49th DPS Session Table of Contents - Microsoft...2017/10/16 · 49th DPS Provo, UT – October, 2017 Meeting Abstracts Session Table of Contents 100 – Dynamics, Origins and Theory:

49th DPSProvo, UT – October, 2017

Meeting AbstractsSession Table of Contents100 – Dynamics, Origins and Theory:NEOs101 – Education and Outreach102 – Pluto System I103 – Asteroids: Observational Surveys104 – Planetary Rings105 – Pluto System II106 – Meteors and Meteorites107 – The Life and Work of Toby Owen108 – Plenary: Cassini Grand Finale109 – Plenary: Juno Science Highlights110 – Asteroids: Physical Characterization111 – Asteroids: Dynamics, Origins andTheory112 – Asteroids: Observational Surveys113 – Meteors and Meteorites114 – Dawn at Ceres115 – Jovian Planets116 – Education and Outreach117 – Asteroids: iPoster118 – Jovian Planets: iPoster119 – Education and Outreach: iPoster200 – Historical Astronomy: Rosetta,Cassini, Transit of Mercury201 – Dynamics, Origins and Theory:Main-Belt Asteroids202 – Astrobiology and ComparativePlanetology203 – Icy Galilean Satellites204 – Asteroid Physical Characteristics:NEOs205 – Giant Planet Atmospheres I207 – Enceladus208 – Asteroid Physical CharacteristicsIncluding Main-belt Asteroids209 – Giant Planet Atmospheres II210 – Other Icy Satellites211 – Jovian Planets: Magnetospheres andAurorae212 – Planetary Rings and SatelliteDynamics213 – Titan214 – Outer Planet Satellites215 – Pluto System216 – Centaurs and Kuiper Belt Objects217 – Astrobiology and ComparativePlanetology218 – Data Archiving and Analysis

219 – Future Missions andInstrumentation220 – Planetary Rings and Satellites:iPoster221 – Pluto, Centaurs, and Kuiper BeltObjects: iPoster222 – Astrobiology and ComparativePlanetology: iPoster223 – Data Archiving and Analysis: iPoster224 – Future Missions andInstrumentation: iPoster300 – Extrasolar Planets and Systems:Terrestrial Planet Atmospheres301 – Titan: Surface and Interior302 – Trojan Asteroids303 – Jovian Planets: Interiors304 – Titan: Atmosphere305 – Comet Physical Characteristics:Comae306 – Dawn at CeresPresentation of Carl Sagan Medal andGerard P. Kuiper Prize308 – Gerard P. Kuiper Prize: Using theTools of the Trade to Understand PlasmaInteractions at Jupiter and Saturn,Margaret Kivelson (UCLA & Univ. ofMichigan)309 – Plenary Talk: The Long-TermEffects of Racial Microaggressions onPeople of Color in STEM, William Smith(University of Utah)310 – Plenary Talk: Aromatic, Alphatic,Enigmatic: The Chemistry of Titan, SarahHörst (Johns Hopkins Univ.)400 – Mars: Surface401 – Comets: Dynamics, Origins andTheory402 – Extrasolar Planets and Systems:Giant Planet Atmospheres I403 – Comet Physical Characteristics:Nuclei and Surfaces404 – Mercury and The Moon405 – Centaurs and Kuiper Belt Objects:Surveys, Dynamics, Theory, and "Planet 9"406 – Phobos and Deimos408 – Extrasolar Planets and Systems:Giant Planet Atmospheres II407 – Io: The Volcanic Wonderland

Presentation of Harold Masursky Award,Jonathan Eberhart Planetary SciencesJournalism Award, and Harold C. UreyPrize410 – Harold C. Urey Prize: Mars’ FirstBillion Years: Key Findings, Key UnsolvedParadoxes, and Future Exploration,Bethany Ehlmann (Caltech)411 – Plenary Talk: Gone with the Wind:Three Years of MAVEN Measurements ofAtmospheric Loss at Mars, David Brain(Univ. of Colorado, Boulder)412 – Plenary Talk: A Septet of Earth-Sized Planets, Amaury Triaud (Univ. ofCambridge)413 – Origins and Planet Formation414 – Comets: Origins, Dynamics, andCharacterization415 – 67P/Churyumov-Gerasimenko416 – Extrasolar Planets417 – Mercury, Venus, and the Moon418 – Mars Surface, Atmosphere, andSatellites419 – Origins and Planet Formation:iPoster420 – Comets: iPoster421 – Extrasolar Planets: iPoster422 – Mercury, Venus, and Mars: iPoster500 – Origins of Planetary Systems I501 – Centaurs and Kuiper Belt Objects:Rings and Collisional Families502 – Unveiling Venus503 – Origins of Planetary Systems II504 – Centaurs and Kuiper Belt Objects:Physical Characterization505 – Terrestrial Planets: Magnetospheres506 – Extrasolar Planets and Systems:Discoveries and Dynamics507 – Mars: Lower Atmospheric Structure,Composition, and Circulation508 – Formation of Planets and Satellites509 – 67P/Churyumov-Gerasimenko510 – Mars: Upper AtmosphericObservations, Modeling, andInterpretations511 – Outer Irregular Satellites

100 – Dynamics, Origins and Theory: NEOs100.01 – The Population of Near-Earth AsteroidsRevisitedI have been tracking progress of the surveys discovering Near-Earth Asteroids (NEAs) for more than 20 years, and havereported updates every few years at past meetings. Following mylast report at a DPS and the published update two years ago(Harris and D’Abramo 2015, Icarus 257, 302-312), it came tolight that these and previous estimates were affected by round-offof H magnitudes by the Minor Planet Center to 0.1 mag. While itis true that individual magnitudes are generally not even thataccurate, statistically the round-off shifted the populationestimate by ~6%. While this hardly matters in the small sizerange, for the largest asteroids the shift alters N(H<17.75),assumed equivalent to N(D>1km), from 990 ± 20 (Harris &D’Abramo 2015) to 934 ± 20. Since the number alreadydiscovered, 872, is the same for both solutions, the impliedcompletion of the surveys shifts from 88% to 93%. Not only is thiscorrection satisfying with regard to the “Spaceguard Goal” ofdiscovering 90% of NEAs of D > 1 km, but it reduces theestimated number of large NEAs remaining to be discovered bynearly a factor of 2. In this presentation I will explain thecorrection to the round-off bias and present an updatedpopulation estimate and survey progress using discoveries up toJuly, 2017.

Author(s): Alan William HarrisInstitution(s): 1. MoreData! Inc

100.02 – Debiased estimates for NEO orbits,absolute magnitudes, and source regionsThe debiased absolute-magnitude and orbit distributions as wellas source regions for near-Earth objects (NEOs) provide afundamental frame of reference for studies on individual NEOs aswell as on more complex population-level questions. We present anew four-dimensional model of the NEO population thatdescribes debiased steady-state distributions of semimajor axis(a), eccentricity (e), inclination (i), and absolute magnitude (H).We calibrate the model using NEO detections by the 703 and G96stations of the Catalina Sky Survey (CSS) during 2005-2012corresponding to objects with 17<H<25. The modeling approachimproves upon the methodology originally developed by Bottke etal. (2000, Science 288, 2190) in that we allow the power-lawslope of the H-frequency distribution to change as a function of Hand we carry out the fitting in an absolute sense using the biasescomputed for CSS (Jedicke et al. 2016, Icarus 266, 173). Themodel makes use of six source regions or escape routes from themain asteroid belt as identified by Granvik et al. (2017, A&A 598,A52) in addition to Jupiter-family comets: Hungaria and Phocaeaasteroids, and main-belt asteroids escaping through the ν , 3:1J,5:2J and 2:1J resonance complexes. We account for thedestruction of asteroids with small perihelion distances (Granviket al. 2016, Nature 530, 303) by fitting a penalty function inperihelion distance. Our model accurately reproduces theobserved distribution of NEOs and the predicted numbers,particularly for the larger NEOs, are in agreement with othercontemporary estimates. Our model also provides updatedestimates for the likelihood of the various source regions andescape routes as a function of NEO (a,e,i,H) parameters. Wepresent the model and its predictions, and discuss them in thecontext of other contemporary estimates.

Author(s): Mikael Granvik , Alessandro Morbidelli , RobertJedicke , Bryce T. Bolin , William Bottke , Edward C. Beshore ,David Vokrouhlicky , David Nesvorny , Patrick MichelInstitution(s): 1. Charles University, 2. Observatoire de la Coted'Azur, 3. Southwest Research Institute, 4. University of Arizona,5. University of Hawaii, 6. University of Helsinki

100.03 – What Really Happened to Earth's OlderCraters?Most assume the Earth’s crater record is heavily biased, witherosion/tectonics destroying older craters. This matches

expectations, but is it actually true? To test this idea, wecompared Earth’s crater record, where nearly all D ≥ 20 kmcraters are < 650 Myr old, to the Moon’s. Here lunar crater ageswere computed using a new method employing LRO-Divinertemperature data. Large lunar rocks have high thermal inertiaand remain warm through the night relative to the regolith.Analysis shows young craters with numerous meter-sizedfragments are easy to pick out from older craters with erodedfragments. Moreover, an inverse relationship between rockabundance (RA) and crater age exists. Using measured RA values,we computed ages for 111 rocky craters with D ≥ 10 km thatformed between 80°N and 80°S over the last 1 Gyr. We found several surprising results. First, the production rate ofD ≥ 10 km lunar craters increased by a factor of 2.2 [-0.9, +4.4;95% confidence limits] over the past 250 Myr compared to theprevious 750 Myr. Thus, the NEO population is higher now thanit has been for the last billion years. Second, the size and agedistributions of lunar and terrestrial craters for D ≥ 20 km overthe last 650 Myr have similar shapes. This implies that cratererasure must be limited on stable terrestrial terrains; in anaverage sense, for a given region, the Earth either keeps all orloses all of its D ≥ 20 craters at the same rate, independent of size.It also implies the observed deficit of large terrestrial cratersbetween 250-650 Myr is not preservation bias but rather reflectsa distinctly lower impact flux. We predict 355 ± 86 D ≥ 20 kmcraters formed on Earth over the last 650 Myr. Only 38 ± 6 areknown, so the ratio, 10.7 ± 3.1%, is a measure of the Earth’ssurface that is reasonably stable to large crater formation over650 Myr. If erosion had dominated, the age distribution ofterrestrial craters would be strongly skewed toward younger ages,which is not observed. We predict Chicxulub-type impacts wererare over the last Gyr, with the event 66 Ma a probable byproductof the current high terrestrial impact flux.

Author(s): William Bottke , Sara Mazrouei , RebeccaGhent , Alex ParkerInstitution(s): 1. Southwest Research Inst., 2. University ofToronto

100.04 – Difficult to discover Near-Earth ObjectsThere has been good progress in discovering large Near-EarthObjects (NEOs). Impact by an object of 1 km diameter or largerwould be globally catastrophic. It is presently believed that thereare approximately 900 NEOs with diameter greater than 1 km,and that over 90% of them have been discovered. The remainingobjects are difficult to discover, and are currently being found at arate of about 6 per year. The Pan-STARRS1 telescope in Hawaiihas been leading the discovery of the remaining large objects. The Pan-STARRS1 telescope has also discovered a large numberof NEOs that have periods close to 3 years. These NEOs haveescaped discovery by less sensitive telescopes, and their orbitalproperties will be examined. The orbital properties of the recentlydiscovered large NEOs will be discussed, and the reasons whythey evaded discovery will be examined. The future prospects forfinding the remaining large NEOs will be discussed. Possiblechanges to the search strategy by Pan-STARRS to facilitatediscovery of the remaining undiscovered large NEOs will beevaluated.

Author(s): Richard J. Wainscoat , Kenneth C. Chambers ,Eva Lilly , Marco Micheli , Robert J. WerykInstitution(s): 1. ESA SSA-NEO Coordination Centre, 2. Univ.of Hawaii

100.05 – Resurfacing Asteroids From ThermallyInduced Surface DegradationThe spectral slopes of S and Q-type Near-Earth Asteroids (NEAs)trend toward lower values with decreasing perihelion.Additionally, Q-type asteroids show a higher correlation of havingrecent close encounters with terrestrial planets compared to S-types. These two results have led to the explanation that close

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encounters with the terrestrial planets are an effective resurfacingmechanism for changing S-type asteroids into Q-types and forlowering their spectral slopes. However, previous modelingattempts had difficulty in reproducing the exact orbitaldistribution of all Q-type asteroids from close encounters,suggesting that other potential resurfacing mechanisms mayexplain observations more fully. We consider thermally inducedsurface degradation as a possible mechanism to create freshsurfaces on asteroids with low (≤ 1 AU) perihelia. Stressesinduced by diurnal thermal cycling in asteroid materials scalestrongly with solar distance, making this an attractive potentialmechanism. Using an N-body model, we simulate the evolution ofS and Q-type NEAs. In the model, we incrementally weather theasteroid surfaces from the solar wind and refresh their surfacesfrom a simplified thermal degredation model. We show that theprocess of thermally induced surface degradation can naturallycreate the spectral slope vs. perihelion trend seen in the data forreasonable scaling factors of surface degradation with solardistance. We also recreate a close encounter resurfacing model togenerate the spectral slope vs. perihelion distribution from closeencounters and compare the results from both models.

Author(s): Kevin Graves , David A. Minton , Jamie Molaro ,Masatoshi HirabayashiInstitution(s): 1. JPL, 2. Purdue University

100.06 – The Characterization of Non-Gravitational Perturbations That Act on Near-Earth Asteroid OrbitsThe Yarkovsky effect is a thermal process acting upon the orbitsof small celestial bodies which can cause these orbits to slowlyexpand or contract with time. The effect is subtle -- typical driftrates lie near 1e-4 au/My for a ~1 km diameter object -- and isthus generally difficult to measure. However, objects with longobservation intervals, as well as objects with radar detections,serve as excellent candidates for the observation of this effect.

We analyzed both optical and radar astrometry for all numberedNear-Earth Asteroids (NEAs), as well as several un-numberedNEAs. In order to quantify the likelihood of Yarkovsky detections,we developed a metric based on the quality of Yarkovsky fits ascompared to that of gravity-only fits. Based on the metric results,we report 167 objects with measured Yarkovsky drifts.

Our Yarkovsky sample is the largest published set of suchdetections, and presents an opportunity to examine the physicalproperties of these NEAs and the Yarkovsky effect in a statisticalmanner. In particular, we confirm the Yarkovsky effect'stheoretical size dependence of 1/D, where D is diameter. We alsoexamine the efficiency with which this effect converts absorbedlight into orbital drift. Using our set of 167 objects, we find typicalefficiences of around 5%. This efficiency can be used to placebounds on spin and thermal properties. We report the ratio ofpositive to negative drift rates and interpret this ratio in terms ofprograde/retrograde rotators and main belt escape mechanisms.The observed ratio has a probability of 1 in 9 million of occurringby chance, which confirms the presence of a non-gravitationalinfluence. We examine how the presence of radar data affect thestrength and precision of our detections. We find that, on average,the precision of radar+optical detections improves by a factor ofapproximately 1.6 for each additional apparition with rangingdata compared to that of optical-only solutions.

Author(s): Jean-Luc Margot , Adam H Greenberg , AshokK. Verma , Patrick A. TaylorInstitution(s): 1. Arecibo Observatory, 2. University ofCalifornia, Los Angeles

100.07 – New results on spin evolution due to theYORP effectWe revisit the theory of how asteroids change their rotation ratesand obliquities due to the YORP effect. We study the general casewith spin rate and obliquity coupled through basic analyticmodels. Under a set of reasonable assumptions we analytically

derive the basic Type I and II YORP coefficients, and also show afundamental correlation between the spin rate and spin obliquityevolutions. This result indicates that, out of a range of possiblespin evolutions, there are mainly two that need to be considered.Our analytical theory is tested against available photometric,radar and in situ shape models of asteroids, obtaining the YORPcoefficients for comparison with the analytic models, as well asfor numeric simulations of spin evolution of asteroids. Ourmodels also incorporate the effects of finite thermal conductivityfor the evolution of the obliquity, and the thermal transferthrough surface boulders for the evolution of the spin rate (the so-called Tangential YORP effect). Under these effects we show thatthere exist possibly stable equilibria for the combined asteroidspin and obliquity evolution. The existence of such equilibria hasimportant implications for the evolution of small body spin statesand for the asteroid population in general.

Author(s): Oleksiy Golubov , Daniel J. ScheeresInstitution(s): 1. CU BoluderContributing team(s): Oleksiy Golubov

100.08 – A contact binary asteroid evolutionarycycle driven by BYORP & the classical LaplaceplaneSeveral contact binaries have been observed to have highobliquities distributed around 90°. With this information, weexplore the possibility of these high obliquities being a keycharacteristic that causes an evolutionary cycle of contact binaryformation and separation. The contact binary cycle begins with a single asteroid that isspinning up due to the YORP effect. For the binary cycle weassume YORP will drive the obliquity to 90°. Eventually, theasteroid will reach a critical spin frequency that will cause theasteroid to fission into a binary. We assume that the mass-ratio,q, of the system is greater than 0.2. With a high q, the secondarywill not escape/impact the primary but will evolve through tidesinto a stable circular double-synchronous orbit. The binary beingsynchronous will cause the forces from BYORP to have seculareffects on the system. For this cycle, BYORP will need to expandthe secondary away from the primary. As the system expands, we have found that the secondary willfollow the classical Laplace plane. Therefore, the secondary’s orbitwill increase in inclination with respect to the equator as thesecondary’s orbit expands. The Laplace plane is a stable orbit toperturbations from J & Sun tides except for an instability regionthat exists for primaries with obliquities above 68.875° & asecondary orbital radius of 13.5-19.5 primary radii. Once BYORPexpands the secondary into this instability region, the eccentricityof the secondary’s orbit will increase until the orbit intersects withthe primary & causes an impact. This impact will create a contactbinary with a new obliquity that will randomly range from23°-150°. The cycle will begin again with YORP driving thecontact binary to an obliquity of 90°. Our contribution will discuss the proposed contact binary cycle inmore detail, including the mechanics of the system that drives theevents given above. We will include investigations into how losingsynchronous lock will disrupt the eccentricity growth in theLaplace plane instability region. We will also discuss the timescales of each event to help predict which part of the cycle we willmost likely to be observing when discovering new contact binaries& binary systems.

Author(s): Samantha Rieger , Daniel J. ScheeresInstitution(s): 1. University of Colorado Boulder

100.09 – Mass estimate and close approaches ofnear-Earth asteroid 2015 TC25Near-Earth asteroid 2015 TC25 was discovered by the CatalinaSky Survey in October 2015, just two days before an Earth flyby at0.3 lunar distances. By using ground-based optical, near-infrared,and radar assets during the flyby, Reddy et al. (2016) successfully

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101 – Education and Outreach

characterized 2015 TC25. They suggested that the object has ahigh albedo and a diameter of 2 m, which makes 2015 TC25 oneof the smallest asteroids ever detected. Moreover, the orbitalinformation available at the end of the 2015 apparition indicatedthat 2015 TC25 had a probability of an Earth impact of more than1 in 10000 from 2070 to 2115. To rule out possible impacts werecovered 2015 TC25 at the end of March 2017 and continuedtracking the object through the end of April, when it became toofaint to be observable. The recent 2017 astrometry clearly showsthe action of solar radiation pressure on the orbit of 2015 TC25with a 7.6-sigma detection. This solar radiation pressure estimateallows us to put constraints on the density and mass of 2015 TC25and further suggests that the object is only a couple of meters insize. In particular, the area-to-mass ratio is between 0.6 m^2/tand 0.7 m^2/t and, for a diameter of 2 m, the density is about 1.1

g/cm^3. By accounting for the contribution of non-gravitationalperturbations, we analyze the future trajectory of 2015 TC25.Based on the extended data arc, ephemeris predictions are nowdeterministic until the Earth close approach in 2089 and a MonteCarlo search rules out impacts for the next 100 years.

Author(s): Davide Farnocchia , David J. Tholen , MarcoMicheli , William Ryan , Edgard G. Rivera-Valentin , Patrick A.Taylor , Jon D. GiorginiInstitution(s): 1. Arecibo Observatory, 2. ESA SSA-NEOCoordination Center, 3. Jet Propulsion Laboratory, 4.Magdalena Ridge Observatory, 5. University of Hawaii

101.01 – Teaching Planetary Science as Part of theSearch for Extraterrestrial Intelligence (SETI)In Spring 2016 and 2017, UCLA offered a course titled "EPSSC179/279 - Search for Extraterrestrial Intelligence: Theory andApplications". The course is designed for advancedundergraduate students and graduate students in the science,technical, engineering, and mathematical fields. Each year,students designed an observing sequence for the Green Banktelescope, observed known planetary systems remotely, wrote asophisticated and modular data processing pipeline, analyzed thedata, and presented their results. In 2016, 15 studentsparticipated in the course (9U, 5G; 11M, 3F) and observed 14planetary systems in the Kepler field. In 2017, 17 studentsparticipated (15U, 2G; 10M, 7F) and observed 10 planetarysystems in the Kepler field, TRAPPIST-1, and LHS 1140. In orderto select suitable targets, students learned about planetarysystems, planetary habitability, and planetary dynamics. Inaddition to planetary science fundamentals, students learnedradio astronomy fundamentals, collaborative softwaredevelopment, signal processing techniques, and statistics.Evaluations indicate that the course is challenging but thatstudents are eager to learn because of the engrossing nature ofSETI. Students particularly value the teamwork approach, theobserving experience, and working with their own data. The nextoffering of the course will be in Spring 2018. Additionalinformation about our SETI work is available at seti.ucla.edu.

Author(s): Jean-Luc Margot , Adam H GreenbergInstitution(s): 1. University of California, Los Angeles

101.02 – The 2017 Total Solar Eclipse: Through theEyes of NASAThe August 21st, 2017 Total Solar Eclipse Across Americaprovided a unique opportunity to teach event-based science tonationwide audiences. NASA spent over three years planningspace and Earth science education programs for informalaudiences, undergraduate institutions, and life long learners tobring this celestial event to the public through the eyes of NASA.This talk outlines how NASA used its unique assets includingmission scientists and engineers, space based assets, citizenscience, educational technology, science visualization, and itswealth of science and technology partners to bring the eclipse tothe country through multimedia, cross-discipline scienceactivities, curricula, and media programing. Audience reach,impact, and lessons learned are detailed. Plans for similar eventsin 2018 and beyond are outlined.

Author(s): Louis MayoInstitution(s): 1. NASA Goddard Space Flight CenterContributing team(s): NASA Goddard Heliophysics EducationConsortium

101.03 – Solar-system Education for the 2017 TotalSolar Eclipse I describe an extensive outreach program about the Sun, thesilhouette of the Moon, and the circumstances both celestial andterrestrial of the August 21, 2017, total solar eclipse. Publications

included a summary of the last decade of solar-eclipse researchfor Nature Astronomy, a Resource Letter on Observing SolarEclipses for the American Journal of Physics, and book reviewsfor Nature and for Phi Beta Kappa's Key Reporter. Symposiaarranged include sessions at AAS, APS, AGU, and AAAS. Lecturesinclude all ages from pre-school through elementary school tohigh school to senior-citizen residences. The work, including the scientific research about the solar coronathat is not part of this abstract, was supported by grants from theSolar Terrestrial Program of the Atmospheric and GeospaceSciences Division of NSF and from the Committee for Researchand Exploration of the National Geographic Society. Additionalstudent support was received from NSF, NASA's MassachusettsSpace Grant Consortium, the Honorary Research Society SigmaXi, the Clare Booth Luce Foundation, and funds at WilliamsCollege.

Author(s): Jay M. PasachoffInstitution(s): 1. Williams College

101.04 – Leveraging Emerging Technologies inOutreach for JWSTThe James Webb Space Telescope (JWST) is NASA’s next greatobservatory, launching in October 2018. How will we maintainthe prestige and cultural impact of the Hubble Space Telescope asthe torch passes to Webb? Emerging technologies such asaugmented (AR) and virtual reality (VR) bring the viewer into thedata and introduce the telescope in previously unimaginableimmersive detail. Adoption of mobile devices, many of whicheasily support AR and VR, has expanded access to information forwide swaths of the public. From software like WorldwideTelescope to hardware like the HTC Vive, immersiveenvironments are providing new avenues for learning. If wedevelop materials properly tailored to these media, we can reachmore diverse audiences than ever before. STScI is piloting toolsrelated to JWST to showcase at DPS, and in local events, which Ihighlight here.

Author(s): Bonnie K. Meinke , Joel D. Green , Louis ChadSmith , Denise A. Smith , Brandon L. Lawton , Michael GoughInstitution(s): 1. STScI

101.05 – NASA’s Universe of Learning: GirlsSTEAM AheadNASA Science Mission Directorate’s Universe of Learning (UoL)program enables scientists and engineers to more effectivelyengage with learners of all ages. The Girls STEAM Ahead withNASA education program within UoL, expands upon the formerprogram, NASA Science4Girls and Their Families, in celebrationof National Women’s History Month. The initiative partners theNASA’s Universe of Learning science education programresources with public libraries to provide NASA-themed activitiesfor girls and their families, including hands-on activities forengaging girls, complementary exhibits, and professionaldevelopment for library partner staff. The science-institute-embedded partners in NASA’s UoL are uniquely poised to fostercollaboration between scientists with content expertise andeducators with pedagogy expertise. The thematic topics related to

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NASA Astrophysics enable audiences to experience the full rangeof NASA scientific and technical disciplines and the differentcareer skills each requires. The events focus on engagingunderserved and underrepresented audiences in Science,Technology, Engineering, and Mathematics (STEM) via use ofresearch-based best practices, collaborations with libraries,partnerships with local and national organizations (e.g. NationalGirls Collaborative Project or NGCP), and remote engagement ofaudiences. This presentation will provide an overview of theprogram progress related to engaging girls and their families inNASA-based science programming.

Author(s): Emma Marcucci , Bonnie K. Meinke , Denise A.Smith , Holly Ryer , Carolyn Slivinski , Jessica Kenney ,Kimberly K. Arcand , Lynn R. CominskyInstitution(s): 1. Smithsonian Astrophysical Observatory, 2.Sonoma State University, 3. Space Telescope Science InstituteContributing team(s): Girls STEAM Ahead with NASA team

101.06 – Trick or Treat and TelescopesBased on an activity that DPS member Richard Schmude Jr. hasbeen doing for years, with over 5000 children reached, DPSinitiated in 2016 a pilot program entitled “Trick-or-Treat andTelescopes.” DPS encouraged its members to put out theirtelescopes during trick-or-treat time on Halloween, in their ownlawns or in a neighbor’s lawn with better viewing (or moretraffic). The program will be continued in 2017. This year shouldoffer good viewing with a waxing gibbous moon and Saturnvisible. The program was also advertised though the Night SkyNetwork, a consortium of astronomy clubs. The following websitegives advice and connections to resources.

https://dps.aas.org/education/trick-or-treat-and-telescopes

© 2017 California Institute of Technology. Governmentsponsorship acknowledged.

Author(s): Bonnie J. Buratti , Bonnie K. Meinke , RichardW. SchmudeInstitution(s): 1. Gordon State College, 2. JPL, 3. SpaceTelescope Science Institute

101.07 – The PACA Project Observing Campaigns:From Comets to the SunThe Pro-Am Collaborative Astronomy (PACA) project evolvedfrom the observational campaign of C/2012 S1 or C/ISON in2013, and has expanded to pro-am observing campaigns ofplanets, polarimetric exploration and recently, polarization of theinner solar corona during the 2017 US Continental Total SolarEclipse (TSE). The evolving need for individual customizedobserving campaigns has been incorporated into the evolution ofPACA portal: supporting observing campaigns of current comets,legacy data, historical comets, planets, solar corona,interconnected with social media and a set of shareabledocuments addressing observational strategies; consistentstandards for data; data access, use, and storage, to align with theneeds of professional observers. Given the volume of datagenerated for each campaign, new ways of rapid data analysis,mining access and storage are needed. Several interesting resultsemerged from the synergistic inclusion of both social media andamateur astronomers: (1) the establishment of a network ofastronomers and related professionals, that can be galvanizedinto action on short notice to support observing campaigns; (2)assist in various science investigations pertinent to the campaign;(3) provide an alert-sounding mechanism should the need arise;(4) immediate outreach and dissemination of results via ourmedia/blogger members; (5) provide a forum for discussionsbetween the imagers and modelers to help strategize theobserving campaign for maximum benefit. Some recent PACAcampaigns of note are: C/2013 A1 (C/SidingSpring) ;67P/Churyumov-Gerasimenko (CG), target for ESA/Rosettamission; PACA_Jupiter (and for other planets Mars, Saturn,Uranus and Neptune); polarimetry and current campaign

PACA_PolNet, a multi-site polarimetric network to beimplemented in August 2017, in partnership with the projectCitizen CATE. I will highlight key aspects of various PACAcampaigns, especially the current PACA_PolNet for the 2017Total Solar Eclipse and the proposed collaboration for the nextTotal Solar Eclipse of 2024. The integration of science,observations by professional and amateur astronomers, andvarious social media provides a dynamic and evolving collectivecollaborative partnership.

Author(s): Padma A. Yanamandra-FisherInstitution(s): 1. Space Science InstituteContributing team(s): The PACA Project

101.08 – An Analog Rover Exploration Mission forEducation and OutreachThis abstract describes an analog rover exploration missiondesigned as an outreach program for high school andundergraduate students. This program is used to teach themabout basic mission control operations, how to manage a rover asif it were on another planetary body, and employing the roverremotely to complete mission objectives. One iteration of thisprogram has been completed and another is underway. In bothtrials, participants were shown the different operation processesinvolved in a real-life mission. Modifications were made to theseprocesses to decrease complexity and better simulate a missioncontrol environment in a short time period (three 20-minute-longmission “days”). In the first run of the program, participants selected a landingsite, what instruments would be on the rover - subject to cost,size, and weight limitations - and were randomly assigned one ofsix different mission operations roles, each with specificresponsibilities. For example, a Science Planner/Integrator (SPI)would plan science activities whilst a Rover Engineer (RE) wouldkeep on top of rover constraints. Planning consisted of a series offour meetings to develop and verify the current plan, pre-plan thenext day's activities and uplink the activities to the “rover” (ahuman colleague). Participants were required to attend certainmeetings depending upon their assigned role. To conclude themission, students viewed the site to understand any differencesbetween remote viewing and reality in relation to the rover. Another mission is currently in progress with revisions from theearlier run to improve the experience. This includes broader rolesand meetings and pre-selecting the landing site and rover. Thenew roles are: Mission Lead, Rover Engineer and SciencePlanner. The SPI role was previously popular so most of thestudents were placed in this category. The meetings were reducedto three but extended in length. We are also planning to integrate this program into the OntarioScience Center (OSC) to educate and fascinate people of all ages.

Author(s): John Moores , Charissa L. Campbell , Christina L.Smith , Brittney A. CooperInstitution(s): 1. York University

101.09 – Big Data & Datamining: Using APIs tocomputationally determine who follows spacescience, & what do they care about?In today's connected world, scientists & space science projects areturning to social media outlets like Twitter to share ourachievements, request aid, & discuss the issues of our profession.Maintaining these disparate feeds requires time & resources thatare already in short supply. To justify these efforts, we mustexamine the data to determine: are we speaking to our intendedaudiences; are our varied efforts needed; & what types ofmessages achieve the greatest interactions. The software used tosupport this project is available on GitHub. Previously, it has been unclear if our day-to-day social mediaefforts have been merely preaching to one homogeneous choirfrom which we have all drawn our audiences, or if our individual

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efforts have been able to reach into different communities tomultiply our impact. In this preliminary study, we examine thesocial media audiences of several space science Twitter feeds thatrelate to: podcasting; professional societies; individual programs;& individuals. This study directly measures the overlap inaudiences & the diversity of interests held by these audiences.Through statistical analysis, we can discern if these audiences areall drawn from one single population, or if we are samplingdifferent base populations with different feeds.

The data generated in this project allow us to look beyond howour audiences interact with space science, with the added benefitof revealing their other interests. These interests are reflected bythe non-space science accounts they follow on Twitter. Thisinformation will allow us to effectively recruit new people fromspace science adjacent interests.

After applying large data analytics & statistics to social media

interactions, we can model online communications, audiencepopulation types, & the causal relationships between how wetweet &how our audiences interact. With this knowledge, we arethen able to institute reliable communications & effectiveinteractions with our target audience. This work is supported through NASA cooperative agreementNNX17AD20A.

Author(s): Pamela L. Gay , Maya Bakerman , NancyGraziano , Susan Murph , Alison ReiheldInstitution(s): 1. Astronomical Society of the Pacific, 2.Planetary Science Institution, 3. Southern Illinois UniversityEdwardsvilleContributing team(s): CosmoQuest

102.01 – A Search for Temporal Changes on Plutoand CharonA search for temporal changes on Pluto and Charon wasmotivated by (1) the discovery of young surfaces in the Plutosystem that imply ongoing or recent geologic activity, (2) thedetection of active plumes on Triton during the Voyager 2 flyby,and (3) the abundant and detailed information that observinggeologic processes in action provides about the processes. Athorough search for temporal changes using New Horizonsimages was completed. Images that covered the same region wereblinked and manually inspected for any differences inappearance. The search included full-disk images such that allilluminated regions of both bodies were investigated and alsohigher resolution images such that parts of the encounterhemispheres were investigated at finer spatial scales. Changes ofappearance between different images were observed but in allcases were attributed to variability of the imaging parameters(especially geometry) or artifacts. No differences of appearancethat are strongly indicative of a temporal change were found onthe surface or in the atmosphere of either Pluto or Charon. Limitson temporal changes as a function of spatial scale and temporalinterval during the New Horizons encounter are determined. Thelongest time interval constraint is one Pluto/Charon rotationperiod (~6.4 Earth days). Contrast reversal and high-phase brightfeatures that change in appearance with solar phase angle areidentified. The change of appearance of these features is mostlikely due to the change in phase angle rather than a temporalchange. Had active plumes analogous to the plumes discoveredon Triton been present on the encounter hemispheres of eitherPluto or Charon, they would have been detected. Several darkstreak features that may be deposits from past plumes areidentified. The absence of active plumes may be due to temporalvariability or because the process that generates Triton’s plumesdoes not occur on Pluto.

Author(s): Jason D Hofgartner , Bonnie J. Buratti , SpencerDevins , Ross A. Beyer , Paul M. Schenk , S. Alan Stern , HaroldA Weaver , Catherine Olkin , Andrew F. Cheng , KimberlyEnnico , Tod R. Lauer , John R. Spencer , Leslie YoungInstitution(s): 1. Jet Propulsion Laboratory, 2. Johns HopkinsUniversity Applied Physics Laboratory, 3. Lunar and PlanetaryInstitute, 4. NASA Ames Research Center, 5. National OpticalAstronomy Observatory, 6. Southwest Research InstituteContributing team(s): New Horizons Science Team

102.02 – Emission from Pluto and Charon at LongWavelengths: Observations using ALMA, SMA, andVLAWe report on the first Earth-based observations of thermalemission from the surfaces of Pluto and Charon where the two areresolved from each other. Observations at wavelengths from 0.8mm to 0.9 cm with the Atacama Large Millimeter/submillimeterArray (ALMA), Submillimeter Array (SMA), and Karl G. JanskyVery Large Array (VLA) provide separate, high SNR flux densities

for both bodies, which are converted into brightnesstemperatures. These observations have been presented separatelypreviously [1-3] but here we combine them for the first time andextend the analysis. For Pluto, brightness temperatures rangefrom 31--33 K, and for Charon from 42--45 K, over the full rangeof observed wavelengths. These brightness temperatures aresignificantly lower than observed surface temperatures for bothbodies. While hinted at from unresolved observations of the pair,this is the first definitive observation showing both bodies havedepressed brightness temperatures. These low brightnesstemperatures are likely due to a combination of low thermalinertia, and subsurface scattering, with a larger depression forPluto than for Charon. [1] Butler et al. 2015, BAAS #47, id.210.04. [2] Gurwell et al. 2011,DPS/EPSC, p271. [3] Butler et al. 2011, DPS/EPSC, p. 1670.

Author(s): Bryan J. Butler , Mark A. Gurwell , EmmanuelLellouch , Arielle Moullet , Nicolas Biver , Dominique Bockelee-Morvan , Jeremie boissier , Thierry Fouchet , Dariusz C. Lis ,Raphael Moreno , John Stansberry , S. Alan Stern , Eliot F.Young , Leslie Young , Harold A WeaverInstitution(s): 1. Caltech, 2. Harvard-Smithsonian Center ForAstrophysics, 3. IRAM, 4. JHU APL, 5. NRAO, 6. Observatoire deParis, 7. STScI, 8. SWRI

102.03 – Washboard Terrain on PlutoWashboard texture or patterning consists of fields of parallel tosub-parallel ridges typically spaced ~1-2 km crest to crest and afew 100 m in amplitude (Fig. 4a in Moore et al., 2016, Science,351, 1284-1293). For the most part, underlying topography can beeasily discerned. We will refer to discrete, well-bounded patchesof these landforms as Washboard Terrain (WT). WT is observedto occur along the rim, and just beyond the rim, of Sputnik basinfrom the West to NNW. Where it is seen in high-resolution data,it has clearly defined limits, beyond which it would be able to beseen if it were there. WT doesn’t occur at very low latitudes orvery high latitudes (ranging from 22°N to 62°N). WT seems tooccur most conspicuously on relatively level, gently slopingterrain. It is restricted to elevations between ~-2 km to <+1.5 km(i.e. not at high elevations). The most noticeable regional aspectof the area in which WT occurs is the sinuous valley network,which is suspected to have been formed, or at least substantiallymodified, by glaciation. WT also appears to occur mainly on anintermediate-albedo reddish material, where seen in enhancedcolor data. Where it occurs in level terrain, WT tends to trendENE – there doesn’t seem to be a strong local control of itsorientation in response to valley drainage directions. WT candisplay a greater range of orientations where it occurs in higher-relief (not higher elevation) settings such as spurs. WT appearssuperposed on very ancient landscapes, but is itself crateredlocally by clusters of small (~1-3 km) craters, which may besecondaries. This implies that WT may be intermediate in age. Ofseveral working hypotheses, we currently provisionally favor thatWT may be akin to terrestrial recessional moraines (or de Geermoraines) associated with the retreat of a higher stand of N

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glaciation that once overfilled Sputnik basin. These putativemoraine features may owe their spacing to superseasonal retreaton Milankovitch timescales of ~1 Ma. If this hypothesis hasvalidity, then perhaps the intermediate-albedo reddish materialmay be akin to ground moraine deposits.

Author(s): Jeffrey M. Moore , Oliver L. White , Alan D.Howard , Orkan M. Umurhan , Paul M. Schenk , Ross A.Beyer , William B. McKinnnon , Kelsi N. Singer , Tod R. Lauer ,Andrew F. Cheng , Leslie Young , S. Alan Stern , Harold AWeaver , Catherine Olkin , Kimberly EnnicoInstitution(s): 1. Johns Hopkins University Applied PhysicsLaboratory, 2. Lunar and Planetary Institute, 3. NASA AmesResearch Center, 4. National Optical Astronomy Observatory, 5.Southwest Research Institute, 6. University of Virginia, 7.Washington UniversityContributing team(s): The New Horizons Science Team

102.04 – Sputnik Planitia, Pluto Convection CellSurface Velocities of ~10 Centimeters per YearBased on Sublimation Pit DistributionSputnik Planitia, Pluto contains cellular landforms with areas onthe order of a few 10 -10 km that are likely the surfacemanifestation of convective overturn in a vast basin of nitrogenice. The cells have sublimation pits on them, with smaller pitsnear their centers and larger pits near their edges. We map over12,000 pits on seven cells and find that the pit radii increase bybetween 2.1 ± 0.4 and 5.9 ± 0.8 × 10 m per meter away fromthe cell center, depending on the cell. Due to finite dataresolution, this is a lower bound on the size increase.Conservatively accounting for resolution effects yields upperbounds on the size vs. distance distribution of 4.2 ± 0.2 to 23.4 ±1.5 × 10 m m . In order to convert the pit size vs. distancedistribution into a pit age vs. distance distribution, we use ananalytic model to calculate that pit radii grow via sublimation at arate of 3.6 [+2.1,-0.6] × 10 m yr . Combined with the mappeddistribution of pit radii, this yields surface velocities between 1.5[+1.0,-0.2] and 6.2 [+3.4,-1.4] cm yr for the slowest cell andsurface velocities between 8.1 [+5.5,-1.0] and 17.9 [+8.9,-5.1] cmyr for the fastest cell; the lower bound estimate for each cellaccounts for resolution effects, while the upper bound estimatedoes not. These convection rates imply that the surface ages at theedge of cells reach approximately 4.2 to 8.9 × 10 yr, dependingon the cell. The rates we find are comparable to rates of ~6 cm yr that were previously obtained from modeling of the convective

overturn in Sputnik Planitia [McKinnon, W.B. et al., 2016,Nature, 534(7605), 82–85]. Finally, we find that the minimumviscosity at the surface of the convection cells is of order 10 to10 Pa s; we find that pits would relax away before sublimatingto their observed radii of several hundred meters if the viscositywere lower than this value.

Author(s): Peter Benjamin Buhler , Andrew P. IngersollInstitution(s): 1. California Institute of Technology

102.05 – Dunes as New Evidence of Recently ActiveSurface Processes on PlutoThe surface of Pluto contains hundreds of aligned, regularlyspaced features best described as transverse dunes (Telfer et al. inreview). They are spaced by 500-700 meters, are several tens ofkilometers long, and are subparallel and with a slightlyundulatory planform, as seen by the New Horizons LORRIinstrument. Their crests are orthogonal to wind streaks seennearby, and therefore to the assumed regional winds. They sitatop the nitrogen-rich informally named Sputnik Planitiacontinental glacier at the base of the informally named Al-IdrisiMontes and appear from New Horizons MVIC data to have acomposition enriched in methane. Their presence requires thereto be particles that can be saltated as well as wind. The particles,or “sands”, are likely composed of relatively hard methane ice,possibly derived from the methane snow seen to blanket themountain summits. While Pluto’s nitrogen-rich atmospherefluctuates in density, perhaps dramatically, current modelledconditions allow for winds that are required to saltate the ice

sands (<~10 m/s). These features are relatively fresh inappearance, especially in comparison with features farther souththat have severe sublimation erosion textures and deformationfrom glacier flow. Furthermore, they lie atop convection cellmargins of Sputnik Planitia, which overturns at rates of ~500 ka.This indicates the dune-like landforms of Pluto are relativelyyoung. This has implications for the surface activity of other largeKuiper Belt Objects and the interaction between limited solarheating and the exotic properties of their surfaces andatmospheres.

Author(s): Jani Radebaugh , Matthew Telfer , Eric Parteli ,Ross A. Beyer , Tanguy Bertrand , Francois Forget , FrancisNimmo , William M. Grundy , Jeffrey M. Moore , S. Alan SternInstitution(s): 1. Brigham Young University, 2. LowellObservatory, 3. NASA Ames Research Center, 4. PlymouthUniversity, 5. Southwest Research Institute, 6. Université Pierreet Marie Curie, 7. University of California, 8. University ofCologneContributing team(s): the New Horizons Team

102.06 – Pluto: Fluidized transport of tholins byheating of the subsurfaceNew Horizons images of Pluto show evidence of the transport ofthe colored non-ice component across the surface, withsubstantial accumulations in some areas of low elevation. Thenon-ice component is presumed to be tholin produced in theatmosphere as a precipitating aerosol, in the surface ices byphotolysis or radiolysis, or both. We model the surface layer of Nice with varying amounts of incorporated tholin particles toexplore the heating within the ice that occurs by the solid-stategreenhouse effect. We find that in plausible models of thecontaminated N surface ice the triple point temperature(63.15K) is reached at a depth of ~< 1m. At that depth theconfining pressure of the ice column is much less than the triplepoint pressure (12.52 kPa), so N should convert to the gas phase,exerting pressure on the overburden. When the gas pressureexceeds the strength of the confining ice, a breakout on thesurface will occur, fluidizing fragments of ice and itscontaminants that are then free to flow downhill, rafted onentrained gas, similar in some ways to the pyroclastic volcanicphenomenon known as nuée ardente. The digital elevation mapof Pluto made from stereo images shows some surface regionsthat may have been stripped of the N layer, exposing H O ice(presumed to be bedrock) below, with a correspondingaccumulation of dark material that was that was the previouslyentrained particulate tholin. Accumulations of tholin are foundassociated with some of the fossae, and some cover preexistingtopography to depths of up to a few hundred meters. Supportedby the New Horizons project.

Author(s): Dale P. Cruikshank , Steven Spohrer , WilliamM. Grundy , Jeffrey M. Moore , Orkan M. Umurhan , Oliver L.White , Ross A. Beyer , Cristina M. Dalle Ore , S. Alan Stern ,Leslie Young , Harold A Weaver , Catherine Olkin , KimberlyEnnicoInstitution(s): 1. JHUAPL, 2. Lowell Observatory, 3. NASAAmes Research Center, 4. SWRIContributing team(s): New Horizons COMP, GGI Teams

102.07 – Pluto’s non-icy component: a close-inanalysisThe understanding of the origin and evolution of Pluto, and, byextension, that of a vast number of similar sized and smallerbodies in the Third Zone of the solar system, are closely tied totheir atmosphere and surface chemistry. In turn, a major role inthe composition and coloration (from dark red to yellow) of thesurface -and indirectly the atmosphere- of Pluto is played by non-ice components presumed to be organic compounds known astholins. While some of these compounds have been reproduced inthe laboratory by irradiation of native materials found in Pluto’satmosphere and surface, the number of kinds of tholins on thesurface of Pluto, and the processes responsible for their formationand distribution is still subject of investigation. We make use of

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103 – Asteroids: Observational Surveys

Pluto data from the New Horizons Ralph instrument consisting ofa multicolor/panchromatic mapper (MVIC) and mappinginfrared (IR) composition spectrometer (LEISA). For this studywe have adopted a set of scans at high spatial resolution (onaverage 2.7 km/pixel), spectroscopically analyzed for the firsttime. Our preliminary analysis shows different signatures for thedark red material that could be attributed to either grain size orcomposition/nature of the darkening agent. We characterize andinter-compare the potentially different tholins aiming atunderstanding its/their history and chemical evolution.

Author(s): Cristina M. Dalle Ore , Silvia Protopapa , Dale P.Cruikshank , William M. Grundy , S. Alan Stern , KimberlyEnnico , Catherine Olkin , Dennie Reuter , Leslie Young ,Harold A WeaverInstitution(s): 1. JHU-APL, 2. Lowell Observatory, 3. NASAAmes Research Center, 4. NASA/GSFC, 5. SETI Institute , 6.Southwest Research Institute, 7. University of MarylandContributing team(s): New Horizons Composition ThemeTeam

102.08 – Pluto's Paleoglaciation: Processes andBoundsNew Horizons imaging of Pluto’s surface shows erodedlandscapes reminiscent of assorted glaciated terrains found onthe Earth such as alpine valleys, dendritic networks and others.For example, LORRI imaging of fluted craters show radiallyoriented ridging which also resembles Pluto’s washboard terrain.Digital elevation modeling indicates that these down-gradientoriented ridges are about 3-4 km spaced apart with depthsranging from 0.2-0.5 km. Present day glaciation on Pluto ischaracterized by moving N ice blocks presumably riding over aH O ice bedrock substrate. Assuming Pluto’s ancient surface wassculpted by N glaciation, what remains a mystery is the specificnature of the glacial erosion mechanism(s) responsible for theobserved features.

To better resolve this puzzle, we perform landform evolutionmodeling of several glacial erosion processes known fromterrestrial H O ice glaciation studies. These terrestrial processes,which depend upon whether or not the glacier’s base is wet or dry,include quarrying/plucking and fluvial erosion. We also considernew erosional processes (to be described in this presentation)which are unique to the highly insulating character of solid Nincluding both phase change induced hydrofracture andgeothermally driven basal melt. Until improvements in ourknowledge of solid N ’s rheology are made available (including itsmechanical behavior as a binary/trinary mixture of CH and CO),it is difficult to assess with high precision which of theaforementioned erosion mechanisms are responsible for theobserved surface etchings.

Nevertheless, we consider a model crater surface and examine itserosional development due to flowing N glacial ice as built up

over time according to N deposition rates based on GCMmodeling of Pluto’s ancient atmosphere. For given erosionalmechanism our aim is to determine the permissible ranges ofmodel input parameters (e.g., ice strength, flow rates, grain sizes,quarrying rates, etc.) that best reproduces the observed lengthscales found on the observed fluted craters. As of the writing ofthis abstract, both the processes of quarrying and phase changeinduced hydrofracture appear to be most promising at explainingthe fluted crater ridging.

Author(s): Orkan Umurhan , Alan D. Howard , Oliver L.White , Jeffrey M. Moore , William M. Grundy , Paul M.Schenk , Ross A. Beyer , William B. McKinnon , Kelsi N.Singer , Tod R. Lauer , Andrew F. Cheng , S. Alan Stern ,Harold A Weaver , Leslie Young , Kimberly Ennico , CatherineOlkinInstitution(s): 1. Johns Hopkins University Applied PhysicsLaboratory, 2. Lowell Observatory, 3. Lunar and PlanetaryInstitute, 4. NASA Ames Research Center, 5. National OpticalAstronomy Observatory, 6. Southwest Research Institute, 7.University of Virginia, 8. Washington UniversityContributing team(s): The New Horizons Science Team

102.09D – Methane Distribution on Pluto asMapped by New Horizons' Ralph/MVIC InstrumentThe data returned from NASA’s New Horizons spacecraft hasgiven us an unprecedented, detailed look at the Pluto system.New Horizons’ Ralph/MVIC (Multispectral Visible ImagingCamera) is composed of 7 independent CCD arrays on a singlesubstrate. Among these are a red channel (540-700 nm), near-infrared channel (780-975 nm), and narrow band methanechannel (860-910 nm). By comparing the relative reflectance ofthese channels we are able to produce high-resolution methaneequivalent width (based on the 890 nm absorption band) andspectral slope maps of Pluto’s surface. From these maps we canthen quantitatively study the relationships between methanedistribution, redness, and other parameters like latitude andaltitude. In this talk, we will look at these relationships and howthey improve our understanding of Pluto’s geology and serves as aguide for refining volatile transport models.

Author(s): Alissa Earle , William M. Grundy , CarlyHowett , Catherine Olkin , Alex Harrison Parker , Paul M.Schenk , Francesca Scipioni , Ross A. Beyer , Richard P Binzel ,Dale P. Cruikshank , Kimberly Ennico , Dennie Reuter ,Bernard Schmitt , S. Alan Stern , Harold A Weaver , LeslieYoungInstitution(s): 1. JHU/APL, 2. Lowell Observatory, 3. LPI, 4.MIT, 5. NASA Ames Research Center, 6. NASA Goddard SpaceFlight Center, 7. SwRI, 8. Université Grenoble Alpes, CNRSContributing team(s): The New Horizons Science Team

103.01 – Lost Near-Earth Object CandidatesThe number of discovered Near-Earth Objects (NEOs) increasesrapidly, currently exceeding 16,000 NEOs. 2016 was the mostproductive year ever with 1,888 NEO discoveries. The NEOdiscovery process typically begins with three to five detections ofa previously unidentified object that are reported to the MinorPlanet Center (MPC). According to the plane-of-sky motion, theMPC ranks all of the new candidate discoveries for the likelihoodof being NEOs using the so-called digest score. If the digest scoreis greater than 65 the observations appear on the publiclyaccessible NEO Confirmation Page (NEOCP). Objects on theNEOCP are followed up in subsequent hours and days. Whenenough observations are collected to ensure that the object is realand that the orbit is determined, the NEO is officially announcedwith its new designation by a Minor Planet Electronic Circular.However, 14% of NEO candidates never get confirmed and aretherefore lost due to the lack of follow-up observations. Weanalyzed the lost NEO candidates that appeared on NEOCP in2013-2016 and investigated the reasons why they were not

confirmed. In particular, we studied the properties of the lostNEO candidates with a digest score of 100 that were reported bythe two most prolific discovery sites - Pan-STARRS1 (F51) andMt. Lemmon Survey (G96). We derived their plane-of-skypositions and rates, brightness, and ephemeris uncertainties, andassessed correlations with the phase of the moon and seasonaleffects apparent in the given observatory’s data. We concludedthat lost NEO candidates typically have a larger rate of motionand larger uncertainties than those of confirmed objects.However, many of the lost candidates could be recovered. In fact,the 1-sigma plane-of-sky uncertainty was still within ±0.5 deg in79% (F51) and 69% (G96) of the cases 24 hours after discoveryand in 31% (F51) and 30% (G96) of the cases 48 hours afterdiscovery. If all of the NEO candidates with a digest score of 100had been followed up, the number of discovered NEOs wouldhave been larger by 685+/-30 in 2013-2016. The measures todecrease the number of lost NEO candidates include improveduncertainty maps and uncertainties as function of time on theNEOCP.

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Author(s): Peter Veres , Davide Farnocchia , GarethWilliams , Sonia Keys , Ian Boardman , Matthew J. Holman ,Matthew J. PayneInstitution(s): 1. Harvard-Smithsonian Center forAstrophysics, 2. Jet Propulsion Laboratory

103.02 – Isolated Tracklet LinkingWe discuss our on-going work to reduce the size of the IsolatedTracklet File (ITF) : a database hosted by the Minor Planet Center(MPC) containing 14+ million unlinked detections of asteroids.The ITF is dominated by observations from Pan-STARRS1 (F51),the Catalina Sky Survey (G96), and the Spacewatch Project (691).

Survey telescopes are dependent on the follow-up capabilities ofother telescopes, but many of their detected objects are not linkedto already known objects, are are either not posted to the NEOConfirmation Page and/or are not followed up sufficiently, andtherefore have their astrometry relegated to the ITF. While manyof these asteroids may have in fact been previously observedsufficiently over longer timescales (enough to become designatedobjects), the linking of their astrometry can pose a challenge.

We have developed a search method capable of finding andlinking these isolated detections for distinct types of orbit classes,including main-belt and Hungaria objects (which often appear onthe NEOCP due to their apparent motion). We use a brute-forcetechnique which compares tracklets having motion whichsuggests they are the same object. Suspected linkages are furthertested by searching for additional tracklets over multipleoppositions.

So far, we have linked a significant portion of the ITF and havesubmitted these linkages to the MPC. We are confident in beingable to link even more tracklets. Our method can even associatethese new linkages with already designated objects, which willeventually lead to them becoming numbered objects. We hope toimprove the efficiency of all asteroid surveys as future detectionscan be batch submitted without manual review, and more objectswhich are well known will not be posted to the NEOCP.

Author(s): Robert J. Weryk , Richard J. Wainscoat , GarethWilliamsInstitution(s): 1. Minor Planet Center, Harvard SmithsonianCenter for Astrophysics, 2. Univ. of Hawaii

103.03 – Machine learning and next-generationasteroid surveysNext-generation surveys such as NEOCam (Mainzer et al., 2016)will sift through tens of millions of point source detections dailyto detect and discover asteroids. This requires new, more efficienttechniques to distinguish between solar system objects,background stars and galaxies, and artifacts such as cosmic rays,scattered light and diffraction spikes.

Supervised machine learning is a set of algorithms that allowscomputers to classify data on a training set, and then apply thatclassification to make predictions on new datasets. It has beenemployed by a broad range of fields, including computer vision,medical diagnoses, economics, and natural language processing.It has also been applied to astronomical datasets, includingtransient identification in the Palomar Transient Factory pipeline(Masci et al., 2016), and in the Pan-STARRS1 difference imaging(D. E. Wright et al., 2015).

As part of the NEOCam extended phase A work we apply machinelearning techniques to the problem of asteroid detection. Asteroiddetection is an ideal application of supervised learning, as there isa wealth of metrics associated with each extracted source, andsuitable training sets are easily created. Using the vettedNEOWISE dataset (E. L. Wright et al., 2010, Mainzer et al., 2011)as a proof-of-concept of this technique, we applied the pythonpackage sklearn. We report on reliability, feature set selection,and the suitability of various algorithms.

Author(s): Carrie R Nugent , John Dailey , Roc M. Cutri ,Frank J. Masci , Amy K. MainzerInstitution(s): 1. IPAC/Caltech, 2. Jet Propulsion Laboratory

103.04 – ATLAS: Finding the Nearest Asteroids The Asteroid Terrestrial-impact Last Alert System (ATLAS)became fully operational in June 2017. Our two robotic, 0.5 metertelescopes survey the whole accessible sky every two nights fromthe Hawaiian mountains of Haleakala and Mauna Loa. Withsensitivity to magnitude 19.5 over a field of 30 square degrees, wediscover several bright near-Earth objects every month –particularly fast moving asteroids, which can slip by other surveysthat scan the sky more slowly. Several important developments in2017 have enhanced our sensitivity to small, nearby asteroids andpotential impactors. We report on these developments –including optical adjustments, automated screening of detections,closer temporal spacing of images, and tolerance for largedeviations from Great Circle motion on the sky – and we describetheir effect in terms of measuring and discovering real objects.

Author(s): Aren Heinze , John L. Tonry , Larry Denneau ,Brian StalderInstitution(s): 1. Institute for Astronomy, University of Hawaii

103.05 – The Large Synoptic Survey Telescope as aNear-Earth Object Discovery MachineWe discuss the capabilities of LSST to discover small bodiesthroughout the Solar System, including Near-Earth Objects(NEOs) which present a challenge to automated discoverytechniques due to their rapid motion across the sky. Tests of theprototype LSST difference imaging software conducted onDECam data yield an estimate of the false detection rate at ~450sources per square degree when scaled to LSST's depth andseeing. Tests of the prototype Moving Object Processing System(MOPS) indicate that NEOs can be effectively linked with theplanned LSST cadence with this rate of false detections (Veres &Chesley 2017). Using a high-fidelity simulated survey pointinghistory, we evaluate the performance of the LSST baseline surveystrategy in discovering NEOs and Potentially HazardousAsteroids (PHAs), as well as other populations of small bodiesthroughout the solar system. With the baseline cadence, LSSTalone could discover 68.4% of PHAs with H<=22 and 63.4% ofNEOs with H<=22; when discoveries from other currently-operational surveys are included, this could rise to 80% and 78%respectively. Extension of the LSST survey by an additional twoyears and further investments in LSST software development andcompute resources can provide a further boost of about 5%.

Author(s): R. Jones , Mario Juric , Colin Slater , ZeljkoIvezic , Joachim Moeyens , Tim S. Axelrod , Kem H. Cook ,Jonathan Ashley Myers , Catherine E. PetryInstitution(s): 1. Cook Astronomical Consulting, 2. JohnsHopkins University, 3. LSST, 4. Univ. of Arizona, 5. Univ. ofWashington

103.06 – Short arc orbit determination and GaiaalertsSince October 2016, the short term (ST) processing of SolarSystem Objects (SSOs) by Gaia is up and running, and it hasproduced almost 600 alerts. A crucial point in the chain is thepossibility of performing a short arc orbit determination as soonas the object has been detected, which allows the follow up of theobject from the ground. The method we present has been recentely developed for twomain reasons: 1) search for imminent impactors within the NEO -Confirmation Page (imminent impactors are asteroids that could impact the Earth in few days from their discovery) 2) validation of the SSO-ST Gaiapipeline. We show some good confirmations on objects that could have

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104 – Planetary Rings

been discovered by Gaia, and some properties of the Gaiaastrometry for the short term.

Author(s): Federica Spoto , Paolo Tanga , Alessio DelVigna , Benoit Carry , William Thuillot , Pedro David , FrancoisMignard , Andrea Milani , Giacomo TommeiInstitution(s): 1. IMCCE, Observatoire de Paris, 2.Observatoire de la Cote d'Azur, 3. University of Pisa

104.01 – A Three-Body Resonance Confines theRing-Arcs of NeptuneTwo prominent arcs in Neptune's Adams ring have persisted formore than thirty years. Absent active confinement, the arcs wouldhave dissipated in a few years due to Kepler shear. Based onnearly 30 years of astrometry from Voyager and the Hubble SpaceTelescope, we now find that the orbital semimajor axis of the arcsfalls within ~ 10 meters of a strong three-body mean motionresonance, which involves the two nearest moons, Galatea andLarissa. Resonances of comparable strength are typically spacedby several km in the vicinity of the ring, making this particularassociation unlikely to be a coincidence. Furthermore, each arcfalls within the longitudinal boundaries of one of the 39corotation sites that this resonance creates. Collisionlessnumerical simulations confirm that the resonance is capable ofconfining ring material within these corotation sites; morerealistic, collisional simulations are in progress. The dynamicsappears to be generally similar to that from an earlier model inwhich the arcs were confined by a two-body resonance withGalatea (Porco, Science 253, 995-1001, 1991). However,subsequent observations have shown that the arcs' mean motionis definitively outside the resonance as originally proposed.Subsequent models have invoked one or more embeddedmoonlets to confine the arcs, but this new model eliminates theneed to invoke additional unseen moonlets. We hypothesize thatthe arcs comprise debris ejected from an impact into the Adamsring multiple decades ago. Only a fraction of that debris landedprecisely in the resonance. The additional arcs imaged by Voyagerin 1990 comprise material that orbited close to, but not in, theresonance; that material has dispersed slowly over thesubsequent decades, leaving only two arcs that persist to this day.

Author(s): Mark Showalter , Jack J. Lissauer , Imke dePater , Robert S FrenchInstitution(s): 1. NASA Ames, 2. SETI Institute, 3. UC Berkeley

104.02 – Dynamics of the Uranian Gamma RingThe planet Uranus is surrounded by a unique ring systemconsisting of ten narrow ringlets as well as several broad sheets ofdust. The brightest of these rings is bracketed by a pair ofsatellites, Cordelia and Ophelia, that may serve to help confinethe ring radially. Searches for smaller satellites near the othernarrow rings, however, have been unsuccessful. Hamilton et. al.2016 and Rimlinger et al. 2016 have argued that the eccentricand/or inclined uranian ringlets self confine radially by acombination of ringlet gravity and viscous forces. Importantly, noshepherd satellites are required in this model.

We apply these ideas to the uranian gamma ring, a particularlystrange ringlet which has, in addition to the standard ellipticalshape, a superposed m=0 breathing mode (French et. al. 1988).In a pure m=0 mode, the particles in an elliptical ring all reachpericenter at the same times giving the ring a circular appearance.The particles remain synced in phase and all move outwardreaching apocenter simultaneously. Thus the ring appearscircular at any given time, but the radius of the circle seems toincrease and decrease - it breathes. We investigate first thedynamics of the pure m=0 mode and show that the equilibrium isstable against small perturbations. We are currently movingtoward a more sophisticated stability analysis for the real gammaring with its unusual combination of normal modes. We willdetail our results to date and will report on our progress towardan origin scenario for this obscure but interesting ringlet.

Author(s): Douglas P. Hamilton , Thomas Rimlinger ,Joseph M. HahnInstitution(s): 1. SSI, 2. Univ. of Maryland

104.03 – On the Formation of Rings around GiantPlanetsThe origin and age of the rings around giant planets areintensively debated. It has been proposed that Saturn's rings mayform by tidal disruption of a Titan-sized primordial satellite thatmigrates inward due to the gas drag [1]. On the other hand, ringsaround giant planets may form by tidal disruption of a passinglarge Kuiper belt object during the late heavy bombardment [2]. Recently, it is suggested that a proto-Rhea and a proto-Dionemight have experienced a catastrophic collision (only 100 Myrago) [3]. Following their arguments, we performed SPHsimulations of impacts between such objects and found that theimpact is indeed catastrophic [4]. Then, we investigated the long-term evolution of the debris by using N-body simulations andanalytical arguments. We found that the debris quickly re-accreteinto new generation of Rhea- or Dione-like satellite(s) asproposed by the previous work [3], but we didn't see anysignificant spreading of the debris to form Saturn's rings [4]. In this work, we will discuss the current understanding of theorigin of rings around giant planets by referring our recent papers[2,4]. [1] Canup, R. 2010, Nature, 468, 943 [2] Hyodo, R., Charnoz, S., Ohtsuki, K. & Genda, H. 2017, Icarus,282, 195 [3] Cuk, M., Dones, L., & Nesvorny, D. 2016, ApJ, 820, 97 [4] Hyodo, R., & Charnoz, S. 2017, AJ, 154, 34

Author(s): Ryuki Hyodo , Sebastien Charnoz , HidenoriGenda , Keiji OhtsukiInstitution(s): 1. Earth-Life Science Institute/Tokyo Instituteof Technology, 2. Institut de Physique du Globe/Universite ParisDiderot, 3. Kobe University

104.04 – Saturn’s ring age from bombardmentsimulation and reflectance fit to Cassini UVISspectraThe age of Saturn’s rings is open question. Our understanding ofthis question depends heavily on the rate at which infallingmeteoritic material impacts the rings, which is a matter of somedebate. Recent estimates of this mass flux are between an order ofmagnitude higher and lower than the estimate given by Cuzzi andEstrada 1998. Given this range, we perform a meteoriticbombardment simulation, using our stochastic Markov-chainbased model, which yields fractional-pollution curves over timefor the B and C rings of Saturn. Next, using Hapke’s 2012 modelfor bidirectional reflectance for an intimate mixture of water-iceand pollutant grains, we perform a non-linear least-squares fit toCassini UVIS data with two free parameters, fractional pollutionand surface roughness of the ring particles, with a correction forthe optical depth of the rings, to determine the estimatedfractional pollution observed by UVIS. We perform this fit withtwo pollutants, amorphous carbon, and cometary materialmeasured by the Rosetta Alice UV spectrometer of comet67P/Churyumov–Gerasimenko. The fractional pollution valuereturned by our fit is then used to interpolate ring age along thefractional pollution curves returned by our Markov-chainsimulation.

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Author(s): Joshua Peter Elliott , Larry Esposito , Eric ToddBradleyInstitution(s): 1. Laboratory for Atmospheric and SpacePhysics, 2. University of Central Florida, 3. University ofColorado

104.05 – The dust distribution between F and GringThe High Rate Detector of the Cosmic Dust Analyzer aboard thespacecraft Cassini detected more than 2,000 dust particlesbetween F and G ring in the Ring Grazing Orbits. These small icydust particles of about 1 micrometer radius form a 1000 km thickdust layer with a peak density of 0.04 m . Most of the 0.8micrometer particles probably originate from the neighbouring Fand G ring. However, there is a strong indication that half of theparticles being larger than 1.6 micrometer also originate from thenearby moons Janus and Epimetheus. The particles could belifted from their surface by micrometeoroid bombardment. Thesize distribution of the particle can be described by a power lawwith an index -3.8.

Author(s): Martin Seiss , Ralf Srama , Holger Hoffmann ,Frank SpahnInstitution(s): 1. University of Potsdam, 2. University ofStuttgartContributing team(s): CDA team of the Cassini-Huygensmission

104.06 – New patterns in dust off the edge ofSaturn’s main ringsThe Roche Division is a 3000-km-span of diffuse dust located atthe outer edge of Saturn’s main ring system between the A and Frings. Several high-resolution images from Cassini’s orbitinsertion revealed two regions with higher concentrations of dustwithin the Roche Division. These proposed dusty ringlets R/2004S1 (radius=137,630 km) and R/2004 S2 (radius=138,900 km) liecoincident with the orbit of Atlas and slightly interior to the orbitof Prometheus respectively (Porco et al. 2005a Science). Usingseveral image sequences later obtained by Cassini Hedman et al.2009 (Icarus) found that these concentrations of dusty ringmaterial are not simple ringlets, but are in fact organized intocanted azimuthal brightness variations with a periodicity akin to a3:4 resonance with Saturn’s rotation rate. The presumedperturbing phenomenon is Saturn’s kilometric radiation (SKR), astrong low wavelength component of the planet’s radio emissions,whose power oscillates near the planet’s rotation rate at afrequency matching the Roche Division structures. However, overthe course of the Cassini mission the SKR period has varied by atleast 7 minutes. As a result, the location of the resonance movedinterior to the edge of the A ring and out of the Roche Divisionaround the time of Saturn’s equinox. Subsequent observations ofthe Roche Division in the this time period show no evidence ofthe prominent structures previously observed during the first fewyears of the Cassini mission. Recently, the 3:4 resonant structureshave reappeared in the Roche Division as one of the SKR periodshas increased. Here we show that the these dusty Roche Divisionstructures are present in sync with the varying SKR period usingimages sequences spanning the entire Cassini mission. We alsohighlight some particularly optimal observations, obtained duringCassini’s F-ring proximal and grand finale orbits, which reveal thedusty structure of the Roche Division in unprecedented detail.

Author(s): Robert Ormal Chancia , Matthew M. Hedman ,Shengyi Ye , William S. KurthInstitution(s): 1. University of Idaho, 2. University of Iowa

104.07 – Saturn’s rings in the near-IR: a new viewfrom Cassini-VIMSThe reflectance spectrum of Saturn’s rings in the UV, visible andnear-IR regions is dominated by fine-grained crystalline water icewith relatively small amounts of non-icy material, generallyproposed to be space-weathered silicates, organics, nano-phaseiron oxides or carbon. Previous observations by the VIMSinstrument on Cassini have revealed significant spatial variations

in the rings’ near-IR spectrum, with higher levels ofcontamination by non-icy material in the Cassini Division and Cring and larger ice grain sizes in the A and B rings (Nicholson etal. [2008], Cuzzi et al. [2009], Hedman & Nicholson [2013],Filacchione et al. [2012, 2014]). Over the past 12 months, with theCassini spacecraft passing ever closer to Saturn, VIMS hasobtained the best-ever complete spectral scans of both the sunlitand dark sides of the main rings in the 0.35-5.1 micron range,with radial resolutions of 50-120 km. The observations weremade at a uniform emission angle of ~15 degrees and a constantphase angle of 60 or 130 degrees so as to minimize extraneousphotometric variations. In addition to confirming previousresults, the new data clearly show significant smaller-scalespectral variations between the C ring plateaux and theirbackground, within the inner B ring, across several density wavehalos and in the trans-Keeler region in the outer A ring.

Author(s): Philip D. Nicholson , Matthew M. Hedman ,Stephane Le Mouélic , Gianrico Filacchione , Mauro Ciarniello ,Roger Nelson ClarkInstitution(s): 1. Cornell Univ., 2. INAF-IAPS, 3. PlanetaryScience Institute, 4. University of Idaho, 5. University of NantesContributing team(s): Cassini VIMS team

104.08 – Surface roughness of Saturn's rings andring particles inferred from thermal phase curvesWe analyze thermal phase curves of all the main rings of Saturn(the A, B, C rings, and the Cassini division) measured by both thefar-IR and mid-IR detectors of the Cassini Composite InfraRedSpectrometer (CIRS). All the rings show temperature increasestoward zero phase angle, known as an opposition effect orthermal beaming. For the C ring and Cassini division, which havelow optical depths, intra-particle shadowing is considered thedominant mechanism causing the effect. On the other hand, thephase curves of the optically thick B and A rings steepensignificantly with decreasing absolute solar elevation angle from21$^{\circ}$ to 14$^{\circ}$, suggesting inter-particleshadowing plays an important role in these rings. We employ ananalytic roughness model to estimate the degrees of surfaceroughness of the rings or ring particles. For optically thin rings,an isolated particle covered by spherical segment craters isemployed while for the thick rings we approximate a packedparticle layer as a slab covered by craters. The particles in the thinrings are found to have generally rough surfaces, except in themiddle C ring. Across the C ring, the optical depth correlates withthe degree of surface roughness. This may indicate that surfaceroughness comes mainly from particle clumping, while individualparticles have rather smooth surfaces. For the optically thickrings, the surface roughness of the particle layer is found to bemoderate. The modeled phase curves of optically thick rings areshallow if the phase angle change is primarily due to change ofobserver azimuthal angle. On the other hand, the phase curvesare steep if the phase angle change is due to change of observerelevation angle, as inter-particle shadows become visible athigher observer elevation. In addition, the area of shadowedfacets increases with decreasing solar elevation angle. Thesecombined effects explain the large seasonal change of the phasecurve steepness observed for the thick rings. The degrees ofsurface roughness inferred from the thermal phase curves aregenerally less than those from the phase curves in visible light.This is probably explained by different roughness scales seen inthermal and visible light.

Author(s): Ryuji Morishima , Neal J. Turner , LindaSpilkerInstitution(s): 1. Jet Propulsion Laboratory, 2. University ofCalifornia - Los Angels

104.09D – The Particle Size Distribution inSaturn’s C Ring from UVIS and VIMS StellarOccultations and RSS Radio OccultationsThe Cassini Ultraviolet Imaging Spectrograph (UVIS) and Visualand Infrared Mapping Spectrometer (VIMS) have measured ringoptical depths over a wide range of viewing geometries at effective

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105 – Pluto System II

wavelengths of 0.15 μm and 2.9 μm respectively. Using Voyager Sand X band radio occultations and the direct inversion of theforward scattered S band signal, Marouf et al. (1982), (1983), andZebker et al. (1985) determined the power-law size distributionparameters assuming a minimum particle radius of 1 mm. Manyfurther studies have also constrained aspects of the particle sizedistribution throughout the main rings. Marouf et al. (2008a)determined the smallest ring particles to have radii of 4-5 mmusing Cassini RSS data. Harbison et al. (2013) used VIMS solaroccultations and also found minimum particle sizes of 4-5 mm inthe C ring with q ~ 3.1, where n(a)da=Ca^(-q)da is the assumeddifferential power-law size distribution for particles of radius a.Recent studies of excess variance in stellar signal by Colwell et al.(2017, submitted) constrain the cross-section-weighted effectiveparticle radius to 1 m to several meters. Using the wide range ofviewing geometries available to VIMS and UVIS stellaroccultations we find that normal optical depth does not stronglydepend on viewing geometry at 10km resolution (which would bethe case if self-gravity wakes were present). Throughout the Cring, we fit power-law derived optical depths to those measured

by UVIS, VIMS, and by the Cassini Radio Science Subsystem(RSS) at 0.94 and 3.6 cm wavelengths to constrain the fourparameters of the size distribution at 10km radial resolution. Wefind significant amounts of particle size sorting throughout theregion with a positive correlation between maximum particlessize (amax) and normal optical depth with a mean value of amax~ 3 m in the background C ring. This correlation is negative in theC ring plateaus. We find an inverse correlation in minimumparticle radius with normal optical depth and a mean value ofamin ~ 4 mm in the background C ring with slightly largersmallest particles in the C ring plateaus.

Author(s): Richard Gregory Jerousek , Josh Colwell ,Matthew M. Hedman , Richard G. French , Essam A. Marouf ,Larry Esposito , Philip D. NicholsonInstitution(s): 1. Cornell University, 2. San Jose StateUniversity, 3. University of Central Florida, 4. University ofColorado, 5. University of Idaho, 6. Wellesley College

105.01 – Haze Heating and Cooling in Pluto’sAtmosphereDuring the Pluto flyby, an ultraviolet imaging spectrometerALICE onboard New Horizon spacecraft revealed an unexpectedcold atmosphere on Pluto (Gladstone et al., 2016). The missingcooling agent is still a mystery. Here we show that hazes in theatmosphere could explain Pluto’s temperature profile. Hazeparticles are likely formed via hydrocarbon and nitrile chemistryin Pluto’s atmosphere. Numerous global haze layers have beendiscovered in the New Horizons images obtained from the LOngRange Reconnaissance Imager (LORRI) (Gladstone et al. 2016).Based on the vertical profile of haze opacity derived from ALICEobservations (Gao et al. 2017; Young et al. 2017), we calculate theUV and visible heating and infrared cooling rates on Pluto. Wefound that the haze heating and cooling effects are largecompared with the heating from methane and cooling from CO,HCN and C2 hydrocarbons. We predict that Pluto is muchbrighter than a conventionally assumed blackbody in the mid-infrared, which can be tested by future observations.

Author(s): Xi Zhang , Darrell F. Strobel , Hiroshi ImanakaInstitution(s): 1. Johns Hopkins University, 2. NASA Ames, 3.University of California Santa Cruz

105.02 – The Effect of Aerosols on Pluto's C2Hydrocarbon ChemistryOn July 14, 2015 the New Horizons spacecraft flew through thePluto system, providing critical details about Pluto’s atmosphere.The vertical profiles of N and CH , C H , C H , and C Hderived from New Horizons Alice transmission data allow themore accurate modeling of Pluto’s atmosphere than in the pre-New Horizons era, and help better understand the physical andphotochemical processes in Pluto’s atmosphere. All the measuredC hydrocarbon densities showed an unexpected inversionbetween ~100 and 400 km, which suggests that processes otherthan chemistry play an important role in shaping their verticalprofiles. We present here a state-of-the-art Pluto Ion-Neutral-Photochemistry (Pluto INP) model that includes thecondensation onto and incorporation into aerosol particles, andevaluate the dominant production and loss processes of Chydrocarbons with a special emphasis on the role of aerosolinteraction. We found that in order to reproduce the C profilesmeasured by New Horizons, they must stick to and bepermanently removed by aerosols - a process different fromcondensation. We determined through empirical fits to the NewHorizons data that the sticking efficiency of C hydrocarbons andthe stickiness of the aerosol particles are inversely related to theavailable aerosol surface area, which has been inferred fromobservation to increase as altitude decreases. Thiscounterintuitive relationship between sticking efficiency andavailable aerosol surfaces indicates that similarly to Titan, Pluto’saerosols must harden and become less sticky as they age. Such

hardening with ageing is both necessary and sufficient to explainthe vertical profiles of C hydrocarbons in Pluto’s atmosphere.

Author(s): Adrienn Luspay-Kuti , Kathleen Mandt ,Kandis-Lea Jessup , Vincent Hue , Joshua Kammer , RachaelFilwett , Mark HamelInstitution(s): 1. Johns Hopkins University Applied PhysicsLaboratory, 2. Southwest Research Institute, 3. University ofTexas at San Antonio

105.03 – Analysis of Archival Low-Resolution Near-Infrared Spectra to Measure Pluto's Atmosphere.First detected via occultation observations, Pluto's atmospherehas changed since its discovery in the 1980s (Brosch &Mendelson, 1985; Elliot et al., 1989). Between the occultations of1988 and 2002, the surface pressure doubled (Elliot et al., 2003)as Pluto passed through perihelion in 1989. In the years followingthe 2002 occultation, only a slight increase in the surfacepressure has been noted (Young et al. 2013; Olkin et al. 2015).High-resolution spectroscopy has also been used to determine thecomposition of Pluto's atmosphere. This was first successfullydone in 1992 (Young et al., 1997), but no follow up detection wasmade until 2008 (Lellouch et al. 2009). With a gap in theoccultation and spectroscopic records, we have little informationon how and when Pluto's atmosphere changed. In order to fill inthis gap, we are examining low spectral resolution, high signal-to-noise spectra of Pluto such as Cook et al (2014) presentedpreviously. At this meeting, we will report on additional archiveobservations from Gemini. These data were taken between 2004and 2008 using the NIRI+Altair (adaptive optics instrument) andGNIRS instruments. These have resolving powers (λ/Δλ) of ~600and 6000, respectively. Both data sets cover the K-band spectralrange (1.95 to 2.40 μm) where gaseous CH has several stronglines, such as the ν +ν Q-branch near 2.317 μm. Funding for this work has been provided by NASA-PATM grantNNX12AK62G.

Author(s): Jason C. Cook , Leslie Young , Dale P.CruikshankInstitution(s): 1. NASA Ames Research Center, 2. PinheadInstititue, 3. Southwest Research Institute

105.04 – Pluto's Solar Occultation from NewHorizonsThe Alice instrument on NASA’s New Horizons spacecraftobserved an ultraviolet solar occultation by Pluto's atmosphere on2015 July 14. We derived line-of-sight abundances and localnumber densities for the major species (N and CH ) and minorhydrocarbons (C H , C H , C H ), and line-of-sight opticaldepth and extinction coefficients for the haze. Our majorconclusions are that (1) we confirmed temperatures in Pluto’supper atmosphere that were colder than expected before the New

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Horizons flyby, with upper atmospheric temperatures near 65-68K, and subsequently lower escape rates, (2) the lower atmospherewas very stable, placing the homopause within 12 km of thesurface, (3) the abundance profiles of the “C H hydrocarbons”had non-exponential density profiles that compare favorably withmodels for hydrocarbon production near 300-400 km and hazecondensation near 200 km, and (4) haze had an extinctioncoefficient approximately proportional to N density.

This work was supported by NASA’s New Horizons project.

Author(s): Leslie Young , Joshua Kammer , Andrew JSteffl , Randy Gladstone , Michael Summers , Darrell F.Strobel , David P. Hinson , S. Alan Stern , Harold A Weaver ,Catherine Olkin , Kimberly Ennico , Dave McComasInstitution(s): 1. George Mason Univ. , 2. JHU, 3. JHU/APL, 4.NASA Ames Research Center, 5. Princeton, 6. SETI, 7. SouthwestResearch Inst., 8. Southwest Research Inst.Contributing team(s): New Horizons Atmospheres ScienceTheme Team

105.05 – Triton, Pluto, and Titan: A Comparison ofHaze PhotometryAs Kuiper Belt Objects of similar size and albedo, Triton andPluto were thought to be kindred bodies exhibiting like geologichistories and features, with possible seasonal volatile transport intheir polar regions. During the flyby of Pluto in July 2015, activegeological processes were observed on the planet (Stern et al.,2015), and a substantial haze layer that was more akin to Titan’swas observed (Gladstone et. al., 2016). Multiple haze layers werediscovered surrounding the dwarf planet (Cheng et al. 2017).

Using a radiative transfer model based on Chandrasekhar’s“Planetary Problem” of an optically thin atmosphere and a surfaceof arbitrary single scattering albedo and single particle phasefunction (Chandrasekhar, 1960; Hillier et al., 1990, 1991; Burattiet al., 2011), we have characterized the optical depth and surfaceproperties of Pluto, Triton, and Titan. The forward-scatteringproperties of the haze can also be quantified by this model.Optical imaging data was analyzed for Triton and Pluto. For Titanwe made use of published data on Titan (Tomasko and West,2009) plus new Cassini Visual Infrared Mapping Spectrometer(VIMS) data, which spans the wavelength range between 0.35 and5.2 microns, and which has several channels in the mid-infraredwhere both the haze opacity is relatively low and the atmosphereis optically thin. Pluto’s atmosphere is more optically thick thanTriton’s but both are far thinner than Titan’s. The composition ofTriton’s haze layer differs markedly from Titan’s. Observations ofPluto’s haze reveal a bluish color (Gladstone et al., 2016), but thereddish tint of possible haze deposits on the surface (Stern et al.,2015; Buratti et al., 2015) suggest Pluto’s haze composition isTitan-like.


Author(s): Bonnie J. Buratti , John K. Hillier , MaryAbgarian , Nicholas Kutsop , Spencer Devins , Joel A Mosher ,S. Alan Stern , Harold A Weaver , Catherine Olkin , LeslieYoung , Kimberly EnnicoInstitution(s): 1. Cornell University, 2. Grays Harbor College,3. JHU-APL, 4. JPL, 5. NASA Ames, 6. Southwest Res InstContributing team(s): New Horizons Science Team

105.06D – High resolution 3D global climatemodeling of Pluto's atmosphere to interpret NewHorizons observationsWe use the LMD Global Climate Model (GCM) of Pluto'satmosphere to interpret New Horizons observations and simulatethe Pluto climate system. The model takes into account the cyclesof N2, CH4, CO and organic haze. It is described in details inForget et al., 2017. In order to ensure our simulations, sensitive toour initial conditions, correctly describe reality, we initialize the3D model with a set of subsurface temperatures and icedistribution, which converged toward steady state after thousandsof years simulated with a 2D version of the model (Bertrand andForget, 2016). We identify three “realistic” simulations which differ by theirspatial distribution of N2 ice in 2015 but remain consistent withthe evolution of the surface pressure (Sicardy et al., 2016) and theamount of atmospheric methane observed on Pluto (Lellouch etal., 2015). We perform a comprehensive characterization ofPluto’s atmosphere in 2015 using these simulations. Near surfacewinds can be compared to wind streaks on Pluto, while thesimulated waves and thermal structure can be compared to theNew Horizons occultations measurements (Hinson et al., 2017). In particular, we demonstrate the sensitivity of the generalcirculation to the distribution of N2 ice on the surface. Our latestresults suggest that Pluto’s atmosphere undergoes retrograderotation, a unique circulation regime in the Solar System, inducedby the condensation-sublimation of N2 in the Sputnik Planitiabasin. In Sputnik Planitia, the near-surface winds favor adeposition of haze particles in the northern and western part ofthe ice cap, which helps to interpret the different colors observed.The GCM also shows that several atmospheric phenomena are atthe origin of the cold boundary layer observed deep in the SputnikPlanitia basin, in particular the sublimation of N2, effects oftopography and the supply of cold air by winds. This allows us tounderstand the near-surface differences observed between theentry and exit temperature profiles, measured by REX on-boardNew Horizons. However it does not reproduce the differencesobserved between 6 and 30 km above the mean surface.

Author(s): Tanguy Bertrand , Francois ForgetInstitution(s): 1. Laboratoire de Météorologie Dynamique(LMD/UPMC)Contributing team(s): The New Horizons Science Team

106.01 – Ground Hazards from 100 - 300 mAsteroid ImpactsObservation programs have found over 15 000 of the estimated 1million asteroids larger than 30 m in diameter. Current estimatessuggest one such object will strike the Earth, on average, eachcentury. As observation and tracking capabilities improve it isincreasingly likely we will find asteroids on a collision coursebefore they hit us. The ability to accurately predict grounddamage from an impact is useful in determining appropriateresponse, whether through in-space mitigation or civil defensemeasures. For cases where in-space mitigation is unlikely, thespecific damage consequences help emergency planners reducecasualties. The current work extends the understanding of impactdamage by comparing the damage caused by blast overpressure,thermal radiation, and seismic waves due to 100 - 300 mdiameter asteroids which are large enough to impact the groundyet small enough that global effects are not the primary concern.

Land impacts were simulated with the ALE3D hydrocode todetermine the amount of incident kinetic energy converted toeach of the potential hazards. The resulting damage areas arecompared considering the effects of asteroid size and compositionas well as ground composition and porosity. We compare thesimulation results to semi-analytical models from the literature.

Author(s): Darrel Robertson , Eric Stern , DonovanMathiasInstitution(s): 1. NASA Ames Research Center

106.02 – Meteorite Unit Models for StructuralPropertiesTo assess the threat posed by an asteroid entering Earth’satmosphere, one must predict if, when, and how it fragmentsduring entry. A comprehensive understanding of the asteroidmaterial properties is needed to achieve this objective. At present,

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107 – The Life and Work of Toby Owen

108 – Plenary: Cassini Grand Finale

the meteorite material found on earth are the only objects froman entering asteroid that can be used as representative materialand be tested inside a laboratory. Due to complex composition, itis challenging and expensive to obtain reliable material propertiesby means of laboratory test for a family of meteorites. In order tocircumvent this challenge, meteorite unit models are developed todetermine the effective material properties including Young’smodulus, compressive and tensile strengths and Poisson’s ratio,that in turn would help deduce the properties of asteroids. Themeteorite unit model is a representative volume that accounts fordiverse minerals, porosity, cracks and matrix composition.

The Young’s Modulus and Poisson’s Ratio in the meteorite unitsare calculated by performing several hundreds of Monte Carlosimulations by randomly distributing the various phases insidethese units. Once these values are obtained, cracks are introducedin these units. The size, orientation and distribution of cracks arederived by CT-scans and visual scans of various meteorites.Subsequently, simulations are performed to attain stress-strainrelations, strength and effective modulus values in the presence ofthese cracks. The meteorite unit models are presented for H, Land LL ordinary chondrites, as well as for terrestrial basalt. In thecase of the latter, data from the simulations is compared withexperimental data to validate the methodology. These meteoriteunit models will be subsequently used in fragmentation modelingof full scale asteroids.

Author(s): Parul Agrawal , Alexander A Carlozzi , Zaid SKarajeh , Kathryn L BrysonInstitution(s): 1. AMA/NASA Ames Research Center, 2. BayArea Environmental Institute, 3. Lockheed Martin, 4.USRA/NASA Ames Research Center

106.03 – Forbidden mass ranges for showermeteoroidsBurns et al. (1979) use the parameter β to describe the ratio ofradiation pressure to gravity for a particle in the Solar System.The central potential that these particles experience is effectivelyreduced by a factor of (1 − β), which in turn lowers the escapevelocity. Burns et al. (1979) derived a simple expression for thevalue of β at which particles ejected from a comet follow parabolicorbits and thus leave the Solar System; we expand on this toderive an expression for critical β values that takes ejectionvelocity into account, assuming geometric optics. We use ourexpression to compute the critical β value and correspondingmass for cometary ejecta leading, trailing, and following theparent comet’s nucleus for 10 major meteor showers. Finally, wenumerically solve for critical β values in the case of non-geometricoptics. These values determine the mass regimes within whichmeteoroids are ejected from the Solar System and thereforecannot contribute to meteor showers.

Author(s): Althea V MoorheadInstitution(s): 1. NASA

107.01 – Toby Owen, a visionary and charismaticscientistToby’s relationship with Paris Observatory goes back to the earlybeginning of the 1970s. While he was a professor at Sony BrookUniversity (NY), he played a very active role in the developmentof the young planetology group at the Observatory. With DanielGautier, Catherine de Bergh, Michel Combes and ThérèseEncrenaz, he initiated many research projects around thecomposition and structure of planetary atmospheres, using spaceexploration and ground-based observations. With Jean-PierreMaillard and the French planetology group, he made a series ofmajor discoveries, in particular about the deuterium abundancein the solar system. In a visionary and multidisciplinaryapproach, he developed numerous research projects on allfamilies of solar system objects, planets, satellites and comets,using all wavelength spectral ranges, from ground and space. Inthe early 1980s, with Daniel Gautier and Wing Ip, Toby becamedeeply involved in the development of the Cassini-Huygens spacemission, jointly led by the United States and Europe, devoted tothe exploration of Saturn and Titan. Beyond its exceptionalscientific return, this mission has been an exemplary success interms of international cooperation between different spaceagencies. Toby was strongly in favor of bringing together scientificcommunities beyond national frontiers. With his French friendsand colleagues, at Paris Observatory and beyond, Toby hasdeveloped very strong links of scientific cooperation andfriendship. In the early 2000s, he joined the High ScientificCouncil of Paris Observatory. In 2006, with Daniel Gautier andJean-Pierre Lebreton, he received the Grand Prix Marcel Dassaultof the French Academy of Sciences. In 2007, he became DoctorHonoris Causa of Paris Observatory. He is deeply missed by hisfriends and colleagues, who all remember his generosity, hisavailability, his kindness, his simplicity and modesty.

Author(s): Therese EncrenazInstitution(s): 1. LESIA, Paris Observatory

107.02 – The Early Planetary Research of Tobias C.Owen

Tobias Chant Owen (Toby) was a graduate student of G. P.Kuiper, receiving his Ph.D. in the Dept. of Astronomy, Universityof Arizona, in 1965. His thesis was broadly titled "Studies ofPlanetary Spectra in the Photographic Infrared", and primarilypresented a study of the composition and other properties ofJupiter, as well as the abundance and surface pressure of CO onMars. The surface pressure on Mars was a topic of debate at thattime, with a wide range of diverse observational results fromseveral investigators. The Jupiter work in particular consisted ofthe analysis of Kuiper's unpublished spectra that were made withphotographic plates pushed to the longest wavelength possible,about 1120 nm, with ammonia-hypersensitized Kodak Zemulsions. Toby used the long-pathlength absorption cells at theLunar and Planetary Lab to study the spectra of CH and NH atpressures and temperatures relevant to Jupiter (and Saturn), aswell as to search for spectral signatures of potential minorcomponents of their atmospheres. Toby also obtained newspectra of Io, Ganymede, and Saturn and its rings, extended tothe long-wavelength limit of photographic emulsions. No newmolecular absorptions were found, although Owen basicallyconfirmed Kuiper's earlier result that Saturn's rings are covered(or composed of) with H O ice or frost. As he pursued a broadrange of problems of planetary atmospheres, Toby used existingand newly acquired spectra of the planets in the photographic andnear-infrared wavelength regions, together with data he obtainedin the laboratory with long-pathlength absorption cells, to resolvesome outstanding issues of unidentified spectral features and toclarify issues of the compositions, temperatures, and atmosphericpressures of several bodies. This work laid the foundation for hislater decades of studies of planetary atmospheres and cometswith spacecraft as an active participant in many US and Europeanmissions. He was very influential in shaping the science goals ofseveral missions, and in the interpretation of the results.

Author(s): Dale P. CruikshankInstitution(s): 1. NASA Ames Research Center

108.01 – Cassini's Grand Finale Science Highlights

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109 – Plenary: Juno Science Highlights

After 13 years in orbit, the Cassini-Huygens Mission to Saturnended in a science-rich blaze of glory. Cassini returned its finalbits of unique science data on September 15, 2017, as it plungedinto Saturn's atmosphere satisfying planetary protectionrequirements. Cassini's Grand Finale covered a period of roughlyfive months and ended with the first time exploration of theregion between the rings and planet.

The final close flyby of Titan in late April 2017 propelled Cassiniacross Saturn’s main rings and into its Grand Finale orbits; 22orbits that repeatedly dove between Saturn’s innermost rings andupper atmosphere making Cassini the first spacecraft to explorethis region. The last orbit turned the spacecraft into the firstSaturn upper atmospheric probe.

The Grand Finale orbits provided highest resolution observationsof both the rings and Saturn, and in-situ sampling of the ringparticle composition, Saturn's atmosphere, plasma, andinnermost radiation belts. The gravitational field was measured tounprecedented accuracy, providing information on the interiorstructure of the planet, winds in the deeper atmosphere, and massof the rings. The magnetic field provided insight into the physicalnature of the magnetic dynamo and structure of the internalmagnetic field. The ion and neutral mass spectrometer sampledthe upper atmosphere for molecules that escape the atmospherein addition to molecules originating from the rings. The cosmicdust analyzer directly sampled the composition from differentparts of the main rings for the first time. Fields and particlesinstruments directly measured the plasma environment betweenthe rings and planet.

Science highlights and new mysteries gleaned to date from theGrand Finale orbits will be discussed.

The research described in this paper was carried out in part at theJet Propulsion Laboratory, California Institute of Technology,under a contract with the National Aeronautics and SpaceAdministration. Copyright 2017 California Institute ofTechnology. Government sponsorship is acknowledged.

Author(s): Linda SpilkerInstitution(s): 1. Jet Propulsion Laboratory

108.02 – High-resolution imaging of Saturn’s mainrings during the Cassini Ring-Grazing Orbits andGrand FinaleCassini is ending its spectacular 13-year mission at Saturn with atwo-part farewell, during which it has obtained the sharpest andhighest-fidelity images ever taken of Saturn’s rings. FromDecember 2016 to April 2017, the spacecraft executed 20 near-polar orbits that passed just outside the outer edge of the mainrings; these “Ring-Grazing Orbits” provided the mission’s bestviewing of the A and F rings and the outer B ring. From April toSeptember 2017, the spacecraft is executing 22 near-polar orbitsthat pass between the innermost D ring and the planet’s clouds;this “Grand Finale” provides the mission’s best viewing of the Cand D rings and the inner B ring.

1) Clumpy Belts Clumpy structure called “straw” was previously observed in partsof the main rings [Porco et al. 2005, Science]. New images show

this structure with greater clarity. More surprisingly, new imagesreveal strong radial variations in the degree and character ofclumpiness, which are probably an index for particle propertiesand interactions. Belts with different clumpiness characteristicsare often adjacent to each other and not easily correlated withother ring characteristics. 2) Propellers A “propeller” is a local disturbance in the ring created by anembedded moon [Tiscareno et al. 2006, Nature; 2010, ApJL].Cassini has observed two classes of propellers: small propellersthat swarm in the “Propeller Belts” of the mid-A ring, and “GiantPropellers” whose individual orbits can be tracked in the outer Aring. Both are shown in unprecedented detail in new images.Targeted flybys of Giant Propellers were executed on both the litand unlit sides of the ring, yielding enhanced ability to convertbrightness to optical depth and surface density. 3) Impact Ejecta Clouds Being a large and delicate system, Saturn’s rings function as adetector of their planetary environment. Cassini images of impactejecta clouds in the rings previously constrained the population ofdecimeter-to-meter-sized meteoroids in Saturn’s vicinity[Tiscareno et al. 2013, Science]. Many more IECs are detected innew images, with color data that may constrain the particle-sizedistribution of the ejecta, and thus the fracture properties of ringmaterial.

Author(s): Matthew S. TiscarenoInstitution(s): 1. SETI InstituteContributing team(s): Cassini Imaging Team

108.03 – Saturn’s Magnetic Field from the CassiniGrand Finale orbitsThe fundamental aim of the Cassini magnetometer investigationduring the Cassini Grand Finale orbits was determination ofSaturn’s internal planetary magnetic field. The unique geometryof the orbits provided an unprecedented opportunity to measurethe intrinsic magnetic field at close distances never beforeencountered. The surprising close alignment of Saturn’s magneticaxis with its spin axis known about since the days of Pioneer 11has been a focus of the team’s analysis since Cassini Saturn OrbitInsertion. However, the varying northern and southernmagnetospheric planetary period oscillations which fill themagnetosphere, has been a factor in masking the field signalsfrom the interior. Prior to the Grand Finale orbits, the magneticfield data analysis had confirmed the extreme axisymmetry of theintrinsic magnetic field, with a dipole tilt of < 0.06°, shown noevidence for secular variation to date, established equatorial fluxexpulsion in the deep interior and revealed no polar fieldminimum up to spherical harmonic degree 5. Here we describethe magnetometer results from the Grand Finale orbits whichinclude confirmation of the extreme axisymmetric nature of theplanetary field.

Author(s): Michele Dougherty , Hao Cao , KrishanKhuranaInstitution(s): 1. Caltech, 2. Imperial College London, 3. UCLAContributing team(s): Cassini Magnetometer Team

109.01 – Unveiling the Interior of Jupiter withJuno

In orbit since July 2016, Juno is changing the way we see Jupiter,paving the way for a much better understanding of the giantplanet and its role in the formation of the solar system. Thegravity field measured during just the first two orbits is an orderof magnitude more accurate than previous measurements (Bolton et al. 2017,Folkner et al. 2017), allowing discrimination betweencontradictory measurements prior to Juno and to further

constrain interior differential rotation and structure. Interiormodels consistent with the data favour solutions in whichJupiter’s core is diluted in the envelope (Wahl et al. 2017), in linewith recent models of the formation of the planet. Anotherlongterm mystery is whether Jupiter’s observed zonal flowspenetrate deep into the interior or not (Kaspi et al. 2017). Theincreased accuracy seen in Juno’s gravity measurements in thenext orbits gives hope that this mystery can be solved. Juno’s highprecision measurements of Jupiter’s gravity field, magnetic fieldcombined with the ability to probe the deep atmosphere atmicrowave wavelengths will enable us to further unveil Jupiter'sinterior and role in the early solar system.

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110 – Asteroids: Physical Characterization

Author(s): Tristan Guillot , Yamila Miguel , William B.Hubbard , Yohai Kaspi , Burkhard Militzer , Sean Wahl ,William Folkner , Luciano Iess , Ravit Helled , Eli Galanti ,Daniele Durante , Marzia Parisi , Hao Cao , Daniel Reese ,Jonathan I. Lunine , Jeremy Bloxham , John D. Anderson ,Steven Levin , J. E. P. Connerney , Scott J. Bolton , David J.StevensonInstitution(s): 1. Berkeley , 2. Caltech, 3. Cornell University, 4.ETH, 5. Harvard University, 6. JPL, 7. LPL, 8. NASA Goddard,9. Obs. de La Cote D' Azur, 10. Observatoire de Paris, 11. SwRI,12. Università La Sapienza, 13. Weissman InstituteContributing team(s): Juno team

109.02 – Jupiter’s Magnificent AuroraI Lightshow:Initial observations and results from the JunoMission.The Juno spacecraft carries with it an impressive suite ofinstruments to study Jupiter’s aurora and its response tovariations in Jupiter’s magnetosphere. The UV and near-infraredauroral emissions serve as a “witness plate” or “viewing screen” tosome of the complex processes occurring in Jupiter’s giantmagnetosphere. Observations by the particle instruments (JEDIand JADE) measure the electron and ion particle distributions atthe spacecraft, while the MAG instrument measures theinstantaneous magnitude and orientation of Jupiter’s magneticfield and the Waves instrument measures auroral plasma wavesand radio emissions. With these measurements and modelpredictions of how the position of the spacecraft maps to theupper atmosphere of Jupiter in magnetic field coordinates, UVSand JIRAM can observe how Jupiter’s upper atmosphere reacts tothe magnetospheric loading observed at Juno. We will presentselect results from the 6 successful perijoves to date and possiblysomething from the 8 Perijove planned for September 1 , 2017.

Author(s): Thomas K. Greathouse , Scott J. Bolton , RandyGladstone , John E.P. Connerney , Alberto Adriani , William S.Kurth , Barry Mauk , Philip Valek , Steven Levin , VincentHueInstitution(s): 1. Istituto di Astrofisica e Planetologia Spaziali,2. Jet Propulsion Laboratory, 3. NASA Goddard SpaceflightCenter, 4. Southwest Research Institute, 5. The Johns HopkinsUniversity Applied Physics Laboratory, 6. University of IowaContributing team(s): Juno Mission Team

109.03 – JunoCam Images of Jupiter: A JunoCitizen Science ExperimentThe Juno mission to Jupiter carries a visible imager on itspayload primarily for outreach. The vision of JunoCam’s outreachplan was for the public to participate in, not just observe, ascience investigation. Four webpage components were developedfor uploading and downloading comments and images, followingthe steps a traditional imaging team would do: Planning,Discussion, Voting, and Processing, hosted athttps://missionjuno.swri.edu/junocam.

Lightly processed and raw JunoCam data are posted. JunoCamimages through broadband red, green and blue filters and anarrowband methane filter centered at 889 nm mounted directlyon the detector. JunoCam is a push-frame imager with a 58 degwide field of view covering a 1600 pixel width, and builds thesecond dimension of the image as the spacecraft rotates. Thisdesign enables capture of the entire pole of Jupiter in a singleimage at low emission angle when Juno is ~1 hour from perijove(closest approach). At perijove the wide field of view images are

high-resolution while still capturing entire storms, e.g. the GreatRed Spot. The public is invited to download JunoCam images, processthem, and then upload their products. Over 2000 images havebeen uploaded to the JunoCam public image gallery.Contributions range from scientific quality to artful whimsy.Artistic works are inspired by Van Gogh and Monet. Works ofwhimsy include how Jupiter might look through the viewport ofthe Millennium Falcon, or to an angel perched on a lookout, orthrough a kaleidoscope. Citizen scientists have also engaged in serious quantitativeanalysis of the images, mapping images to storms and disruptionsof the belts and zones that have been tracked from the earth. Theyare developing a phase function for Jupiter that allows the imagesto be flattened from the subsolar point to the terminator, andstudying high hazes. Citizen scientists are also developing time-lapse movies, measuring wind flow, tracking circulation patternsin the circumpolar cyclones, and looking for lightning flashes. This effort has engaged the public, with a range of personalinterests and considerable artistic and analytic talents. In return,we count our diverse public as partners in this endeavor.

Author(s): Candice Hansen , Michael Ravine , ScottBolton , Mike Caplinger , Gerald Eichstadt , Elsa Jensen ,Thomas W. Momary , Glenn S. Orton , John RogersInstitution(s): 1. British Astronomical Society, 2. Independentscholar, 3. JPL, 4. MSSS, 5. PSI, 6. SWRI

109.04 – Juno observes the dynamics of Jupiter'satmosphere Jupiter is a photogenic planet, but our knowledge of the deepatmosphere is limited. Remote sensing observations havetraditionally probed within and above the cloud tops, which are inthe 0.5-1.0 bar pressure range. Dynamical models have focusedon explaining this data set. Microwave observations from Earthprobe down to the 5-10 bar range, which overlaps with thepredicted base of the water cloud. The Galileo probe yielded dataon winds, composition, temperature gradients, clouds, radiantflux, and lightning down to 22 bars, but only at one place on theplanet. Further, the traditional observations are constrained tocover low and middle latitudes. In contrast, Juno's camera andinfrared radiometer, JunoCam and JIRAM, have yielded imagesof the poles that show cyclonic vortices in polygonalarrangements. Juno's microwave radiometer yields latitude-altitude cross sections that show dynamical features of theammonia distribution down to 50-100 bars. And Jupiter's gravityfield yields information about the winds at thousands of kmdepth, where the pressures are tens of kbars. In this talk I willsummarize the Juno observations that pertain to the dynamics ofJupiter's atmosphere and I will offer some of my owninterpretations. The new data raise as many questions as answers,but that is as it should be. As Ed Stone said during a Voyagerencounter, "If we knew all the answers before we got there, wewouldn't be learning anything."

Author(s): Andrew P. IngersollInstitution(s): 1. CaltechContributing team(s): Juno Science Team

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– Itokawa’s Opposition Surge seen byHayabusa/AMICAUsing images acquired by the Hayabusa/AMICA instrument,along with Lederer et al.’s (2008) ground-based observations, were-examine Itokawa’s disk-integrated phase curve. The AMICAimages provide critical opposition measurements (between 0.7° –

9.3° phase at 540 nm). Using Hapke’s model (2012), we fit theupdated phase curves at 5 different wavelengths. Preliminarymodeling results show a range of porosity values commensuratewith those in the literature (Ostro et al. 2004, Gundlach andBlum 2012, Kiuchi and Nakamura 2014) based on an impact-generated grain size distribution function and grain size rangeevaluations from the AMICA data (Yano et al. 2006). The widerange of porosity values for the globally-averaged regolithporosity suggests a highly variable porosity across the surface,

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matching what is seen in the AMICA imaging data (e.g. Yano et al.2006). The derived transport mean free path and the generallyforward scattering nature of the global regolith indicate scatteringcenters (such as cracks, bubbles, and inclusions) that are smallcompared to the observational wavelengths. The derived regolithproperties are compared with the imaging and sample analysisresults, testing the predictive capabilities of global disk-integratedmeasurements. This work suggests that the sub-pixel graininformation could be extracted from the photometry, especiallyaround opposition. This test is in preparation for activities insupport of Hayabusa2’s encounter with Ryugu in 2018. This workwas supported by the JAXA/ISAS Hayabusa2 program, the JSPSCore-to-Core Program’s “International Network of PlanetarySciences”, NASA’s Hayabusa2 participating scientist program(grant NNX16AL34G), and SSERVI – TREX.

Gundlach, B., Blum, J. 2012. Icarus 223, 479 – 492. Hapke, B., 2012. Theory of Reflectance and EmittanceSpectroscopy. Cambridge University Press, NY, 2 Edition, 513pp. Kiuchi, M., Nakamura, A.M., 2014. Icarus 239, 291 – 293. Lederer, S.L., et. al. 2008. Earth Planets Space 60, 49 – 59. Ostro, S.J., et al., 2004. Meteorit. Planets. Sci. 39, 407 – 424. Yano, H., et al., 2006. Science 312, 1350 – 1353.

Author(s): Deborah L. Domingue , Eri Tatsumi , FaithVilas , Susan M. Lederer , Naru Hirata , Seiji SugitaInstitution(s): 1. NASA Johnson Space Center, 2. PlanetaryScience Institute, 3. University of Aizu, 4. University of Tokyo

110.01 – Spectral Mapping at Asteroid 101955BennuThe OSIRIS-REx Asteroid Sample Return mission was launchedin September 2016. The main science surveys of asteroid 101955Bennu start in March 2019. Science instruments include aVisible-InfraRed Spectrometer (OVIRS) and a Thermal EmissionSpectrometer (OTES) that will produce observations that will beco-registered to the tessellated shape model of Bennu (thefundamental unit of which is a triangular facet). One task of thescience team is to synthesize the results in real time duringproximity operations to contribute to selection of the samplingsite. Hence, we will be focused on quickly producing spectralmaps for: (1) mineral abundances; (2) band strengths of mineralsand chemicals (including a search for the subtle ~5% absorptionfeature produced by organics in meteorites); and (3) temperatureand thermal inertia values. In sum, we will be producing onthe order of ~60 spectral maps of Bennu’s surfacecomposition and thermophysical properties. Due tooverlapping surface spots, simulations of our spectral maps showthere may be an opportunity to perform spectral super-resolution.We have a large parameter space of choices available in creatingspectral maps of Bennu, including: (a) mean facet size (shapemodel resolution), (b) percentage of overlap between subsequentspot measurements, (c) the number of spectral spots measuredper facet, and (d) the mathematical algorithm used to combinethe overlapping spots (or bin them on a per-facet basis).Projection effects -- caused by irregular sampling of an irregularlyshaped object with circular spectrometer fields-of-view and thenmapping these circles onto triangular facets -- can be intense. Toprepare for prox ops, we are simulating multiple mineralogical“truth worlds” of Bennu to study the projection effects that resultfrom our planned methods of spectral mapping. This presentationaddresses: Can we combine the three planned global surveys ofthe asteroid (to be obtained at different phase angles) to create aspectral map with higher spatial resolution than the nativespectrometer field-of-view in order to increase our confidence indetection of a spatially small occurrence of organics on Bennu?

Author(s): Beth Ellen Clark , Victoria E. Hamilton , JoshuaP. Emery , C. Luke Hawley , Ellen S. Howell , Dante Lauretta ,Amy A. Simon , Philip R Christensen , Dennis ReuterInstitution(s): 1. Arizona State University, 2. Ithaca College, 3.NASA Goddard Space Flight Center, 4. Southwest ResearchInstitute, 5. University of Arizona, 6. University of Tennessee

110.02 – Thermophysical Analysis of 101955 Bennuwith OSIRIS-RExNASA’s OSIRIS-REx mission will approach its target asteroid,(101955) Bennu, in August 2018. The primary objective of themission is to return a pristine sample from Bennu in order toaddress some of NASA’s (and humanity’s) fundamentalquestions: How did the Solar System form? How did life evolve inthe Solar System? Are asteroids harbingers of life or death – orboth? Prior to picking up the sample from the surface, OSIRIS-REx will spend more than a year characterizing the surface withcameras, spectrometers, and the laser altimeter that are on boardthe spacecraft. Global and local determination of thermophysicalproperties will inform maps of sampleability, spacecraft safety,and science value of the surface. The primary data set to be usedfor thermophysical analyses are thermal spectra from theOSIRIS-REx Thermal Emission Spectrometer (OTES). The long-wavelength end of spectra obtained by the OSIRIS-REx Visibleand InfraRed Spectrometer (OVIRS) will also be dominated bythermal emission. Full-disk observations during Approach willprovide hemispherically averaged, but rotationally resolved,properties. The Approach observations also enable directcomparisons to previous Spitzer space telescope observations ofBennu. During the Detailed Survey phase, OTES will measure theinfrared radiation from the entire surface, enabling us to maptemperatures over Bennu at seven different local times of day(3:20am, 6am, 10am, 12:30pm, 3pm, 6pm, and 8:40pm). Thediurnal temperature curves will be used to map the thermalinertia of the surface at a ~40m spatial scale. The Orbital phase ofthe mission will enable higher spatial resolution thermalobservations of up to twelve potential sample sites, andReconnaissance phase will enable even higher spatial resolutionobservations of the two highest priority potential sample sites.Thermophysical analysis of these data will be carried out with acustom thermal model that is based on the AdvancedThermophysical Model of Rozitis and Green (2011, 2012, 2013).We will present an overview of the OSIRIS-REx thermalobservations and discuss the rich array of potentialthermophysical analyses enabled by the OTES and OVIRS data ofBennu.

Author(s): Joshua Emery , Ben Rozitis , Philip RChristensen , Cristina A. Thomas , Victoria E. Hamilton , BethEllen Clark , Marco Delbo , Lucy F. Lim , Dante LaurettaInstitution(s): 1. Arizona State University, 2. CNRS, 3. IthacaCollege, 4. NASA GSFC, 5. Open University, 6. Planetary ScienceInstitute, 7. Southwest Research Institute, 8. University ofArizona, 9. University of Tennessee

110.03 – Cluster analysis of near-infraredreflectance spectra of asteroid ItokawaThe data from the analysis of samples returned by Hayabusaspacecraft have provided conclusive evidence regarding mineralcomposition and space weathering of near-Earth S-type asteroidItokawa. To apply these information to the Hayabusa remotesensing data towards revealing the formation history of Itokawa,we made a more precise near-infrared spectral map of Itokawathan the previous ones from the Hayabusa NIRS data andperformed its cluster analysis. The NIRS instrument had acquiredmore than 80,000 spatially resolved 0.75 to 2.20 micronsreflectance spectra from the surface of Itokawa. We used PCA andk-means clustering for cluster analysis and found that at leastthree different types of surface areas would exist on Itokawa.

Author(s): Tomoki Inasawa , Kohei Kitazato , Naru Hirata ,Hirohide DemuraInstitution(s): 1. University of Aizu

110.05 – Ground-based Characterization ofHayabusa2 Mission Target Asteroid 162173 RyuguIn preparation for the arrival of the Japanese Space Agency’s(JAXA) Hayabusa2 sample return mission to near-Earth asteroid(NEA) (162173) Ryugu, we took the opportunity to characterizethe target with a ground-based telescope. We observed Ryuguusing the SpeX instrument in Prism mode on NASA Infrared

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Telescope Facility on Mauna Kea, Hawaii, on July, 12 2016 whenthe asteroid was 18.87 visual magnitude, at a phase angle of 13.3°.The NIR spectra were used to constrain Ryugu’s surfacecomposition, meteorite analogs and spectral affinity to otherasteroids. We also modeled its photometric properties usingarchival data. Using the Lommel-Seeliger model we computed thepredicted flux for Ryugu at a wide range of viewing geometries aswell as albedo quantities such as geometric albedo, phaseintegral, and spherical Bond albedo. Our computed albedoquantities are consistent with results from Masateru et al. (2014).Our spectrum of Ryugu has a broad absorption band at 1 µm, aslope change at 1.6 µm, and a second broad absorption band near2.2 µm, but no well-defined absorption features over the 0.8-2.5µm range. The two broad absorption features, if confirmed, areconsistent with CO and CV chondrites. The shape of Ryugu’sspectrum matches very well those of NEA (85275) 1994 LY andMars-crossing asteroid (316720) 1998 BE7, suggesting that theirsurface regolith have similar composition. We also compared thespectrum of Ryugu with that of main belt asteroid (302) Clarissa,the largest asteroid in the Clarissa asteroid family, suggested asthe source of Ryugu by Campins et al. (2013). We found that thespectrum of Clarissa shows significant differences with our NIRspectrum of Ryugu. Our analysis shows Ryugu’s spectrum bestmatches two CM2 carbonaceous chondrites, Mighei andALH83100. We expect the surface regolith of Ryugu to be alteredby a range of factors including temperature, contamination byexogenic material, and space weathering, posing challenges tolink spacecraft and ground-based data, and sample site selection.

Author(s): Lucille Le Corre , Vishnu Reddy , Juan ASanchez , Driss Takir , Edward Cloutis , Audrey Thirouin , KrisJ Becker , Jian-Yang Li , Seiji Sugita , Eri TatsumiInstitution(s): 1. Department of Geography, University ofWinnipeg, 2. Dept. of Earth and Planetary Science, School ofScience, University of Tokyo, 3. Lowell Observatory, 4. Lunarand Planetary Laboratory, University of Arizona, 5. PlanetaryScience Institute, 6. SETI Institute, 7. USGS Astrogeology ScienceCenter

110.06 – Spitzer observations of Near Earth ObjectsThe Spitzer Space Telescope has proven to be a powerful tool tomeasure the diameters and albedos of Near Earth Objects. Wehave completed two major Spitzer NEO surveys (ExploreNEOsand NEOSurvey) and are in the middle of a culiminating thirdsurvey (NEOLegacy), with a total target list across all threeprograms of 2175 previously known NEOs. We report here on thestatus of our ongoing program and of our entire database. Wereport our measured size distribution of NEOs as well as thedistribution of albedos (and, by proxy, compositions). We alsoreport preliminary results from our new initiative to derivelightcurves from our observations. Ultimately, more than 1000NEO partial or complete lightcurves with high quality photometrywill be extracted from our data. Our new websitenearearthobjects.nau.edu includes data and modeling resultsfrom across all of our programs.

This work is based in part on observations made with the SpitzerSpace Telescope, which is operated by the Jet PropulsionLaboratory, California Institute of Technology under a contractwith NASA. Support for this work was provided by NASA throughan award issued by JPL/Caltech.

Author(s): David E. Trilling , Joseph L. Hora , MichaelMommert , Steven R. Chesley , Joshua P. Emery , Giovanni G.Fazio , Alan Harris , Michael Mueller , Howard Alan SmithInstitution(s): 1. DLR, 2. Jet Propulsion Laboratory, 3.Northern Arizona University, 4. Smithsonian AstrophysicalObservatory, 5. SRON, 6. University of Tennessee

110.07 – Albedo Corrections for High Albedo NearEarth Objects Observed With SpitzerThermal infrared observations are the most effective way tomeasure asteroid diameter and albedo. Major surveys likeNEOWISE and NEOSurvey return a small fraction of objects withalbedo values higher than that believed to exist in the near-Earth

object (NEO) population. About 10% of Spitzer-observed NEOshave nominal albedo solutions greater than 0.5. There are manypossible causes for these unrealistically high albedos, includingthermal lightcurves (leading to a mis-estimate of asteroiddiameter) or inaccurate absolute visual magnitudes (either frompoor photometry or lightcurve effects). We present here theresults of a ground-based optical photometric study of 36 highalbedo NEOs from NEOSurvey (Trilling et al. 2016) usingmeasurements from the Discovery Channel Telescope. Ourfindings indicate that uncertainty in the diameter has the mostimpact on the derived albedo of our targets, while the uncertaintyin the H-magnitude and slope parameter have smaller effects. Wesupply corrected albedos for our target list, as well as a systematicoffset dependent on the solar phase angle of the object (Mommertel al. 2017). These corrected albedo values will help constrain thealbedo range in the population to better reflect its physicalcharacteristics. This work is based in part on the observationsmade with the Spitzer Space Telescope, which is operated by theJet Propulsion Laboratory, California Institute of Technologyunder a contract with NASA. Support for this work was providedby NASA through an award issued by JPL/Caltech.

Author(s): Annika Gustafsson , David E. Trilling , MichaelMommert , Joseph L. HoraInstitution(s): 1. Harvard-Smithsonian Center forAstrophysics, 2. Northern Arizona University

110.08 – NEOShield-2 Project: Final Results onCompositional Characterization of small NEOsNEOShield-2 project was selected in the framework of theEuropean Commission H2020 program in answer to the call for“Access technologies and characterisation for Near Earth Objects(NEOs)”. NEOShield-2 project (2015-2017) is a follow-up of thefirst NEOShield (2012-2015) and includes 11 EuropeanInstitutions and Industries. The main objectives of NEOShield-2project are: i) technological development on techniques andinstruments needed for GNC for possible asteroid missions and ii)characterization of NEOs of small sizes. Our team at LESIA is the leader of the entire observationalprogram which involved complementary techniques to providephysical and compositional characterization of NEOs. Priority hasbeen given to potential space-mission targets, optimized formitigation or exploration missions. In this framework anagreement with the European Southern Observatory was signedto obtain Guaranteed Time Observations at the 3.6-meter NTTwith an allocation of 30 nights to characterize by spectroscopy thecomposition of the smaller asteroids. The objects with an absolutemagnitude larger than 20 were selected, with a priority for thevery small newly discovered objects. We obtained more than 170 new spectra of NEOs. Theobservations were performed with EFOSC2 instrument. Wecovered the wavelength interval 0.4-0.92 microns, with aresolution of R=~200. The observed asteroids include 29asteroids with diameters smaller than 100 meters and 71 withdiameters between 100 and 300 m. The taxonomic type has been assigned for 137 individual objects.Our results on NEO mineralogical compositions provide a body ofreference data directly applicable to the design and developmentof mitigation-relevant space missions. Within our survey, wefound eight D-types with ΔV < 7 km/s, four of which with ΔV < 6km/s. Among these, 2009 DL46 and (52381) 1993 HA, with a ΔVbelow 5.5 km/s and a diameter large enough to allow spacecraftoperations in their proximity, represent the best candidatescurrently known for a sample-return mission to a D-typeprimitive asteroid. Acknowledgments: The authors acknowledge the NEOShield-2funding by European Commission Horizon 2020 program(contract No. PROTEC-2-2014-640351).

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Author(s): Maria Antonieta Barucci , Davide Perna , SoniaFornasier , Alain Doressoundiram , Cateline Lantz , MarcelPopescu , Frederic Merlin , Marcello FulchignoniInstitution(s): 1. Astronomical Institute of the RomanianAcademy, 2. INAF-OAR, 3. MIT, 4. Obs. de Paris

110.09 – Do Near-Earth Asteroids and MeteoriteFalls Share the Same Source Regions?A compositional mismatch confounds the comparison betweennear-Earth asteroids (where LL ordinary chondrites dominate)and meteorite fall statistics (where H and L chondrites dominate).We have a new approach for resolving this conundrum enabled byavailable spectral information for more than 1000 near-Earthasteroids (NEAs) [1], to which we apply the Shkuratov model [2]for deriving estimates for olivine and pyroxene abundances. Asindependent variables, we correlate each NEA’s meteoritemineralogy with its dynamical source region derived from themodel by Granvik et al. [3, 4]. We contrast these “meteorite”source regions for the NEAs to the ~2 dozen available meteoritefalls having well determined orbits. Here we report the results ofthis comparison that further illuminates the role of Yarkovskydrift for delivering both meteorites and NEAs into the inner solarsystem from main-belt sources. This work supported by the National Science Foundation Grant0907766 and NASA Grant NNX10AG27G.

Author(s): Richard P Binzel , Francesca E. DeMeo , CatelineLantz , Brian Burt , Emma V Turtelboom , AlessandroMorbidelli , Mikael Granvik , Thomas H BurbineInstitution(s): 1. Massachusetts Institute of Technology, 2.Mount Holyoke College, 3. Observatoire de la Côte d’Azur, 4.Univ. Helsinki

110.10 – The LCO Follow-up and CharacterizationNetwork and AgentNEO Citizen Science ProjectThe LCO NEO Follow-up Network is using the telescopes of theLas Cumbres Observatory (LCO) and a web-based targetselection, scheduling and data reduction system to confirm NEOcandidates and characterize radar-targeted known NEOs. Startingin July 2014, the LCO NEO Follow-up Network has observed over4,500 targets and reported more than 25,000 astrometric andphotometric measurements to the Minor Planet Center.

The LCO NEO Follow-up Network's main aims are to performconfirming follow-up of the large number of NEO candidates andto perform characterization measurements of radar targets toobtain light curves and rotation rates. The NEO candidates comefrom the NEO surveys such as Catalina, PanSTARRS, ATLAS,NEOWISE and others. In particular, we are targeting objects inthe Southern Hemisphere, where the LCO NEO Follow-upNetwork is the largest resource for NEO observations.

The first phase of the LCO Network comprises nine 1-meter andseven 0.4-meter telescopes at site at McDonald Observatory(Texas), Cerro Tololo (Chile), SAAO (South Africa) and SidingSpring Observatory (Australia). The network has been fullyoperational since 2014 May, and observations are being executedremotely and robotically. Additional 0.4-meter telescopes will bedeployed in 2017 and 2x1-meter telescopes for a site at AliObservatory, Tibet are planned for 2018-2019.

We have developed web-based software called NEOexchangewhich automatically downloads and aggregates NEO candidatesfrom the Minor Planet Center's NEO Confirmation Page, theArecibo and Goldstone radar target lists and the NASA lists.NEOexchange allows the planning and scheduling of observationson the LCO Telescope Network and the tracking of the resultingblocks and generated data. We have extended the NEOexchangesoftware to include automated scheduling and moving objectdetection, with the results presented to the user via the website.

We will present results from the LCO NEO Follow-up Networkand from the development of the NEOexchange software which isused to schedule, analyze and report observations taken with the

LCO Network. In addition, we describe a Citizen Science project,AgentNEO, which uses LCO data to allow the public to find andlearn about asteroids.

Author(s): Tim Lister , Sarah Greenstreet , Edward Gomez ,Eric J. Christensen , Stephen M. LarsonInstitution(s): 1. Las Cumbres Observatory, 2. University ofArizona

110.12 – Arecibo Radar Observation of Near-EarthAsteroids: Expanded Sample Size, Determinationof Radar Albedos, and Measurements ofPolarization RatiosThe Near-Earth Asteroid (NEA) population ranges in size from afew meters to more than 10 kilometers. NEAs have a wide varietyof taxonomic classes, surface features, and shapes, includingspheroids, binary objects, contact binaries, elongated, as well asirregular bodies. Using the Arecibo Observatory planetary radarsystem, we have measured apparent rotation rate, radarreflectivity, apparent diameter, and radar albedos for over 350NEAs. The radar albedo is defined as the radar cross-sectiondivided by the geometric cross-section. If a shape model isavailable, the actual cross-section is known at the time of theobservation. Otherwise we derive a geometric cross-section froma measured diameter. When radar imaging is available, thediameter was measured from the apparent range depth. However,when radar imaging was not available, we used the continuouswave (CW) bandwidth radar measurements in conjunction withthe period of the object. The CW bandwidth provides apparentrotation rate, which, given an independent rotationmeasurement, such as from lightcurves, constrains the size of theobject. We assumed an equatorial view unless we knew the poleorientation, which gives a lower limit on the diameter. The CWalso provides the polarization ratio, which is the ratio of the SCand OC cross-sections. We confirm the trend found by Benner et al. (2008) thattaxonomic types E and V have very high polarization ratios. Wehave obtained a larger sample and can analyze additional trendswith spin, size, rotation rate, taxonomic class, polarization ratio,and radar albedo to interpret the origin of the NEAs and theirdynamical processes. The distribution of radar albedo andpolarization ratio at the smallest diameters (≤50 m) differs fromthe distribution of larger objects (>50 m), although the samplesize is limited. Additionally, we find more moderate radar albedosfor the smallest NEAs when compared to those with diameters50-150 m. We will present additional trends we find in this dataset.

Author(s): Cassandra Lejoly , Ellen S. Howell , Patrick A.Taylor , Alessondra Springmann , Anne Virkki , Michael C.Nolan , Edgard G. Rivera-Valentin , Lance A. M. Benner ,Marina Brozovic , Jon D. GiorginiInstitution(s): 1. JPL, 2. Lunar and Planetary Laboratory (U.of Arizona), 3. USRA/Arecibo

110.13 – Volatile Characterization on Near EarthAsteroidsNear Earth Asteroids (NEAs) are excellent laboratories forprocesses that affect the surfaces of airless bodies. Most NEAs arenot expected to contain surface volatiles such as OH/H O sincethey formed in the anhydrous regions of the solar system andsince their surface temperatures are high enough to evaporatesuch volatiles. However, OH/H O has been discovered on otherseemingly dry bodies in the inner solar system, such as the Moonand Vesta. Possible sources for OH/H O on these bodies includecarbonaceous chondrite impacts and interactions with protonsimplanted by solar wind. NEAs should be subjected to the sameprocesses as other “dry” bodies in the inner solar system so arehypothesized to also contain OH/H O on their surfaces. Weobserved NEAs using SpeX on NASA’s Infrared Telescope Facilityon Mauna Kea, Hawaii. Spectra were collected using both prism(0.7-2.52 µm) and LXD_short (1.67-4.2 µm) modes in order toaccurately characterize asteroid type and the 3-µm region, where

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the OH/H O signature is present. We have made 19 observationsof 13 NEAs as part of this ongoing project, with five moreobservations scheduled for this Fall. Of those, at least 3 NEAsexhibit an absorption feature in the 3-µm region: (433) Eros,(1036) Ganymed, and (3122) Florence. Eros and Ganymed haveboth been observed multiple times and by multiple observers(e.g., Rivkin et al. 2017), including two observations of Eros inFall 2016, and Florence will be observed again in earlySeptember. Of the other 10 NEAs studied, eight do not exhibit a3-µm spectral feature. The spectra for 1998 XB and 2014 JO25are too noisy to definitively determine the presence of volatiles.Characterizing the shape of the 3-µm absorption feature can yieldinformation on the source of the OH/H O on the surface. Shallowfeatures that gradually slope upward towards the continuum,such as is present in the spectra of Eros and Ganymed, indicatethe presence of OH, which is inferred to have formed due to solarwind proton bombardment. Further study of these objects willshed more light on how volatiles are brought to the surface of“dry” NEAs.

Author(s): Lauren McGraw , Joshua P. Emery , Cristina A.Thomas , Andrew S. Rivkin , Nathanael R. WigtonInstitution(s): 1. JHU/APL, 2. Oak Ridge NationalLaboratory, 3. Planetary Science Institute, 4. University ofTennessee

110.15 – Thermophysical Modeling of PotentiallyHazardous Asteroid (85989) 1999 JD6We present thermal and photometric properties of potentiallyhazardous near-Earth asteroid (85989) 1999 JD6, a contactbinary with a maximum breadth of three kilometers. JD6's shapeand rotation state are well constrained by radar and lightcurveobservations. We used the absolutely calibrated lightcurves todetermine JD6's photometric properties. We observed JD6 fromNASA's InfraRed Telescope Facility (IRTF) on three nights in2010 (from 0.8 to 4 microns) and on two nights in 2015 (from 0.7to 5 microns). Additionally, JD6 has been observed in the mid-infrared using Spitzer (in 2008 and 2009) and WISE (in 2010).We compared those observations to model spectra from ourSHERMAN software to determine JD6's thermal properties.

Author(s): Sean E. Marshall , Ellen S. Howell , Ronald J.Vervack , Christopher Magri , Jenna L. Crowell , Yanga R.Fernandez , Donald B. Campbell , Michael C. Nolan , VishnuReddy , Petr Pravec , Brandon BozekInstitution(s): 1. Academy of Sciences of the Czech Republic, 2.Cornell University, 3. Johns Hopkins University / AppliedPhysics Laboratory, 4. University of Arizona, 5. University ofCentral Florida, 6. University of Maine at Farmington, 7.University of Texas at Austin

110.16 – Laboratory study of asteroid surfaceprocesses due to electrostatic dust mobilizationOur recent laboratory work has shown a strong evidence that dustparticles on the surface of airless bodies such as asteroids areexpected to be electrostatically lofted or mobilized due toexposure to ultraviolet (UV) radiation or energetic electrons.These electrostatic processes may have a significant contributionin shaping the surfaces of asteroids or other airless bodies. Onecritical question is how efficient these processes can be inchanging the surface physical characteristics of asteroids. Herewe report a series of laboratory experiments that record dustactivities as a function of the fluxes of UV photons or energeticelectrons over a long exposure time. Our preliminary results showthat the surface morphology is changed significantly due to dustmobilization and becomes smoothened over time, on millimeter-to-centimeter scale under Earth gravity. Our results also indicatethat the dynamics of dust mobilization may be complicated bytemporal charging effect as dust moves. It was found that dustmobilization largely depends on the size and type of dustparticles. These new experimental data will help us bettercharacterize the dynamics of electrostatic dust mobilization andcan be ultimately extrapolated to the space situations in order toestimate the timescale of the electrostatic processes in

comparison to other surface processes, e.g., thermalfragmentation.

Author(s): Xu Wang , Joseph Schwan , Noah Hood , Hsiang-Wen Hsu , Mihaly HoranyiInstitution(s): 1. University of Colorado

110.17 – Genetic Algorithm-based Optimization toMatch Asteroid Energy Deposition CurvesAn asteroid entering Earth’s atmosphere deposits energy along itspath due to thermal ablation and dissipative forces that can bemeasured by ground-based and space-borne instruments.Inference of pre-entry asteroid properties and characterization ofthe atmospheric breakup is facilitated by using an analyticfragment-cloud model (FCM) in conjunction with a GeneticAlgorithm (GA). This optimization technique is used to inverselysolve for the asteroid’s entry properties, such as diameter,density, strength, velocity, entry angle, ablation coefficient, andstrength scaling, from simulations using FCM. The previousparameters’ fitness evaluation involves minimizing residuals andcomparing the incremental energy deposited to ascertain the bestmatch between the physics-based calculated energy depositionand the observed meteors. This steady-state GA provided sets ofsolutions agreeing with literature, such as the meteor fromChelyabinsk, Russia in 2013 and Tagish Lake, Canada in 2000,which were used as case studies in order to validate theoptimization routine. The assisted exploration and exploitation ofthis multi-dimensional search space enables inference anduncertainty analysis that can inform studies of near-Earthasteroids and consequently improve risk assessment.

Author(s): Ana Maria Tarano , Donovan Mathias , LorienWheeler , Sigrid CloseInstitution(s): 1. NASA Ames Research Center, 2. StanfordUniversity

110.18 – Sensitivity of Asteroid Impact Risk toUncertainty in Asteroid Properties and EntryParametersA central challenge in assessing the threat posed by asteroidsstriking Earth is the large amount of uncertainty inherentthroughout all aspects of the problem. Many asteroid propertiesare not well characterized and can range widely from strong,dense, monolithic irons to loosely bound, highly porous rubblepiles. Even for an object of known properties, the specific entryvelocity, angle, and impact location can swing the potentialconsequence from no damage to causing millions of casualties.Due to the extreme rarity of large asteroid strikes, there are alsolarge uncertainties in how different types of asteroids will interactwith the atmosphere during entry, how readily they may break upor ablate, and how much surface damage will be caused by theresulting airbursts or impacts. In this work, we use our Probabilistic Asteroid Impact Risk(PAIR) model to investigate the sensitivity of asteroid impactdamage to uncertainties in key asteroid properties, entryparameters, or modeling assumptions. The PAIR model combinesphysics-based analytic models of asteroid entry and damage in aprobabilistic Monte Carlo framework to assess the risk posed by awide range of potential impacts. The model samples fromuncertainty distributions of asteroid properties and entryparameters to generate millions of specific impact cases, andmodels the atmospheric entry and damage for each case,including blast overpressure, thermal radiation, tsunamiinundation, and global effects. To assess the risk sensitivity, wealternately fix and vary the different input parameters andcompare the effect on the resulting range of damage produced.The goal of these studies is to help guide future efforts in asteroidcharacterization and model refinement by determining whichproperties most significantly affect the potential risk.

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Author(s): Lorien Wheeler , Donovan Mathias , Jessie L.DotsonInstitution(s): 1. NASA Ames Research Center, 2. NASA Ames,CSRAContributing team(s): NASA Asteroid Threat AssessmentProject

110.19 – Bayesian modeling of the mass and densityof asteroidsMass and density are two of the fundamental properties of anyobject. In the case of near earth asteroids, knowledge about themass of an asteroid is essential for estimating the risk due to(potential) impact and planning possible mitigation options. Thedensity of an asteroid can illuminate the structure of the asteroid.A low density can be indicative of a rubble pile structure whereasa higher density can imply a monolith and/or higher metalcontent. The damage resulting from an impact of an asteroid withEarth depends on its interior structure in addition to its totalmass, and as a result, density is a key parameter to understandingthe risk of asteroid impact. Unfortunately, measuring the massand density of asteroids is challenging and often results inmeasurements with large uncertainties. In the absence of mass /density measurements for a specific object, understanding therange and distribution of likely values can facilitate probabilisticassessments of structure and impact risk.

Hierarchical Bayesian models have recently been developed toinvestigate the mass – radius relationship of exoplanets(Wolfgang, Rogers & Ford 2016) and to probabilistically forecastthe mass of bodies large enough to establish hydrostaticequilibrium over a range of 9 orders of magnitude in mass (fromplanemos to main sequence stars; Chen & Kipping 2017). Here,we extend this approach to investigate the mass and densities ofasteroids. Several candidate Bayesian models are presented, andtheir performance is assessed relative to a synthetic asteroidpopulation. In addition, a preliminary Bayesian model forprobablistically forecasting masses and densities of asteroids ispresented. The forecasting model is conditioned on existingasteroid data and includes observational errors, hyper-parameteruncertainties and intrinsic scatter.

Author(s): Jessie L. Dotson , Donovan MathiasInstitution(s): 1. NASA Ames Research Center

110.21 – University of Central Florida / Deep SpaceIndustries Asteroid Regolith SimulantsIntroduction: The University of Central Florida (UCF), inpartnership with Deep Space Industries (DSI) are working undera NASA Phase 2 SBIR contract to develop and produce a family ofasteroid regolith simulants for use in research, engineering, andmission operations testing. We base simulant formulas on themineralogy, particle size, and physical characteristics of CI, CR,CM, C2, CV, and L-Chondrite meteorites. The advantage insimulating meteorites is that the vast majority of meteoriticmaterials are common rock forming minerals that are available incommercial quantities. While formulas are guided by themeteorites our approach is one of constrained maximizationunder the limitations of safety, cost, source materials, and ease ofhandling. In all cases our goal is to deliver a safe, high fidelityanalog at moderate cost. Source Materials, Safety, and Biohazards: A critical factorin any useful simulant is to minimize handling risks forbiohazards or toxicity. All the terrestrial materials proposed forthese simulants were reviewed for potential toxicity. Of particularinterest is the organic component of volatile rich carbonaceouschondrites which contain polycyclic aromatic hydrocarbons(PAHs), some of which are known carcinogens and mutagens.Our research suggests that we can maintain rough chemicalfidelity by substituting much safer sub-bituminous coal as ourorganic analog. A second safety consideration is the choice ofserpentine group materials. While most serpentine polymorphsare quite safe we avoid fibrous chrysotile because of its asbestoscontent. Terrestrial materials identified as inputs for oursimulants are common rock forming minerals that are available

in commercial quantities. These include olivine, pyroxene,plagioclase feldspar, smectite, serpentine, saponite, pyrite, andmagnetite in amounts that are appropriate for each type. For CI'sand CR’s, their olivines tend to be Fo100 which is rare on Earth.We have substituted Fo90 olivine, but the loss of mineralogicalfidelity is offset by a major cost advantage. Family of Simulants: The CI, CR, and CM simulants arecurrently available in commercial quantities from Deep SpaceIndustries and the full list will be available by mid-2018.

Author(s): Daniel Britt , Steven D Covey , Cody SchultzInstitution(s): 1. Deep Space Industries, 2. Univ. of CentralFlorida

110.22 – Multiple scattering in planetary regolithsusing first-order incoherent interactionsWe consider scattering of light by a planetary regolith modeledusing discrete random media of spherical particles. The size of therandom medium can range from microscopic sizes of a fewwavelengths to macroscopic sizes approaching infinity. The size ofthe particles is assumed to be of the order of the wavelength. Weextend the numerical Monte Carlo method of radiative transferand coherent backscattering (RT-CB) to the case of dense packingof particles. We adopt the ensemble-averaged first-orderincoherent extinction, scattering, and absorption characteristicsof a volume element of particles as input for the RT-CB. Thevolume element must be larger than the wavelength but smallerthan the mean free path length of incoherent extinction. In theradiative transfer part, at each absorption and scattering process,we account for absorption with the help of the single-scatteringalbedo and peel off the Stokes parameters of radiation emergingfrom the medium in predefined scattering angles. We thengenerate a new scattering direction using the joint probabilitydensity for the local polar and azimuthal scattering angles. In thecoherent backscattering part, we utilize amplitude scatteringmatrices along the radiative-transfer path and the reciprocal path,and utilize the reciprocity of electromagnetic waves to verify thecomputation. We illustrate the incoherent volume-elementscattering characteristics and compare the dense-medium RT-CBto asymptotically exact results computed using the SuperpositionT-matrix method (STMM). We show that the dense-medium RT-CB compares favorably to the STMM results for the current casesof sparse and dense discrete random media studied. The novelmethod can be applied in modeling light scattering by thesurfaces of asteroids and other airless solar system objects,including UV-Vis-NIR spectroscopy, photometry, polarimetry,and radar scattering problems. Acknowledgments. Research supported by European ResearchCouncil with Advanced Grant No. 320773 SAEMPL, Scatteringand Absorption of ElectroMagnetic waves in ParticuLate media.Computational resources provided by CSC – IT Centre for ScienceLtd, Finland.

Author(s): Karri Muinonen , Johannes Markkanen , TimoVäisänen , Antti PenttiläInstitution(s): 1. University of Helsinki

110.23 – Finding the Parent Body of AnomalousAchondrite NWA 6704 Among V-type AsteroidsNorth West Africa (NWA) 6704 is an unusual, ungrouped basalticachondrite meteorite that has a striking greenish-yellow color onthe inside, and that is also relatively unaltered and un-shocked.The meteorite is coarse-grained with grain sizes around1.5millimeters, which is highly suggestive of a slow-cooling geologicenvironment. The meteorite is mostly composed oforthopyroxene (~70%), with a less abundant olivine fraction(~16%), as well as feldspar (~13%). We obtained laboratoryspectra of NWA 6704 as chips and <150-micron samples foranalysis with XRD and Ramen spectroscopy. Asteroid (4) Vestahas been proposed to be the parent body of the largest basalticachondrite clan, the HED meteorites. However, NWA 6704 hasan 0.625 micrometer absorption band feature attributed to Niin olivine that has not been detected on Vesta. We plotted the

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Band I center and Band Area Ratio (BAR) for this meteorite and itplots in the region between S(V) and S(VI) subtype. The S(V)subtype shows strong variations in olivine-feldspar ratios, andbecomes difficult to distinguish with large amounts of metalphases. The S(VI) type describes mineralogy that is consistentwith olivine-metal assemblage, with a minor pyroxenecomponent. Both of these subtypes are indicative with bodies thathave experienced some component of partial differentiation.NWA 6704 could be one of the oldest rocks in the solar system, asmultiple distinguished thermal events are revealed through U-Pbdating as well as Ar-Ar dating at ~4.52 Ga and at ~2.67 Ga. Wealso compared the spectral band parameters of NWA 6704 withV-type asteroids from the literature. Based on this comparison,the best match is an outer main belt V-type asteroid that suffereda catastrophic collision very early on in the Solar System history.

Author(s): Allison M. McGraw , Vishnu Reddy , Lucille LeCorre , Edward CloutisInstitution(s): 1. Lunar and Planetary Laboratory, 2.Planetary Science Institute, 3. Unniversity of Winnipeg

110.24 – A HST campaign to search for widelyseparated satellites around asteroid pairsAn unbound asteroid pair is formed by the rotational disruptionof an asteroid resulting in the ejection of a secondary body. Sincesome bound satellites (“binary asteroids”) are considered to formby the same mechanism, it has been suggested that the twopopulations may be linked. Indeed, photometric observationsfound a few asteroid pairs each with a bound satellite, suggestingthe disruption resulted in multiple ejected components. Thedisruptions into multiple components of P/2013 R3 and P/2012F5, observed by the Hubble Space Telescope (HST), support thisscenario and raise the question of the likelihood that rotationallydisrupted asteroid having both bound and lost components.Specifically, since the events of P/2013 R3 and P/2012 F5resulted in ejecta at high separation, high resolution observationscould reveal unknown satellites in a parameter-space notmeasureable by typical ground-based photometry. 3749 Balam,which has an unbound secondary, a near-by satellite and a widelyseparated satellite, is an example of such a complex, multi-component system. We performed a pilot campaign using WFC3 on the HST to searchfor widely separated satellites (>20 asteroid radii) orbiting theprimary members of six asteroid pairs. Since the signal from theasteroid is not completely removed by subtraction, our algorithmis sensitive to signals from satellites outside a 2-pixel radius fromthe asteroid center on the image. We tested the sensitivity of ouralgorithm with 30 synthetic satellites added to the images insideof the Hill sphere of the asteroids, and found a detection successrate of ~95%. We did not find a clear satellite signal in the images for any of thesix asteroid pair primaries. Using the synthetic satellites, wedetermined an inverse correlation of the minimal distance fromthe asteroid in which a satellite would be detected as a function ofthe diameter ratio of the satellite relative to the asteroid. Since theparameters of known asteroids with widely separated satellitesplace them away from our minimal detection limit, we concludethat the observed asteroid pairs do not have widely separatedsatellites. Thus 3749 Balam appears to be a unique case withinthe group of asteroid pairs.

Author(s): David Polishook , Nicholas Moskovitz , Susan D.Benecchi , Seth A. Jacobson , Oded AharonsonInstitution(s): 1. Lowell Observatory, 2. Planetary ScienceInstitute, 3. University of Bayreuth, 4. Weizmann Institute ofScience

110.25 – Searching for a Differentiated AsteroidFamily: A Spectral Survey of the Massalia, Merxia,and Agnia FamiliesAsteroid families were formed by catastrophic collisions or largecratering events that caused fragmentation of the parent bodyand ejection of asteroidal fragments with velocities sufficient toprevent re-accretion. Due to these formation processes, asteroid

families provide us with the opportunity to probe the interiors ofthe former parent bodies. Differentiation of a large initiallychondritic parent body is expected to result in an “onion shell"object with an iron-nickel core, a thick olivine-dominated mantle,and a thin plagioclase/pyroxene crust. However, most asteroidfamilies tend to show similar spectra (and therefore composition)among the members. Spectroscopic studies have observed apaucity of metal-like materials and olivine-dominatedassemblages within Main Belt asteroid families. The deficit of olivine-rich mantle material in the meteorite recordand in asteroid observations is known as the “Missing Mantle"problem. For years the best explanation has been the “battered tobits" hypothesis: differentiated parent bodies (aside from Vesta)were disrupted very early in the Solar System and the olivine-richmaterial was collisionally broken down over time. Alternatively,Elkins-Tanton et al. (2013) have suggested that previous work hasoverestimated the amount of olivine produced by thedifferentiation of a chondritic parent body. We have completed a visible and near-infrared wavelengthspectral survey of asteroids in the Massalia, Merxia, and Agnia S-type Main Belt asteroid families. These families were carefullychosen for the spectroscopic survey because they havecompositions most closely associated with a history of thermalmetamorphism and because they represent a range of collisionalformation scenarios. Additionally, members of the Merxia andAgnia families were identified as products of differentiation bySunshine et al. (2004). Our spectral analyses suggest that the observed families containproducts of partial differentiation. We will present results fromour spectral survey of these three families and discuss anyevidence of differentiation among the family members. We willdiscuss our band parameter analyses and compositional resultsfrom the Modified Gaussian Model (MGM).

Author(s): Cristina A. Thomas , Nicholas Moskovitz , LucyF. Lim , David E. TrillingInstitution(s): 1. Lowell Observatory, 2. NASA GSFC, 3.Northern Arizona University, 4. Planetary Science Institute

110.26 – Space Weathering of Silicate Asteroids: AnObservational InvestigationSolar wind exposure and micrometeoroid bombardment areknown to cause mineralogical changes in the upper few micronsof silicate grains (by forming amorphous “composition” rims withembedded nano-phase Fe ). These processes, jointly called spaceweathering (SW), affect the light-scattering properties andsubsequently the geometric albedo and spectral parameters(spectral slope and band depth). Earth’s Moon exhibits the wellknown “lunar-style” of SW: albedo decrease, spectral slopeincrease, and absorption band suppression. However, spacemission images of (243) Ida and (433) Eros suggest that differentSW “styles” exist among the silicate-bearing (olivine andpyroxene) S-complex asteroids, which exhibit diagnosticabsorption features near 1 & 2 μm. While Eros generally showsonly albedo differences between younger and older locations,Ida’s surface only shows changes in spectral slope and banddepth. It is not clear if these SW styles are unique to Ida and Erosor if they can be observed throughout the entire asteroidpopulation. We hypothesize that the SW styles seen on Eros and Ida also existon other asteroid surfaces. Additionally, we hypothesize thatincreased solar wind exposure, smaller regolith particles, higherolivine abundance, and older asteroid surfaces will increase theobserved degree of SW. Our dataset includes publicly availableVisible (0.4-0.8 μm) and Near Infrared (~0.7-2.5 μm) reflectancespectra of silicate-bearing asteroids (those with 1 & 2 μm bands)from the PDS and the SMASS, S OS and MIT-UH-IRTF spectralsurveys. We have also conducted a spectral survey with theIRTF/SpeX targeting 52 silicate asteroids for which we haveconstraints for regolith grain sizes from interpretation of thermal-IR data. The relevant band parameters to SW and to interpreting

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mineralogical properties are calculated using the band analysiscode, SARA. Geometric albedos are calculated using thermal-IRdata from WISE/NEOWISE. Using these derived parameters, wesearch for potential SW styles among different spectral classesand for correlations with the factors listed above. Analysis on asubset of S-types suggests that heliocentric distance correlateswith spectral slope and band depth but not albedo.

Author(s): Eric M. MacLennan , Joshua Emery , Sean S.LindsayInstitution(s): 1. University of Tennessee

110.27 – Shape models of asteroids reconstructedfrom WISE data and sparse photometryBy combining sparse-in-time photometry from the LowellObservatory photometry database with WISE observations, wereconstructed convex shape models for about 700 new asteroidsand for other ~850 we derived 'partial' models withunconstrained ecliptic longitude of the spin axis direction. In ourapproach, the WISE data were treated as reflected light, whichenabled us to directly join them with sparse photometry into onedataset that was processed by the lightcurve inversion method.This simplified treatment of thermal infrared data turned out toprovide correct results, because in most cases the phase offsetbetween optical and thermal lightcurves was small and the correctsidereal rotation period was determined. The spin and shapeparameters derived from only optical data and from acombination of optical and WISE data were very similar. The newmodels together with those already available in the Database ofAsteroid Models from Inversion Techniques (DAMIT) represent asample of ~1650 asteroids. When including also partial models,the total sample is about 2500 asteroids, which significantlyincreases the number of models with respect to those that havebeen available so far. We will show the distribution of spin axesfor different size groups and also for several collisional families.These observed distributions in general agree with theoreticalexpectations proving that smaller asteroids are more affected byYORP/Yarkovsky evolution. In asteroid families, we see a clearbimodal distribution of prograde/retrograde rotation thatcorrelates with the position to the right/left from the center of thefamily measured by the semimajor axis.

Author(s): Josef Durech , Josef Hanus , Victor Ali-LagoaInstitution(s): 1. Charles University, 2. Max-Planck-Institutfür extraterestrische Physik

110.29 – Spectra of 5261 Eureka and its family:meteorite spectral analogues of asteroidal andplanetary originThe Mars trojan asteroid (5261) Eureka is now known to be thelargest member of a dynamical family whose near-IR spectra aredominated by the 1-micron band of olivine (Christou et al. 2013,Ćuk et al. 2015, Borisov et al. 2017, Christou et al. 2017).Recently, Polishook et al. (2017) have suggested that the olivine-dominated spectra of Eureka and two of its family members implyan achondritic composition, which forms an important part oftheir argument that these objects originated in the Martianmantle.

However, we note that the olivine-rich composition of Eureka andits family members is consistent not only with achondrites ofplanetary origin, but also with achondrites of asteroidal originsuch as brachinites and indeed with the R chondrites (e.g. Lim etal. 2011, Sanchez et al. 2014). The Spitzer IRS spectrum of 5261Eureka will be discussed together with the extant near-IR spectrafrom the Eureka family in the context of candidate meteoriteanalogues and their laboratory spectra.

Author(s): Lucy F. Lim , Joshua P. Emery , MichaelMueller , Andrew S. Rivkin , Cristina A. Thomas , David E.TrillingInstitution(s): 1. JHU/APL, 2. Kapteyn Astronomical Institute,3. NASA / GSFC, 4. Northern Arizona University, 5. PSI, 6. U.Tennessee

110.30 – The orbits of satellites of (22) Kalliope and(317) RoxaneBetween October 2016 and February 2017 we imaged asteroid(22) Kalliope (10.3<V< 10.9) and its satellite Linus, and (317)Roxane (13.5 <V< 14.5) and its unnamed moon discovered byMerline et al. (IAU Circular 9099, 2) in 2009 and unobservedsince. We used two Toptica 20 W lasers to produce a 40 w laserguide star in order to provide high order adaptive opticscorrections for our 3.5 m telescope. The apparent orbits of bothsatellites carried them in and out of the asteroids’ point spreadfunction over this period, and from just this one apparition we areable to derive true orbits for both.For Kalliope’s satellite we findthe following orbit and compare it to one derived from years of 8-10 m telescope observations (Vachier, Berthier, and Marchis(2012), A&A 543, A68): Linus (here) a=1099+/-6 km;P=3.595606+/-0.000375d;T0=2457751.021+/-0.004;Pole [RA;Dec]=[194.3;-4.2];e=0 Vachier et al. a=1082+/-11 km;P=3.595712+/-0.000068d;T0=2452215.141+/-0.022;Pole [RA;Dec]=[195.1;-4.2];e=0.007+/-0.010;ω=150+/-2 We provide the first-ever orbit for Roxane’s moon, but it is notclear if the orbit is retrograde (R) or prograde (P), circular (C) oreccentric (E): Roxane S/1 (RC) a=243+/-6 km; P=11.5265+/-0.0204 d;T0=2457725.137+/-0.050; Pole[RA;Dec]=[ 96.2;-68.3]; e=0 Roxane S/1 (PC) a=245+/-6 km; P=11.5858+/-0.0203 d;T0=2457721.631+/-0.051; Pole[RA;Dec]=[275.7;+68.8]; e= 0 Roxane S/1 (RE) a=251+/-8 km; P=11.4927+/-0.0215 d;T0=2457717.730+/-0.126; Pole[RA;Dec]=[ 95.3; -67.8];e=0.178+/-0.061;ω=124+/-4 Roxane S/1 (PE) a=249+/-7 km; P=11.5594+/-0.0190 d;T0=2457717.603+/-0.162; Pole[RA;Dec]=[276.6;+69.2];e=0.133+/-0.038;ω= 230+/-5 Roxane’s moon’s orbital pole is less than 4 degrees from theEcliptic pole or Roxane’s orbital pole, but more than 22 degreesfrom Roxane’s rotational pole. Perhaps this indicates that themoon was captured from the Ecliptic plane rather than spun intoRoxanne’s equatorial plane. The Starfire Optical Range’s 3.5 m telescope is the smallestground based telescope used to derive orbits of asteroid satellites.Kalliope and Roxane follow our study of (87) Sylvia and itsRomulus (Drummond, Reynolds, and Buckman (2016), Icarus276, 107-115).

Author(s): Jack D. Drummond , Odell Reynolds , MilesBuckman , Mark EickhoffInstitution(s): 1. Starfire Optical Range

110.31 – Exploring Extreme Retro-reflection byAsteroids Using Las Cumbres Observatory RoboticTelescope ObservationsThe reflectivity of solar system surfaces ‘spikes’ sharply when theSun is less than 1 degree from directly behind the observer. TheGalileo spacecraft measured the reflectivity of part of Europa’ssurface to increase by as much as a factor of 8 as the observermoves from 5 degrees to the exact backscattering direction! Onemechanism explains this spike as coherent light scattering thatoccurs only close to this unique retro-reflection geometry. Due tothe tight linear alignment of the target, observer and Sun requiredto measure the peak brightness of the spike, accurate andcomplete measurements of the amplitude and decay of the spikeexist for only a few targets. We used the unique capabilities of theautomated Las Cumbres Observatory global telescope network(LCO) to systematically measure this extreme opposition surgefor 60+ asteroids sampling a variety of taxonomic classes in theBus/DeMeo taxonomy. Each asteroid was observed in the SDSS r’ and g’ filters during the~8 hour interval when it passes within ~0.1 deg of the pointopposite the Sun on the sky. Supporting observations of each

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asteroid with LCO collected over ~50 days measure asteroidrotation and phase angle brightness changes to enable accuratecharacterization of the retro-reflection spike. This data set vastlyincreases the number and variety of the surfaces characterized atsuch small phase angles compared to existing asteroid data. Weexamine how the spike characteristics vary with surfacecomposition, albedo, and wavelength providing new constraintson physical models of this ubiquitous yet poorly understoodphenomenon.

Analysis and modeling of these measurements will advance ourunderstanding of the physical mechanism responsible for thisenhanced retro-reflection thereby improving our ability tocharacterize these surfaces from remote observations. The abilityto infer surface physical properties from remote sensing data is akey capability for future asteroid missions, manned exploration,impact hazard assessment, and fundamental asteroid science.

Author(s): Jay D. Goguen , James M BauerInstitution(s): 1. Jet Propulsion Laboratory, CaliforniaInstitute of Technology, 2. University of Maryland

110.32 – Measuring Longitudinal Albedo Variationsof Asteroids with Ground-Based, Part-Per-MillionPolarimetryThe polarization state of asteroids encodes a wealth ofinformation about their surfaces. Linear polarization and albedoof rocky Solar System bodies has long been known to beanticorrelated (the Umov effect): dark surfaces, dominated bysingle scattering, are strongly polarized, but multiple scattering inbright surfaces randomizes the electric field orientation andreduces polarization. As an asteroid rotates, both shape changesand surface albedo variations affect reflected light flux, causingdifficulty in the identification of albedo variations. As adifferential technique, however, polarimetry is insensitive toshape changes: as total flux varies with instantaneous cross-sectional area, fractional polarization does not. Thus, rotationalvariability in linear polarization is a hallmark of albedoinhomogeneity, and it cannot be identified with photometryalone.

Until now, polarimeters have only discovered high significancerotational variation of linear polarization for one asteroid, (4)Vesta. We report on Lick 3-m observations of Main Belt asteroidswith the POLISH2 polarimeter, which utilizes photoelasticmodulators instead of a waveplate. We have not only confirmedrotational variations in (4) Vesta with 12 sigma significance in asingle, 4-hour observation, but we have also discovered variationsin (1) Ceres (5 sigma detection) and (7) Iris (7 sigma detection).We observe that both (4) Vesta and (7) Iris harbor strong linearpolarization variations, due to the presence of significant albedoheterogeneity on their surfaces, while those of (1) Ceres aremarkedly weaker due to its relatively homogenous surface.

Circular polarization, which may originate from multiplescattering or from the phase retardance introduced by ametalliferous surface, has been observed in nearly all SolarSystem bodies except for asteroids. POLISH2 simultaneouslymeasures linear and circular polarization, and we report thediscovery of non-zero circular polarization from (7) Iris with 8sigma significance. Interestingly, while the differentiated (1)Ceres and (4) show no evidence for time-averaged circularpolarization, the potentially undifferentiated (7) Iris does. Thismay indicate a metalliferous surface on (7) Iris.

Author(s): Sloane Wiktorowicz , Joseph R. MasieroInstitution(s): 1. JPL, 2. The Aerospace Corporation

110.33 – A Survey of Rotation Lightcurves of SmallJovian Trojan Asteroids in the L4 CloudJovian Trojan asteroids are of interest both as objects in theirown right and as possible relics of Solar System formation.Several lines of evidence support a common origin for, andpossible hereditary link between, Jovian Trojan asteroids and

cometary nuclei. Asteroid lightcurves give information aboutprocesses that have affected a group of asteroids including theirdensity. Due to their distance and low albedos, few comet-sizedTrojans have been studied. We have been carrying out a survey ofTrojan lightcurve properties comparing small Trojan asteroidswith comets (French et al 2015). We present new lightcurveinformation for 39 Trojans less than about 35 km in diameter. Wereport our latest results and compare them with results from thesparsely-sampled lightcurves from the Palomar Transient Factory(Waszazak et al., Chang et al. 2015). The minimum densities forobjects with complete lightcurves are estimated and are found tobe comparable to those measured for cometary nuclei. A significantfraction (~40%) of this observed small Trojan population rotates slowly (P > 24 hours),with measured periods as over 500 hours (Waszczak et al 2015).The excess of slow rotators may be due to the YORP effect.Results of the Kolmogorov-Smirnov test suggest that thedistribution of Trojan rotation rates is dissimilar to those of MainBelt Asteroids of the same size.

Author(s): Linda M. French , Robert Stephens , BrianWarner , David James , Derrick Rohl , Kyle ConnourInstitution(s): 1. Center for Solar System Studies, 2. IllinoisWesleyan Univ., 3. Laboratory for Atmospheric and SpacePhysics, 4. Sudekum Planetarium, 5. University of Washington

110.34 – Silicate Phases on the Surfaces of TrojanAsteroidsDetermining the origin of asteroids provides an effective means ofconstraining the solar system’s dynamic past. Jupiter Trojanasteroids (hereafter Trojans) may help in determining the amountof radial mixing that occurred during giant planet migration.Previous studies aimed at characterizing surface compositionshow that Trojans have low albedo surfaces and are spectrallyfeatureless in the near infrared. The thermal infrared (TIR)wavelength range has advantages for detecting silicates on lowalbedo asteroids such as Trojans. The 10 μm region exhibitsstrong features due to the Si-O fundamental molecular vibrations.Silicates that formed in the inner solar system likely underwentthermal annealing, and thus are crystalline, whereas silicates thataccreted in the outer solar system experienced less thermalprocessing, and therefore are more likely to have remained in anamorphous phase. We hypothesize that the Trojans formed in theouter solar system (i.e., the Kuiper Belt), and therefore will have amore dominant amorphous spectral silicate component. With TIRspectra from the Spitzer Space Telescope, we identifymineralogical features from the surface of 11 Trojan asteroids.Fine-grain mixtures of crystalline pyroxene and olivine exhibit a10 μm feature with sharp cutoffs between about 9 μm and 12 μm,which create a broad flat plateau. Amorphous phases, whenpresent, smooth the sharp emission features, resulting in a dome-like shape. Preliminary results indicate that the surfaces ofanalyzed Trojans contain primarily amorphous silicates.Emissivity spectra of asteroids 1986 WD and 4709 Ennomosinclude small peaks in the 10 μm region, diagnostic of smallamounts of crystalline olivine. One explanation is that Trojansformed in the same region as Kuiper Belt objects, and when giantplanet migration ensued, they were swept into Jupiter’s stableLagrange points where they are found today. As such, it ispossible that an ancestral group of Kuiper Belt objects wereseparated from Trojans during large planet migration.

Author(s): Audrey Martin , Joshua P. Emery , Sean S.LindsayInstitution(s): 1. University of Tennessee

110.35 – Color Variation on the Surfaces ofJupiter’s Greek and Trojan AsteroidsThe L4 and L5 Lagrange points of Jupiter are populated withthousands of known, and possibly hundreds of thousands ofunknown, Greek and Trojan Asteroids. Understanding theenvironmental and weathering conditions experienced by theseobjects over their lifetimes could constrain formation models for

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the Solar System. In an effort to shine some light on this issue, wehave collected partial, simultaneous, lightcurves in both Johnson-Cousins V and I filters for a dozen large Jupiter Trojans. Wefound significant signs of color variation over the surfaces of fourof these objects, and more subtle signs on an additional four. Themost convincing examples of variation occur on (4709) Ennomosand (4833) Meges. Such a variation in color with rotation likelyimplies a large surface feature such as a recent crater. That such ahigh fraction of observed Trojans display these signatures couldimply a more active collisional history for Jupiter Trojans thanpreviously thought. It is therefore likely that one or more of thetargets for the Lucy mission will have experienced a large,relatively recent, cratering event. This may help us obtain a muchmore in-depth understanding of the evolutionary processesongoing for the Jupiter Trojan populations.

Author(s): Joseph Chatelain , David E. Trilling , Joshua P.EmeryInstitution(s): 1. Northern Arizona University, 2. University ofTennessee

110.36 – Assessing Shape Characteristics of JupiterTrojans in the Kepler Campaign 6 FieldWe report estimates of spin pole orientations and body-centricaxis ratios of nine Jupiter Trojan asteroids through convex shapemodels derived from Kepler K2 photometry. Our sample containssingle-component as well as candidate binary systems (identifiedthrough lightcurve features). Photometric baselines on the targetscovered 7 to 93 full rotation periods. By incorporating a biasagainst highly elongated physical shapes, spin vector orientationsof single-component systems were constrained to several discreteregions. Single-component convex models failed to converge ontwo binary candidates while two others demonstratedpronounced tapering that may be consistent with concavities ofcontact binaries. Further work to create two-component models islikely necessary to constrain the candidate binary targets. We findthat Kepler K2 photometry provides robust datasets capable ofproviding detailed information on physical shape parameters ofJupiter Trojans.

Author(s): Benjamin Sharkey , Erin L. Ryan , Charles E.WoodwardInstitution(s): 1. LPL/U. Arizona, 2. SETI Institute, 3.University of Minnesota, MIfA

110.37 – Rotational Dynamics and SurfaceEnvironment of the Tumbling NEA (99942)ApophisOur works investigate the rotational dynamics and surfaceenvironment of the tumbling near-Earth asteroid (99942)Apophis, which is a candidate target for the Chinese asteroidmission. Combined with the previously published observationdata, we use the photometric observations obtained by the Lijiang2.4m telescope to study the spin states and rotational parametersof the asteroid. Effects of both gravitational and non-gravitationaltorques on the evolution of its rotation during the next twodecades are evaluated, particularly for the two flybys in 2029 and2036. A nutational relaxation process is also studied with thestring force taken into consideration. Furthermore, dynamicalfeatures on surface of Apophis are sketched based on the shapemodel derived from ground observations. Assuming ahomogenous density distribution, parameters such asgeopotential, surface tilt and slope and some other characteristicsare studied. Our investigation provides a better understanding onthe status of the both rotational dynamics and near-surfacedynamical status of Apophis.

Author(s): Yuhui ZhaoInstitution(s): 1. Purple Mountain Observatory, ChineseAcademy of Sciences

110.38 – Model shape and spin direction of theasteroid 2011 UW158

We determinate the spin direction and convex model shape of theNear Earth Asteroid 2011 UW158 using the lightcurves from theMinor Planet Center database and obtained from the San PedroMártir observatory (Ensenada, Baja California, Mexico) and theObservatório Astronômico do Sertão de Itaparica (Itacuruba,Pernambuco, Brazil) by mean of the light-curve inversiontechnique. The shape model was compared with the radar images obtainedfrom the 230-foot-wide Deep Space Network antenna atGoldstone, California, in concert with the National RadioAstronomy Observatory's 330-foot Green Bank Telescope in July2015 and with the spin direction published for Carbognani et. al(2016). We found that the spin direction given for Carbognani et al. doesnot correspond with the visual geometry observed from the radarimages. Also, we try to minimize the number of lightcurves thatreproduce the shape in a robust way, with the objective of to planfuture observations of asteroids better and prioritize time.

Author(s): José Silva , Filipe Monteiro , Francisco TamayoInstitution(s): 1. Instituto de Astronomia, UNAM, 2.Observatorio Nacional, 3. UANL

110.39 – RGB Colors of the Jovian Trojan AsteroidsWe use SPIRIT I&II telescopes which has 43cm diameter, toobserve around 50 Jovian Trojan asteroids. Due to the limitingmagnitude of our equipment, We only choose some brightasteriods as our targets.To testify the feasibility of using RGBBayer filter system for research project, we use the RGB Bayerfilter system instead of the Johnson-Cousins BVR filters system.Once proved, the photometry data will be significantly enlarged.More collected data can be used on scientific researches and morescholars can do relevant researches by using the RGB Bayer filtersystem. What we did is using a software called Astrometrica tomeasure the magnitude of the asteroids under RGB filter. Thenwe transform the RGB data to BVR data. Later on we calculate thecolor index by using those BVR data from our calculations. Thefinal step to do the statistic work and make graphs, and compareit with the former research data. We are aim to find same result asthe research before, or why there are differnt result. We are still in the process of handling the data, so the final resultwill be released at the conference. This project is based on dataacquired using the SPIRIT robotic telescopes at The University ofWestern Australia. We gratefully acknowledge the assistance ofPaul Luckas, SPIRIT Program Manager. The project is supported by The University of Western Australia,Youth Astronomy Teachers' Link.

Author(s): Haoyuan Chen , Xiaofei ZhangInstitution(s): 1. Beijing No.80 High SchoolContributing team(s): The University of Western Australia,Youth Astronomy Teachers' Link

110.40 – Resolved Observations of the Patroclus-Menoetius Binary The Trojan binary (617) Patroclus–Menoetius is one of the targetsof the Lucy Discovery mission. Lucy is scheduled to launch inOctober 2021. We observed this system with the Hubble SpaceTelescope in May and June 2017 in order to resolve the individualcomponents and use the relative positions to update the binaryorbit. The updated orbit is required to predict the upcomingmutual event season. A precise determination of the orbit phase,period, orbit plane and pole position that will result fromobservations of mutual events is essential for planning the Lucymission’s encounter with this system. We present results of thesuccessful HST observations including preliminary predictionsfor mutual events observable in semester 2018A.

Author(s): Keith S. Noll , William M. Grundy , Marc W.Buie , Harold F. LevisonInstitution(s): 1. Lowell Obs., 2. NASA/GSFC, 3. SwRI

110.41 – Recent impact on (4709) Ennomos?

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111 – Asteroids: Dynamics, Origins and Theory

In this work, we try to associate the albedo variations of theTrojan L5 asteroid (4709) Ennomos (Emery et al., 2016) with arelatively recent impact structure on its surface. Although themean visual albedo of Trojans is generally very low (p ~0.07,Grav et al., 2012), especially for asteroids with diameter D > 50km, Fernández et al. (2003) reported unusually high albedo of(4709) Ennomos (p ~0.12 to 0.18), which diameter is D ~ 80 km.However, the albedo of (4709) Ennomos determined from theWISE data by Grav et al. (2012) is only p ~ 0.09 and the samealbedo derived from AKARI is about p ~ 0.08 (Usui et al., 2011).One possible explanation for these discrepancies is that thealbedo of (4709) Ennomos is strongly dependent on its rotationalphase. Emery et al. (2016) reported a clear evidence of spectralslope variations of (4709) Ennomos with its rotation, what mayalso suggest an existence of a bright spot on its surface, causede.g. by impact. As we reported the asteroid family associated with(4709) Ennomos in our previous works (eg. Broz and Rozehnal,2011, Rozehnal et al., 2016), we try to simulate the family originby SPH simulations (Benz and Aspaugh, 1994).

Because the albedo variations could be in principle used toestimate an approximate size of the impact structure (in the caseof cratering event, what means M /M > 0.5) on the familyparent body an hence an approximate size of the impactor, this isa uniqe chance to compare it with the results of the SPHsimulations. In our work we also try to determine the age of theEnnomos family by simulating the dynamical evolution of oursynthetic families in different impact geometries (with different fand ω).

Author(s): Jakub Rozehnal , Miroslav BrozInstitution(s): 1. Astronomical Institute, Charles University

110.42 – Light scattering and absorption by spaceweathered planetary bodies: Novel numericalsolutionAirless planetary bodies are exposed to space weathering, i.e.,energetic electromagnetic and particle radiation, implantationand sputtering from solar wind particles, and micrometeoritebombardment.Space weathering is known to alter the physicaland chemical composition of the surface of an airless body (C.

Pieters et al., J. Geophys. Res. Planets, 121, 2016). From the lightscattering perspective, one of the key effects is the production ofnanophase iron (npFe ) near the exposed surfaces (B. Hapke, J.Geophys. Res., 106, E5, 2001). At visible and ultravioletwavelengths these particles have a strong electromagneticresponse which has a major impact on scattering and absorptionfeatures. Thus, to interpret the spectroscopic observations ofspace-weathered asteroids, the model should treat thecontributions of the npFe particles rigorously. Our numerical approach is based on the hierarchical geometricoptics (GO) and radiative transfer (RT). The modelled asteroid isassumed to consist of densely packed silicate grains with npFeinclusions. We employ our recently developed RT method fordense random media (K. Muinonen, et al., Radio Science,submitted, 2017) to compute the contributions of the npFeparticles embedded in silicate grains. The dense media RTmethod requires computing interactions of the npFe particles inthe volume element for which we use the exact fast superpositionT-matrix method (J. Markkanen, and A.J. Yuffa, JQSRT 189,2017). Reflections and refractions on the grain surface andpropagation in the grain are addressed by the GO. Finally, thestandard RT is applied to compute scattering by the entireasteroid. Our numerical method allows for a quantitative interpretation ofthe spectroscopic observations of space-weathered asteroids. Inaddition, it may be an important step towards more rigorous athermophysical model of asteroids when coupled with theradiative and conductive heat transfer techniques. Acknowledgments. Research supported by European ResearchCouncil with Advanced Grant No. 320773 SAEMPL.Computational resources provided by CSC– IT Centre for ScienceLtd, Finland.

Author(s): Johannes Markkanen , Timo Väisänen , AnttiPenttilä , Karri MuinonenInstitution(s): 1. University of Helsinki

111.01 – REBOUND-ing Off Asteroids: An N-bodyParticle Model for Ejecta Dynamics on SmallBodiesHere we describe our numerical approach to model the evolutionof ejecta clouds. Modeling with an N-body particle methodenables us to study the micro-dynamics while varying the particlesize distribution. A hydrodynamic approach loses many of thefine particle-particle interactions included in the N-body particleapproach (Artemieva 2008). We use REBOUND, an N-body integration package (Rein et al.2012) developed to model various dynamical systems (planetaryorbits, ring systems, etc.) with high resolution calculations at alower performance cost than other N-body integrators (Rein &Tamayo 2017). It offers both symplectic (WHFast) and non-symplectic (IAS15) methods (Rein & Spiegel 2014, Rein &Tamayo 2015). We primarily use the IAS15 integrator due to itsrobustness and accuracy with short interaction distances andnon-conservative forces. We implemented a wrapper (developedin Python) to handle changes in time step and integrator atdifferent stages of ejecta particle evolution. To set up the system, each particle is given a velocity away fromthe target body’s surface at a given angle within a defined ejectacone. We study the ejecta cloud evolution beginning immediatelyafter an impact rather than the actual impact itself. This modelconsiders effects such as varying particle size distribution,radiation pressure, perturbations from a binary component,particle-particle collisions and non-axisymmetric gravity of thetarget body. Restrictions on the boundaries of the target body’ssurface define the physical shape and help count the number ofparticles that land on the target body. Later, we will build thecentral body from individual particles to allow for a wider variety

of target body shapes and topographies. With our particle modeling approach, individual particletrajectories are tracked and predicted on short, medium and longtimescales. Our approach will be applied to modeling of the ejectacloud produced during the Double Asteroid Redirection Test(DART) impact (Cheng et al. 2016, Schwartz et al. 2016). We willpresent some preliminary results of our applied model andpossible applications to other asteroid impact events and Centaurring formation mechanisms.

Author(s): Jennifer Larson , Gal SaridInstitution(s): 1. University of Central Florida, 2. University ofCentral Florida, Florida Space Institute

111.02 – The University of Hawaii NEO Follow-UpProgramAt the University of Hawaii, we carry out NEO follow-upobservations for orbital refinement. We regularly observe eightnights a month using the University of Hawaii 88-inch (UH88)telescope and utilise Canada-France-Hawaii Telescope queuetime for recovery of targets with large ephemeris uncertainties.Our focus is follow-up of Virtual Impactors and faint asteroidswith magnitudes V>21. The combination of excellent atmosphericconditions on Mauna Kea and long integration times allow us toobserve asteroids as faint as V=25. Recent extensive improvements to our workhorse UH88telescope have included renovations to the telescope exterior,software upgrades, and the commissioning of the new monolithicSTA-1600 10K CCD. Recent observational highlights includeastrometry of 2017 JB2 during its diurnal retrograde loop andphotometric observations 2016 HO3 which was measured to havea synodic period of 27.90 minutes.

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Author(s): Dora Fohring , David J. Tholen , Zach Claytor ,Yudish Ramanjooloo , Denise Hung , Colin AspinInstitution(s): 1. University of Hawaii

111.05 – Asteroid Impact Risk: Ground Hazardversus Impactor SizeThe Asteroid Threat Assessment Project at NASA Ames ResearchCenter has developed a Probabilistic Asteroid Impact Risk (PAIR)model to assess the level of risk posed by potential asteroid strikeson Earth. The PAIR model combines analytic models of asteroidentry and damage in a probabilistic Monte Carlo framework toassess the ensemble risk posed by a wide range of potentialimpacts. The model samples from uncertainty distributions ofasteroid properties and entry parameters to generate millions ofspecific impact cases, and models the atmospheric entry anddamage for each case.

We present the recent results of an expanded asteroid impact riskassessment. The expanded assessment models 60 million impactcases, covering asteroid sizes from 20m up to 10km in diameter,and evaluates damage due to local blast overpressure and thermalradiation, tsunami inundation, and global effects for each case.Advancements include: (a) incorporation of a tsunami model thatis able to estimate specific flood damage for each ocean strike,accounting for local ocean depth, coastal topography, andpopulations; (b) use of improved height-of-burst maps forestimating the blast overpressure footprints, developed based onhigh-fidelity blast propagation simulations; and (c)representation of multiple damage levels for local blastoverpressure and thermal radiation exposure. Resultsdemonstrate the relative contributions of the various hazardsources to the total risk, and the significance of including lowerdamage levels in risk assessment metrics. The annualizedexpected risk is dominated by the global-effects causing large (> 1km) object impacts. Local damage, due to blast overpressure andthermal radiation, expectations peak for impactors in the fewhundred-meter size range, but the annualized damage is an orderof magnitude less than that of the larger objects. Asteroidgenerated tsunami poses very little ensemble risk compared toboth local land and global scenarios.

Author(s): Donovan Mathias , Lorien Wheeler , Jessie L.Dotson , Michael Aftosmis , Ana Maria TaranoInstitution(s): 1. NASA Ames Research Center, 2. StanfordUniversity

111.06 – Delivery of water and organics to Mercurythrough asteroid and comet impactsDetection and observation of the bright and dark polar deposits inpermanently shadowed northpolar regions of Mercury suggestthat these regions contain water and organic compounds. This issomehow surprising taking into account the planet’s proximity tothe Sun. Water flux on Mercury was studied in the past and haveshown that interplanetary dust particles, asteroids and comets arepossible sources of water on Mercury.

We are studying how much water and organics certain asteroids(C-type) and comets can deliver to Mercury. We have performednumerical gravity simulations of impact rates on Mercury withinthe past few Myr. We use the N-body integrator RMVS/Swifter topropagate the Sun and the eight planets from their currentpositions. Separately, we add comets and asteroids to thesimulations as massless test particles, based on their currentorbital distributions. In our asteroid simulations we focus onorganic-rich (C-class), basing ourselves on the dynamical modelby Greenstreet et al. (2012) and on the measured distribution oftaxonomic types across the Main Asteroid Belt. For the comets weassume a constant organic fraction. We expect to present firstresults at the meeting.

Author(s): Kateryna Frantseva , Michael Mueller , Floris F.S. van der TakInstitution(s): 1. Kapteyn Astronomical Institute, 2. SRON

111.08 – Measuring the Yarkovsky effect with LasCumbres ObservatoryThe Las Cumbres Observatory (LCO) provides an ideal platformfor follow-up and characterization of Solar System objects (e.g.asteroids, Kuiper Belt Objects, comets, Near-Earth Objects) andultimately for the discovery of new objects. We have used LCO'sglobal network of nine 1-meter telescopes to measure theYarkovsky effect on tens of asteroids through precise astrometricmeasurements using the Gaia-DR1 catalog, providing loweruncertainty with each detection. The target asteroids were pickedthrough simulated observations each month to determine theobjects for which new astrometry would yield the mostimprovement. The Gaia-DR1 release has greatly improved thequality of the astrometry obtained, making the detection of theYarkovsky effect more likely and secure by greatly reducingsystematic catalog zonal errors. With the release of DR2 next yearand the availability of good reference star colors, we will be ableto take other more subtle effects into account in the astrometricreduction. In addition, the availability of the Gaia catalog wouldallow re-measurement of past data with more accurate starcatalogs. The amount of Yarkovsky acceleration depends onseveral physical properties, such as the asteroid spin state, size,mass, and thermal properties, to which detection of the effect cangive important constraints. The effect is also important forunderstanding the transportation of asteroids and meteorites intonear-Earth space from the main belt, producing the NEOs and forthe formation and evolution of asteroid families. Determining andmodeling the Yarkovsky effect can be critical for accurateprediction of asteroid trajectories and even for impact hazardassessment. The measurements made with the help of LCO havesignificantly increased the number of known asteroids withYarkovsky detections. LCO is ideally suited to perform theseobservations due to its ability to monitor several targets overseveral days by employing dynamic scheduling, weatheravoidance, and use of multiple sites around the globe.

Author(s): Sarah Greenstreet , Davide Farnocchia , TimListerInstitution(s): 1. Jet Propulsion Laboratory, 2. Las CumbresObservatory

111.09 – Is YORP Stochastic?The YORP effect is one of the dominant processes that controlsthe dynamical evolution of small asteroids in the inner solarsystem. It has recently been hypothesized that as an asteroid’sspin rate increases due to YORP, the shape will change, which inturn causes the YORP coefficient to drastically change beforereaching the spin limit - thus making the classical YORP cycles“stochastic”. This work examines how the YORP coefficientchanges when the shape change due to spin up is constrained by asimple geophysical model that represents the effect of a cohesiverubble pile. Two processes are investigated: the relaxation of theasteroid shape, and the motion of boulders on the surface. In bothcases the changes are modeled so that the resulting shaperespects various arbitrary slope limits. Simulations of this processappear to stop the drastic change in YORP coefficients that leadsto the idea of “stochastic” YORP, except in carefully prescribedworst case scenarios. Results are presented specifically based onthe current radar and lightcurve derived shape model of Bennu.

Author(s): Jay W. McMahonInstitution(s): 1. University of Colorado - Boulder

111.10 – The weaker effects of First-order meanmotion resonances in intermediate inclinationsDuring planetary migration, a planet or planetesimal can becaptured into a low-order mean motion resonance with anotherplanet. Using a second-order expansion of the disturbing functionin eccentricity and inclination, we explore the sensitivity of thecapture probability of first-order mean motion resonances toorbital inclination. We find that second-order inclinationcontributions affect the resonance strengths, reducing them atintermediate inclinations of around $10-40^\circ$ for majorfirst-order resonances. We also integrated the Hamilton's

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equations with arbitrary initial arguments, and provided thevarying tendencies of resonance capture probabilities versusorbital inclinations for different resonances and different particleor planetary eccentricities. Resonance-weaker ranges ininclinations generally appear at the places where resonancestrengths are low, around $10-40^\circ$ in general. The weakerranges disappear with a higher particle eccentricity($\gtrsim0.05$) or planetary eccentricity ($\gtrsim0.05$).

These resonance-weaker ranges in inclinations implies thatintermediate-inclination objects are less likely to be disturbed orcaptured into the first-order resonances, which would make thementering into the chaotic area around Neptune with a largerfraction than those with low inclinations, during the epoch ofNeptune's outward migration. The privilege of high-inclinationparticles leave them to be more likely captured into NeptuneTrojans, which might be responsible for the unexpected highfraction of high-inclination Neptune Trojans.

Author(s): YuanYuan Chen , Alice C. Quillen , Yuehua MaInstitution(s): 1. Purple Mountain Observatory, 2. Universityof RochesterContributing team(s): Chinese Scholar Council, the NationalNatural Science Foundation of China, the Natural ScienceFoundation of Jiangsu Province, the Minor Planet Foundation ofthe Purple Mountain Observatory

111.11 – THE SMALL BODY GEOPHYSICALANALYSIS TOOLThe Small Body Geophysical Analysis Tool (SBGAT) that we aredeveloping aims at providing scientists and mission designerswith a comprehensive, easy to use, open-source analysis tool.SBGAT is meant for seamless generation of valuable simulateddata originating from small bodies shape models, combined withadvanced shape-modification properties.

The current status of SBGAT is as follows: The modular software architecture that was specified in the

original SBGAT proposal was implemented in the form of twodistinct packages: a dynamic library SBGAT Core containing thedata structure and algorithm backbone of SBGAT, and SBGATGui which wraps the former inside a VTK, Qt user interface tofacilitate user/data interaction. This modular developmentfacilitates maintenance and addition of new features. Note thatSBGAT Core can be utilized independently from SBGAT Gui. SBGAT is presently being hosted on a GitHub repository ownedby SBGAT’s main developer. This repository is public and can beaccessed at https://github.com/bbercovici/SBGAT. Along withthe commented code, one can find the code documentation athttps://bbercovici.github.io/sbgat-doc/index.html. This codedocumentation is constently updated in order to reflect newfunctionalities. SBGAT’s user’s manual is available athttps://github.com/bbercovici/SBGAT/wiki. This documentcontains a comprehensive tutorial indicating how to retrieve,compile and run SBGAT from scratch. Some of the upcoming development goals are listed hereafter.First, SBGAT's dynamics module will be extented: the PGMalgorithm is the only type of analysis method currentlyimplemented. Future work will therefore consists in broadeningSBGAT’s capabilities with the Spherical Harmonics Expansion ofthe gravity field and the calculation of YORP coefficients. Second,synthetic measurements will soon be available within SBGAT.The software should be able to generate synthetic observations ofdifferent type (radar, lightcurve, point clouds,...) from the shapemodel currently manipulated. Finally, shape interactioncapabilities will be added to SBGAT GUI, as it will be augmentedwith these functionalities using built-in VTK interaction methods.

Author(s): Benjamin Bercovici , Jay McMahonInstitution(s): 1. University of Colorado Boulder

112.01 – Minimoon Survey with Subaru HyperSuprime-CamWe will present the status of our search for minimoons usingHyper Suprime-Cam on the Subaru telescope on Maunkea,Hawaii. We use the term 'minimoon' to refer to objects that aregravitationally bound to the Earth-Moon system, make at leastone revolution around the barycenter in a co-rotating framerelative to the Earth-Sun axis, and are within 3 Earth Hill-sphereradii (∼12 LD). There are one or two 1 to 2 meter diameterminimoons in the steady state population at any time, and abouta dozen larger than 50 cm diameter. `Drifters' are also bound tothe Earth-Moon system but make less than one revolution aboutthe barycenter. The combined population of minimoons anddrifters provide a new opportunity for scientific exploration ofsmall asteroids and testing concepts for in-situ resourceutilization. These objects provide interesting challenges forrendezvous missions because of their limited lifetime andcomplicated trajectories. Furthermore, they are difficult to detectbecause they are small, available for a limited time period, andmove quickly across the sky.

Author(s): Robert Jedicke , Ben Boe , Bryce T. Bolin ,William Bottke , Monique Chyba , Larry Denneau , CurtDodds , Mikael Granvik , Jan Kleyna , Robert J. WerykInstitution(s): 1. Nice Observatory, 2. Southwest ResearchInstitute, 3. U. Hawaii, 4. U. Helsinki

112.04 – Near-Earth Object Survey SimulationSoftwareThere is a significant interest in Near-Earth objects (NEOs)because they pose an impact threat to Earth, offer valuablescientific information, and are potential targets for robotic andhuman exploration. The number of NEO discoveries has beenrising rapidly over the last two decades with over 1800 being

discovered last year, making the total number of known NEOs>16000. Pan-STARRS and the Catalina Sky Survey are currentlythe most prolific NEO surveys, having discovered >1600 NEOsbetween them in 2016. As next generation surveys such as LargeSynoptic Survey Telescope (LSST) and the proposed Near-EarthObject Camera (NEOCam) become operational in the nextdecade, the discovery rate is expected to increase tremendously.Coordination between various survey telescopes will be necessaryin order to optimize NEO discoveries and create a unified globalNEO discovery network. We are collaborating on a community-based, open-source software project to simulate asteroid surveysto facilitate such coordination and develop strategies forimproving discovery efficiency. Our effort so far has focused ondevelopment of a fast and efficient tool capable of accepting user-defined asteroid population models and telescope parameterssuch as a list of pointing angles and camera field-of-view, andgenerating an output list of detectable asteroids. The softwaretakes advantage of the widely used and tested SPICE library andarchitecture developed by NASA’s Navigation and AncillaryInformation Facility (Acton, 1996) for saving and retrievingasteroid trajectories and camera pointing. Orbit propagation isdone using OpenOrb (Granvik et al. 2009) but future versionswill allow the user to plug in a propagator of their choice. Thesoftware allows the simulation of both ground-based and space-based surveys. Performance is being tested using the Grav et al.(2011) asteroid population model and the LSST simulated survey“enigma_1189”.

Author(s): Shantanu P Naidu , Steven R. Chesley , DavideFarnocchiaInstitution(s): 1. Jet Propulsion Laboratory, CaliforniaInstitute of Technology

112.06 – Improved Asteroid Astrometry with theGaia Catalog

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In the ten months since the Gaia-DR1 catalog was released, wehave reported over 2500 astrometric Gaia-based observations ofasteroids, mostly of the near-Earth variety, but whatever otherasteroids that appear in the same field also get measured andreported. The astrometric solutions have contributed an averageof 0.01 arcsec to the overall astrometric uncertainty, and thereduced chi-squared statistics indicate that our ability to measurethe centroid of an often-trailed reference star is the limiting factorin the quality of the astrometric solutions, not the catalogcoordinates of the stars themselves. The centroiding accuracy onthe targets has averaged about 0.05 arcsec, meaning that wefinally have an astrometric reference catalog that is not thelimiting factor in the quality of the astrometry reduced using it.Gaia-DR2 is scheduled for 2018 April, and its inclusion of propermotions will eliminate one shortcoming of the current catalog.DR1 also suffers from non-uniform sky coverage to the samelimiting magnitude, as we have encountered two 7.5 arcmin fieldswith no Gaia stars with which to perform the astrometriccalibration, forcing us to fall back on the PPMXL catalog. A thirdfield has only six Gaia stars in it, poorly distributed with respectto the location of the asteroid, even though there are plenty ofother suitably bright stars available. The Gaia photometry is alsoa huge improvement over the mostly photographic magnitudescontained in the comparably deep USNO-B1.0 and PPMXLcatalogs, though we have also encountered some fields wheresome of the stars' G magnitudes are systematically off by as muchas a magnitude. Presumably this issue will also be solved in DR2.We have computed a transformation between Gaia G magnitudesand Johnson V magnitudes using Landolt's photometry of acouple hundred standard stars. Assuming a typical asteroid color,we recommend using a correction of +0.28 mag to transform aGaia G magnitude into a Johnson V magnitude. In cases of knownasteroid V-R or V-I color, we can provide second-orderpolynomial transformation equations.

Author(s): David J. Tholen , Yudish Ramanjooloo , DoraFohring , Denise Hung , Zach ClaytorInstitution(s): 1. Univ. of Hawaii

112.08 – Update on Spacewatch Observations ofNear-Earth ObjectsSpacewatch performs targeted astrometric follow-up of near-Earth objects, primarily asteroids (NEAs), to improve knowledgeof their orbits. We have a noteworthy history of asteroid andcomet observations beginning in 1984 as the first survey to useCCDs to scan the sky for asteroids and comets. Currently, wemeasure simultaneous astrometry and photometry ofobservations during an average of 24 nights per lunation (darkand gray time) as the exclusive users of a 1.8-m telescope and a0.9-m telescope on Kitt Peak. In addition, we use bright time onthe 2.3-m Bok Telescope and the 4-m Mayall Telescope on KittPeak to chase fainter targets. Continued astrometric follow-uphelps to prevent potentially hazardous objects and scientificallyinteresting NEAs from becoming lost.

We prioritize virtual impactors, MPC confirmation page objects,potentially hazardous asteroids (PHAs) with close approacheswithin 0.03 AU in the next 30 years, upcoming radar targets withastrometry requests, Yarkovsky effect candidates, NEAs withexisting characterization data (WISE, Spitzer, SMASS, MANOS),possible spacecraft destinations (NHATS), and requests from thecommunity.

In mid October 2015, we switched from survey mode to targetedastrometry on the 0.9-m telescope. From 2015 October 15through 2017 June 29 (1.7yr), Spacewatch (observatory codes 291,691, and ^695) had 20951 MPC-accepted NEO lines of astrometrycorresponding to measurements of 2647 different NEOs. Thisincludes 4801 PHA lines of astrometry corresponding to 426different PHAs, of which 223 lines were at apparent magnitudesV>=22.5. We observed 43% of all NEAs and 52% of allunnumbered NEAs that were observed by any observatory duringthat period. We observed 50% of all PHAs and 64% of allunnumbered PHAs observed during that period. These statisticsdo not include submitted measurements of confirmation page

objects that were not confirmed as NEAs. Support of Spacewatch is from NASA/NEOO grants, the Lunarand Planetary Laboratory, Steward Observatory, Kitt PeakNational Observatory, the Brinson Foundation of Chicago, IL, theestates of R. S. Vail and R. L. Waland, and other private donors.We are also indebted to the MPC and JPL for their web services.

Author(s): Melissa Brucker , Robert S. McMillan , TerryBressi , Jeff Larsen , Ron Mastaler , Mike Read , Jim Scotti ,Andrew TubbioloInstitution(s): 1. United States Naval Academy, 2. Universityof Arizona

112.09 – Arecibo Radar Observations of Near-EarthAsteroids The Arecibo S-Band (2.38 GHz, 12.6 cm; 1 MW) planetary radarsystem at the 305-m William E. Gordon Telescope in Arecibo,Puerto Rico is the most active, most powerful, and most sensitiveplanetary radar facility in the world. As such, Arecibo is vital forpost-discovery characterization and orbital refinement of near-Earth asteroids. Since August 2016, the program has observed100 near-Earth asteroids (NEAs), of which 38 are classified aspotentially hazardous to Earth and 31 are compliant with theNASA Near-Earth Object Human Space Flight Accessible TargetsStudy (NHATS). Arecibo observations are critical for identifyingNEAs that may be on a collision course with Earth in addition toproviding detailed physical characterization of the objectsthemselves in terms of size, shape, spin, and surface properties,which are valuable for assessing impact mitigation strategies.Here, we will present a sampling of the asteroid zoo observed byArecibo, including press-noted asteroids 2014 JO25 and the(163693) Atira binary system.

Author(s): Edgard G. Rivera-Valentin , Patrick A. Taylor ,Anne Virkki , Sriram Saran Bhiravarasu , Flaviane Venditti ,Luisa Fernanda Zambrano-Marin , Betzaida Aponte-HernandezInstitution(s): 1. Arecibo Observatory (USRA)

112.10 – Simulation of a wide area survey for NEOswith Pan-STARRS PS1 & PS2 TelescopesWe have performed a new survey simulation for a wide areasurvey with PS1 & PS2 as part of our quest to optimize thediscovery rate of Near Earth Objects with the full Pan-STARRSsystem. The survey is intended to be as unbiased and as completeas possible given the available sky visibility and the anticipatedperformance of the PS1 and PS2 telescopes working together. Thesimulation includes a complete model of both telescopes, cameraand slew overhead, sky visibility, moon phase, galactic planeexclusion, and weather. The performance of the resulting surveystrategy is then evaluated using the method of Lilly et. al. 2017.This uses the Greenstreet et al. 2012 model with 50 million NEOswith absolute magnitudes 13 < H < 29 and the Moving ObjectProcessing System (MOPS, Denneau et al. 2013) for linkages. Theresults are compared with other possible strategies.

Author(s): Kenneth C. Chambers , Eva Lilly (Schunova) ,Martin Todd Dukes , Richard J. WainscoatInstitution(s): 1. University of Hawaii

112.11 – Long-Term Monitoring of 'Active Asteroid'P/2016 G1 (PANSTARRS)We present updated results of repeated monitoring of ‘ActiveAsteroid’ P/2016 G1 (PANSTARRS) using the 0.7-m, f/3.2 JeanneRich Telescope at the Jay Baum Rich Observatory in Frazier Park,CA, as well as the Keck 10-m telescope equipped with the LRISinstrument. The ‘Active Asteroids’ are a strange and newlydiscovered class of small bodies in the Solar System that have theorbital and dynamical properties of asteroids and also thephysical properties of comets; for example, ejection of dust andvolatile materials. P/2016 G1 (PANSTARRS) was detected in 2016April by R. Weryk and R. Wainscoat using the 1.8-mPANSTARRS1 telescope and appears to exhibit activity potentiallydue to catastrophic impact of the main body (Moreno et al. 2016).

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In this work, we have monitored P/2016 G1 (PANSTARRS) fromthe months of April to August 2016 to better understand themechanism and drivers of activity in this Solar System small bodyand detect changes in the appearance form which to form a morecomplete picture of this object.

Author(s): Dave Gerald Milewski , David Jewitt , RobertMichael RichInstitution(s): 1. University of California, Los Angeles (UCLA)

112.12 – Near-Earth Asteroid Follow-upObservations from the Astronomical ResearchInstituteThe Astronomical Research Institute (ARI) operates eighttelescopes ranging in size from 0.41m to 1.3m. These telescopesare dedicated to the astrometric recovery and arc-extension ofNear-Earth Asteroids (NEAs). Four telescopes are located outsideWestfield, Illinois, USA (0.61, 0.76, 0.81, 1.3m) while the otherfour telescopes are at Cerro Tololo Inter-American Observatory(0.41, 0.61, 0.61, 1.0m).

The increase in NEA discovery from PanSTARRS and CatalinaSky Survey continues to escalate the nightly demand for newlydiscovered NEA follow-up. ARI has developed a new protocolwhich allows the discovery rate to increase fivefold without theneed for additional telescopes.

ARI’s new secondary priority is to provide spectra andspectrophotometry observations of the brightest newly discoveredNEAs. Proposed methods and procedures will be discussed sothat other NEA researchers may have access to the results withouta peer-reviewed delay.

Author(s): Tyler R. LinderInstitution(s): 1. Astronomical Research Institute

112.13 – Determining an empirical estimate of the trackinginconsistency component for true astrometricuncertainties

The asteroid community is moving towards the implementationof a new astrometric reporting format. This new format willfinally include of complementary astrometric uncertainties in thereported observations. The availability of uncertainties will allowephemeris predictions and orbit solutions to be constrained withgreater reliability, thereby improving the efficiency of thecommunity's follow-up and recovery efforts.

Our current uncertainty model involves our uncertainties incentroiding on the trailed stars and asteroid and the uncertaintydue to the astrometric solution. The accuracy of our astrometricmeasurements are reliant on how well we can minimise the offsetbetween the spatial and temporal centroids of the stars and theasteroid. This offset is currently unmodelled and can be caused byvariations in the cloud transparency, the seeing and trackinginconsistencies. The magnitude zero point of the image, which isaffected by fluctuating weather conditions and the catalog bias inthe photometric magnitudes, can serve as an indicator of thepresence and thickness of clouds. Through comparison of theastrometric uncertainties to the orbit solution residuals, it wasapparent that a component of the error analysis remainedunaccounted for, as a result of cloud coverage and thickness,

telescope tracking inconsistencies and variable seeing. This workwill attempt to quantify the tracking inconsistency component.We have acquired a rich dataset with the University of Hawaii2.24 metre telescope (UH-88 inch) that is well positioned toconstruct an empirical estimate of the tracking inconsistencycomponent. This work is funded by NASA grant NXX13AI64G.

Author(s): Yudish Ramanjooloo , David J. Tholen , DoraFohring , Zach Claytor , Denise HungInstitution(s): 1. University of Hawaii

112.14 – Introducing ADES: A New IAU AstrometryData Exchange StandardFor several decades, small body astrometry has been exchanged,distributed and archived in the form of 80-column ASCII records.As a replacement for this obsolescent format, we have workedwith a number of members of the community to develop theAstrometric Data Exchange Standard (ADES), which was formallyadopted by IAU Commission 20 in August 2015 at the XXIXGeneral Assembly in Honolulu, Hawaii. The purpose of ADES is to ensure that useful and availableobservational information is submitted, archived, anddisseminated as needed. Availability of more completeinformation will allow orbit computers to process the data morecorrectly, leading to improved accuracy and reliability of orbitalfits. In this way, it will be possible to fully exploit the improvingaccuracy and increasing number of both optical and radarobservations. ADES overcomes several limitations of the previousformat by allowing characterization of astrometric andphotometric errors, adequate precision in time and angle fields,and flexibility and extensibility. To accommodate a diverse base of users, from automated surveysto hands-on follow-up observers, the ADES protocol allows fortwo file formats, eXtensible Markup Language (XML) and Pipe-Separated Values (PSV). Each format carries the sameinformation and simple tools allow users to losslessly transformback and forth between XML and PSV. We have further developed and refined ADES since it was firstannounced in July 2015 [1]. The proposal at that time [2] hasundergone several modest revisions to aid validation and avoidoverloaded fields. We now have validation schema and filetransformation utilities. Suitable example files, test suites, andinput/output libraries in a number of modern programminglanguages are now available. Acknowledgements: Useful feedback during the developmentof ADES has been received from numerous colleagues in thecommunity of observers and orbit specialists working onasteroids comets and planetary satellites. References: [1] Chesley, S.R. (2015) M.P.E.C. 2015-O06. [2]http://minorplanetcenter.net/iau/ info/IAU2015_ADES.pdf

Author(s): Steven R. Chesley , George M Hockney ,Matthew J. HolmanInstitution(s): 1. Harvard-Smithsonian Center forAstrophysics, 2. JPL

113.01 – Modeling the Thermal Interactions ofMeteorites Below the Antarctic IceMeteorites with high specific gravities, such as irons, appear to beunderrepresented in Antarctic collections over the last 40 years.This underrepresentation is in comparison with observedmeteorite falls, which are believed to represent the actualpopulation of meteorites striking Earth. Meteorites on theAntarctic ice sheet absorb solar flux, possibly leading todownward tunneling into the ice, though observations of this in

action are very limited. This descent is counteracted by ice sheetflow supporting the meteorites coupled with ablation nearmountain margins, which helps to force meteorites towards thesurface. Meteorites that both absorb adequate thermal energy andare sufficiently dense may instead reach a shallow equilibriumdepth as downward melting overcomes upward forces during theAntarctic summer. Using a pyronometer, we have measured theincoming solar flux at multiple depths in two deep field sites inAntarctica, the Miller Range and Elephant Moraine. We compare

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these data with laboratory analogues and model the thermal andphysical interactions between a variety of meteorites and theirsurroundings. Our Matlab code model will account for a widerange of parameters used to characterize meteorites in anAntarctic environment. We will present the results of our modelalong with depth estimates for several types of meteorites. Therecovery of an additional population of heavy meteorites wouldincrease our knowledge of the formation and composition of thesolar system.

Author(s): William Jared Oldroyd , Jani Radebaugh ,Denise C. Stephens , Ralph Lorenz , Ralph Harvey , JamesKarnerInstitution(s): 1. Brigham Young University, 2. Case WesternReserve University, 3. Johns Hopkins University Applied PhysicsLaboratory

114.01 – A complete model of the Ceres transientshock: from generation to dissipationIn June 2015, while DAWN was orbiting Ceres at about 10 Ceresradii away, energetic charged particles were recorded that arebest explained by a transient shock, caused by a comet likeinteraction with the solar wind. The required strength of theatmosphere has been evaluated to determine if it is consistentwith previous observations. In this work, we simulate thecomplete atmosphere excitation-interaction-loss process. Wecalculate the total energy input from the associated solarenergetic particle (SEP) event, obtain the model-drivenatmosphere profile with such energy input, and then model theatmosphere-solar wind interaction to determine the 3-D profile of

the shock. With the time varation of the SEP event, we model thedifferent stages of the atmosphere and plasma interaction. In re-constructing the event, we determine the entire lifecycle of thetransient atmosphere produced on an airless body activated by asolar event, and its subsequent loss in its interaction with thesolar wind.

Author(s): Ying-Dong Jia , Michaela Villarreal , Ian Lai ,Christopher T. Russell , Wing-Huen IpInstitution(s): 1. IGPP/UCLA, 2. National Central University

115.02 – Measuring NH and other molecularabundance profiles from 5 microns ground-basedspectroscopy in support of JUNO investigationsWe report on results of an observational campaign to support theJuno mission. At the beginning of 2016, using TEXES (TexasEchelon cross-dispersed Echelle Spectrograph), mounted on theNASA Infrared Telescope Facility (IRTF), we obtained data cubesof Jupiter in the 1930--1943 cm and 2135--2153 cm spectralranges (around 5 μm), which probe the atmosphere in the 1--4bar region, with a spectral resolution of ≈0.3 cm (R≈7000) andan angular resolution of ≈1.5''.

This dataset is analyzed by a code that combines a line-by-lineradiative transfer model with a non-linear optimal estimationinversion method. The inversion retrieves the abundance profilesof NH and PH , which are the main conbtributors at thesewavelengths, as well as the cloud transmittance. This retrieval isperformed over more than one thousand pixels of our data cubes,producing effective maps of the disk, where all the major belts arevisible (NEB, SEB, NTB, STB, NNTB and SSTB).

We will present notably our retrieved NH abundance mapswhich can be compared with the unexpected latitudinaldistribution observed by Juno's MWR (Bolton et al., 2017 and Liet al. 2017), as well as our other species retrieved abundancemaps and discuss on their significance for the understanding ofJupiter's atmospheric dynamics.

References: Bolton, S., et al. (2017), Jupiter’s interior and deep atmosphere:The first close polar pass with the Juno spacecraft, Science,doi:10.1126/science.aal2108, in press. Li, C., A. P. Ingersoll, S. Ewald, F. Oyafuso, and M. Janssen(2017), Jupiter’s global ammonia distribution from inversion ofJuno Microwave Radiometer observations, Geophys. Res. Lett.,doi:10.1002/2017GL073159, in press.

Author(s): Doriann Blain , Thierry Fouchet , Thomas K.Greathouse , Bruno Bézard , Therese Encrenaz , John H. Lacy ,Pierre DrossartInstitution(s): 1. Observatoire de Paris, 2. SWRI, 3. Universityof Texas

115.04 – High-Resolution Observations of Jupiter’sQQO and Mid-Latitude Waves via TEXES/GeminiNorth Observations

In an attempt to further constrain the 3-dimensional structure ofJupiter’s Quasi-Quadrennial Oscillation and mid-latitude waves,we have performed high-spectral and -spatial scan mappingobservations of Jupiter’s mid-latitudes using TEXES, the TexasEchelon cross-dispersed Echelle Spectrograph, mounted on the 8-meter Gemini North Telescope. Observations retrieved on March16 and 20 UT of methane emission features between 1244.5and 1250.5 cm , allow for the retrieval of the verticaltemperature profiles between 10 mbar and 1 μbar. Theobservations taken over the two nights produced nearly completelongitude coverage between +/-45° latitude with 1.4° lat/longresolution at Jupiter’s sub earth point. We will present theobservations, retrieved temperature data cube, andinterpretations of the features observed.

Author(s): Thomas K. Greathouse , Glenn Orton , RichardCosentino , Raul Morales-Juberias , Rohini GilesInstitution(s): 1. Jet Propulsion Laboratory, 2. NASA GoddardSpaceflight Center, 3. New Mexico Institute of Mining andTechnology, 4. Southwest Research Institute

115.05 – Statistical Estimation of Properties andVariations in Jupiter’s Stratospheric Oscillation The Quasi-Quadrennial Oscillation's (QQO) 4 year period inJupiter's atmosphere near 10 hPa was first discovered in 7.8-micron brightness temperature observations from the 1980's and1990's. New observations using the high-spectral resolution TexasEchelon cross-dispersed Echelle Spectrograph (TEXES), mountedon the NASA Infrared Telescope facility (IRTF), havecharacterized the vertical structure of the QQO from spectral dataat 8 microns taken over a complete cycle between January 2012and January 2017. These new observations show the thermaloscillation spans a range of pressures from 2-20 hPa. Aftercombining both data sets, we found the QQO has a largertemperature amplitude in the TEXES spectroscopy than wasmeasured from previous photometric imaging. We also found asmaller QQO period in the TEXES data when compared to theolder IRTF data. The disparities in the observed QQO propertiesare actually consistent with each other when we considereddetails of each observation. We also developed models betweendifferent QQO cycles and found statistical evidence for a 20%change in the QQO's 4 year period at the 10 hPa level.

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Author(s): Richard Cosentino , Amy A. Simon , Thomas K.Greathouse , Leigh Fletcher , Raul Morales-Juberias , Glenn S.Orton , Perianne JohnsonInstitution(s): 1. Goddard Space Flight Center, 2. JetPropulsion Laboratory, 3. New Mexico Institute of Mining andTechnology, 4. Southwest Research Institute, 5. University ofLeicester

115.06 – Studying the Structure of CondensablesJupiter’s 24deg JetSimulations of the atmospheres of Jovian planets can be used tocheck our current understanding of the physics of theiratmospheres. Such studies have been performed in the past, butthe development of cloud microphysics models allows us to gainnew insight in how the clouds form and behave in areas ofinterest. This study conducts high resolution cloudy simulationsof the 24 degree north high speed jet for a period of 200 days. Themodels were created using the Explicit PlanetaryIsentropic_Coordinate (EPIC) general circulation model(Dowling et al 1998, 2006) that includes full hydrological cycle formultiple condensible species (Palotai and dowling 2008, Palotaiet al 2016). This builds off of work presented by our group lastyear at DPS. The simulations were run under various conditionsagain in order to test what parameters led to stable simulations.These results help describe which physical parameters can lead tostable high speed jets and how water and ammonia behave withinthese features. Reference: [1] T. Dowling, A. Fischer, P. Gierasch,J. Harrington, R. Lebeau, and C. Santori. The explicit planetaryisentropic-coordinate (epic) atmospheric model. Icarus, 1998. [2]T. E. Dowling, M. E. Bradley, E. Colon, J. Kramer, R. P. LeBeau,G. C. H. Lee, T. I. Mattox, R. Morales-Juberias, C. J. Palotai, V. k.Parimi, and A. P. Showman. The epic atmospheric model with anisentropic/terrain-following hybrid vertical coordinate. Icarus,182:259–273, may 2006.[3] C. Palotai and T. E. Dowling.Addition of water and ammonia cloud microphysics to the epicmodel. Icarus, 2008.[4] C. J. Palotai, R. P. Le Beau, R. Shankar,A. Flom, J. Lashley, and T. McCabe. A cloud microphysics modelfor the gas giant planets. In AAS/Division for Planetary SciencesMeeting Abstracts, 2016.

Author(s): Abigail Flom , Ramanakumar Sankar , Csaba J.Palotai , Timothy E. DowlingInstitution(s): 1. Florida Institute of Technology, 2. Universityof Louisville

115.08 – Ground-based hyperspectral imaging andanalysis of Jupiter’s atmosphere during the JunoeraThe Juno mission to Jupiter has presented ground-basedobservers with a unique opportunity to collect data while thespacecraft is simultaneously measuring the planet and itsatmosphere. Data collected in conjunction with Junomeasurements have the capability to complement and enhancewavelength regimes already covered by Juno instruments. In order to enrich Juno’s scientific returns in the visible regime,we use the New Mexico State University Acousto-optic ImagingCamera (NAIC) to obtain hyperspectral image cubes of Jupiterfrom 470-950 nm with an average spectral resolution (λ/dλ) of242. We use NAIC with the Apache Point Observatory 3.5-mtelescope to image Jupiter’s atmosphere during Juno’s perijoveflybys. With these timely, high spectral resolution measurements,we can derive the properties of cloud and haze particulates andestimate cloud heights. We present geometrically andphotometrically calibrated spectra of representative regions ofJupiter’s atmosphere to be compared with previous work andlaboratory measurements of candidate chromophore materials.The data we present are from the night of March 26 , 2017,captured during Juno’s 5 perijove flyby. We discuss preliminaryanalyses of these spectra, including implications for future workregarding atmospheric modeling. For the aforementioned observations, NAIC was equipped with athinned, back-illuminated CCD. Because of the narrowbandwidths NAIC’s spectral tuning element produces, this chipdesign resulted in etaloning, or “fringing,” in images at

wavelengths longer than ~720 nm. We discuss our methodologyfor correcting the fringing and the progress of a general-usemodel for correcting fringing in CCDs. Such a model requires theextraction of chip characteristics from monochromatic flats,which can be then be used to model exactly how the interferenceof light inside the chip results in the fringing pattern. Thisartificial fringing image can then be removed from images,thereby correcting the effect. This work is supported by Research Support Agreement 1569980from the Jet Propulsion Laboratory, as a subaward of aNASA/Solar System Observations grant.

Author(s): Emma Dahl , Nancy J. Chanover , David Voelz ,David M. Kuehn , Erandi Wijerathna , Robert Hull , Paul D.Strycker , Kevin H. BainesInstitution(s): 1. Condordia University Wisconson, 2. GarminInternational, 3. NASA/Jet Propulsion Laboratory, 4. NewMexico State University

115.09 – Jupiter's belts and zones: Contradictoryevidence for upwelling and downwelling Early authors (Hess and Panofsky 1951, Ingersoll and Cuzzi 1969,Barcilon and Gierasch 1970) noted that the zonal winds arecyclonic in the belts and anticyclonic in the zones. From thethermal wind equation they concluded that the air below theclouds is colder at the belts and warmer at the zones. Hot airrising and cold air sinking led to the notion of downwelling in thebelts and upwelling in the zones, which agreed with observationsof clear air and low ammonia vapor in the belts and cloudy airand high ammonia vapor in the zones (Gierasch et al. 1986).However, lightning in the belts seemed to contradict that idea,based on the assumption that lightning and convection requireupwelling of moist air from below (Little et al. 1999, Ingersoll etal. 2000). Convergence of the eddy momentum flux on thepoleward sides of the zones (Salyk et al. 2006) supports theinference based on lightning by implying convergence of themeridional flow in the zones. Here we argue that lightning in thebelts does not require upwelling. Instead, there is a threshold formoist convection that is triggered when the thickness of theweather layer drops below a critical value (Li and Ingersoll 2006,Thomson and McIntyre 2016). We also argue that theconvergence of the eddy momentum flux does not requireequatorward flow. Instead, the meridional flow is controlled bythe sign of the potential vorticity (PV) gradient, which issouthward on the equatorward sides of the zones (Ingersoll et al.2017), implying divergence of the meridional flow in the zones.This is a new idea and is based on the observation that thepredicted flat parts of the PV staircase (Dritschel and McIntyre2008), might actually be sloping inward, since the curvature ofthe zonal velocity profile U_yy exceeds beta at the centers of thewestward jets (Ingersoll and Cuzzi 1969, Ingersoll et al. 1981,Limaye et al. 1986, Li et al. 2004, Read et al. 2006). Thesearguments agree with observations of upwelling in the zones, butthey do not explain the near absence of a belt-zone signaturebelow 2-3 bars, as implied by the recent Juno data (Bolton et al.2017, Ingersoll et al. 2017).

Author(s): Andrew P. IngersollInstitution(s): 1. CaltechContributing team(s): Juno Science Team

115.10 – Measuring turbulent cascades in Jupiter'sweather layerJupiter's atmosphere has often been compared with a classicalquasi-two-dimensional, geostrophically turbulent fluid, in whichkinetic energy is transferred upscale, with zonal jets emerging dueto the spherical curvature of the planet. In a new analysis of 2Dwind fields obtained from Cassini cloud images taken duringclosest approach to Jupiter at the time of the December 2000 fly-by, we have determined 2nd and 3rd order structure functionsand spectral transfers of kinetic energy and enstrophy (squaredvorticity) across scales ranging from ~1000 km to the scale of theplanet itself. These confirm the upscale transfer of kinetic energyfrom eddies on scales ≥ 3000 km up to the scales of the zonal jets,

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with ~90% of the energy being transferred into the jetsthemselves, accompanied by downscale transfer of enstrophyfrom all scales. For scales ≤ 3000 km or so, however, kineticenergy is transferred downscale, indicating a strong source ofkinetic energy at a scale ~2000-3000 km, comparable with theinternal Rossby deformation radius. This suggests an importantrole for baroclinic instability in energising Jupiter's turbulentatmosphere.

Author(s): Roland M B Young , Peter L ReadInstitution(s): 1. University of Oxford

115.11 – Disappearance of surface banded structureproduced by thermal convection in a rapidlyrotating thin spherical shellSurface flows of Jupiter and Saturn are characterized by thebroad prograde zonal jets around the equator and the narrowalternating zonal jets in mid- and high-latitudes. The productionand maintenance mechanisms of those surface jets are still indebate.

A distinguished study by Heimpel and Aurnou (2007)demonstrates that a "deep" model, namely, thermal convection ina rotating but thin spherical shell, can produce an equatorialprograde zonal jet and alternating zonal jets in mid- and high-latitudes simultaneously by using Boussinesq fluid. However,they assume eight-fold symmetry in the longitudinal directionand calculate fluid motion only in the one-eighth sector of thewhole spherical shell. Further, since time integration of theirnumerical experiment is so short as 1600 rotation period (0.024viscous diffusion time), their result may not reach statisticallysteady state.

In the present study, we perform long time numerical integrationof thermal convection in the whole thin spherical shell domainwhere the experimental setup is same as that of Heimpel andAurnou (2007). The experiment in the 1/8 sector domain withlongitudinal symmetry is also conducted for comparison.

Time integration were completed until 38000 rotation period forcalculation in the 1/8 sector domain, and 17000 rotation periodfor that in the whole spherical shell. In both cases, equatorialprograde surface zonal jets and alternating banded zonal jetsemerge at certain stages, which seem to be consistent with theresult of Heimpel and Aurnou (2007). However, in the case of thewhole domain calculation, in the mid- and high- latitudinalregions eastward acceleration continues, zonal banded structuresdisappear, and finally, one broad eastward zonal jet appears inmid- and high- latitudes of each hemisphere. It is in contrast tothe result of 1/8 sector domain where alternating jets in mid- andhigh- latitudes are maintained during the integration period.

Reference : Heimpel, M., Aurnou, J. (2007) Icarus, 187, 540--557.

Author(s): Shin-ichi Takehiro , Youhei Sasaki , KeiichiIshioka , Kensuke Nakajima , Masaki Ishiwatari , Yoshi-YukiHayashiInstitution(s): 1. Department of Cosmosciences, HokkaidoUniversity, 2. Department of Earth and Planetary Sciences,Kyoto University, 3. Department of Earth and PlanetarySciences, Kyushu University, 4. Department of Mathematics,Kyoto University, 5. Department of Planetology, KobeUniversity, 6. Research Institute for Mathematical Sciences,Kyoto University

115.12 – Three-wave resonant interactions in two-dimensional turbulence on a rotating sphereRossby waves are indispensable to discuss flow dynamics underdifferential rotation, and in particular, three-wave resonantnonlinear interactions of Rossby waves are often considered toplay an important roles in realizing characteristic features inRossby wave turbulences. In fact, at high rotation rates, it hasbeen mathematically shown that the dynamics of two-dimensional Rossby wave turbulence on a beta plane within

certain finite time is totally governed by three-wave resonantnonlinear interactions of Rossby waves (Yamada and Yoneda,Physica D, 2013). Also, for example, Kartashova and L’vov (Phys.Rev. Lett., 2007) considered clusters of resonant Rossby waves,defined by connected triangles by nonzero energy transfer, anddiscussed dynamics of atmosphere. However, what kind of roles the three-wave resonant nonlinearinteractions of Rossby waves possess and how they function intwo-dimensional turbulences are not at all clear yet, sinceresonant and non-resonant interactions are always mixed anddetermine the flow dynamics together in systems havingmoderate rotation rates, and it is extremely difficult tonumerically extract the effect of there-wave resonant interactionsthere. Therefore in this research, based on the result of Yamada andYoneda (Physica D, 2013), we have considered two-dimensionalNavier-Stokes flows on rapidly rotating spheres, in order tonumerically investigate how the three-wave resonant nonlinearinteractions of Rossby waves are working in the system. Then itwas found that large-scale structures, i.e. zonal flows, cannot beformed only by three-wave resonant interactions. It was alsofound that, the existence of resonant Rossby waves having no netenergy transfer by resonant interactions should not be neglectedin considering the dynamics of total resonant Rossby wavesdynamics, and as a result, the group of resonant Rossby wavescannot be divided into clusters in terms of connected triangles bynonzero energy transfer.

Author(s): Kiori Obuse , Michio YamadaInstitution(s): 1. Kyoto University, 2. Okayama University

115.15 – Polarization of Hazes and Aurorae onJupiterOur solar system planets show a large variety of atmosphericpolarization properties, from the thick, highly polarizing haze onTitan and the poles of Jupiter, Rayleigh scattering by moleculeson Uranus and Neptune, to clouds in the equatorial region ofJupiter or on Venus. Changes in the clouds/thermal filed can bebrought about by endogenic dynamical processes such merger ofvortices; global, planetary scale upheavals, and external factorssuch as celestial collisions (such as D/Shoemaker-Levy 9 impactwith Jupiter in 1994, etc.). Although the range of phase anglesavailable from Earth for outer planets is restricted to a narrowrange, limb polarization measurements provide constraints onthe polarimetric properties. For example, at the equator, much ofthe observed reflected radiation is due to the presence of cloudsand therefore, low polarization. Polar asymmetry exists betweenthe two poles, while the planetary disk is unpolarized. Jupiter isknown to exhibit a strong polar limb polarization and a lowequatorial limb polarization due to the presence of haze particlesand Rayleigh scattering at the poles. In contrast, at the equator,the concentration of particulates in the high atmosphere mightchange, changing the polarimetric signature and aurorae at bothpoles. The polarimetric maps, in conjunction with thermal mapsand albedo maps, can provide constraints on modeling efforts tounderstand the nature of the aerosols/hazes in Jovianatmosphere. With Jupiter experiencing morphological changes atmany latitudes, we have initiated a polarimetric observingcampaign of Jupiter, in conjunction with The PACA Project. WithNASA/Juno mission in a 53-day orbit around Jupiter, and recentoutbreaks in the atmosphere, changes in the polarimetricsignature will provide insight to the changes occurring in theatmosphere. Some of our observations are acquired by a team ofprofessional/amateur planetary imagers astronomers based inthe U.K., Australia and Europe. France. Details/results of thesestudies will be presented to optimize the observing strategy ofplanetary atmospheres and their role in the atmosphericretrievals and the next stage of polarimetric exploration ofJupiter.

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Author(s): Padma A. Yanamandra-Fisher , Will McLeanInstitution(s): 1. Armagh Observatory, 2. Space ScienceInstituteContributing team(s): PACA_Jupiter

115.16 – Last Looks at the Eye of Saturn byCassini/VIMS During the Grand FinaleA lasting remnant of the Great Storm that erupted on Saturn inlate 2010 has been a massive lone anticyclone persisting to thepresent time in a NH -dry 5-µm-bright “desert” zone that spansthe entire Saturnian globe at 34 N. We have been observing thisoval storm with Cassini/VIMS since 2011 and, in 2017, as Cassiniperforms its Grand Finale orbits close to the planet, havecaptured it at our highest resolution since January 2012 at 260km/pixel – enough to resolve spiral structure inside the oval at 5µm. The spot drifts latitudinally in Saturn’s zonal currents: it wasat 35.9 planetocentric latitude in May 2011, wanderednorthward to 37.8 in 2012, hovered near 37 through 2013,meandered as far south as 36.5 in 2014, drifted northward to37 in 2015, and then returned back to about 36.3 in 2016,where it remains presently. It has also periodically bumped upagainst the dark band above it, spinning off material in 2013,2015, and 2017. We measured a prograde zonal drift speed of 22m/s in 2012, increasing as much as 60% through 2013, thenrelaxing to a more moderate 15 m/s in 2014 and 2015. It slowedconsiderably in 2016 to 4.7 m/s and is currently drifting slightlyfaster at 8.5 m/s. The spot has varied in size over time as it spins,spanning 4.9 x 3.2 in 2011, elongating to 7.3 x 2.9 by 2013,contracting to 5.5 x 2.9 in 2014, enlarging again to 9 x 4 in2015, and contracting currently to 7.0 x 3.2 (6100 x 3200 km)in 2017, symmetrically oval in shape. It has varied in terms ofcloudiness, being 90% 5-µm dark (obscured) in 2011, whereas by2013 it was mostly bright (clear) with a thin dark edge. It was90% dark in 2015, and in 2017 is about 65% obscured, with abright central eye. Utilizing night observations to isolate thermalflux, we have found that the mean 5-µm flux coming from theanticyclone has diminished steadily by about 75% since 2013. Theentire storm latitude of ~34 N itself has remained persistently 5-µm bright since 2011, but is slowly dimming as it fills in. Aquantitative record of the evolution of this feature from formationto last looks during the Grand Finale passes by Cassini/VIMS willbe presented.

Author(s): Thomas W. Momary , Kevin H. Baines , SarahBadman , Robert H Brown , Bonnie J. Buratti , Roger NelsonClark , Philip D. Nicholson , Christophe SotinInstitution(s): 1. Cornell University, 2. Jet PropulsionLaboratory/CalTech, 3. Lancaster University, 4. PlanetaryScience Institute, 5. SSEC/University of Wisconsin-Madison, 6.University of Arizona

115.17 – Uranus' post-equinox north polarbrightening characterized with 2013 and 2016 IRTFSpeX observationSince its 2007 equinox, the atmosphere of Uranus, as seen in thenear infrared (~800-1600 nm) has exhibited dramatic changes.Its southern polar cap, prominent prior to equinox, has faded anda similar polar cap has begun developing in the north.Karkoschka and Tomasko (2009, Icarus 202:287) demonstratedthat in 2002 the south polar region, brighter than lower latituderegions when viewed at wavelengths of intermediate methaneabsorption, was depleted in methane compared to darker regions.Tice et al. (2013, Icarus 223:684) and Sromovsky et al. (2014,Icarus 238:137) concluded that the northern polar regions weresimilarly depleted. The north polar region (45N-90N) hascontinued to brighten; modeling of 2015 HST STIS observations(Fry et al. 2016, AAS DPS #48 421.03) suggested that thelatitudinal methane distribution has remained essentiallyunchanged since equinox, but brightening from 2012 to 2015 wasdue to changes in aerosol scattering. We acquired 0.8-2.5 μmSpeX spectra in 2013 (central meridian) and 2016 (pole-alignedspectra at 0, 0.4, 0.8, and 1.2 arcsec. distant from the CM) undersimilar seeing conditions (0.4-0.5 arcsec.). The SpeX wavelengthrange gives us an additional wavelength region where H

absorption competes with or exceeds CH absorption, and awider wavelength range to characterize aerosol particleproperties, compared to STIS. The multiple spectra in 2016 allowus to compare specific latitudes to 2013 at the same view angles(and to use center-to-limb constraints in modeling 2016 spectra).We will present observations, reduction procedures, comparative(2013 vs 2016) modeling of latitudinal methane abundance andvertical aerosol profiles, and compare to 2012/2015 STIS analysis.Preliminary analysis shows that lower latitudes (~30N) have notchanged since 2013, but higher latitudes (~70N) have undergonecontinued significant brightening at pseudo-continuumwavelengths dominated by both H (1080 nm, up ~50%) andCH (1290 nm, also up ~50%) absorption , indicating a change inscattering properties. This work is supported by NASA Solar System Observations grantNNA16AH99G.

Author(s): Patrick M. Fry , Lawrence A. SromovskyInstitution(s): 1. Univ. of Wisconsin

115.18 – Waves, Plumes and Bubbles from JupiterComet ImpactsWe present results from our numerical simulations of joviancomet impacts that investigate various phases of the Shoemaker-Levy 9 (SL9) and the 2009 impacts into Jupiter's atmosphere.Our work includes a linked series of observationally constrained,three-dimensional radiative-hydrodynamic simulations to modelthe impact, plume blowout, plume flight/splash, and wave-propagation phases of those impact events. Studying these stagesusing a single model is challenging because the spatial andtemporal scales and the temperature range of those phases maydiffer by orders of magnitudes (Harrington et al. 2004). In oursimulations we model subsequent phases starting with theinterpolation of the results of previous simulations onto a new,larger grid that is optimized for capturing all key physics of therelevant phenomena while maintaining computational efficiency.This enables us to carry out end-to-end simulations that requireno ad-hoc initial conditions. In this work, we focus on the wavesgenerated by various phenomena during the impact event andstudy the temporal evolution of their position and speed. Inparticular, we investigate the shocks generated by the impactorduring atmospheric entry, the expansion of the ejected plume andthe ascent of the hot bubble of material from terminal depth.These results are compared to the observed characteristics of theexpanding SL9 rings (Hammel et al. 1995). Additionally, wepresent results from our sensitivity tests that focus on studyingthe differences in the ejecta plume generation using variousimpactor parameters (e.g., impact angle, impactor size, material,etc.). These simulations are used to explain various phenomenarelated to the SL9 event and to constrain the characteristics of theunknown 2009 impactor body. This research was supported byNational Science Foundation Grant AST-1627409.

Author(s): Csaba J. Palotai , Ramanakumar Sankar , TylerMcCabe , Donald KorycanskyInstitution(s): 1. Florida Institute of Technology, 2. Universityof California, Santa Cruz

115.19 – Studies of Dark Spots and TheirCompanion Clouds on the Ice Giant PlanetsObservations of ice giant planets in our Solar System have shownseveral large-scale dark spots with varying lifespans. Some ofthese features were directly observed, others were diagnosed fromtheir orographic companion clouds. Historically, numericalsimulations have been able to model certain characteristics ofthese storms such as the shape variability of the Neptune GreatDark Spot (GDS-89) (Deng and Le Beau, 2006), but have notbeen able to match observed drift rates and lifespans using thestandard zonal wind profiles (Hammel et al. 2009). Commonamongst these studies has been the lack of condensable species inthe atmosphere and an explicit treatment of cloud microphysics.Yet, observations show that dark spots can affect neighboringcloud features, such as in the case of bright companion clouds or

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the “Berg” on Uranus. An analysis of the cloud structure istherefore required to gain a better understanding of theunderlying atmospheric physics and dynamics of these vortices. For our simulations, we use the Explicit Planetary IsentropicCoordinate (EPIC) general circulation model (Dowling et al. 1998,2006) and adapt its jovian cloud microphysics module whichsuccessfully reproduced the cloud structure of jovian storms, suchas the Great Red Spot and the Oval BA (Palotai and Dowling2008, Palotai et al. 2014). EPIC was recently updated to accountfor the condensation of methane and hydrogen sulfide (Palotai etal. 2016), which allows us to account for both the high-altitudemethane ice-cloud and the deep atmosphere hydrogen sulfide ice-cloud layers. In this work, we simulate large-scale vortices on Uranus andNeptune with varying cloud microphysical parameters such as thedeep abundance and the ambient supersaturation. We examinethe effect of cloud formation on their lifespan and drift rates tobetter understand the underlying processes which drive thesestorms.

Author(s): Sakhee Bhure , Ramanakumar Sankar , NathanHadland , Csaba J. Palotai , Raymond P. Le Beau , NikkoKoutasInstitution(s): 1. Florida Institute of Technology, 2. St. LouisUniversity

115.20 – Photochemistry in Saturn’s Ring-Shadowed Atmosphere: Photochemistry and HazeObservationsAfter 13 years of observing Saturn, Cassini would have endednearly a half Saturnian year. During this epoch, the ring shadowhas moved from covering much of the northern hemisphere tocovering a large swath southern hemisphere. The net effect is thatthe intensity of both ultraviolet and visible sunlight penetratingthrough the rings to any particular latitude will vary dependingon both Saturn’s axis relative to the Sun and the optical thicknessof each ring system. In essence, the rings act like semi-transparent venetian blinds. This effect magnifies the effect dueto axial tilt alone and acts to turn off photochemistry and hazegeneration. This effect is seen in both the presence of a bluishRayleigh-scattering atmosphere in 2004 in the northernhemisphere and color change to blue in the northern hemisphere. Previous work examined the variation of the solar flux as afunction of solar inclination, i.e. for each 7.25-year season atSaturn. We report on the impact of the oscillating ring shadow, inaddition to variation due to axial tilt, on photolysis andproduction rates of hydrocarbons and phosphine in Saturn’sstratosphere and upper troposphere. The impact of theseproduction and loss rates on the abundance of long-livedphotochemical products leading to haze formation are explored.We assess their impact on a disequilibrium species whosepresence in the upper troposphere can be used as a tracer ofconvective processes in the deeper atmosphere. We will also present our ongoing analysis of Cassini’s CIRS, UVIS,and VIMS datasets that provide an estimate of the evolving hazecontent. In particular, we will examine how the region insideSaturn’s famous hexagonal jet stream changes over time from arelatively clear atmosphere to a hazy one. We also explore howthe hexagon acts like a barrier to transport, isolating Saturn’snorth polar region from outside influences of photochemically-generated molecules and haze.

The research described in this paper was carried out in part at theJet Propulsion Laboratory, California Institute of Technology,under a contract with the National Aeronautics and SpaceAdministration. Copyright 2017 California Institute ofTechnology. Government sponsorship is acknowledged.

Author(s): Scott G. Edgington , Sushil K. Atreya , Kevin H.Baines , Robert A West , Gordon L. Bjoraker , Leigh Fletcher ,Thomas W. Momary , Eric WilsonInstitution(s): 1. Jet Propulsion Laboratoy/California Institueof Technology, 2. NASA Goddard Space Flight Center, 3. SpaceEnvironment Technologies, 4. University of Leicester, 5.University of MichiganContributing team(s): CIRS, ISS, UVIS, VIMS

115.21 – Resistive Heating and Ion Drag in Saturn'sThermosphere One of the most puzzling observations of the jovian planets is thatthe thermospheres of Jupiter, Saturn, Uranus and Neptune are allseveral times hotter than solar heating can account for (Strobeland Smith 1973; Yelle and Miller 2004; Muller-Wodarg et al.2006). On Saturn, resistive heating appears sufficient to explainthese temperatures in auroral regions, but the particularmechanism(s) responsible for heating the lower latitudes remainsunclear. The most commonly proposed heating mechanisms arebreaking gravity waves and auroral heating at the poles followedby redistribution of energy to mid-and low latitudes. Both of theseenergy sources are potentially important but also come withsignificant problems. Wave heating would have to be continuousand global to produce consistently elevated temperatures and thestrong Coriolis forces coupled with polar ion drag appear tohinder redistribution of auroral energy (see Strobel et al. 2016 forreview). Here we explore an alternative: wind-driven electrodynamics thatcan alter circulation and produce substantial heating outside ofthe auroral region. Smith (2013) showed this in-situ mechanismto be potentially significant in Jupiter’s thermosphere. We present new results from an axisymmetric, steady-state modelthat calculates resistive (Joule) heating rates through rigoroussolutions of the electrodynamic equations for the coupled neutralatmosphere and ionosphere of Saturn. At present, we assume adipole magnetic field and neglect any contributions from themagnetosphere. We use ion mixing ratios from the model of Kimet al. (2014) and the observed temperature-pressure profile fromKoskinen et al. (2015) to calculate the generalized conductivitytensor as described by Koskinen et al. (2014). We calculate thecurrent density under the assumption that it has no divergenceand use it to calculate the resistive heating rates and ion drag. Ourresults suggest that resistive heating and ion drag at low latitudeslikely play a significant role in the dynamics and energetics ofSaturn's low-latitude thermosphere.

Author(s): Jess William Vriesema , Tommi Koskinen ,Roger V YelleInstitution(s): 1. University of Arizona

115.22 – Jupiter's Equatorially AntisymmetricGravitational Field and its Interior DynamicsThe equatorially anti-symmetric gravitational field of Jupiter isnearly unaffected by its rotational distortion and, hence, it provides a direct window into the equatorially anti-symmetric fluid motion taking place in Jupiter's interior. We present a new accurate approach, based on the thermal-gravitational wind equation in spherical geometry (a two-dimensional kernel integral equation with the Green'sfunction in its integrand), for estimating thelocation/structure/amplitude of the Jovian equatoriallyantisymmetric zonal flow of Jupiter via its equatorially anti-symmetric gravitational field and understanding the dynamics ofJupiter's deep interior. The mathematical and numericaldifficulties in computing the equatorially anti-symmetricgravitational field are discussed.

Author(s): Keke Zhang , Dali Kong , Gerald Schubert , JohnD. AndersonInstitution(s): 1. JPL, 2. SHAO, 3. UCLA, 4. University pfExeter, UK

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115.23 – Multiple Excitation Regimes in Jupiter’sPolar AuroraeSince the Voyager epoch, it has been known that thethermospheres of all the outer planets are heated to atemperature over 3 times higher than can be explained by solarEUV (Yelle & Miller 2000). The dominant heat source is still anopen question. Without this knowledge, one cannot understandthe structure, energy balance, and seasonal evolution of outerplanet upper atmospheres. Majeed et al. (2009) suggest that themain ionospheric heat source driving the thermospheric flow athigh Jovian latitudes is Joule currents resulting from thefrictional motion of the ions relative to the neutrals, while particleprecipitation dominates the heating of the auroral ovals atexospheric altitudes. However, since the diffuse emission interiorto the oval is not directly connected to a source in themagnetosphere, and vice versa, separate processes may drive theheating in the auroral oval and the zone within. Because thelatter’s open field lines expose it to “space weather”, it is subjectto thermospheric heating by the solar wind, coronal massejections, and reconnection in the Jovian magnetotail.

H plays an important role in the cooling and stabilizing ofhydrogenic planetary thermospheres (Miller et al. 2000). ForJupiter's hot upper atmosphere, above the homopause at ~1 µbar,H appears to be the dominant coolant, so that the local heatingrate may be estimated by measuring the H emission flux.Consequently, the morphology and spectrum of the H emissionflux should be heavily influenced by, and so provide the clearestsignature of, the unknown heating process. A study of Jupiter’sH emission may therefore help to isolate and constrain thatdominant process. Towards that end, we surveyed Jupiter'snorthern and southern auroral zones near pre-oppositionquadrature on May 11 and 12, 2009, by obtaining emission linespectra between 3-4 microns at Keck II with NIRSPEC. Thesouthern spectra resolve at least three contrarily excited Hemission spectra simultaneously, suggesting at least three distinctexcitation processes operating within Jupiter's polar aurorae. Theemission morphology cannot be explained by the observinggeometry nor viewing aspect.

Author(s): Laurence M. TraftonInstitution(s): 1. Univ. of Texas, Austin

115.24 – Cassini UVIS Auroral Observations in2016 and 2017In 2016 and 2017, the Cassini Saturn orbiter executed a finalseries of high-inclination, low-periapsis orbits ideal for studies ofSaturn's polar regions. The Cassini Ultraviolet ImagingSpectrograph (UVIS) obtained an extensive set of auroral images,some at the highest spatial resolution obtained during Cassini'slong orbital mission (2004-2017). In some cases, two or threespacecraft slews at right angles to the long slit of the spectrographwere required to cover the entire auroral region to form auroralimages. We will present selected images from this set showingnarrow arcs of emission, more diffuse auroral emissions, multipleauroral arcs in a single image, discrete spots of emission, smallscale vortices, large-scale spiral forms, and parallel linear featuresthat appear to cross in places like twisted wires. Some shorterfeatures are transverse to the main auroral arcs, like barbs on awire. UVIS observations were in some cases simultaneous withauroral observations from the Cassini Imaging Science Subsystem(ISS) the Cassini Visual and Infrared Mapping Spectrometer(VIMS), and the Hubble Space Telescope Space TelescopeImaging Spectrograph (STIS) that will also be presented.

Author(s): Wayne R. Pryor , Larry W Esposito , AlainJouchoux , Aikaterini Radioti , Denis Grodent , JacquesGustin , Jean-Claude Gerard , Laurent Lamy , Sarah Badman ,Ulyana A. DyudinaInstitution(s): 1. Caltech, 2. Central Arizona College, 3.Lancaster University, 4. LASP, University of Colorado, 5.Observatoire de Paris- Section de Meudon, 6. University of LiegeContributing team(s): Cassini UVIS Team, Cassini VIMSTeam, Cassini ISS Team, HST Saturn Auroral Team

115.25 – What can numerical simulations say aboutJupiter’s deep, long-lived anticyclones?If Jupiter’s long-lived anticyclones, GRS being the mostprominent example, are indeed deep as indicated, the study oftheir dynamics would be much more difficult than if they wereshallow. A shallow phenomenon limited to the troposphere can bemodeled by general circulation models like those used in weatherprediction for Earth’s atmosphere, as the layer overall isconvectively stable (hydrostatic approximation can be applied)and the time scales (advection and radiation) are relatively short.If the dynamics involve the deep convective envelop below, thetime scales for thermal relaxation and spin-up would be manyorders of magnitudes longer. At the same time, the requirementsfor handling stratification, turbulence, compressibility, fastrotation, spatial resolution, and numerical stability conditions arenot forgiving. Currently, numerical studies of long-lived vorticesgenerated in convection zone are limited to ‘numericalexperiments’ having internal energy fluxes many orders ofmagnitudes greater than that of Jupiter (for faster thermal anddynamical relaxation). Though these experiments cannot predictquantitative values for direct observational comparison, theirinformation on the spatial distributions and connections amongvelocity, temperature, pressure etc. can tell a lot about what adeep-seated model can predict or describe. We are going topresent the results of our latest fully compressible, large-eddy-simulation model for generation of long-lived anticyclones indeep convection zone. The high turbulence and complex internalstructures of the vortices can naturally be explained. Oneprediction for observation is: While fluctuations of temperatureand vertical velocity dissipate relative fast with height in thetroposphere (stable region), the horizontal velocities (vorticalmotions) drop much slower; they hardly decrease by a factor oftwo in four pressure scale heights in the overshoot region.Acknowledgement: This research is supported by FDCT of Macau039/2013/A2 and 080/2015/A3.

Author(s): Kwing L ChanInstitution(s): 1. Macau University of Science and Technology

115.26 – 3D General Circulation Model of theMiddle Atmosphere of JupiterThe characteristics of Jupiter’s large-scale stratosphericcirculation remain largely unknown. Detailed distributions oftemperature and photochemical species have been provided byrecent observations [1], but have not yet been accuratelyreproduced by middle atmosphere general circulation models(GCM). Jupiter’s stratosphere and upper troposphere areinfluenced by radiative forcing from solar insolation and infraredcooling from hydrogen and hydrocarbons, as well as wavespropagating from the underlying troposphere [2]. The relativesignificance of radiative and mechanical forcing on stratosphericcirculation is still being debated [3]. Here we present a 3D GCMof Jupiter’s atmosphere with a correlated-k radiative transferscheme. The simulation results are compared with observations.We analyze the impact of model parameters on the stratospherictemperature distribution and dynamical features. Finally, wediscuss future tracer transport and gravity wave parameterizationschemes that may be able to accurately simulate the middleatmosphere dynamics of Jupiter and other giant planets. [1] Kunde et al. 2004, Science 305, 1582. [2] Zhang et al. 2013a, EGU General Assembly, EGU2013-5797-2. [3] Conrath 1990, Icarus, 83, 255-281.

Author(s): Nicholas Gerard Zube , Xi Zhang , Cheng Li ,Tianhao LeInstitution(s): 1. California Institute of Technology, 2.University of California - Santa Cruz

115.27 – Dynamics and Characteristics of Saturn’s RibbonWave Using Cassini Images We present an analysis of Saturn’s Ribbon feature using Cassini

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ISS images captured using the CB2, MT2, and MT3 filters in thenear-infrared. First observed by Voyager 1 and 2, the Ribbon is aplanetary-scale meandering dark line around 47°Nplanetographic latitude. During the Voyager flybys, themeandering dark line followed the peak in an eastwardatmospheric jet and marked the boundary between cyclonic andanticyclonic shear zones. The shape of the line rapidly changed inthe timescale of tens of hours, likely following the shifting path ofthe meandering jet. During the Cassini era, the 47°N jet has alsoexhibited wavy cloud morphology; however, unlike previousanalyses of Voyager and Hubble images which showed the Ribbonat the center of the eastward jet, we observe that, between 2007and 2010, the most prominent wave was located at the northernflank of the jet at 50.7°N. We analyze the wave-like morphologyobserved in the Cassini images. Our analysis covers the Ribbon'stemporal evolution on the scale of hours to years. Using map-projected mosaics, we used both automated and manual methodsto map the Ribbon’s latitudinal position as a function of longitudeand calculate the wave’s Fourier power spectrum. These powerspectra show several distinct spectral peaks that evolve over time.We also examine the temporal evolution of the region over severalSaturnian rotations to determine the dispersion and the phasespeed of the waves. Our work is supported by NASA CDAP grantNNX15AD3392.

Author(s): Jacob L Gunnarson , Kunio M. Sayanagi , JohnJ. Blalock , Angelina Gallego , Andrew P. Ingersoll , Ulyana A.Dyudina , Shawn Ewald , Ryan M. McCabe , Justin GarlandInstitution(s): 1. California Institute of Technology, 2.Hampton University

115.28 – Infrared rotational light curves on Jupiterinduced by wave activities and cloud patterns and implications on brown dwarfsMany brown dwarfs exhibit infrared rotational light curves withamplitude varying from a few percent to twenty percent (Artigau et al. 2009, ApJ, 701, 1534;Radigan et al. 2012, ApJ, 750, 105). Recently, it was claimed that weather patterns, especiallyplanetary-scale waves in the belts and cloud spots, are responsible for the light curves and

their evolutions on brown dwarfs (Apai et al. 2017, Science, 357, 683). Here we present a clearrelationship between the direct IR emission maps and light curves of Jupiter at multiplewavelengths, which might be similar with that on cold brown dwarfs. Based on infrared disk maps fromSubaru/COMICS and VLT/VISIR, we constructed full maps of Jupiter and rotational light curves atdifferent wavelengths in the thermal infrared. We discovered a strong relationship betweenthe light curves and weather patterns on Jupiter. The light curves also exhibit strong multi-bands phase shifts and temporal variations, similar to that detected on brown dwarfs. Togetherwith the spectra from TEXES/IRTF, our observations further provide detailedinformation of the spatial variations of temperature, ammonia clouds and aerosols in the troposphere ofJupiter (Fletcher et al. 2016, Icarus, 2016 128) and their influences on the shapes of the lightcurves. We conclude that wave activities in Jupiter’s belts (Fletcher et al. 2017, GRL, 44, 7140),cloud holes, and long-lived vortices such as the Great Red Spot and ovals control the shapesof IR light curves and multi- wavelength phase shifts on Jupiter. Our finding supports thehypothesis that observed light curves on brown dwarfs are induced by planetary-scale waves andcloud spots.

Author(s): Huazhi Ge , Xi Zhang , Leigh Fletcher , Glenn S.Orton , James Andrew Sinclair , Joshua Fernandes, , Thomas W.Momary , Ari Warren , Yasumasa Kasaba , Takao M. Sato ,Takuya FujiyoshiInstitution(s): 1. Jet Propulsion Laboratory, 2. SubaruTelescope/National Astronomical Observatory of Japan, 3.Tohoku University, 4. University of California Santa Cruz, 5.University of Leicester

116.01 – 2017 Solar Eclipse in Hopkinsville, KY:E/PO Feedback from Two VenuesHopkinsville, Kentucky was the largest town in the region ofmaximum totality for the 21 August 2017 Solar Eclipse, andtransformed itself into “Eclipseville” with extensive mediaattention. Here we give 2 on-the-ground reports on education andpublic outreach (E/PO) activities from Hopkinsville. One of us(TD) partnered with the Kentucky Division of EmergencyManagement (KYEM) and was in the Hopkinsville VIP area, andthe other (GC) led a series of E/PO events at the HopkinsvilleChurch of Ss. Peter & Paul, which were nationally advertised indiocesan newspapers. In addition, both of us were interviewedextensively by local and national media before the event. Pre-event planning by KYEM extended for over a year, andculminated in a 6-hour, 12 July 2017 Tabletop Exercise (TTX) runby FEMA. This face-to-face workshop drew over 250 participants,including Kentucky’s Lt. Governor, health and public safetyofficials at the state-level and from the 21 Kentucky counties inthe path of totality, mayors and convention-bureau officials fromthe affected KY towns, the KY National Guard, the U.S. Depts. ofHealth and Human Services, Homeland Security, andTransportation, the National Weather Service, the U.S. CoastGuard for riverboat traffic, the U.S. Forest Service, the AmericanRed Cross, representatives from ATT, Verizon and Sprint, andrepresentatives from local universities—it was the largest TTX inKentucky’s history. Here, we report on E/PO feedback weassembled from the VIP and parochial sites, including the mostfrequently asked questions, which types of answers seemed to bemost effective, and how actual events compared with the large-crowd preparations and planning.

Author(s): Timothy E. Dowling , Guy ConsolmagnoInstitution(s): 1. Univ. of Louisville, 2. Vatican Obs.

116.03 – Planetary Science Educational Materialsfor Out-of-School Time Educators Planetary Learning that Advances the Nexus of Engineering,Technology, and Science (PLANETS) is a five-year NASA-funded(NNX16AC53A) interdisciplinary and cross-institutionalpartnership to develop and disseminate STEM out-of-school time(OST) curricular and professional development units thatintegrate planetary science, technology, and engineering. TheCenter for Science Teaching and Learning (CSTL) andDepartment of Physics and Astronomy (P&A) at NorthernArizona University, the U.S. Geological Survey AstrogeologyScience Center (USGS ASC), and the Museum of Science Boston(MoS) are partners in developing, piloting, and researching theimpact of three out-of-school time units. Planetary scientists atUSGS ASC and P&A have developed two units for middle gradesyouth and one for upper elementary aged youth. The two middleschool units focus on greywater recycling and remote sensing ofplanetary surfaces while the elementary unit centers on exploringspace hazards. All units are designed for small teams of ~4 youthto work together to investigate materials, engineer tools to assistin the explorations, and utilize what they have learned to solve aproblem. Youth participate in a final share-out with adults andother youth of what they learned and their solution to theproblem. Curriculum pilot testing of the two middle school unitshas begun with out-of-school time educators. A needs assessmenthas been conducted nationwide among educators and evaluationof the curriculum units is being conducted by CSTL during thepilot testing. Based on data analysis, the project is developing andtesting four tiers of professional support for OST educators. Tier 1

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meets the immediate needs of OST educators to teach curriculumand include how-to videos and other direct support materials.Tier 2 provides additional content and pedagogical knowledgeand includes short content videos designed to specifically addressthe content of the curriculum. Tier 3 elaborates on best practicesin education and gives guidance on methods, for example, todevelop cultural relevancy for underrepresented students. Tier 4helps make connections to other NASA or educational productsthat support STEM learning in out of school settings.

Author(s): Nadine G. Barlow , Joelle G ClarkInstitution(s): 1. Northern Arizona Univ.

116.05 – CosmoQuest – Mapping Surface FeaturesAcross the Inner Solar SystemThe CosmoQuest Virtual Research Facility allows researchscientists to work together with citizen scientists in ‘big data’investigations. Some research requires the examination of vastnumbers of images – partnering with engaged and trained citizenscientists allows for that research to be completed in a thoroughand timely manner. The techniques used by CosmoQuest tocollect impact crater data have been validated to ensurerobustness (Robbins et al., 2014), and include software tools thataccurately identify crater clusters, and multiple crateridentifications. CosmoQuest has current or up-and-comingprojects that span much of the inner solar system. “MoonMappers” gives the public a chance to learn about the importanceof cratered surfaces, and investigate factors that effect theidentification and measurement of impact craters such asincidence angle. In the “Mars Mappers” program citizens mapsmall craters in valley networks. These will be used to estimatetimes of ancient water flow. In “Mercury Mappers” the publiclearns about other issues related to crater counting, such assecondaries. On Mercury, secondaries appear to dominate countsup to 10km. By mapping these craters, we will be able to betterunderstand the maximum diameter of secondaries relative to theparent primary. The public encounters Vesta in “Vesta Mappers,”a project that contributes data to the overall crater countingefforts on that body. Asteroid investigations do not end there –the OSIRIS-REx team is collaborating with CosmoQuest to createa science campaign to generate boulder and crater countingdatasets of the asteroid Bennu. This “Bennu Mappers” project willinform the final selection of the sample return site. The Earth isthe target for the “Image Detective” project, which uses the 2million images returned from crewed space flight. These imagesare rich in information about our changing Earth, as well asphenomena like aurora. Citizens tag these images with meta-datasuch as visible features and the center point location of imagery toenable scientists and the public to more easily search for imageryof interest in NASA’s online database of astronaut imagery ofEarth.

Author(s): Jennifer A. Grier , Matthew Richardson ,Pamela L. Gay , Cory Lehan , Ryan Owens , Stuart J. Robbins ,Daniella DellaGiustina , Carina Bennett , Susan Runco , PaigeGraffInstitution(s): 1. Astronomical Society of the Pacific, 2. Jacobsat NASA Johnson Space Center, 3. NASA Johnson Space Center,4. Planetary Science Institute, 5. Southwest Research Institute, 6.University of Arizona, Lunar and Planetary Laboratory

116.06 – An Inaugural Girl Scout DestinationsAstronomy CampThe University of Arizona (UA) conducted its first teenage GirlScout Destinations Astronomy Camp. This program waspreceded by 24 Leadership Workshops for Adult Girl ScoutLeaders, initially supported by EPO funding from NIRCam forJWST. For five days in late June, 24 girls (ages 13-17 years)attended from 16 states. The Camp was led by UA astronomersand long-term educators. Representing Girl Scouts of the USA(GSUSA) were a husband/wife amateur astronomer team who areSOFIA Airborne Astronomy and NASA Solar SystemAmbassadors. Other leaders included a Stanford undergraduateengineering student who is a lifelong Girl Scout and Gold Award

recipient and a recent UA Master’s degree science journalist. TheCamp is a residential, hands-on “immersion” adventure inscientific exploration using telescopes in southern Arizona’sCatalina Mountains near Tucson. Under uniquely dark skies girlsbecome real astronomers, operating telescopes (small and large)and associated technologies, interacting with scientists, obtainingimages and quantitative data, investigating their own questions,and most importantly having fun actually doing science andbuilding observing equipment. Girls achieve a basicunderstanding of celestial objects, how and why they move, andtheir historical significance, leading to an authenticunderstanding of science, research, and engineering. Girls canlead these activities back home in their own troops and councils,encouraging others to consider STEM field careers. Theseprograms are supported by a 5-year NASA CollaborativeAgreement, Reaching for the Stars: NASA Science for Girl Scouts(www.seti.org/GirlScoutStars), through the SETI Institute incollaboration with the UA, GSUSA, Girl Scouts of NorthernCalifornia, the Astronomical Society of the Pacific, and AriesScientific, Inc. The Girl Scout Destinations Astronomy Campaligns with the GSUSA Journey: It’s Your Planet-Love It! andintroduces the girls to some of the activities being developed bythe Girl Scout Stars team for GSUSA’s new space science badgesfor all Girl Scout levels as a part of Reaching for the Stars.Reaching for the Stars: NASA Science for Girl Scouts issupported by NASA SMD’s Education Cooperative Agreement #NNX16AB90.

Author(s): Larry A. Lebofsky , Donald W. McCarthy , JoeWright , Rita Wright , Mikayla Mace , Charmayne FloydInstitution(s): 1. Arizona. Daily Star, 2. Stanford University, 3.University of Arizona, 4. Warkoczewski Public Observatory

116.07 – Science and Exploration in the Classroom& Beyond: An Interdisciplinary STEAM CurriculumDeveloped by SSERVI Educators & ScientistsThrough NASA’s Solar System Exploration Research VirtualInstitute (SSERVI), the Center for Lunar and Asteroid SurfaceScience (CLASS) and the SSERVI Evolution and Environment ofExploration Destinations (SEEED) nodes have developed aninterdisciplinary formal and informal hands-on curriculum tobring the excitement of space exploration directly to the students. With a focus on exploring asteroids, this 5-year effort has infusedart with traditional STEM practices (creating STEAM) andprovides teachers with learning materials to incorporate art,social studies, English language arts, and other courses into thelesson plans. The formal curricula being developed follows NextGeneration Standards and incorporates effective and engagingpedagogical strategies, such as problem-based learning (PBL),design thinking, and document based questions, using authenticdata and articles, some of which are produced by the SSERVIscientists. From the materials developed for the formal educationcomponent, we have built up a collection of informal activities ofvarying lengths (minutes to weeks-long programs) to be used bymuseums, girl and boy scouts, science camps, etc. The curricula are being developed by formal and informaleducators, artists, storytellers, and scientists. The continualfeedback between the educators, artists, and scientists enables theprogram to evolve and mature such that the material will beaccessible to the students without losing scientific merit. Onlinecomponents will allow students to interact with SSERVI scientistsand will ultimately infuse ongoing, exciting research into thestudent’s lessons. Our Education & Public Engagement (EPE) program makes astrong effort to make educational material accessible to alllearners, including those with visual or hearing impairments.Specific activities have been included or independently developedto give all students an opportunity to experience the excitement ofthe universe.

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Author(s): Tracy M Becker , Cassandra Runyon , HallCynthia , Daniel BrittInstitution(s): 1. College of Charleston, 2. Southwest ResearchInstitute, 3. University of Central FloridaContributing team(s): Tracy Becker

116.08 – DPS Planetary Science GraduatePrograms Database for Students and AdvisorsPlanetary science is a topic that covers an extremely diverse set ofdisciplines; planetary scientists are typically housed in adepartments spanning a wide range of disciplines. As such it isdifficult for undergraduate students to find programs that willgive them a degree and research experience in our field asDepartment of Planetary Science is a rare sighting, indeed. Notonly can this overwhelm even the most determined student, it caneven be difficult for many undergraduate advisers.

Because of this, the DPS Education committee decided severalyears ago that it should have an online resource that could helpundergraduate students find graduate programs that could leadto a PhD with a focus in planetary science. It began in 2013 as astatic page of information and evolved from there to a database-driven web site. Visitors can browse the entire list of programs orcreate a subset listing based on several filters. The site should beof use not only to undergraduates looking for programs, but alsofor advisers looking to help their students decide on their futureplans.

We present here a walk-through of the basic features as well assome usage statistics from the collected web site analytics. We askfor community feedback on additional features to make thesystem more usable for them. We also call upon those mentoringand advising undergraduates to use this resource, and forprogram admission chairs to continue to review their entry andprovide us with the most up-to-date information.

The URL for our site is http://dps.aas.org/education/graduate-schools.

Author(s): David R. Klassen , Anthony Roman , Bonnie K.MeinkeInstitution(s): 1. Rowan Univ., 2. Space Telescope ScienceInstitute

116.09 – Las Cumbres Observatory Partners WithLocal Museums In “Experience The Eclipse”Community ProgramLas Cumbres Observatory (LCO) in Goleta, California, togetherwith the Santa Barbara Museum of Natural History (SBMNH)and the Wolf Museum of Exploration & Innovation (MOXI) puttogether a community program called “Experience the Eclipse”for the month of August.

The greater Santa Barbara community includes over 200,000people and the city is known for its vibrant cultural life. Eventsfeaturing science, physics, and astronomy are very popular. In2016, Javier Rivera, the Astronomy Program Manager of theSBMNH, and Ron Skinner, the Director of Education at MOXI,met with LCO to discuss planning a month of activities to educatethe public about the Great American Eclipse. The vision was tocapitalize on the strength of each organization and to shareinformation and events.

The events included daily planetarium shows and open houses atthe observatory of the SBMNH. All three organizations gaveparties at public venues with presentations by astronomers.Together the group purchased 6,000 pairs of eclipse viewerglasses and they shared the responsibility of distributing these tolocal schools and community groups. A master calendar of theevents was published in local press outlets and a documentdescribing the eclipse and safe viewing practices was distributedwidely. Preparation of these materials was a joint effort amongthe three institutions.

“Experience the Eclipse” was a great success. The open houses atSBMNH were well attended and all public events sold out veryquickly. On August 21, the SBMNH presented a live feed of theeclipse taken from their own observatory. We will present photos and videos from these events, along withdata on the attendance and quotes from enthusiastic participants.

Author(s): Sarah Greenstreet , Sandy Seale , Javier Rivera ,Ron SkinnerInstitution(s): 1. Las Cumbres Observatory, 2. MOXI TheWorld Museum of Exploration & Innovation, 3. Santa BarbaraMuseum of Natural History

116.10 – Eclipse 2017: Through the Eyes of NASAThe August 21, 2017 total solar eclipse across America was, by allaccounts, the biggest science education program ever carried outby NASA, significantly larger than the Curiosity Mars landing andthe New Horizons Pluto flyby. Initial accounting estimates overtwo billion people reached and website hits exceeding five billion.The NASA Science Mission Directorate spent over two yearsplanning and developing this enormous public educationprogram, establishing over 30 official NASA sites along the pathof totality, providing imagery from 11 NASA space assets, twohigh altitude aircraft, and over 50 high altitude balloons. Inaddition, a special four focal plane ground based solar telescopewas developed in partnership with Lunt Solar Systems thatobserved and processed the eclipse in 6K resolution. NASA EDGEand NASA TV broadcasts during the entirity of totality across thecountry reached hundreds of millions, world wide.This talk willdiscuss NASA's strategy, results, and lessons learned; and previewsome of the big events we plan to feature in the near future.

Author(s): Louis MayoInstitution(s): 1. NASA's GSFCContributing team(s): NASA Heliophysics EducationConsortium

116.11 – Techniques for Engaging the Public inPlanetary SciencePublic audiences are often curious about planetary science.Scientists and education and public engagement specialists canleverage this interest to build scientific literacy. This poster willhighlight research-based techniques the authors have tested witha variety of audiences, and are disseminating to planetaryscientists through trainings. Techniques include: Make it personal. Audiences are interested in personal stories,which can capture the excitement, joy, and challenges thatplanetary scientists experience in their research. Audiences canlearn more about the nature of science by meeting planetaryscientists and hearing personal stories about their motivations,interests, and how they conduct research. Share relevant connections. Most audiences have very limitedunderstanding of the solar system and the features andcompositions of planetary bodies, but they enjoy learning aboutthose objects they can see at night and factors that connect totheir culture or local community. Demonstrate concepts. Some concepts can be clarified withanalogies, but others can be demonstrated or modeled withmaterials. Demonstrations that are messy, loud, or that yieldsurprising results are particularly good at capturing an audience’sattention, but if they don’t directly relate to the key concept, theycan serve as a distraction. Give them a role. Audience participation is an importantengagement technique. In a presentation, scientists can invite theaudience to respond to questions, pause to share their thoughtswith a neighbor, or vote on an answer. Audiences can respondphysically to prompts, raising hands, pointing, or clapping, oreven moving to different locations in the room. Enable the audience to conduct an activity. People learn best bydoing and by teaching others; simple hands-on activities in whichthe audience is discovering something themselves can beextremely effective at engaging audiences.

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This poster will cite examples of each technique, resources thatcan help planetary scientists develop presentations,demonstrations, and activities for public engagement events, andthe research that supports the use of these techniques.

Author(s): Christine Shupla , Andrew Shaner , AmandaSmith HacklerInstitution(s): 1. Lunar and Planetary Institute

117.01 – Evidence of Collisional Histories ofAsteroids, Comets and Meteorites: Comparisonswith Shocked MineralsEvidence of the collisional history of comets and asteroids hasbeen emerging from analyses of cometary forsterite and enstatitereturned from Comet Wild 2 by the Stardust mission (Keller etal.Geochim. Cosmochim. Acta 72, 2008; Tomeoka et al. MAPS43, 2008; Jacobs et al. MAPS 44, 2009). Likewise, shockmetamorphism is observed in many meteoritic forsterites andenstatites (McCausland et al. AGU, 2010), suggesting similarcollisional histories for asteroids. Further exploration of theeffects of collisions is slated for the upcoming Asteroid ImpactMission/Double Asteroid Redirection Test (AIM/DART) mission,expected for launch in 2020. DART will impact Didymoon, thecompanion of the larger 65803 Didymos (1996 G2) asteroid, andAIM will use its instrumentation to characterize the impact.

A suite of relevant impact experiments have been carried out inthe Experimental Impact Laboratory at the NASA Johnson SpaceCenter at velocities ranging from ~2.0 – 2.8 km s andtemperatures from 25°C to -100°C. Targets include a suite ofminerals typically found in cometary dust and in asteroids andmeteorites: Mg-rich forsterite (olivine), enstatite(orthopyroxene), diopside (clinopyroxene), magnesite (Mg-richcarbonate), and serpentine (phyllosilicate). TransmissionElectron Microscope (TEM) imaging indicates evidence of shocksimilar to that seen in forsterite and enstatite from Comet Wild 2.Fourier Transform Infrared (FTIR) Spectroscopy will also be usedfor comparisons with meteorite spectra. A quantitative analysis ofthe shock pressures required to induce planar dislocations andspectral effects with respect to wavelength will also be presented.

Funding provided by the NASA PG&G grant 09-PGG09-0115,NSF grant AST-1010012. Special thanks to NASA EIL staff, F.Cardenas and R. Montes.

Author(s): Susan M. Lederer , Elizabeth Jensen , DouglasSmith , Michael Fane , Akbar Whizin , Zoe A. Landsman , DianeH. Wooden , Sean S. Lindsay , Mark Cintala , Lindsay P.Keller , Michael ZolenskyInstitution(s): 1. Cal State Univ SB, 2. NASA Ames ResearchCenter, 3. NASA Johnson Space Center, 4. Planetary ScienceInstitute, 5. Univ. Central Florida, 6. Univ. Tenn. Knoxville

117.02 – The asteroid 2014 JO25The asteroid 2014 JO25 was discovered by A. D. Grauer at the Mt.Lemmon Survey on May 2014, and Joe Masiero usedobservations from the NEOWISE in 2014 to estimate a diameterof 650 meters [1]. However, using the radio telescope at Arecibo-Puerto Rico, astronomers obtained radar images on April 17-2017and Edgar Rivera Valentín (scientist at Arecibo) said: “We found2014 JO25 is a contact binary asteroid, two space rocks that wereoriginally separate bodies, and each segment is about 640 metersand 670 meters, for a total of about 1.3 km long. Its rotation is of3.5 hours” [2]. This asteroid flew past Earth on April 19 at adistance of about 4.6 lunar distances from the Earth. This was theclosest approach by an asteroid since 4179 Toutatis. Toutatis flewpast Earth on September 2004 at a distance of about 4 lunardistances from the Earth [3]. In April 12-2020 the asteroid will beat a minimum possible distance of 0.1617280 A.U from Earth [4].From our observatory, located in Pasto-Colombia, we obtained alot of pictures. Our data was published by the Minor PlanetCenter [5] and also appears at the web page of NEODyS [6].Astrometry and photometry were carried out, and we calculatedthe orbital elements. We obtained the following orbitalparameters: eccentricity=0.88454+/-0.00152, semi-major axis=2.0573+/- 0.0216 A.U, orbital inclination=25.22+/-0.10 deg,

longitude of the ascending node =30.6530+/-0.0032 deg,argument of perihelion=49.586+/-0.012 deg, mean motion =0.33402+/-0.00527 deg/d, periheliondistance=0.237524+/-0.000644 A.U, apheliondistance=3.8770+/-0.0449 A.U, absolute magnitude =18.1. Theparameters were calculated based on 164 observations. Dates:2017 April: 22 to 24 with mean residual=0.22 arcseconds.Theasteroid has an orbital period of 2.95 years. [1]https://echo.jpl.nasa.gov/asteroids/2014JO25/2014JO25_planning[2] http://earthsky.org/astronomy-essentials/large-asteroid-2014-jo25-close-april-19-2017-how-to-see [3] https://cneos.jpl.nasa.gov/news/news196.html [4] http://newton.dm.unipi.it/neodys/index.php?pc=1.1.8&n=2014JO25 [5] http://www.minorplanetcenter.net/db_search/show_object?utf8=%E2%9C%93&object_id=2014+JO25 [6] http://newton.dm.unipi.it/neodys/index.php?pc=2.1.2&o=H78&ab=8

Author(s): Alberto Vodniza , Mario PereiraInstitution(s): 1. University of Narino Observatory

117.03 – Binary asteroid orbit evolution due toprimary shape deformationAbout a sixth of all small asteroid systems are binary [Margot etal., Science, 2002]. Many binary asteroids consist of an elongatedsynchronous secondary body orbiting a fast-rotating spheroidalprimary body with ridges on its equator. The primary in suchsystems has experienced a long-term spin-up due to the YORPeffect [Vokrouhlick'y et al., Asteroid IV, 2015]. This spin-upprocess can make the primary reach its spin barrier inducingshape deformation processes that ease the structural conditionfor failure inside the primary [e.g., Holsapple, Icarus, 2010].Earlier works have shown that structural heterogeneities in theprimary such as the shape and density distribution induceasymmetric deformation [Sánchez and Scheeres, Icarus, 2016].Here, we investigate how asymmetric shape deformation in theprimary affects the mutual motion of a binary system. We use adynamics model for an irregularly shaped binary system thataccounts for possible deformation of the primary [Hirabayashi etal., LPSC, 2017]. In this model, we consider asymmetricdeformation that occurs based on structural failure in the primaryand thus it modifies the location of the center of mass of thesystem. Using 1999 KW4 as an example, we study a hypotheticalcase in which the primary is initially identical to the current shape[Ostro et al., Science, 2006] with an aspect ratio (AR) of 0.83 andthen suddenly changes its shape to an AR of 0.76. The resultsshow that the asymmetric deformation process and the shift ofthe center of mass excite the eccentricity of the mutual orbit.Considering that the original mutual orbit has an eccentricity of0.0004, after the primary shape change the eccentricity reachesvalues up to 0.15. Also, since the gravity field is modified afterdeformation, the secondary’s spin is desynchronized from themutual orbit. Since synchronicity is a requirement for the binaryYORP (BYORP) effect, which modifies the semi-major axis ofbinary asteroids, a primary shape change temporarily pauses theBYORP effect, in effect lengthening the effective BYORPtimescale.

Author(s): Masatoshi Hirabayashi , Seth A. Jacobson ,Alex DavisInstitution(s): 1. Auburn University, 2. NorthwesternUniversity, 3. University of Colorado Boulder

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117.04 – First results from the rapid-responsespectrophotometric characterization of Near-Earthobjects using RATIRWe are carrying out a program to obtain rapid-responsespectrophotometric characterization of newly discovered NearEarth Objects. Here we present a detailed analysis of the r-idistribution of 87 small (~30-800 m) NEOs observed with theRATIR instrument on the 1.5-m telescope on San Pedro Martir,Mexico. The observations are made in queue mode and the dataprocessing is carried out autonomously. By the use of statisticaltechniques, including Monte Carlo simulations, we find S and Ctype asteroids to be equally frequent, which is in agreement withour previous study (Mommertet al. , 2016). This work is part of acollaboration in which we will characterize hundreds of NEOsthat are generally too faint for other characterization techniques(down to V~21). This work is supported by funding from NASA'sSolar System Observations program.

Author(s): Samuel Navarro-Meza , Michael Mommert ,David E. Trilling , Robert Jedicke , Nathaniel R. Butler ,Mauricio Reyes-Ruiz , Bárbara Pichardo , Tim S. AxelrodInstitution(s): 1. Arizona State University, 2. NorthernArizona University, 3. Universidad Nacional Autónoma deMéxico, 4. Universidad Nacional Autónoma de México, 5.University of Arizona, 6. University of Hawaii

117.05 – Asteroid (367943) 2012 DA14 Flyby SpinState AnalysisOn February 15, 2013 asteroid 2012 DA14 experienced anextremely close Earth encounter, passing within 27700 kmaltitude. This flyby gave observers the chance to directly detectflyby-induced changes to the asteroid’s spin state and physicalproperties. The strongest shape and spin state constraints wereprovided by Goldstone delay-Doppler radar and visible-wavelength photometry taken after closest approach. These dataindicated a roughly 40 m x 20 m object in non-principal axisrotation. NPA states are described by two fundamental periods.Pφ is the average precession period of the long/short axis aboutthe angular momentum vector and Pψ is the rotation periodabout the long/short axis.

WindowCLEAN (Belton & Gandhi 1988) power spectrum analysisof the post flyby light curve showed three prominent frequencies,two of which were 1:2 multiples of each other. Mueller et al.(2002) suggest peaks with this relationship are 1/Pφ and 2/Pφ,implying that Pφ = 6.35 hr. Likely values for Pψ were then 8.72,13.95, or 23.39 hr. These Pφ,Pψ pairs yielded six candidate spinstates in total, one LAM and one SAM per pair.

Second to fourth order, two-dimensional Fourier series fits to thelight curve were best for periods of 6.359 and 8.724 hr. The twoother candidate pairs were also in the top ten fits. Inertiaconstraints of a roughly 2:1 uniform density ellipsoid eliminatedtwo of the three SAM states. Using JPL Horizons ephemeridesand Lambertian ellipsoids, simulated light curves were generated.The simulated and observed power spectra were then comparedfor all angular momentum poles and reasonable ellipsoidelongations. Only the Pφ = 6.359 hr and Pψ = 8.724 hr LAM stateproduced light curves consistent with the observed frequencystructure. All other states were clearly incompatible. With twowell-fitting poles found, phasing the initial attitude and angularvelocity yielded plausible matches to the observed light curve.Neglecting gravitational torques, neither pole agreed with theobserved pre-flyby light curve, suggesting that the asteroid’s spinstate changed during the encounter, consistent with numericalsimulation predictions. The consistency between the pre-flybyobservations and simulated states will be discussed.

Author(s): Conor Benson , Daniel J. Scheeres , NicholasMoskovitzInstitution(s): 1. Lowell Observatory, 2. University ofColorado Boulder

117.06 – An empirical examination ofWISE/NEOWISE asteroid analysis and resultsObservations made by the WISE space telescope and subsequentanalysis by the NEOWISE project represent the largest corpus ofasteroid data to date, describing the diameter, albedo, and otherproperties of the ~164,000 asteroids in the collection. I present acritical reanalysis of the WISE observational data, and NEOWISEresults published in numerous papers and in the JPL PlanetaryData System (PDS). This analysis reveals shortcomings and a lackof clarity, both in the original analysis and in the presentation ofresults. The procedures used to generate NEOWISE results fallshort of established thermal modelling standards. Rather thanusing a uniform protocol, 10 modelling methods were applied to12 combinations of WISE band data. Over half the NEOWISEresults are based on a single band of data. Most NEOWISE curvefits are poor quality, frequently missing many or all the datapoints. About 30% of the single-band results miss all the data;43% of the results derived from the most common multiple-bandcombinations miss all the data in at least one band. TheNEOWISE data processing procedures rely on inconsistentassumptions, and introduce bias by systematically discardingmuch of the original data. I show that error estimates for theWISE observational data have a true uncertainty factor of ~1.2 to1.9 times larger than previously described, and that the errorestimates do not fit a normal distribution. These issues call intoquestion the validity of the NEOWISE Monte-Carlo erroranalysis. Comparing published NEOWISE diameters to publishedestimates using radar, occultation, or spacecraft measurements(ROS) reveals 150 for which the NEOWISE diameters were copiedexactly from the ROS source. My findings show that the accuracyof diameter estimates for NEOWISE results depend heavily onthe choice of data bands and model. Systematic errors in thediameter estimates are much larger than previously described.Systematic errors for diameters in the PDS range from −3% to+27%. Random errors range from −14% to +19% when using allfour WISE bands, and from −45% to +74% in cases using only theW2 band. The results presented here show that much workremains to be done towards understanding asteroid data fromWISE/NEOWISE.

Author(s): Nathan MyhrvoldInstitution(s): 1. Intellectual Ventures

117.07 – Recent Advances and Achievements at TheCatalina Sky SurveyThe Catalina Sky Survey (CSS) is a NASA-funded project fullydedicated to discover and track near-Earth objects (NEOs). Sinceits founding nearly 20 years ago CSS remains at the forefront ofNEO surveys, and recent improvements in both instrumentationand software have increased both survey productivity and dataquality. In 2016 new large-format (10K x 10K) cameras wereinstalled on both CSS survey telescopes, the 1.5-m reflector andthe 0.7-m Schmidt, increasing the field of view, and hence nightlysky coverage by 4x and 2.4x respectively. The new cameras,coupled with improvements in the reduction and detectionpipelines, and revised sky-coverage strategies have yielded adramatic upward trend of NEO discovery rates. CSS has alsodeveloped a custom adaptive queue manager for scheduling NEOfollow-up astrometry using a remotely operated and recentlyrenovated 1-m Cassegrain reflector telescope, improvements thathave increased the production of follow-up astrometry for newlydiscovered NEOs and arc extensions for previously discoveredobjects by CSS and other surveys. Additionally, reprocessing ofarchival CSS data (which includes some 46 million individualastrometric measurements) through the new reduction anddetection pipeline will allow for improved orbit determinationsand increased arc extensions for hundreds of thousands ofasteroids. Reprocessed data will soon feed into a new publicarchive of CSS images and catalog data products made availablethrough NASA’s Planetary Data System (PDS). For the future,CSS is working towards improved NEO follow-up capabilitiesthrough a combination of access to larger telescopes, instrumentupgrades and follow-up scheduling tools.

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Author(s): Gregory J Leonard , Eric J. Christensen , CarsonFuls , Alex Gibbs , Al Grauer , Jess A Johnson , RichardKowalski , Stephen M. Larson , Rose Matheny , Rob Seaman ,Frank ShellyInstitution(s): 1. University of Arizona

117.08 – PRIMitive Asteroids Spectroscopic Survey– PRIMASS: Current StatusPrimitive asteroids contain the most pristine material that gavebirth to the rocky planets. Interest in spectral data from primitiveasteroids that could be the source of the primitive near-Earthasteroids (NEAs) has increased in anticipation of the two sample-return missions that will reach their targets in the next four yearsand bring samples to the Earth within five years. Concurrently,the discovery of water ice on the surfaces of two primitiveasteroids (24 Themis and 65 Cybele) placed the focus on theouter-belt (orbits with semi-major axis larger than 2.82 AU),where more asteroids could harbor water ice on, or below thesurface. In 2010 we started a survey, called the PRIMitive AsteroidsSpectroscopic Survey (PRIMASS), to collect spectra of primitiveasteroids all through the Solar System. Up to now, PRIMASSlibrary (PRIMASS-L) contains more than 530 spectra (0.4 - 2.5μm) of primitive asteroids (> 90% of the asteroids had nospectroscopic data before) in the inner and outer belt. The aim ofthis survey is to provide the community with a comprehensivecollection of data that enable us to study the surface compositionof primitive asteroids by means of visible and near-infraredspectroscopy. Our plans for the close future include making PRIMASS-Lpublicly available in proper timing to be used by the teams of theOSIRIS-REx (NASA) and Hayabusa 2 (JAXA) missions. Thesemissions will characterize two primitive near-Earth asteroids indetail, and the Earth-based libraries, as PRIMASS-L, willestablish the broader framework and maximize the value of thespacecraft results. PRIMASS-L will also serve as a quality-checkdatabase for the Gaia spectroscopic products that will bepublished in its final release, by the end of the nominal mission in2019. In parallel, we plan to continue observing at least for four moresemesters (up to semester 2019A). After almost 10 years of dataacquisition, the PRIMASS database will contain about 700spectra of primitive asteroids in the inner and outer belt. In this work, we present the current state of the PRIMASS survey,and we include major results from the data already analyzed.Finally, we will draft the plans for the future.

Author(s): Noemí Pinilla-Alonso , Julia de León , DavidMorate , Mario de Prá , Vania Lorenzi , Javier Licandro ,Humberto Campins , Victor Ali-LagoaInstitution(s): 1. Florida Space Institute - UCF, 2. FundaciónGalileo Galilei - INAF, 3. Instituto Astrofísico de Canarias, 4.Max Planck Institute for Extraterrestrial Physics, 5.Observatório Nacional, 6. University Central Florida (UCF)

117.09 – LSST Data Products and Tools for SolarSystem ScienceThe Large Synoptic Survey Telescope (LSST; http://lsst.org) willbe an 8-meter, wide-field, ground-based telescope that will surveyhalf the sky every few nights in six optical bands from 320 to 1050nm. It is currently being constructed at Cerro Pachon, Chile, withfirst light expected in 2020 and start of survey operations in2022.

The LSST is expected to make a significant contribution to thestudy of the Solar System, delivering a billion highly preciseobservations of millions of Solar System objects (5mmagphotometry and 10mas astrometry, per observation, on the brightend). Current estimates show yields ranging from ~100,000 newdiscoveries of nearby NEOs (Jones et al. 2017), to 5.5 million forthe main belt, and ~40,000 for KBO populations (Ivezic et al2008).

To enable Solar System science, the LSST will employ a suite of

specialized software tools and generate Solar System-specific dataproducts. These are designed to enable both detection (rapididentification and alerting, and orbit determination) andcharacterization (delivering information such as color andvariability). Solar System processing will occur on three distinctcadences. In near real-time, trailed moving objects will beidentified and alerts sent to the community within minutes ofobservation. These will be a part of LSST’s alert stream, with flagsset to denote they are trailed (Juric et al. 2016). At the end of eachnight of observing, a next generation Moving Object ProcessingSoftware (MOPS) will be utilized to identify, link, compute orbits,and perform precovery for new asteroid detections. This willresult in an updated orbit catalog, published daily. In addition toorbital solutions, this catalog will include covariances anduncertainty estimates, absolute magnitude and slope parameterestimates, quality metrics, and other useful information (Juric etal. 2013). Finally, all LSST data will be reprocessed on an annualcadence, to derive better astrometric and photometric solutionsand recompute improved orbit solutions. All these data will bemade available to the U.S. and Chilean communities, and LSST’sinternational contributors.

Author(s): Mario Juric , R. Jones , Joachim Moeyens , ZeljkoIvezic , Colin SlaterInstitution(s): 1. University of WashingtonContributing team(s): LSST Data Management Team

117.10 – NEOWISE Reactivation Mission YearThree: Asteroid Diameters and AlbedosThe Near-Earth Object Wide-field Infrared Survey Explorer(NEOWISE) reactivation mission has completed its third year ofsurveying the sky in the thermal infrared for near-Earth asteroidsand comets. NEOWISE collects simultaneous observations at 3.4um and 4.6 um of Solar System objects passing through its field ofregard. These data allow for the determination of total thermalemission from bodies in the inner Solar System, and thus thesizes of these objects. We present thermal model fits of asteroiddiameters for 170 NEOs and 6110 MBAs detected during the thirdyear of the survey, as well as the associated optical geometricalbedos. We also compare our results with previous thermalmodel results from NEOWISE for overlapping sample sets, aswell as diameters determined through other independentmethods, and find that our diameter measurements for NEOsagree to within 26% (1-sigma) of previously measured values.Diameters for the MBAs are within 17% (1-sigma). This brings thetotal number of unique near-Earth objects characterized by theNEOWISE survey to 541, surpassing the number observed duringthe fully cryogenic mission in 2010.

Author(s): Joseph R. Masiero , Carrie Nugent , Amy K.Mainzer , Edward L. Wright , James M Bauer , Roc M. Cutri ,Tommy Grav , Emily A. Kramer , Sarah M. SonnettInstitution(s): 1. IPAC/Caltech, 2. NASA JPL/Caltech, 3. PSI,4. UCLA, 5. University of Maryland

117.11 – Asteroid astrometry with Gaia: stellaroccultations and beyondThe first data release of star astrometry by Gaia (Sept. 2016) hasgiven an anticipation of the mission capabilities. By providingpositions with uncertainties at the level of few milli-arcsec (mas)a new frame to calibrate ground-based observations hasimmediately become available, thus disclosing a new possibility ofexploitation for archive data. We will discuss, in particular, thenew role of stellar occulations. Successful observations of occultations have been used in the pastto provide accurate shape and size of the targets and to calibrateother size determination methods. Now, a new possibility ofexploitation exists, as occultation astrometry provides thepossibility of measuring precise asteroid position, at the level ofGaia accuracy. This approach will have an increasing impact, alsothanks to the much improved prediction accuracy that Gaia isgoing to provide, for smaller asteroids and fainter target stars. The scientific goals of improving asteroid astrometry are multiple.For instance, reaching sensitivity to Yarkovsky drift in the Main

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Belt might become possible, by occultation astrometry performedon smaller asteroids, thanks to future Gaia predictions. The second data release (April 2018) will also contain astrometryof asteroids observed directly by Gaia. The properties of this newdata set, that will permit direct orbit improvement, will beillustrated.

Author(s): Paolo Tanga , Federica Spoto , Daniel Hestroffer ,Martin Altmann , Sebastien Bouquillon , Josselin DesmarsInstitution(s): 1. Observatoire de La Côte D'Azur, 2.Observatoire de Paris, 3. Zentrum für Astronomie derUniversität Heidelberg, ARII

118.01 – Comparison of the Cloud MorphologySpatial Structure Between Jupiter and SaturnUsing JunoCam and Cassini ISSWe present an analysis of the spatial-scales contained in the cloudmorphology of Jupiter’s southern high latitudes using imagescaptured by JunoCam in 2016 and 2017, and compare them tothose on Saturn using images captured using the Imaging ScienceSubsystem (ISS) on board the Cassini orbiter. For Jupiter, thecharacteristic spatial scale of cloud morphology as a function oflatitude is calculated from images taken in three visual (600-800,500-600, 420-520 nm) bands and a near-infrared (880- 900 nm)band. In particular, we analyze the transition from the bandedstructure characteristic of Jupiter’s mid-latitudes to the chaoticstructure of the polar region. We apply similar analysis to Saturnusing images captured using Cassini ISS. In contrast to Jupiter,Saturn maintains its zonally organized cloud morphology fromlow latitudes up to the poles, culminating in the cyclonic polarvortices centered at each of the poles. By quantifying thedifferences in the spatial scales contained in the cloudmorphology, our analysis will shed light on the processes thatcontrol the banded structures on Jupiter and Saturn. Our workhas been supported by the following grants: NASA PATMNNX14AK07G, NASA MUREP NNX15AQ03A, and NSF AAG1212216.

Author(s): Justin Garland , Kunio M. Sayanagi , John J.Blalock , Jacob Gunnarson , Ryan M. McCabe , AngelinaGallego , Candice Hansen , Glenn S. OrtonInstitution(s): 1. Hampton University, 2. Jet PropulsionLaboratory, 3. Planetary Science Institute

118.02 – The ammonia absorption behavior onJupiter during 2005-2015V.G.Tejfel, V.D.Vdovichenko, A.M.Karimov, P.G.Lysenko, ,G.A.Kirienko, , V.A.Filippov, G.A.Kharitonova, A.S. Khozhenetz

Fessenkov Astrophysical Institute, Almaty, Kazakhstan

We measured the intensity of the 645 and 787 nm NHabsorption bands in five latitudinal belts of Jupiter (STrZ, SEB,EZ, NEB and NTrZ) during almost full period of its revolutionaround the Sun: from 2005 to 2015. The variations in theequivalent widths of the bands were investigated. Thepermanently lowered intensity of the 787 nm NH band in NEB isconfirmed. There are also some systematic differences inlatitudinal and temporal variations between the 645 and 787 nmammonia bands. The equivalent width of the 787 nm NH bandwas averaged for all years of observations. Its maximum (W =18.95 ± 0.75 A) corresponds to EZ, its minimum (W = 15.82 ±0.68 A) corresponds to NEB. The 645 nm NH band shows themaximum in SEB (W = 6.78 ± 0.45 A), and the minimum in NTrZ(W = 5.38 ± 0.36 A). The weakened ammonia absorption is alsoobserved in the Great Red Spot. However, this is due to theincreased density of the clouds inside the Spot storm, but not todecreased gaseous ammonia abundance, in contrast to NEB. Thebrightness temperature of GRS in the infrared and millimeterranges of thermal radiation is lower, in contrast to NEB, where anincreased brightness temperature is observed. The enhancedcloud density may explain also a pretty high brightness of GRSobserved in strong methane absorption bands such as the 887 nmCH band and more long waved ones.

Author(s): Victor G. TejfelInstitution(s): 1. Fessenkov Astrophysical InstituteContributing team(s): V.G.Tejfel, V.D.Vdovichenko,A.M.Karimov, P.G.Lysenko, , G.A.Kirienko, , V.A.Filippov,G.A.Kharitonova, A.S. Khozhenetz

118.03 – Utilizing Neural Networks in the Retrievalof Jovian Constituent Profiles Using Data from theJuno MWRThe Juno Microwave Radiometer (MWR) has six channelsranging from 1.36-50 cm and has the ability to peer deep into theJovian atmosphere. A minimization algorithm utilizing surrogatemodels has been developed and implemented to performretrievals for Jovian constituent profiles using Juno MWR data.An artifical neural network algorithm is used as the surrogate forthe Juno Atmospheric Microwave Radiative Transfer (JAMRT)model in this minimization. The neural network is trained bysimulating emissions at the six wavelengths computed usingJAMRT. By exploiting the speed of this surrogate model,retrievals for Jovian constituents profiles, such as ammonia andwater vapor, can be rapidly and accurately performed. Retrievedabundance profiles for the first six perijoves during which theJuno MWR was operational will be presented. This work was supported by NASA Contract NNM06AA75C fromthe Marshall Space Flight Center supporting the Juno MissionScience team, under Subcontract 699054X from the SouthwestResearch Institute.

Author(s): Amadeo Bellotti , Paul G SteffesInstitution(s): 1. Georgia Institute of Technology

118.04 – Tracing 3D flows in Jupiter's Atmosphere:Multispectral Observations in February 2017We will present results from near-simultaneous observations inthree very different wavelength ranges, tracing both horizontaland vertical motions. The combined dataset will provide acoherent picture of the flow within discrete features such as 5-micron hot spots. The observations taken together can betterconstrain models of atmospheric flow, compared to the Galileoera, where some wavelengths were missing and observations werenot simultaneous. We span a wide range of the spectrum. Images in reflectedsunlight range from 225 to 889 nm, captured by the WFC3instrument on Hubble, from 1 to 2 February 2017. Images in thethermal infrared were obtained at 4.7 microns with the NIRIinstrument at Gemini North, on 2 and 5 February 2017, and high-resolution infrared spectroscopy at similar wavelengths wasperformed with Keck NIRSPEC on 5 and 6 February 2017.Spectral imaging was performed in the 1.2 to 1.7 cm range by theVLA, on 2 February 2017. These three data sets measure velocitiesin different ways. Our initial correlation of the multispectral dataset involves flow ina 5-micron hot spot (very similar in morphology to the oneimaged by the Galileo Orbiter in Vasavada et al., 1998), found at alongitude of about 330 deg on UT 2017-02-02. At this longitude,Hubble imaging data provide coverage of the feature over threeJupiter rotations, enabling retrieval of two separate velocityfields, 10 hours apart. Both velocity fields show similar features tothe Vasavada hot spot, particularly an anticyclonic circulation inthe "oval cloud" to the southeast of the hot spot. The Gemini dataconfirm that the dark area in the Hubble imaging correspondsexactly to a region of high 5-micron emission, which is a sign of

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downward flow, as traced by low cloud opacity. The infraredspectroscopy will be inverted to measure NH3 and H2O gasabundance profiles. VLA data require much more calibration andprocessing, but eventually will reveal how locations of highammonia abundance trace upwelling flow, a capabilitydemonstrated by earlier observations by the VLA at this latitude(de Pater et al. 2016).

Author(s): Michael H. Wong , Mate Adamkovics , AlbertoAdriani , Sushil K. Atreya , Megan Barnett , Gordon LBjoraker , Bryan J. Butler , Imke de Pater , Philip Marcus ,Glenn S. Orton , Amy A. Simon , Andrew W. Stephens , JoshuaTollefsonInstitution(s): 1. Clemson University, 2. Gemini Obs., 3. INAF,4. JPL, 5. NASA GSFC, 6. NRAO, 7. University of California, 8.University of Michigan

119.01 – Boise State's Idaho Eclipse OutreachProgramThe 2017 total solar eclipse is an unprecedented opportunity forastronomical education throughout the continental United States.With the path of totality passing through 14 states, from Oregonto South Carolina, the United States is expecting visitors from allaround the world. Due to the likelihood of clear skies, Idaho was apopular destination for eclipse-chasers. In spite of considerableenthusiasm and interest by the general population, the resourcesfor STEM outreach in the rural Pacific Northwest are very limited.In order to help prepare Idaho for the eclipse, we put together acrowdfunding campaign through the university and raised over$10,000. Donors received eclipse shades as well as informationabout the eclipse specific to Idaho. Idaho expects 500,000visitors, which could present a problem for the many small, ruraltowns scattered across the path of totality. In order to helpprepare and equip the public for the solar eclipse, we conducted aseries of site visits to towns in and near the path of totalitythroughout Idaho. To maximize the impact of this effort, theprogram included several partnerships with local educational andcommunity organizations and a focus on the sizable refugee andlow-income populations in Idaho, with considerable attendanceat most events.

Author(s): Karan Davis , Brian JacksonInstitution(s): 1. Boise State University

119.02 – Moving People from Science Adjacent toScience Doers with Twitch.tvThe CosmoQuest community is testing the ability to attractpeople from playing online videogames to doing fully online

citizen science by engaging people through the Twitch.tvstreaming platform. Twitch.tv launched in 2011 as an onlineplatform for video gamers to stream their gameplay whileproviding narrative. In its six years of regular growth, theplatform has added support for people playing non-video games,and for those participating in non-game activities. As part of theirexpansion, in April 2017, Twitch.tv hosted a science week duringwhich they streamed the Cosmos series and allowed differentfeeds provide real-time commentary. They also hosted paneldiscussions on a variety of science topics. CosmoQuestparticipated in this event and used it as a jumping off point forbeginning to interact with Twitch.tv community members online.With CosmoQuest’s beta launch of Image Detectives, theyexpanded their use of this streaming platform to include regular“office hours”, during which team members did science withCosmoQuest’s online projects, took questions from communitymembers, and otherwise promoted the CosmoQuest community.This presentation examines this case study, and looks at how welldifferent kinds of Twitter engagements attracted audiences, theconversion rate from viewer to subscriber, and at how effectivelyCosmoQuest was able to migrate users from viewing citizenscience on Twitch.tv to participating in citizen science onCosmoQuest.org. This project was supported through NASA cooperativeagreement NNX17AD20A.

Author(s): Pamela L. GayInstitution(s): 1. Astronomical Society of the PacificContributing team(s): CosmoQuest

200.02 – The Rosetta Mission to Comet67P/Churyumov-Gerasimenko: The USContributionsThe International Rosetta Mission to comet 67P/Churyumov-Gerasimenko was the first deep space mission to rendezvous withand follow a Jupiter-family comet through a full perihelionpassage. Developed and flown by the European Space Agency(ESA), the U.S. made key contributions including threeinstruments on the Rosetta orbiter: the Allice ultravioletspectrometer, the Microwave Instrument for Rosetta (MIRO),and the Ion Electron Spectrometer (IES), which was part of theRosetta Plasma Consortium (RPC). The U. S. also contributedpart of the Rosetta Orbiter Ion and Neutral Analyzer (ROSINA)’selectronics, provided shadow navigation, an InterdisciplinaryScientist specializing in nucleus studies, and many co-investigators to ESA-led instruments.


Author(s): Bonnie J. Buratti , Paul R. WeissmanInstitution(s): 1. JPL, 2. Planetary Science Institute

200.03 – Iapetus: Tenth Anniversary of the CassiniFlyby and the Albedo Dichotomy Enigma

Ten years ago, on 10 Sep 2007, Cassini (the spacecraft) performedthe only targeted flyby of Saturn's outermost regular moonIapetus and came as close as 1620 km to its surface [1]. Cassiniapproached Iapetus over the unlit low-albedo leadinghemisphere, flew over the ridge on the anti-Saturn side duringclosest approach, and departed over the illuminated brighttrailing side. This flyby was different in many aspects to all othersatellite flybys of Cassini. For example, it occured near apoapsisof the spacecraft orbit, and the flyby velocity was much lower thanususal, allowing for an unusually intensive observing program.There was also a major change in the sub-spacecraft groundtrackimplemented in 2006 primarily because of the discovery of theequatorial ridge in late 2004. Unexpected (and unpleasant)events like a spacecraft safing occuring just about 15 min afterdata playback start are also part of the story. Iapetus was originally discovered by Cassini (the man) in 1671,and only six years later, he published a paper where he correctlydescribed the albedo dichotomy that Iapetus is famous for [2].Over the following ~300 years, no progress was made with regardto the cause of this phenomenon. Since the 1970s, numerousideas have been published, but all shared the common property ofnot being widely accepted. One of the top science tasks for Cassini(the spacecraft) to solve was this enigma which was among theoldest unresolved questions in planetary sciences.

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The talk recaps the efforts to explain the albedo dichotomy [3]and gives an overview of the Cassini Iapetus observation planningand execution with an emphasis on the 2007 targeted flyby.

As a final sidenote, the monolith from Arthur Clarke's novel"2001 - A Space Odyssey" [4] was not detected in the images.

[1] Denk, T. (2008): Cassini at Iapetus: A Bumpy but SuccessfulFlyby. The Planetary Report, Vol. XXVIII, no. 1, pp. 10-16,Jan/Feb 2008. [2] Cassini, J.D. (1677): Some New Observations Made by Sig.Cassini and Deliver'd in the Journal Des Sçavans, Concerning theTwo Planets about Saturn, Formerly Discover'd by the Same, asAppears in N. 92. of these Tracts. Philosophical Transactions 12,No. 133, 831-833 (25 Mar 1677). [3] Spencer, J.R., Denk, T. (2010): Formation of Iapetus'sExtreme Albedo Dichotomy by Exogenically-Triggered ThermalMigration of Water Ice. Science 327, 432-435. [4] Clarke, A.C. (1968): 2001 - A Space Odyssey. New AmericanLibrary, 221 pp.

Author(s): Tilmann DenkInstitution(s): 1. Freie Universität

200.04 – The 2016 Transit of Mercury and theSolar ParallaxWe observed the 9 May 2016 transit of Mercury with the 1.6-mNew Solar Telescope of the Big Bear Solar Observatory of the NewJersey Institute of Technology in California and with smallertelescopes in Germany. The solar granulation behind thesilhouette of Mercury can be aligned, showing Mercury's parallax.From these observations, the value of the solar parallax can bedetermined, showing historical parallels. As a second method ofmaking the parallactic shift of Mercury visible and the distance tothe sun measurable, we aligned photos taken with telescopes ofshorter focal lengths, for instance, by using the prominentsunspots.

Author(s): Jay M. Pasachoff , Udo Backhaus , BerndGährken , Glenn SchneiderInstitution(s): 1. Bavarian Public Observatory, 2. StewardObs., U. Arizona, 3. Universität Duisburg-Essen, 4. WilliamsCollege

201.01 – The excitation of a primordial coldasteroid belt as a natural outcome of the planetaryinstabilityThe initial dynamical state of the main asteroid belt (MB) alwayspuzzled astronomers and it is still a hot subject under debate. Foryears, the currently well known Grand Tack model wasconsidered to be the only capable of reconciling the formation ofthe terrestrial planets together with a well dynamically excitedMB. This model, despite its success, is still not generally acceptedgiven that it implies an invasion of Jupiter within the terrestrialregion, passing through the MB twice. Other models for theterrestrial planet formation, on the other hand, always end upwith a fully or partially cold MB formed. It was recently proposedthat a chaotic evolution for Jupiter and Saturn before theplanetary instability of the Solar System could excite an initiallycold MB. However, hydrodynamical simulations predict that theorbits of those planets at the end of the gas disk phase should becharacterized by resonant and regular motion. Therefore, theorigin of this chaotic evolution is not fully understood. Here,assuming initial resonant and regular motion for Jupiter andSaturn, we propose a different mechanism capable of exciting aprimordial cold MB during the planetary instability. For this, weassume that the planetary instability was of the jumping-Jupiter(JJ) type, and that it accounts for all the constraints alreadyplaced. Our results, which also possibly can explain the pathwayto the chaotic evolution of Jupiter and Saturn, show that whenJupiter gets a temporary large enough level of excitation, both ineccentricity and inclination, it induces strong forced vectors ofeccentricity and inclination within the MB region. Then, becausein the JJ instability Jupiter is jumping around, such forcedvectors keep changing both in magnitude and phase throughoutthe whole MB region. Thus, depending on the evolution of Jupiterduring the JJ instability, the excitation of a primordial cold MBcan indeed be achieved as a natural outcome of the planetaryinstability for any initial planetary configuration.Acknowledgment FAPESP 2014/02013-5.

Author(s): Rogerio Deienno , André Izidoro , Rodney S.Gomes , Alessandro Morbidelli , David NesvornyInstitution(s): 1. National Institute for Space Research - INPE,2. National Observatory - ON, 3. Nice Observatory - OCA, 4.Southwest Research Institute - SwRI, 5. UNESP - Sao PauloState University

201.02 – A primordial inner Main Belt asteroidfamily that pre-dates the giant planet instabilityHere we report the discovery of a primordial asteroid family inthe inner portion of the Main Belt whose properties suggest that it

is over 4 Gyr old and whose members include most low-albedoasteroids previously unlinked to families. This family was identified by the V-shape detection algorithm(Bolin et al. 2016, Icarus 282 p290) that detects outer boundariesof families that spread by the Yarkovsky effect. The slope of theouter boundary points to an age of at least 4 Gyr. The dispersionof the distribution of the eccentricities and inclinations of theorbits of the primordial family members suggests that the familyformed before the instability of the giant planets. The family isalso primitive, with very low-albedo objects most of which arealso classified in the spectroscopic C-complex. The primordialfamily also overlaps with other primitive inner Main Belt familiessuch as Eulalia and Polana, which have previously been shown tohave spectral homogeneity (de Leon et al. Icarus 267 p57;Pinnella-Alonso et al. Icarus 274 p231).

Author(s): Marco Delbo , Kevin J. Walsh , Bryce T. Bolin ,Chrysa Avdellidou , Alessandro MorbidelliInstitution(s): 1. ESTEC/ESA, 2. Observatoire de la Coted'Azur, 3. Southwest Research Institute

201.03 – Beyond the families - the size distributionof non-family asteroids in the inner main beltThere are three large and old low-albedo families in the innerportion of Main Asteroid Belt that may account for the majority ofdark asteroids in this region. The inner boundary of the oldestfamily creates a size-dependent line across the belt inward ofwhich there are no small dark asteroids. This void of asteroidsclarifies the edge of this very old family, but also highlights ahandful of large bodies that can't be part of any known family anddo not have observed family of their own. We interpret them to beoriginal asteroid belt objects, which formed from direct accetionfrom the protoplanetary disk. These bodies are all larger than35km in diameter. Their sizes point to a large formation size andthe total number of primitive bodies in this region of the belt,extrapolated across the entire belt and taxonomies, roughlymatch the number of known unique meteorite parent body types.

Author(s): Kevin J. Walsh , Marco Delbo , Bryce T. Bolin ,Chrysa Avdellidou , Alessandro MorbidelliInstitution(s): 1. CNRS/Observatoire de la Cote d'Azur, 2.ESTEC/ESA, 3. Southwest Research Institute

201.04 – The Midplane of the Main Asteroid Beltand Its WarpsIt has been recognized for a long time that the orbital planes ofasteroids are surprisingly highly dispersed about the mean planeof the solar system, and likely memorialize dynamical events overthe ancient history of the solar system. But how well do we know

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the mean plane of the asteroid belt? Since the time of the firstmeasurements of their mean plane (Plummer 1916; Shor &Yagudina 1991), the number of known main belt asteroids(MBAs) has dramatically increased; the large size of thispopulation now allows measuring its mean plane at much higheraccuracy than in previous studies and also allows to compare itwith theoretical expectations. The theoretically expected meanplane is defined by the forced solution of the secular perturbationtheory for the inclinations and nodes (e.g., Murray & Dermott1999); this forced plane varies with semi-major axis. We measurethe mean plane by analyzing the observational data and wecompare it with the theoretical prediction. Our observationallynearly complete sample consists of 89,216 numbered, non-collisional family asteroids of absolute magnitude below 15.5. Forthe population as a whole, we find that the mean plane differssignificantly from previous measurements: the mean plane’sinclination is I = 0.929 (+0.042, -0.042) degrees and its longitudeof ascending node is Ω = 87.60 (+2.58, -2.58) degrees. Whenmeasured in small semi-major axis bins between 2.15 and 3.25AU, the mean plane is found to be largely consistent with secularperturbation theory predictions, deviating not more than (1-2)-σfrom the theoretically expected values. A warp near the inneredge, due to the ν secular resonance, is visible in the data. Ouranalysis reveals the way to a novel method for the computation ofthe free or “proper” inclinations of the MBAs, by computingasteroid inclinations relative to the measured mean plane at thatlocation in semi-major axis.

This study used the catalogs of osculating elements for the minorplanets and collisional family membership available on theAstDys-2 website (http://hamilton.dm.unipi.it/astdys/). We aregrateful for research funding from NSF (grant AST-1312498).

Author(s): Saverio Cambioni , Renu MalhotraInstitution(s): 1. The University of Arizona

201.05 – Collisional disruptions of rotating targetsCollisions are key processes in the evolution of the Main AsteroidBelt and impact events - i.e. target fragmentation andgravitational reaccumulation - are commonly studied bynumerical simulations, namely by SPH and N-body methods. Inour work, we extend the previous studies by assuming rotatingtargets and we study the dependence of resulting size-distributions on the pre-impact rotation of the target. To obtainstable initial conditions, it is also necessary to include the self-gravity already in the fragmentation phase which was previouslyneglected.

To tackle this problem, we developed an SPH code, accelerated bySSE/AVX instruction sets and parallelized. The code solves thestandard set of hydrodynamic equations, using the Tillotsonequation of state, von Mises criterion for plastic yielding andscalar Grady-Kipp model for fragmentation. We further modifiedthe velocity gradient by a correction tensor (Schäfer et al. 2007)to ensure a first-order conservation of the total angular

momentum. As the intact target is a spherical body, its gravity canbe approximated by a potential of a homogeneous sphere, makingit easy to set up initial conditions. This is however infeasible forlater stages of the disruption; to this point, we included theBarnes-Hut algorithm to compute the gravitational accelerations,using a multipole expansion of distant particles up tohexadecapole order. We tested the code carefully, comparing the results to ourprevious computations obtained with the SPH5 code (Benz andAsphaug 1994). Finally, we ran a set of simulations and wediscuss the difference between the synthetic families created byrotating and static targets.

Author(s): Pavel Ševeček , Miroslav BrozInstitution(s): 1. Astronomical Institute of Charles University

201.06 – Asteroid mass estimation with Markov-chain Monte CarloEstimates for asteroid masses are based on their gravitationalperturbations on the orbits of other objects such as Mars,spacecraft, or other asteroids and/or their satellites. In the case ofasteroid-asteroid perturbations, this leads to a 13-dimensionalinverse problem at minimum where the aim is to derive the massof the perturbing asteroid and six orbital elements for both theperturbing asteroid and the test asteroid by fitting theirtrajectories to their observed positions. The fitting has typicallybeen carried out with linearized methods such as the least-squares method. These methods need to make certainassumptions regarding the shape of the probability distributionsof the model parameters. This is problematic as theseassumptions have not been validated. We have developed a newMarkov-chain Monte Carlo method for mass estimation whichdoes not require an assumption regarding the shape of theparameter distribution. Recently, we have implemented severalupgrades to our MCMC method including improved schemes forhandling observational errors and outlier data alongside theoption to consider multiple perturbers and/or test asteroidssimultaneously. These upgrades promise significantly improvedresults: based on two separate results for (19) Fortuna withdifferent test asteroids we previously hypothesized thatsimultaneous use of both test asteroids would lead to animproved result similar to the average literature value for (19)Fortuna with substantially reduced uncertainties. Our upgradedalgorithm indeed finds a result essentially equal to the literaturevalue for this asteroid, confirming our previous hypothesis. Herewe show these new results for (19) Fortuna and other examplecases, and compare our results to previous estimates. Finally, wediscuss our plans to improve our algorithm further, particularly inconnection with Gaia.

Author(s): Lauri Siltala , Mikael GranvikInstitution(s): 1. University of Helsinki

202.02 – Are Makemake and Eris Sputnik Planets?Makemake and Eris have high albedos (Sicardy et al. 2011; Ortizet al. 2012) and show strong spectral absorption by CH ice(Licandro et al. 2006; Brown et al. 2007; Dumas et al. 2007).Energetic space radiation breaks C-H bonds in CH producingfragments that recombine into dark, red macromolecularmaterials (tholins, e.g., Johnson et al. 1987; Thompson et al.1987; Strazzulla et al. 1991). This fact, coupled with Pluto's strongCH ice absorption bands and high albedo led Stern (1988) topose the question "why is Pluto bright?". New Horizons hasconfirmed that Pluto refreshes its surface via seasonal volatiletransport (e.g., Stern et al. 2015). However, one part of Plutorefreshes itself in a different way, too. This is the informallynamed Sputnik Planitia, a vast plain of volatile ice partly filling aprobable impact basin. The ice is thick enough to act as a barrierto internal radiogenic heat flow, which drives convectiveoverturning on 10 to 10 year timescales (e.g., McKinnon et al.2016; Trowbridge et al 2016). Vigorous convection in Sputnik

mixes radiolytic products from the surface down into the bulk ofthe ice, diluting it, and thus maintaining the high albedo of thesurface. We propose that the surfaces of Eris and Makemake are similarlyrefreshed by convection in deep volatile ice deposits, perhapscovering the majority of their surfaces, unlike Pluto's Sputnik,which only covers a small fraction. The local fluxes of energeticradiation dictate production rates for tholin. Assuming steady-state production over the age of the solar system and mixing intothe volatile ice, the colors and albedos of the bodies can be used toestimate the thickness of the volatile ice into which the tholin hasbeen diluted through convective mixing. Likewise, for plausibleradiogenic internal heat production, lower limits can be set on thethickness of the ice, to support convective mixing. We don't knowthe rheological properties of mixed N +CH ice, let alone whathappens when plausible additional contaminants, such as CO, Ar,C H , C H , C H , etc. are added, but bounding cases for N -

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dominated and CH -dominated ice compositions can becalculated.

Author(s): William M. Grundy , Orkan M. UmurhanInstitution(s): 1. Lowell Obs., 2. NASA Ames Research Ctr.

202.03 – An Answer to Fermi’s Paradox In thePrevalence of Ocean Worlds?The Fermi Paradox (e.g., [1]) asks the question aboutextraterrestrial civilizations, “Where are they?” Givenspeculations based on numerical evaluations of the DrakeEquation that would seem to indicate that the likelihood ofprecisely N=1 communicating extraterrestrial civilizations in theUniverse is small, i.e., that we are unique, the Fermi Paradoxremains a puzzle. Many possible explanations have beenproffered. We suggest another—namely that the great majority ofworlds with biology and civilizations are interior water oceanworlds (WOWs). Interior WOWs appear to be particularlyconducive to the development of life owing to several keyadvantages, including these two: (1) EnvironmentalIndependence to Stellar Type, Multiplicity, and Distance. Owingto the several to hundreds of kilometers depth of typical Type IIliquid water oceans, and the overlying thermal insulationprovided by the planetary lid atop these oceans, the energybalance, temperature, pressure, and toxicity in Type II oceanworlds is only weakly coupled to their host star’s stellar type,stellar multiplicity, stellar distance, and stellar evolutionary stage(i.e., from protostars with winds and high activity through themain sequence to stellar remnants). (2) Environmental Stability.Again owing to the depth of typical Type II oceans and theoverlaying thermal insulation provided by the planetary lid atopthese oceans, these environments are protected from numerouskinds of external risks to life, such as impacts, radiation, surfaceclimate and obliquity cycles, poisonous atmospheres, and nearbydeleterious astrophysical events such as novae and supernovae,hazards stellar flares, and even phenomena like the Faint EarlySun. Interior WOWs are naturally cut off from communication bytheir interior nature below a thick roof of ice or rock and ice,therefore do not easily reveal themselves. In this talk I willexamine this new idea in more detail. [1] Hart, M.H., 1975.Explanation for the Absence of Extraterrestrials on Earth.Quarterly Journal of the Royal Astronomical Society, Vol. 16,p.128-135.

Author(s): S. Alan SternInstitution(s): 1. SwRI

202.04 – The radiation stability of the RNA baseuracil in H O-ice and CO -ice: in-situ laboratorymeasurements with applications to comets,Europa, and MarsPlanetary bodies of astrobiological interest, such as Mars, areoften exposed to harsh incident radiation, which will influencethe times that molecules can survive on them. Some or all of thesebodies may well contain biologically-important organicmolecules, some may even have supported life at some point intheir history, and some may support life today. Future searchesfor organic molecules likely will include sampling the martiansubsurface or a cometary surface sample return mission, whereorganics may be frozen in ices dominated by either H O or CO ,which provide some protection from ionizing radiation.

Recently, our research group has published studies of theradiation stability of amino acids, with a focus on glycine - in bothundiluted form and in mixtures with H O and CO . Here, wepresent a similar study that focuses on the radiation-chemical

kinetics of the RNA base uracil. We compare results for uracildecay for dilution in both H O and CO ices. Moreover, wecompare these new results with those for glycine. For eachsample, we measured uracil’s destruction rate constant and half-life dose due to irradiation by 0.9-MeV protons. Allmeasurements were made in situ at the temperature ofirradiation using IR spectroscopy. Trends with dilution (up to~300:1) and temperature (up to ~150 K) are considered, andresults are discussed in the context of icy planetary surfaces. Acknowledgment: Our work is supported in part by the NASAEmerging Worlds Program and by the NASA AstrobiologyInstitute through the Goddard Center for Astrobiology.

Author(s): Perry A. Gerakines , Sarah Frail , Reggie L.HudsonInstitution(s): 1. NASA GSFC

202.05D – A Methane-Rich Early Mars:Implications for Habitability and the Emergence ofLifeWe investigate the radiation and chemistry of a ~4.0 Ga, CH -rich martian atmosphere in an effort to assess whether or notMars was once habitable and suitable for the emergence of life.High atmospheric CH may be consistent with a mantle that doesnot reach the requisite pressure (24 GPa) and temperature (1900K) for the silicate spinel-to-perovskite transition (Dale et al.,2012; McCammon, 1997; Wadhwa, 2001; Wood et al., 2006).Impact degassing from chondritic material can also contributesubstantial amounts of CH to the atmosphere (Schaefer andFegley, 2007). CH plays an important role in atmospheric radiation.Atmospheric models have demonstrated that a purely COatmosphere, even one as massive as 7 bars, is incapable of heatingMars above an annual-mean surface temperature of 273 K (Forgetet al., 2013), although recent studies show that recurring wetstates could have been induced in an H -rich atmosphere(Batalha et al., 2015, 2016). We show that CH alone isinsufficient to warm early Mars above freezing—in fact itproduces an anti-greenhouse effect—but it substantially raisesmiddle atmospheric temperatures. We determine whether or notsuch high temperatures could prolong the photochemical lifetimeof SO , another potent greenhouse gas. We use RC1D, a non-gray 1-D radiative-convective equilibriummodel, to calculate the atmospheric thermal structure consistentwith the radiative heating and cooling associated with thecomposition computed at each chemical model time step.KINETICS, the Caltech/JPL chemistry transport model (e.g. Nairet al., 1994), determines the chemical makeup of the atmosphere,evaluating steady-state chemical profiles and the synthesis ofastrobiologically relevant molecules. H O is in vapor pressureequilibrium at the surface. We consider conditions forced by thefaint-young Sun’s spectrum and luminosity. By coupling RC1D and KINETICS, we are able to paint a morerealistic picture of Mars’s early climate, calculating the surfacetemperature under a CH -rich atmosphere, and assessing theproduction of key electron acceptors, such as sulfate and nitrate.

Author(s): Michael L Wong , Andrew James Friedson ,Karen Willacy , Run-Lie Shia , Yuk Yung , Michael J RussellInstitution(s): 1. Caltech, 2. JPL

203.01 – Surface Modification and Surface -Subsurface Exchange Processes on EuropaThe surface of Jupiter’s moon Europa is modified by exogenicprocesses such as sputtering, gardening, radiolysis, sulfur ionimplantation, and thermal processing, as well as endogenicprocesses including tidal shaking, mass wasting, and the effects of

subsurface tectonic and perhaps cryovolcanic activity. Newmaterials are created or deposited on the surface (radiolysis,micrometeorite impacts, sulfur ion implantation, cryovolcanicplume deposits), modified in place (thermal segregation,sintering), transported either vertically or horizontally(sputtering, gardening, mass wasting, tectonic and cryovolcanicactivity), or lost from Europa completely (sputtering, plumes,

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larger impacts). Some of these processes vary spatially, as visiblein Europa’s leading-trailing hemisphere brightness asymmetry.

Endogenic geologic processes also vary spatially, depending onterrain type. The surface can be classified into general landformcategories that include tectonic features (ridges, bands, cracks);disrupted “chaos-type” terrain (chaos blocks, matrix, domes, pits,spots); and impact craters (simple, complex, multi-ring). Thespatial distribution of these terrain types is relatively random,with some differences in apex-antiapex cratering rates andlatitudinal variation in chaos vs. tectonic features.

In this work, we extrapolate surface processes and rates from thetop meter of the surface in conjunction with global estimates oftransport and resurfacing rates. We combine near-surfacemodification with an estimate of surface-subsurface (and viceversa) transport rates for various geologic terrains based on anaverage of proposed formation mechanisms, and a spatialdistribution of each landform type over Europa’s surface area.

Understanding the rates and mass balance for each of theseprocesses, as well as their spatial and temporal variability, allowsus to estimate surface – subsurface exchange rates over theaverage surface age (~50myr) of Europa. Quantifying thetimescale and volume of transported material will yield insight onwhether such a process may provide fuel to sustain a biosphere inEuropa’s subsurface ocean, which is relevant to searches for lifeby a future mission such as a potential Europa Lander.

Author(s): Cynthia B. Phillips , Jamie Molaro , Kevin P.HandInstitution(s): 1. NASA Jet Propulsion Lab / Caltech

203.02 – Breaking the shell: Initiating platetectonic-like subduction on EuropaEuropa’s prominent bands have been proposed to form by aseafloor-spreading-like mechanism involving complete separationof Europa’s lithosphere and the emplacement of fresh ice frombelow [Prockter et al. 2002]. This formation mechanism poses achallenge for Europa’s strain balance: extensional rifting at bandsmust be offset by lithospheric shortening elsewhere, yet fewobvious contractional features have been observed. Kattenhornand Prockter [2014] suggested that extension on Europa isaccommodated by subduction of the lithosphere at linear, tabularzones termed subsumption bands. Subduction of Europa’slithosphere implicitly requires that lithospheric-scale thrust faultscan develop. This contrasts with previous numerical modeling,which found that lithospheric shortening is instead primarilyaccommodated by folding or passive thickening [Bland andMcKinnon 2012, 2013]. Here we reevaluate the conditionsrequired to form large-scale thrust faults using a numerical modelof lithospheric shortening on Europa that includes realisticlocalization of brittle failure (non-associated plasticity). In theabsence of strain weakening (wherein brittle failure decreases thesubsequent yield strength) essentially all shortening results infolding or thickening, consistent with previous results. Withmoderate strain weakening, deformation becomes localizedwithin fault-like zones for surface temperatures ≤100 K; however,the resulting surface deformation suggests a complex interplaybetween folding and faulting. Only if the ice shell weakens veryeasily does faulting dominate. Large-scale faults preferentiallyform at cold surface temperatures and high heat fluxes. Coldtemperatures promote faulting (as opposed to folding), and highheat fluxes result in a thinner lithosphere, which is more easilysubducted. The subsumption bands identified by Kattenhorn andProckter [2014] are at a relatively high latitude (coldtemperature), and are associated with putative cryovolcanicfeatures indicating locally increased heat flow, suggestingconditions there may have been ideal for the initiation ofsubduction.

Author(s): Michael T. Bland , William B. McKinnonInstitution(s): 1. U. S. Geological Survey, Astrogeology ScienceCenter, 2. Washington University in Saint Louis

203.03 – Occurrence and Detectability of ThermalAnomalies on EuropaEndogenic activity is likely on Europa, given its young surface ageof and ongoing tidal heating by Jupiter. Temperature is afundamental signature of activity, as witnessed on Enceladus,where plumes emanate from vents with strongly elevatedtemperatures. Recent observations suggest the presence ofsimilar water plumes at Europa. Even if plumes are uncommon,resurfacing may produce elevated surface temperatures, perhapsdue to near-surface liquid water. Detecting endogenic activity onEuropa is one of the primary mission objectives of NASA’splanned Europa Clipper flyby mission. Here, we use a probabilistic model to assess the likelihood ofdetectable thermal anomalies on the surface of Europa. TheEuropa Thermal Emission Imaging System (E-THEMIS)investigation is designed to characterize Europa’s thermalbehavior and identify any thermal anomalies due to recent orongoing activity. We define “detectability” on the basis ofexpected E-THEMIS measurements, which include multi-spectralinfrared emission, both day and night. Thermal anomalies on Europa may take a variety of forms,depending on the resurfacing style, frequency, and duration ofevents: 1) subsurface melting due to hot spots, 2) shear heating onfaults, and 3) eruptions of liquid water or warm ice on the surface.We use numerical and analytical models to estimate temperaturesfor these features. Once activity ceases, lifetimes of thermalanomalies are estimated to be 100 - 1000 yr. On average,Europa’s 10 - 100 Myr surface age implies a resurfacing rate of ~3- 30 km /yr. The typical size of resurfacing features determinestheir frequency of occurrence. For example, if ~100 km chaosfeatures dominate recent resurfacing, we expect one event everyfew years to decades. Smaller features, such as double-ridges,may be active much more frequently. We model each feature typeas a statistically independent event, with probabilities weightedby their observed coverage of Europa’s surface. Our results showthat if Europa is resurfaced continuously by the processesconsidered, there is a >99% chance that E-THEMIS will detect athermal anomaly due to endogenic activity. Therefore, if noanomalies are detected, these models can be ruled out, or revised.

Author(s): Paul O. Hayne , Philip R Christensen , John R.Spencer , Oleg Abramov , Carly Howett , Michael Mellon ,Francis Nimmo , Sylvain Piqueux , Julie A. RathbunInstitution(s): 1. Applied Physics Laboratory, 2. Arizona StateUniversity, 3. Jet Propulsion Laboratory, 4. Planetary ScienceInstitute, 5. Southwest Research Institute, 6. UC Santa Cruz

203.04 – Update on Plumes at EuropaSeveral recent papers (Roth et al. 2014; Sparks et al. 2016; Sparkset al. 2017) have reported evidence for active plumes at Europa.Plumes would provide a crucial method to "touch the water" atEuropa, i.e., to more directly sample the composition of thesubsurface ocean, avoiding the confusion bound to occur withsurface or sputtered atmosphere sampling, which arecontaminated with exogenic material, as well as altered viaradiolytic processing by Jovian magnetospheric plasma. Inparticular, Sparks et al. (2017) has reported evidence for a second,repeat detection of a plume near the crater Pwyll that iscoincident with a possible thermal (or thermal inertia) anomaly atthe same location, reported in Spencer et al. (1999). Wesummarize the recent observational evidence for plumes atEuropa, as well as identify another unique feature that is virtuallycoincident with the repeat plume detection near Pwyll, whichfurther strengthens the case for ongoing activity at thisfascinating moon.

Author(s): Melissa McGrath , William B. Sparks , KevinHand , Britney E Schmidt , John R. Spencer , Misty Cracraft ,Susana E. DeustuaInstitution(s): 1. Georgia Institute of Technology, 2. JetPropulsion Laboratory, 3. SETI Institute, 4. Southwest ResearchInstitute, 5. Space Telescope Science Institute

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203.05 – ALMA Thermal Observations of Europa We present four daytime thermal images of Europa taken withthe Atacama Large Millimeter Array. These images map the entiresurface in thermal emission at a frequency of 233 GHz with alinear resolution of ~ 200 km. At this resolution, the imagescapture spatially localized thermal variations on the scale ofgeologic and compositional units. In order to understand thesevariations, we develop a global thermal model of Europa andsimulate the ALMA observations. The model reproduces large-scale structure well, but some localized discrepancies exist. Ofparticular note is the region northwest of Pwyll Crater, which isassociated with a nighttime thermal excess seen by the GalileoPhotopolarimeter Radiometer and with two potential plumedetections. Using our model, we investigate whether thenighttime thermal anomaly can be attributed to excess endogenicheat flow, as might be expected from a plume source region. Wefind that the nighttime and daytime brightness temperatures nearPwyll Crater cannot be matched by including excess heat flow atthat location. Rather, we can successfully model bothmeasurements with an elevated local surface thermal inertia. Wealso employ our model to investigate thermal features and theirpotential causes across the rest of Europa’s surface.

Author(s): Samantha K. Trumbo , Michael Brown , Bryan J.ButlerInstitution(s): 1. California Institute of Technology, 2.National Radio Astronomy Observatory

203.06 – Europa in the Far-UV: Spatial andSpectral Analysis from HST ObservationsWe present a spatial and spectral analysis of Europa using far-UVobservations from 1999 – 2015 made by the Space TelescopeImaging Spectrograph (STIS) on the Hubble Space Telescope(HST). Disk-integrated observations show that the far-UVspectrum from ~130 nm – 170 nm is blue (increasing albedo withdecreasing wavelength) for the studied hemispheres: the leading,trailing, and anti-Jovian hemispheres. At Lyman-alpha (121.6nm), the albedo of the trailing hemisphere continues the bluetrend, but it reddens for the leading hemisphere. At wavelengthsshorter than 133.5 nm, the leading hemisphere, which is brighterthan the trailing hemisphere at near-UV and visible wavelengths,becomes darker than the trailing hemisphere. We find noevidence of a sharp water-ice absorption edge at 165 nm on anyhemisphere of Europa, which is intriguing since such anabsorption feature has been observed on most icy moons. Thissuggests the possibility that radiolytic alteration by Jovianmagnetospheric plasma has made the surface more stronglyabsorbing, masking the absorption edge. We will also present aspatial map of Lyman-alpha across the entire surface of Europa.This map can then be used to distinguish variable H emissions inthe atmosphere from surface reflectance, improving our ability todetect potential plumes occurring on the disk of Europa during anobservation.

Author(s): Tracy M Becker , Kurt D. Retherford , LorenzRoth , Amanda R. Hendrix , Melissa McGrath , Juan Alday ,Joachim Saur , Philippa M Molyneux , Ujjwal Raut , BenjaminTeolisInstitution(s): 1. Institute of Geophysics and Meteorology,University of Cologne, 2. Planetary Science Institute, 3. RoyalInstitute of Technology (KTH), 4. SETI, 5. Southwest ResearchInstitute

203.07 – Detectability of molecular gas signatureson Jupiter’s moon Europa from ground and space-based facilitiesPlumes and their effluent material could provide insights intoEuropa’s subsurface chemistry and relevant information aboutthe prospect that life could exist, or now exists, within the ocean.In 2016, we initiated a strong observational campaign tocharacterize the chemical composition of Europa’s surface andexosphere using high-resolution infrared spectroscopy. Whileseveral studies have focused on the detection of water, or itsdissociation products, there could be a myriad of complex

molecules released by erupting plumes. Our IR survey hasprovided a serendipitous search for several key molecular species,allowing a chemical characterization that can aid the investigationof physical processes underlying its surface. Since our tentativewater detection, presented at the 2016 DPS meeting, we havecontinued the observations of Europa during 2017 covering asignificant extent of the moon’s terrain and orbital position (trueanomaly), accounting for over 50 hr on source. Current analysesof these data are showing spectral features that grant furtherinvestigation. In addition to analysis algorithms tailored to theexamination of Europan data, we have developed simulation toolsto predict the possible detection of molecular species usingground-based facilities like the Keck Observatory, NASA’sInfrared Telescope and the Atacama LargeMillimeter/submillimeter Array (ALMA). In this presentation wewill discuss the detectability of key molecular species with theseremote sensing facilities, as well as expected challenges andfuture strategies with upcoming spacecrafts such as the JamesWebb Space Telescope (JWST), the Large UV/Optical/InfraredSurveyor (LUVOIR), and a possible gas spectrometer onboard anorbiter. This work is supported by NASA’s Keck PI Data Award (PI L.P.)and Solar System Observation Program (PI L.P.), and by theNASA Astrobiology Institute through funding awarded to theGoddard Center for Astrobiology (PI M.J.M.).

Author(s): Lucas Paganini , Geronimo Luis Villanueva ,Terry Hurford , Avi Mandell , Lorenz Roth , Michael J.MummaInstitution(s): 1. KTH, 2. NASA-GSFC

203.08 – Ice sintering timescales at the surface ofEuropa and implications for surface propertiesThe planned exploration of Europa by NASA’s Europa ClipperMission and the possibility of a future Europa lander have driventhe need to characterize its surface strength, roughness, porosity,thermal conductivity, and regolith depth in order to accuratelyinterpret remote sensing data and develop appropriate spacecraftlanding systems. Many processes contribute to Europa’slandscape evolution, such as sputtering, mass wasting, thermalsegregation, and impact gardening, driving the creation anddistribution of icy regolith across the surface. While the efficacy ofthese processes are not well constrained, any amount of regolithemplaced at the surface will undergo subsequent processing dueto sintering. Ice sintering is a form of frost metamorphismwhereby contacting ice grains experience the diffusion of materialinto their contact region, forming a “neck” between them anddensifying over time. Over long enough timescales, ice aggregateswill sinter into solid material, which may contribute to theincorporation of non-ice material into Europa’s subsurface andhelp to drive subsurface chemistry. Sintering also interacts withother processes, adding to the complexity of icy surface evolution.For example, sputtering preferentially removes larger grains andmay enhance sintering rates, and changes in ice porosity mayaffect the response of the surface to micrometeorite impacts. Quantifying the effects of ice sintering will allow us to predict themicrostructural properties of Europa’s surface at spacecraftscales. To this end, we have modeled pressure-less (nooverburden) sintering of spherical water-ice grains and validatedthe results with a laboratory experiment. We also modeled ice atthe surface of Europa to obtain a first-order approximation of thesintering timescale and surface properties. Preliminary resultsindicate that ice grains will experience neck growth but notsignificant densification over Europa’s surface age, suggestingthat loose surface ice forms a weak and porous crust.Furthermore, our results suggest that existing models do notaccurately quantify all stages of the sintering process for ice,emphasizing the need for more laboratory studies on this topic.

Author(s): Jamie Molaro , Cynthia B. Phillips , GarethMeirion-GriffithInstitution(s): 1. Jet Propulsion Laboratory

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203.09 – Laboratory Simulations of PlanetarySurfaces: Understanding Regolith PhysicalProperties from Remote PhotopolarimetricObservationsWe present reflectance and polarization phase curvemeasurements for a suite of highly reflective planetary regolithanalogues with physical characteristics that might be expected onthe surface of an atmosphereless solar system body (ASSB). Westudied thirteen well-sorted particle size fractions of aluminumoxide (Al O ) in the laboratory with a goniometricphotopolarimeter (GPP) of novel design. These results are highly relevant to understanding the unusualnegative polarization behavior observed near small phase anglesthat has been reported over several decades on highly reflectiveASSBs such as the asteroids 44 Nysa, 64 Angelina (Harris et al.,1989) and the Galilean satellites Io, Europa and Ganymede(Rosenbush et al., 1997; Mishchenko et al., 2006). Ourmeasurements are consistent with the hypothesis that thesurfaces of these ASSBs effectively scatter electromagneticradiation as if they were extremely fine grained with void space>~95%, and grain sizes of the order <= λ. This portendsconsequences for efforts to deploy surface landers on high ASSB’ssuch as Europa. These results also have relevance to the field ofterrestrial geo-engineering particularly to proposals for modifyingEarth’s radiation balance by injecting Al O particulates into thestratosphere for the purpose of offsetting the effect ofanthropogenic greenhouse gas emissions (Teller et al., 1997). Harris et al., 1989 . Icarus 81, 365–374. Mishchenko et al., 2006 Applied Optics, 45, 4459-4463. Rosenbush et al, 1997, Astrophys. J. 487, 402–414. Teller et al., 1997. UCRL-JC-128715.

Author(s): Robert M. Nelson , Mark Boryta , Bruce W.Hapke , Kenneth S. Manatt , Yuriy Shkuratov , VladimirPsarev , Kurt Vandervoort , Desire Kroner , Adaze Nebedum ,Christina Vides , John QuinonesInstitution(s): 1. California Polytechnic University at Pomona,2. California State University at Los Angeles, 3. Jet PropulsionLaboratory, 4. Karazin University, 5. Mount San AntonioCollege, 6. Planetary Science Institute, 7. University of Californiaat Los Angeles, 8. University of Pittsburgh

203.10 – Effect of MeV Electron Radiation onEuropa’s Surface Ice AnalogsMeV electrons that impact Europa’s trailing hemisphere andcause both physical and chemical alteration of the surface andnear-surface. The trailing hemisphere receives far lower fluxesabove 25 MeV as compared with lower energy particles, but cancause significant chemical and physical modifications at theseenergies. With NASA's planned Europa Clipper mission and aEuropa Lander Concept on the horizon, it is critical to understandand quantify the effect of Europa’s radiation environment on thesurface and near surface.

Electrons penetrate through ice by far the deepest at any givenenergy compared to protons and ions, making the role ofelectrons very important to understand. In addition, secondaryradiation – Bremsstrahlung, in X-ray wavelengths – is generatedduring high-energy particle penetration through solids.Secondary X-rays are equally lethal to life and penetrate evendeeper than electrons, making the cumulative effect of radiationon damaging organic matter on the near surface of Europa acomplex process that could have effects several meters belowEuropa’s surface. Other physical properties such as colorationcould be caused by radiation.

In order to quantify this effect under realistic Europa trailinghemisphere conditions, we devised, built, tested, and obtainedpreliminary results using our ICE-HEART instrument prototypetotally funded by JPL’s internal competition funding for Researchand Technology Development. Our Ice Chamber for Europa High-Energy Electron And Radiation-Environment Testing (ICE-HEART) operates at ~100 K. We have also implemented a magnetthat is used to remove primary electrons subsequent to passing

through an ice column, in order to determine the flux ofsecondary X-radiation and its penetration through ice. Some of the first results from these studies will be presented andtheir relevance to understand physical and chemical properties ofEuropa’s trailing hemisphere surface. This work has been carried out at Jet Propulsion Laboratory,California Institute of Technology under a contract with theNational Aeronautics and Space Administration, and funded byJPL’s R&TD Program and NASA Solar System WorkingsProgram.

Author(s): Murthy Gudipati , Bryana Henderson , FredBatemanInstitution(s): 1. Jet Propulsion Laboratory, CaliforniaInstitute of Technology, 2. National Institute of Standards andTechnology

203.11 – Ocean Tidal Dynamics and Dissipation inthe Thick Shell WorldsTidal dissipation in the subsurface oceans of icy satellites has sofar only been explored in the limit of a free-surface ocean orunder the assumption of a thin ice shell. Here we consider oceantides in the opposite limit, under the assumption of an infinitelyrigid, immovable, ice shell. This assumption forces the surfacedisplacement of the ocean to remain zero, and requires thesolution of a pressure correction to ensure that the ocean is massconserving (divergence-free) at all times. This work investigates the effect of an infinitely rigid lid on oceandynamics and dissipation, focusing on implications for the thickshell worlds Ganymede and Callisto. I perform simulations usinga modified version of the numerical model Ocean Dissipation inIcy Satellites (ODIS), solving the momentum equations forincompressible shallow water flow under a degree-2 tidal forcing.The velocity solution to the momentum equations is updatediteratively at each time-step using a pressure correction toguarantee mass conservation everywhere.

Author(s): Hamish Hay , Isamu MatsuyamaInstitution(s): 1. University of Arizona

203.12D – Atmospheric Bulges on Tidally-LockedSatellites We use a simple analytic model to examine the spatialdistribution of a volatile species in a surface-bounded atmosphereon a rotating object that is tidally-locked to its parent body.Spatial asymmetries in such atmospheres have recently beenobserved via ultraviolet auroral emissions from the exospheres ofthe icy satellites Europa and Ganymede. The Hubble SpaceTelescope observations indicate that these satellites host unique,surface-bounded O exospheres which bulge towards dusk. Usinga simple 1-D mass conservation balance we examine the nature ofthe volatile source, the surface temperature profile, the spatialmorphology of the loss process, and the adsorption anddesorption properties of the surfaces to understand the spatialdistribution of the surface-bounded atmosphere for a number ofobjects. Since the ballistic hop distances are much smaller thanthe satellite radii, we show that the observed asymmetries atEuropa and Ganymede can be simply due to a strongly thermally-dependent source, although asymmetries in the plasma-inducedloss could contribute. A key condition for these atmosphericbulges that are shifted towards dusk is the relationship betweenthe rotation rate and the atmospheric loss rate.

Author(s): Apurva V. Oza , Robert E. Johnson , FrancoisLeblancInstitution(s): 1. Université Pierre et Marie Curie, 2.University of Virginia

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204 – Asteroid Physical Characteristics: NEOs204.01 – Goldstone radar images of near-Earthasteroids (469896) 2007 WV4, 2014 JO25, 2017BQ6, and 2017 CSWe report Goldstone delay-Doppler radar imaging of four NEAsobtained during February–June 2017. The signal-to-noise ratioswere very strong for each object and we obtained detailed imageswith range resolutions as fine as 3.75 m/pixel. Delay-Dopplerimaging revealed that 2017 BQ6 is a strikingly angular objectroughly ~200 m in diameter with a rotation period of ~3 h. Themulti-faceted shape is puzzling assuming a rubble-pile structureof this asteroid. 2017 CS was discovered by Pan-STARRS 1 onFebruary 2 and approached within 8 lunar distances on May 29.2017 CS appears rounded on large scales but has considerablefine-scale topography evident along its leading edges. The imagessuggest a diameter of ~1 km and rotation visible in the images isconsistent with the 40 h rotation period obtained independentlyby from photometry by P. Pravec (pers. comm.). The highestresolution images show evidence for meter-size boulders, ridges,and broad concavities. 2007 WV4 was imaged in late May andearly June. 2007 WV4 appears distinctly angular, with a diameterin the realm of 900 meters, and with at least three large facetsmore than 100 m in extent. Tracking of features in the imagesgives a rotation period of about 12 hours. The echoes show apersistent, small topographic feature that extends out from thesurface. The nature of this feature is unknown, but it may be alarge boulder similar to Yoshinodai seen on 25143 Itokawa. 2014JO25 approached within 4.6 lunar distances on April 19. This wasthe closest encounter by an asteroid with an absolute magnitudebrighter than 18 known in advance until 2027, when 1999 AN10will approach within one lunar distance. Radar imaging showsthat 2014 JO25 is an irregular object, which consists of twocomponents connected by a narrow neck. The asteroid has a longaxis of about 1 km and a short axis of roughly 600 m. The 3.75 mrange resolution imaging placed thousands of pixels on the objectand reveals ridges, hills, concavities, flat regions up to 200 meterslong, and radar-bright spots that are probably boulders. Trackingof features in the images yields a rotation period of about 4.5hours that is among the fastest of the ~50 known contact binariesin the near-Earth population.

Author(s): Marina Brozovic , Lance A. M. Benner ,Shantanu P Naidu , Jon D. Giorgini , Michael Busch , JosephJao , Clement Lee , Lawrence Snedeker , Marc Silva , Martin A.Slade , Kenneth J. LawrenceInstitution(s): 1. Jet Propulsion Laboratory/Caltech, 2.SAITECH, Goldstone Deep Space Communication Complex, 3.SETI Institute

204.02 – Radar, Optical, and InfraredObservations of Equal-Mass Binary Near-EarthAsteroid (190166) 2005 UP156The binary nature of near-Earth asteroid (190166) 2005 UP156was shown by distinctive mutual events in its optical lightcurvesfrom 2017 May 4-23 (Warner & Harris, 2017; CBET 4394). Theobserved lightcurve period of 40.542 +/- 0.008 h agrees with theperiod determined in 2014 (Warner, 2015; Minor Planet Bulletin42, 41-53), though no mutual events were noted at that time. Anout-of-eclipse amplitude of 0.5 mag implies elongated shapes forthe components. Radar observations with the Arecibo planetaryradar system on 15 dates from 2017 June 2 to July 10unambiguously revealed the roughly equal-size components ofthe binary system, only the third such system known among thenear-Earth asteroids after (69230) Hermes (Margot et al., 2003;IAUC 8227) and 1994 CJ1 (Taylor et al., 2014; DPS 46, #409.03)out of more than 50 known near-Earth multiple-asteroid systems.Preliminary diameter estimates from radar images are no morethan 1 km in the longest dimension for both components. Imagesat different orientations suggest elongated shapes with the longaxes aligned, i.e., face-locked synchronous rotation, and anorbital period commensurate with the optical lightcurve period.The maximum observed separation between the components of2.4 km places a lower limit on the semimajor axis of the system,though the projection effect should be minimal given the eclipsing

nature of the lightcurves. Combined with the above upper limit onthe diameters, the implied density of the system could be lessthan 1 g/cc, though the actual value will be sensitive to the trueelongation of the shapes. Spectra of the system between 0.7 and5.1 microns obtained with the NASA Infrared Telescope Facilityon four dates between 2017 May 27 and July 19 suggest a Bus-DeMeo taxonomic type of S or Sq transitioning to a spectrumdominated by thermal emission beyond 3.5 microns with littlevariation over the two-month span of observations.

Author(s): Patrick A. Taylor , Anne Virkki , Brian Warner ,Amadeo Aznar , Ellen S. Howell , Ronald J. Vervack , Jenna L.Crowell , Mary Hinkle , Flaviane Venditti , Luisa FernandaZambrano-Marin , Betzaida Aponte-Hernandez , Edgard G.Rivera-Valentin , Sriram Saran Bhiravarasu , Carolina RodriguezSanchez-Vahamonde , Alan William Harris , Yanga R.Fernandez , Sean E. MarshallInstitution(s): 1. Arecibo Observatory, 2. Cornell University, 3.MoreData!, 4. Observatorio Isaac Aznar, 5. The Johns HopkinsUniversity Applied Physics Laboratory, 6. University of Arizona,7. University of Central Florida

204.03 – Planetary surface characterization fromdual-polarization radar observationsWe present a new method to investigate the physical properties ofplanetary surfaces using dual-polarization radar measurements.The number of radar observations has increased radically duringthe last five years, allowing us to compare the radar scatteringproperties of different small-body populations and compositionaltypes. There has also been progress in the laboratory studies ofthe materials that are relevant to asteroids and comets. In a typical planetary radar measurement a circularly polarizedsignal is transmitted using a frequency of 2380 MHz (wavelengthof 12.6 cm) or 8560 MHz (3.5 cm). The echo is receivedsimultaneously in the same circular (SC) and the opposite circular(OC) polarization as the transmitted signal. The delay anddoppler frequency of the signal give highly accurate astrometricinformation, and the intensity and the polarization are suggestiveof the physical properties of the target's near-surface. The radar albedo describes the radar reflectivity of the target. Ifthe effective near-surface is smooth and homogeneous in thewavelength-scale, the echo is received fully in the OC polarization.Wavelength-scale surface roughness or boulders within theeffective near-surface volume increase the received echo power inboth polarizations. However, there is a lack in the literaturedescribing exactly how the physical properties of the target affectthe radar albedo in each polarization, or how they can be derivedfrom the radar measurements. To resolve this problem, we utilize the information that thediffuse components of the OC and SC parts are correlated whenthe near-surface contains wavelength-scale scatterers such asboulders. A linear least-squares fit to the detected values of OCand SC radar albedos allows us to separate the diffusely scatteringpart from the quasi-specular part. Combined with the spectro-photometric information of the target and laboratory studies ofthe permittivity-density dependence, the method provides us witha new way to characterize the density or porosity of the the fine-grained regolith layer, and distinguish it from the centimeter-to-meter-scale boulders. We present the application of the methodto asteroids, comets, and the Galilean moons.

Author(s): Anne VirkkiInstitution(s): 1. Arecibo Observatory/USRAContributing team(s): Planetary Radar team of the AreciboObservatory

204.04 – The Mission Accessible Near-Earth ObjectSurvey (MANOS): Project StatusThe Mission Accessible Near-Earth Object Survey (MANOS) is aphysical characterization survey of sub-km, low delta-v, newly

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discovered near-Earth objects (NEOs). MANOS aims to collectastrometry, lightcurve photometry, and reflectance spectra for arepresentative sample of these important target of opportunityobjects in a rarely observed size range. We employ a diverse set oflarge aperture (2-8 meter) telescopes and observing modes(queue, remote, classical) to overcome the challenge of observingfaint NEOs moving at high non-sidereal rates with shortobserving windows. We target approximately 10% of newlydiscovered NEOs every month for follow-up characterization.

The first generation MANOS ran from late 2013 to early 2017,using telescopes at Lowell Observatory, NOAO, and theUniversity of Hawaii. This resulted in the collection of data forover 500 targets. These data are continuing to provide newinsights into the NEO population as a whole as well as forindividual objects of interest. Science highlights includeidentification of the four fastest rotating minor planets found todate with rotation periods under 20 seconds, constraints on thedistribution of NEO morphologies as quantified by de-biasedestimates for lightcurve-derived axis ratios, and thecompositional distribution of NEOs at sizes under 100 meters.

The second generation MANOS will begin in late 2017 and willemploy much of the same strategies while continuing to build acomprehensive dataset of NEO physical properties. This will growthe MANOS sample to ~1000 objects and provide the means tobetter address key questions related to understanding thephysical properties of NEOs, their viability as exploration missiontargets, and their relationship to Main Belt asteroids andmeteorites. This continuation of MANOS will include anincreased focus on spectroscopic observations at near-IRwavelengths using a new instrument called NIHTS (the Near-Infrared High-Throughput Spectrograph) at Lowell Observatory’s4.3m Discovery Channel Telescope.

We will present key results from the first generation survey andcurrent status and plans for the second generation survey.MANOS is supported by the NASA SSO/NEOO program.

Author(s): Nicholas Moskovitz , Audrey Thirouin , MichaelMommert , Cristina A. Thomas , Brian Skiff , David Polishook ,Brian Burt , David E. Trilling , Francesca E. DeMeo , Richard PBinzel , Eric J. Christensen , Mark Willman , Mary HinkleInstitution(s): 1. Lowell Observatory, 2. MIT, 3. NorthernArizona University, 4. PSI, 5. UA, 6. UCF, 7. UH, 8. WeizmannInstitute

204.05 – Rapid-Response Characterization ofNear-Earth Asteroids Using KMTNet-SAAOWe present here VRI spectrophotometry of 39 near-Earthasteroids (NEAs) observed with the Sutherland, South Africa,node of the Korea Microlensing Telescope Network (KMTNet). Ofthe 39 NEAs, 19 were targeted, but because of KMTNet’s large 2deg × 2 deg field of view, 20 serendipitous NEAs were alsocaptured in the observing fields. Our rapid-response approachmeant targeted observations were performed within 44 days(median: 16 days, min: 4 days) of each NEA’s discovery date. Ourbroadband spectrophotometry is reliable enough to distinguishamong four asteroid taxonomies and we were able to confidentlycategorize 31 of the 39 observed targets as either a S-, C-, X- or D-type asteroid. Our data suggest that the ratio between “stony” S-type NEAs and “not- stony” (C+X+D)-type NEAs, with Hmagnitudes between 15 and 25, is roughly 1:1. Additionally, wereport ~1-hour light curve data for each NEA. Of the 39 targets,we were able to resolve the complete rotation period andamplitude for six and place lower limits for the remaining targets.

Based on the success of this pilot study we plan to continueKMTNet observations but also make use of Lesedi, a new 1-meterremotely-operable telescope also situated in Sutherland, toperform similar spectrophotometric observations in the future. Asbefore, we plan to target newly discovered NEAs in order tocontinue the rapid-response approach. With Lesedi, observationswill take place throughout the year and we plan to include smallerNEAs (larger H magnitudes) in our sample. We will also increase

the observed duration of each NEA to 2-3 hours so we are morelikely to observe a complete rotation period for our observedNEAs. This study was facilitated by observations made at the SouthAfrican Astronomical Observatory (SAAO) and this work ispartially supported by the South African National ResearchFoundation (NRF). This work is supported in part by the NationalAeronautics and Space Administration (NASA) under grantnumber NNX15AE90G issued through the SSO Near Earth ObjectObservations Program and in part by a grant from NASA’s Officeof the Chief Technologist.

Author(s): Nicolas Erasmus , Michael Mommert , David E.Trilling , Amanda A. Sickafoose , Carel van Gend , Joseph L.Hora , Hannah L WortersInstitution(s): 1. Department of Physics and Astronomy,Northern Arizona University, 2. Harvard-Smithsonian Centerfor Astrophysics, 3. South African Astronomical Observatory

204.06 – Spin State of Returning Fly-by Near EarthAsteroid 2012 TC4The ten-meter class near-Earth asteroid 2012 TC4 will make aclose approach to the Earth on October 12, 2017. As of July 2017,the close approach distance ranges from 0.003 to 0.64 lunardistances (LD) with a nominal value of 0.23 LD. However this isthe second observable close approach that this object has madesince its discovery. In particular, broadband photometry wasobtained for 2012 TC4 on 10 and 11 October 2012 using theMagdalena Ridge Observatory (MRO) 2.4-meter telescope. Aperiodicity of ~12.2 minutes was immediately evident in the time-series data, which was in agreement with the reported values ofPolishook (2013), Odden et al. (2012), Warner (2013), andCarbognani (2014). The lightcurve displays an amplitude of ~0.9magnitude, which implies that it is highly elongated with an axialratio of a/b>2.3. However, a second period is also clearly evidentin the MRO data, indicating that the asteroid is in a state of non-principle axis rotation. The nature of its orbit has made 2012 TC4 an attractive Earth-impacting asteroid surrogate for an exercise testing thecapabilities of the scientific and emergency response communities(Reddy, 2017). For this reason, it is anticipated that considerableresources, including MRO, will be utilized to take advantage ofthe 2017 flyby to study this asteroid. Here, we present the detailsof the tumbling nature of this fast-spinning object observedduring the October 2012 discovery apparition. These data wereacquired before closest approach in 2012 where the asteroid camewithin 0.25 lunar distances of Earth. Therefore, this analysis willbe discussed in the context of the spin state observations plannedfor early October 2017 at MRO, for which preliminary results willalso be reported. In particular, comparison of the observedrotation state from the two apparitions can be indicative of anyeffects of Earth’s gravity during the 2012 flyby. References: Odden, C.E., Verhaegh, J.C., McCullough, D.G., and Briggs, J.W.(2013). Minor Planet Bul. 40, 176-177. Warner, B.D. (2013). Minor Planet Bul. 40, 71-80. Polishook, D. (2013). Minor Planet Bul. 40, 42-43. Carbognani, A. (2014). Minor Planet Bul. 41, 4-8. Reddy, V. (2017), AMOS SSA Technical Conference, Maui, HI.

Author(s): William Ryan , Eileen V. RyanInstitution(s): 1. NM Tech/MRO

204.07 – Ground-based Characterization of EarthQuasi Satellite (469219) 2016 HO3(469219) 2016 HO3 is a small, <100 meter-size, near-Earth object(NEO) that while orbiting the Sun, also appears to circle aroundthe Earth just beyond the Hill sphere as a Earth quasi-satellite.Only five quasi-satellites have been discovered so far, but 2016HO3 is the most stable of them. The provenance of this object isunknown. On timescales of many centuries, 2016 HO3 remains

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within 38-100 lunar distance from us making it a prime target forfuture robotic and human exploration, provided it can beestablished it is indeed a natural object. In an effort to constrainits rotation period and surface composition, we observed 2016HO3 on April 14 and 18 2017 (UTC) with the Large BinocularTelescope (LBT) and the Discovery Channel Telescope (DCT). Wederive a rotation period of about 28 minutes based on ourlightcurve observations. We obtained low-resolution (R ∼ 150 −500) spectra of 2016 HO3 on 2017 April 14 (UTC) using the pairof MODS spectrographs mounted at the direct Gregorian foci ofthe LBT, obtaining the entire spectrum from 0.39-0.97 micronssimultaneously. The visible wavelength spectrum shows a sharprise in reflectance between 0.4-0.65 microns with a broad plateaubeyond. The scatter near 0.8 microns makes it challenging toconfirm the presence of a silicate absorption band at ~1 micron.Color ratios derived from the spectrum all suggest an S taxonomictype. We also derive an updated diameter of 36 meters for 2016HO3 using an absolute magnitude of 24.3 and S-type albedo of0.25. The derived rotation period and the spectrum are notuncommon amongst small NEOs, suggesting that 2016 HO3 is anatural object of similar provenance to other small NEOs. NASANear-Earth Object Observations Program Grant NNX17AJ19G(PI: Reddy) funded parts of this work.

Author(s): Vishnu Reddy , Olga Kuhn , Audrey Thirouin , AlConrad , Renu Malhotra , Juan A Sanchez , Christian VeilletInstitution(s): 1. Lowell Observatory, 2. Planetary ScienceInstitute, 3. University of Arizona

204.08 – Lunar impact flashes - tracing the NEOsize distributionAlmost 20 years ago, we started to monitor the lunar surface withsmall telescopes to detect light flashes resulting from thehypervelocity collisions of meteoroids. The initial purpose was tounderstand the flux of impactors on Earth. The estimation of theflux of near Earth Objects (NEOs) is important not only for theprotection of the human civilisation (meter-sized, seeChelyabinsk event in 2013), but also for the protection of thespace assets (cm-sized objects). Apart from the NEO flux, thelunar surface helps the study of the impact events per se. TheEuropean Space Agency (ESA) is directing and funding lunarobservations at 1.2 m Kryoneri telescope in Peloponnese, Greece.This telescope is equipped with a dichroic beam-splitter thatdirects the light onto two sCMOS cameras, that observe in visibleand infrared wavelengths, using Rc and Ic Cousin filtersrespectively. Currently it is the largest telescope in the world thatperforms dedicated lunar impact flashes observations. Wepresent the first flash observations in two bands, allowing us tomeasure flash temperatures for the first time. We find that thetemperatures have a range that agrees with the theoreticalapproaches. Since the temperature can now be calculated, wehave a more accurate estimation of the impactor’s mass and thesize of the radiated ejecta plume. Having the Moon as a large-scale laboratory, new horizons are settowards the understanding of the nature of impacts, theimpactor's material type and the energy partitioning, that is aconstant puzzle in impact studies. This can now happen as moreimpact parameters can be determined and combined, such as theimpactor’s mass and speed, flash luminosity, radiating volume,crater size when applicable etc. Future statistics can determinethe different lunar regolith properties at different impact sites,especially during a meteoroid stream where the impactors share acommon origin and possibly composition.

Author(s): Chrysa Avdellidou , Detlef KoschnyInstitution(s): 1. European Space Agency- ESTECContributing team(s): NELIOTA team

204.09 – Using Cross Correlation for EvaluatingShape Models of AsteroidsThe Origins, Spectral Interpretation, Resource Identification, andSecurity-Regolith Explorer (OSIRIS-REx) sample return missionto Bennu will be using optical navigation during its proximityoperations. Optical navigation is heavily dependent upon having

an accurate shape model to calculate the spacecraft's position andpointing. In support of this, we have conducted extensive testingof the accuracy and precision of shape models. OSIRIS-REx willbe using the shape models generated by stereophotoclinometry(Gaskell, 2008). The most typical technique to evaluate models is to subtract twoshape models and produce the differences in the height of eachnode between the two models. During flight, absolute accuracycannot be determined; however, our testing allowed us tocharacterize both systematic and non-systematic errors. We havedemonstrated that SPC provides an accurate and reproducibleshape model (Weirich, et al., 2017), but also that shape modelsubtraction only tells part of the story. Our advanced shape model evaluation uses normalized cross-correlation to show a different aspect of quality of the shapemodel. In this method, we generate synthetic images using theshape model and calculate their cross-correlation with images ofthe truth asteroid. This technique tests both the shape model'srepresentation of the topographic features (size, shape, depth andrelative position), but also estimates of the surface's albedo. Thisalbedo can be used to determine both Bond and geometric albedoof the surface (Palmer, et al., 2014). A high correlation scorebetween the model's synthetic images and the truth images showsthat the local topography and albedo has been well representedover the length scale of the image. A global evaluation, such asglobal shape and size, is best shown by shape model subtraction.

Author(s): Eric Palmer , John Weirich , Olivier Barnouin ,Tanner Campbell , Diane LambertInstitution(s): 1. Planetary Science Institute, 2. The JohnsHopkins University Applied Physics Laboratory, 3. TheUniversity of Arizona

204.10 – Thermally induced rock breakdown onasteroid ItokawaOn airless bodies of the inner solar system, changes in surfacetemperature due to insolation yield thermal cracking of rocks.This has been considered as a leading cause of rock breakdown,crater degradation and regolith production. However, it is poorlyunderstood what thermal conditions are actually required tocause damage in rocks. Here we present a new evidence ofthermally induced rock breakdown found on asteroid Itokawa.We analyzed the visible and near-infrared spectra of Shirakamiand Muses-C regio, both of which are located within the concavepart of Itokawa, and found that less space weathered debrisgenerated from Shirakami are deposited on Muses-C regio. Inaddition, we performed thermophysical analysis to calculate thethermal conditions of Itokawa surface, which indicates that therock breakdown on Shirakami would be caused by rapidtemperature changes related to shadowing.

Author(s): Kohei Kitazato , Naru Hirata , HirohideDemura , Tomoki Inasawa , Masanao Abe , Yukio Yamamoto ,Akira Miura , Jun'ichiro KawaguchiInstitution(s): 1. Japan Aerospace Exploration Agency, 2.University of Aizu

204.11 – Regolith on Super Fast RotatorsThe current understanding of small asteroids in the Solar Systemis that they are gravitational aggregates held together bygravitational, cohesive and adhesive forces. Results from theHayabusa mission to Itokawa along with in situ, thermal andradar observations of asteroids have shown that they can becovered in a size distribution of grains that spans from microns totens of meters. Before the Hayabusa mission, it was generallythought that smaller asteroids would likely be “regolith-free,” dueto impact seismic shaking removing the loose covering. Given theregolith-rich surface of that body, it is now an open questionwhether even smaller bodies, down to a few meters in size, couldalso retain regolith covering. The question is especiallycompelling for the small-fast rotators, whose surface centripetalaccelerations exceed their gravitational attraction. When thephysical theory of cohesion is considered, it becomes possible for

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small-fast rotators to retain regolith.

We use a Soft-Sphere discrete element method (SSDEM) code tosimulate a longitudinal slice of a spherical monolith covered bycohesive regolith. The simulations are carried out in the bodyframe. Tensile strength is varied to span the observed strength ofasteroids and spin rate is elevated in small steps until themajority of regolith is removed from the surface. The simulationsshow that under an increasing spin rate (such as due to the YORPeffect), the regolith covering on an otherwise monolithic asteroidis preferentially lost across certain regions of the body. In general,regolith from the mid latitudes is the first to fail at high spin rates.This failure happens either by regolith flowing towards theequator or by detachment of large coherent chunks of materialdepending on the tensile strength of the regolith. Regolith fromthe equator region fails next, usually by the detachment of largepieces. Regolith from the poles stays in place unless the spin ratesare extremely high. With these results we derive a scaling law thatcan be used to determine whether observed small asteroids couldretain surface regolith of a given size. The implications of this forthe interpretation of spectral observations of small asteroids arediscussed.

Author(s): Diego Paul Sanchez Lana , Daniel J. ScheeresInstitution(s): 1. University of Colorado Boulder

204.12 – Cohesion of Mm- to Cm-Sized AsteroidSimulant Grains: An Experimental StudyThe regolith covering the surfaces of asteroids and planetarysatellites is very different from terrestrial soil particles andsubject to environmental conditions very different from what isfound on Earth. The loose, unconsolidated granular material hasangular-shaped grains and a broad size distribution. On smalland airless bodies (<10 km), the solar wind leads to a depletion of

fine grains (<100µm) on the surface. Ground observations of thetwo asteroids currently targeted by spacecraft, Ryugu (Hayabusa-2) and Bennu (OSIRIS-REx), indicate that their surfaces could becovered in mm- to cm-sized regolith grains. As these small bodieshave surface gravity levels below 10 g, g being the Earth surfacegravity, the cohesion behavior of the regolith grains will dictatethe asteroid’s surface morphology and its response to impact orspacecraft contact. Previous laboratory experiments on low-velocity impacts intoregolith simulant with grain sizes <250 µm have revealed atransition of the grain behavior from a gravity-dominated regimeto a cohesion-dominated regime when the local gravity levelreaches values below 10 g. This is in good agreement withanalytical and simulation studies for these grain sizes. From theexpected grain sizes at the surfaces of Ryugu and Bennu, we havenow focused on larger grain sizes ranging from mm to cm. Wehave carried out a series of experiments to study the cohesionbehavior of such larger grains of asteroid regolith simulant. Thesimulant used was CI Orgueil of Deep Space Industries.Experiments included laboratory tabletop avalanching,compression and shear force measurements, as well as low-velocity impacts under microgravity. Our goal is to determine if the grain size distribution has aninfluence on the cohesion behavior of the regolith and if we canvalidate numerical simulation results with experimentalmeasurements. We will discuss the implications of our results forsample return or landing missions to small bodies such asasteroids or Martian moons.

Author(s): Julie Brisset , Joshua E. Colwell , AdrienneDove , Stephanie Jarmak , Seamus AndersonInstitution(s): 1. University of Central Florida

205.01 – Hubble’s Global View of Jupiter Duringthe Juno MissionWith two observing programs designed for mapping clouds andhazes in Jupiter's atmosphere during the Juno mission, theHubble Space Telescope is acquiring an unprecedented set ofglobal maps for study. The Outer Planet Atmospheres Legacyprogram (OPAL, PI: Simon) and the Wide Field Coverage forJuno program (WFCJ, PI: Wong) are designed to enable frequentmulti-wavelength global mapping of Jupiter, with many mapstimed specifically for Juno’s perijove passes. Filters spanwavelengths from 212 to 894 nm. Besides offering global viewsfor Juno observation context, they also reveal a wealth ofinformation about interesting atmospheric dynamical features.We will summarize the latest findings from these global mappingprograms, including changes in the Great Red Spot, zonal windprofile analysis, and persistent cyclone-generated waves in theNorth Equatorial Belt.

Author(s): Amy A. Simon , Michael H. Wong , Glenn S.Orton , Richard Cosentino , Joshua Tollefson , PerianneJohnsonInstitution(s): 1. Jet Propulsion Lab, 2. NASA's GSFC, 3. NewMexico Tech, 4. U. California Berkeley, 5. USRA

205.02 – Characterization of the Great Red Spotfrom Observations by Juno and the Earth-BasedSupporting CampaignOn July 11, 2017, the Juno spacecraft made a close approach toJupiter, passing over the center of Jupiter’s Great Red Spot(GRS). We summarize some of the results from Juno andsupporting Earth-based measurements over a broad spectralrange. Near-infrared images show that the GRS has higher-altitude particles than anywhere else outside polar regions, andthat the darkest red center has the highest-altitude particleswithin the GRS. This region has darker swirl-like features andlittle detectable rotational motion. The red region forming thebulk of the GRS has both dark and light swirls and counter-clockwise winds that peak toward its periphery. JunoCam images,

resolving down to ~6-7 km per pixel, shows very small, pinkfeatures that look like thunderstorm clouds in clusters on top ofthe brighter swirls. They are similar in morphology to whitishfeatures that can be seen in zones north and south of the GRS.Close to the terminator, shadows some 7-12 km in lengthassociated with these features can be resolved. A train ofmesoscale gravity waves with ~70 km spacing spans a length ofover 1,000 km near the northern periphery of the GRS between15.8° and 15.9°S (planetocentric). Thermal-emission images in 5-µm and 8.7-µm spectral windows show most of the GRS as coldwith high clouds, surrounded by a visibly-dark warm peripherythat is consistent with being relatively clear. Longer-wavelengththermal observations indicate that the GRS is one of the coldestregions on the planet in the upper troposphere with indirectchemical indicators of vertical motions (e.g. para-H , PH )consistent with prevailing upwelling motion. NH is notenhanced with respect to the regions outside the GRS, most likelybecause its colder temperatures cause it to condense deeper thanit does outside the GRS. A region immediately south of the GRS isanomalously warmer than elsewhere at the same latitude. TheMicrowave Radiometer (MWR) data are consistent with shorter-wavelength thermal-emission observations sensitive to the NHcondensation level; they are currently being examined forindications of deep structure and depth.

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Author(s): Glenn S. Orton , Candice Hansen , Michael A.Janssen , Scott Bolton , Shannon Brown , Gerald Eichstaedt ,John Rogers , Andrew P. Ingersoll , Cheng Li , Thomas W.Momary , Fachreddin Tabataba-Vakili , Leigh Fletcher ,Takuya Fujiyoshi , Thomas K. Greathouse , Yasumasa Kasaba ,Amy A. Simon , James Andrew Sinclair , Andrew W. Stephens ,Michael H. Wong , Padraig Donnelley , Agustin M. Sanchez-Lavega , Ricardo HuesoInstitution(s): 1. British Astronomical Association, 2.California Institute of Technology, 3. Gemini Observatory, 4.Independent Scholar, 5. JPL, 6. NASA Goddard Space FlightCenter, 7. Planetary Science Institute, 8. Southwest ResarchInstitute, 9. Subaru Telescope, 10. Tohoku University, 11.Universidad del Pais Vasco, 12. University of California, 13.University of LeicesterContributing team(s): The Juno-Support Observing Team

205.03 – Radiative Transfer Analysis of Neptune’sNew Dark VortexA new dark spot on Neptune was discovered in late 2015, named:"SDS-2015" for "Southern Dark Spot discovered in 2015".Subsequent observations from Hubble Space Telescope Mid-Cycle 23 (PI: Wong) and the Outer Planetary Atmospheres Legacy(OPAL) programs (PI: Simon-Miller) took the first multispectraldata over multiple viewing geometries of a Neptunian dark spot,spanning wavelengths from 336 to 763nm. SDS-2015 is visible atblue wavelengths, with contrast from the background atmospherepeaking at 467nm. In this abstract, we present a radiative transferanalysis of the dark spot and surrounding backgroundatmosphere. We summarize our retrieved properties of Neptune'sbackground atmosphere, including its aerosol structure andmethane profile, and compare our findings in the opticalwavelengths to those in the near-infrared. We then discussvarious hypotheses about the make up of SDS-2015 and itsinteraction with the background atmosphere.

Author(s): Joshua Tollefson , Statia H. Luszcz-Cook ,Michael H. Wong , Imke de PaterInstitution(s): 1. American Museum of Natural History, 2.University of California Berkeley

205.04 – Ammonia in Jupiter’s troposphere fromhigh-resolution 5-micron spectroscopyJupiter's tropospheric ammonia (NH ) abundance is studiedusing spatially-resolved 5-micron observations from CRIRES, ahigh-resolution spectrometer at the Very Large Telescope in 2012.The high resolving power (R=96,000) allows the line shapes ofthree NH absorption features to be resolved. These threeabsorption features have different line strengths and probeslightly different pressure levels, and they can therefore be usedto constrain the vertical profile of NH in the 1-4 bar pressurerange. The instrument slit was aligned north-south alongJupiter's central meridian, allowing us to search for latitudinalvariability. The CRIRES observations do not provide evidence forbelt-zone variability in NH , as any spectral differences can beaccounted for by the large differences in cloud opacity betweenthe cloudy zones and the cloud-free belts. However, we do findevidence for localised small-scale variability in NH . Specifically,we detect a strong enhancement in NH on the southern edge ofthe North Equatorial Belt (4-6°N). This is consistent with the‘ammonia plumes’ observed by Fletcher et al. (2016,doi:10.1016/j.icarus.2016.06.008) at the 500-mbar level using10-micron observations from TEXES/IRTF, as well as withmeasurements by Juno’s Microwave Radiometer (Li et al. 2017,doi:10.1002/2017GL073159).

Author(s): Rohini Giles , Leigh Fletcher , Patrick Irwin ,Glenn S. Orton , James Andrew SinclairInstitution(s): 1. Jet Propulsion Laboratory, 2. University ofLeicester, 3. University of Oxford

205.05 – Variation in the Water and AmmoniaAbundance in Jupiter’s North Equatorial Belt

We used iSHELL on NASA’s Infrared Telescope Facility andNIRSPEC on the Keck telescope concurrent with Juno perijoves4-6 between February and May 2017 to obtain 5-micron spectraof Jupiter. Here we will focus on observations of the NorthEquatorial Belt. Spectrally resolved line profiles of CH D, NH ,and H O probe the 1 to 8-bar level of Jupiter’s troposphere. Thisoverlaps with the weighting functions for several channels ofJuno’s microwave radiometer. The profile of the CH D lines at4.66 microns is very broad in Hot Spots due to collisions with upto 8 bars of H , where unit optical depth occurs due to collision-induced H opacity. The extreme width of these CH D featuresimplies that the Hot Spots that we observed do not havesignificant cloud opacity for P > 2 bars. We will discuss theabundance of NH and gaseous H O within Hot Spots and otherregions near the longitude of perijove for each Juno encounter.We had dry nights on Mauna Kea and a sufficient Doppler shift todetect H O. We will compare line wings to derive H O profiles inthe 2 to 6-bar region. NEB Hot Spots are depleted in NH withrespect to adjacent regions, especially for P < 2 bars. NEB HotSpots are highly depleted in H O for P < 5 bars.

Author(s): Gordon L Bjoraker , Imke de Pater , Michael H.Wong , Mate Adamkovics , Tilak Hewagama , Glenn OrtonInstitution(s): 1. Clemson Univ, 2. JPL, 3. NASA/GSFC, 4. UMaryland, 5. UC Berkeley

205.06 – Cassini limb images of hazes in Saturn’snorthern hemisphereWe have used high resolution Cassini ISS images of the limb ofSaturn to study the vertical distribution, altitude location,thickness and optical properties of the haze layers in the northernhemisphere (1°S to 82°N) in 2013 and 2015. The images cover anample spectral range from the ultraviolet (UV1 filter, 264 nm) tothe near infrared (CB3 filter, 938 nm) including methaneabsorption bands at 619 nm, 724 nm and 890 nm. Spatialresolution ranges from 1.6 to 13 km/pixel depending onwavelength and latitude. Three latitude bands were selected forthe analysis according to the background zonal wind profilemeasured at cloud level and known dynamical activity: (a) NorthPolar Region encompassing the Hexagon latitude (74°N); (b)Mid-latitudes (45°N-52°N), and (3) Equator (1°N-3°S). The bestdefined haze structures and most extended haze layers werefound at the latitude of the Hexagon. Up to 6-8 haze layersextending up to 400 km in altitude above clouds (in the pressurerange from about 0.7 bar to 0.1 mbar) were detected. The verticalthickness of the layers is in the range 3-15 km compared to thescale height which is about 40 km. The spectral reflectivity isrelatively uniform between the layers in the blue and redcontinuum wavelengths coming from the backward lightscattering from the haze particles, while the brightness in themethane bands (relative to red continuum) and in the ultravioletshows the effects of methane absorption and Rayleigh scatteringby the gas, respectively. At mid-latitudes 3-4 haze layers arefound spanning up to altitudes 200 km above the clouds. At theEquator 5-6 layers are found extending up to altitudes 250 kmabove the clouds (up to 2 mbar in pressure level) in a region ofgreat dynamical interest because of the particular structure of thezonal winds and their known oscillations. We comment on thepossible nature of the haze layers on the basis of condensingspecies and photochemistry.

Author(s): Agustin M. Sanchez-Lavega , Daniel Garcia ,Teresa del Rio-Gaztelurrutia , Antonio Garcia-Muñoz , SantiagoPerez-Hoyos , Ricardo HuesoInstitution(s): 1. Universidad del Pais Vasco UPV/EHU, 2.Zentrum für Astronomie und Astrophysik, TechnischeUniversität Berlin

205.07 – Clouds and Hazes in Saturn's North PolarVortex: New Results from Cassini/VIMS High-Spatial Resolution Spectral Imagery on the FirstGrand Finale Pass

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High-spatial-resolution spectral images of Saturn's polar regionobtained during the first Grand Finale pass on April 26, 2017 bythe Cassini/Visual Infrared Mapping Spectrometer (VIMS) reveala variety of cloud/haze structures exhibiting distinctively differentcolors in the near-infrared, corresponding to a variety of cloudcompositions, altitudes and thicknesses. Two spectral images inparticular, obtained from altitudes of 110,000 km and 69,600 kmabove the cloudtops - corresponding to VIMS pixel resolutions of55 and 34 km, some five times better than has been obtained byVIMS on any previous orbit - reveal small (~ 200 km across)discrete clouds remarkably enhanced in 3-micron absorptioncompared to nearby features, indicating enhanced ammoniaand/or perhaps ammonia hydrosulfide or water ice absorptions.The ~2000-km-wide eye of the vortex in which these discreteammonia/water ice clouds are embedded is surprisingly dark,exhibiting reflectivities less than one-third of those displayed bythe small discrete clouds at all near-IR continuum wavelengths.However, at 5 microns, this contrast is reversed with the vortexeye emanating eight times the thermal flux of the embeddedclouds. Taken together, the small reflectivity and large 5-micronthermal transmission indicate that the eye is an optically-thinhaze/cloud region, nearly devoid of aerosols. From a dynamicalpoint of view, the stark contrast between the reflectively dark,nearly-aerosol-free polar "eye" - indicative of downwellingprocesses - and the clouds of 3-micron absorbers embeddedwithin it - indicative of powerful upwelling of materials from thedepths of Saturn perhaps 50-200 km below - is puzzling,revealing that a remarkable range of vertical dynamical processesoccur in Saturn's north polar region over relatively small spatialscales. Quantitative results for these various clouds, includingtheir compositional characteristics, altitudes, mass loading, andwavelength-dependent opacities will be presented.

Author(s): Kevin H. Baines , Lawrence A. Sromovsky ,Patrick M. Fry , Thomas W. Momary , Robert H Brown , BonnieJ. Buratti , Roger Nelson Clark , Philip D. Nicholson ,Christophe SotinInstitution(s): 1. Cornell University, 2. NASA/Jet PropulsionLaboratory, 3. Planetary Science Institute, 4. University ofArizona, 5. University of Wisconsin-Madison

205.08 – South Polar Ammonia Clouds on Saturn°Most of Saturn is covered by a thick cloud layer of unknowncomposition. Evidence of the underlying NH ice cloud (its strong3-μm absorption signature) had so far been seen only inassociation with lightning storms, including the Great Storm of2010-2011 (Sromovsky et al. 2013, Icarus 226, 402-418), near 35°N planetocentric latitude, and much smaller storms located near36° S in the Storm Alley region (Baines et al. 2009, Planet. &Space Sci. 57, 1650-1658). In the Great Storm, NH ice reachedthe visible cloud tops. The Storm Alley clouds have more subtle 3-μm signatures, which is consistent with ammonia ice reachinginto but not fully penetrating the upper cloud (Sromovsky et al.2017, Icarus submitted). The presence of 3-μm absorptionfeatures in the south polar region is surprising because there is noassociated lighting that would indicate deep convection.Radiation transfer modeling of October 2006 VIMS spectra ofthese features yields good fits with a stacked structure of a thinstratospheric haze, a physically thin and optically thin (~0.2optical depths at 2 μm) layer of non-absorbing particles, amoderate layer of NH ice particles (r=2 μm, ~2 optical depths)near 550 mbar, then a clear region down to about 2 bars, whichmarks the top of a very optically thick layer of NH SH particles,which provides a needed strong reduction in thermal emission inthe 5-μm window. The structure of neighboring clouds differsdramatically in the NH SH layer, which has a much lower opticaldepth and has a cloud top 1 bar deeper. But the ammonia layer isthe main modulator of pseudo continuum I/F in reflectedsunlight. That layer has an optical depth of about 1.3 inbackground clouds, but almost double that in the brightestclouds. What makes the 3-μm absorption of the NH ice layermore apparent in these polar clouds is the reduced optical depthof the upper cloud layer, which is an order of magnitude less thanin other regions on Saturn, perhaps because of polardownwelling.

The authors acknowledge support from NASA CDAPS GrantNNX15AL10G.

Author(s): Lawrence A. Sromovsky , Kevin H. Baines ,Patrick M. FryInstitution(s): 1. Univ. of Wisconsin, Madison

205.09 – Cassini/CIRS Observations of Saturn’sPolar Vortices from Proximal Orbit ObservationsThe proximal orbit phase of the Cassini mission, with periapsesinside the inner edge of the rings, has allowed observations ofSaturn’s atmosphere with unprecedented spatial resolution.During the periapse periods on 26 April and 29 June 2017, theComposite Infrared Spectrometer (CIRS) performed scans overboth the north and south poles with a spatial resolution betterthan 0.2° of latitude, over a factor of 4 better resolution thanprevious observations. A further observation of the south pole isplanned on 20 Aug 2017. Previous thermal infrared observations of Saturn’s poles [1,2]showed a compact hot spot in the upper troposphere at each pole,roughly coincident with the hurricane-like polar vortex seen invisible imaging [3]. Preliminary results from the proximal orbitscans of the north pole, near summer solstice, show that in theupper troposphere, the meridional temperature gradientincreases sharply at about 89°N, with the temperature increasingby ~5K between 89°N and the pole, with the temperaturegradient persisting all the way to the pole within the spatialresolution of the observation. In the northern stratosphere, thepolar hot spot is broader than in the troposphere, extending to~86°N at 4 mbar, and disappearing into the general meridionalgradient at 1 mbar. [1] G. S. Orton and P. A. Yanamadra-Fisher, Science 307, 696 [2] L. N. Fletcher et al., Science, 319, 79 [3] U. A. Dyudina et al., Icarus, 202, 240.

Author(s): Richard Achterberg , Gordon L. Bjoraker ,Brigette E. Hesman , F. Michael FlasarInstitution(s): 1. NASA/GSFC, 2. STScI, 3. University ofMaryland

205.10 – Dynamical analysis of Jovian polarobservations by JunoThe JunoCAM and JIRAM instruments onboard the Junospacecraft have generated unparalleled observations of the Jovianpolar regions. These observations reveal a turbulent environmentwith an unexpected structure of cyclonic polar vortices. Wemeasure the wind velocity in the polar region using correlationimage velocimetry of consecutive images. From this data, wecalculate the kinetic energy fluxes between different length scales.An analysis of the kinetic energy spectra and eddy-zonal flowinteractions may improve our understanding of the mechanismsmaintaining the polar macroturbulence in the Jovian atmosphere.

Author(s): Fachreddin Tabataba-Vakili , Glenn S. Orton ,Alberto Adriani , Gerald Eichstaedt , Davide Grassi , Andrew P.Ingersoll , Cheng Li , Candice Hansen , Thomas W. Momary ,Maria Luisa Moriconi , Alessandro Mura , Peter L Read , JohnRogers , Roland M B YoungInstitution(s): 1. British Astronomical Association, 2.California Institute of Technology, 3. INAF-Istituto di Astrofisicae Planetologia Spaziali, 4. Independent Scholar, 5. JetPropulsion Laboratory, 6. Planetary Science Institute, 7.University of Oxford

205.11 – Dynamics and Morphology of Saturn’sNorth Polar Region During Cassini’s Final YearWe present an analysis of Saturn’s north polar region utilizingCassini ISS images captured in visible and near-infraredwavelengths during late 2016 and 2017, including imagescaptured during Cassini’s Grand Finale orbits. To measure thewind field in the region, we utilize the two-dimensional

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correlation imaging velocimetry (CIV) technique. We alsocalculate the relative vorticity and divergence from the wind field.To detect changes in the dynamics, we compare measurements ofthe wind, relative vorticity, and divergence in 2012 and 2013 withthose from 2016/2017. We also compare cloud reflectivitybetween 2012/2013 and 2016/2017 in images that show the northpole under similar illumination conditions. To detect changes incloud reflectivity, we utilize a Minnaert correction to calculate thezonal mean reflectivity as a function of latitude. Furthermore, wecompare the winds and cloud reflectivity at several wavelengthsin order to look for changes occurring at different altitudes. Ourresults indicate that while the dynamics of the north polar regionhave remained relatively stable, there have been significantmorphology changes that have resulted in dramatic colorchanges. We hypothesize that these changes are a result of theseasonal cycle and linked to the increased production ofphotochemical hazes in the atmosphere. Our work has beensupported by NASA PATM NNX14AK07G, NSF AAG 1212216,and NASA NESSF NNX15AQ70H.

Author(s): John J. Blalock , Kunio M. Sayanagi , Andrew P.Ingersoll , Ulyana A. Dyudina , Shawn Ewald , Ryan M.McCabe , Jacob Gunnarson , Justin Garland , AngelinaGallegoInstitution(s): 1. California Institute of Technology, 2.Hampton University

205.12 – Shallow water modeling of Jovian polarcyclone and vorticesJupiter’s polar atmosphere was observed for the first time by theJuno visible spectrum camera (JunoCAM) and Juno InfraredAuroral Mapper (JIRAM). Both the visible and infrared imagesshow active vortices and weather systems that are unlike anypolar regions previously seen or modeled on any of the planets inour solar system. We developed a global shallow water model on asphere with poles rotated to the equator to investigate theformation, maintenance and dynamic regimes controlling themorphology of polar cyclones and vortices. Passive Lagrangianparticles with finite life time are included to represent the clouds.We verified that a westward barotropically unstable jet canspontaneously break the axial symmetry into a polygon-shapedfigure rotating rigidly around the rotation axis as reported byprevious laboratory experiments. The number of sides of thepolygon depends on the deformation radius and is insensitive tothe initial condition. Why Jupiter’s pole is different from Saturn’sis still under investigation.

Author(s): Cheng Li , Fachreddin Tabataba-Vakili , AndrewP. IngersollInstitution(s): 1. California Institute of Technology, 2. JetPropulsion Laboratory

207.01 – Ultra High Resolution Imaging ofEnceladus Tiger Stripe Thermal Emission withCassini CIRSIn October 2015, Cassini flew within 48 km of Enceladus’ southpole. The spacecraft attitude was fixed during the flyby, but theroll angle of the spacecraft was chosen so that the remote sensinginstrument fields of view passed over Damascus, Baghdad, andCairo Sulci. The Composite Infrared Spectrometer (CIRS)instrument obtained a single interferometer scan during the flyby,using a special mode, enabled by a flight software update, whichbypassed numerical filters to improve the fidelity of theinterferograms. This generated a total of 11 interferograms, at 5contiguous spatial locations for each of the 7 – 9 micron (FP4)and 9 – 17 micron (FP3) focal planes, and a single larger field ofview for the 17 – 500 micron focal plane (FP1). Strong spikes wereseen in the interferograms when crossing each of the sulci, due tothe rapid passage of warm material through the field of view. ForFP3 and FP4, the temporal variations of the signals from the 5contiguous detectors can be used to generated 5-pixel-wideimages of the thermal emission, which show excellent agreementbetween the two focal planes. FP3 and FP4 spatial resolution,limited along track by the 5 msec time sampling of theinterferogram, and across track by the CIRS field of view, is aremarkable 40 x 40 meters. At this resolution, the tiger stripethermal emission shows a large amount of structure, includingboth continuous emission along the fractures, discrete hot spotsless than 100 meters across, and extended emission with complexstructure.

Author(s): John R. Spencer , Nicolas Gorius , CarlyHowett , Anne J. VerbiscerInstitution(s): 1. Catholic University of America, 2. SouthwestResearch Institute, 3. University of VirginiaContributing team(s): Cassini CIRS Team

207.02 – Short-Term Variability in Enceladus'PlumeThe density of solids in Enceladus' south-polar plume at altitudesabove about 50 km has been observed to vary by a factor of threebetween Enceladus' periapse and apoapse. This variability of thecombined plume on the orbital time scale supports a relationbetween tidal stress and combined eruptive activity, and containsinformation about how the fractures fail in an averaged sense, butlocal variability is still not understood.

Here we report on a sequence of three Cassini images showing a

single collimated jet transitioning from dormant to active duringa period of a few minutes. In the first image, the jet is not visible;in the subsequent images, it is seen increasing to heights of order100 km. Prior estimates of particle velocities have been based onobserving the vertical brightness profiles of steady-stateeruptions. The non-steady-state jet observations discussed hereprovide a different way of measuring velocities, as the rate ofchange in density at each altitude can be estimated (usingappropriate photometric assumptions). Moreover, the timing andlocation of the eruption contain information about the failuremechanism leading to an eruption at this particular time andplace. Other jets may also be observed activating at this time, but thedetections are less certain.

Author(s): Joseph N. Spitale , Terry Hurford , Alyssa R.RhodenInstitution(s): 1. Arizona State University, 2. Goddard SpaceFlight Center, 3. Planetary Science Institute

207.03 – Enceladus Plume Activity Consistent withEruptions from Sources within a Thin ShellEnceladus is a small (radius 250 km) moon that orbits Saturnbetween the moons Mimas and Tethys with a period of 1.37 days.A 2:1 mean motion resonance with the moon Dione, which orbitsjust beyond Tethys, excites its orbital eccentricity to the observedvalue of 0.0047, which in turn produces periodic tidal stress onthe surface. In 2005, Cassini detected the eruption of material from warmregions, which correlated with the large Tiger Stripe fracturesnear the south pole of Enceladus. A 2007 analysis of tidal stresspostulated that the eruptive activity might be linked to tidaltension across these fractures and predicted that activity shouldvary on the orbital timescale such that greatest activity should beobserved near apocenter (Hurford et al., 2007). In 2013, resultsfrom analysis of Cassini’s Visual and Infrared Map- pingSpectrometer (VIMS) data detected variability of the eruptingmaterial in the orbital cycle and qualitatively confirmed thepredictions of variable activity from 2007 (Hedman et al., 2013;Hurford et al. 2007). Since then, work has been done to refine models for tidal controlof plume activity. Nimmo et al. (2014) found that the plumeactivity could track the fraction of fractures under tension, but

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required a ~5 hr lag in Enceladus’ tidal response. This lag seemedplausible in a 24km ice shell. Behounkova et al. (2105) confirmedthis result with a slightly improved model that linked tidal activityto normalize average tensile stress on the fracture.

In this work, we illustrate how reservoir depth combines with alag in tidal response to mimic larger delays in tidal activity.Taking into account the depth of the volatile reservoir, we findthat the response of Enceladus to tidal deformation needs only be~3 hrs and is more consistent with eruptions from a thin ice shell(≤10 km). This result is more consistent with recent revisions inice shell thickness (Iess et al., 2014; Thomas et al., 2016).

Hurford et al., 2007, Nature 447, 292-294. Hedman et al, 2013,Nature 500, 182-184. Nimmo et al, 2014, The AstronomicalJournal 148. Behounkova et al., 2015, Nature Geoscience 8, 601-604. Iess et al., 2014, Science 344, 78-80. Thomas et al., 2016,Icarus 264, 37-47.

Author(s): Terry Hurford , Joseph N. Spitale , Alyssa R.Rhoden , Wade HenningInstitution(s): 1. ASU, 2. NASA GSFC, 3. PSI, 4. UMD

207.04 – Enceladus Plume Morphology andVariability from UVIS MeasurementsThe Ultraviolet Imaging Spectrograph (UVIS) on the Cassinispacecraft has been observing Enceladus’ plume and its effect onthe Saturnian environment since 2004. One solar and 7 stellaroccultations have been observed between 2005 and 2017.

On 27 March 2017 epsilon Canis Majoris (CMa) passed behindthe plume of water vapor spewing from Enceladus’ tiger stripefissures. With this occultation we have 6 cuts through the plumeat a variety of orientations over 12 years. Following our standardprocedure the column density along the line of sight fromEnceladus to the star was determined and the water fluxcalculated [1]. The mean anomaly was 131, well away from thedust flux peak associated with Enceladus at an orbital longitudenear apoapsis [2].

We find that the water vapor flux was ~160 kg/sec (this numberwill be refined when the final reconstructed trajectory isavailable). That puts it “in family” with the other occultations,with values that cluster around 200 kg/sec. It is at the low end,which may be consistent with the drop in particle output observedover the last decade [3].

UVIS results show that the supersonic collimated gas jetsimbedded in the plume are the likely source of the variability indust output [4], rather than overall flux from the tiger stripes. Anoccultation of epsilon Orionis was observed on 11 March 2016when Enceladus was at a mean anomaly of 208. Although thebulk flux changed little the amount of water vapor coming fromthe Baghdad I supersonic jet increased by 25% relative to 2011.The Baghdad I jet was observed again in the 2017 epsilon CMaoccultation, and the column density is half that of 2016, furtherbolstering the conclusion that the gas jets change output as afunction of orbital longitude.

UVIS results describing gas flux, jets, and general structure of theplume, the observables above the surface, are key to testinghypotheses for what is driving Enceladus’ eruptive activity belowthe surface.

[1] Hansen, C. J. et al. (2006) Science 311:1423; [2] Hedman, M.M. et al., (2013) Nature 500:182; [3] Ingersoll, A. P. and S. P.Ewald (2017) Icarus 282:260. [4] Hansen, C. J. et al (2017) GRL10.1002/2016GL071853.

Author(s): Candice Hansen , Larry Esposito , Josh Colwell ,Amanda Hendrix , Ganna PortyankinaInstitution(s): 1. PSI, 2. University of Central Florida, 3.University of Colorado, LASP

207.05 – Space Toilets and Ocean Worlds : Whatspacecraft water dumps tell us about plumes onEnceladus and EuropaThe exposure of liquid water on Enceladus and Europa to spaceforms plumes of water vapor and ice grains that may beimportant means of accessing this material and therebyinvestigating the habitability or even presence of life in OceanWorlds. The process is unfamiliar and difficult to fully replicateaffordably in finite-volume terrestrial laboratories, but in fact isseen in the venting of biological waste and fuel-cell water oncrewed space vehicles. Here I review observations of these waterdumps and related spacecraft engineering experiments and theinsights they yield on plume formation processes. Of note are AirForce optical measurements of a release experiment from SpaceShuttle flight STS-29 (which revealed two particle populations -mm-size particles influenced by the vent size and dropletbreakup, and sub-micron grains formed by re-condensation ofexpanding vapor), and the detection of nitrogen- and sulphur-residues in microcraters on recovered spacecraft surfaces due tothe impaction of urine ice crystals, which show promise thatanalogous biosignatures from ocean worlds may be detected bysuitable instrumentation on future missions. Hazardous icicleformation in vacuum from Space Shuttle dumps on STS-41D(which required action with the robot arm to remove beforeentry) highlight the possible evolution of vent geometry onEnceladus by local recondensation and freezing.

Author(s): Ralph LorenzInstitution(s): 1. JHU/APL

207.06 – A parametric study of Enceladus plumesbased on DSMC calculations for retrieving theoutgassing parameters as measured by CassiniinstrumentsThe vapor and particulate plumes arising from the southern polarregions of Enceladus are a key signature of what lies below thesurface. Multiple Cassini instruments (INMS, CDA, CAPS, MAG,UVIS, VIMS, ISS) measured the gas-particle plume over the warmTiger Stripe region and there have been several close flybys.Numerous observations also exist of the near-vent regions in thevisible and the IR. The most likely source for these extensivegeysers is a subsurface liquid reservoir of somewhat saline waterand other volatiles boiling off through crevasse-like conduits intothe vacuum of space. In this work, we use a DSMC code to simulate the plume as itexits a vent, considering axisymmetric conditions, in a verticaldomain extending up to 10 km. Above 10 km altitude, the flow iscollisionless and well modeled in a separate free molecular code.We perform a DSMC parametric and sensitivity study of thefollowing vent parameters: vent diameter, outgassed flow density,water gas/water ice mass flow ratio, gas and ice speed, and icegrain diameter. We build parametric expressions of the plumecharacteristics at the 10 km upper boundary (number density,temperature, velocity) that will be used in a Bayesian inversionalgorithm in order to constrain source conditions from fits toplume observations by various instruments on board the Cassinispacecraft and assess the parametric sensitivity study.

Author(s): Arnaud Mahieux , David B. Goldstein , PhilipVarghese , Laurence M. TraftonInstitution(s): 1. University of Texas at Austin

208.01 – Temperature and rate of dehydration ofmajor constituents of carbonaceous chondritesunder vacuum conditions

Some sub-types of carbonaceous chondrites contain a significantamount of hydrated minerals which produce specific absorptionlines, typically due to the presence of hydroxyls. However, if theseasteroids have come close enough to the Sun during their history,

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the high temperatures might have resulted in mineraldecomposition and consequent loss of hydroxyl (or water)molecules in the surface layer and even to certain depths.Determination of the hydration state of phyllosilicates typicallyfound on asteroids as well as the relative quantities of hydrated todesiccated phyllosilicates relies on experimental data - thetemperature and rate of dehydration. Both dehydrationtemperature and rate depend on pressure. The rate also dependson the temperature. Experimentally determined phase curves forserpentine, that show for example decomposition of antigorite toforsterite and enstatite or talc and water, exist for GPa pressurelevels. For antigorite, these temperatures span the range 500-750°C for pressures between 0.1 GPa and 8 GPa. However, thesedata are not suitable for vacuum environment found on asteroids;further, at lower pressures, the available data suggest amonotonically decreasing dehydration temperature withdecreasing pressure. Also, the available data suggest dependenceof both dehydration temperature and rate on the grain sizedistribution of the mineral. We have determined the temperatureand rate of dehydration of the serpentine polymorphs antigorite,lizardite, cronstedtite, under high vacuum conditions and forvarious grain size distributions. The grain size distributions havebeen determined by particle analyzer and each sample source wasalso analyzed using X-Ray Diffraction.

Author(s): Leos Pohl , Daniel BrittInstitution(s): 1. University of Central Florida

208.02 – Multiple scattering modeling pipeline forspectroscopy and photometry of airless SolarSystem objectsWe combine numerical tools to analyze the reflectance spectra ofgranular materials. Our motivation comes from the lack of toolswhen it comes to intimate mixing of materials and modelingspace-weathering effects with nano- or micron-sized inclusions.The current practice is to apply a semi-physical models such asthe Hapke models (e.g., Icarus 195, 2008). These are expressed ina closed form so that they are fast to apply. The problem is thatthe validity of the model is not guaranteed, and the derivedproperties related to particle scattering can be unrealistic (JQSRT113, 2012).

Our pipeline consists of individual scattering simulation codesand a main program that chains them together. The chain foranalyzing a macroscopic target with space-weathered mineralwould go as: (1) Scattering properties of small inclusions inside ahost matrix are derived using exact Maxwell equation solvers.From the scattering properties, we use the so-called incoherentfields and Mueller matrices as input for the next step; (2)Scattering by a regolith grain is solved using a geometrical opticsmethod with surface reflections, internal absorption, and internaldiffuse scattering; (3) The radiative transfer simulation isexecuted inputting the regolith grains from the previous step asthe scatterers in a macroscopic planar volume element.

For the most realistic asteroid reflectance model, the chain wouldproduce the properties of a planar surface element. Then, ashadowing simulation over the surface elements would beconsidered, and finally the asteroid phase function would besolved by integrating the bidirectional reflectance distributionfunction of the planar element over the object's realistic shapemodel.

The tools in the proposed chain already exist, and practical taskfor us is to tie these together into an easy-to-use public pipeline.We plan to open the pipeline as a web-based open service adedicated server, using Django application server and Pythonenvironment for the main functionality. The individual programsto be ran under the chain can still be programmed with Fortran,C, or other.

We acknowledge the ERC AdG No. 320773 ‘SAEMPL’ and thecomputational resources provided by CSC — IT Center for ScienceLtd., Finland.

Author(s): Antti Penttilä , Timo Väisänen , JohannesMarkkanen , Julia Martikainen , Maria Gritsevich , KarriMuinonenInstitution(s): 1. University of Helsinki

208.03 – Interrelating meteorite and asteroidspectra at UV-Vis-NIR wavelengths using novelmultiple-scattering methodsAsteroids have remained mostly the same for the past 4.5 billionyears, and provide us information on the origin, evolution andcurrent state of the Solar System. Asteroids and meteorites can belinked by matching their respective reflectance spectra. This isdifficult, because spectral features depend strongly on the surfaceproperties, and meteorite surfaces are free of regolith dustpresent in asteroids. Furthermore, asteroid surfaces experiencespace weathering which affects their spectral features. We present a novel simulation framework for assessing thespectral properties of meteorites and asteroids and matchingtheir reflectance spectra. The simulations are carried out byutilizing a light-scattering code that takes inhomogeneous wavesinto account and simulates light scattering by Gaussian-random-sphere particles large compared to the wavelength of the incidentlight. The code uses incoherent input and computes phasematrices by utilizing incoherent scattering matrices. Reflectancespectra are modeled by combining olivine, pyroxene, and iron,the most common materials that dominate the spectral features ofasteroids and meteorites. Space weathering is taken into accountby adding nanoiron into the modeled asteroid spectrum. Thecomplex refractive indices needed for the simulations areobtained from existing databases, or derived using anoptimization that utilizes our ray-optics code and the measuredspectrum of the material. We demonstrate our approach by applying it to the reflectancespectrum of (4) Vesta and the reflectance spectrum of theJohnstown meteorite measured with the University of Helsinkiintegrating-sphere UV-Vis-NIR spectrometer. Acknowledgments. The research is funded by the ERC AdvancedGrant No. 320773 (SAEMPL).

Author(s): Julia Martikainen , Antti Penttilä , MariaGritsevich , Karri MuinonenInstitution(s): 1. University of Helsinki

208.04 – A Large Program to derive the shape,cratering history and density of the largest main-belt asteroidsAsteroids in our solar system are metallic, rocky and/or icyobjects, ranging in size from a few meters to a few hundreds ofkilometers. Whereas we now possess constraints for the surfacecomposition, albedo and rotation rate for all D≥100 km main-beltasteroids, the 3-D shape, the crater distribution, and the densityhave only been measured for a very limited number of thesebodies (N≤10 for the first two). Characterizing these physicalproperties would allow us to address entirely new questionsregarding the earliest stages of planetesimal formation and theirsubsequent collisional and dynamical evolution. ESO allocated to our program 152 hours of observations over 4semesters to carry out disk-resolved observations of 38 large(D≥100 km) main-belt asteroids (sampling the four maincompositional classes) at high angular-resolution withVLT/SPHERE throughout their rotation in order to derive their3-D shape, the size distribution of the largest craters, and theirdensity (PI: P. Vernazza). These measurements will allowinvestigating for the first time and for a modest amount ofobserving time the following fundamental questions: (A) Does theasteroid belt effectively hosts a large population of small bodiesformed in the outer solar system? (B) Was the collisionalenvironment in the inner solar system (at 2-3 AU) more intensethan in the outer solar system (≥5AU)? (C) What was the shape ofplanetesimals at the end of the accretion process?

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We will present the goals and objectives of our program in thecontext of NASA 2014 Strategic Plan and the NSF decadal survey"Vision and Voyages" as well as the first observations and resultscollected with the SPHERE Extreme AO system. A detailedanalysis of the shape modeling will be presented by Hanuš et al.in this session.

Author(s): Franck Marchis , Pierre Vernazza , MichaelMarsset , Josef Hanus , Benoit Carry , Mirel Birlan , ToniSantana-Ros , Bin YangInstitution(s): 1. Aix Marseille Univ, CNRS, LAM, Laboratoired’Astrophysique de Marseille, 2. Astronomical Institute, Facultyof Mathematics and Physics, Charles University, 3. AstronomicalObservatory Institute, Adam Mickiewicz University, 4.Astrophysics Research Centre, Queen’s University, 5. EuropeanSouthern Observatory, 6. IMCCE, Observatoire de Paris, 7. SETIInstitute, Carl Sagan Center, 8. Université Côte d’Azur,Observatoire de la Côte d’AzurContributing team(s): and the Large Asteroid Survey withSPHERE (LASS)

208.05 – Shape models of large asteroids based ondisk-resolved images collected with the SPHEREExtreme AO systemESO allocated to our Large Asteroid Survey with SPHERE (LASS)program 152 hours of observations over four semesters (PI: PierreVernazza, run ID: 199.C-0074) to carry out disk-resolved imagesof 38 large (D≥100 km) main-belt asteroids (sampling the fourmain compositional classes) at high angular-resolution withVLT/SPHERE throughout their rotation in order to derive their3-D shape, the size distribution of the largest craters, and theirdensity. LASS program is introduced in more details by Marchiset al. in this session.

Here we focus on the preliminary shape modeling of a fewindividual asteroids that were targeted in the first semester of theLASS program by the SPHERE Extreme AO system. To obtain the3D shape model with a local topography, we utilize the All-DataAsteroid modelling (ADAM, Viikinkoski et al. 2015, A&A, 576,A8) procedure that allows simultaneous inversion of opticallightcurves, stellar occultations and disk-resolved images.Because ADAM minimizes the difference between the Fouriertransformed image and a projected polyhedral model, we do notrequire any a priori extraction of boundary contours. Utilizationof AO images allows ADAM to scale the shape model in size,which essentially leads to a volume estimate.

We derive preliminary shape models for selected asteroids andcompare them with models based on disk-resolved imagesobtained by the Near InfraRed Camera (Nirc2) mounted on theW. M. Keck II telescope. We illustrate the performance of theADAM procedure and the shape model improvement due to theunprecedented quality of the SPHERE images.

Author(s): Josef Hanus , Pierre Vernazza , MichaelMarsset , Franck Marchis , Benoit Carry , Toni Santana-Ros ,Mirel Birlan , Matti Viikinkoski , Josef Durech , MikkoKaasalainenInstitution(s): 1. Aix Marseille Univ, CNRS, LAM, Laboratoired’Astrophysique de Marseille, 2. Astronomical Institute, Facultyof Mathematics and Physics, Charles University in Prague, 3.Astronomical Observatory Institute, Adam MickiewiczUniversity, 4. Astrophysics Research Centre, Queen’s University,5. Department of Mathematics, Tampere University ofTechnology, 6. IMCCE, Observatoire de Paris, 7. SETI Institute,Carl Sagan Center, 8. Université Côte d’Azur, Observatoire de laCôte d’AzurContributing team(s): and the Large Asteroid Survey withSPHERE (LASS)

208.06D – The search for extreme asteroids in thePan-STARRS 1 Survey

Using sparse photometry of main belt asteroids obtained in thefirst 1.5 years of the Pan-STARRS 1 survey we identified a list ofpotential ’extreme lightcurve asteroids’, defined as objects witheither rotation period P < 2.2 h or light curve amplitude A ≥ 1.0mag. Follow-up observations were made of 22 asteroids using the2.5 m Isaac Newton Telescope, the 3.5m ESO New TechnologyTelescope and the University of Hawaii 2.2 m Telescope. 9 ofthese objects were found to have light curve amplitudes A > 1.0mag, with no objects with P < 2.2 h being observed. Fromlightcurve analysis we determine that 5 may be single rubble pileellipsoids with significant cohesive strength allowing them toresist mass shedding even at their highly elongated shapes. It wasnot possible to analytically find unique shape solutions for theremaining objects with the available data. Two asteroids wereobserved at a number of orbital geometries allowing for shapeand spin pole models to be determined through light curveinversion. (45864) 2000 UO97 was determined to haveretrograde rotation with spin pole latitude and longitude β=82 ±5 , λ=218 ± 10 and asteroid (206167) 2002 TS242 was found tohave spin pole axes β=-67 ± 5 , λ= 57 ± 5 . Using serendipitousobservations, an additional asteroid not initially measured with A> 1.0 mag, (49257) 1998 TJ31, was determined to have a shapemodel suggesting a higher amplitude than that measured from itssparse photometry light curve (A = 0.8 mag). Its spin pole axeswere found to be β=6 ± 5 , λ=112 ± 6 . The high obliquity of thisobject could explain how we initially failed to identify this body ashigh amplitude from its light curve alone, when its shape solutionsuggests otherwise. Since the initial generation of our target list,the number of asteroid detections by Pan-STARRS has increaseddramatically. Using the same criteria for the generation of thisinitial target list but utilising all of the data available we now havea list of 110 potential high amplitude objects which we arecontinuing to observe.

Author(s): Andrew McNeill , Alan Fitzsimmons , RobertJedicke , Eva Lilly , Pedro Lacerda , David E. TrillingInstitution(s): 1. Institute for Astronomy, University ofHawaii, 2. Northern Arizona University, 3. Queen's UniversityBelfastContributing team(s): Members of the Pan-STARRS ScienceConsortium

208.07 – Hungaria Asteroid Region TelescopicSpectral Survey (HARTSS) II: SpectralHomogeneity Among Hungaria Family AsteroidsSpectral observations of asteroid family members providevaluable information regarding parent body interiors, the sourceregions of near-Earth asteroids, and the link between meteoritesand their parent bodies. Hungaria family asteroids constitute theclosest samples to the Earth from a collisional family (~1.94 AU),permitting observations of smaller fragments than accessible forMain Belt families. We have carried out a ground-basedobservational campaign - Hungaria Asteroid Region TelescopicSpectral Survey (HARTSS) - to record reflectance spectra of thesepreserved samples from the inner-most primordial asteroid belt.During HARTSS phase one (Lucas et al. [2017]. Icarus 291, 268-287) we found that ~80% of the background population iscomprised of stony S-complex asteroids that exhibit considerablespectral and mineralogical diversity. In HARTSS phase two, weturn our attention to family members and hypothesize that theHungaria collisional family is homogeneous. We test thishypothesis through taxonomic classification, albedo estimates,and spectral properties. During phase two of HARTSS we acquired near-infrared (NIR)spectra of 50 new Hungarias (19 family; 31 background) withSpeX/IRTF and NICS/TNG. We analyzed X-type family spectrafor NIR color indices (0.85-J; J-K), and a subtle ~0.9 µmabsorption feature that may be attributed to Fe-poororthopyroxene. Surviving fragments of an asteroid collisionalfamily typically exhibit similar taxonomies, albedos, and spectralproperties. Spectral analysis of X-type Hungaria family membersand independently calculated WISE albedo determinations for428 Hungaria asteroids is consistent with this scenario.Furthermore, ~1/4 of the background population exhibit similar

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spectral properties and albedos to family X-types.

Spectral observations of 92 Hungaria region asteroids acquiredduring both phases of HARTSS uncover a compositionallyheterogeneous background and spectral homogeneity down to ~2km for collisional family members. Taxonomy, albedos, andspectral properties reveal that the Hungaria family progenitorwas an igneous body that formed under reduced conditions, andwas compositionally consistent with the enstatite achondrite (i.e.,aubrite) meteorite group.

Author(s): Michael P Lucas , Joshua Emery , Noemi Pinilla-Alonso , Sean S. Lindsay , Eric M. MacLennan , RichardCartwright , Vishnu Reddy , Juan A Sanchez , Cristina A.Thomas , Vania LorenziInstitution(s): 1. Department of Physics and Astronomy,University of Tennessee, 2. Fundación Galileo Galilei, 3. Lunarand Planetary Laboratory, University of Arizona, 4. PlanetaryScience Institute, 5. University of Central Florida, 6. Universityof Tennessee

208.08 – A Most Incredible Asteroid: The Break-Up of P/2013 R3We present a comprehensive study of the actively disintegratingasteroid P/2013 R3. Using the Hubble and Keck telescopes, weidentified thirteen discrete components separating with a mean,pair-wise velocity dispersion of v = 0.33+/-0.03 m/s. Theirseparation times are staggered over an interval of 5 months.Combined, the components of P/2013 R3 would form a singlespherical body with radius 400 m, which is our best estimate ofthe size of the precursor object. Dust enveloping the system has,in the first observations, a cross-section 30 sq. km but fadesmonotonically at a rate consistent with the action of radiationpressure sweeping. The individual components exhibit comet-likemorphologies and also fade except where secondaryfragmentation is accompanied by the release of additional dust.Upper limits to the radii of any embedded solid nuclei aretypically 100 to 200 m (geometric albedo 0.05 assumed). Theobservations are consistent with rotational disruption of a weak(cohesive strength 50 to 100 Pa) parent body, 400 m in radius.Estimated radiation (YORP) spin-up times of this parent are lessthan 1 Myr, shorter than the collisional lifetime. If present, waterice sublimating at as little as 1 g/s could generate a torque on theparent body rivaling the YORP torque. Under conservativeassumptions about the frequency of similar disruptions, theinferred asteroid debris production rate is 1000 kg/s, which is atleast 4 percent of the rate needed to maintain the Zodiacal Cloud.

The work has been recently published: D. Jewitt, J. Agarwal, J. Li,H. Weaver, M. Mutchler, S. Larson (2017). The AstronomicalJournal, 153:223(17pp)

Author(s): David Jewitt , Jessica Agarwal , Jing Li , HaroldA Weaver , Maximilian J. Mutchler , Stephen M. LarsonInstitution(s): 1. Johns Hopkins Applied Physics Laboratory,2. Max Planck, 3. Space Telescope Science Institute, 4. UCLA, 5.University of Arizona

208.09 – Split Active Asteroid P/2016 J1(PANSTARRS)We present a photometric and astrometric study of the split activeasteroid P/2016 J1 (PANSTARRS). Separation occurred either in2012 May to June, or 2010 April, with a separation speed V =0.70 ± 0.02 m s for the former scenario and 0.83 ± 0.06 m sfor the latter. The two fragments (hereafter J1-A and J1-B) havesimilar, Sun-like colors that are comparable to the colors ofprimitive C- and G-type asteroids. With a nominal comet-likealbedo, p = 0.04, the effective, dust-contaminated cross sectionsare estimated to be 2.4 km (J1-A) and 0.5 km (J1-B). Weestimate that the nucleus radii lie in the range 140 < R < 900 m(J1-A) and 40 < R < 400 m (J1-B). A syndyne-synchronesimulation shows that both components have dust ejection rates~1 kg s (J1-A) and 0.1 kg s (J1-B) sustained for 3-6 months.The rotational spin-up and devolatilization times of 2016 J1 are

both short compared to the age of the solar system, raising thequestion of why this object still exists. We suggest that formerlyburied ice became exposed at the surface, perhaps via a minorimpact, and that sublimation torques then rapidly drove the bodyto breakup. Further disintegration events are anticipated owing tothe rotational instability. Reference: Hui, M.-T., Jewitt, D. andDu, X., 2017. AJ, 153(4), p.141.

Author(s): Man-To Hui , David Jewitt , Xinnan DuInstitution(s): 1. University of California, Los Angeles

208.10 – Variation in Surficial Hydrated Mineralson Large Low-Albedo Asteroids Observations of asteroids in the 3-µm spectral region, whereabsorptions diagnostic for hydrated minerals are found, showlow-albedo asteroid spectra can be classified into at least 3 groups(Takir et al. 2013, Rivkin et al. 2015). While definitions of thesegroups vary between authors, they hold in common a group withspectra like what we see for CM/CI meteorites, one group withspectra like that of Ceres, and a group with spectra that have beeninterpreted as ice frost. The relationship between these groups is not yet clear. Onepossibility is that the spectrum reflects (no pun intended) theformation location for the asteroids and that a given object isundifferentiated and homogeneous in the composition of itshydrated minerals. However, models of the thermal and chemicalevolution of large, low-albedo asteroids suggests thatdifferentiation may be more common than we had thought, andimpacts could exhume once-deep layers or expose complicatedmixes of salts and silicates (for instance, Castillo-Rogez et al.LPSC 2017 model of Ceres). In this case, we might expectvariation in the 3-µm spectral region to be seen on the surfaces ofsome objects as they rotate. We will present evidence for such variation in the spectrum of twolarge asteroids, 704 Interamnia (306 km diameter) and 324Bamberga (220 km diameter). In the first case, Interamnia’sspectrum seems to have a combination of Ceres- and CM/CI-likefeatures and has aspects where one or another component isdominant, while Bamberga’s spectrum is not easily placed inpreviously-defined groups.

Author(s): Andrew S. Rivkin , Joshua P. Emery , Ellen S.HowellInstitution(s): 1. JHU/APL, 2. University of Arizona, 3.University of Tennessee

208.11D – Water in the early solar system: Mid-infrared studies of aqueous alteration on asteroids.This work investigates the distribution of water in the early SolarSystem by connecting asteroids to carbonaceous chondritemeteorites using spectroscopy. Aqueous alteration or thechemical reaction between liquid water and silicates on the parentasteroid, has extensively affected several groups of carbonaceouschondrites. The degree of alteration or amount of hydratedminerals produced depends on a number of factors including theabundance of coaccreted water-ice, the internal distribution ofwater in the parent body and the setting of alteration (e.g., openvs. closed setting). Despite this complexity which is still underinvestigation, the mineralogical changes produced by aqueousalteration are well understood (e.g., Howard et al., 2015). Themid-infrared spectral region has been shown to be a tool forestimating the degree of alteration of asteroids and meteoritesremotely (McAdam et al., 2015). Specifically, mid-infraredspectral features changes continuously with degree of alteration.In this region meteorites can be categorized into four groupsbased on their spectral characteristics: anhydrous, less altered,intermediately altered and highly altered. We present theestimated degrees of alteration for 73 main belt asteroids usingthese results. Hydrated minerals appear to be widespread in themain belt and asteroids have variable degrees of alteration. Theredoes not appear to be any relationship between the estimateddegree of alteration and size, albedo or heliocentric distance. This

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indicates that water-ice must have been a significant componentof the solar nebula in the 2-5 AU region during the time ofcarbonaceous chondrite accretion (~2.7-4 Ma post-CAIformation; Sugiura and Fujiya, 2014). The snow-line thereforemust have been in this region during this epoch. Furthermore,local heterogeneities of water-ice were likely common sinceasteroids of all sizes and heliocentric distances may exhibit anydegree from anhydrous to highly altered. Additionally, asteroidsthat have been shown to have water-ice on their surfaces (e.g.,Takir and Emery, 2012) appear to have hydrated minerals. Thisindicates that while these asteroids have water-ice, its presencedid not prevent aqueous alteration.

Author(s): Margaret M. McAdam , Jessica M. Sunshine ,Michael S. Kelley , David E. TrillingInstitution(s): 1. Northern Arizona University , 2. Universityof Maryland

208.12D – Identifying asteroid families >2 Gyrs-oldThere are only a few known Main Belt (MB) asteroid families withages >2 Gyr. The lack of ancient families may be due to a bias incurrent techniques used to identify families. Ancient asteroidfamily fragments disperse in their orbital elements (a,e,i), due tosecular resonances and the Yarkovsky effect (YE) making themdifficult to identify. We have developed a new technique that isinsensitive to the resonant spreading of fragments in e and i bysearching for V-shaped correlations between family members in avs 1/Diameter space. Our V-shape technique is demonstrated onknown families and used to discover a 4 Gyr-old family linkingmost dark asteroids in the inner MB previously not included inany known family. In addition, the 4 Gyr-old family revealsasteroids with D >35 km that are do not belong to any asteroidfamily implying that they originally accreted from the

protoplanetary disk. The V-shape detection tool is also a powerful analysis tool byfinding the boundary of an asteroid family and fitting for itsshape. Following the proposed relationship between thermalinertia (TI) with D, we find that asteroids YE drift rate might havea more complex size dependence than previous thought, leadingto a curved family boundary in a vs 1/D space. The V-shape tool iscapable of detecting this on synthetic families and was deployedon >30 families located throughout the MB to find this effect andquantify the YE size-dependent drift rate. We find that there is nocorrelation between family age and V-shape curvature. Inaddition, the V-shape curvature decreases for asteroid familieswith larger a suggesting that the relationship between TI and D isweaker in the outer MB. By examining families <20 Myrs-old, we can use this tool toseparate family shape that is due to the initial ejection velocityand that which is due to the YE drift rate. V-shapes which do notcontain any spreading due to YE preserve their initial ejectionvelocity. We constrain the initial initial velocity of young familiesby measuring the curvature of their fragments' V-shape in a vs1/D space. We find that the majority of <20 Myr-old asteroidfamilies have initial velocity fields scaling with 1/D supportingimpact experiments.

Author(s): Bryce T. Bolin , Alessandro Morbidelli , MarcoDelbo , Kevin J. WalshInstitution(s): 1. Obs. de La Cote D'Azur, 2. SouthwestResearch Institute

209.01 – INMS measures an influx of moleculesfrom Saturn’s ringsIn 1984, Connerney and Waite proposed water influx fromSaturn’s rings to explain the low electron densities measuredduring Pioneer and Voyager radio occultation experiments.Charge exchange with this minor species depleted the H ionsand provided a faster path to electron recombination. With ice theprimary constituent of the rings, water was the most likely in-falling molecule.

During the Grand Finale orbits, Cassini’s Ion and Neutral MassSpectrometer (INMS) detected and quantified an influx from therings. Unexpectedly, the primary influx molecules are CH and aheavier carbon-bearing species. Water was detected, butquantities were factors of ten lower than these other species.

Distribution in both altitude and latitude are consistent with aring influx. The concentration of the minor species in Saturn’satmosphere shows that they enter Saturn’s atmosphere from thetop. Both molecules have their highest concentrations at thehighest altitudes, with concentrations >0.4% at 3,500 km altitudeand only 0.02% at 2,700 km. Molecules from the rings deorbit toSaturn’s atmosphere at altitudes near 4,000 km, consistent withthe INMS measurements.

The latitudinal dependence of the minor species indicates thattheir source is near the equatorial plane. At high altitudes, theminor species were observed primarily at zero latitude, where the28u species was six times more concentrated than at 5° latitude.At lower altitudes, the peaking ratio was 1, indicating that thespecies had diffused and was fully mixed into Saturn’s Hatmosphere. The lighter molecule, CH , diffuses more rapidlythan the 28u species. INMS also detected both of these speciesduring the earlier F-ring passes, finding that the neutrals werecentered at the ring plane and extended 3,000 km (half width,half max) north and south.

Author(s): Mark E. PerryInstitution(s): 1. Johns Hopkins Applied Physics LabContributing team(s): The Cassini INMS team

209.02 – Monitoring Saturn's Upper AtmosphereDensity Variations Using Helium 584 AirglowThe study of He 584 Å brightnesses is interesting as the EUV(Extreme UltraViolet) planetary airglow have the potential toyield useful information about mixing and other importantparameters in its thermosphere. Resonance scattering of sunlightby He atoms is the principal source of the planetary emission ofHe 585 Å. The principal parameter involved in determining theHe 584 Å albedo are the He volume mixing ratio, f_He, wellbelow the homopause. Our main science objective is to estimatethe helium mixing ratio in the lower atmosphere. Specifically, Heemissions come from above the homopause where optical depthtrau=1 in H2 and therefore the interpretation depends mainly ontwo parameters: He mixing ratio of the lower atmosphere andK_z. The occultations of Koskinen et al (2015) give K_z with anaccuracy that has never been possible before and the combinationof occultations and airglow therefore provide estimates of themixing ratio in the lower atmosphere. We make these estimates atseveral locations that can be reasonably studied with bothoccultations and airglow and then average the results. Our resultslead to a greatly improved estimate of the mixing ratio of He inthe upper atmosphere and below. The second objective is toconstrain the dynamics in the atmosphere by using the estimateof the He mixing ratio from the main objective. Once we have anestimate of the He mixing ratio in the lower atmosphere thatagrees with both occultations and airglow, helium becomes aneffective tracer species as any variations in the Cassini UVIShelium data are direct indicator of changes in K_z i.e., dynamics.Our third objective is to connect this work to our Cassini UVISdata He 584 Å airglow analyses as they both cover the time spanof the observations and allow us to monitor changes in theairglow observations that may correlate with changes in the stateof the atmosphere as revealed by the occultations Saturn's upperthermosphere. This work helps to determine the mixing ratio ofHe and constrain dynamics in the upper atmosphere, both ofwhich are high level science objectives of the Cassini mission.

Author(s): Chris ParkinsonInstitution(s): 1. Univ. of Michigan

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209.03 – Constraints on atmospheric structure andhelium abundance of Saturn from Cassini/UVISand CIRSWe combine results from stellar occultations observed byCassini/UVIS and infrared emissions observed by Cassini/CIRSto create empirical models of atmospheric structure on Saturncorresponding to the locations probed by the UVIS stellaroccultations. These models span multiple occultation locations atdifferent latitudes from 2005 to the end of 2015. In summary, weconnect the temperature-pressure profiles retrieved from theCIRS data to the temperature-pressure profiles in thethermosphere retrieved from the occultations. A correspondingaltitude scale is calculated and matched to the altitude scale of thedensity profiles that are retrieved directly from the occultations.In addition to the temperature structure, our ability to match thealtitudes in the occultation light curves depends on the meanmolecular weight of the atmosphere. We use the UVISoccultations to constrain the abundance of methane near thehomopause, allowing us to constrain the eddy mixing rate of theatmosphere. In addition, our preliminary results are consistentwith a mixing ratio of about 11% for helium in the loweratmosphere. Our results provide an important reference forfuture models of Saturn’s upper atmosphere.

Author(s): Tommi Koskinen , Sandrine GuerletInstitution(s): 1. Laboratoire de MeteorologieDynamique/IPSL, CNRS, UPMC University of Paris 06,Sorbonne Universites, 2. University of Arizona

209.04 – Saturn's stratospheric temperature andcomposition at the epoch of the 2017 summersolstice.Over the course of its 29.5-years orbit, Saturn undergoessignificant seasonal changes, owing to its 26.7° axial tilt. 2017marks the end of the 13-year exploration of the Saturnian systemby the Cassini spacecraft and coincides with summer solstice inSaturn's northern hemisphere. Monitoring changes intemperature and composition in Saturn's stratosphere throughseasons can teach us about dynamical, radiative and chemicalprocesses governing its atmospheric structure and evolution.Here we report on thermal infrared spectroscopic observations ofSaturn's stratosphere in March 2017 obtained with the TexasEchelon Cross Echelle Spectrograph (TEXES) mounted on theGemini telescope. We retrieve vertical profiles of the temperaturebetween latitudes 15°S and 87°N from the analysis of methaneemission lines near 1245 cm . The inferred zonally averagethermal structure is validated against Cassini/CIRSmeasurements acquired in January and February 2017. Thesedatasets (ground-based and space-based) are in excellentagreement. The 1-mbar temperature is found to increasemoderately from 140K at 20°N to 145K at 60°N, then increasesmore sharply to reach 155K at 85°N. The overall meridionaltemperature gradient observed in 2017 resembles the oneobserved in 2004 in the southern summer hemisphere, where awarm “polar hood” was observed poleward of 70°S [Fletcher etal., 2008]. In contrast, a seasonal radiative-equilibrium model[Guerlet et al., 2014] predicts much smaller and smoothermeridional temperature gradients with latitude. We furtheranalysed Cassini/CIRS data acquired in 2014 over the northernhemisphere to study seasonal changes between 2014 and 2017.Surprisingly, the 1-mbar temperature has slightly cooled down inthe region 25N-55N between these two dates, at odds with themoderate warming predicted by our radiative-equilibrium model.We will discuss several hypotheses to account for these model-observation mismatches. In addition, we also retrieve verticalprofiles of ethane and acetylene volume mixing ratios from theiremission lines recorded by TEXES near 822 and 728 cm-1 andwill discuss their spatial distribution.

Author(s): Sandrine Guerlet , Thomas K. Greathouse ,Glenn S. Orton , Marine Martin-Lagarde , Leigh Fletcher ,Thierry FouchetInstitution(s): 1. CNRS, 2. JPL, 3. Laboratoire de MétéorologieDynamique, 4. LESIA, Observatoire de Paris, 5. SWRI, 6.University of Leicester

209.05 – First determination of the troposphericCO abundance in SaturnIn Giant Planets, CO has two potential origins: i) an externalsource in form of cometary impacts, infalling ring/satellite dustor/and interplanetary particles; ii) an internal origin that involvesconvective transport from the deep, dense, hot atmosphere wherethe thermodynamic equilibrium CO abundance is relatively large. In Saturn, submilimeter stratospheric CO emissions have beendetected (Cavalié et al. A&A, 510, A88, 2010; Cavalié et al. Icarus,203, 531, 2009), suggesting a cometary impact 200 years ago. Incontrast, no observation was in position to confirm or rule out thepresence of CO in Saturn's troposphere (Noll et al. Icarus, 89,168, 1990). Here, we present CRIRES/ELT 5-μm observations of Saturn thatdefinitely confirm the presence of CO in Saturn's troposphere. Wewill present the derived CO abundance and its implication forSaturn's tropospheric transport rate and water deep abundance.

Author(s): Thierry Fouchet , Emmanuel Lellouch , ThibaultCavalié , Bruno BézardInstitution(s): 1. Observatoire de Paris

209.06 – Stratospheric Oxygen Chemistry on theGiant Planets from Dust Ablation and CometsThe stratospheres of Jupiter, Saturn, Uranus, and Neptune allcontain oxygen-bearing molecules that were supplied by comets,interplanetary dust particles, and/or local satellite/ring sources.We use recent dynamical model predictions for the dustvelocity/mass distributions in the outer solar system andcorresponding influx rates to the giant planets (Poppe, A.R., 2016,Icarus 264, 369) to investigate the dust ablation process on theseplanets and to model the resulting coupled oxygen-hydrocarbonneutral photochemistry. Model-data comparisons are then usedto constrain the relative roles of the different sources in deliveringexternal oxygen to the giant planets. We find that dust grainsfrom the Edgeworth–Kuiper Belt, Jupiter-family comets, andOort-cloud comets supply an effective oxygen influx rate of 1.0

×10 O atoms cm s to Jupiter, 7.4 ×10cm s to Saturn, 8.9 ×10 cm s to Uranus, and7.5 ×10 cm s to Neptune. The bulk of the oxygenends up in the photochemically stable species CO, H O, and CO ,which have been observed giant-planet stratospheres.Interplanetary dust grains contribute a major component of theexternal oxygen to Jupiter and Uranus but are insufficient toexplain the CO abundance currently seen in the middlestratospheres of Saturn and Neptune. Our results suggest thatlocal sources such as Enceladus and/or the rings supply much ofSaturn's stratospheric water, while large comets within the lastfew hundred years or so have delivered CO to Jupiter, Saturn,Neptune, and perhaps Uranus. The low background H Oabundance in Jupiter’s stratosphere, in combination with ourhigh predicted dust influx rate, suggests effective conversion ofmeteoric oxygen to CO during or immediately after the ablationprocess —photochemistry alone cannot efficiently convert theH O into CO on the giant planets.

Author(s): Julianne I. Moses , Andrew R PoppeInstitution(s): 1. Space Science Institute, 2. UC-Berkeley

209.07 – Small impacts on the Giant Planet JupiterAmateur video observations of Jupiter have shown five events of1-s long flashes, each one observed by 2-3 observersgeographically separated. The first three of these events occurredon June 3 2010, August 20 2010 and September 10 2012. Analysisof the light-curves of each flash shows that they most probablywere caused by the impact of objects of 5-20 m depending ontheir density (Hueso et al., 2010, 2013) with a released energy

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comparable to superbolides on Earth similar to the Chelyabinskairburst. The last two flashes on Jupiter were detected on 17March 2016 and 26 May 2017 after a long pause in impactsdetections of more than 3 years. In all of these cases no impactdebri at the impact location was found in later observations.

We present detailed light-curves of the five flashes. Photometriccalibration of the images allows to constrain the size of theimpacting objects. We estimate the flash observablecharacteristics of a Jupiter impact event that could leave anobservable debri field on Jupiter’s atmosphere over a few daystriggering fast observations. We also present results from asystematic search of impacts on >65,000 video amateurobservations with a software specifically designed towards impactdetection and based on differential photometry of frames overvideos of Jupiter. From the observations of impacts and astatistical analysis of amateur observations the flux of smallobjects (5-20 m size) impacting Jupiter is predicted to be small(from 1 every 70 days to 1 every 12 days). A larger telescope thanthose used by amateurs could detect smaller impacts happeningmuch more frequently. In spite of the uncertainties, thesenumbers imply that a dense number of observers are required toefficiently discover Jupiter impacts. The first three events weredetected with Jupiter oppositions on September and December in2010 and 2012 respectively and the last two events were detectedwith Jupiter oppositions in March and April 2017. We predict thatmore impacts will be found in the upcoming years with Jupiteropposition displaced towards the Summer in the Northernhemisphere where most amateur astronomers observe.

References: Hueso et al. ApJ, 721L (2010). Hueso et al. A&A, 560, A55 (2013).

Author(s): Ricardo Hueso , Marc Delcroix , Agustin M.Sanchez-Lavega , Jose Felix Rojas , Josep María Gómez-Forrellad , Jon Juaristi-CampilloInstitution(s): 1. Fundació Observatori Esteve Duran, 2.Societé Astronomique de France, 3. UPV/EHU

209.08 – ALMA spectral imaging of SL9 species inJupiter’s stratosphereIn July 1994, the Shoemaker-Levy 9 comet (SL9) spectacularlyimpacted Jupiter near 44°S. On the long term, Jupiter was leftwith a variety of new species in its stratosphere, including CO,HCN, CS, H O, and CO . These species can be used as tracers forJupiter’s stratospheric chemistry and dynamics. Theirdistributions have been monitored, although with stronglimitations in terms of spatial resolution in most cases.

We mapped the spectral emissions of CO and HCN (at 345 and354 GHz, resp.) in Jupiter with ALMA in March 2017. We havesuccessfully performed the first mosaic of Jupiter to cover theentire planet. We have recorded the data with a very high spectralresolution (up to 61 kHz) and at an unprecedented angularresolution of 1.1”, which translates into a meridional resolution of3° at the equator and 7° at 70°S. The lines are detected at theplanetary limb with a high signal-to-noise ratio. The emissiondistributions and line shapes at the limb indicate strongmeridional variability for CO and HCN, quite different from oneanother. In this paper, we will present our observations andpreliminary interpretation of the observed distributions.

Author(s): Thibault Cavalié , Raphael Moreno , EmmanuelLellouch , Thierry Fouchet , Vincent Hue , Thomas K.Greathouse , Michel Dobrijevic , Franck Hersant , PaulHartogh , Christopher Jarchow , Ladislav Rezac , BrunoBézardInstitution(s): 1. LAB, 2. LESIA - Obs. Paris - CNRS, 3. MPS, 4.SwRI

209.09 – First detection of CS in Neptune'satmosphere from ALMA Observations We report on the detection of carbone sulfide (CS) in Neptune'satmosphere, the first unambiguous observation of a sulfur-bearing species in a Giant Planet beyond Jupiter. Our observations used the ALMA interferometer to search forCS(7-6) at 342.883 GHz in Neptune in three occasions In April2016. These measurements were obtained using about 40antenna of the 12m array, despite the angular resolution of ~0.6’’and Neptune’s angular surface diameter was 2.24’’, only disk-averaged measurements allowed to detect with sufficient signal-to-noise ratio the CS line on the three occasions. The narrow lineindicates that CS appears to be present only at sub-millibar levelsin the stratosphere. We will present the analysis of these observations and will discussthe origin of CS as well as a comparison with the CS present inJupiter since the 1994 Shoemaker-Levy 9 impacts. The favored origin of CS in Neptune’ stratosphere is deposition bya putative large comet impact several centuries ago.

Author(s): Raphael Moreno , Emmanuel Lellouch ,Thibault Cavalié , Arielle MoulletInstitution(s): 1. NRAO, 2. Obs. Paris

210.01 – Detection of Deuterium in Icy Surfacesand the D/H Ratio of Icy ObjectsWater ice in crystalline or amorphous form is orientationallydisordered, which results in very broad absorptions. Deuterium intrace amounts goes into an ordered position, so is not broadenedlike H2O absorptions. The D-O stretch is located at 4.13 micronswith a width of 0.027 micron. Laboratory spectral measurementson natural H2O and deuterium doped ice show the absorption isslightly asymmetric and in reflectance the band shifts from 4.132to 4.137 microns as abundance decreases. We derive apreliminary absorption coefficient of ~ 80,000 cm^-1 for the D-Ostretch compared to about 560 cm^-1 in H2O ice at 4.13 microns,enabling the detection of deuterium at levels less than ViennaStandard Mean Ocean Water (VSMOW), depending on S/N. Howaccurate the D/H ratios can be derived will require additional labwork and radiative transfer modeling to simultaneously derivethe grain size distribution, the abundance of any contaminants,and deuterium abundance. To first order, the grain sizedistribution can be compensated by computing the D-O stretchband depth to 2-micron H2O ice band depth ratio, which we callDratio. Colorado fresh water (~80% of VSMOW) has a Dratio of0.036, at a D/H = 0.0005, the Dratio = 0.15, and at a D/H =0.0025, the Dratio = 0.42. The VSMOW Dratio is ~ 0.045.

We have used VIMS data from the Cassini spacecraft to computelarge spectral averages to detect the deuterium in the rings and onthe icy satellite surfaces. A B-ring, 21,882 pixel average, at 640ms/pixel, or 3.89 hours of integration time, shows a 3.5% O-Dstretch band depth and a Dratio = 0.045, indicating deuteriumabundance equal to VSMOW. Rhea, using 1.89 hours ofintegration time shows Dratio = 0.052, or slightly higher thanVSMOW. Phoebe has an unusually deep O-D stretch band of1.85% considering the high abundance of dark materialsuppressing the ice absorptions. We measure a Dratio = 0.11, anenhancement of ~2.4 over VSMOW, but detailed radiativetransfer modeling is needed to derive a more accurate ratio. Theenhancement is consistent with previous studies that suggestPhoebe's origin might be external to the Saturn system. Moresatellites and radiative transfer modeling results will be shown atthe meeting.

Author(s): Roger Nelson Clark , Robert H Brown , Gregg ASwayze , Dale P. CruikshankInstitution(s): 1. NASA, 2. Planetary Science Institute, 3.University of Arizona, 4. USGS

210.02 – Red material on the large moons ofUranus: Dust from the irregular satellites?

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Ground-based, near-infrared (NIR) observations of the classicalUranian satellites show that their surface compositions aredominated by a mixture of H O ice and a dark, spectrally-neutralconstituent. Analysis of data collected during the Voyager 2 flybyof Uranus indicates that a spectrally red constituent is alsopresent on these satellites, primarily on the leading hemispheresof the outer moons. We hypothesize that the red materialoriginated on the irregular satellites, which are redder than theclassical moons. Impact events on the irregular satellites ejectdust particles from their surfaces and into orbit around Uranus.The orbits of these dust particles decay due to Poynting-Robertson drag, and the dust slowly migrates inward. These dustparticles eventually cross into the orbital zone of the classicalmoons, where they are swept up primarily by the leadinghemispheres of the outer moons, with a fairly homogenousdistribution across their southern and northern latitudes.

The data collected by Voyager 2 were over the southernhemispheres of the classical satellites (sub-observer latitude~81°S), when their northern hemispheres were almost entirelyshrouded by winter darkness. We collected new ground-based,NIR spectra of these moons now-observable northernhemispheres (sub-observer latitude ~24 – 35°N). Analysis ofthese new data indicates that the degree of reddening is greateston the leading hemispheres of the outer moons, consistent withthe Voyager 2 observations. Thus, longitudinal and planetocentrictrends in reddening on these moons are apparent at bothnorthern and southern latitudes, supporting the hypothesis thattheir surfaces are mantled by red dust from the irregularsatellites. Additionally, our analysis indicates that the degree ofreddening is greater on Titania than Oberon, in contrast to theanalysis of Voyager 2-era data. We will present work related toour analysis of red material on the classical Uranian moons.

Author(s): Richard Cartwright , Joshua P. Emery , NoemíPinilla-AlonsoInstitution(s): 1. Florida Space Institute, 2. University ofTennessee

210.03 – Icy Saturnian Satellites: Using UV-Visdata to study surface composition & surfaceprocessingThe icy moons of Saturn (Mimas, Enceladus, Tethys, Dione,Rhea) are known to exhibit subtle color variations across theirsurfaces (e.g., Schenk et al., 2011) that appear to be representativeof exogenic processes at these moons, including plume fallout (atEnceladus), E-ring grain bombardment and plasmabombardment. It is known that organics are present in ~30% of Ering grains (Postberg et al., 2008), and that interact with thesurfaces of the satellites orbiting Saturn within the E ring. The Ering organics are likely plasma- and UV-irradiated while in the Ering, and plasma bombardment on the trailing hemispheres of thesatellites is expected to further process these organic moleculesinto longer-chain species that redden and darken the surfaces(Hendrix et al., 2017). We utilize HST/STIS full-disk data toinvestigate spectral differences across the moons to understandlarge-scale spectral effects of organics, E ring bombardment andplasma bombardment.

Author(s): Amanda R. Hendrix , Keith S. Noll , John R.SpencerInstitution(s): 1. NASA Goddard Space Flight Center, 2.Planetary Science Institute, 3. Southwest Research Institute

210.04 – Searching for activity on Dione usingCassini CIRS dataNo direct detection of activity on Dione has ever been made, butthere are many indications that such activity may exist. Forexample Dione has regions of moderately cratered smoothterrains, implying endogenic activity at some point in its history,and extensive fracturing that may be more recent. Other evidencealso points to possible activity on Dione, such as: observations ofan atmosphere-like emission around the moon observed byCassini’s Visual Infrared Mapping Spectrometer (VIMS), possibly

caused by outgassing (Clark et al., 2008, Icarus 193, 372);detection of plasma flow from Dione by Cassini’s PlasmaSpectrometer (CAPS), which indicates possible outgassing (Burchet al., 2007, Nature 447, 883); an enhancement in the strength ofthe ion-cyclotron waves in the magnetosphere, which could alsobe due to ionized plasma from Dione (Khurana et al., 2007, AGUSpring Meeting, Abstract #P43A-03). However, we note that nodirect evidence for plumes on Dione was discovered in analysis ofCassini VIMS data (Buratti et al., 2011, Icarus 214, 534). Cassini’s Composite Infrared Spectrometer (CIRS) has taken over30,000 resolved spectra of Dione since its arrival in the Saturniansystem in 2004. The work presented here is the first systematicstudy of this vast data set to determine whether a thermalsignature of ongoing activity exists on Dione. In the event of adetection we will fully characterize the endogenic emission, whilein the event of a non-detection upper-limits on Dione's activitywill be placed. At the time of writing no endogenic signature hadbeen detected on Dione, but the search continues!

Author(s): Carly Howett , John R. Spencer , AnneVerbiscer , Terry HurfordInstitution(s): 1. Goddard Space Flight Center, 2. SouthwestResearch Institute, 3. University of VirginiaContributing team(s): Cassini CIRS Team

210.05 – Organic Molecules On the Surfaces ofIapetus and PhoebeAbsorption bands of both aliphatic and aromatic organicmolecules are found in the reflectance spectra of Saturn satellitesIapetus, Phoebe, and Hyperion obtained with the Cassini Visible-Infrared Mapping Spectrometer (VIMS) . The VIMS data donot fully resolve the individual bands of C-H functional groupsspecific to particular molecules, but instead show absorptionenvelopes representing blended clusters of the bands of aromatic(~3.28 μm) and aliphatic (~3.4 μm) hydrocarbons known inspectra of interstellar dust . In Cruikshank et al. (2014), wematched components of the unresolved hydrocarbon bandenvelopes with clusters of bands of a range of functional groups inspecific types of organic compounds (e.g., normal and N-substituted polycyclic aromatic hydrocarbons, olefins,cycloalkanes, and molecules with lone-pair interactions of N andO with CH ). In the work reported here, we revisit the spectra ofIapetus and Phoebe using VIMS data processed with improvedradiometric and wavelength calibration (denoted RC19). Theband envelopes of both aromatic and aliphatic hydrocarbons arenow more clearly defined, corroborating the provisionalassignment of specific classes of molecules in Cruikshank et al.2014, but permitting a more reliable quantitative assessment ofthe relative contributions of those classes, and a revision to theearlier estimate of the ratio of the abundances of aromatic toaliphatic molecules. Clark et al. 2012 Icarus 218, 831; Dalle Ore et al. 2012 Icarus

221, 735; Cruikshank et al. 2014 Icarus 233, 306; Pendleton &Allamandola 2002 Ap.J. Supp. 138, 75.

Author(s): Yvonne J. Pendleton , Cristina M. Dalle Ore ,Roger Nelson Clark , Dale P. CruikshankInstitution(s): 1. NASA Ames Research Center, 2. PlanetaryScience Institute

210.06 – The Plasma Environment at Enceladusand Europa ComparedThe plasma environment near Enceladus is complex, as revealedduring 16 encounters of the Cassini spacecraft. The welldocumented Enceladus plumes create a dusty, asymmetricexosphere in which electrons can attach to small ice particles -forming anions, and negatively charged nanograins and dust - tothe extent that cations can be the lightest charged particlespresent and, as a result, the dominant current carriers. Severalinstruments on the Cassini spacecraft are able to measure thisenvironment in both expected and unexpected ways. CassiniPlasma Spectrometer (CAPS) is designed and calibrated to

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212 – Planetary Rings and Satellite Dynamics

measure the thermal plasma ions and electrons and alsomeasures the energy/charge of charged nanograins when present.Cassini Radio Plasma Wave Sensor (RPWS) measures electrondensity as derived from the ‘upper hybrid frequency’ which is afunction of the total free electron density and magnetic fieldstrength and provides a vital ground truth measurement forCassini calibration when the density is sufficiently high for it to bewell measured. Cassini Langmuir Probe (LP) measures theelectron density and temperature via direct current measurement,and both CAPS and LP can provide estimates for the spacecraftpotential which we compare. The plasma environment nearEuropa is similarly complex and, although not socomprehensively equipped and hampered by the non-deploymentof its high gain antenna, the Galileo spacecraft made similar

measurements during 9 Europa flybys and recent observationshave suggested that, like Enceladus, Europa might have activeplume activity. We present a detailed comparison of data from theCassini and Galileo sensors in order to assess the plasmaenvironment observed by the different instruments, discuss whatis consistent and otherwise, and the implications for the plasmaenvironment at Enceladus and Europa in the context of work todate as well as implications for future studies.

Author(s): Abigail Rymer , Ann Persoon , MichikoMorooka , Steven Heuer , Joseph H. WestlakeInstitution(s): 1. IRF, 2. JHU-APL, 3. University of Iowa

211.01 – Global Scale Periodic Responses inSaturn’s MagnetosphereDespite having an axisymmetric internal magnetic field, Saturn’smagnetosphere exhibits periodic modulations in a variety ofproperties at periods close to the planetary rotation period. Whilethe source of the periodicity remains unidentified, it is evidentfrom Cassini observations that much of Saturn’s magnetosphericstructure and dynamics is dominated by global-scale responses tothe driving source of the periodicity. We have developed a globalMHD model in which a rotating field-aligned current system isintroduced by imposing vortical flows in the high-latitudeionosphere in order to simulate the magnetospheric periodicities.The model has been utilized to quantitatively characterize variousperiodic responses in the magnetosphere, such as thedisplacement of the magnetopause and bow shock and flapping ofthe tail plasma sheet, all of which show quantitative agreementwith Cassini observations. One of our model predictions isperiodic release of plasmoids in the tail that occurs preferentiallyin the midnight-to-dawn local time sector during each rotationcycle. Here we present detailed analysis of the periodic responsesseen in our simulations focusing on the properties of plasmoidspredicted by the model, including their spatial distribution,occurrence frequency, and mass loss rate. We will compare thesemodeled parameters with published Cassini observations, anddiscuss their implications for interpreting in-situ measurements.

Author(s): Xianzhe Jia , Margaret G. KivelsonInstitution(s): 1. UCLA, 2. University of Michigan

211.02 – Solar wind control of stratospherictemperatures in Jupiter's auroral regions?Auroral emissions are the process through which the interactionof a planet’s atmosphere and its external magnetosphere can bestudied. Jupiter exhibits auroral emission at a multitude ofwavelengths including the X-ray, ultraviolet and near-infrared.Enhanced emission of CH and other stratospheric hydrocarbonsis also observed coincident with Jupiter’s shorter-wavelengthauroral emission (e.g. Caldwell et al., 1980, Icarus 44, 667-675,Kostiuk et al., 1993, JGR 98, 18823). This indicates that auroralprocesses modify the thermal structure and composition of theauroral stratosphere. The exact mechanism responsible for thisauroral-related heating of the stratosphere has howeverremained elusive (Sinclair et al., 2017a, Icarus 292, 182-207,Sinclair et al., 2017b, GRL, 44, 5345-5354). We will present ananalysis of 7.8-μm images of Jupiter measured by COMICS(Cooled Mid-Infrared Camera and Spectrograph, Kataza et al.,2000, Proc. SPIE(4008), 1144-1152) on the Subaru telescope.These images were acquired on January 11 , 12 , 13 , 14 ,February 4, 5 and May 17 , 18 , 19 and 20 in 2017,allowing the daily variability of Jupiter’s auroral-relatedstratospheric heating to be tracked. Preliminary results suggestlower stratospheric temperatures are directly forced by the solarwind dynamical pressure. The southern auroral hotspot exhibiteda significant increase in brightness temperature over a 24-hourperiod. Over the same time period, a solar wind propagationmodel (Tao et al. 2005, JGR 110, A11208) predicts a strongincrease in the solar wind dynamical pressure at Jupiter.

Author(s): James Andrew Sinclair , Glenn Orton ,Yasumasa Kasaba , Takao M. Sato , Chihiro Tao , J. HunterWaite , Thomas Cravens , Stephen Houston , Leigh Fletcher ,Patrick Irwin , Thomas K. GreathouseInstitution(s): 1. Japanese Aerospace Exploration Agency, 2.Jet Propulsion Laboratory/California Institute of Technology, 3.National Institute of Information and CommunicationsTechnology, 4. Southwest Research Institute, 5. TohokuUniversity, 6. University of Kansas, 7. University of Leicester, 8.University of Oxford

211.03 – A fresh look at Jupiter's synchrotron fromthe Cassini RADAR flybyThe temporal variability is one of the big remaining questions insynchrotron radiation. Most known processes affect the radiationbelts on time scales of month and years, whereas variations onshorter time scales are still a subject of scientific debate. In thislight, the extreme depletion of energetic electrons as revealed bythe 2001 Cassini radio measurements during its flyby of Jupiter isvery surprising. The obtained estimate of the ultra-relativisticelectron number density is considerably lower when compared tomodel calculations and similar observation. It has long beensuspected that the measurements suffered from large systematicuncertainties. The uncertainties were reduced by recalibrating the raw data theCassini RADAR measurements based on an improvedunderstanding of the instrument after a decade of operation atTitan. The uncertainties pertaining to spacecraft pointing and theJovian thermal radiation were solved for by applying a Markov-Chain Monte-Carlo optimization to the full set of 20 Jupiterscans. The synchrotron radiation was then recovered bysubtracting the thermal radiation extending from Jupiter’s upperatmosphere, which comprises up to 97% of the total signalstrength in the Cassini frequency band. The excellent knowledgeof the instrument allows for constraining the disk-averagedbrightness temperature of 158.6K ± 2.4K and can be used toimprove the calibration of radio telescope such as the Very LargeArray. The new retrieval confirmed that systematic artifacts propagatedinto the initial analysis. The synchrotron radio flux was revisedupwards to agree with model predictions of a depletedmagnetosphere. Radio maps indicated an enhancement at higherlatitudes of electrons, requiring processes to scatter particles tohigher latitudes. Comparison with other radio mapsdemonstrated a positive correlation between the energy of theelectrons and the scattering they experienced. This behavior isindicative of wave-particle interactions, which are known to beacting in the terrestrial van-Allen belts but have not so far beenconsidered in the Jupiter models.

Author(s): Chris Moeckel , Michael A. Janssen , Imke dePaterInstitution(s): 1. Delft University of Technology , 2.JPL/Caltech, 3. University of California, Berkeley

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212 Planetary Rings and Satellite Dynamics212.01 – One last look from the dark side: Cassini'sfinal views of Saturn's rings from with the planet'sshadowAround the start of Cassini's Grand Finale, the spacecraft passeda dozen times through Saturn's shadow, enabling its cameras andspectrometers to observe the ring system at extremely high phaseangles. These opportunities yielded the best combination ofsignal-to-noise and resolution for many parts of Saturn's fainterdusty rings, and allowed the main rings to be viewed frompreviously inaccessible lighting geometries. We will highlightsome of the surprising features found in the data obtained byCassini's Imaging Science Subsystem (ISS) and Visual andInfrared Mapping Spectrometer (VIMS) during these timeperiods, and discuss what they might be able to tell us about thestructure and dynamics of Saturn's various ring systems. Forexample, ISS captured global views of the entire ring system thatreveal previously unseen structures in dust-filled regions like theD ring and the zone between Saturn's F and G rings, as well asnovel fine-scale structures in the core of the E ring nearEnceladus' orbit. These structures provide new insights into theforces that sculpt these tenuous rings. ISS and VIMS also detectedan unexpected brightening and highly unusual spectra of themain rings at extremely high phase angles. These data mayprovide novel information about the distribution of small grainsand particles in these denser rings.

Author(s): Matthew M. Hedman , Joseph A. Burns , PhilipD. Nicholson , Matthew S. Tiscareno , Michael W. Evans , EmilyBakerInstitution(s): 1. Cornell University, 2. SETI Institute, 3. SSI, 4.University of Idaho

212.02 – Using Saturn's Rings as a Diagnostic of itsInternal Dierential RotationThis is the end; Cassini crashes into Saturn’s atmosphere,providing unique data and results thanks to the last orbits.Cassini have spent 13 years in orbit around Saturn, during thisperiod, scientists from the world have collected data from manyinstruments and have learned a great deal about the planet itself,its rings and satellites, and the connection between them. I willpresent some of the results some dynamical structures on themain rings of Saturn and their dynamical connection with theinterior of the planet.

Author(s): Maryame El Moutamid , Matthew M. Hedman ,Philip D. NicholsonInstitution(s): 1. Cornell University, 2. University of Idaho

212.03 – VIMS Stellar Occultations and theParticle-Size Distribution of Saturn's RingsOccultations of rings have proven to be a useful way to measurethe particle-size distribution of the bodies making up the ring.During stellar occultations of Saturn's rings observed by Cassini,we have observed 'gap overshoots' or 'horns': places near a sharpedge of the rings, such as the gaps of A Ring, where thetransmission of starlight appears to exceed unity. This excesslight is due to starlight forward-scattered from the nearby ringinto the detector. In this work, we model these `horns' in terms ofa truncated power law particle-size distribution. Due to thegeometry of the observations and the observation wavelength of2.92 microns, chosen to minimize reflected ringshine, ourobservations are sensitive to the distribution of ring particlesfrom the millimeter to decimeter range, which we model thisusing a truncated power law size distribution. Using data from2005 through 2017, we confirm results seen in other wavelengthregimes that show the steepening of the power-law index anddecrease in minimum particle size after the Encke Gap and out tothe edge fo the A Ring and use the Keeler Gap to further constrainthis trend.

Author(s): Rebecca A. Harbison , Philip D. NicholsonInstitution(s): 1. Cornell University, 2. University of Nebraskaat Lincoln

212.04 – Spectrophotometric study of Saturn'smain rings by means of Monte Carlo ray-tracingand Hapke's theoryThis work is devoted to the investigation of thespectrophotometric properties of Saturn's rings from Cassini-VIMS (Visible and Infrared Mapping Spectrometer) observations.The dataset used for this analysis is represented by ten radialspectrograms of the rings which have been derived in Filacchioneet al. (2014) by radial mosaics produced by VIMS. Spectrogramsreport the measured radiance factor of the main Saturn's rings asa function of both radial distance (from 73.500 to 141.375 km)and wavelength (0.35-5.1 µm) for different observationgeometries (phase angle ranging in the 1.9°-132.2° interval). Wetake advantage of a Monte Carlo ray-tracing routine tocharacterize the photometric behavior of the rings at eachwavelength and derive the spectral Bond albedo of rings particles.This quantity is used to infer the composition of the regolithcovering rings particles by applying Hapke's theory. Fourdifferent regions, characterized by different optical depths, andrespectively located in the C ring, inner B ring, mid B ring and Aring, have been investigated. Results from spectral modelingindicate that rings spectrum can be described by water ice withminimal inclusion of organic materials (tholin, < 1%) mixed withvariable amounts of a neutral absorber such as amorphous carbonand amorphous silicates. The abundance of the neutral absorberanti-correlates with the optical depth of the investigated regions,being maximum in the thinnest C ring and minimum in thethickest mid B ring. This distribution of the neutral absorber isinterpreted as the result of a contamination by exogenousmaterial, which is more effective in the less dense regions of therings because of their lower content of pure water ice.

Author(s): Mauro Ciarniello , Gianrico Filacchione ,Emiliano D'Aversa , Jeffrey N. Cuzzi , Fabrizio Capaccioni ,Matthew M. Hedman , Cristina M. Dalle Ore , Philip D.Nicholson , Roger Nelson Clark , Robert H Brown , PriscillaCerroni , Linda SpilkerInstitution(s): 1. Cornell University, 2. INAF-IAPS, 3. JPL, 4.LPL, 5. NASA Ames Research Center, 6. PSI, 7. SETI institute, 8.University of Idaho

212.05 – Ray-tracing temperatures of the MainRings of SaturnThe temperature of the main rings of Saturn is stronglydependent upon the distribution and the general structure of theensembles of particles that compose them, mainly due toshadowing effects that modulate how much energy reaches theindividual particles granted that the direct solar energy is themain driver of the rings' temperature-. In this work we separatethe main rings (A, CD, B and C) in 13 different regions along theradial direction and, based on the average properties of thestructure of these regions derived from the Cassini UVISobservations, we simulate them using lambertian sphericalparticles. These simulations are then used to derive theirshadowed/non-shadowed fractional areas as the solar elevationangle varies and then their temperature variation with the sameangle. For this purpose we use a semi-analytical model where fourenergy sources are considered (solar direct and Saturn reflectedenergy, Saturn thermal energy and particles' thermal energies).The synthetic temperature results are compared to the Cassinimeasured temperatures (from -22 deg to equinox) with goodagreement.

Author(s): Alberto Flandes , Ángel García , Estelle Deau ,Linda SpilkerInstitution(s): 1. Instituto de Geofísica, Universidad NacionalAutónoma de México, UNAM, 2. Jet Propulsion Laboratory

212.06 – Size of Self-Gravity Wakes from CassiniUVIS Tracking Occultations and RingTransparency StatisticsWe compare two methods for determining the size of self-gravitywakes in Saturn’s rings. Analysis of gaps seen in UVIS

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occultations gives a power law distribution from 10-100m(Rehnberg etal 2017). Excess variance from UVIS occultationscan be related to characteristic clump widths, a method whichextends the work of Showalter and Nicholson (1990) to morearbitrary shadow distributions. In the middle A ring, we useresults from Colwell etal (2017) for the variance and results fromJerousek etal (2016) for the relative size of gaps and wakes toestimate the wake width consistent with the excess varianceobserved there. Our method gives:

W= sqrt (A) * E/T * (1+ S/W)

Where A is the area observed by UVIS in an integration period, Eis the measured excess variance above Poisson statistics, T is themean transparency, and S and W are the separation and width ofself-gravity wakes in the granola bar model of Colwell etal (2006).We find: W ~ 10m and infer the wavelength of the fastest growinginstability Lambda(TOOMRE) = S + W ~ 30m. This is consistent with the calculation of the Toomre wavelengthfrom the surface mass density of the A ring, and with the highestresolution UVIS star occultations.

Author(s): Larry W Esposito , Morgan Rehnberg , JoshuaE. Colwell , Miodrag SremcevicInstitution(s): 1. UCF, 2. University of Colorado

212.08 – A missing correction on the lags ofPrometheus and PandoraObservational data collected in 1995 during the passage of theEarth by the ring plane of Saturn indicated angular lags in thepredicted positions of Prometheus and Pandora. Using additionaldata the lags were confirmed, with Prometheus being about −19degrees of its estimated longitude and Pandora about 25 degrees.A possible chaotic relationship caused due to a 121:118 meanmotion resonance between the two satellites is currently acceptedto explain those lags. In the present work, we use a table of thelags of Prometheus and Pandora that have been measured alongthe time to infer the correspondence of the gravitationalinteraction between these two satellites. By the conservation ofthe angular momentum, one should expect a constant value forthe ratio of the lags of the satellites. However, there is an increasein this value over time, indicating that another non-mutualmechanism may influence the orbit of the satellites. Here weinvestigate what could cause this change in the lag ratio, forinstance, the periodic close encounters between Prometheus andthe F-ring.

Author(s): Thamiris De Santana , Othon Cabo WinterInstitution(s): 1. Sao Paulo State University

212.09 – Using four-body problems to exploreAegaeon's orbital evolutionSaturn's moon Mimas holds Aegaeon and an arc of debris in a 7:6corotation resonance. Compared with other similarly confinedmoon-arc systems, Aegaeon is closer to exact resonance andAegaeon is a fraction of the total mass in its arc. We investigatewhether these two phenomena are linked and whetherinteractions with other bodies drove Aegaeon's orbital evolutiontowards the center of the corotation site. We analyze numericalsimulations with multiple bodies initially in the same corotationsite as Aegaeon. During interactions with other bodies, weobserve changes in values that are constants in the relevant three-body problem that may provide evidence for this model of orbitalevolution in a corotation resonance.

Author(s): Joseph A'Hearn , Matthew M. HedmanInstitution(s): 1. University of Idaho

212.10 – What confines the rings of Saturn?The viscous spreading of planetary rings is believed to becounteracted by satellite torques, either through an individualresonance or through overlapping resonances (when the satellite

is close to the ring edge). For the A ring of Saturn, it has beencommonly believed that the satellite Janus alone can prevent thering from spreading via its 7:6 Lindblad resonance. We discussthis common misconception and show that, in reality, the A ringis confined by the contributions from the group of satellites Pan,Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas,whose resonances gradually decrease the angular momentum fluxtransported outward through the ring via density and bendingwaves. We further argue that this decrease in angular momentumflux occurs through the mechanism of ‘flux reversal’. We find that the Janus 7:6 torque is relatively feeble, as is thecomparable torque of the nearby small satellite Atlas, eachamounting to less than one-tenth of the angular momentumtransport carried by the A ring. But the cumulative torques of themany other satellite resonances in the A ring sufficiently reducethe angular momentum flux through the rings so that the torquesdue to Janus and Atlas are effective in confining the outer edge ofthe ring. Furthermore, we use the magnitude of the satellites’ resonancetorques to estimate the effective viscosity profile across the A ring,showing that it decreases from ~50 cm s at the inner edge toless than ~11 cm s at the outer edge. The gradual estimateddecrease of the angular momentum flux and effective viscosity areroughly consistent with results obtained by balancing theshepherding torques from Pan and Daphnis with the viscoustorque at the edges of the Encke and Keeler gaps, as well as theedge of the A ring. On the other hand, the Mimas 2:1 Lindblad resonance aloneseems to be capable of confining the edge of the B ring, andcontrary to the situation in the A ring, we show that the effectiveviscosity across the B ring is relatively constant at ~24-30 cm s.

Author(s): Radwan Tajeddine , Philip D. Nicholson ,Maryame El Moutamid , Pierre-Yves Longaretti , Joseph A.BurnsInstitution(s): 1. Cornell University, 2. Université de GrenobleAlpes (UGA)

212.11 – Preliminary Results from the CassiniRADAR Ring ObservationsIn its last year of operation, the Cassini spacecraft executed aseries of short highly inclined orbits that brought it close toSaturn’s rings. The Cassini RADAR instrument collected activeand passive data of the rings in five separate observations. Theseobservations provided a unique opportunity to obtain backscattermeasurements and relatively high-resolution brightnesstemperature measurements from the rings. Such measurementswere never before possible from the spacecraft or the Earth due tohigh range. Preliminary examination of the active data showsmajor ring structural features such as the Cassini Division, theEncke Gap, and the Keeler Gap. This presentation will showpreliminary processing results from the radar rings scans anddiscuss the calibration and processing issues. These ring scanmeasurements provide a 1-D profile of backscatter obtained at 2.2cm wavelength that complements similar passive profilesobtained at optical, infrared, and microwave wavelengths. Suchmeasurements can further constrain and inform models of thering particle composition and structure, and the local verticalstructure of the rings. This work is supported by the NASACassini Program at JPL - CalTech.

Author(s): Richard D. West , Michael A. Janssen , ZhimengZhang , Jeffrey N. Cuzzi , Yanhua Anderson , Gary Hamilton ,Charles ElachiInstitution(s): 1. Jet Propulsion Laboratory, 2. NASA AmesResearch CenterContributing team(s): Cassini RADAR Science Team

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213 – Titan213.01 – C/ C and N/ N isotopic ratios inHCN in the middle atmosphere of Titan fromCassini/CIRS dataOur study aims at constraining the C/ C and N/ N isotopicratios in HCN, the most abundant nitrile in Titan’s atmosphere,which can provide information on physical and chemical processoccurring during the formation and/or destruction of thismolecule.

Over the last decade, several estimations of the C/ C andN/ N isotopic ratios in HCN were performed from ground-

based, Herschel and Cassini observations (Bézard et al,2014). TheN/ N ratio lies in the range 56-76, which corresponds to half

of the N/ N ratio in N (major N-bearing molecule in Titan’satmosphere). This nitrogen isotopic fractionation mostlyoriginates from the photodissociation of N (Liang et al, 2007).The C/ C ratio lies in the range 75-108, in agreement with the

C/ C ratio in CH (major C-bearing molecule). Recent disk-averaged ALMA observations indicate C/ C and N/ Nratios equal to ∼90 and ∼72, respectively (Molter et al, 2016).

Vinatier et al (2007) derived N/ N and C/ C ratios in twodifferent regions (equator and north pole) from Cassini/CIRS(Composite InfraRed Spectrometer) observations at thebeginning of the Cassini mission. N/ N was similar for bothlatitudes while the C/ C ratio displayed a possibleenhancement at the equator.

We present here a new study of the C/ C and N/ Nisotopic ratios in HCN from CIRS. We analyzed limb observations(0.5 cm resolution) from northern winter to early spring atpoles, mid-latitudes and equator in order to investigate potentialspatial and seasonal changes of these isotopic ratios in Titan’smiddle atmosphere. These preliminary results will be presentedand compared with previous observations.

References: Bézard et al., Cambrigde University Press, 2014 Liang et al., The Astrophysical Jounral Letters, 2007 Molter et al., The Astronomical Journal, 2016 Vinatier et al., Icarus, 2007

Author(s): Christophe Mathé , Sandrine Vinatier , BrunoBézard , Conor A. NixonInstitution(s): 1. LESIA-Observatoire de Paris, 2. PlanetarySystems Laboratory, NASA-GSFC

213.02 – Chemical evolution of Titan’s aerosolanalogues under VUV irradiationSince the Cassini-CAPS measurements, organic aerosols areknown to be present and formed at high altitudes in the dilutedand partially ionized medium that is Titan’s ionosphere [1]. After production in the ionosphere, Titan’s aerosols evolvethrough microphysics during their sedimentation down to Titan’ssurface [2]. Starting with a few nanomers size in the upperatmosphere, they reach a fractal structure of a few hundredsnanometers close to the surface [3]. During sedimentation,aerosols are also submitted to solar irradiation. As laboratoryanalogs of Titan’s atmospheric aerosols (tholins) show a strongUV absorption [4], we suspect that VUV irradiation could alsoinduce a chemical evolution of Titan’s aerosols during theirdescent in Titan’s atmosphere.

The aim of this work ist to simulate the irradiation processoccuring on the aerosols in Titan’s atmosphere and to addresswhether this irradiation impacts the chemical composition of theorganic solids. First aerosol analogues were produced in a N -CH plasma discharge as thin organic films of a few hundreds ofnanometers thick [5]. Then those were irradiated at Lyman-αwavelength, the strongest VUV line in the solar spectrum, with ahigh photon flux on a synchrotron VUV beamline. We will present

and discuss the significant chemical evolutions observed on theanalogues after VUV irradiation by mid-IR absorptionspectroscopy. [1] Waite et al. (2009) Science , 316, p. 870 [2] Lavvas et al. (2011) Astrophysical Journal, 728:80 [3] Tomasko et al. (2008) Planetary and Space Science, 56, p. 669 [4] Mahjoub et al. (2012) Icarus 221, P. 670 [5] Carrasco et al. (2016) Planetary and Space Science, 128, p. 52

Author(s): Nathalie Carrasco , Lisseth Gavilan , SarahTigrine , Ludovic Vettier , Laurent Nahon , Pascal PernotInstitution(s): 1. SOLEIL, 2. University of Paris Sud, 3.University of Versailles Saint Quentin

213.03 – Photoreactivity of condensed species inTitan lower atmospherePhotochemical processes initiated in the thermosphere of Titan atabout 1000 km by the dissociation and the ionization of N andCH by the VUV solar photons lead to the formation of anumber of hydrocarbons and nitriles species. Some of thesespecies can condense in the troposphere and the lowerstratosphere of Titan (<100 km) according to the lowertemperatures measured by the HASI instrument onboard theHuygens probe . If the most energetic solar photons areabsorbed at higher altitude, longer wavelengths photons (λ > 300nm) can reach these lower atmospheric layers , ongoingpossible further solid-state chemistry as demonstratedexperimentally . We will present here an experimental studysimulating the reactivity of ices in the atmosphere of Titan andwill discuss the photoreactivity occurring in the loweratmospheric layers of Titan despite the absorption of the mostenergetic photons. Acknowledgments This work is supported by NASA Solar System Workings grant "Photochemistry in Titan’s Lower Atmosphere". The research workhas been carried out at the Jet Propulsion Laboratory, CaliforniaInstitute of Technology under a contract with the NationalAeronautics and Space Administration. NC acknowledges theEuropean Research Council for their financial support (ERCStarting Grant PRIMCHEM, grant agreement n°636829). References [1] Waite, J. H., et al., The process of Tholin formation in Titan’supper atmosphere, (2007), Science 316, 870-875. [2] Barth, E. L., Modeling survey of ices in Titan’s stratosphere,(2017), Planetary and Space Science 137, 20-31. [3] Fulchignoni, M., et al., In situ measurements of the physicalcharacteristics of Titan’s environment, (2005), Nature 438, 785-791. [4] Tomasko, M. G., et al., Rain, winds and haze during theHuygens probe’s descent to Titan’s surface, (2005), Nature 438,765-778. [5] Gudipati, M. S., et al., Photochemical activity of Titan’s low-altitude condensed haze, (2013), Nature Communications, 4:p1648.

Author(s): Benjamin Fleury , Murthy Gudipati , IsabelleCouturier-Tamburelli , Nathalie CarrascoInstitution(s): 1. Aix-Marseille Université, CNRS, PIIM, UMR7345, 2. Jet Propulsion Laboratory, California Institute ofTechnology, 3. LATMOS, Universite Versailles St Quentin, UPMCUniversite Paris 06, CNRS

213.04 – Isotopic composition of trace molecules inthe atmosphere of TitanHigh precision measurements of the isotopic composition of H, C,N and O in several molecules in the atmosphere of Titan haverecently been obtained by the Cassini-Huygens spacecraft,Submillimeter Array (SMA), and Atacama Large Millimeter Array(ALMA). We developed a one-dimensional photochemistry-transport model for methane, ethane, water, nitrogen and theirisomers and isotopologues. Our model identifies severalimportant physical, photolytic, and chemical processes that

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control the isotopic fractionation of these species in Titan'satmosphere. The model can reproduce most of the recentobservations. Implications of our current model forunderstanding the dynamical transport in the upper atmosphereand chemical evolution of the atmosphere are discussed.

Author(s): Mao-Chang Liang , Siteng Fan , Yuk YungInstitution(s): 1. Academia Sinica, 2. Caltech

213.05 – Seasonal evolution of Titan’s stratospherenear the poles from Cassini/CIRS dataWe report on the monitoring of the seasonal evolution nearTitan’s poles. Since 2010, we observe at Titan’s south pole astrong temperature decrease and the onset of a dramaticenhancement of several trace species such as complexhydrocarbons and nitriles (HC3N and C6H6 in particular)previously observed only at high northern latitudes (Coustenis etal. 2016 and references therein). This is due to the transition ofTitan’s seasons from northern winter in 2002 to northernsummer in 2017 and, at the same time, the advent of winter in thesouth pole, during which time species with longer chemicallifetimes remain in the north for a little longer undergoing slowphotochemical destruction, while those with shorter lifetimesdisappear, reappearing in the south. An opposite effect has beenexpected in the North, but not observed with any significantcertainty until 2016. We present here an analysis of nadir spectraacquired by Cassini/CIRS (Jennings et al., 2017) at highresolution in the past years and describe the newly observeddecrease in chemical abundances of the components in the North.From 2013 until 2016, the Northern polar region has shown atemperature increase of 10 K, while the South had shown a moresignificant decrease in a similar period of time. The chemicalcontent in the North is finally showing a clear depletion for mostmolecules since 2015 (Coustenis et al., 2017).

References: Coustenis et al., 2016, Icarus 270, 409-420 ;Coustenis et al., 2017, in preparation; Jennings et al., 2017,Applied Optics 56, no 18, 5274-5294.

Author(s): Athena Coustenis , Donald E. Jennings , RichardK. Achterberg , Georgios Bampasidis , Valeria Cottini , Conor A.Nixon , F. Michael FlasarInstitution(s): 1. Faculty of Physics, National andKapodistrian University of Athens, Panepistimioupolis, 2.Laboratoire d’Etudes Spatiales et d’Instrumentation enAstrophysique (LESIA), Observatoire de Paris, CNRS, UPMCUniv. Paris 06, Univ. Paris-Diderot, 5, place Jules Janssen, , 3.NASA Goddard Space Flight Center

213.06 – Influences of the Absorption andScattering of Haze Particles on the MolecularEmissions of Titan Extensive observations of the hazy atmosphere of Titan with theVisual Infrared Mapping Spectrometer (VIMS) on Cassinispacecraft since 2004 produced infrared spectra showingdistinctive spectral features of molecular emissions as well asabsorptions with haze continua. In order to properly calculate theexcitations and deexcitations of atmospheric molecules in thehazy atmosphere, we present a formulation of radiative transferequations, which include the scatterings and absorptions of hazeparticles as well as molecular emissions and absorptions. Weconstructed synthetic spectra of HCN, for example, using theradiative transfer equations and compared the resultant spectrawith HCN emission spectra from Keck II/NIRSPEC andCassini/VIMS observations available in literature. We present adiscussion about the quantitative influences of haze opacities onthe mixing ratios of HCN in the atmosphere of Titan.

Author(s): Sang J. KimInstitution(s): 1. Kyunghee Univ.

213.07 – A Comparative Analysis of SedimentTransport and Deposition Trends of the Sand Seas ofTitan and the Namib

Despite different atmospheric and grain compositionaldifferences, the similarity in the shape, size and spatial trends oflinear dunes of the Belet Sand Sea of Titan and the Namib SandSea suggest that comparisons of dune parameters between themwill yield a better understanding of dune forming processes.Titan’s main dune fields occupy the lowest elevation areas in theequatorial regions, with the exception of the lower Xanadu. Newanalyses of dune widths in the Belet Sand Sea support thecorrelation between dune width and latitude. Furthermore, duneswith larger widths and spacings are concentrated towards Belet’scenter. This may suggest that the elevation in the topographicbasin constrains dune size, or instead, that proximity to the sandsea margin influences dune size. There are larger dune-to-interdune ratios at lower elevations across Titan. This could be aresult of lower wind velocities which would cause greatersediment accumulation as opposed to bypassing. In the Namib,new analyses of dune width and spacing suggest elevation exertslittle to no control on general dune morphology. However, thereis an increase in the variability of dune spacing as elevationincreases. Our results corroborate previous studies indicating aconcentration of larger linear dunes in the center of the NamibSand Sea. This may suggest influence by variables other thanelevation, such as proximity to the dune field margin or varyingsand supply and wind parameters across the dune field. It’spossible that sediment supply and wind are more consistent onTitan’s surface than on Earth because we observe a predominanceof linear dunes on Titan. Further analyses of dune parameters inrelation to these controls, and the further delineation of thesevariables, will allow for a better understanding of sedimenttransport and deposition patterns in sand seas on Earth andTitan.

Author(s): Corbin Lewis , Bradley Bishop , Jani Radebaugh ,Eric ChristiansenInstitution(s): 1. Brigham Young University

213.08 – Constraints on the frequency distributionof small lakes and ponds on TitanIn many ways, Titan’s polar regions (particularly the north-polarregion) resemble a terrestrial wetlands environment, albeit withmarkedly different materials: a methane-ethane-nitrogendominated liquid modifying a water-ice and solid hydrocarbonlandscape. Portions of the landscape appears dissected bychannels, resulting in erosional and depositional features, and theregion is dotted with both smaller lakes and larger seas. Despitethese similarities, however, notable deviations from terrestrialfamiliarity provide clues to the formation and evolution of Titan’slandscape. Of note to this study is the size-frequency distributionof Titan’s lakes, which does not appear to follow a power-lawdistribution like terrestrial lakes. This may indicate a sizedependence to the origin or evolution of Titan’s lakes that isdissimilar to terrestrial lakes (see Hayes et al. 2016, Annu. Rev.Earth Planet. Sci., and references therein). This conclusion,however, is drawn from Cassini Synthetic Aperture Radar (SAR),the Visual and Infrared Mapping Spectrometer (VIMS) andImaging Science Subsystem (ISS) images, which cannot resolvelakes smaller than ~1 km^2. Sunglints from Titan’s lakes afford a method to constrain thedistribution of lakes and ponds at much smaller scales. We useVIMS 5-micron observations of Titan’s north polar region thatwere acquired under specular geometries to constrain thedistribution of ponds as small as 10s of meters in diameter. Weuse these results to extend the analysis of the size-frequencydistribution of Titan’s lakes to those two orders of magnitudesmaller in area, and discuss the implications these results havefor the formation of lacustrine basins in Titan’s polar landscapes.

Author(s): Jason M. Soderblom , Alexander HayesInstitution(s): 1. Cornell University, 2. Massachusetts Instituteof Technology

213.09 – A bright intra-dune feature on Titan andits implications for sand formation and transport

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Organic sands cover much of Titan’s equatorial belt, gathered intolongitudinal dunes about a kilometer wide and hundreds ofkilometers long. At the end of the Cassini era, questions of howsuch a vast volume of saltable material is or was created on Titanremain unanswered. At least two possible mechanisms suggestedfor forming sand-sized particles involve liquids: (1) evaporitedeposition and erosion and (2) flocculation of material within alake. Transporting sand from the lakes and seas of Titan’s poles tothe equatorial belt is not strongly supported by Cassiniobservations: the equatorial belt sits higher than the poles and nosheets or corridors of travelling sand have been identified. Thus,previous sites of equatorial surface liquids may be of interest forunderstanding sand formation, such as the suggested paleoseasTui and Hotei Regio. A newly identified feature in the VIMS datasits within the Fensal dune field but is distinct from thesurrounding sand. We investigate this Bright Fensal Feature(BFF) using data from Cassini VIMS and RADAR. Specifically, wefind spectral similarities between the BFF and both sand andHotei Regio. The RADAR cross sectional backscatter is similar toneighboring dark areas, perhaps sand covered interdunes. We usethis evidence to constrain the BFF’s formation history and discusshow this intra-dune feature may contribute to the processes ofsand transport and supply.

Author(s): Shannon MacKenzie , Jason W. Barnes ,Sebastien Rodriguez , Thomas Cornet , Jeremy Brossier , JasonM. Soderblom , Stephane Le Mouélic , Christophe Sotin ,Robert H Brown , Bonnie J. Buratti , Roger Nelson Clark ,Philip D. Nicholson , Kevin BainesInstitution(s): 1. Cornell University, 2. Institut de Physique duGlobe de Paris (IPGP) Université Paris Diderot, 3. Institute ofPlanetary Research, German Aerospace Center (DLR), 4. JetPropulsion Laboratory, California Institute of Technology,, 5.Laboratoire Astrophysique, Instrumentation et Modélisation(AIM), CNRS-UMR 7158, 10 Université Paris-Diderot,, 6. Lunarand Planetary Lab, University of Arizona, 7. MassachusettsInstitute of Technology, 8. Planetary Science Institute, 9.Universite de Nantes, 10. University of Idaho

213.10 – A karstic origin for the north polar lakesreveals a soluble TitanWe quantitatively test the karst hypothesis for the formation ofTitan's lakes by comparing their morphometry to that ofterrestrial karst lakes. Titan is the only place in our solar system other than the Earthknown to harbor stable surface liquids. While much has beenstudied and predicted about the liquid composition anddistribution, the origin of the lake basins remains unknown. Weuse spatial regularity derived from the morphology of these lakesto test the hypothesis that they could be karstic in origin. Earth’skarstic lakes are closed depressions that form when the bedrock isdissolved. Karstic depressions have several distinct features, suchas their elongation index and their diameter distributions. Theseare lognormal, a relationship that holds under the assumptionthat these lakes originated and evolved over a comparatively shortperiod of time. Furthermore, the spread in sizes of depressions issmall, indicating tightly constrained formation processes. In ourstudy, we use statistics to ascertain whether Titan’s lakes followsimilar karstic geomorphometric patterns. Cassini RADAR andISS observations of Titan’s north pole show that the equivalentradii of 224 lakes indeed follow a lognormal distribution just likeEarth’s karstic lakes, thus suggesting Earth-like processes may beforming Titan’s lakes.

Author(s): Rajani Dhingra , Jason W. Barnes , JaniRadebaugh , Matthew M. HedmanInstitution(s): 1. Brigham Young University, 2. University ofIdaho

213.11 – Principal Component Analysis of Titan’ssurface composition at Middle Latitudes We present an investigation of Titan’s surface spectra order todetermine the composition of Titan’s surface on a global scale andto identify and map the surfaces where water ice “bedrock” isexposed, despite the ongoing sedimentation of organic materialfrom the atmosphere. This work follows the method establishedby an analysis of Titan’s tropical surface from 30S to 30 Nlatitudes (Griffith et al. 2017, submitted for publication).Similarly, we conduct a Principal Components Analysis (PCA) ofthe 4 wavelengths that most clearly view Titan’s surface (1.1, 1.3,1.6, and 2.0 μm). However, here we investigate target Titan’smiddle latitudes extending to 60S to 60 N. In contrast to previousanalyses, which yield consistent results, this study identifies anddeconstructs the major spectral components of the surface on aglobal scale, without prior assumptions regarding the surfacecomposition and atmospheric scattering and absorption, asassumed from radiative transfer analyses. In addition, thisapproach by virtue of sampling the correlations among the 4096spectra that make up a VIMS cube can identify subtle spectralfeatures that would not be apparent in a single spectrum. The PCA analysis is conducted on over 100,000 VIMS spectra todetermine the spectral trends that define the greatest spectralvariance (the principal component) as well as successively lesserorthogonal correlations between the I/F values at eachwavelength. The orthogonal spectral trends are derived bycalculating the eigenvalues and eigenvectors of the covariancematrix, defined by the I/F values at the 4 window wavelengths ofeach cube and their deviations from their mean values. This presentation will discuss the PCA analysis and compare ourderived compositional maps of Titan’s surface with Radar maps ofthe topography and morphology, to entertain questions regardingthe geology of Titan’s surface the age of its atmosphere.

Author(s): Caitlin Ann Griffith , Paulo F. Penteado ,Catherine Neish , Rosaly M.C LopesInstitution(s): 1. JPL, 2. University of Arizona, 3. University ofWestern Ontario

213.12 – Dynamics of Atmospheric Waves In a HazyAtmosphere: Implications for Titan and PlutoWe present a dynamical model of atmospheric gravity wavespropagating in a stable atmosphere in the presence of small-sizeparticulates. We consider a two-way interaction: (i) the effect ofatmospheric mass-loading on the propagation of the waves and(ii) the dynamical forcing of the haze particle motion in thepresence of variable atmospheric winds. The model illustrates theeffect on the vertical distribution of haze particles due to wave-induces vertical winds and wind gradients. The results arepresented in the context of Titan’s atmosphere and Cassiniobservations.

Author(s): Katia MatchevaInstitution(s): 1. University of Florida

214.01 – Spatial Distribution of the Forbidden 1.707mm Rovibronic Emission on Io Io’s forbidden SO 1.707 mm rovibronic transition was discoveredin 1999 when the satellite was observed with the NIRSPECspectrometer on the Keck telescope while in eclipse [1]. Theemission, at the time indicative of a rotational temperature of1000 K, was attributed to SO molecules in the excited a D state,ejected as such from the vent at a thermodynamic quenchingtemperature of ~1500 K. We suggested Loki as its source, a

volcano that was exceptionally active during this period. Insubsequent years we found that the disk-averaged SO emissionvaries substantially over time [2]. In November 2002 we observedIo in eclipse with Keck’s NIRSPEC coupled to the Adaptive Optics(AO) system, and identified a latitudinal variation in SO: mostemission came from the equator and the south, and practically noemission was detected in the north [3]. To further investigate the nature of the SO emission, we observed

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Io in eclipse with the near-infrared integral field spectrographOSIRIS, coupled to the AO system, on the Keck II telescope on UT27 July 2010 and 25 December 2015. On the latter date weobserved simultaneously with the NIRSPEC spectrometer at ahigh spectral resolution (R ~ 25,000). On these dates Callisto andGanymede, resp., were close enough to be used for wavefrontsensing. The angular resolution of our images is ~0.1”, or ~10resolution elements across Io’s disk. The emission is extended;preliminary results show that in 2010 most of the emissionoriginated in the north, and in 2015 it appeared to be moreconfined to the equatorial region. Potential connections to activevolcanoes, or absence thereof, and model fits to the emissionbands including LTE vs non-LTE contributions will be discussed.

[1]: de Pater, I., et al., 2002. Icarus, 156, 296-301. [2]: Laver, C., et al. 2007. Icarus, 189, 401-408. [3]: de Pater, I. et al., 2007. Icarus, 191, 172-182.

Author(s): Imke de Pater , Katherine de Kleer , MateAdamkovicsInstitution(s): 1. Caltech, 2. UC, Berkeley

214.02 – Testing Planetary Volcanism Models withMulti-Wavelength Near Infrared Observations ofKilauea Flows and FountainsUsing remote sensing of planetary volcanism on objects such asIo to determine eruption conditions is challenging because theemitting region is typically not resolved and because exposed lavacools so quickly. A model of the cooling rate and eruptionmechanism is typically used to predict the amount of surface areaat different temperatures, then that areal distribution isconvolved with a Planck blackbody emission curve, and thepredicted spectra is compared with observation. Often the broadnature of the Planck curve makes interpretation non-unique.However different eruption mechanisms (for example cooling firefountain droplets vs. cooling flows) have very different area vs.temperature distributions which can often be characterized bysimple power laws. Furthermore different composition magmashave significantly different upper limit cutoff temperatures. Inorder to test these models in August 2016 and May 2017 weobtained spatially resolved observations of spreading Kilaueapahoehoe flows and fire fountains using a three-wavelength near-infrared prototype camera system. We have measured the area vs.temperature distribution for the flows and find that over arelatively broad temperature range the distribution does follow apower law matching the theoretical predictions. As oneapproaches the solidus temperature the observed area dropsbelow the simple model predictions by an amount that seems tovary inversely with the vigor of the spreading rate. At thesehighest temperatures the simple models are probably inadequate.It appears necessary to model the visco-elastic stretching of thevery thin crust which covers even the most recently formedsurfaces. That deviation between observations and the simplemodels may be particularly important when using such remotesensing observations to determine magma eruption temperatures.

Author(s): Robert R. Howell , Jani Radebaugh , Rosaly M.CLopes , Laura Kerber , Anezina Solomonidou , Bryn WatkinsInstitution(s): 1. Brigham Young University, 2. CaliforniaInstitute of Technology, 3. Jet Propulsion Laboratory, CaliforniaInstitute of Technology, 4. Univ. of Wyoming

214.04 – Numerical Models of Europan OceanDynamics: Sensitivity to Fluid PropertiesEuropa possesses a global liquid water ocean overlain by an iceshell that mediates heat flux from the deeper interior. Since nodirect measurements of ocean dynamics and chemistry arepresently available, yet are crucial for assessing the satellite'spotential habitability, oceanographic processes must be inferredfrom other observations and/or through numerical andlaboratory experiments. We use numerical thermal convectionsimulations to test the sensitivity of global ocean dynamics touncertainties in fluid properties that depend on the poorly

constrained ocean salinity as parameterized by the Prandtlnumber, Pr. This dimensionless ratio of viscous to thermaldiffusivities is expected to be Pr~7 for pure water and Pr~14 forseawater with a salinity that is slightly higher than that of theterrestrial ocean. In contrast, Pr~1 may be appropriate when(turbulent) eddy diffusivity estimates are employed. Given thisrange of possible values, we determine how the ocean currents,heat transport, and ice-ocean coupling vary as a function ofPrandtl number and assess whether their behaviors may be usedto help constrain Europa’s ocean salinity.

Author(s): Krista M. Soderlund , Britney E Schmidt , DonBlankenshipInstitution(s): 1. Georgia Institute of Technology, 2. Universityof Texas Institute for Geophysics

214.05 – Permeability and Hydration State ofEuropa’s Rocky InteriorWe will present radial structure and composition models forEuropa that include self-consistent thermodynamics of allmaterials, developed using the PlanetProfile software. We willfocus on the potential hydration states and porosity of Europa’srocky interior. Scaling of porosity and permeability to conditionsin Earth’s upper mantle suggest the upper 10 km or more ofEuropa’s crust is permeable. We will compare these results to thesimilar predictions of thermal fracturing models previouslyapplied to Europa and other icy ocean worlds. If Europa retainedmuch of its formation heat, the lower part of its rocky mantleshould be anhydrous, with solid state convection aiding in thecooling and hydration of the lower layer. Hydration of the upperlayer implies lower bulk and shear moduli than typicallyconsidered, and thus more heat from tidal dissipation. We willexamine the implications for producing hydrogen and otherreductants from water-rock alteration and radiolysis of water.

Author(s): Steven Vance , Christopher R. Glein , AlexisBouquet , William B. McKinnon , Fabio CammaranoInstitution(s): 1. Jet Propulsion Laboratory, Caltech, 2.Southwest Research Institute, 3. Universita Roma Tre, 4.Washington University

214.06 – Ganymede’s stratigraphy and craterdistributions in Voyager and Galileo SSI images:results from the anti-jovian hemisphereCrater size distributions are a valuable tool in planetarystratigraphy to derive the sequence of geologic events. In thisstudy, we extend our previous work [1] in Ganymede’s sub-jovianhemisphere to the anti-jovian hemisphere. For geologic mapping,the map by [2] is used as a reference. Our study providesgroundwork for the upcoming imaging by the JANUS cameraaboard ESA’s JUICE mission [3]. Voyager-2 images arereprocessed using a map scale of 700 m/pxl achieved for parts ofthe anti-jovian hemisphere. To obtain relative ages from craterfrequencies, we apply an updated crater scaling law for crateringinto icy targets in order to derive a crater production function forGanymede [1]. Also, we adopt the Poisson timing analysis methoddiscussed and implemented recently [4] to obtain relative (andabsolute model) ages. Results are compared to those from thesub-jovian hemisphere [1] as well as to support and/or refine theglobal stratigraphic system by [2]. Further emphasis is placed onlocal target areas in the anti-jovian hemisphere imaged by GalileoSSI at regional map scales of 100 to 300 m/pxl in order to studylocal geologic effects and processes. These areas incorporate (1)dark and (2) light tectonized materials, and (3) impact cratermaterials including an area with numerous secondaries from raycrater Osiris. References: [1] Wagner R. et al. (2014), DPSmeeting #46, abstract 418.09. [2] Collins G. et al. (2013), U.S.G.S.Sci. Inv. Map 3237. [3] Della Corte V. et al. (2014), Proc. SPIE9143, doi:10.1117/12.2056353. [4] Michael G. et al. (2016), Icarus277, 279-285.

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Author(s): Roland Josef Wagner , Nico Schmedemann ,Katrin Stephan , Stephanie Werner , Boris A Ivanov , ThomasRoatsch , Ralf Jaumann , Pasquale PalumboInstitution(s): 1. CEED, Univ. of Oslo, 2. DLR, Institute ofPlanetary Research, 3. Inst. for Dynamics of Geospheres, 4. Inst.of Geosciences, FU Berlin, 5. Univ. degli Studi di Napoli

214.07 – Ice particle size variations and possiblenon-ice materials on Ganymede's and Callisto'ssurfaceBand depth ratios (BDRs) of the major H O-ice absorptions inthe spectra of the Jovian satellites Ganymede and Callistoacquired by the Galileo-NIMS spectrometer have been found tobe mainly unaffected by the abundance of the dark non-icematerial and therefore provide semi-quantitative indicators ofvariations in the H O-ice particle sizes across their surfaces.Intriguingly, H O-ice particle sizes vary continuously withgeographic latitude on both satellites. Ice particles on Callistoappear slightly larger at low and mid latitude than observed onGanymede, whereas the BDR values converge toward the polesindicating similarly small ice particle sizes. This smoothlatitudinal trend on both satellites may be related to the surfacetemperatures and possible thermal migration of water vapor tohigher latitudes and grain welding at lower latitudes. It is notexpected that the observed relationship between the BDRs andH O-ice particle sizes occurs for mixtures with every non-icematerial expected to exist on planetary surfaces. Therefore, icemixtures with a variety of considered non-ice materials such ascarbon-rich materials, phyllosilicates and salts have beencalculated and the validity of the relationship tested depending ondifferent H O-ice abundances and particle sizes. The relationshipseems to be valid for most materials if the amount of the non-icematerial in the mixture does not exceed 10 percent. Best resultsacross the full range of percentage could be achieved for carbon-rich material and hydroxylated phyllosilicates, which are expectedto be the major constituent of carbonaceous chondrites. Incontrast, significant amounts of hydrated material, as identifiedon Europa, significantly changes the BDRs and could not fullyexplain the global trend.

Author(s): Katrin Stephan , Harald Hoffmann , Charles A.Hibbitts , Roland Wagner , Ralf JaumannInstitution(s): 1. APL, 2. German Aerospace Center

214.08 – Modelling Stresses on Icy Satellites:Upgrading SatStressGUISatStressGUI is a program that calculates surfacestresses resulting from candidate stress sources,specifically: diurnal tidal forces, nonsynchronousrotation, ice shell thickening, obliquity, and orbitalmigration on icy and rocky satellites. SatStressGUI isdesigned to enable quick calculations and easy to createstress field visuals. Here we report on recent upgradesto SatStressGUI; specifically, enabling it to calculatestresses resulting from obliquity driven stressing in aviscoelastic regime. We define obliquity as the tilt of thesatellite’s equatorial plane relative to the orbital plane.Obliquity driven stresses cause asymmetric stress fieldsabout the equator. The resulting asymmetries can affectthe orientation of the principal stresses and therebyresult in the arcuate (as opposed to boxy) cycloidpatterns seen in some icy satellites and allow forfractures to propagate across the equator. In the past,SatStressGUI had the ability to calculate obliquitystresses only for an elastic body; however, icy satellitesare better described as viscoelastic bodies. As a result ofour recent upgrades; these stress fields, which canresult in the formation of surface features such as thelineaments and cycloids found on Europa, can now bemore accurately simulated. We used an obliquity modelthat follows the calculations the calculations of Hermeset al. (Icarus, 215, 417–438, 2011), which takes a closerlook at the effects of a non-zero obliquity in aviscoelastic regime. By the calculations of Hermes et al.

(Icarus, 215, 417–438, 2011), accounting for viscoelasticbehavior of ice could result in a westward shift of theentire stress field. By permitting simulation of surfacefeatures from various tidal stresses and comparisonthem to observations, SatStressGUI can help us gaininsight into icy bodies’ deformation history: a historywhich can better informing our predictions about theinteriors and geological histories of satellites such asEuropa.

Author(s): Chad Harper , Robert T. Pappalardo , AlexPatthoff , Nhu DoanInstitution(s): 1. Columbia University, 2. Grinnell College, 3.Jet Propulsion Laboratory, California Institute of technology , 4.Planetary Science Institute

214.09 – The Planned Europa Clipper Mission:Exploring Europa to Investigate its HabitabilityA key driver of planetary exploration is to understand theprocesses that lead to habitability across the solar system. In thiscontext, the science goal of the planned Europa Clipper missionis: Explore Europa to investigate its habitability. Following fromthis goal are three Mission Objectives: 1) Characterize the ice shelland any subsurface water, including their heterogeneity, oceanproperties, and the nature of surface-ice-ocean exchange; 2)Understand the habitability of Europa's ocean throughcomposition and chemistry; and 3) Understand the formation ofsurface features, including sites of recent or current activity, andcharacterize localities of high science interest. Folded into thesethree objectives is the desire to search for and characterize anycurrent activity. To address the Europa science objectives, a highly capable andsynergistic suite of nine instruments comprise the mission'sscientific payload. This payload includes five remote-sensinginstruments that observe the wavelength range from ultravioletthrough radar, specifically: Europa UltraViolet Spectrograph(Europa-UVS), Europa Imaging System (EIS), MappingImaging Spectrometer for Europa (MISE), Europa THErMalImaging System (E-THEMIS), and Radar for EuropaAssessment and Sounding: Ocean to Near-surface (REASON). Inaddition, four in-situ instruments measure fields and particles:Interior Characterization of Europa using MAGnetometry(ICEMAG), Plasma Instrument for Magnetic Sounding (PIMS),MAss Spectrometer for Planetary EXploration (MASPEX), andSUrface Dust Analyzer (SUDA). Moreover, gravity science can beaddressed via the spacecraft's telecommunication system, andscientifically valuable engineering data from the radiationmonitoring system would augment the plasma dataset. Workingtogether, the planned Europa mission’s science payload wouldallow testing of hypotheses relevant to the composition, interior,and geology of Europa, to address the potential habitability of thisintriguing moon.

Author(s): Robert T. Pappalardo , David A. Senske , HajeKorth , Diana L. Blaney , Donald D Blankenship , Philip RChristensen , Sascha Kempf , Carol Anne Raymond , Kurt D.Retherford , Elizabeth P. Turtle , J. Hunter Waite , Joseph H.Westlake , Geoffrey Collins , Murthy Gudipati , Jonathan I.Lunine , Carol Paty , Julie A. Rathbun , James Roberts ,Britney E Schmidt , Jason M. SoderblomInstitution(s): 1. Arizona State University, 2. CornellUniversity, 3. Georgia Institute of Technology, 4. Jet PropulsionLaboratory, California Institute of Technology, 5. Johns HopkinsUniversity Applied Physics Laboratory, 6. MassachusettsInstitute of Technology, 7. Planetary Science Institute, 8.Southwest Research Institute, 9. University of Colorado, 10.University of Texas Institute for Geophysics, 11. Wheaton CollegeContributing team(s): The Europa Clipper Science Team

214.10 – Expected Recovery of Europa'sGeophysical Attributes with Clipper GravityScience Investigation

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The primary gravity science objective of NASA’s Clipper missionto Europa is to confirm the presence or absence of a globalsubsurface ocean beneath Europa's icy crust. Gravity fieldmeasurements obtained with a radio science investigation canreveal much about Europa's interior structure. Here, we conductextensive simulations of the radio science measurements with theanticipated spacecraft trajectory and attitude (17F12V2) andassets on the spacecraft and the ground, including antennaorientations and beam patterns, transmitter characteristics, andreceiver noise figures. In addition to two-way Dopplermeasurements, we also include radar altimeter crossover rangemeasurements. We concentrate on +/-2 hour intervals centeredon the closest approach of each one of the 46 flybys. Ourcovariance analyses reveal the precision with which the tidal Lovenumber k2, second-degree gravity coefficients C20 and C22, andhigher-order gravity coefficients can be determined. The resultsdepend strongly on the Deep Space Network (DSN) assets thatare deployed to track the spacecraft. We find that some DSNallocations are sufficient to conclusively confirm the presence orabsence of a global ocean and to evaluate whether the ice shell ishydrostatic.

Author(s): Ashok Kumar Verma , Jean-Luc MargotInstitution(s): 1. UCLA

214.13 – The distribution of Enceladus water-groupneutrals in Saturn’s MagnetosphereSaturn’s magnetosphere is unique in that the plumes from thesmall icy moon, Enceladus, serve at the primary source for heavyparticles in Saturn’s magnetosphere. The resulting co-orbitingneutral particles interact with ions, electrons, photons and otherneutral particles to generate separate H O, OH and O tori.Characterization of these toroidal distributions is essential forunderstanding Saturn magnetospheric sources, composition anddynamics. Unfortunately, limited direct observations of thesefeatures are available so modeling is required. A significantmodeling challenge involves ensuring that either the plasma andneutral particle populations are not simply input conditions butcan provide feedback to each population (i.e. are self-consistent).Jurac and Richardson (2005) executed such a self-consistentmodel however this research was performed prior to the return ofCassini data. In a similar fashion, we have coupled a 3-D neutralparticle model (Smith et al. 2004, 2005, 2006, 2007, 2009, 2010)with a plasma transport model (Richardson 1998; Richardson &Jurac 2004) to develop a self-consistent model which isconstrained by all available Cassini observations and currentfindings on Saturn’s magnetosphere and the Enceladus plumesource resulting in much more accurate neutral particledistributions. Here a new self-consistent model of the distributionof the Enceladus-generated neutral tori that is validated by allavailable observations. We also discuss the implications forsource rate and variability.

Author(s): Howard T. Smith , John D. RichardsonInstitution(s): 1. Johns Hopkins Applied Physics Lab, 2.Massachusetts Institute of Technology

214.15 – On the Determination of the Mass ofHeleneHelene is the largest of Dione's co-orbital satellites; it libratesabout the L Lagrangian point. The smaller co-orbital,Polydeuces, librates about the L Lagrangian point. Since theirdiscoveries, we have included both as members of the Saturniansatellite system for ephemeris development because observationsof their motions lead to a determination of the mass of Dione.Theoretically, it should also be possible to infer the mass of theco-orbitals by observing their effect on the motion of Dione. Ofcourse, because of their small sizes, Helene's mean radius is 18km and that of Polydeuces is 1.3 km, their masses are presumedto be small. Consequently, very precise observations of Dione arerequired to be able to detect perturbations due to them. Webelieve that the Doppler tracking of Cassini during five closeflybys of Dione may have provided a detection of Helene(Polydeuces is too small). The Doppler data were acquired for the

purpose of determining Dione's gravity field. However, those dataalso provide a strong constraint on the orbital position of Dione.We included Helene's GM as one of the gravity parameters in ourdevelopment of our post-Cassini Saturnian satellite ephemeris.That analysis relies on an extensive data set including the Cassiniradiometric tracking. Our formal data fit yielded a statisticallysignificant, but quite small, value for the GM, suggesting thatHelene has an extremely low density. Perhaps it is a very porousbody or a loose conglomeration of material collected at L Wealso examined possible bounds on the GM and found thatassuming a massless Helene degrades the fit of the Dione orbit tothe data. Moreover, assuming masses consistent with significantdensities also degrades the fit. Our conclusion is that the actualGM of Helene is at least as large as our formal estimated value,but not large enough to be consistent with a 0.5 g cm density.

Author(s): Robert Arthur JacobsonInstitution(s): 1. Jet Propulsion Laboratory

214.16 – Viscoelastic Relaxation of Craters andThermal Histories of the Mid-Sized Icy Satellites ofSaturnCrater relaxation can be used as a probe of subsurfacetemperature structure in planetary bodies. The relaxation rate ofa crater is controlled by the rheology of the medium in which thecrater is emplaced. Because the rheology is a strong function oftemperature, the crater relaxation can be used to constrain theheat flux out of the body since the time of crater formation. Whencombined with models of thermal evolution, the degree ofrelaxation can be used to determine the ages of craters on aplanetary surface. Here we considered large (50 – 200 km diameter) impact craterson Saturn’s mid-sized satellites Tethys, Dione, Rhea, and Iapetus.We model viscoelastic relaxation of crater topography using thefinite-element code CitcomVE for a variety of ice shellthicknesses, differentiation states, temperature profiles and craterdiameters. We consider satellites both with and withoutsubsurface oceans. If the ice shell is conductive, the relaxation rate is controlled bythe ice shell thickness, but only weakly. Once the ice thicknessexceeds the crater diameter, additional thickening has little effecton the relaxation time; the topography does not interact with thedeeper ice layer. If the ice shell convects, then the relaxation isnearly independent of the total ice thickness. Rather, on thetimescales relevant to planetary evolution (Gy), warm convectingice basically behaves like a fluid, and the degree of relaxation iscontrolled by the strength of the cold outer portion of the iceshell. We thus find that it is very difficult to distinguish between aconvecting ice shell with a stagnant lid, and a conducting ice shellover a subsurface ocean, on the basis of crater relaxation alone.The degree of crater relaxation thus gives us the thickness of theelastic part of the ice shell, and our model results can becompared against measurements of crater relaxation on thesefour satellites. In the present models, the temperature structure is notcalculated, but imposed. Combination of the present craterrelaxation results with a model of thermal evolution is ongoing inorder to evaluate the geophysical self-consistency of the thermalstructures considered here.

Author(s): James Roberts , Cynthia B. PhillipsInstitution(s): 1. Jet Propulsion Laboratory, 2. Johns HopkinsApplied Physics Laboratory

214.17 – Crater densities within young, largecraters on Rhea and Dione: Towardsunderstanding the recent Saturnian bombardmentThe cratering flux for the inner Solar System is partiallyconstrained by geochronological measurements of returned lunarsamples and martian meteorites combined with cratering studies.For the outer Solar System, minimal constraints on the

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bombardment history are derived from dynamical simulations,historical observations of cometary impacts onto the gas giants,and cratering studies. Here, in order to specifically resolve thecratering flux experienced by the Saturnian system, we use highresolution Cassini Imaging Science Subsystem (ISS) data toconduct crater counts on the floors of young, large craters onRhea and Dione to investigate their relative crater formation age.These two mid-sized moons of Saturn have been shown to havedissimilar crater distributions, which may imply impacts bydifferent populations. Crater diameter and locations of observedsmall craters between ~100s of meters to ~10s of kilometerswithin large craters are recorded, where the limit of the smallestcrater observable is constrained by the image resolution. Relativecrater ages are compared through their cumulative crater density,and populations via the standard R-plot. Ultimately, craterdensities within young, large craters on these moons can becompared with crater ages inferred from crystallinity studiesusing Cassini VIMS data to refine our understanding of the outerSolar System bombardment.

Author(s): Carolina Rodriguez Sanchez-Vahamonde ,Edgard G. Rivera-Valentin , Michelle KirchoffInstitution(s): 1. Arecibo Observatory (USRA), 2. SouthwestResearch Institution

214.18 – Water ice and sub-micron ice particles onTethys and MimasIntroduction We present our ongoing work, mapping the variation of the mainwater ice absorption bands, and the distribution of the sub-micron particles, across Mimas and Tethys’ surfaces usingCassini-VIMS cubes acquired in the IR range (0.8–5.1 μm). Wepresent our results in the form of maps of variation of selectedspectral indicators (depth of absorption bands, reflectance peakheight, spectral slopes).

Data analysis VIMS acquires hyperspectral data in the 0.3–5.1 μm spectralrange. We selected VIMS cubes of Tethys and Mimas in the IRrange (0.8–5.1 μm). For all pixels in the selected cubes, wemeasured the band depths for water-ice absorptions at 1.25, 1.5and 2.02 μm and the height of the 3.6 μm reflection peak.Moreover, we considered the spectral indictors for particlessmaller than 1 µm [1]: (i) the 2 µm absorption band is asymmetricand (ii) it has the minimum shifted to longer λ; (iii) the banddepth ratio 1.5/2.0 µm decreases; (iv) the reflection peak at 2.6µm decreases; (v) the Fresnel reflection peak is suppressed; (vi)the 5 µm reflectance is decreased relative to the 3.6 µm peak. Tocharacterize the global variation of water-ice band depths, and ofsub-micron particles spectral indicators, across Mimas andTethys, we sampled the two satellites’ surfacees with a 1°x1° fixed-resolution grid and then averaged the band depths and peakvalues inside each square cell.

3. Results For both moons we find that large geologic features, such as theOdysseus and Herschel impact basins, do not correlate with waterice’s abundance variation. For Tethys, we found a quite uniformsurface on both hemispheres. The only deviation from thispattern shows up on the trailing hemisphere, where we notice twonorth-oriented, dark areas around 225° and 315°. For Mimas, theleading and trailing hemispheres appear to be quite similar inwater ice abundance, the trailing portion having water iceabsorption bands lightly more suppressed than the leading side.

References [1] Clark, R., et al., 2013. Observed ices in the solar system. In:Gudipati, M. S., Castillo-Rogez, J. (Eds.), The Science of SolarSystem Ices. Vol. 356. Astrophysics and Space Science Library,Springer Science+Business Media New York, p. 3.

Author(s): Francesca Scipioni , Tom Nordheim , RogerNelson Clark , Emiliano D'Aversa , Dale P. Cruikshank ,Federico Tosi , Paul M. Schenk , Jean-Philippe Combe , CristinaM. Dalle OreInstitution(s): 1. Bear Fight Institute, 2. INAF/IAPS, 3. JPL, 4.LPI, 5. NASA Ames Research Center, 6. PSI, 7. SETI

214.19 – Orbital and Photometric Analysis of theInner Uranian Satellites from Hubble ImagesWe continue our exploration of the dynamics of the thirteendensely-packed inner Uranian satellites. Using over 830 long-exposure images taken during 2003-2013 by the Hubble SpaceTelescope through broadband filters, we have obtainedastrometry for twelve of the thirteen moons (excluding Cordelia)and derived Keplerian orbital elements including the influence ofUranus’s oblateness. Analysis of the libration caused by theBelinda:Perdita 44:43 mean-motion resonance implies thatBelinda has roughly 26 times the mass of Perdita. We also seeevidence of forced eccentricity in the orbits of several moons dueto currently unknown perturbations. We will present our mostrecent findings on these topics as well as the photometrically-obtained rotational state of Perdita.

Author(s): Robert S French , Mark R Showalter , Imke dePater , Jack J. LissauerInstitution(s): 1. NASA ARC, 2. SETI Institute, 3. University ofCalifornia, Berkeley

214.20 – Physical Constraints on the Ices presenton Triton's SurfaceTriton is the largest distant satellite of the solar system and wasprobably captured from the Transneptunian population byNeptune. It is mainly covered by N2 , CO, CO2 , CH4 and H2O insolid state and, except for H2O and CO2 , these species are alsopresent in gas phase (with a thin N2 rich atmosphere, with CH4and CO traces, see Lellouch et al., 2011, for instance). Sublimationand recondensation of the volatile species could lead togeographical and temporal variation, and could participate to theformation of complex chemical compounds formed fromphotochemistry occurring in the atmosphere (Krasnopolsky andCruikshank, 1999) or from irradiation of N2 :CH4 :CO layers(Moore and Hudson, 2003). We present new analyses based on observations that have beenperformed in the near Infrared at the VLT-ESO with SINFONIfrom 2010 to 2013 at a spectral resolution ranging from 1500 to4000, in order to give new constraints on the chemical andphysical properties of the surface. Several models based on theHapke theory (Hapke, 1993) have also been tested in order toconstrain the abundance, the grain size and the state of the majorices (N2 , CH4 , CO, CO2 , H2O) as well as an attempt to identifyother species. For this purpose, we use new optical constants ofCO2 performed at 35 and 54K. We confirm the presence of deep N2 layers in which CO and CH4are diluted. Our models highly support the presence of pure CH4ice that can explain the enhancement of the CH4/N2 gas ratio inthe atmosphere over what would be expected from ideal mixing.Our results also suggest significant smaller particles of CO2 andH2O than that reported in Quirico et al. (1999). H2O is expectedto be present in its crystalline phase and CO2 spectral bands arecompatible with a highly crystalline structure. Our models alsosuggest that CO2 is probably spread over a large area of the Tritonsurface. Our analyses do not support the presence of higher orderhydrocarbons, such as those reported by Merlin (2015) on thesurface of Pluto.

Author(s): Frederic Merlin , Emmanuel Lellouch , EricQuirico , Bernard SchmittInstitution(s): 1. LESIA-Observatoire de Paris, CNRS, UPMCUniv Paris 06, Univ. Denis Diderot, Sorbonne Paris Cite, 2. Univ.Paris 6, Paris, France. Institut de Planetologie et dAstrophysique de Grenoble (IPAG), Univ. Grenoble Alpes/CNRS-INSU, UMR 5274

214.21 – The Irregular Moons of Saturn

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The 38 irregular moons of Saturn, all but Phoebe discoveredbetween 2000 and 2007, outnumber the planet's classicalsatellites. Observations from the ground and from near-Earthspace have revealed orbits, sizes, and colors and have hinted atthe existence of dynamical families, indicative of collisionalevolution and common progenitors. More recently, remoteobservations of many irregular satellites with the Cassinispacecraft produced lightcurves that helped determine rotationalperiods, coarse shape models, potential hemispheric colorheterogeneities, and other basic properties.

From Cassini, a total of 25 Saturnian irregulars have beenobserved with the ISS camera. Their rotational periods rangefrom 5.45 h to 76.13 h. The absence of fast rotators is evident.Among main-belt asteroids of the same size range (~4 to ~45km), one third of the objects have faster rotations, indicating thatmany irregulars should be low-density objects.

While the origin of the irregulars is still debated, capture ofcomets via three-body interactions during giant planetsencounters does the best job thus far at reproducing the observedprograde/retrograde orbits. Data from the ground, near-Earthspacecraft, and Cassini as well as modeling results suggest thepopulation visible today has experienced substantial collisionalevolution. It may be that only Phoebe has survived relativelyintact. The small particle debris drifts toward Saturn by P-R drag,with most of it swept up by Titan. Only remnants of this processare visible today.

Our current knowledge on the Saturnian irregulars will besummarized in a chapter [1] in the book "Enceladus and the IcyMoons of Saturn" [2]. The talk will give an overview on thechapter's content, which covers the following topics: Orbital"architecture" (a,e,i), sizes and colors, Cassini observations andresults, Phoebe, origin, an outlook.

[1] Denk, T., Mottola, S., Tosi, F., Bottke, W.F., Hamilton, D.P.(2018): The Irregular Satellites of Saturn. In: Enceladus and theIcy Moons of Saturn (Schenk, P. et al., eds.), Space Science Series,The University of Arizona Press. In press. [2] See http://www.uapress.arizona.edu/Books/bid2726.htm

Author(s): Tilmann Denk , Stefano Mottola , Federico Tosi ,William Bottke , Douglas P. HamiltonInstitution(s): 1. DLR, 2. Freie Universität, 3. INAF-IAPS, 4.SwRI, 5. University of Maryland

214.22 – Mapping Cryo-volcanic Activity fromEnceladus’ South Polar RegionUsing Cassini images taken of Enceladus’ south polar plumes atvarious times and orbital locations, we are producing maps oferuptive activity at various times. The purpose of this experimentis to understand the mechanism that controls the cryo-volcaniceruptions.The current hypothesis is that Tiger Stripe activity ismodulated by tidal forcing, which would predict a correlationbetween orbital phase and the amount and distribution oferuptive activity. The precise nature of those correlations dependson how the crust is failing and how the plumbing system isorganized.

We use simulated curtains of ejected material that aresuperimposed over Cassini images, obtained during thirteendifferent flybys, taken between mid-2009 and mid-2012. Each setrepresents a different time and location in Enceladus’ orbit aboutSaturn, and contains images of the plumes from various angles.Shadows cast onto the backlit ejected material by the terminatorof the moon are used to determine which fractures were active atthat point in the orbit. Maps of the spatial distribution of eruptive activity at variousorbital phases can be used to evaluate various hypotheses aboutthe failure modes that produce the eruptions.

Author(s): Mattie Tigges , Joseph N. SpitaleInstitution(s): 1. Planetary Science Institute, 2. University ofArizona

214.23 – Extenstional terrain formation in icysatellites: Implications for ocean-surfaceinteractionEuropa and Ganymede, Galilean satellites of Jupiter, exhibitgeologic activity in their outer H O ice shells that might conveymaterial from water oceans within the satellites to their surfaces.Imagery from the Voyager and Galileo spacecraft reveal surfacesrich with tectonic deformation, including dilational bands onEuropa and groove lanes on Ganymede. These features aregenerally attributed to the extension of a brittle ice lithosphereoverlaying a possibly convecting ice asthenosphere. To exploreband formation and interaction with interior oceans, we employfully visco-elasto-plastic 2-D models of faulting and convectionwith complex, realistic pure ice rheologies. In these models,material entering from below is tracked and considered to be“fossilized ocean,” ocean material that has frozen into the ice shelland evolves through geologic time. We track the volume fractionof fossil ocean material in the ice shell as a function of depth, andthe exposure of both fresh ice and fossil ocean material at the iceshell surface. To explore the range in extensional terrains, we varyice shell thickness, fault localization, melting-temperature iceviscosity, and the presence of pre-existing weaknesses.Mechanisms which act to weaken the ice shell and thin thelithosphere (e.g. vigorous convection, thinner shells, pre-existingweaknesses) tend to plastically yield to form smooth bands athigh strains, and are more likely to incorporate fossil oceanmaterial in the ice shell and expose it at the surface. In contrast,lithosphere strengthened by rapid fault annealing or increasedviscosity, for example, exhibits large-scale tectonic rifting at lowstrains superimposed over pre-existing terrains, and inhibits theincorporation and delivery of fossil ocean material to the surface.Thus, our results identify a spectrum of extensional terrainformation mechanisms as linked to lithospheric strength, ratherthan specific mechanisms that are unique to each type of band,and discuss where in this spectrum ocean material incorporatedat the bottom of the ice shell may be exposed on the satellitesurface.

Author(s): Samuel M Howell , Robert T. PappalardoInstitution(s): 1. Jet Propulsion Laboratory

215.02 – Topographic and Other Influences onPluto's Volatile IcesPluto’s surface is known to consist of various volatile ices, mostlyN2, CH4, and CO, which sublimate and condense on varyingtimescales, generally moving from points of high insolation tothose of low insolation. The New Horizons Pluto encounter dataprovide multiple lenses through which to view Pluto’s detailedsurface topography and composition and to investigate thedistribution of volatiles on its surface, including albedo andelevation maps from the imaging instruments and compositionmaps from the LEISA spectral imager. The volatile surface ice isexpected to be generally isothermal, due to the fact that theirvapor pressures are in equilibrium with the atmosphere.

Although secular topographic transport mechanisms suggest thatpoints at low elevation should slowly fill with volatile ices(Trafton 2015 DPS abstract, Bertrand and Forget 2017), there arecounter-examples of this across the surface, implying that energydiscrepancies caused by insolation differences, albedo variations,local slopes, and other effects may take precedence at shortertimescales. Using data from the 2015 New Horizons flyby, wepresent our results of this investigation into the effects ofvariations in insolation, albedo, and topography on the presenceof the different volatile ices across the surface of Pluto.

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Author(s): Briley Lynn Lewis , John Stansberry , WilliamM. Grundy , Bernard Schmitt , Silvia Protopapa , Laurence M.Trafton , Bryan J Holler , William B. McKinnon , Paul M.Schenk , S. Alan Stern , Leslie Young , Harold A Weaver ,Catherine Olkin , Kimberly EnnicoInstitution(s): 1. Columbia University, 2. Johns HopkinsUniversity Applied Physics Laboratory, 3. Lowell Observatory,4. Lunar and Planetary Institute, 5. NASA Ames ResearchCenter, 6. Southwest Research Institute, 7. Space TelescopeScience Insitute, 8. The University of Texas at Austin, 9.Université Grenoble Alpes, 10. University of Maryland, 11.Washington UniversityContributing team(s): The New Horizons Science Team

215.03 – Predicted Antenna TemperaturesMeasured by REX/New Horizons During ThePluto’s Flyby Probing the sub-surface in MicrowaveThe Pluto dwarf planet was observed in details in July 2015 by theNew Horizons spacecraft (NASA) during a close-targeted flybywhich reavealed surprising and fascinating landscapes with avariety of albedo and chemical composition over the surface.During the flyby, the REX microwave instrument was activated inorder to measure the antenna temperature while the beamcrossed Pluto’s surface. In particular, 3 scans were performed, thefirst two during few tens of seconds when both the day and nightside of Pluto were observed, including the South pole ; and thelast one during an occultation with Earth. We present herepredited antenna temperatures considering the known andassumed variations of thermal and electrical properties of thePluto’s sub-surface..

Each scan allow to observe thermal radiation at 4.2 cmwavelength of the surface and subsurface of Pluto, at differentlocations (latitudes / longitudes). Using a seasonnal thermalmodel that considers the measured Bond albedo and type of ice,we have modeled the Brightness temperatures that weremeasured by REX, for different amount of porosity (or thermalinertia). This modeling uses a seasonally-forced thermal modeland an emissivity model in the case of circular polarizedobservations. An antenna temperature if then retrieved assuminga beam pattern for REX. We present here how the antennatemperatures vary with the porosity of the ices obseved.

Author(s): Cedric Leyrat , Alice Le Gall , Ralph Lorenz ,Shadi BoomiInstitution(s): 1. JHU/APL, 2. LATMOS, 3. Observatoire deParis

215.04 – Observational Limits for Rings and Debrisat Pluto from New HorizonsNASA's New Horizons missions flew past Pluto on July 14, 2015.New Horizons conducted an extensive search for orbital materialat Pluto, using deep imaging at backscatter and forward-scatter,direct in situ dust detector measurements, and stellaroccultations. We searched the entire region from the surface ofPluto outward to the Pluto-Charon Hill radius (6.4 x 10 km =100 times Hydra's orbital radius), using the spacecraft's LORRIand MVIC cameras.

No material was found to a normal I/F limit of 2 x 10 for 1500km-wide rings, and 7 x 10 for 12,000 km-wide rings. Ourresults are consistent with dynamical studies that show thelifetime of dust in the Pluto system is short, with the lossdominated by solar radiation pressure and gravitationalperturbations.

Author(s): Henry B. Throop , Tod R. Lauer , Mark RShowalter , Harold A Weaver , S. Alan Stern , John R. Spencer ,Marc W. Buie , Douglas P. Hamilton , Simon Bernard Porter ,Anne J. Verbiscer , Leslie Young , Catherine Olkin , KimberlyEnnicoInstitution(s): 1. JHU-APL, 2. NOAO, 3. PSI, 4. SETI, 5. SwRI,6. UMD, 7. UVAContributing team(s): New Horizons Science Team

215.06 – Global Correlation and Non-Correlationof Topography with Color and Reflectance on PlutoA key objective of the New Horizons mission at Pluto in July 2015was completion of global maps of surface brightness and colorpatterns (covering 78% of surface) and topography (covering~42%) of Pluto and its large moon Charon. The first calibratedand registered versions of these maps have now been completedfor posting in the PDS this fall (with a peer-reviewed report onthese products to be submitted). Rich in detail, investigation intothe roles of local topography and insolation are ongoing (e.g.,Lewis et al., 2017). Here we focus on the data sets and linksbetween elevation and global color and brightness patterns andthe global mapping revealed by them. In the “north,” yellowishdeposits correlate with non-depressed portions of an eroded polartopographic dome ~600 km wide & 2-3 km high (e.g., Young etal., 2017). The broad dark band along the equator formingCthulhu Macula to the west of Sputnik Planitia is topographicallyindistinguishable from the vast smooth lightly cratered plains tothe north, indicating that latitude is the primary control, nottopography. The curious lack of dark material along theequatorial band east of Sputnik Planitia may be partly due totopography of Eastern Tombaugh Regio, which is ~500 m aboveeroded plains the north and Cthulhu Macula itself. To the south ofCthulhu Macula, plains are slightly brighter, which correlateswith a modest rise in topography of <1 km. To the southeast ofCthulhu Macula, however, an abrupt increase in reflectancecorrelates with the edge of elevated plateau that rises 2-3 kmabove the plains. The areas with the strongest signature in theCH4-band are associated with bladed terrain, the higheststanding geologic unit in absolute elevation. Similar coloredamoeboid-shaped units are evident along the equator in the low-resolution mapping areas, indicating their probable occurrenceelsewhere. Thus, while many of Pluto’s major color and albedofeatures correlate well with topography and are thus controlled byit, some (especially Cthulhu Macula) are not. Latitude controlssome of the global patterns, but geology may be a more importantdriver.

Author(s): Paul M. Schenk , Ross A. Beyer , Jeffrey M.Moore , Leslie Young , Kimberly Ennico , Catherine Olkin ,Harold A Weaver , S. Alan SternInstitution(s): 1. JHU Applied Physics Lab, 2. Lunar andPlanetary Inst., 3. NASA Ames Res. Ctr., 4. Southwest Res. Inst.Contributing team(s): New Horizons Geology and GeophysicsTeam

215.07 – Radio Thermal Emission from Pluto andCharon during the New Horizons Encounter As part of the New Horizons Radio-Science Experiment REX,radio thermal emission from Pluto and Charon (wavelength: 4.2cm) was observed during the encounter on 14 July 2015. Theprimary REX measurement, a determination of the atmosphericheight profile from the surface up to about 100 km, wasconducted during an uplink radio occultation at both ingress andegress (Hinson et al., Icarus 290, 96-111, 2017). During theinterval between ingress and egress, when the Earth and the REXuplink signals were occulted by the Pluto disk, the spacecraftantenna continued to point toward Earth and thus scanneddiametrically across the Pluto nightside. The average diameter ofthe HGA 3 dB beam was ≈1100 km at the surface during thisopportunity, thereby providing crudely resolved measurements ofthe radio brightness temperature across Pluto. The bestresolution for the REX radiometry observations occurred shortlyafter closest approach, when the HGA was scanned twice acrossPluto. These observations will be reported elsewhere (Linscott et

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al., Icarus, submitted, 2017). In addition to the resolvedobservations, full disk brightness temperature measurements ofboth bodies were performed during the approach (dayside) anddeparture (nightside) phases of the encounter. We present theresults of these observations and provide a preliminaryinterpretation of the measured brightness temperatures.

Author(s): Michael Bird , Ivan Linscott , David Hinson , G.L. Tyler , Darrell F. StrobelInstitution(s): 1. Carl Sagan Center, SETI Institute, 2. JohnsHopkins University, 3. Stanford Univ., 4. University of BonnContributing team(s): The New Horizons Science Team

216.01 – Astrometry of the Orcus/Vanthoccultation on UT 7 March 2017On UT 7 March 2017, Orcus was predicted to occult a star withm=14.3. Observations were made at five observatories: the 0.6-mAstronomical Telescope of the University of Stuttgart (ATUS) atSierra Remote Observatories (SRO), California; Las CumbresObservatory’s 1-m telescope (ELP) at McDonald Observatory,Fort Davis, Texas; NASA’s 3-m InfraRed Telescope Facility(IRTF) on Mauna Kea, Hawaii; the 4.1-m Southern AstrophysicalResearch telescope (SOAR) on Cerro Pachón, Chile; and the 0.6-m Southeastern Association for Research in Astronomy telescope(SARA-CT) at Cerro Tololo, Chile. While observations at all siteswere successful, only two—ELP and IRTF—observed solid-bodyoccultation signatures. We will discuss the various predictions forthis event and the reasons for the differences among them,including an offset of 130 mas for the star position from theposition in the Gaia catalog. The sum of the positive and negativedetections place constraints on the geometry of the Orcus/Vanthsystem, and we present our astrometric results for the geometricsolution for this occultation. The implications of the light curveanalyses are presented by Sickafoose et al., this conference.

Author(s): Amanda S. Bosh , Carlos Zuluaga , StephenLevine , Amanda A. Sickafoose , Anja Genade , KarstenSchindler , Tim Lister , Michael J. PersonInstitution(s): 1. Deustches SOFIA Institut, UniversitatStuttgart, 2. Las Cumbres Observatory, 3. Lowell Observatory,4. MIT, 5. South African Astronomical Observatory

216.02 – A 2017 stellar occultation by Orcus/Vanth(90482) Orcus is a large trans-Neptunian object (TNO) ofdiameter ~900 km, located in the 3:2 orbital resonance withNeptune. This plutino has a satellite, Vanth, approximately 280km in diameter. Vanth orbits roughly 9000 km from Orcus in a~9.5-day period. This system is particularly interesting, as Orcusfalls between the small, spectrally-bland TNOs and the largeTNOs having spectra rich in volatile features, while Vanth mighthave resulted from either collision or capture.

A stellar occultation by Orcus was predicted to occur on 07 March2017. Observations were made from five sites: the 0.6-mAstronomical Telescope of the University of Stuttgart (ATUS) atSierra Remote Observatories (SRO), California; Las CumbresObservatory’s 1-m telescope (ELP) at McDonald Observatory,Fort Davis, Texas; NASA’s 3-m InfraRed Telescope Facility(IRTF) on Mauna Kea, Hawaii; the 4.1-m Southern AstrophysicalResearch telescope (SOAR) on Cerro Pachón, Chile; and the 0.6-m Southeastern Association for Research in Astronomy telescope(SARA-CT) at Cerro Tololo, Chile. High-speed, visible-wavelengthimages were taken at all sites, in addition to simultaneous K-bandimages at the IRTF. A solid-body occultation was observed atboth ELP and the IRTF. Offset midtimes and incompatible lightratios suggest that two different stars were occulted by twodifferent bodies, likely Orcus and Vanth. See Bosh et al. thisconference for details of the astrometry for the event. Here, wepresent results from the observations, including light curves, sizeand albedo estimates, and upper limits on a possible atmosphere.

Author(s): Amanda A. Sickafoose , Amanda S. Bosh ,Stephen Levine , Carlos A. Zuluaga , Anja Genade , KarstenSchindler , Tim Lister , Michael J. PersonInstitution(s): 1. Deutsches SOFIA Institut, 2. Las CumbresObservatory, 3. Lowell Obs., 4. MIT, 5. SAAO

216.03 – Predictions of stellar occultations byTNOs/Centaurs using GaiaStellar occultations are the unique technique from the ground toaccess physical parameters of the distant solar system objects,such as the measure of the size and the shape at kilometric level,the detection of tenuous atmospheres (few nanobars), and theinvestigation of close vicinity (satellites, rings, jets). Predictions of stellar occultations require accurate positions ofthe star and the object. The Gaia DR1 catalog now allows to get stellar position to themilliarcsecond (mas) level. The main uncertainty in theprediction remains in the position of the object (tens to hundredsof mas). Now, we take advantage of the NIMA method for the orbitdetermination that uses the most recent observations reduced bythe Gaia DR1 catalog and the astrometric positions derived fromprevious positive occultations. Up to now, we have detected nearly 50 positive occultations forabout 20 objects that provide astrometric positions of the objectat the time of the occultation. The uncertainty of these positionsonly depends on the uncertainty on the position of the occultedstars, which is a few mas with the Gaia DR1 catalog. The mainlimitation is now on the proper motion of the star which is onlygiven for bright stars in the Tycho-Gaia Astrometric Solution.This limitation will be solved with the publicationof the Gaia DR2expected on April 2018 giving proper motions and parallaxes forthe Gaia stars. Until this date, we use hybrid stellar catalogs(UCAC5, HSOY) that provide proper motions derived from GaiaDR1 and another stellar catalog. Recently, the Gaia team presented a release of three preliminaryGaia DR2 stellar positions involved in the occultations byChariklo (22 June and 23 July 2017) and by Triton (5 October2017). Taking the case of Chariklo as an illustration, we will present acomparison between the proper motions of DR2 and the othercatalogs and we will show how the Gaia DR2 will lead to a maslevel precision in the orbit and in the prediction of stellaroccultations. **Part of the research leading to these results has receivedfunding from the European Research Council under the European Community’s H2020 (2014-2020/ ERC GrantAgreement n 669416 ”LUCKY STAR”).

Author(s): Josselin Desmars , Julio Camargo , DianeBerard , Bruno Sicardy , Rodrigo Leiva , Roberto Vieira-Martins , Felipe Braga-Ribas , Marcelo Assafin , Gustavo RossiInstitution(s): 1. Observatoire de Paris, 2. ObservatórioNacional/MCTIC, 3. Valongo ObservatoryContributing team(s): Chariklo occultations Team, Rio Group,Lucky Star Occultation Team, Granada Occultation Team

216.05 – Search for signatures of extendedemission around dwarf planets on Hubble SpaceTelescope archival imagesRecent discoveries of rings around the Centaurs Chariklo andChiron suggest that extended features may be present aroundseveral bodies in the outer Solar System, and maybe also arounddwarf planets. The spatial extension of these features makes theidentification possible with the Hubble Space Telescope (HST),however the relative faintness of the rings makes the detectionchallenging via direct imaging. We developed a method that considers simulated HST pointspread functions (PSFs) and those of calibration stars. Our aim is

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that by comparing these PSFs to that of the target, we identifydeviations that can be explained with the existence of a ring-likefeature.

We applied this method on HST WFPC2 and WFC3 archivalimages of several dwarf planets and here we report on the resultof our investigation.

Author(s): Gabor Marton , Csaba Kiss , Anikó Farkas-Takács , Bernadett IgnáczInstitution(s): 1. Konkoly Observatory

216.06 – Light Curve observations of the BinaryKuiper Belt Object Manwe-ThorondorThe binary Kuiper Belt Object (385446) Manwe-Thorondor (aka2003 QW111) is intriguing for several reasons. Not only areManwe and Thorondor currently undergoing mutual events,whereby the two ~100-km bodies alternately eclipse and occulteach other as seen from Earth [1], but the observed rotationalvariation implies a rotation for Thorondor that is eithersynchronous with Manwe ( a period of 11.79 h), or else muchlonger than 10 days [2]. Here we report new light curveobservations using the 8.1-m Gemini South telescope at the timeof a predicted mutual event on 2017 July 22-23. Combining thesedata with our previous observations with the 4.1m SOARtelescope at the time of an earlier mutual event (2016 Aug 25-26),we put precise constraints on the independent rotation states ofManwe and Thorondor.

[1] Grundy, W. et al. 2012, Icarus, 220, 74 [2] Rabinowitz, D. et al. 2016, AAS DPS meeting #48, astractid.120.10

Author(s): David L. Rabinowitz , Susan Benecchi , WilliamM. Grundy , Audrey Thirouin , Anne J. VerbiscerInstitution(s): 1. Lowell Observatory, 2. Planetary ScienceInstitute, 3. University of Virginia, 4. Yale Univ.

216.07 – The thermal emission of Centaurs andTrans-Neptunian objects at submm wavelengthsfrom ALMA observationsWe report on ALMA 233 GHz (1.29 mm) measurements of fourCentaurs (2002 GZ , Bienor, Chiron, Chariklo) and two TNOs(Huya, Makemake). The thermal fluxes are combined withprevious mid/far infrared fluxes, mostly from Spitzer andHerschel, in order to derive their relative emissivity at mmwavelengths. using NEATM and thermophysical models. Wereassess earlier thermal measurements of these and other objects,exploring in particular effects due to shape and varying apparentpole orientation, and show that these effects can be key forreconciling previous diameter determinations and correctlyestimating spectral emissivities. We also evalute the possiblecontribution to thermal emission of established (Chariklo) orclaimed (Chiron) systems. We find that for Chariklo, the rings donot impact the diameter determinations by more than 5 %; forChiron, invoking a ring system does not help in improving theconsistency between the numerous past size measurements.Combining our results with those of Brown and Butler (2017) onfour other TNOs, we find that all objects except Makemake haverelative radio emissivities significantly below unity. Although theemissivity values show diversity, we do not find any significanttrend with physical parameters such as diameter, albedo, color,beaming factor..., but suggest that the emissivity could becorrelated with grain size. The mean relative radio emissivity isfound to be 0.70+/-0.13, a value that we recommend for theanalysis of further mm/submm data.

Author(s): Emmanuel Lellouch , Raphael Moreno , ThomasMüller , Sonia Fornasier , Pablo Santos-Sanz , Arielle Moullet ,Mark A. Gurwell , John Stansberry , Rodrigo Leiva , BrunoSicardy , Bryan J. Butler , Jeremie boissierInstitution(s): 1. CfA, 2. IAA, 3. IRAM, 4. MPIeP, 5. NRAO, 6.NRAO, 7. Observatoire de Paris, 8. STScI

216.08 – New Solid-Phase IR Spectra of Solar-System Molecules: Methanol, Ethanol, andMethanethiol The presence and abundances of organic molecules inextraterrestrial environments, such as on TNOs, can bedetermined with infrared (IR) spectroscopy, but significantchallenges exist. Reference IR spectra for organics under relevantconditions are vital for such work, yet for many compounds suchdata either are lacking or fragmentary. In this presentation wedescribe new laboratory results for methanol (CH OH), thesimplest alcohol, which has been reported to exist in planetaryand interstellar ices. Our new results include near- and mid-IRspectra, band strengths, and optical constants at various icetemperatures. Moreover, the influence of H O-ice is examined. Inaddition to CH OH, we also have new results for the relatedcometary molecules CH SH and CH CH OH. Although IRspectra of such molecules have been reported by many groupsover the past 60 years, our work appears to be the first to coverdensities, refractive indices, band strengths and optical constantsof both the amorphous and crystalline phases. Our results arecompared to earlier work, the influence of literature assumptionsis explored, and possible revisions to the literature are described.Support from the following is acknowledged: (a) NASA-SSERVI'sDREAM2 program, (b) the NASA Astrobiology Institute'sGoddard Center for Astrobiology, and (c) a NASA-APRA award.

Author(s): Reggie L. Hudson , Perry A. Gerakines , Robert FFerranteInstitution(s): 1. NASA Goddard Space Flight Center, 2. USNaval Academy

216.09 – Orbital Clustering in Trans-NeptunianObjectsWe have conducted a clustering analysis of the orbits of extremetrans-Neptunian objects (TNOs). We report the results of this clustering analysis and discuss theirimplications for the orbital alignment of the putative Planet-9hypothesized to sculpt the orbits of the extreme TNOs.

Author(s): Matthew Payne , Matthew J. Holman , SamHaddenInstitution(s): 1. Harvard-Smithsonian CfA

216.11 – Dynamics of a Possible Collisional Familyof Extreme TNOsThe Dark Energy Survey has been highly successful in discoveringouter Solar System objects. In this presentation, we discuss thedynamics of three extreme TNOs, two of which were found by theDES. The similarity of their orbits leads us to consider thepossibility that these three objects originated from a collisionevent. In addition, as these TNOs appear to be clustered inlongitude of perihelion, we analyze their dynamics in the contextof the Planet Nine hypothesis, particularly since they reside in the150 AU < a < 250 AU transition region identified by Batygin andBrown (2016). We explore the diffusion and chaotic nature oftheir behavior both with and without the presence of Planet Nine,and evaluate the likelihood that these objects originated from acollision event.

Author(s): Tali Khain , Juliette Becker , Fred C. Adams ,David W. GerdesInstitution(s): 1. University of Michigan Department ofAstronomy, 2. University of Michigan Physics Department

216.12 – OSSOS: constraints on resonant trans-Neptunian populations from the full survey sampleThe Outer Solar System Origins Survey (OSSOS) has discoveredmore than 300 objects in mean motion resonances with Neptune,including more than 100 objects in Neptune’s 3:2 resonance. Thisquadruples the available characterized sample of resonant trans-Neptunian objects. This sample can be used to test models of thecurrent populations of these resonances and the distributions ofobjects within them, which will provide valuable constraints onthe dynamical history of Neptune. We will report on the

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distribution of objects within the 3:2 resonant population andprovide updated constraints on their H magnitude andeccentricity distribution. We will provide an updated estimate ofthe intrinsic population ratios between Neptune’s resonancesbased on the full OSSOS sample, highlight interesting constraintsfor individual resonant populations, and report new discoveries inresonances not previously known to be occupied.

Author(s): Kathryn Volk , Ruth Murray-Clay , BrettGladman , Ying-Tung Chen , Hsing Wen Lin , Rebekah IleneDawson , Samantha Lawler , Wing-Huen Ip , SarahGreenstreet , Patryk S. Lykawka , Mike Alexandersen , MicheleT Bannister , Stephen Gwyn , J. J. Kavelaars , Jean-Marc PetitInstitution(s): 1. Academia Sinica, 2. CNRS/Observatoire DeBesançon, 3. Kinki University, 4. Las Cumbres ObservatoryGlobal Telescope, 5. National Central University, 6. NationalResearch Council of Canada, 7. Pennsylvania State University,8. Queen's University Belfast, 9. University of Arizona, 10.University of British Columbia, 11. University of CaliforniaSanta Cruz

216.13 – Chariklo vs Chiron: the stability of therings due to planetary close encountersThe surprising discovery of a two well defined rings around theCentaur Chariklo was the first finding of such structures around asmall body (Braga Ribas et al., 2014). Since it is known that thecentaurs have a short lifetime (up to ten million years) and theyexperience a large number of encounters with the giant planets,one raises the question whether the rings would survive along theorbital evolution of Chariklo. In a previous work we analyzedthrough numerical simulations the effects of the close encounterswith the giant planets experienced by an ensemble of 729Chariklo-like objects (Araujo, Sfair & Winter, 2016). Even whenconsidering the most extreme encounters, the most likely result(>90%) is the survival of the ring system without any significantorbital change. Here we intend to broaden our analysis to 2060Chiron, another Centaur with a presumed ring system (Ortiz etal., 2015). Applying the same method of Araujo, Sfair & Winter(2016), initially we recorded the encounters with the giant planetsperformed by the clones of Chiron. We first notice Chiron'slifetime is shorter, and the number of encounters it experienced issignificantly larger than by Chariklo. As a consequence, the ringsof Chiron would be more susceptible to be disrupted by the closeapproaches with the giant planets. We attribute this dichotomy tothe difference of orbital and physical parameters of the twocentaurs.

Author(s): Rafael Sfair , Rosana Araujo , Othon CaboWinterInstitution(s): 1. UNESP - FEG

216.14 – Status of the Transneptunian AutomatedOccultation Survey (TAOS II)The Transneptunian Automated Occultation Survey (TAOS II)will aim to detect occultations of stars by small (~1 km diameter)objects in the Kuiper Belt and beyond. Such events are very rare(<0.001 events per star per year) and short in duration (~200ms), so many stars must be monitored at a high readout cadence.TAOS II will operate three 1.3 meter telescopes at theObservatorio Astronómico Nacional at San Pedro Mártir in BajaCalifornia, México. With a 2.3 square degree field of view and ahigh speed camera comprising CMOS imagers, the survey willmonitor 10,000 stars simultaneously with all three telescopes at areadout cadence of 20 Hz. Construction of the site began in thefall of 2013 and was completed this summer. Telescopeinstallation began in August 2017. This poster will provide anupdate on the status of the survey development and the scheduleleading to the beginning of survey operations.

Author(s): Matthew Lehner , Shiang-Yu Wang , MauricioReyes-Ruiz , Charles Alcock , Joel Castro Chacón , Wen-PingChen , You-Hua Chu , Kem H. Cook , Liliana Figueroa , John C.Geary , Benjamin Hernandez , Chung-Kai Huang , TimothyNorton , Andrew Szentgyorgyi , Wei-Ling Yen , Zhi-Wei ZhangInstitution(s): 1. Academia Sinica Institute of Astronomy andAstrophysics, 2. Harvard Smithsonian Center for Astrophysics,3. Instituto de Astronomía, Universidad Nacional Autónoma deMéxico, 4. National Central University

216.15 – Parameters for binary TNOs which couldbe detected by TAOS-IIThe main goal of the TAOS-II project is to characterize thepopulation of small TNOs by means of detecting serendipitousstellar occultations. The result of an occultation event is aparticular feature in the observed light curves resulting from thesampling of the diffraction profile. This diffraction profilecontains information about the shape of the occulting object,which can, in principle, also be used to determine if it is amember of a binary system. The combination of physicalparameters for binary objects and the capabilities of TAOS-IIconstrain the properties of the objects that can be detected. Inthis work we discuss under what conditions and physicalparameters, a binary object can be detected by TAOS-II. In orderto detect a binary TNO, the following conditions must be met: infirst place, the size of the TNO must be big enough to bediscriminated in shape and small enough to produce a diffractionpattern that fits into the reading area for just one backgroundstar. Secondly, the combination of object size and distance to theSun have to be such that, diffraction and silhouette contribute tothe light curve. The size of a binary object, in terms ofdetectability, depends on the mass of the system, angular speedand alignment in the moment of detection. Considering thesephysical parameters and detectability conditions we calculatedthe corresponding diffraction profiles and compared them withsingle object profiles. The methodology includes the computationof 2D diffraction patterns by solving the diffraction integral, forpossible binary TNOs.

Author(s): Joel Castro Chacón , Mauricio Reyes-Ruiz ,Joannes Bosco Hernández-Águila , Matthew Lehner , BenjamínHernández , Edilberto Sanchez , J.S. Silva , Teresa Garcia-Díaz , Charles Alcock , Shiang-Yu Wang , You-Hua Chu , Wen-Ping Chen , Fernando Alvarez , Liliana Figueroa , John C.Geary , Chung-Kai Huang , Kem H. Cook , Timothy Norton ,Andrew Szentgyorgyi , Wei-Ling Yen , Zhi-Wei ZhangInstitution(s): 1. CONACYT - Instituto de Astronomía,Universidad Nacional Autónoma de México, 2. Harvard-Smithsonian Center for Astrophysics, 3. Institute for Astronomyand Astrophysics, Academia Sinica., 4. Institute of Astronomy,National Central University, 5. Instituto de Astronomía,Universidad Nacional Autónoma de MéxicoContributing team(s): TAOS-II

216.16 – Analysis of Potential Radical Chemistry onKuiper Belt ObjectsKuiper Belt Objects (KBOs) are of high interest following the NewHorizons encounter with the Pluto system and the extendedmission to 2014MU69. We aimed to clarify questions raisedconcerning the possible presence of organic radicals formed fromphotolysis on the surface of KBOs and other Trans-NeptunianObjects, and obtain laboratory spectra of these radicals forcomparison to remote sensing data. We explored thephotochemical generation of methyl radical from matrix-isolatedCH I in an attempt to create sufficient amounts of the methylradical to obtain spectra in the near infrared. Both Ar and Nmatrices were studied, as well as varying guest:matrix ratios.Hydrogen lamp irradiation was found to be more effective thanmercury lamp irradiation. The irradiation time was a significantfactor when we switched matrices: methyl radical depletedrapidly in the N matrix with prolonged irradiation (~10 hours)whereas it survived for over 48 hours in some experiments withthe Ar matrix. Reaction of the methyl radical with the N matrixto form HCN was observed. Future experiments will focus on

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alternate methods of radical generation in order to increase theyield of trapped radical.

Author(s): Maya Danielle Yanez , Robert Hodyss , MorganCable , Paul JohnsonInstitution(s): 1. NASA Jet Propulsion Laboratory, CaliforniaInstitute of Technology, 2. University of Colorado Boulder

216.17 – Radiolysis by-products on the surface ofKuiper Belt Object (20000) VarunaWe present the results of an investigation into the presence ofradiolysis by-products on the surface of the intermediate-sizedKuiper Belt Object (KBO) (20000) Varuna. Interaction ofextreme-UV photons and cosmic rays with volatile methane(CH4) ice results in the formation of other hydrocarbons such asethane (C2H6), acetylene (C2H2), and ethylene (C2H4). Ethaneis the most common by-product, and all by-products are non-volatile at Kuiper Belt temperatures. Near-infrared spectra ofVaruna were obtained with the SpeX instrument in Prism mode(0.7-2.52 microns, R=100) at NASA’s Infrared Telescope Facility(IRTF) on the nights of February 20-23, 2017. A handful ofabsorption features in the spectrum of Varuna between 2.2 and2.5 μm are not consistent with absorption from the non-volatilespecies H2O and CH3OH (methanol). The features are alsoinconsistent with absorption due to CH4 ice, which was presentedas a possible component of Varuna’s surface by Lorenzi et al.(2014). Preliminary analysis suggests these features areconsistent with absorption from ethane and ethylene (Hudson etal., 2014). Volatile retention theories (e.g., Schaller and Brown,2007) favor the retention of ethane and ethylene and the loss ofmethane on Varuna due its diameter (∼700 km; Lellouch et al.,2013) and estimated equilibrium temperature (∼41 K). Portionsof this work were funded by NASA Solar Systems Observationsgrant NNX17AG16G.

Author(s): Bryan J Holler , Leslie Young , Silvia Protopapa ,Schelte J. BusInstitution(s): 1. Southwest Research Institute, 2. SpaceTelescope Science Institute, 3. University of Hawaii, 4.University of Maryland

216.18 – Absolute colors and phase coefficients ofTrans-Neptunian objects: H − H colors.We present results of our photometric follow up of Trans-Neptunian objects (TNOs). New data for 35 objects, together withpreviously data presented in Alvarez-Candal et al. 2016, as well asdata from literature allow us to obtain absolute magnitudes andabsolute coefficients H (β ) for 113 TNOs and H (β ) for 117TNOs from which we obtained absolute colors H − H andrelative phase coefficients Δβ, for 106 objects. We explored associations between H − H and Δβ vs. orbitaland physical parameters of TNOs, such associations were testedby Spearman’s coefficient r . The correlations we found betweenH − H and orbital parameters semimayor axis a, eccentricity e,and inclination i, reflect observational biases: first, against fartherfainter objects; second, against eccentric and high-inclinationorbits. We followed Brown criteria (Brown 2012), and separated into twogroups: large and small using H = 4.5 instead of D=500 km. Wedetected a gap at H = 4.5 which not reported before to the bestof our knowledge. We found a strong anticorrelation between H − H and Δβ, withr = -0.8273, which indicates that redder objects have steeperphase curves in the R filter than in the V filter, while the oppositeis true for bluer objects. The anticorrelation holds if we considerdifferent bins in semi-major axis and separate between large H< 4.5 mag (D > 500 km) and small objects H > 4.5 mag (D <500 km). Therefore, we conclude it is intrinsic to the TNO (andassociated) populations. As many different surfaces types, sizes,and dynamical evolutions of TNOs we considered in our sample,we cannot assure that we are seeing an evolutionary effect, butprobably something related to the porosity and compation of thesurfaces. Further studies are granted.

Author(s): Carmen Ayala-Loera , Alvaro Alvarez-Candal ,Jose Luis Ortiz , Rene Duffard , Estela Fernández-Valenzuela ,Pablo Santos-Sanz , Nicolas MoralesInstitution(s): 1. Instituto de Astrofísica de Andalucía, 2.Observátorio Nacional

217.01 – PlanetCARMA: A New Framework forStudying the Microphysics of PlanetaryAtmospheres The Community Aerosol and Radiation Model for Atmospheres(CARMA) has been updated to apply to atmospheres of the SolarSystem outside of Earth. CARMA, as its name suggests, is acoupled aerosol microphysics and radiative transfer model andincludes the processes of nucleation, condensation, evaporation,coagulation, and vertical transport. Previous model versions havebeen applied (by this and other groups) to the atmospheres ofSolar System bodies and extrasolar planets. The primaryadvantage to our version, which we now call PlanetCARMA, isthat the core physics routines each reside in their own self-contained modules and can be turned on/off as desired while aseparate planet module supplies all the necessary parameters toapply the model run to a particular planet (or planetary body). Soa single codebase is used for all planetary studies. Our CARMAmodel is also now written in Fortran 90 modular format.Examples of PlanetCARMA results will be presented from studiesof the atmospheres of Titan, Saturn, Jupiter, and Pluto.

Author(s): Erika L. BarthInstitution(s): 1. Southwest Research Inst.

217.02 – Ertel Potential Vorticity versus BernoulliStreamfunction in Earth's Southern Ocean:Comparison with the Atmospheres of Earth, Mars,Jupiter and SaturnWe are working to expand the comparative planetology ofvorticity-streamfunction correlations established for theatmospheres of Earth, Mars, Jupiter and Saturn to include

Earth’s Antarctic Circumpolar Current (ACC), which is the onlyoceanic jet that encircles the planet. Interestingly, the ACC and itseddies scale like atmospheric jets and eddies on Jupiter andSaturn---the Southern Ocean is a “giant planet” with a zonal jetstream. Our input is the Southern Ocean State Estimate (SOSE;Mazloff et al 2010, J. Phys. Ocean. 40, 880-899), an optimalcombination of observations and primitive-equation model thatspans 2005-2010. Two hurdles not encountered in atmosphericwork arise from the nonlinear equation of state of ocean water:non-zero helicity, which prevents the existence of truly neutral(analogous to adiabatic) surfaces, and the lack of a geostrophicstreamfunction in general. We follow de Szoeke et al (2000, J.Phys. Ocean. 30, 2830-2852) to overcome these hurdles,regionally, by using orthobaric density as the vertical coordinate.In agreement with results for all atmospheres analyzed to date,scatter plots of Ertel potential vorticity, Q, versus Bernoullistreamfunction, B, on orthobaric density surfaces in the SouthernOcean are well correlated. The general shape of the correlation islike a hockey stick, with the “blade” corresponding to a broadhorizontal region that spans the ACC, and the “handle”corresponding to shallow water. The same linear-regression Qversus B model employed for Mars is applied to the ACC (“blade”)signal. Results include that the deeper water on the equatorwardside of the ACC is most prone to shear instability, and elsewherethe ACC is “supersonic” such that the net propagation of vorticitywaves is eastward, not the usual westward. During the 6-yearspan of the SOSE data, there is a steady drift of the correlation tolarger values at the top of the vertical profile, and to smallervalues in the middle of the profile, which correlates with the time-smoothed Southern Annular Mode, i.e. the strength of theatmospheric polar vortex, and may indicate how the bulk oceanreacts to interannual changes in the atmospheric polar vortex.

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Author(s): Timothy E. Dowling , Geoff Stanley , MaryElizabeth Bradley , David P MarshallInstitution(s): 1. Univ. of Louisville, 2. Univ. of Oxford

217.04 – Origins and Destinations: Tracking PlanetComposition through Planet FormationSimulationsThere are now several thousand confirmed exoplanets, a numberwhich far exceeds our resources to study them all in detail. Inparticular, planets around M dwarfs provide the best opportunityfor in-depth study of their atmospheres by telescopes in the nearfuture. The question of which M dwarf planets most merit follow-up resources is a pressing one, given that NASA’s TESS missionwill soon find hundreds of such planets orbiting stars brightenough for both ground and spaced-based observation. Our work aims to predict the approximate composition of planetsaround these stars through n-body simulations of the last stage ofplanet formation. With a variety of initial disk conditions, weinvestigate how the relative abundances of both refractory andvolatile compounds in the primordial planetesimals are mappedto the final planet outcomes. These predictions will serve toprovide a basis for making an educated guess about (a) whichplanets to observe with precious resources like JWST and (b) howto identify them based on dynamical clues.

Author(s): Quadry ChanceInstitution(s): 1. University of Arizona

217.05 – Gyrochronology relating star age torotational period is derived from first principlesthrough a novel time dual for thermodynamics,named lingerdynamicsGyrochronology estimates the age of a low-mass star from itsrotational period, which is found from changes in brightnesscaused by dark star spots. First revealed as an insight in(Skumanich, A. 1972, The Astrophysical Journal. 171:565) it allows astronomers to find true sun-like stars that may

harbor life in its planets (Meibom, S. et. al., Nature. 517:589–591). Here a simple expression for the age of a star isderived through a novel linger thermo theory (LTT) integratingthermodynamics with its revealed time-dual, namedlingerdynamics. This expression relates the star age to the ratio ofpast and present rotational period metrics (RPM) oflingerdynamics. LTT has been used earlier to derive a simpleexpression for the finding of the entropy of spherical-homogeneous mediums (Feria, E. H. Nov. 19, 2016, LingerThermo Theory, IEEE Int’l Conf. on Smart Cloud, 18pages, DOI 10.1109/SmartCloud.2016.57, ColombiaUniv., N.Y., N.Y. and Feria, E. H. June 7 2017, AAS340 Meeting). In LTT the lifespan of system operation τ isgiven by: τ = (2Π /3v )G M x RPM where G is the gravitationalconstant, Π is the pace of mass-energy retention in s/m units(e.g., for our current sun it is given by 5 billion ‘future’ years overits volume), and v is the perpetual radial speed about the point-mass M. Since in LTT a star is modeled as a point mass at thecenter of its spherical volume, its RPM is not the same as themeasured rotational period of an actual star. For instance, for oursun its equator rotational period is approximately 25.34 days,while in lingerdynamics it is a fraction of a day, i.e., 0.116 days,where this value is derived from the RPM expression2πr /(GM / r ) where 2πr is the circumference ofthe sun, (GM /r ) is the perpetual radial speed v for ourpoint-mass modeled sun, and r and M are the sun radiusand point-mass, respectively. However, using conservation ofangular momentum arguments it is assumed that the ratio of the‘actual past and present rotational periods’ matches that of ourtheoretical lingerdynamic’s rotational period metrics. Using thiskey enabling theoretical assumption one then sensibly arrives atgyrochronology from our first principles LTT perspective.

Author(s): Erlan H FeriaInstitution(s): 1. CUNY College of Staten Island

218.01 – An Overview of the Planetary Data SystemRoadmap Study for 2017 - 2026NASA’s Planetary Data System (PDS) is the formal archive of >1.2petabytes of data from planetary exploration, science, andresearch. Initiated in 1989 to address an overall lack of attentionto mission data documentation, access, and archiving, the PDShas since evolved into an online collection of digital data managedand served by a federation of 6 science discipline nodes and 2technical support nodes. Several ad-hoc mission-oriented datanodes also provide complex data interfaces and access for theduration of their missions.

The new PDS Roadmap Study for 2017-2026 involved 15planetary science community members who collectively prepareda report summarizing the results of an intensive examination ofthe current state of the PDS and its organization, management,practices, and data holdings(https://pds.jpl.nasa.gov/roadmap/PlanetaryDataSystemRMS17-26_20jun17.pdf). The report summarizes PDS history, itsfunctions and characteristics, and its present form; also includedare extensive references and documentary appendices. The reportrecognizes that as a complex evolving system, the PDS mustrespond to new pressures and opportunities. The report providesdetails on challenges now facing the PDS, 19 detailed findings andsuggested remediations that could be used to respond to thesefindings, and a summary of the potential future of planetary dataarchiving. These findings cover topics such as user needs andexpectations, data usability and discoverability (i.e., metadata,data access, documentation, and training), tools and file formats,use of current information technologies, and responses toincreases in data volume, variety, complexity, and number of dataproviders. In addition, the study addresses the possibility ofarchiving software, laboratory data, and physical samples. Finally,the report discusses the current structure and governance of PDSand the impact of this on how archive growth, technology, and

new developments are enabled and managed within the PDS. Thereport, with its findings, acknowledges the ongoing and expectedchallenges to be faced in the future, the need for maintaining anedge on the use of emerging technologies, and represents a guidefor evolution of the PDS for the next decade.

Author(s): Thomas H. Morgan , Ralph L. McNutt , LisaGaddis , Emily Law , Ross A. Beyer , Kate Crombie , DentonEbel , Amitahba Ghosh , Edwin J. Grayzeck , Flora Paganelli ,Anne C. Raugh , Thomas Stein , Matthew S. Tiscareno ,Renee Weber , Maria E Banks , Kathryn PowellInstitution(s): 1. American Museum of Natural History, 2.Indigo Information Services, LLC, 3. JHUAPL, 4. NASAMarshall Space Flight Center, 5. NASA/Ames, 6. NASA/GSFC, 7.NASA/JPL, 8. SETI Institute, 9. Tharsis Inc., 10. University ofMaryland, 11. USGS/Flagstaff, 12. Washington University

218.03 – A Tale of Two Archives: PDS3/PDS4Archiving and Distribution of Juno Mission DataThe Juno mission to Jupiter, which was launched on 5 August2011 and arrived at the Jovian system in July 2016, represents thelast mission to be officially archived under the PDS3 archivestandards. Modernization and availability of the newer PDS4archive standard has prompted the PDS Atmospheres Node(ATM) to provide on-the-fly migration of Juno data from PDS3 toPDS4. Data distribution under both standards presentschallenges in terms of how to present data to the end user in bothstandards, without sacrificing accessibility to the data orimpacting the active PDS3 mission pipelines tasked withdelivering the data on predetermined schedules. The PDSAtmospheres Node has leveraged its experience with prior activePDS4 missions (e.g., LADEE and MAVEN) and ongoing PDS3-to-PDS4 data migration efforts providing a seamless distribution ofJuno data in both PDS3 and PDS4. When ATM receives a datadelivery from the Juno Science Operations Center, the PDS3

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labels are validated and then fed through PDS4 migrationsoftware built at ATM. Specifically, a collection of Pythonmethods and scripts has been developed to make the migrationprocess as automatic as possible, even when working with themore complex labels used by several of the Juno instruments.This is used to create all of the PDS4 data labels at once and buildPDS4 archive bundles with minimal human effort. Resultantbundles are then validated against the PDS4 standard andreleased alongside the certified PDS3 versions of the same data.The newer design of the distribution pages provides access toboth versions of the data, utilizing some of the enhancedcapabilities of PDS4 to improve search and retrieval of Juno data.Webpages are designed with the intent of offering easy access toall documentation for Juno data as well as the data themselves inboth standards for users of all experience levels. We discuss thestructure and organization of the Juno archive and associatedwebpages as examples of joint PDS3/PDS4 data access for endusers.

Author(s): Zena Stevenson , Lynn Neakrase , Lyle Huber ,Nancy J. Chanover , Reta F. Beebe , Kathrine Sweebe , Joni J.JohnsonInstitution(s): 1. New Mexico State University

218.04 – Educational Labeling System forAtmospheres (ELSA): Python Tool Developmentfor Archiving Under the PDS4 StandardThe Research and Analysis programs within NASA’s PlanetaryScience Division now require archiving of resultant data with thePlanetary Data System (PDS) or an equivalent archive. The PDSAtmospheres Node is developing an online environment forassisting data providers with this task. The Educational LabelingSystem for Atmospheres (ELSA) is being designed withDjango/Python coding to provide an easier environment forfacilitating not only communication with the PDS node, but alsostreamlining the process of learning, developing, submitting, andreviewing archive bundles under the new PDS4 archivingstandard. Under the PDS4 standard, data are archived in bundles,collections, and basic products that form an organizationalhierarchy of interconnected labels that describe the data andrelationships between the data and its documentation. PDS4labels are implemented using Extensible Markup Language(XML), which is an international standard for managingmetadata. Potential data providers entering the ELSAenvironment can learn more about PDS4, plan and develop labeltemplates, and build their archive bundles. ELSA provides aninterface to tailor label templates aiding in the creation ofrequired internal Logical Identifiers (URN – Uniform ResourceNames) and Context References (missions, instruments, targets,facilities, etc.). The underlying structure of ELSA usesDjango/Python code that make maintaining and updating theinterface easy to do for our undergraduate/graduate students.The ELSA environment will soon provide an interface for usingthe tailored templates in a pipeline to produce entire collectionsof labeled products, essentially building the user’s archive bundle.Once the pieces of the archive bundle are assembled, ELSAprovides options for queuing the completed bundle for peerreview. The peer review process has also been streamlined foronline access and tracking to help make the archiving processwith PDS as transparent as possible. We discuss the currentstatus of ELSA and provide examples of its implementation.

Author(s): Lynn Neakrase , Danae Hornung , KathrineSweebe , Lyle Huber , Nancy J. Chanover , Zena Stevenson ,Jodi Berdis , Joni J. Johnson , Reta F. BeebeInstitution(s): 1. New Mexico State University

218.06 – Quantitative Outline-based ShapeAnalysis and Classification of PlanetaryCraterforms using Supervised Learning ModelsThe shapes of craterform morphology on planetary surfacesprovides rich information about their origins and evolution.While morphologic information provides rich visual clues togeologic processes and properties, the ability to quantitatively

communicate this information is less easily accomplished. Thisstudy examines the morphology of craterforms using thequantitative outline-based shape methods of geometricmorphometrics, commonly used in biology and paleontology. Weexamine and compare landforms on planetary surfaces usingshape, a property of morphology that is invariant to translation,rotation, and size. We quantify the shapes of paterae on Io,martian calderas, terrestrial basaltic shield calderas, terrestrialash-flow calderas, and lunar impact craters using elliptic Fourieranalysis (EFA) and the Zahn and Roskies (Z-R) shape function, ortangent angle approach to produce multivariate shapedescriptors. These shape descriptors are subjected to multivariatestatistical analysis including canonical variate analysis (CVA), amultiple-comparison variant of discriminant analysis, toinvestigate the link between craterform shape and classification.Paterae on Io are most similar in shape to terrestrial ash-flowcalderas and the shapes of terrestrial basaltic shield volcanoes aremost similar to martian calderas. The shapes of lunar impactcraters, including simple, transitional, and complex morphology,are classified with a 100% rate of success in all models. MultipleCVA models effectively predict and classify different craterformsusing shape-based identification and demonstrate significantpotential for use in the analysis of planetary surfaces.

Author(s): Thomas Joseph Slezak , Jani Radebaugh , EricChristiansenInstitution(s): 1. Brigham Young University

218.07 – Planetary Nomenclature: An Overviewand Update for 2017The task of naming planetary surface features, rings, and naturalsatellites is managed by the International Astronomical Union’s(IAU) Working Group for Planetary System Nomenclature(WGPSN). There are currently 15,361 IAU-approved surfacefeature names on 41 planetary bodies, including moons andasteroids. The members of the WGPSN and its task groups haveworked since the early 1970s to provide a clear, unambiguoussystem of planetary nomenclature that represents cultures andcountries from all regions of Earth. WGPSN members includeRita Schulz (Chair) and 9 other members representing countriesaround the globe. The participation of knowledgeable scientistsand experts in this process is vital to its success of the IAUWGPSN . Planetary nomenclature is a tool used to uniquelyidentify features on the surfaces of planets or satellites so they canbe located, described, and discussed in publications, includingpeer-review journals, maps and conference presentations.Approved names are listed in the Transactions of the IAU and onthe Gazetteer of Planetary Nomenclature website. Any namescurrently in use that are not listed the Gazetteer are not official.Planetary names must adhere to rules and conventionsestablished by the IAU WGPSN (seehttp://planetarynames.wr.usgs.gov/Page/Rules for the completelist). The gazetteer includes an online Name Request Form(http://planetarynames.wr.usgs.gov/FeatureNameRequest) thatcan be used by members of the professional science community.Name requests are first reviewed by one of six task groups(Mercury, Venus, Moon, Mars, Outer Solar System, and SmallBodies). After a task group has reviewed a proposal, it issubmitted to the WGPSN. Allow four to six weeks for the reviewand approval process. Upon WGPSN approval, names areconsidered formally approved and it is then appropriate to usethem in publications. Approved names are immediately enteredinto the database and shown on the website. Questions about thenomenclature database and the naming process can be sent toRosalyn Hayward, USGS Astrogeology Science Center, 2255N. Gemini Dr., Flagstaff, AZ 86001, or by email [email protected].

Author(s): Tenielle Gaither , Rose HaywardInstitution(s): 1. USGS Astrogeology Science CenterContributing team(s): IAU Working Group for PlanetarySystem Nomenclature

218.08 – Improved moving source photometry withTRIPPy

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Photometry of moving sources is more complicated than forstationary sources, because the sources trail their signal out overmore pixels than a point source of the same magnitude. Using acircular aperture of same size as would be appropriate for pointsources can cut out a large amount of flux if a moving sourcemoves substantially relative to the size of the aperture during theexposure, resulting in underestimated fluxes. Using a largecircular aperture can mitigate this issue at the cost of asignificantly reduced signal to noise compared to a point source,as a result of the inclusion of a larger background region withinthe aperture. Trailed Image Photometry in Python (TRIPPy) solves thisproblem by using a pill-shaped aperture: the traditional circularaperture is sliced in half perpendicular to the direction of motionand separated by a rectangle as long as the total motion of thesource during the exposure. TRIPPy can also calculate theappropriate aperture correction (which will depend both on theradius and trail length of the pill-shaped aperture), and hasfeatures for selecting good PSF stars, creating a PSF model

(convolved moffat profile + lookup table) and selecting a customsky-background area in order to ensure no other sourcescontribute to the background estimate. In this poster, we present an overview of the TRIPPy features anddemonstrate the improvements resulting from using TRIPPycompared to photometry obtained by other methods withexamples from real projects where TRIPPy has been implementedin order to obtain the best-possible photometric measurements ofSolar System objects. While TRIPPy has currently mainly beenused for Trans-Neptunian Objects, the improvement from usingthe pill-shaped aperture increases with source motion, makingTRIPPy highly relevant for asteroid and centaur photometry aswell.

Author(s): Mike Alexandersen , Wesley Cristopher FraserInstitution(s): 1. Academia Sinica, 2. Queen's UniversityBelfast

219.01 – The Near-Earth Object CameraThe Near-Earth Object Camera (NEOCam) is a NASA mission informulation designed to find, track, and provide basic physicalcharacterization of asteroids and comets that make closeapproaches to Earth. Its goal is to reduce the risk of impacts fromundetected near-Earth objects (NEOs) capable of causing globaland regional disasters. NEOCam consists of a 50 cm telescopeoperating at two channels dominated by NEO thermal emission,4.2-5.0um and 6-10um, in order to better constrain the objects'temperatures and diameters. Orbiting the Sun-Earth L1 Lagrangepoint, the mission would find hundreds of thousands of NEOsand would make significant progress toward the Congressionalobjective of discovering more than 90% of NEOs larger than 140m during its five-year lifetime. The mission uses novel2048x2048 HgCdTe detectors that extend the wavelength cutoffbeyond 10um at an operating temperature of 40K (Dorn et al.2016). Both the optical system and the detectors are cooledpassively using radiators and thermal shields to enable longmission life and to avoid the complexity of cryocoolers orcryogens. NEOCam is currently in an extended Phase A.

Author(s): Amy K. MainzerInstitution(s): 1. JPLContributing team(s): NEOCam Science Team

219.02 – Dragonfly: Exploring Titan's Surface witha New Frontiers Relocatable LanderWe proposed to the NASA New Frontiers 4 mission call a landerto assess Titan's prebiotic chemistry, evaluate its habitability, andsearch for biosignatures on its surface. Titan as an Ocean World isideal for the study of prebiotic chemical processes and thehabitability of an extraterrestrial environment due to itsabundant complex carbon-rich chemistry and because both liquidwater and liquid hydrocarbons can occur on its surface. Transientliquid water surface environments can be created by both impactsand cryovolcanic processes. In both cases, the water could mixwith surface organics to form a primordial soup. The missionwould sample both organic sediments and water ice to measuresurface composition, achieving surface mobility by using rotors totake off, fly, and land at new sites. The Dragonfly rotorcraft landercan thus convey a single capable instrument suite to multiplelocations providing the capability to explore diverse locations 10sto 100s of kilometers apart to characterize the habitability ofTitan's environment, investigate how far prebiotic chemistry hasprogressed, and search for chemical signatures indicative ofwater- and/or hydrocarbon-based life.

Author(s): Jason W. Barnes , Elizabeth P. Turtle , Melissa GTrainer , Ralph LorenzInstitution(s): 1. JHU/APL, 2. NASA Goddard Space FlightCenter, 3. University of Idaho

219.03 – neoPASCAL: A Cubesat-based approach tovalidate Mars GCMs using a network of landedsensorsBeginning in the 1990s, concepts for a network of 15-20 small(12.8 kg) landers to measure surface pressure across Mars wereproposed (Merrihew et al., 1996). Such distributed measurementswere seen as particularly valuable as they held the promise ofvalidating Mars Global Circulation Models (GCMs), for which thediurnal and seasonal variations in surface pressure may bediagnostically related to atmospheric parameters (Haberle et al.,1996). MicroMET, later renamed PASCAL, was a Discoverycontender, however, the total mass required for the 20 landersand a support orbiter presented a challenge compared to thedelivered science. In the 20 years since this concept originated, miniaturization ofspacecraft systems, sensors and components has madesubstantial progress. Several small planetary science spacecraftbased on the CubeSat design approach will launch in the next fewyears. Yet, only one meteorological station (REMS) currentlyoperates on the surface of Mars. Meanwhile, the output fromatmospheric models have become ever more critical forunderstanding key Martian geological processes including volatiletransport, identifying the extent and persistence of surface brines,understanding the sources and sinks of methane andinvestigating the past climate of Mars, to name only a few areas. As such, it is time to reconsider the PASCAL concept. We findthat modern equipment opens up payload space in the original12.8 kg entry-vehicles from 23 g to nearly 1 kg, sufficient foradding small imagers, spectrometers and other additional oralternate payloads to examine atmosphere and surface over awide geographic range of settings. If, instead, we seek theminimum solution for spacecraft mass, we find that a pressure-sensing vehicle would mass < 250 g at entry making thesespacecraft appealing secondary payloads for future Marsmissions.

Author(s): John Moores , Hugh Podmore , Regina S.K.Lee , Robert HaberleInstitution(s): 1. Ames Research Center, 2. York University

219.04 – Science Goals, Objectives, andInvestigations of the 2016 Europa Lander ScienceDefinition Team ReportIn June of 2016 NASA convened a 21-person team of scientists toestablish the science goals, objectives, investigations,measurement requirements, and model payload of a Europalander mission concept. The NASA HQ Charter goals, in priorityorder, are as follows: 1) Search for evidence of life on Europa, 2) Assess the habitabilityof Europa via in situ techniques uniquely available to a landermission, 3) Characterize surface and subsurface properties at the

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scale of the lander to support future exploration of Europa.

Within Goal 1, four Objectives were developed for seeking signs oflife. These include the need to: a) detect and characterize anyorganic indicators of past or present life, b) identify andcharacterize morphological, textural, and other indicators of life,c) detect and characterize any inorganic indicators of past orpresent life, and d) determine the provenance of Lander-sampledmaterial. Goal 2 focuses on Europa’s habitability and ensures thateven in the absence of the detection of any potentialbiosignatures, significant ocean world science is still achieved.Goal 3 ensures that the landing site region is quantitativelycharacterized in the context needed for Goals 1 and 2, and thatkey measurements about Europa’s ice shell are made to enablefuture exploration.

Critically, scientific success cannot be, and should never be,contingent on finding signs of life – such criteria would be levyingrequirements on how the universe works. Rather, scientificsuccess is defined here as achieving a suite of measurements suchthat if convincing signs of life are present on Europa’s surfacethey could be detected at levels comparable to those found inbenchmark environments on Earth, and, further, that even if nopotential biosignatures are detected, the science return of themission will significantly advance our fundamentalunderstanding of Europa’s chemistry, geology, geophysics, andhabitability.

Author(s): Kevin P. Hand , Alison Murray , James GarvinInstitution(s): 1. DRI, 2. GSFC, 3. JPLContributing team(s): and the Europa Lander ScienceDefinition Team, Project Science Team, and Project EngineeringTeam.

219.05 – Scientific Objectives of China Chang ’E4（CE-4） Lunar Far-side Exploration MissionChina has achieved great success in the recently CE-1~CE-3 lunarmissions, and in the year of 2018, China Lunar ExplorationProgram (CLEP) is going to launch the CE-4 mission. CE-4satellite is the backup satellite of CE-3, so that it also consists of aLander and a Rover. However, CE-4 is the first mission designedto detect the far side of the Moon in human lunar explorationhistory. So the biggest difference between CE-4 and CE-3 is that itwill be equipped with a relay satellite in Earth-Moon-L2 Point forEarth-Moon Communication. And the scientific payloads carriedon the Lander and Rover will also be different. It has beenannounced by the Chinese government that CE-4 mission will beequipped with some new international cooperated scientificpayloads, such as the Low Frequency Radio Detector fromHolland, Lunar Neutron and Radiation Dose Detector fromGermany, Neutral Atom Detector from Sweden, and LunarMiniature Optical Imaging Sounder from Saudi Arabia. The mainscientific objective of CE-4 is to provide scientific data for lunarfar side research, including: 1)general spatial environmentalstudy of lunar far side；2)general research on the surface,shallow layer and deep layer of lunar far side；3)detection of lowfrequency radio on lunar far side using Low Frequency RadioDetector, which would be the first time of using such frequencyband in lunar exploration history .

Author(s): Hongbo Zhang , Xingguo Zeng , Wangli ChenInstitution(s): 1. National Astronomical Observatories ofChina,Chinese Academy of Sciences

219.06 – New Frontiers Science at Venus fromOrbit plus Atmospheric Gas Sampling

Venus remains the most Earth-like body in terms of size,composition, surface age, and insulation. Venus Origins Explorer(VOX) determines how Earth’s twin diverged, and enablesbreakthroughs in our understanding of rocky planet evolutionand habitability. At the time of the Decadal Survey the ability tomap mineralogy from orbit (Helbert et al.) and present-day radartechniques to detect active deformation were not fully

appreciated. VOX leverages these methods and in-situ noblegases to answer New Frontiers science objectives: 1. Atmospheric physics/chemistry: noble gases and isotopes toconstrain atmospheric sources, escape processes, and integratedvolcanic outgassing; global search for current volcanicallyoutgassed water. 2. Past hydrological cycles: global tessera composition todetermine the role of volatiles in crustal formation. 3. Crustal physics/chemistry: global crustalmineralogy/chemistry, tectonic processes, heat flow, resolve thecatastrophic vs. equilibrium resurfacing debate, active geologicprocesses and possible crustal recycling. 4. Crustal weathering: surface-atmosphere weathering reactionsfrom redox state and the chemical equilibrium of the near-surfaceatmosphere. 5. Atmospheric properties/winds: map cloud particle modes andtheir temporal variations, and track cloud-level winds in the polarvortices. 6. Surface-atmosphere interactions: chemical reactions frommineralogy; weathering state between new, recent and olderflows; possible volcanically outgassed water. VOX’s Atmosphere Sampling Vehicle (ASV) dips into and samplesthe well-mixed atmosphere, using Venus Original ConstituentsExperiment (VOCE) to measure noble gases. VOX’s orbitercarries the Venus Emissivity Mapper (VEM) and the VenusInterferometric Synthetic Aperture Radar (VISAR), and maps thegravity field using Ka-band tracking. VOX is the logical next mission to Venus because it delivers: 1)top priority atmosphere, surface, and interior science; 2) keyglobal data for comparative planetology; 3) high-resolutiontopography, composition, and imaging to optimize future landers;4) opportunities for revolutionary discoveries with a 3-year longmission, proven implementation and 44 Tb of data.

Author(s): Suzanne Smrekar , Melinda Dyar , ScottHensley , Joern HelbertInstitution(s): 1. German Space Agency, 2. Jet PropulsionLaboratory, 3. Mount Holyoke CollegeContributing team(s): VOX Science and Engineering Teams

219.07 – Hayabusa2 NIRS3’s Investigation toCharacterize and Select Sampling and LandingSites on Asteroid (25143) RyuguFollowing the visit of the spacecraft Hayabusa to (25143) Itokawain 2005, the Japanese Space Agency (JAXA) launched a secondspacecraft, Hayabusa2, in 2014 to the near-Earth Apollo asteroid(162173) Ryugu, a C-complex asteroid. Hayabusa2 will arrive atRyugu in 2018. Near-Earth asteroids (NEAs) are importantobjects to study because of their possible role in the delivery ofwater and complex organic molecules to early Earth, and theirthreats to impact the Earth at irregular and unpredictable periodsin the future. Hayabusa2 mission will provide exceptional sciencewith a primary objective to illuminate the origin, evolution, anddistribution of volatiles and organics on the surface of Ryugu andin the Solar System. Here we present our Near InfraredSpectrometer(NIRS3)-related strategy and plan to help thescience team to characterize and select sampling and landing sitesto collect carbonaceous samples from Ryugu and bring them backto Earth in 2020. Our plan includes, (1) measuring spectra ofvarious carbonaceous chondrites and end-member hydratedsilicates under asteroid-like conditions (vacuum and elevatedtemperatures) to develop spectral parameters of minerals andchemical compounds that we expect to detect on Ryugu,particularly around 2.8 to 3.2 µm, and (2) thermally andphotometrically correcting Ryugu’s spectra to create site-specificand global maps of the mineralogical and chemical relativeabundances across Ryugu’s surface, in addition to creatingvarious albedo maps, including the geometric and bolometricBond albedo. Previous 3-µm spectroscopic studies wereconducted in ambient terrestrial environments, and hence werecontaminated by atmospheric water. In our work, however,chondrite reflectance and hydrated mineral spectra are measuredunder asteroid-like conditions to remove adsorbed water andaccurately compute the spectral parameters that will be used forRyugu’s mineralogical and chemical mapping.

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Acknowledgements We wish to thank the Japan Society for the Promotion of ScienceCore-to-Core program (International Network of PlanetarySciences) for supporting Yusuke Nakauchi. Part of this work hasbeen supported by NASA Hayabusa2 Participating Scientist grantNNX17AL02G (PI: Takir).

Author(s): Driss Takir , Charles A. Hibbitts , Lucille LeCorre , Joshua P. Emery , Kohei Kitazato , Seiji Sugita , YusukeNakauchiInstitution(s): 1. Dept. of Earth and Planetary Science, Schoolof Science, Univeristy of Tokyo, 2. JHU Applied PhysicsLaboratory, 3. Planetary Science Institute, 4. SETI Institute, 5.The University of Aizu, Research Center for AdvancedInformation Science and Technology, Ikki-machi, Aizu-Wakamatsu, 6. University of Tennessee

219.09 – High Resolution Mid-IR Observations ofthe Solar System with EXES on SOFIAThe Echelon Cross Echelle Spectrograph (EXES) is a high-resolution (R~100,000) spectrograph operating in the 4.5-28.3um region onboard NASA/DLRs SOFIA observatory. Thecombination of high-resolution spectroscopy and spectralwindows previously unavailable from the ground has made EXESa powerful and productive tool in the study of molecules in thesolar system. We highlight results from our 2016-2017 campaigns includingstudies of water loss on Venus and Mars, stringent upper limitsfor Martian Methane, mapping HCN in the clouds of Jupiter andattempting to detect water plumes reported from Jupiter's moonEuropa.

Author(s): Curtis N. DeWitt , Matthew Richter , Edward J.Montiel , Cordell Newmiller , Therese Encrenaz , Shohei Aoki ,Constantine Tsang , Abraham C. A. BoogertInstitution(s): 1. Belgian Institute for Space Aeronomy, 2.Observatoire Paris-Site de Meudon, 3. SwRI, 4. UC Davis, 5.University of Hawaii

219.10 – Acquiring Spectra of Solar System Objectswith the NIRSpec Instrument on the James WebbSpace TelescopeThe NIRSpec Instrument on the James Webb Space Telescopewill allow near-IR spectroscopy in the wavelength range between0.6 and 5.3 microns with resolving power of ~100, 1000, or 2700.We review strategies for performing spectral observations of solarsystem objects using each of NIRSpec's available observingmodes, including the integral field unit (IFU), multi-ObjectSpectroscopy (MOS), and fixed slit (FS) templates, and discusshow the choice of mode affects the limiting target brightness aswell as the detailed wavelength and spatial coverage obtained. Wealso discuss the expected pointing accuracy and target acquisitionoptions for moving targets, including the use and limitations ofthe Wide Aperture Target Acquisition (WATA) capability and ofthe pre-defined field points that will be available for use with theMOS template to enable the use of custom micro-shutter patternsincluding ones emulating very long slits.

Author(s): Charles R. Proffitt , Stephan Birkmann , PierreFerruit , Aurelie Guilbert , Bryan J Holler , John StansberryInstitution(s): 1. CNRS - UTINAM UMR, 2. European SpaceAgency, 3. Space Telescope Science Institute

219.11 – Potential and Challenges for Stereo 3DImaging with the Hubble and James Webb SpaceTelescopesImagine if we could perceive and visualize cometary outgassing,or see the elevation differences in cloud tops of Jupiter. Imagine ifwe could view Saturn's rings in their full depth, using real imagesrather than synthetic stereo pictures. Imagine if we could viewthese objects in 3D infrared. We present the basic constraints,challenges, and parameters in using both the Hubble andupcoming James Webb space telescopes for simultaneousspectroscopic imaging, across their common wavelength band (~

700-1600 nm) or in other applications, and outline potentialscience cases.

Author(s): Joel D. Green , Bonnie K. Meinke , Johannes MBurge , John StansberryInstitution(s): 1. Space Telescope Science Institute, 2.University of Pennsylvania

219.15 – A Microchannel Inlet to Reduce High-Velocity Impact Fragmentation of Molecules inOrbital and Fly-by Mass SpectrometersClosed source neutral mass spectrometers are often used on flybymissions to characterize the molecular components of planetaryexospheres. In a typical closed source, neutrals are thermalized asthey deflect off the walls within a spherical antechamber prior toionization and mass analysis. However, the high kinetic energy ofeach molecule as it impacts the chamber can lead tofragmentation before the ionization region is reached. Due to thisfragmentation, the original composition of the molecule can bealtered, leading to ambiguous identification. Even knowing the fragmentation pathways that occur may notallow deconvolution of data to give the correct composition. Onlystable, volatile fragments will be observed in the subsequent massspectrometer and different organic compounds likely give similarfragmentation products. Simply detecting these products will notlead to unambiguous identication of the precursor molecules.Here, we present a hardware solution to this problem—an inletthat reduces the fragmentation of molecules that impact at highvelocities. We present a microchannel inlet that reduces the impactfragmentation by allowing the molecules to dissipate kineticenergy faster than their respective dissociation lifetimes.Preliminary calculations indicate that impact-inducedfragmentation will be reduced up to three orders of magnitudecompared with conventional closed sources by using this inlet.The benefits of such an inlet apply to any orbital or flyby velocity.The microchannel inlet enables detection of semi-volatilemolecules that were previously undetectable due to impactfragmentation.

Author(s): Brandon Turner , Anupriya Anupriya , EricSevy , Daniel E. AustinInstitution(s): 1. Brigham Young University

219.16 – Performance, Calibration and Stability ofthe Mars InSight Mission Pressure SensorThe NASA Mars InSight Discovery Mission is primarily aimed atunderstanding the seismic environment at Mars and in turn theinterior structure of the planet. To this end, it carries a set of verysensitive seismometers to characterize fine ground movementsfrom quakes, impacts and tides. However, to remove atmosphericperturbations that would otherwise corrupt the seismic signals,InSight also carries a pressure sensor of unprecedented sensitivityand frequency response for a Mars mission. The instrument is based on a commercial spacecraft pressuresensor built by the Tavis Corporation. Tavis heritage transducershave provided pressure measurements on several interplanetarymissions, starting with a similar application on the VikingLanders. The sensor developed for the Insight mission is theirmost sensitive device. That same sensitivity was the root of thechallenges faced in the design and development for Insight. Ituses inductive sensing of a deformable membrane, and includesan internal temperature sensor to compensate for temperatureeffects in its overall response. The technical requirement on the pressure sensor performance is0.01(f/0.1)^(-2/3) Pa/sqrt(Hz) between 0.01 and 0.1 Hz, and 0.01Pa/sqrt(Hz) between 0.1 and 1 Hz. The actual noise spectrum isabout 0.01(f/0.3)^(-2/3) Pa/sqrt(Hz) between 0.01 and 1 Hz, andits frequency response (including inlet plumbing) has goodresponse up to about 10 Hz Nyquist (it will be sampled at 20 Hz). Achieving the required sensitivity proved to be a difficult

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engineering challenge, which necessitated extensiveexperimentation and prototyping of the electronics design. Inaddition, a late discovery of the introduction of noise by the signalprocessing chain into the measurement stream forced a last-minute change in the instrument’s firmware.

The flight unit has been calibrated twice, separated by a time spanof about 2 years due to the delay in launching the InSight mission.This has the benefit of allowing a direct measure of the stability ofthe pressure sensor over time. We will discuss the details of theperformance, calibration and stability of the pressure sensor inmore detail in our presentation.

Author(s): Don Banfield , Bruce Banerdt , Ken Hurst ,Jonny Grinblat , alex murray , Scott CarpenterInstitution(s): 1. Cornell Univ., 2. JPL/Caltech, 3. TavisCorporation

219.18 – The Plasma Instrument for MagneticSounding (PIMS) onboard the Europa ClipperMissionEuropa is embedded in a complex Jovian magnetospheric plasma,which rotates with the tilted planetary field and interactsdynamically with Europa’s ionosphere affecting the magneticinduction signal. Plasma from Io’s temporally varying torusdiffuses outward and mixes with the charged particles in Europa’sown torus producing highly variable plasma conditions. Onboardthe Europa Clipper spacecraft the Plasma Instrument forMagnetic Sounding (PIMS) works in conjunction with theInterior Characterization of Europa using Magnetometry(ICEMAG) investigation to probe Europa’s subsurface ocean. Thisinvestigation exploits currents induced in Europa’s interior by themoon’s exposure to variable magnetic fields in the Jovian systemto infer properties of Europa’s subsurface ocean such as its depth,thickness, and conductivity. This technique was successfullyapplied to Galileo observations and demonstrated that Europaindeed has a subsurface ocean. While these Galileo observationscontributed to the renewed interest in Europa, due to limitationsin the observations the results raised major questions that remainunanswered. PIMS will greatly refine our understanding ofEuropa’s global liquid ocean by accounting for contributions tothe magnetic field from plasma currents.

The Europa Clipper mission is equipped with a sophisticated suiteof 9 instruments to study Europa's interior and ocean, geology,chemistry, and habitability from a Jupiter orbiting spacecraft.PIMS on Europa Clipper is a Faraday Cup based plasmainstrument whose heritage dates back to the Voyager spacecraft.PIMS will measure the plasma that populates Jupiter’smagnetosphere and Europa’s ionosphere. The science goals ofPIMS are to: 1) estimate the ocean salinity and thickness bydetermining Europa’s magnetic induction response, corrected forplasma contributions; 2) assess mechanisms responsible forweathering and releasing material from Europa’s surface into theatmosphere and ionosphere; and 3) understand how Europainfluences its local space environment and Jupiter’smagnetosphere and vice versa.

In this presentation we describe the principles of PIMSoperations, detail the PIMS science goals, and discuss how toassess Europa's induction response.

Author(s): Joseph H. Westlake , Ralph L. McNutt , JustinC. Kasper , Abigail Rymer , Anthony Case , Corina Battista ,Corey Cochrane , David Coren , Alexander Crew , MatthewGrey , Xianzhe Jia , Krishan Khurana , Cindy Kim , MargaretG. Kivelson , Haje Korth , Norbert Krupp , Carol Paty , EliasRoussos , Michael Stevens , James A. Slavin , Howard T.Smith , Joachim SaurInstitution(s): 1. Georgia Institute of Technology, 2. JetPropulsion Laboratory, 3. Johns Hopkins Applied PhysicsLaboratory, 4. Max Planck Institute for Solar System Research,5. Smithsonian Astrophysical Observatory, 6. University ofCalifornia Los Angeles, 7. University of Cologne, 8. University ofMichigan

219.19 – Results of the first Seismometer toInvestigate Ice and Ocean Structure (SIIOS)Analogue MissionThe icy moons of Europa and Enceladus are thought to haveglobal subsurface oceans in contact with mineral-rich interiors,likely providing the ingredients needed for life as we know it. Thepossibility of life forming in the ocean or in melt pockets, relies onthe presence of a source of energy and chemistry for biologicalmolecule formation. A thick, stagnant ice crust would likelyprevent transfer of oxidants from the surface to the water, haltingthe development of life. The ice thickness and structure istherefore one of the most important and controversial topics inastrobiology. The best way to access an icy moon’s interior structure is with alander-based seismometer. Our team has identified acommercial-off-the-shelf device as a flight-candidate foroperation in the extreme environment of the icy moons. Based onestimates of Europan seismicity, the flight candidate device issensitive enough to detect the ice-water boundary and pockets ofliquid within the ice. Its low mass and low power enablesdeployment of multiple seismometers in a short-baseline array ona lander. The performance, mass, and volume of this device meetor exceed flight requirements identified in lander studies makinga field test of these seismometers highly representative of a flightunit developed for an Ocean Worlds mission. We report the results of the first field campaign for the SIIOSAnalogue Mission Program (AMP), which has evaluates theperformance of the flight candidate seismometer in Ocean Worldterrestrial analogue environments. In particular, the first SIIOSAMP field exercise is performed at Gulkana Glacier, Alaska.During the summer melt season Gulkana provides kilometer-scale regions of coexisting ice, water, and silicate material,thereby providing areas with the desired analogue seismiccontrasts. During this first mission, we have demonstrated devicesensitivity to the detection of seismicity from high frequency (>50 Hz) active and passive sources, the depth of ice-waterboundaries, and to the ice properties using a short-baseline (1m ) seismic array and a “lander-mounted” single stationseismometer.

Author(s): Daniella Della-Giustina , Veronica Bray ,Samuel "Hop" Bailey , Erin Pettit , Nicholas Schmerr , PeterDahl , Brad Avenson , Shane ByrneInstitution(s): 1. Avenson Audio, 2. University of AlaskaFairbanks, 3. University of Arizona, 4. University of MarylandCollege Park, 5. University of Washington Applied PhysicsLaboratoryContributing team(s): the SIIOS team

219.21 – The Small Next-generation AtmosphericProbe (SNAP) for Exploration of the Ice Giants - APSDS3 Mission Concept StudyThe Small Next-generation Atmospheric Probe (SNAP) missionconcept was selected under the NASA Planetary Science DeepSpace Small Satellite (PSDS3) call. Envisioned as a secondaryprobe on a future ice giant flagship mission nominally comprisingan orbiter and primary probe, SNAP would providemeasurements of spatially variable atmospheric properties suchas the abundances of key volatiles, the distribution of clouds andcloud-forming chemical species, thermal stratification andstability of the atmosphere, and the vertical profile of zonal windspeeds at the probe descent location. In addition to Uranus andNeptune, the SNAP design is also a viable Saturn entry probe. The SNAP mission concept would comprise a 30-kg entry probewith a diameter of ~0.5m (less than half the size of the Galileoprobe) that could descend through at least 5-bars. The baselinepayload would include an atmospheric structure instrument tomeasure the altitude profile of atmospheric pressure andtemperature, an atmospheric composition sensor, and anultrastable oscillator to enable radio science measurementsincluding Doppler wind tracking. An identical ultrastable

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oscillator would be carried within the probe relay link receiverhardware on the carrier spacecraft. All probe data, including pre-entry and entry calibration and housekeeping data, entryaccelerometry, and descent pressures, temperatures,composition, and zonal winds, would be returned to Earth byutilizing the carrier as a relay station.

The in-situ atmospheric investigations enabled by SNAP wouldlead to an improved understanding of the chemical and physicalprocesses that shape giant planet atmospheres, which in turnwould shed light on the formation and evolution processes of thegiant planets and the Solar System. The compositionmeasurements would also provide chemical evidence addressingtheories of planetary migration, thereby improving theunderstanding of the giant planets' role in promoting a habitableplanetary systems.

Author(s): David H. Atkinson , Kunio M. Sayanagi , robertA. Dillman , Drew J. Hope , Jing Li , Sarag J. Saikia , Amy A.Simon , Thomas R. Spilker , Michael H. WongInstitution(s): 1. Hampton University, 2. Jet PropulsionLaboratory - Retired, 3. Jet Propulsion Laboratory/CaliforniaInstitute of Technology, 4. NASA Ames Research Center, 5. NASAGoddard Space Flight Center, 6. NASA Langley Research Center,7. Purdue University, 8. University of California, Berkeley

219.22 – Intrepid: Exploring the NEA population with aFleet of Highly Autonomous SmallSat explorersThe Intrepid mission concept calls for phased deployment of afleet of small highly autonomous rendezvous spacecraft designedto characterize the evolution, structure and composition of dozensof Near-Earth Asteroids (NEAs). Intrepid represents a markeddeparture from conventional solar system exploration projects,where a single unique and complex spacecraft is typically directedto explore a single target body. In contrast, Intrepid relies on thedeployment of a large number of autonomous spacecraft toprovide redundancy and ensure that the project goals areachieved at a small fraction of the cost of typical missions. The Intrepid science goals are threefold: (1) to understand theevolutionary processes that govern asteroid physical, chemicaland dynamical histories and relate these results to solar systemorigins and evolution; (2) to facilitate impactor deflectionscenarios for planetary defense by statistically characterizingrelevant asteroid physical properties; (3) to quantify the presenceand extractability of potentially useful resources on a largesample of asteroids. To achieve these goals, the baselinearchitecture includes multiple modular instruments includingcameras, spectrometers, radar sounders, and projectiles thatcould interact with the target asteroid. Key questions to beaddressed are: what is the total quantity of water in each object?How is the water incorporated? Are organics present? What is theasteroid physical structure? How would the object respond toimpact/deflection? We have begun development of a miniature infrared pointspectrometer, a cornerstone of the Intrepid payload, coveringboth shortwave infrared (SWIR) and mid-infrared (MIR) spectralbands. The spectrometer is designed with a compact 2U form-factor, making it both relevant to Intrepid and implementable ona CubeSat. The combination of SWIR and MIR in a singleintegrated instrument would enable robust compositionalinterpretations from a single dataset combining both solarreflectance and thermal emission spectroscopy. Thesemeasurements would be crucial to determining the quantity andnature of water present.

Author(s): Jordana Blacksberg , Steven R. Chesley ,Bethany Ehlmann , Carol Anne RaymondInstitution(s): 1. California Institute of Technology, 2. JetPropulsion Laboratory

219.23 – Design of a hydrophone for an Ocean WorldlanderFor this presentation we describe the science return, and designof a microphone onboard a Europa lander mission. In additionto the E/PO benefit of a hydrophone to listen to the EuropaOcean, a microphone also provides scientific data on theproperties of the subsurface ocean. A hydrophone is a small light-weight instrument that could beused to achieve two of the three Europa Lander missionanticipated science goals of: 1) Asses the habitability (particularlythrough quantitative compositional measurements of Europa viain situ techniques uniquely available to a landed mission. And 2)Characterize surface properties at the scale of the lander tosupport future exploration, including the local geologic context. Acoustic properties of the ocean would lead to a betterunderstanding of the water density, currents, seafloor topographyand other physical properties of the ocean as well as lead to anunderstanding of the salinity of the ocean. Sound from watermovement (tidal movement, currents, subsurface out-gassing,ocean homogeneity (clines), sub-surface morphology, andbiological sounds. The engineering design of the hydrophone instrument will bedesigned to fit within a portion of the resource allocation of thecurrent best estimates of the Europa lander payload (26.6 Kg,24,900 cm3, 2,500 W-hrs and 2700 Mbits). The hydrophonepackage will be designed to ensure planetary protection ismaintained and will function under the current Europa landermission operations scenario of a two-year cruise phase, and 30-day surface operational phase on Europa. Although the microphone could be used on the surface, it isdesigned to be lowered into the subsurface ocean. As such,planetary protection (forward contamination) is a primarychallenge for a subsurface microphone/ camera. The preliminarydesign is based on the Navy COTS optical microphone. Reference: Pappalardo, R. T., et al. "Science potential from aEuropa lander." Astrobiology 13.8 (2013): 740-773.

Author(s): Heather D Smith , Andrew G. DuncanInstitution(s): 1. Desert Sensors, 2. NASA Ames ResearchCenter

219.24 – SmallSat Innovations for PlanetaryScienceAs NASA continues to look for ways to fly smaller planetarymissions such as SIMPLEX, MoO, and Venus Bridge, it isimportant that spacecraft and instrument capabilities keep paceto allow these missions to move forward. As spacecraft becomesmaller, it is necessary to balance size with capability, reliabilityand payload capacity. Ball Aerospace offers extensive SmallSatcapabilities matured over the past decade, utilizing our broadexperience developing mission architecture, assemblingspacecraft and instruments, and testing advanced enablingtechnologies. Ball SmallSats inherit their software capabilitiesfrom the flight proven Ball Configurable Platform (BCP) line ofspacecraft, and may be tailored to meet the unique requirementsof Planetary Science missions. We present here recent efforts inpioneering both instrument miniaturization andSmallSat/sensorcraft development through mission design andimplementation. Ball has flown several missions with small, butcapable spacecraft. We also have demonstrated a variety ofenhanced spacecraft/instrument capabilities in the laboratoryand in flight to advance autonomy in spaceflight hardware thatcan enable some small planetary missions.

Author(s): Jonathan Weinberg , Shelley Petroy , ShaneRoark , Eric SchindhelmInstitution(s): 1. Ball Aerospace and Technologies Corp.

220.01 – Confining the Rings of Chariklo withResonant Perturbations

Until recently, ring systems were thought to exist only aroundlarge planets. In 2013, a stellar occultation discovered ringsaround the centaur Chariklo; subsequently, a set of rings has been

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proposed to exist around the centaur Chiron. Similarities in theseminor-body systems include a small nucleus (~220-240 km), withtwo narrow rings (a few km in width) separated by a gap (~8-12km). Possible methods for confinement of such narrow ringsinclude shepherding satellites or apse alignment due to selfgravity. We present the results of numerical simulations of asystem like that observed around Chariklo to investigate ringconfinement by a resonant perturbation. The simulations includea range of perturber configurations including only collisionswithout self-gravity as well as one simulation with self-gravity toshow that the confinement mechanism is robust. Comparison to asimulation with no resonant perturbation shows that oursimulations are capable of measuring the viscous spread of thisring system.

Simulations include a single perturber with masses between 10and 10 kg, corresponding to diameters on the order of 1-2 km.These perturbers are small enough and close enough to thecentral body that they would not be visible in Hubbleobservations. The ring material starts off with gaussian densityprofiles centered on the observed locations of the rings. The ringparticles are 3-10 m in radius. The longest simulations were runfor ~12 orbits.

Results from the simulations include: - the width of the rings begins to narrow after a few synodicperiods with the perturber, at the point when the streamlinesintersect; - there isn’t a preference for the resonance with one ring, but theneed to have both rings in resonance provides a constraint; - the perturber can be located exterior or interior to the rings. The robustness of the mechanism leaves open the possibility thatthe perturbation comes from a mass anomaly on the central bodyitself. This is supported by observational indications that the spinrate of Chariklo is in resonance with the orbital period of its mainring. Simulation results are used to generate synthetic stellaroccultation chords for direct comparison with observations.

Author(s): Mark C. Lewis , Amanda A. SickafooseInstitution(s): 1. SAAO, 2. Trinity Univ.

220.02 – Multi-Wavelength investigation of the co-orbital moons Dione and HeleneThe icy satellites Dione and Helene share the same orbit, at 6.26Saturn radii from the giant planet, which is within Saturn’sdiffuse E ring. Helene is one of Dione’s two Trojan moons, locatedin the leading Lagrangian point L4 of Dione’s orbit. We presenthere preliminary results on the investigation of the Dione-Heleneduo in term of origin, formation and evolution. Specifically, thekey objectives are to retrieve the photometric properties andcomposition of the moons to answer questions such as: Are theDione and Helene surfaces made of the same material? Did theyform in the same region of the Solar System? Is one satelliteolder than the other? Have they experienced the same amount ofspace weathering? To provide the most complete evaluation of the Dione and Helenesurfaces and advance our understanding of how exogenicprocesses affect the surfaces of icy satellites we use the synergy offour of the Cassini instruments: UVIS (Ultraviolet ImagingSpectrograph), ISS (Imaging Science Subsystem), VIMS (Visualand Infrared Mapping Spectrometer) and CIRS (CompositeInfrared Spectrometer). Composite disk-integrated spectra ofboth moons have been produced to conduct spectral modelingover a large wavelength range from the ultraviolet to the infrared,from 111nm to 1mm. Until now, most investigations have focusedonly on one wavelength domain, telling only part of the story. Amulti-wavelength analysis allows an in-depth investigation of thesurfaces of the Saturnian satellites as each wavelength probes adifferent layer of the surface. Special attention is directed towardthe search for correlations of basic properties (albedo, scatteringproperties, texture, grain size, composition, porosity, thermalproperties) between Dione and Helene.

Author(s): Emilie M. Royer , Amanda R. Hendrix , CarlyHowett , Linda SpilkerInstitution(s): 1. JPL, 2. PSI, 3. SwRI, 4. University ofColorado

220.03 – A Global Geologic Map of EuropaUnderstanding the global scale geology of Europa is paramount togaining insight into the potential habitability of this icy world. Tothis end, work is ongoing to complete a global geological map atthe scale of 1:15 million that incorporates data at all resolutionscollected by the Voyager and Galileo missions. The results of thiswork will aid the Europa Clipper mission, now in formulation, byproviding a framework for collaborative and synergistic scienceinvestigations. To understand global geologic and tectonic relations, a total of 10geologic units have been defined. These include: Low AlbedoRidge Material (lam)—low albedo material that irregularlysurrounds large (>20 km) ridge structures; Ridged plains (pr)—distributed over all latitudes and characterized by subparallel tocross-cutting ridges and troughs visible at high resolution (<100m/px); Band material (b)—linear to curvilinear zones with adistinct, abrupt albedo change from the surrounding region;Crater material (c), Continuous Crater Ejecta (ce) andDiscontinuous Crater Ejecta (dce)—features associated withimpact craters including the site of the impact, crater material,and the fall-out debris respectively; Low Albedo Chaos (chl),Mottled Albedo Chaos (chm) and High Albedo Chaos (chh)—disrupted terrain with a relatively uniform low albedo,patchy/variegated albedo, and uniform high albedo appearancerespectively; Knobby Chaos (chk) - disrupted terrain with roughand blocky texture occurring in the high latitudes. In addition to the geologic units, our mapping also includesstructural features—Ridges, Cycloids, Undifferentiated Linea,Crater Rims, Depression Margins, Dome Margins and Troughs.We also introduce a point feature (at the global scale),Microchaos, to denote small (<10 km) patches of discontinuouschaos material. The completed map will constrain the distributionof different Europa terrains and provide a general stratigraphicframework to assess the geologic history of Europa from theregional to the global scale.

Author(s): Erin Janelle Leonard , Donald Alex Patthoff ,David A. Senske , Geoffrey CollinsInstitution(s): 1. Jet Propulsion Laboratory, 2. PlanetaryScience Institute, 3. University of California Los Angeles, 4.Wheaton College

220.04 – Fracture formation post impact onEnceladus?Saturn’s small icy moon Enceladus was observed by the Cassinimission to have jets of ice and vapor emanating from its southernpolar terrain (SPT), creating a plume. The fact that the activity isonly observed in one region has not been well explained.Hypotheses include a regional sea beneath the SPT or a globalocean that is thicker beneath the SPT, which feeds a group offractures observed there called the tiger stripes. As Enceladusorbits Saturn, stresses acting on the moon may open and close thefractures enabling interior volatiles to escape and form the plume.Here we investigate how these fractures could have formed andthe activity begun. We propose that an impact could have eitherpunctured through or caused substantial melt and fracturing inan ice shell connecting to a liquid layer below. Our goal is todetermine whether a formation of fractures resembling the tigerstripes could emerge post-impact. Previous work by Roberts and Stickle (LPSC 2017, #1955)modeled an impact into an ice shell over an ocean and calculatedpenetration depth and melt temperatures and volumes throughthe shell thickness. Fracturing would occur during and after theimpact, the crater would collapse, water would begin to refreezeand subsequent fluid exchange would occur. Working forwardfrom a point after impact and as the ice shell begins refreezing, weperformed finite element modeling to simulate the probableformation of fractures based on the resulting stress regime. Herewe explore fracture formation for shells ranging from 1 km to 5km thick (consistent with gravity and libration studies), to explore

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formation as the shell cools and thickens through time. Weemplaced several fractures, penetrating either entirely or partiallyacross the base to surface. Fracture interactions, tidal stressforcing with orbital true anomalies and ocean waterpressurization are considered free parameters in the model. Wepresent results for a number of parameter value combinationsand quantify fracture formation sensitivities to modelparameters.

Author(s): Kathleen Craft , James RobertsInstitution(s): 1. Johns Hopkins Applied Physics Laboratory

220.05 – Seismic signal and noise on EuropaSeismology is one of our best tools for detailing interior structureof planetary bodies, and a seismometer is included in the baselineand threshold mission design for the upcoming Europa Landermission. Guiding mission design and planning for adequatescience return, though, requires modeling of both the anticipatedsignal and noise. Assuming ice seismicity on Europa behavesaccording to statistical properties observed in Earth catalogs andscaling cumulative seismic moment release to the moon, we cansimulate long seismic records and estimate background noise andpeak signal amplitudes (Panning et al., 2017). This suggests asensitive instrument comparable to many broadband terrestrialinstruments or the SP instrument from the InSight mission to

Mars will be able to record signals, while high frequencygeophones are likely inadequate. We extend this analysis to alsobegin incorporation of spatial and temporal variation due to thetidal cycle, which can help inform landing site selection. We alsobegin exploration of how chaotic terrane at the bottom of the iceshell and inter-ice heterogeneities (i.e. internal melt structures)may affect anticipated seismic observations using 2D numericalseismic simulations. M. P. Panning, S. C. Stähler, H.-H. Huang, S. D. Vance, S. Kedar,V. C. Tsai, W. T. Pike, R. D. Lorenz, “Expected seismicity and theseismic noise environment of Europa,” J. Geophys. Res., inrevision, 2017.

Author(s): Mark Panning , Simon Stähler , Bruce Bills ,Jorge Castillo Castellanos , Hsin-Hua Huang , Allen Husker ,Sharon Kedar , Ralph Lorenz , William T. Pike , NicholasSchmerr , Victor Tsai , Steven VanceInstitution(s): 1. Academia Sinica, 2. California Institute ofTechnology, 3. ETH Zürich, 4. Imperial College, 5. Jet PropulsionLaboratory/California Institute of Technology, 6. Johns HopkinsUniversity, Applied Physics Laboratory, 7. UniversidadNacional Autonoma de Mexico, 8. University of Maryland

221.01 – Chaotic Mountain Blocks in Pluto’sSputnik PlanitiaOne of the first high-resolution Pluto images returned by NewHorizons displayed a collection of tall, jagged peaks rising out ofthe large nitrogen ice sheet informally known as Sputnik Planitia(SP). This mountain range was later revealed to be one of severalalong the western edge of SP. The mountains are several hundredbroken-up blocks of Pluto’s primarily water ice lithosphere andsome retain surface terrains similar to the nearby intact crustsurrounding SP. Water ice with some fractures or porosity islikely >5% less dense than solid N ice at Pluto’s temperatures.Thus it is possible the blocks are, or were, floating icebergs or atleast partially suspended to the point that some blocks appear tobe tilted as if they have faltered (Moore et al., 2016, Science, 351,1284-1293).

We analyze four mountain ranges on the western edge of SP andcompare to chaotic terrains on Europa and Mars. The blocks onPluto have angular planforms but we characterize their size usingblock surface area converted to an equivalent circular diameter.Topography was used to define block extents. The blocks range insize from 3-30 km in diameter, with a mode of ~8-10 km. Blocksrange from 0.2-3.8 km in height, and block height generallyincreases with block diameter. One or more dark layers can beidentified in a few scarp faces, and are at a similar depth to eachother and to layers seen in fault and crater walls elsewhere onPluto. A large N-S trending fault system runs tangential to SP andmay be the source of crustal disruption on the western side.

On Europa and Mars block sizes vary greatly between differentchaos regions, but Conamara Chaos has an average block size of~5 km in diameter, smaller than that typically seen on Pluto. Alsothe blocks often transition into fractured terrain still connected tothe surround lithosphere at the periphery of the chaos regions.The source regions for the blocks are more obvious on Europaand Mars. Additionally the block heights on Europa and Marsgenerally do not increase with block size. Thus, the mainmechanism of crustal breakup is likely different between thesebodies.

Author(s): Kelsi N. Singer , Katherine I Knight , S. AlanStern , Catherine Olkin , William M. Grundy , William B.McKinnon , Jeffrey M. Moore , Paul M. Schenk , John R.Spencer , Harold A Weaver , Leslie Young , Kimberly EnnicoInstitution(s): 1. Carson-Newman University, 2. JohnsHopkins University Applied Physics Laboratory, 3. LowellObservatory, 4. Lunar and Planetary Institute, 5. NASA AmesResearch Center, 6. Southwest Research Institute Boulder, 7.Washington University in St. LouisContributing team(s): The New Horizons Geology, Geophysicsand Imaging Science Theme Team, The New Horizons SurfaceComposition Science Theme Team

221.02 – The Color of Pluto from New HorizonsThe New Horizons flyby provided the first high-resolution colormaps of Pluto. These maps show the color variegation across thesurface from the very red terrain in the equatorial region, to themore neutral colors of the volatile ices in Sputnik Planitia, theblue terrain of east Tombaugh Regio and the yellow hue onPluto's north pole. There are two distinct color mixing lines in thecolor-color diagrams derived from images of Pluto. Both mixinglines have an apparent starting point in common: the relativelyneutral color volatile-ice covered terrain. One line extends to thedark red terrain exemplified by Cthulu Regio and the otherextends to the yellow hue in the northern latitudes. The red coloris consistent with a non-ice component on the surface and isconsistent with tholins.

Author(s): Catherine Olkin , John R. Spencer , WilliamM. Grundy , Alex Parker , Ross A. Beyer , Dennis Reuter , PaulM. Schenk , S. Alan Stern , Harold A Weaver , Leslie Young ,Kimberly Ennico , Richard P Binzel , Marc W. Buie , Jason C.Cook , Dale P. Cruikshank , Cristina M. Dalle Ore , AlissaEarle , Carly Howett , Donald E. Jennings , Kelsi N. Singer ,Ivan Linscott , Allen Lunsford , Silvia Protopapa , BernardSchmitt , Eddie WeigleInstitution(s): 1. Applied Physics Laboratory, 2. Big HeadEndian, 3. Lowell Observatory, 4. Lunar and PlanetaryInstitute, 5. MIT, 6. NASA Ames Research Center, 7. NASA GSFC,8. Pinhead Institute, 9. SETI, 10. Southwest Research Institute,11. Stanford University, 12. University Grenoble, 13. Universityof MarylandContributing team(s): and the New Horizons Science Team

221.03 – Probing the Hill Sphere of 2014 MUwith HST FGS

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During HST GO/DD Program 15003, we observed the July 17,2017 stellar occultation by the Kuiper Belt object 2014 MU , theclose flyby target of the extended New Horizons mission. Ratherthan capture a solid body occultation by the KBO itself, ourprogram aimed to constrain the opacity of rings or other debris inthe 2014 MU system. We used the HST FGS instrument inTRANS F583W mode to collect 40 Hz time resolution photometryof the stellar occultation star for 2 orbits during this observation.We present the results of reduction and calibration of the FGSphotometry, accounting for the different photometric sensitivitiesof the four PMTs of the instrument. From this, we then set limitson rings or other dust opacity within the Hill sphere of 2014MU at distances up to 75,000 km from the main body.

Author(s): Joshua Kammer , Tracy M Becker , Kurt D.Retherford , S. Alan Stern , Catherine Olkin , Marc W. Buie ,John R. Spencer , Amanda S. Bosh , Lawrence H. WassermanInstitution(s): 1. Lowell Observatory, 2. MassachusettsInstitute of Technology, 3. Southwest Research Institute, 4.Southwest Research Institute

221.04 – The Dynamical History of Chariklo and ItsRingsChariklo is the only small Solar system body confirmed to haverings. Given the instability of its orbit, the presence of rings issurprising, and their origin remains poorly understood. In thiswork, we study the dynamical history of the Chariklo system by

integrating almost 36,000 Chariklo clones backwards in time forone Gyr under the influence of the Sun and the four giant planets.By recording all close encounters between the clones and planets,we investigate the likelihood that Chariklo's rings could havesurvived since its capture to the Centaur population. Our resultsreveal that Chariklo's orbit occupies a region of stable chaos,resulting in its orbit being marginally more stable than those ofthe other Centaurs. Despite this, we find that it was most likelycaptured to the Centaur population within the last 20 Myr, andthat its orbital evolution has been continually punctuated byregular close encounters with the giant planets. The greatmajority (> 99%) of those encounters within one Hill radius of theplanet have only a small effect on the rings. We conclude thatclose encounters with giant planets have not had a significanteffect on the ring structure. Encounters within the Roche limit ofthe giant planets are rare, making ring creation through tidaldisruption unlikely.

Author(s): Jeremy R Wood , Jonti Horner , Tobias Hinse ,Stephen MarsdenInstitution(s): 1. Computational Engineering and ScienceResearch Centre University of Southern Queensland, 2. HazardCommunity and Technical College, 3. Korea Astronomy andSpace Science Institute

222.01 – High pressure ices are not the end of thestory for large icy moons habitability: experimentalstudies of salts effects on high pressure ices and theimplications for icy worlds large hydrospherestructure and chemical evolutionThe presence of several phases of deep high-pressure ices in largeicy moons hydrosphere has often been pointed as a majorlimitation for the habitability of an uppermost ocean. As they aregravitationally stable bellow liquid H O, they are thought to actas a chemical barrier between the rocky bed and the ocean.Solutes, including salt species such as NaCl and MgSO , havebeen suggested inside icy world oceans from remote sensing,magnetic field measurements and chondritic material alterationmodels. Unfortunately, the pressures and temperatures insidethese hydrospheres are very different from the one found in Earthaqueous environments, so most of our current thermodynamicdatabases do not cover the range of conditions relevant formodeling realistically large icy worlds interiors. Recent experimental results have shown that the presence ofsolutes, and more particularly salts, in equilibrium with highpressure ices have large effects on the stability, buoyancy andchemistry of all the phases present at these extreme conditions. In particular brines have been measured to be sometimes moredense than the high pressure ices at melting conditions, possiblycreating several oceanic layer "sandwiched" in between two ices

shells or in contact with the rocky bed. Other effects currently being investigated by our research groupalso covers ice melting curve depressions that depend on the saltspecies and incorporation of solutes inside the crystallographiclattice of high pressure ices. Both of these could have veryimportant implication at the planetary scale, enablingthicker/deeper liquid oceans, and allowing chemicaltransportation through the high pressure ice layer in large icyworlds. We will present the latest results obtained in-situ using diamondanvil cell high pressure allowing to probe the density, chemistryand thermodynamic properties of high pressure ice and aqueoussolutions in equilibrium with Na-Mg-SO -Cl ionic species. We will also discuss the new planetary evolution scenariosimplied by these new material and thermodynamic properties andhow this could suggest the existence of new habitableenvironments in large icy worlds, even when high pressure icesdominate the total volume of the hydrosphere.

Author(s): Baptiste Journaux , Evan Abramson , J. MichaelBrown , Olivier BollengierInstitution(s): 1. University of Washington

223.01 – The Planetary Data System (PDS) DataDictionary Tool (LDDTool)One of the major design goals of the PDS4 development effort wasto provide an avenue for discipline specialists and large datapreparers such as mission archivists to extend the core PDS4Information Model (IM) to include metadata definitions specificto their own contexts. This capability is critical for the PlanetaryData System - an archive that deals with a data collection that isdiverse along virtually every conceivable axis. Amid suchdiversity, it is in the best interests of the PDS archive and its usersthat all extensions to the core IM follow the same designtechniques, conventions, and restrictions as the coreimplementation itself. Notwithstanding, expecting all missionand discipline archivist seeking to define metadata for a newcontext to acquire expertise in information modeling, model-driven design, ontology, schema formulation, and PDS4 designconventions and philosophy is unrealistic, to say the least.

To bridge that expertise gap, the PDS Engineering Node hasdeveloped the data dictionary creation tool known as “LDDTool”.This tool incorporates the same software used to maintain andextend the core IM, packaged with an interface that enables adeveloper to create his contextual information model using thesame, open standards-based metadata framework PDS itself uses.Through this interface, the novice dictionary developer hasimmediate access to the common set of data types and unitclasses for defining attributes, and a straight-forward method forconstructing classes. The more experienced developer, using thesame tool, has access to more sophisticated modeling methodslike abstraction and extension, and can define very sophisticatedvalidation rules. We present the key features of the PDS Local Data DictionaryTool, which both supports the development of extensions to thePDS4 IM, and ensures their compatibility with the IM.

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Author(s): Anne C. Raugh , John S. HughesInstitution(s): 1. Jet Propulsion Laboratory, 2. University ofMaryland

223.02 – Planetary Sciences Literature - Access andDiscoveryThe NASA Astrophysics Data System (ADS) has been around forover 2 decades, helping professional astronomers and planetaryscientists navigate, without charge, through the increasinglycomplex environment of scholarly publications. As boundariesbetween disciplines dissolve and expand, the ADS providespowerful tools to help researchers discover useful informationefficiently. In its new form, code-named ADS Bumblebee(https://ui.adsabs.harvard.edu), it may very well answerquestions you didn't know you had! While the classic ADS(http://ads.harvard.edu) focuses mostly on searching basicmetadata (author, title and abstract), today's ADS is bestdescribed as a an "aggregator" of scholarly resources relevant tothe needs of researchers in astronomy and planetary sciences,and providing a discovery environment on top of this. In additionto indexing content from a variety of publishers, data andsoftware archives, the ADS enriches its records by text-miningand indexing the full-text articles (about 4.7 million in total, with

g130,000 from planetary science journals), enriching its metadatathrough the extraction of citations and acknowledgments. Recenttechnology developments include a new ApplicationProgramming Interface (API), a new user interface featuring avariety of visualizations and bibliometric analysis, and integrationwith ORCID services to support paper claiming. The new ADSprovides powerful tools to help you find review papers on a givensubject, prolific authors working on a subject and who they arecollaborating with (within and outside their group) and papersmost read by by people who read recent papers on the topic ofyour interest. These are just a couple of examples of thecapabilities of the new ADS. We currently index most journalscovering the planetary sciences and we are striving to includethose journals most frequently cited by planetary sciencepublications. The ADS is operated by the SmithsonianAstrophysical Observatory under NASA Cooperative AgreementNNX16AC86A.

Author(s): Edwin A. HennekenInstitution(s): 1. Smithsonian Astrophysical Obs.Contributing team(s): The ADS Team

224.01 – Planetary Science with the StratosphericObservatory for Infrared Astronomy (SOFIA)The Stratospheric Observatory for Infrared Astronomy (SOFIA) isexecuting observations as part of its 5th annual proposal cycle.This poster compiles some scientific highlights from observationsto date, lists pending observations, and statistically summarizesguest observer participation in SOFIA. We have observed comets,asteroids, Venus, Mars, Jupiter, Saturn, Neptune, Kuiper BeltObjects, and extrasolar planets. Infrared obsrvations from ourobservatory have been used to characterize surfaces,atmospheres, and dust. We describe the observatory capabilities,highlighting our scientific instrument in development. Wedescribe future capabilities of the observatory, to encourage newproposals that can utilize this unique facility for planetaryscience.

Author(s): William T. ReachInstitution(s): 1. Universities Space Research AssociationContributing team(s): SOFIA Science Mission Operations

224.02 – Remote microscopy and volumetricimaging on the surface of icy satellitesWith NASA PIDDP support we have applied recent advancementsin Fourier-domain microscopy to develop an instrument capableof microscopic imaging from meter-scale distances for use on aplanetary lander on the surface of an icy satellite or otherplanetary bodies. Without moving parts, our instrument projectsdynamic patterns of laser light onto a distant target using alightweight large-aperture reflector, which then collects the lightscattered or fluoresced by the target on a fast photon-bucketdetector. Using Fourier Transform based techniques, wereconstruct an image from the detected light. The remotemicroscope has been demonstrated to produce 2D images withbetter than 15 micron lateral resolution for targets at a distance of5 meters and is capable of linearly proportionally higherresolution at shorter distances. The remote microscope is alsocapable of providing three-dimensional (3D) microscopic imagingcapabilities, allowing future surface scientists to explore themorphology of microscopic features in surface ices, for example.The instrument enables microscopic in-situ imaging during dayor night without the use of a robotic arm, greatly facilitating thesurface operations for a lander or rover while expanding the areaof investigation near a landing site for improved science targeting.We are developing this remote microscope for in-situ planetaryexploration as a collaboration between the Southwest ResearchInstitute, LambdaMetrics, and the University of Colorado.

Author(s): Alejandro Soto , Keith Nowicki , Carly Howett ,Daniel Feldkhun , Kurt D. RetherfordInstitution(s): 1. LambdaMetrics, 2. Southwest ResearchInstitute, 3. Southwest Research Institute

224.03 – The Development of A Chip-ScaleSpectrometer for In Situ Characterization of SolarSystem SurfacesWe discuss the development of a plasmonic spectrometer for insitu characterization of solar system surface and subsurfaceenvironments. The two goals of this project are to (1)quantitatively demonstrate that a plasmonic spectrometer can beused to rapidly acquire high signal-to-noise spectra between 0.5 -1.0 microns at a spectral resolution suitable for unambiguousdetection of spectral features indicative of volatiles andcharacteristic surface mineralogies, and (2) demonstrate that thisclass of spectrometer can be used in conjunction with opticalfibers to access subsurface materials and vertically map thegeochemistry and mineralogy of subsurface layers, therebydemonstrating that a plasmonic spectrometer is feasible in a low-mass, low-power, compact configuration. Our prototypespectrometer is comprised of a broadband lamp/source, a fiberoptic system to illuminate the sample surface and collect thereflected light, a mosaic filter element based on plasmonresonance, and a focal plane array (FPA) detector. Our work thusfar has been divided into two primary areas: (i) the developmentof the plasmon filter element and (ii) the construction of a testbedto explore the source, fiber system and focal plane arraycomponents of the system. We discuss our preliminary designstudies of the plasmonic nanostructure prototypes to optimize thefull-width half-maximum of the filter, and our fiber illuminationand signal collection system.

Author(s): Nancy J. Chanover , David Voelz , Sang-YeonCho , Charles PelzmanInstitution(s): 1. New Mexico State Univ.

224.04 – Gas And Ice Spectrometer/Radar(GAISR): a new instrument for close-up cometactivity observationsThe Rosetta mission at 67P/Churyumov-Gerasimenko enabledthe first detailed and long-term survey of cometary activity, whichoccurs primarily through water outgassing and emission of dust.Its highly-capable instrument suite improved our understandingof the outgassing and the dust emission and size distributionseparately, however the coupling between the two remains poorlyunderstood. GAISR consists of a dual-channel submillimeter-wave spectrometer inspired from MIRO/Rosetta, coupled to asmall-particle Doppler radar for simultaneous observations of

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outgassing and emission of the large dust particles (comprisingmost of the mass emitted) in cometary jets and plumes of outersolar system satellites. GAISR’s medium-range W-band (95 GHz)radar will operate in a frequency-modulated continuous-wave(FMCW) mode with 1 Watt of transmit power to achieve highsensitivity detection of the range and velocity distribution of 0.1-10 mm sized ice and dust particles released by jets and plumes.The radar’s primary aperture also functions as an antenna for twopassive heterodyne spectrometer channels at 270 and 560 GHzfor detecting the abundance, temperature, and velocity of watervapor and its isotopes (including HDO), as well other majorcometary volatiles such as CO, NH , CH OH. GAISR has beendesigned with a priority placed on low mass and power needs, tofacilitate its infusion in future planetary missions. This isaccomplished by leveraging recent innovations in W-band signalgeneration using low power silicon integrated circuits, state-of-the art III-V semiconductor devices for signal amplification anddetection, and compact quasioptical duplexing. A new signalprocessing algorithm for FMCW Doppler radar detection out tothe maximum range ambiguity limit has also been developed.GAISR’s performance testing has begun, and this poster willsummarize its proven capabilities and plans for validation inrelevant environments.

Author(s): Ken Cooper , Raquel Monje , Corey Cochrane ,Adrian Tang , Maria Alonso , Robert Dengler , Stephen Durden ,Mathieu ChoukrounInstitution(s): 1. Jet Propulsion Laboratory, CaliforniaInstitute of Technology

224.05 – Raman Spectrograph for Ocean Worlds:Integrating Cavity Enhanced SpectroscopyWe present a new concept for a Raman spectrograph instrumentdesigned to conduct high sensitivity measurements of biomarkerswithin Ocean Worlds environments. Our Raman Spectrograph forOcean worlds (RSO) instrument is a UV+IR multi-laser enhancedRaman system capable of detecting complex, biologically-relevantmolecular species mixed within icy surfaces in the outer SolarSystem. Incorporating two or more lasers with differentexcitation-emission pathways is crucial for thorough anddefinitive interpretation of the spectral fingerprints that identifyunknown constituents within a sample. Our approach strives toremove fluorescence-driven ambiguities from degenerate, non-unique signatures expected for the most interesting traceconstituents, i.e., those best revealed by UV excitation. Our design

for deep-UV measurements is based on a novel high-reflectivityintegrating cavity invented at Texas A&M University and furtherdeveloped at SwRI. We report nanomole-range sensitivities ofseveral complex organic molecules measured with our laboratoryprototype cavities. Weak optical signals from Raman orfluorescence based instruments require sensitive low-noisedetectors and long integration times, which by comparison areundesirable for the high radiation environment and limitedbattery power conditions anticipated for the Europa Landermission. The two-to-five orders of magnitude enhancedsensitivity over standard Raman spectroscopy enabled by theintegrating cavity enhanced spectroscopy technique makes it wellsuited for the Europa Lander payload and other future OceanWorlds missions.

Author(s): Kurt D. Retherford , Thomas Z Moore , MichaelW Davis , Carly Howett , Alejandro Soto , Ujjwal Raut ,Philippa M Molyneux , Keith Nowicki , Kathleen Mandt ,Britney E Schmidt , John Mason , Vladislav V Yakovlev ,Edward S FryInstitution(s): 1. Georgia Institute of Technology, 2. JHUApplied Physics Lab, 3. Southwest Research Inst., 4. Texas A&MUniversityContributing team(s): the RSO Team

224.06 – The TESS Science Support Center and theGuest Investigator ProgramThe Transiting Exoplanet Survey Satellite (TESS) Mission willhave a robust Guest Investigator (GI) program that will be run bythe TESS Science Support Center located at NASA Goddard SpaceFlight Center. Following the highly successful Kepler/K2 GuestObservers (GO) program, the TESS Science Support Center willsupport the astronomical and planetary science community inpreparing proposals and providing tools and user support for dataretrieval, processing and analysis. I will present the overallstructure and plan for the GI program, and discuss data products,GI allocations, observing modes, tools and support as we preparefor the first proposal cycle.

Author(s): Elisa V. Quintana , Patricia T. Boyd , ThomasBarclay , Joshua E. SchliederInstitution(s): 1. NASA Goddard Space Flight Center

300.01 – Laboratory Simulations on HazeFormation in Cool Exoplanet AtmospheresThe Kepler mission has shown that the most abundant types ofplanets are super-Earths and mini-Neptunes among ~3500confirmed exoplanets, and these types of exoplanets are expectedto exhibit a wide variety of atmospheric compositions. Recenttransit spectra have demonstrated that clouds and/or hazes couldplay a significant role in these planetary atmospheres (Deming etal. 2013, Knutson et al. 2014, Kreidberg et al. 2014, Pont, et al.2013). However, very little laboratory work has been done tounderstand the formation of haze over a broad range ofatmospheric compositions. Here we conducted a series oflaboratory simulations to investigate haze formation in a range ofplanetary atmospheres using our newly built Planetary HAZEResearch (PHAZER) chamber (He et al. 2017). We ranexperimental simulations for nine different atmospheres: threetemperatures (300 K, 400 K, and 600 K) and three metallicities(100, 1000, and 10000 times solar metallicity) using AC glowdischarge as an energy source to irradiate gas mixtures. We foundthat haze particles are formed in all nine experiments, but thehaze production rates are dramatically different for differentcases. We investigated the particle sizes of the haze particlesdeposited on quartz discs using atomic force microscopy (AFM).The AFM images show that the particle size varies from 30 nm to200 nm. The haze particles are more uniform for 100x solarmetallicity experiments (30 nm to 40 nm) while the particlessizes for 1000x and 10000x solar metallicity experiments have

wider distributions (30 nm to 200 nm). The particle size affectsthe scattering of light, and thus the temperature structure ofplanetary atmospheres. The haze production rates and particlesize distributions obtained here can serve as critical inputs toatmospheric physical and chemical tools to understand theexoplanetary atmospheres and help guide future TESS and JWSTobservations of super-Earths and mini-Neptunes. Ref: Deming, D., et al. 2013, ApJ, 774, 95. He, C., et al. 2017, APJL, 841, L31. Knutson, H. A., et al. 2014, Nat. 505, 66. Kreidberg, L., et al. 2014, Nat. 505, 69. Pont, F., et al. 2013, MNRAS, 432, 2917.

Author(s): Chao He , Sarah Horst , Nikole Lewis , XintingYu , Patricia McGuiggan , Julianne I. MosesInstitution(s): 1. Johns Hopkins University, 2. Space ScienceInstitute, 3. Space Telescope Science Institute

300.02 – Haze production in the atmospheres ofsuper-Earths and mini-Neptunes: Insight fromPHAZER lab Super-Earths and mini-Neptunes (~1.2-3 Earth radii) comprise alarge fraction of planets in the universe and TESS (TransitingExoplanet Survey Satellite) will increase the number that areamenable to atmospheric characterization with observatories likeJWST (James Webb Space Telescope). These atmospheres shouldspan a large range of temperature and atmospheric composition

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phase space, with no solar system analogues. Interpretation ofcurrent and future atmospheric observations of super-Earths andmini-Neptunes requires additional knowledge about atmosphericchemistry and photochemical haze production. We haveexperimentally investigated haze formation for H , H O, andCO dominated atmospheres (100x, 1000x, and 10000x solarmetallicity) for a range of temperatures (300 K, 400 K, and 600K) using the PHAZER (Planetary Haze Research) experiment atJohns Hopkins University. This is a necessary step inunderstanding which, if any, super-Earths and mini-Neptunespossess the conditions required for efficient production ofphotochemical haze in their atmospheres. We find that theproduction rates vary over a few orders of magnitudes with somehigher than our nominal Titan experiments. We therefore expectthat planets in this temperature and atmospheric compositionphase space will exhibit a range of particle concentrations andsome may be as hazy as Titan.

Author(s): Sarah Horst , Chao He , Eliza Kempton ,Julianne I. Moses , Veronique Vuitton , Nikole LewisInstitution(s): 1. Grinnell, 2. Johns Hopkins University, 3.Space Science Institute, 4. Space Telescope Science Institute, 5.Université Grenoble Alpes

300.03 – Limits to Creation of Oxygen-RichAtmospheres on Planets in the Outer Reaches ofthe Conventional Habitable ZoneAbundant free oxygen appears to be a requirement for macrofloraand macrofauna. To the best of our knowledge, a generaldiscussion of which habitable planets are conducive to oxygen hasnot taken place. Theories for the rise of oxygen fall into 4categories: (i) It is governed by an intrinsic rate of biologicalinnovation, independent of environmental factors. (ii) It is causedby mantle evolution, probably consequent to secular cooling. (iii)It is caused by hydrogen escape, which irreversibly oxidizes theEarth. (iv) It is Gaia’s response to the brightening Sun, its riseprevented until reduced greenhouse gases were no longer neededto maintain a clement climate. All but the first of these makeimplicit astronomical predictions that can be quantified andmade explicit.

Here we address the third hypothesis. In this hypothesishydrogen escape acts like an hourglass that continues until allrelevant reduced mineral buffers have been oxidized (titrated, asit were) and the surface made safe for O2. The hypothesis predictsthat abundant free O2 will be absent from habitable planets thathave not experienced significant hydrogen escape. Wherehydrogen escape is modest or insignificant, the atmosphere canbe approximated as hydrostatic, which makes assessing radiativecooling by embedded molecules, atoms, and ions such as CO2 andH3+ straightforward. In particular, H2 is efficient at exciting non-LTE CO2 15 micron emission, which makes radiative cooling veryeffective when H2 is abundant. We can therefore map out theregion of phase space in which habitable planets do not losehydrogen, and therefore do not develop O2 atmospheres.

A related matter is the power of radiative cooling by embeddedmolecules to enforce the diffusion limit to hydrogen escape. Thismatter in particular is relevant to addressing the empiricalobservation that rocky planets with thin or negligibleatmospheres are rarely or never bigger than ~1.6 Earth radii.

Author(s): Kevin ZahnleInstitution(s): 1. NASA Ames Research Center

300.04 – Location of refractive boundaries withatmospheric bulk composition in exoplanettransmission spectraIn exoplanet transit spectroscopy, refraction by the planet’satmosphere creates a boundary below which the atmospherecannot be observed. This boundary suppresses atmosphericspectral features with a mean cross-section lower than a ‘surface’cross-section. We show how this ‘surface’ cross-section varieswith the bulk composition of the exoplanet’s atmosphere. For

terrestrial exoplanets, it differs by more than 2 orders ofmagnitude between a pure He and a pure CO atmosphere,resulting in a difference of more than 5 scaleheights in thelocation of the continuum with respect to absorption features inan exoplanet’s effective atmospheric thickness, a fact of potentialimportance in planning JWST observations.

Author(s): Yan Betremieux , Mark R. SwainInstitution(s): 1. JPL/Caltech

300.05 – Observing the Spectra of MEarth andTRAPPIST Planets with JWST During the past two years, nine planets close to Earth in radiushave been discovered around nearby M dwarfs cooler than 3300K. These planets include the 7 planets in the TRAPPIST-1 systemand two planets discovered by the MEarth survey, GJ 1132b andLHS 1140b (Dittmann et al. 2017; Berta-Thompson et al. 2015;Gillon et al. 2017). These planets are the smallest planetsdiscovered to date that will be amenable to atmosphericcharacterization with JWST. They span equilibrium temperaturesfrom ∼130 K to >500 K, and radii from 0.7 to 1.43 Earth radii.Some of these planets orbit as distances potentially amenable tosurface liquid water, though the actual surface temperatures willdepend strongly on the albedo of the planet and the thickness andcomposition of its atmosphere. The stars they orbit also vary inactivity levels, from the quiet LHS 1140b host star to the moreactive TRAPPIST-1 host star. This set of planets will form thetestbed for our first chance to study the diversity of atmospheresaround Earth-sized planets. Here, we will present model spectra of these 9 planets, varyingthe composition and the surface pressure of the atmosphere. Webase our elemental compositions on three outcomes of planetaryatmosphere evolution in our own solar system: Earth, Titan, andVenus. We calculate the molecular compositions in chemicalequilibrium. We present both thermal emission spectra andtransmission spectra for each of these objects, and makepredictions for the observability of these spectra with differentinstrument modes with JWST.

Author(s): Caroline Morley , Laura Kreidberg , ZafarRustamkulov , Tyler D. Robinson , Jonathan J. FortneyInstitution(s): 1. Harvard University, 2. University of CA -Santa Cruz

300.06 – Planet occurrence in the sub-Neptunephotoevaporation desertData from the Kepler mission have shown that sub-Neptunes arethe most common group of currently known exoplanets. Theseplanets have a large range of bulk densities indicative of a groupspanning purely rocky planets to those with substantialhydrogen/helium atmospheres. This diversity may represent apopulation that has been sculpted by photoevaporation, whereinplanets close to their host stars are stripped of their primordialhydrogen/helium atmospheres by impinging stellar X-ray andextreme ultraviolet (XUV) radiation. This would present itselfobservationally as a rarity of ~1.8 - 4 Earth radii planets withorbital periods of ~10 days or less (Lopez et al. 2013). Evidencefor a lack of these planets has been suggested in the Keplerdataset, in the form of an absence of planets between 2.2 and 3.8Earth radii, with incident bolometric fluxes greater than 650times the solar constant (Sanchis-Ojeda et al. 2014, Lundkvist etal. 2016). However, physically, one would expect the desert to bea function of time-integrated XUV flux, which is directlyresponsible for photoevaporation, not present-day bolometricflux. We first examine how time-integrated X-ray flux for a planetat fixed semi-major axis varies for mid M-dwarfs to early F-typestars, with the finding that for an integration time of 5 billionyears, the integrated X-ray flux varies by only ~1 order ofmagnitude, compared to the 2 order of magnitude change instellar luminosity across these star types. We then investigateevidence for a photoevaporation desert by calculating lifetime-integrated X-ray fluxes for the full Kepler sample. We calculateplanet occurrence in this integrated X-ray flux parameter space,

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301 – Titan: Surface and Interior

with the finding that the transition between the desert and non-desert areas may be sharper when compared to the orbital periodparameter space.

Author(s): George McDonald , Laura Kreidberg , EricLopezInstitution(s): 1. Georgia Institute of Technology, 2. HarvardUniversity, 3. NASA Goddard Space Flight Center

301.01 – Origin of Titan’s Nitrogen: Contributionsfrom Organics in the CoreThe origin of Titan’s atmosphere has been a puzzle for decades.The major atmospheric component is N , with a 14N/15N ratio of~168. This ratio is enriched in heavy N compared to the solarratio of 441, but is similar to that measured in cometary comae forNH2 (127), a product of NH3 in the coma. These data have beenused to argue that Titan’s nitrogen was accreted as NH3, andconverted through shock or photochemical processes to N2. Thismodel assumes that N2 and NH3 were the only major reservoirsof nitrogen in the early solar system. To test this model, furtherconstraints on the building blocks of Titan are needed. Comets are thought to preserve the best records of the materialsaccreted to form outer solar system bodies. Measurements ofHalley revealed the presence of an abundant refractory organiccomponent coating cometary dust grains. The organic componentconstituted ~50 wt.% of the dust. This component has since beendetected at other comets by later missions, including Deep Impactand most recently the Rosetta mission. Multiple instruments onRosetta have converged on a dust-to-ice mass ratio at67P/Churyumov-Gerasimenko between 1 and 4, suggesting thatrefractory materials are a significant component. Data from theCometary Secondary Ion Mass Analyser (COSIMA) confirm thatthis refractory material includes abundant organics, with a bulkcomposition similar to insoluble organic matter (IOM) inchondrites. These data suggest that 67P is composed of ~25 wt.%refractory organics. Using these constraints from Rosetta andIOM as an analog material, we find via mass balance calculationsthat organic N represents a third major reservoir of nitrogen inthe early solar system. This third reservoir could have been asource material for Titan’s atmosphere. We present a cosmochemical model for Titan’s atmosphere thatincorporates this third reservoir via heating in a rocky core. Wededuce the relative contributions of N2, NH3, and organic N toTitan’s atmosphere based on N isotopes. We show how thesepredictions are consistent with the atmospheric Ar/N ratiofrom Huygens, and how the available data constrain conditionsand processes in Titan’s interior.

Author(s): Kelly E. Miller , Christopher R. Glein , J. HunterWaiteInstitution(s): 1. Southwest Research Institute

301.02 – Methane, Ethane, and Nitrogen Stabilityon Titan and Other Icy BodiesMany outer solar system bodies are likely to have a combinationof methane, ethane and nitrogen. In particular the lakes of Titanare known to consist of these species. Understanding the past andcurrent stability of these lakes requires characterizing theinteractions of methane and ethane, along with nitrogen, as bothliquids and ices. Our cryogenic laboratory setup allows us toexplore ices down to 30 K through imaging and transmission andRaman spectroscopy. Our recent work has shown that althoughmethane and ethane have similar freezing points, when mixedthey can remain liquid down to 72 K. Concurrently with thefreezing point measurements we acquire transmission or Ramanspectra of these mixtures to understand how the structuralfeatures change with concentration and temperature. Any mixingof these two species together will depress the freezing point of thelake below Titan’s surface temperature, preventing them fromfreezing. We will present new results utilizing our recentlyacquired Raman spectrometer that allow us to explore both theliquid and solid phases of the ternary system of methane, ethaneand nitrogen. In particular we will explore the effect of nitrogenon the eutectic of the methane-ethane system. At high pressure

f d h h l d h

we find that the ternary creates two separate liquid phases.Through spectroscopy we determined the bottom layer to benitrogen rich, and the top layer to be ethane rich. Identifying theeutectic, as well as understanding the liquidus and solidus pointsof combinations of these species, has implications for not only thelakes on the surface of Titan, but also for theevaporation/condensation/cloud cycle in the atmosphere, as wellas the stability of these species on other outer solar system bodies.These results will help interpretation of future observational data,and guide current theoretical models.

Author(s): Jennifer Hanley , Will Grundy , GarrettThompson , Logan Pearce , Shyanne Dustrud , GerrickLindberg , Stephen C. Tegler , Henry G. RoeInstitution(s): 1. Lowell Observatory, 2. Northern ArizonaUniversity, 3. University of Texas, Austin

301.03 – Titan’s mid-latitude surface region fromCassini/VIMS data: Implications on thecompositionWe investigate the surface of Titan using spectro-imaging near-infrared data from the Cassini Visual and Infrared MappingSpectrometer (VIMS). We apply a radiative transfer code to firstdetermine the contributions of atmospheric haze to the Titanspectrum and then derive the surface albedo (Solomonidou et al.2014; 2016). We focus here on the geological major unitsidentified in Lopes et al. (2010, 2016), Malaska et al. (2016) andRadebaugh et al. (2016) from Synthetic Aperture Radar (SAR),data including mountains, different types of plains, labyrinths,impact craters, dune fields, and alluvial fans. We find that allregions classified as being the same geomorphological unit inSAR exhibit a coherent spectral response after the VIMS dataanalysis, thus suggesting a good correlation in the classificationbetween SAR and VIMS. The Huygens landing site appears to becompositionally similar to one type of plains unit (variableplains), suggesting similar plain formation mechanisms. We havesub-categorized the VIMS data into three albedo categories (high,medium, low). By matching the extracted albedos with candidatematerials for Titan’s surface (GhoSST database), we find that allregions of interest fall into one out of three main types of majorcandidate constituents: water ice, tholin-like material, or anunknown, very dark material. This suggests that Titan’s surface ispossibly dominated by tholin-like material and a very darkunknown (most likely organic) material, and that most of thesurface is covered by atmospheric/organic deposits. Water ice isalso present at a number of regions as major constituent atlatitudes higher than 30N and 30S. The surface albedodifferences and similarities among the various geomorphologicalunits constrain the implications for the geological processes thatgovern Titan’s surface and interior (e.g. aeolian, fluvial,sedimentary, lacustrine, cryovolcanic, tectonic). References: Lopes et al.: Icarus, 205, 540-558, 2010; Lopes et al.:Icarus, 270, 162-182, 2016; Malaska et al.: Icarus, 270, 130-161,2016; [4] Solomonidou et al.: JGR, 119, 1729-1747, 2014; [6]Solomonidou et al.: Icarus, 270, 85-99, 2016; [7] Schmitt et al.:GhoSST database (ghosst.osug.fr).

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Author(s): Anezina Solomonidou , Athena Coustenis ,Rosaly M.C Lopes , Michael Malaska , Sebastien Rodriguez ,Pierre Drossart , Charles Elachi , Bernard Schmitt , SylvainPhilippe , Michael A. Janssen , Mathieu Hirtzig , Stephen D.Wall , Kenneth J. Lawrence , Nicolas Altobelli , EmmanuelBratsolis , Jani Radebaugh , Katrin Stephan , Robert HBrown , Stephane Le Mouélic , Alice Le Gall , EdwardVillanueva , Anthony Bloom , Olivier Witasse , ChristosMatsoukas , Ashley SchoenfeldInstitution(s): 1. Department of Earth, Planetary, and SpaceSciences, University of Calilfornia, 2. Department of GeologicalSciences, Brigham Young University, 3. Department of Physics,University of Athens, 4. European Space Agency (ESA),European Space Astronomy Centre (ESAC), 5. European SpaceAgency (ESA), European Space Research and Technology Centre(ESTEC), 6. Fondation “La main à la pâte”, 7. Institut dePlanétologie et d’Astrophysique de Grenoble, 8. Institute ofPlanetary Research, DLR, 9. Jet Propulsion Laboratory/Caltech,10. KTH-Royal Institute of Technology, 11. Laboratoire AIM,Université Paris Diderot, Paris 7/CNRS/CEA-Saclay,DSM/IRFU/SAp, 12. Laboratoire Atmosphères, Milieux,Observations Spatiales (LATMOS-UVSQ), 13. LESIA -Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, 14. Lunar and Planetary Laboratory, University ofArizona, 15. Université de Nantes, Laboratoire de Planétologie etGéodynamique

301.04 – Compositional Variations of Titan'sImpact Craters Indicates Active Surface ErosionTitan’s crust is assumed to be mostly water-ice. However, thesurface composition is not well constrained due to its thickatmosphere. Based on infrared and radiometry data, the surfaceappears enriched in organics, with only few areas showingevidence of exposed water-ice. Regions of water-ice enrichmentinclude the rims and ejecta blankets of impact craters. This studyutilizes these geologic features to examine compositionalvariations across Titan’s surface, and their subsequentmodification due to erosional processes.

Sixteen craters and their ejecta blankets were mapped on aCassini RADAR mosaic. These features were selected becausethey are some of the best preserved craters on Titan. Compositionwas inferred from Cassini’s Visual and Infrared MappingSpectrometer (VIMS) and 2-cm emissivity data from the Cassiniradiometer. With VIMS, different compositional units wereinferred from their reflectivity at specific wavelengths. With theemissivity data, high values suggest more organic-rich material,while lower values indicate strong volume scattering. Areas withlow emissivity have been interpreted to be water-ice rich, aswater-ice is a favorable medium for volume scattering.

Results show fresher, well-preserved craters in the dunes regionshave a low emissivity indicative of water-ice, and a VIMSspectrum consistent with an unknown material, possibly amixture of water-ice and organics. As these craters erode overtime, the VIMS spectra remain the same but the emissivityincreases. Well-preserved craters in the mid-latitude plains showVIMS spectra and emissivity values consistent with water-ice. Asthese plain craters degrade, the VIMS spectra remain the same,but the emissivity increases. The differing VIMS signaturessuggest more mixing with organics during the cratering event inthe organic-rich dunes than the plains. The changes in emissivityover time are consistent with organic infilling of subsurfacefractures in both regions, with limited surficial alteration. Theseresults support the idea that compositional variations in Titan’simpact craters are related primarily to erosion and infilling, andto a lesser extent, local variations in the overlying organicmaterial of the pre-impact substrate.

Author(s): Alyssa Werynski , Catherine Neish , Alice LeGall , Michael A. JanssenInstitution(s): 1. JPL, 2. University of Western Ontario, 3.UVSQ Université Paris-Saclay

301.05 – Pond Hockey on Whitmore Lacus: theFormation of Ponds and Ethane Ice DepositsFollowing Storm Events on TitanCassini ISS observations reveled regions, later identified astopographic low spots (Soderblom et al. 2014, DPS) on Saturn’smoon Titan become significantly darker (lower albedo) followingstorm events (Turtle et al. 2009, GRL; 2011, Science), suggestingpools of liquid hydrocarbon mixtures (predominantly methane-ethane-nitrogen). However, these dark ponds then significantlybrighten (higher albedo relative to pre-storm albedo), beforefading to their pre-storm albedos (Barnes et al. 2013 Planet. Sci;Soderblom et al. 2014, DPS). We interpret these data to be theresult of ethane ice formation, which cools from evaporation ofmethane. The formation of ethane ices results from a unique sequence ofthermophysical processes. Initially, the methane in the ternarymixture evaporates, cooling the pond. Nitrogen, dissolvedprimarily in the methane, exsolves, further cooling the liquid.However, because nitrogen is significantly more soluble in coolermethane-hydrocarbon mixtures, the relative concentration ofnitrogen in the solution increases as it cools. This increasednitrogen fraction increases the density of the pond, as nitrogen issignificantly more dense thane methane or ethane (pure ethane’sdensity is intermediate to that of methane and nitrogen). Ataround ~85 K the mixture is as dense as pure liquid ethane. Thus,further evaporative methane loss and cooling at the pond’ssurface leads to a chemical stratification, with an increasinglyethane rich epilimnion (surface layer) overlying a methane richhypolimnion (subsurface layer). Further evaporation of methane from the ethane-rich epilimniondrives its temperature and composition toward the methane-ethane-nitrogen liquidus curve, causing pure ethane ice toprecipitate out of solution and settle to the bottom of the pool.This settling would obscure the ethane ice from Cassini VIMS andISS, which would instead continue to appear as a dark pond onthe surface. As the ethane precipitates out completely, a binarymethane-nitrogen liquid mixture remains. Eventually, thisresidual liquid evaporates away, exposing the submerged ethaneice, which Cassini VIMS and ISS would observe as a dramaticbrightening of the surface, consistent with observations.

Author(s): Jordan Steckloff , Jason M. SoderblomInstitution(s): 1. Massachusetts Institute of Technology

301.06 – Creating the best Global Mosaic of Titan'sSurface Albedo using Cassini ImagesWe have conducted a photometric analysis of the set of Cassini'sImaging Science Subsystem (ISS) images of Titan's surface at 938nm. The images show Titan's haze and surface features throughthe haze. At scales < 5 km, the contrast of surface features issubdued by a factor of ~60 which makes them undetectable withstandard methods. Our new photometric method accounts for spatial and temporalatmospheric and instrumental variations through a model with 16parameters, determined by a least square fit to the data. It wasmade possible by recent progress in modeling Titan's hazethrough accurate radiative transfer models. Our new approachgives calibrated surface albedos, unlike previous work. It alsoallows combination of all images of the same terrain, about 20times more images than previously processed, increasing thesignal-to-noise 4-5 times, which is critical to retrieving smallfeatures. In the Adiri region, our approach increased the effective spatialresolution by a factor of 4-5. Statistical analysis finds outliers inthe data set due to surface changes and occasional clouds. Wefound albedo changes where surface changes were previouslyreported. We found terrains with similar albedo that have distinctphase functions indicating possible variations of surfaceroughness. We plan to combine all suitable images into a globalmosaic of high spatial resolution.

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302 – Trojan Asteroids

This effort is leading to new science results in three areas:

(1) We can detect smaller temporal variations on Titan's surface,related to activity such as methane rainfall (and subsequentdryout), potential new evaporite deposits, shrinking andexpanding lakes, and perhaps some new discoveries.

(2) Correlation of observations by RADAR, VIMS, and DISR tothe improved ISS global map facilitates interpretation of theglobal distributions of key terrains such as dark dunes, lakes,large river channels, and tectonic structures.

(3) The ISS map with quantitative albedo values at 938 nmprovides a direct compositional constraint, compared to VIMSdata, for improved mapping of compositional variations. We alsoplan to create a global mosaic at 750 nm to extend the spectralcoverage. This work was supported by the Cassini project.

Author(s): Erich Karkoschka , Alfred McEwen , JasonPerryInstitution(s): 1. University of Arizona

302.01 – The growing population of dark objectsthat have high emissivity contrastAt visible and near-infrared wavelengths dark asteroids, Trojanasteroids, and cometary nuclei are largely featureless and are thuscharacterized and compared primarily based on differences intheir spectral slopes. In contrast, in the mid-infrared a series oftelescopic observations (e.g., ISO, Spitzer, SOFIA) have revealedsubtle but clear silicate emissions in the 9-11 µm region. For themost part, these features are very low in spectral contrast (~5%).However, Emery et al. (2006) showed that Spitzer spectra ofTrojan asteroids can have much larger spectral contrast (~10-15%) akin to cometary comae and dust in planetary disks. Similarhigh-contrast silicate features were found by Kelley et al. (2017)in Spitzer spectra of bare cometary nuclei. Together these resultssuggest the presence of fine grained and likely highly poroussurfaces (Emery et al., 2006; Vernazza et al., 2012). Here wereport on archival spectroscopy with the Spitzer Space Telescopethat shows two mainbelt asteroids 267 Tirza (D-type; 55 kmdiameter) and 1284 Lativa (T/L-type; 40 km diameter) also havestrong 10 µm silicate emission features. Moreover, the shapes oftheir silicate features match those of the other Trojan D-types; thebest agreement is with 1172 Aneas. If high porosity is responsiblefor the enhanced spectra contrast in these objects, that porositymust now be explained for objects over an extended range ofheliocentric distances, sizes, and that likely have differentaccretionary and impact histories.

Author(s): Jessica M. Sunshine , Michael S. P. Kelley ,Margaret M. McAdamInstitution(s): 1. University of Maryland

302.02 – Albedos of Jovian Trojans, Hildas andCentaursWe present distributions of optical V band albedos for samples ofouter solar system minor bodies including Centaurs, JovianTrojans and Hildas. Diameters come almost entirely from theNEOWISE catalog (Mainzer etal 2016- Planetary Data System).Optical photometry (H values) for about 2/3 of the approximately2700 objects studied are from PanStarrrs (Veres et al 2015 Icarus261, 34). The PanStarrs optical photometry is supplemented by Hvalues from JPL Horizons (corrected to be on the samephotometric system as the PanStarrs data) for the objects in theNEOWISE catalog that are not in the PanStarrs catalog. Wecompare the albedo distributions of various pairs of subsamplesusing the nonparametric Wilcoxon rank sum test. Examples ofpotentially interesting comparisons include: (1) The Hildas are15-25% darker than the Trojans at a very high level of statisticalsignificance. If the Hildas and Trojans started out with similarsurfaces, the Hildas may have darkened due to the effects ofgardening as they pass through zone III of the asteroid belt. (2)The median albedo of the gray Centaurs lies between that of theL4 and L5 Trojan groups (3) The median L5 Trojan cloud albedois about 10% darker than that of the L4 cloud at a high level ofsignificance. However, the modes of the L4 and L5 albedodistributions are very similar, perhaps indicating the presence ofa distinct brighter component in the L4 cloud that is not found inthe L5 cloud.

Author(s): William Romanishin , Stephen C. TeglerInstitution(s): 1. Northern Arizona University, 2. Univ. ofOklahoma

302.03 – Candidate Binary Trojan and HildaAsteroids from Rotational Light CurvesJovian Trojans (hereafter, Trojans) are asteroids in stable orbitsat Jupiter's L4 and L5 Lagrange points, and Hilda asteroids areinwards of the Trojans in 3:2 mean-motion resonance withJupiter. Due to their special dynamical properties,observationally constraining the formation location anddynamical histories of Trojans and HIldas offers key input forgiant planet migration models. A fundamental parameter inassessing formation location is the bulk density - with low-densityobjects associated with an ice-rich formation environment in theouter solar system and high-density objects typically linked to thewarmer inner solar system. Bulk density can only be directlymeasured during a close fly-by or by determining the mutualorbits of binary asteroid systems. With the aim of determiningdensities for a statistically significant sample of Trojans andHildas, we are undertaking an observational campaign to confirmand characterize candidate binary asteroids published in Sonnettet al. (2015). These objects were flagged as binary candidatesbecause their large NEOWISE brightness variations imply shapesso elongated that they are not likely explained by a singularequilibrium rubble pile and instead may be two elongated,gravitationally bound asteroids. We are obtaining denselysampled rotational light curves of these possible binaries tosearch for light curve features diagnostic of binarity and todetermine the orbital properties of any confirmed binary systemsby modeling the light curve. We compare the We present anupdate on this follow-up campaign and comment on future steps.

Author(s): Sarah M. Sonnett , Amy K. Mainzer , TommyGrav , Joseph R. Masiero , James M Bauer , Emily A. KramerInstitution(s): 1. Jet Propulsion Laboratory / CaliforniaInstitute of Technology, 2. Planetary Science Institute, 3.University of Maryland

302.04 – Estimating Mass Parameters of DoublySynchronous Binary AsteroidsThe non-spherical mass distributions of binary asteroid systemslead to coupled mutual gravitational forces and torques.Observations of the coupled attitude and orbital dynamics can beleveraged to provide information about the mass parameters ofthe binary system. The full 3-dimensional motion has 9 degrees offreedom, and coupled dynamics require the use of numericalinvestigation only. In the current study we simplify the system toa planar ellipsoid-ellipsoid binary system in a doublysynchronous orbit. Three modes are identified for the system,which has 4 degrees of freedom, with one degree of freedomcorresponding to an ignorable coordinate. The three modescorrespond to the three major librational modes of the systemwhen it is in a doubly synchronous orbit. The linearized periods ofeach mode are a function of the mass parameters of the twoasteroids, enabling measurement of these parameters based onobservations of the librational motion. Here we implementestimation techniques to evaluate the capabilities of this massmeasurement method. We apply this methodology to the Trojanbinary asteroid system 617 Patroclus and Menoetius (1906 VY),

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the final flyby target of the recently announced LUCY Discoverymission. This system is of interest because a stellar occultationcampaign of the Patroclus and Menoetius system has suggestedthat the asteroids are similarly sized oblate ellipsoids moving in adoubly-synchronous orbit, making the system an ideal test forthis investigation. A number of missed observations during thecampaign also suggested the possibility of a crater on thesouthern limb of Menoetius, the presence of which could beevaluated by our mass estimation method. This presentation willreview the methodology and potential accuracy of our approachin addition to evaluating how the dynamical coupling can be usedto help understand light curve and stellar occultationobservations for librating binary systems.

Author(s): Alex Davis , Daniel J. ScheeresInstitution(s): 1. University of Colorado at Boulder

302.05 – Population control of Martian Trojans bythe Yarkovsky & YORP effectsMars is the only terrestrial planet supporting a stable populationof Trojan asteroids. One, (5261) Eureka, has a family of smallerasteroids of similar composition (Borisov et al, 2017; Polishook etal, 2017) that likely separated from Eureka within the last 1 Gyr(Ćuk et al, 2015). Two other Trojans, (101429) 1998 VF and(121514) 1999 UJ , of similar size and on similar orbits to Eureka,are not associated with families of asteroids, begging the questionof what makes Eureka special.

The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect mayhave formed the Eureka family (Christou, 2013; Ćuk et al, 2015)by the spinning off of ``YORPlets’’, a mechanism also responsiblefor close orbital pairs of small Main Belt asteroids (Pravec et al,2010). Eureka’s fast rotation rate (P=2.69 hr; Koehn et al, 2014),right at the so-called ``spin barrier’’ (Warner et al, 2009),apparently supports this.

We obtained photometry of 101429 and 121514 to find out theirrotation periods. We find an unusually long, ∼50 hr period for121514; the asteroid may be in a ``tumbling’’ rotational state thatinhibits YOPRlet production. On the other hand, the faster (P=7.7hr) rotation we obtain for 101429 does not preclude it fromhaving been spun up to the rotational fission limit during themost recent 10s of Myr.

Instead, 101429’s location near a secular resonance (Scholl et al,2005) may lead to rapid loss of any YORPlet asteroids. Indeed,test particles started at 101429’s orbit and evolving under theYarkovsky effect escape within a few hundred Myr, several timesfaster than particles started near Eureka. We conclude that thestability enjoyed by asteroids in Eureka’s orbital vicinity,combined with the ability to readily populate that vicinity withnew asteroids, are likely responsible for Eureka’s status as theonly Martian Trojan with a family.

Author(s): Apostolos Christou , Galin Borisov , Seth AJacobson , Francois Colas , Aldo dell’Oro , Alberto Cellino ,Stefano BagnuloInstitution(s): 1. Department of Earth and Planetary Sciences,Northwestern University, 2. Armagh Observatory andPlanetarium, 3. IMCCE, Observatoire de Paris, 4. OsservatorioAstrofisico di Arcetri, 5. Osservatorio Astronomico di Torino

302.06D – The Trojan-Hilda-KBO connection: Anobservational test of solar system evolution modelsOver the past few decades, many theories have been devised toexplain the observed solar system architecture. The currentparadigm posits that a significant reorganization of the outerSolar System occurred after the end of planet formation.Specifically, it is hypothesized that Jupiter and Saturn crossed amutual mean motion resonance, leading to a chaotic expansion ofthe ice giants’ orbits that disrupted the large population ofplanetesimals situated further out. While the majority of thesebodies were ejected from the Solar System, a fraction of themwere retained as the present-day Kuiper Belt, while others werescattered inward and captured into resonances with Jupiter tobecome the Trojans and Hildas. Dynamical instability modelsinvariably predict that Trojans, Hildas, and Kuiper Belt objects(KBOs) were sourced from the same primordial body of outersolar system planetesimals. Therefore, comparison of these minorbody populations serves as one of the few available observationaltests of our present understanding of solar system evolution. We present the results of a series of studies aimed at synthesizinga detailed picture of Trojans and related asteroid populations. Bycombining analyses of archival data with new photometricsurveys, we have derived the first debiased color distributions ofTrojans and KBOs and extended/refined our knowledge of theirrespective size distributions. In addition, we have explored thepeculiar color bimodality attested in the Trojans, Hildas, andKBOs, which indicates the presence of two sub-populations. Aspart of our continuing efforts to characterize the surfacecomposition of these bodies, we have also obtained new near-infrared spectra of Hildas for comparison with previouslypublished spectra of Trojans covering the same wavelengthregion. We have utilized the full body of observations to formulatehypotheses regarding the formation, composition, anddynamical/chemical evolution of the primordial outer solarsystem planetesimals, with special attention given to explainingthe color bimodality and size distribution shapes. Our results laythe groundwork for future studies with next-generationinstruments and ultimately, the Trojan flyby mission Lucy.

Author(s): Ian Wong , Michael BrownInstitution(s): 1. Caltech

303.01 – Constraining the interior density profileof a Jovian planet from precision gravity field dataThe external gravity field of a planetary body is determined by thedistribution of mass in its interior. Therefore, a measurement ofthe external field, properly interpreted, tells us about the interiordensity profile, ρ(r), which in turn can be used to constrain thecomposition in the interior and thereby learn about the formationmechanism of the planet. Planetary gravity fields are usuallydescribed by the coefficients in an expansion of the gravitationalpotential. Recently, high precision measurements of thesecoefficients for Jupiter and Saturn have been made by the radioscience instruments on the Juno and Cassini spacecraft,respectively.

The resulting coefficients come with an associated uncertainty.And while the task of matching a given density profile with agiven set of gravity coefficients is relatively straightforward, thequestion of how best to account for the uncertainty is not. Inessentially all prior work on matching models to gravity field

data, inferences about planetary structure have rested onimperfect knowledge of the H/He equation of state and on theassumption of an adiabatic interior. Here we wish to vastlyexpand the phase space of such calculations. We present aframework for describing all the possible interior densitystructures of a Jovian planet, constrained only by a given set ofgravity coefficients and their associated uncertainties. Ourapproach is statistical. We produce a random sample of ρ(a)curves drawn from the underlying (and unknown) probabilitydistribution of all curves, where ρ is the density on an interiorlevel surface with equatorial radius a. Since the resulting set ofdensity curves is a random sample, that is, curves appear withfrequency proportional to the likelihood of their being consistentwith the measured gravity, we can compute probabilitydistributions for any quantity that is a function of ρ, such ascentral pressure, oblateness, core mass and radius, etc. Ourapproach is also bayesian, in that it can utilize any priorassumptions about the planet's interior, as necessary, withoutbeing overly constrained by them.

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We demonstrate this approach with a sample of Jupiter interiormodels based on recent Juno data and discuss prospects forSaturn.

Author(s): Naor Movshovitz , Jonathan J. Fortney , RavitHelled , William B. Hubbard , Daniel Thorngren , ChrisMankovich , Sean Wahl , Burkhard Militzer , Daniele DuranteInstitution(s): 1. Sapienza University of Rome, 2. University ofArizona, 3. University of California, Berkeley , 4. University ofCalifornia, Santa Cruz, 5. University of Zurich

303.02 – An Explanation of Jupiter's EquatoriallySymmetric Gravitational Field using a Four-layer,Non-spheroidal Model with Zonal FlowThe structure/amplitude of the Jovian equatorially symmetricgravitational field is affected by both rotational distortion and thefast equatorially symmetric zonal flow. We construct a fully self-consistent, four-layer, non-spheroidal (i.e, the shape is irregular)model of Jupiter that comprises an inner core, a metallic region,an outer molecular envelope and a thin transition layer betweenthe metallic and molecular regions. While the core is assumed tohave a uniform density, three different equations of state areadopted for the metallic, molecular and transition regions. Wesolve the governing equations via a perturbation approach. Theleading-order problem accounts for the full effect of rotationaldistortion, and determines the density, size and shape of the core,the location and thickness of the transition layer, and the shape ofthe 1-bar pressure level; it also produces the mass, the equatorialand polar radii of Jupiter, and the even zonal gravitationalcoefficients caused by the rotational distortion. The next-orderproblem determines the corrections caused by the zonal flowwhich is assumed to be confined within the molecular envelopeand on cylinders parallel to the rotation axis. Our model providesthe total even gravitational coefficients that can be compared withthose acquired by the Juno spacecraft.

Author(s): Dali Kong , Keke Zhang , Gerald Schubert , JohnAndersonInstitution(s): 1. Jet Propulsion Laboratory, 2. ShanghaiAstronomical Observatory, Chinese Academy of Sciences, 3.University of California, Los Angeles, 4. University of Exeter

303.03 – Inferring the depth of the atmosphericflows on Jupiter from the Juno gravitymeasurementsFor the past year the Juno spacecraft has been in orbit aroundJupiter, performing close flybys of the planet and measuring thegravity field to very high precision. These gravity measurementscan be used to infer the depth of Jupiter's observed cloud-levelwinds, and decipher the possible internal flows within the planet.In light of the first few Juno orbits we discuss the gravitymeasurements and present initial results for the depth andvertical structure of the atmospheric flows of Jupiter. Particularlywe focus on the odd gravity harmonics, which reflect asymmetriesbetween the northern and southern hemispheres and thereforeare a pure signature of the dynamics with no contribution fromthe static planet. In order to invert the gravity measurements intoflow fields we use an adjoint based inverse model at several levelsof complexity for the vertical and meridional structure. As theaccuracy of the gravity measurement has improved by two ordersof magnitude compared to pre-Juno knowledge, the effectiveuncertainty for the static even harmonics now comes from thecontribution of the flow field to the gravity spectrum. We showhow this narrows the range of possible interior structure modelsand the implications for the core mass. Implications regarding thephysics governing the atmospheric and internal flows on Jupiterare discussed.

Author(s): Yohai Kaspi , Eli Galanti , William B.Hubbard , David J. Stevenson , Luciano Iess , Tristan Guillot ,Jeremy Bloxham , Hao Cao , Daniele Durante , WilliamFolkner , Ravit Helled , Andrew P. Ingersoll , Jonathan I.Lunine , Yamila Miguel , Burkhard Militzer , Marzia Parisi ,Sean Wahl , John E.P. Connerney , Steven Levin , Scott J.BoltonInstitution(s): 1. Berkeley , 2. California Institute ofTechnology, 3. Cornell University, 4. Harvard University, 5.JPL/Caltech, 6. LaSapienza University, 7. NASA, 8. Obs. de LaCote D' Azur, 9. Southwest Research Institute, 10. University ofArizona, 11. University of Zurich, 12. Weizmann Institute ofScience

303.04 – Excitation Mechanisms for JovianSeismic ModesRecent (2011) results from the Nice Observatory indicate theexistence of global seismic modes on Jupiter in the frequencyrange between 0.7 and 1.5mHz with amplitudes of tens of cm/s.Currently, the driving force behind these modes is a mystery; themeasured amplitudes were much larger than anticipated based ontheory analogous to helioseismology (that is, turbulent convectionas a source of stochastic excitation). One of the most promisinghypotheses is that these modes are driven by Jovian storms. Thiswork constructs a framework to analytically model the expectedequilibrium normal mode amplitudes arising from convectivecolumns in storms. We also place rough constraints of Jupiter'sseismic modal quality factor. Using this model, neither meteorstrikes, turbulent convection, nor water storms can feasibly excitethe order of magnitude of observed amplitudes. Next wespeculate about the potential role of rock storms deeper inJupiter's atmosphere, because the rock storms' expected energyscales make them promising candidates to be the chief source ofexcitation for Jovian seismic modes, based on simple scalingarguments. Finally we suggest a predicted power spectrum forfrequencies which have not yet been observed based on ourfindings, and supply some commentary on potential applicationsto Juno, Saturn, and future missions to Uranus and Neptune.

Author(s): Stephen Markham , David J. StevensonInstitution(s): 1. California Institute of Technology

303.05 – Deep Zonal Flow and Time Variation ofJupiter’s Magnetic FieldAll four giant planets in the Solar System feature zonal flows onthe order of 100 m/s in the cloud deck, and large-scale intrinsicmagnetic fields on the order of 1 Gauss near the surface. Thevertical structure of the zonal flows remains obscure. The end-member scenarios are shallow flows confined in the radiativeatmosphere and deep flows throughout the entire planet. Theelectrical conductivity increases rapidly yet smoothly as afunction of depth inside Jupiter and Saturn. Deep zonal flows willadvect the non-axisymmetric component of the magnetic field, atdepth with even modest electrical conductivity, and create timevariations in the magnetic field. The observed time variations of the geomagnetic field has beenused to derive surface flows of the Earth’s outer core. The sameprinciple applies to Jupiter, however, the connection between thetime variation of the magnetic field (dB/dt) and deep zonal flow(Uphi) at Jupiter is not well understood due to strong radialvariation of electrical conductivity. Here we perform aquantitative analysis of the connection between dB/dt and Uphifor Jupiter adopting realistic interior electrical conductivityprofile, taking the likely presence of alkali metals into account.This provides a tool to translate expected measurement of thetime variation of Jupiter’s magnetic field to deep zonal flows. Weshow that the current upper limit on the dipole drift rate ofJupiter (3 degrees per 20 years) is compatible with 10 m/s zonalflows with < 500 km vertical scale height below 0.972 Rj. Wefurther demonstrate that fast drift of resolved magnetic features(e.g. magnetic spots) at Jupiter is a possibility.

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304 – Titan: Atmosphere

Author(s): Hao Cao , David J. StevensonInstitution(s): 1. Caltech

303.06 – Saturn's Internal Structure: A Viewthrough its Natural SeismographSaturn's nonradial oscillations perturb the orbits of ring particles.The C ring is fortuitous in that it spans several resonances withSaturn's fundamental acoustic (f-) modes, and its moderateoptical depth allows the characterization of wave features usingstellar occultations. The growing set of C-ring waves with precisepattern frequencies and azimuthal order m measured fromCassini stellar occultations (Hedman & Nicholson 2013, 2014;French et al. 2016) provides new constraints on Saturn's internalstructure, with the potential to resolve long-standing questionsabout the planet's distribution of helium and heavier elements, itsmeans of internal energy transport, and its rotation state.

We construct Saturn interior models and calculate modeeigenfrequencies, mapping the planet mode frequencies toresonant locations in the rings to compare with the locations ofobserved spiral density and vertical bending waves in the C ring.While spiral density waves at low azimuthal order (m=2-3)appear strongly affected by resonant coupling between f-modesand deep g-modes (Fuller 2014), the locations of waves withhigher azimuthal order can be fit reasonably well with a spectrumof pure f-modes for Saturn models with adiabatic envelopes andrealistic equations of state. In particular, four observed bendingwaves (Nicholson et al., DPS 2016) align with outer verticalresonances for non-sectoral (m≠l) Saturn f-modes of relativelyhigh angular degree, and we present preliminary identificationsof these. We assess the range of resonance locations in the C andD rings allowed for the spectrum of f-modes given gravity fieldconstraints and discuss what role a realistic helium distribution inthe planet might play.

Author(s): Christopher Mankovich , Mark S. Marley ,Jonathan J. Fortney , Naor MovshovitzInstitution(s): 1. NASA Ames Research Center, 2. University ofCalifornia Santa Cruz

303.07 – Cassini Can Constrain Tidal Dissipation inSaturn

Tidal dissipation inside giant planets is important for the orbitalevolution of their natural satellites. It is conventionally treated byparameterized equilibrium tidal theory, in which the tidal torquedeclines rapidly with distance, and orbital expansion was faster inthe past. However, Lainey et al. (2017) find that some Saturniansatellites are currently migrating outward faster than predicted byequilibrium tidal theory. Reso- nance locking between satellitesand internal oscillations of Saturn, proposed by Fuller et al.(2016), naturally matches the observed migration rates. Here, weshow that the resonance locking theory predicts dynamical tidalperturbations to Saturn’s gravitational field in addition to thoseproduced by equilibrium tidal bulges. We show that theseperturbations can likely be detected during Cassini’s proximalorbits if migration of satellites results from resonant gravitymodes, but will likely be undetectable if migration results frominertial wave attractors or dissipation of the equilibrium tide.Additionally, we show that the detection of gravity modes wouldplace constraints on the size of the hypothetical stably stratifiedregion in Saturn.

Author(s): Jing Luan , Jim Fuller , Eliot QuataertInstitution(s): 1. Caltech, 2. University of California atBerkeley

303.08 – Dynamo Scaling Laws for Uranus andNeptune: The Role of Convective Shell Thicknesson DipolarityPrevious dynamo scaling law studies (Christensen and Aubert,2006) have demonstrated that the morphology of a planet’smagnetic field is determined by the local Rossby number (Ro_l):

a non-dimensional diagnostic variable that quantifies the ratio ofinertial forces to Coriolis forces on the average length scale of theflow. Dynamos with Ro_l <~ 0.1 produce dipolar dominatedmagnetic fields whereas dynamos with Ro_l >~ 0.1 producemultipolar magnetic fields. Scaling studies have also determinedthe dependence of the local Rossby number on non-dimensionalparameters governing the system - specifically the Ekman,Prandtl, magnetic Prandtl and flux-based Rayleigh numbers(Olson and Christensen, 2006). When these scaling laws are applied to the planets, it appears thatUranus and Neptune should have dipole-dominated fields,contrary to observations. However, those scaling laws werederived using the specific convective shell thickness of the Earth’score. Here we investigate the role of convective shell thickness ondynamo scaling laws. We find that the local Rossby numberdepends exponentially on the convective shell thickness.Including this new dependence on convective shell thickness, wefind that the dynamo scaling laws now predict that Uranus andNeptune reside deeply in the multipolar regime, thereby resolvingthe previous contradiction with observations.

Author(s): Sabine Stanley , Bob Yunsheng TianInstitution(s): 1. Johns Hopkins University, 2. University ofToronto

303.09D – Using Jovian Oscillations to ConstrainInteriors and Understanding Why They ExistPlanetary oscillations are excellent tools for probing unknownproperties about their respective interiors, particularly quantitiesthat pertain to formation theories such as core size. Recently,there have been very suggestive indications of detections ofoscillations on Jupiter, and several have been confirmed onSaturn. Saturn is a unique case for seismic exploration as its ringstructures act as a global seismograph. The seismic signatures inthe rings provide information on the frequency of oscillations,which we can exploit to probe Saturn’s interior. Here we describea comprehensive approach to detecting and utilizing oscillationsto constrain the interiors of Jupiter and Saturn. Theaforementioned Saturnian oscillations have already been detectedvia spiral density structures in the C ring as inferred from Cassinioccultation data. Jovian oscillations will be detected in theupcoming years with a global network of Doppler imagingspectrometers established by the JIVE in NM (Jovian InteriorsVelocimetry Experiment) and JOVIAL (Jovian Oscillationsthrough radial Velocimetry ImAging observations at severalLongitudes) groups. This network of instrumentation is optimizedfor observing Jovian oscillations including a high duty cycleallowing for limited temporal interruptions and thus highprecision frequency data. In addition, unlike most oscillatingbodies, we are unaware of the excitation mechanism behindJovian oscillations. Therefore, we also explore mode excitationmechanisms that can excite Jupiter’s oscillations, primarily moistconvection in the atmosphere. We will show under whatconditions moist convection can be responsible for modeexcitation and what this reveals about thunderstorm density onJupiter. In regards to Saturn, we apply adapted helioseismicconcepts to understand its fundamental mode (f-mode)oscillations and develop the framework for Jupiter for once itsmode data becomes available. We will show initial inversionresults for Saturn and what we can interpret about its interiorstructure. By developing this strategy and later applying it toJupiter, we can complement results from Juno gravity data andwork towards creating an accurate and comprehensive interiormodel of Jupiter.

Author(s): Ethan DederickInstitution(s): 1. New Mexico State UniversityContributing team(s): JIVE (Jovian Interiors VelocimetryExperiment) in NM, JOVIAL (Jovian Oscillations through radialVelocimetry ImAging observations at several Longitudes

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3 4 p304.01 – The impact of runoff and surfacehydrology on Titan's climateTitan’s surface liquid distribution has been shown by generalcirculation models (GCMs) to greatly influence the hydrologicalcycle. Simulations from the Titan Atmospheric Model (TAM) withimposed polar methane “wetlands” reservoirs realisticallyproduce many observed features of Titan’s atmosphere, whereas“aquaplanet” simulations with a global methane ocean are not assuccessful. In addition, wetlands simulations, unlike aquaplanetsimulations, demonstrate strong correlations between extremerainfall behavior and observed geomorphic features, indicatingthe influential role of precipitation in shaping Titan’s surface. Thewetlands configuration is, in part, motivated by Titan’s large-scaletopography featuring low-latitude highlands and high-latitudelowlands, with the implication being that methane mayconcentrate in the high-latitude lowlands by way of runoff andsubsurface flow. However, the extent to which topographycontrols the surface liquid distribution and thus impacts theglobal hydrological cycle by driving surface and subsurface flow isunclear. Here we present TAM simulations wherein the imposedwetlands reservoirs are replaced by a surface runoff scheme thatallows surface liquid to self-consistently redistribute under theinfluence of topography. To isolate the singular impact of surfacerunoff on Titan’s climatology, we run simulations withoutparameterizations of subsurface flow and topography-atmosphereinteractions. We discuss the impact of surface runoff on thesurface liquid distribution over seasonal timescales and comparethe resulting hydrological cycle to observed cloud and surfacefeatures, as well as to the hydrological cycles of the TAM wetlandsand aquaplanet simulations. While still idealized, this morerealistic representation of Titan’s hydrology provides new insightinto the complex interaction between Titan’s atmosphere andsurface, demonstrates the influence of surface runoff on Titan’sglobal climate, and lays the groundwork for further surfacehydrology developments in Titan GCMs.

Author(s): Sean Faulk , Juan Lora , Jonathan MitchellInstitution(s): 1. University of California Los Angeles

304.02 – The influence of topography on Titan’satmospheric circulation and hydrologic cycleTitan’s atmospheric circulation is a dominant driver of the globalmethane hydrologic cycle—producing weather and a seasonalclimate cycle—while interactions between the surface and thetroposphere strongly constrain regional climates, and contributeto the differentiation between Titan’s low latitude deserts andhigh latitude lake districts. Yet the influence of surfacetopography on the atmospheric circulation has only been studiedin a few instances, and no published work has investigated thecoupling between topographical forcing and Titan’s hydrologiccycle. In this work, we examine the impacts of global topographyin the Titan Atmospheric Model (TAM), which includes a robustrepresentation of the methane cycle. We focus in particular on theinfluence of large-scale topographical features on the atmosphericflow, atmospheric moisture transport, and cloud formation. Highlatitude transient weather systems have previously beenidentified as important contributors to global atmosphericmethane transport, and here we examine whethertopographically-forced stationary or quasi-permanent systemsare also important, as they are in Earth’s hydrologic cycle.

Author(s): Juan M Lora , Sean Faulk , Jonathan MitchellInstitution(s): 1. University of California, Los Angeles

304.03 – Seasonal variations in Titan’sstratosphere observed with Cassini/CIRS duringnorthern springSince 2004, Cassini performed 127 close Titan flybys, observingits atmosphere with instruments including the Cassini CompositeInfraRed Spectrometer (CIRS). We know from CIRS observationsthat the global dynamics drastically changed after the northernspring equinox that occurred in August 2009 ([1], [2], [3], [4]).The pole-to-pole middle atmosphere dynamics (above 100 km)experienced a global reversal in less than 2 years after the equinox

[4], while the northern hemisphere was entering spring. This newpattern, with downwelling at the south pole, resulted in anenrichment of almost all molecules inside the southern polarvortex since 2011. According to General Circulation Modelcalculations, this single circulation cell pattern should remainuntil 2025. We will present an analysis of CIRS limb observations up to 2017,during the entire northern spring. We show that many species(C H , HCN, HC N, C H , C H , CH CCH, C H ) experiencedtheir highest enrichments near the south pole near 500 km inMarch 2015, with abundances similar to in situ results fromINMS at 1000 km [5], suggesting that the air inside the confinedpolar vortex (observed at latitudes higher than 80°S) was veryefficiently transported downward from very high altitudes. InSeptember 2015, an extension of the polar vortex towards lowerlatitudes (~65°S) was observed, while the molecular abundancesdecreased by a factor of 10 at 500 km. In the same region,unexpectedly cold stratospheric temperatures were observedbelow 300 km from May 2013 to the end of 2015. Simultaneously,after the disruption of the north polar vortex after the equinox,the enriched air that was previously confined at very high latitudegradually expended towards mid latitudes at altitudes higher than300 km. At the beginning of 2016, a zone depleted in moleculargas and aerosol is observed in the entire northern hemispherebetween 400 and 500 km, suggesting some complex unknowndynamical effect. References: [1] Teanby, N. et al., 2012, Nature, 491, pp. 733-735. [2] Achterberg et al., DPS 46, abstract 102.07,Tucson, 2014. [3] Coustenis et al., 2016, , Icarus 270, 409-420. [4] Vinatier et al., 2015, Icarus, 250, 95-115. [5] Cui et al., 2009, , Icarus, 200, 581-615.

Author(s): Sandrine Vinatier , Bruno Bézard , NicholasTeanby , Sébastien Lebonnois , Richard Achterberg , NicolasGorius , F. Michael FlasarInstitution(s): 1. Laboratoire de Météorologie Dynamique(LMD/IPSL), Sorbonne Universités, UPMC Univ Paris 06,CNRS/INSU, 2. LESIA, Observatoire de Paris, PSL ResearchUniversity, CNRS, Sorbonne Universités, UPMC Univ. Paris 06,Univ. Paris Diderot, Sorbonne Paris Cité, 3. NASA/GSFC,Greenbelt, MD, United States, 4. School of Earth Science,University of Bristol, 5. University of Maryland, Department ofAstronomyContributing team(s): CIRS Team

304.04 – Abundance Profiles for C3 Hydrocarbonsin Titan's AtmosphereThe atmosphere of Titan is of astrobiological importance. Itshighly reducing composition and prebiotic chemistry make itanalogous to that of the early Earth. Since the Voyager era,several complex hydrocarbons and nitriles have been detected, insome cases making Titan the only known planetary body wherethese gasses occur naturally. In this work, we report abundanceprofiles of four major C3 gasses expected to occur in Titan’satmosphere, derived from Cassini/Composite InfraredSpectrometer (CIRS) data. Using the NEMESIS iterative radiative transfer module, weretrieved vertical abundance profiles for propane (C3H8) andpropyne (CHCCH3), both initially detected by the Voyager IRISinstrument. Using newly available line data, we were also able todetermine the first vertical abundance profiles for propene(C3H6), initially detected in 2013. We present profiles for severallatitudes and times and compare to photochemical modelpredictions and previous observations. We also discuss our effortsto further the search for allene (CH2CCH2), an isomer ofpropyne. The abundances we retrieved will help to further ourunderstanding of the chemical pathways that occur in Titan'satmosphere.

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Author(s): Nicholas Lombardo , Conor A. Nixon , RichardAchterberg , Antoine Jolly , Keeyoon Sung , Patrick Irwin , F.Michael FlasarInstitution(s): 1. Goddard Space Flight Center, 2. JetPropulsion Laboratory, 3. Laboratoire Interuniversitaire desSystemes Atmospherique, 4. University of Maryland BaltimoreCounty, 5. University of Maryland, College Park, 6. University ofOxford

304.05 – The Titan Haze Simulation Experiment:Latest Laboratory Results and Dedicated PlasmaChemistry ModelHere, we present the latest results on the gas- and solid phaseanalyses in the Titan Haze Simulation (THS) experiment,developed at the NASA Ames COSmIC simulation chamber. TheTHS is a unique experimental platform that allows us to simulateTitan’s complex atmospheric chemistry at Titan-like temperature(200 K) by cooling down N2-CH4-based mixtures in a supersonicexpansion before inducing the chemistry by plasma. Because ofthe accelerated gas flow in the expansion, the residence time ofthe gas in the active plasma region is less than 3 µs. This results ina truncated chemistry that enables us to control how far in thechain of chemical reactions chemistry processes[1], by adding, inthe initial gas mixture, heavier molecules that have been detectedas trace elements on Titan. We discuss the results of recent Mid-infrared (MIR)spectroscopy[2] and X-ray Absorption Near Edge Structurespectroscopy studies of THS Titan tholins produced in differentgas mixtures (with and without acetylene and benzene). Bothstudies have shown the presence of nitrogen chemistry, anddifferences in the level and nature of the nitrogen incorporationdepending on the initial gas mixture. A comparison of THS MIRspectra to VIMS data has shown that the THS aerosols producedin simpler mixtures, i.e., that contain more nitrogen and wherethe N-incorporation is in isocyanide-type molecules instead ofnitriles, are more representative of Titan’s aerosols. In addition, a new model has been developed to simulate theplasma chemistry in the THS. Electron impact and chemicalkinetics equations for more than 120 species are followed. Thecalculated mass spectra[3] are in good agreement with theexperimental THS mass spectra[1], confirming that the shortresidence time in the plasma cavity limits the growth of largerspecies and results in a truncated chemistry, a main feature of theTHS.

References: [1] Sciamma-O'Brien E. et al., Icarus, 243, 325 (2014) [2] Sciamma-O'Brien E. et al., Icarus, 289, 214 (2017) [3] Raymond, A. et al., submitted

Author(s): Ella Sciamma-O'Brien , Alexander Raymond ,Eric Mazur , Farid SalamaInstitution(s): 1. Harvard University, 2. NASA Ames ResearchCenter

304.06 – ALMA and Cassini Comparisons of Titan’sStratospheric Temperature from 2012—2015In the post-Cassini era, the Atacama LargeMillimeter/Submillimeter Array (ALMA) will be a valuable assetcapable of measuring latitudinal and seasonal changes in Titan’satmosphere. Carbon monoxide (CO) emission provides anexcellent probe of Titan’s atmospheric temperature due to themolecule's long chemical lifetime and stable, well constrainedvolume mixing ratio. We present disk-averaged temperatureprofiles of Titan’s upper troposphere through the mesosphere(~50–550 km) obtained through the analysis of 4 ALMAobservations of CO rotational emission lines obtained in 2012,2013, 2014, and 2015 with ALMA. Additionally, ALMA’s highspatial resolution in the 2012, 2014, and 2015 datasets allows usto extract spectra from 3 separate regions on Titan’s disk (~48 N,20 N, and 15 S). Temporal and latitudinal variations will bediscussed, including warming of the stratopause (320 km) andlower stratosphere from 2012–2015 in northern latitudes, withconsistently cooler stratospheric temperatures in the north

compared to lower latitudes by up to 15 K. ALMA temperatureprofiles are compared to Cassini Composite InfraredSpectrometer (CIRS) and radio occultation sciencemeasurements. Though retrieved temperature profiles from ALMA data cover arange of latitudes due to beam sizes ranging from 0.35 x 0.28'' to0.39 x 0.34'', deviations from CIRS data are often found to be lessthan 5 K, and within the retrieved errors, throughout theatmosphere. We observe generally cooler temperatures in thelower stratosphere (~100 km) than those obtained throughCassini radio occultation measurements, with the notableexception of warming in the northern latitudes and the absence ofprevious instabilities. ALMA's excellent sensitivity in the lowerstratosphere (60–300 km) provides a highly complementarydataset to contemporary CIRS and radio science observations,and lays the groundwork for future studies of molecular speciesvisible in the millimeter/submillimeter on Titan.

Author(s): Alexander Thelen , Conor A. Nixon , Nancy J.Chanover , Ned Molter , Martin Cordiner , RichardAchterberg , Joseph Serigano , Patrick Irwin , NicholasTeanby , Steven B. CharnleyInstitution(s): 1. Johns Hopkins University, 2. NASA/GSFC, 3.New Mexico State University, 4. University of Bristol, 5.University of California, Berkeley, 6. University of Oxford

304.07 – Spectroscopic detection and mapping ofvinyl cyanide on TitanThe first spectroscopic detection of vinyl cyanide (otherwiseknown as acrylonitrile; C2H3CN) on Titan was obtained byPalmer et al. (2017), based on three rotational emission linesobserved with ALMA at millimeter wavelengths (in receiver band6). The astrobiological significance of this detection washighlighted due to the theorized ability of C2H3CN molecules tocombine into cell membrane-like structures under the coldconditions found in Titan's hydrocarbon lakes. Here we report thedetection of three additional C2H3CN transitions at higherfrequencies (from ALMA band 7 flux calibration data). Wepresent the first emission maps for this gas on Titan, andcompare the molecular distribution with that of other nitrilesobserved with ALMA including HC3N, CH3CN, C2H5CN andHNC. The molecular abundance patterns are interpreted based onour understanding of Titan's high-altitude photochemistry andtime-variable global circulation. Similar to the short-lived HC3Nmolecule, vinyl cyanide is found to be most abundant in thevicinity of the southern (winter) pole, whereas the longer-livedCH3CN is more concentrated in the north. The verticalabundance profile of C2H3CN (from radiative transfer modeling),as well as its latitudinal distribution, are consistent with a shortphotochemical lifetime for this species. Complementary resultsfrom our more recent (2017) nitrile mapping studies at higherspatial resolution will also be discussed. REFERENCES: Palmer, M. Y., Cordiner, M. A., Nixon, C. A. et al. "ALMAdetection and astrobiological potential of vinyl cyanide on Titan",Sci. Adv. 2017, 3, e1700022

Author(s): Martin Cordiner , Maureen Yukiko Palmer ,James Lai , Conor A. Nixon , Nicholas Teanby , Steven B.Charnley , Veronique Vuitton , Zbigniew Kisiel , Patrick Irwin ,Ned Molter , Michael J. MummaInstitution(s): 1. McMaster University, 2. NASA GoddardSpace Flight Center, 3. Polish Academy of Sciences, 4. UniversitéGrenoble Alpes, 5. University of Bristol, 6. University ofCalifornia, 7. University of Oxford

304.08 – Retrievals of abundances of hydrocarbonand nitrile species in Titan’s upper atmosphereWe develop an innovative retrieval method for Titan occultationmeasurements by the Cassini UVIS experiment. The T35occultation is analyzed to illustrate the methodology. A significantnumber of occultations observed using the UVIS spectrographs

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show loss of pointing control required for correction of thespectral vectors. Consequently, only three stellar occultationshave been analyzed to date. We use the Markov Chain Monte-Carlo (MCMC) method to retrieve the abundances or upper limitsof thirteen hydrocarbon and nitrile species (N , CH , C H ,C H , C H , HCN, C H , C N , C H , tholin, HC N, C N ,NH ) along with the pointing error using the Cassini/UVISsimulator. These numbers are derived for the fast T35occultation, which has never been analyzed because of largepointing errors. Uncertainty in the retrievals is determined usingan intrinsic fitting probability distribution function. TheCaltech/JPL photochemical and kinetics model, KINETICS, isused to calculate the atmospheric aforementioned species.Comparisons between model and observations reveal gaps in ourcurrent understanding of the chemical kinetics of hydrocarbonsand nitrile species, especially for C H .

Author(s): Yuk Yung , Siteng Fan , D. E. Shemansky , ChengLi , Peter GaoInstitution(s): 1. Caltech, 2. Jet Propulsion Laboratory, 3.NASA Ames Research Center, 4. Space EnvironmentTechnologies

304.09 – Analyzing the Dynamic andMorphological Characteristics of Clouds on Titanusing the Cassini VIMS DatasetWe present here a comprehensive analysis of troposphericmethane clouds in Titan's atmosphere as imaged by the Visibleand Infrared Mapping Spectrometer (VIMS) on board the Cassinispacecraft. When incoming light reaches Titan, increasedscattering off cloud particles leads to brightening in certainwavelengths of albedo spectra, and we visually identify cloudyregions using the relative reflectivity of individual pixels intropospheric channels. By manually progressing through theentirety of the VIMS dataset (~25,000 applicable image cubes),we have used this method to analyze the morphologies and spatialevolutions of 200+ discrete cloud systems over varioustimescales. Imaged cloud coverage areas range up to ~4.4% ofTitan's total surface area, and we resolve speeds up to greaterthan 25 m/s for sequences spanning observational durations ofseconds to days. Applying a radiative transfer model to the cloudsequences provides for the calculation of meridional wind speedprofiles, and we observe cloud displacement velocities generallyexceeding equatorial wind speeds measured by the Huygensprobe. In addition to characterization, our mapping efforts offerboth a global distribution of cloud coverage frequency and a long-term picture of latitudinal cloud distribution as a function of time.These seasonal variations illustrate the dynamic nature ofmethane in Titan's atmosphere, so a comprehensive cloud datasetis conducive to placing better constraints on general circulationmodels (GCMs). Connections between characterization andmapping can also be made using the search results, formorphologic variations can be indexed in order to explore cloudformation mechanisms.

Author(s): John Kelland , Paul Corlies , Alexander Hayes ,Sebastien Rodriguez , Elizabeth P. TurtleInstitution(s): 1. Cornell University, 2. Johns HopkinsUniversity Applied Physics Laboratory, 3. University of Paris 7,Diderot

304.10 – Titan’s High Altitude South Polar (HASP)Stratospheric Ice Cloud as observed by CassiniCIRSDuring Cassini’s T112 flyby of Titan in the late southern fallseason (July 2015), the Composite InfraRed Spectrometer (CIRS)made a startling discovery - a massive cloud system haddeveloped throughout Titan’s mid stratosphere (~200 km) athigh southern latitudes. The vertical distributions of intensity ofthis High-Altitude South Polar (HASP) stratospheric ice cloudsystem are at least an order of magnitude stronger than the CIRS-observed northern winter polar stratospheric cloud system [1].The chemical composition of the HASP cloud is not identical to itsnorthern winter counterpart, in that it exhibits different spectral

characteristics. The HASP cloud is just one illustrative exampledemonstrating the rapidly changing conditions occurring inTitan’s south polar stratospheric region as Titan began its journeyinto southern winter. Such observed changes are contrary to theobserved configuration as Titan’s northern polar stratospheretransitioned out of northern winter, which revealed a relativelyslow decay of: 1) the cold polar stratospheric temperatures, 2) thestrength of the polar vortex, and 3) the abundances instratospheric organic gases and ices. We will discuss the physical and chemical characteristics of theCIRS-observed HASP mid stratospheric ice cloud system.Potential ice analog candidates obtained from thin filmtransmission spectra of co-condensed nitrile/hydrocarbon icemixtures obtained with our SPECtroscopy of Titan-Related iceAnaLogs (SPECTRAL) chamber are used to support theseanalyses. [1] Anderson C. M. and Samuelson R. E. (2011) Icarus, 212, 762-778.

Author(s): Carrie Anderson , Delphine Nna-Mvondo ,Robert E. Samuelson , Richard K. Achterberg , F. MichaelFlasar , Donald E. Jennings , Francois RaulinInstitution(s): 1. LISA, UPEC-UPD/CNRS/IPSL, 2. NASAGSFC, 3. University of Maryland, 4. USRA

304.11 – Imaging Molecular Species in Titan'sStratosphere and Mesosphere using ALMAEach flyby of Titan by the Cassini spacecraft demonstrates theimportance of characterizing and monitoring the distributions ofmolecular species; it provides insight into the variability ofchemistry and atmospheric circulation which exhibit significant,global changes occurring over relatively short time periods as wellas seasonally. However, the Cassini mission will end inSeptember 2017, less than half a Titan year after arrival.Fortunately, the unique sensitivity, access to many submillimeterspectral lines, and high resolution capabilities of the AtacamaLarge Millimeter/submillimeter Array (ALMA) will allow forextended, detailed exploration of the global properties of Titan’sstratosphere. We utilized ALMA to obtain a comprehensive view of Titan'sstratosphere in mid-2016 using three tunings covering highimpact portions of the 870 micron atmospheric window.Observations were made on July 22 and August 19, obtaininghigh spectral and spatial resolution imaging of many importantspecies in Titan's atmosphere, including CO (plus CO andC O), HCN (plus DCN, H CN, and HC N), HNC, CH CN,CH CCH, C H CN, and HC N, while covering lines of otherspecies and their isotopomers. The resolution achieved was 0.14"in the N-S direction, equivalent to ~900 km linear resolution atthe distance of Titan. Selected species were observed withextremely high spectral resolution (including CH CN, HCN,HNC, DCN, and HC N) allowing for direct measure of globalcirculation at different altitudes. While the data were only recently delivered, preliminary resultsshow that many molecules show spectacular gradients as afunction of latitude, and they vary by species. For example,CH CN shows very strong emission in the high northernlatitudes, CH CCH shows peaks at both high northern andsouthern latitudes (with preference to the north), while HC Npeaks at high southern latitudes. Winds show zonal speeds of 200m/s (from CH CN) and up to 300 m/s (HCN and HC N); theHCN and HC N line cores probe higher altitudes than CH CN,suggesting increasingly strong zonal winds with altitude. We will present analyses of spatially abundances, temperatures,isotopic ratios, and global circulation, based upon these detailedALMA observations.

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Author(s): Mark A. Gurwell , Raphael Moreno , SandrineVinatier , Emmanuel Lellouch , Bryan J. Butler , ArielleMoullet , Eric Villard , Taufiq Hidayat , Luisa LaraInstitution(s): 1. ALMA/ESO, 2. Bosscha Obs. & Dept.Astronomy, Institut Teknologi Bandung, 3. Harvard-Smithsonian Center For Astrophysics, 4. IAA-CSIC, 5. LESIA,Obs. de Paris-Meudon, 6. NRAO, 7. NRAO

304.12D – A Report of Clouds on Titan We present in this work a detailed analysis of many of the cloudsin the Cassini Visual and Infrared Mapping Spectrometer (VIMS)dataset in order to understand their global and seasonalproperties. Clouds are one of the few direct observables in Titan’satmosphere (Griffith et al 2009, Rodriguez et al 2009,Adamkovics et al 2010), and so determining their characteristicsallows for a better understanding of surface atmosphereinteractions, winds, transport of volatile material, and generalcirculation. We find the clouds on Titan generally reside in at 5-15km altitude,which agrees with previous modelling efforts (Rafkin et al. 2015),as well as a power law distribution for cloud optical depth. Weassume an average cloud droplet size of 100um. No seasonaldependence is observed with either cloud altitude or opticaldepth, suggesting there is no preferred seasonal formationmechanisms. Combining these characteristics with cloud size(Kelland et al 2017) can trace the transport of volatiles in Titan’satmosphere, which can be compared against general circulationmodels (GCMs) (Lora et al 2015). We also present some specific analysis of interesting cloudsystems including hypothesized surface fogs (Brown et al 2009)and orographic cloud formation (Barth et al 2010, Corlies et al

2017). In this analysis we use a correlation between Cassini VIMSand RADAR observations as well as an updated topographic mapof Titan’s southern hemisphere to better understand the role thattopography plays in influencing and driving atmosphericphenomena. Finally, with the end of the Cassini mission, ground basedobserving now acts as the only means with which to observeclouds on Titan. We present an update of an ongoing cloudcampaign to search for clouds on Titan and to understand theirseasonal evolution. References: Adamkovics et al. 2010, Icarus 208:868 Barth et al. 2010, Planet. Space Sci. 58:1740 Corlies et al. 2017, 48 LPSC, 2870C Griffith et al. 2009, ApJ 702:L105 Kelland et al. 2017, 48 LPSC, 2748K Lora et al. 2015, Icarus 250:516 Rafkin et al. 2015, J. Geophys. Res. 120:739 Rodriguez et al. 2009, Nature 459:678

Author(s): Paul Corlies , Alexander Hayes , MateAdamkovics , Sebastien Rodriguez , John Kelland , Elizabeth P.Turtle , Jonathan Mitchell , Juan M Lora , Patricio Rojo ,Jonathan I. LunineInstitution(s): 1. Applied Physics Laboratory, 2. ClemsonUniversity, 3. Cornell University, 4. Universidad de Chile, 5.Université Paris Diderot, 7, 6. University of California, LosAngeles, 7. Westmont College

305.01 – Isotopic Ratios in a Peculiar OutburstingCometIsotopic ratios in comets provide keys for the understanding ofthe origin of cometary material, and the physical and chemicalconditions in the early Solar Nebula. A newly discovered peculiarcomet, C/2015 ER61, underwent an outburst with a totalbrightness increase of 2 magnitudes on the night of April 4th,2017. The sharp increase in brightness offers a rare opportunityto measure the isotopic ratios of the light elements of this comet.We obtained two high-resolution spectra of C/2015 ER61 withUVES on Apr. 13 and Apr. 17 respectively. At the time of ourobservations, the comet was fading gradually since the outburst.We measured the 12C/13C and 14N/15N isotopic ratios from theCN Violet (0,0) band. In addition, we determined the 14N/15Nratio in NH2 for C/2015 ER61 from four pairs of NH2isotopologue lines. Some 18OH lines were detected but the S/N ofthese lines is too low to derive a reliable 18O/16O estimate. Wewill present our UVES spectra of C/2015 ER61, obtained shortlyafter the outburst. We will also present the comparison of theIsotopic ratios of C/2015 ER61 with those of other comets.

Author(s): Bin Yang , Damien Hutsemekers , YoshiharuShinnaka , Emmanuel Jehin , Karen Jean Meech , CyrielleOpitom , Olivier Hainaut , Jacqueline Keane , Jean ManfroidInstitution(s): 1. National Astronomical Observatory of Japan, 2. European Southern Observatory, 3. Université de Liège, 4.University of Hawaii

305.02 – The Volatile Composition of newly-discovered C/2017 E4 (Lovejoy) before itsdissolution as revealed by iSHELL at NASA/IRTFIn April 2017, we acquired comprehensive high-resolution spectraof newly-discovered comet C/2017 E4 (Lovejoy) as it approachedperihelion, and before its disintegration. We detected manycometary emission lines across 4 customized instrument settings(L1-b, L3, Lp1-b and M1) in the (1 – 5) μm range, using iSHELL -the new near-IR high resolution immersion echelle spectrographon NASA/IRTF (Mauna Kea, Hawaii). In M1, near 5μm, we detected multiple ro-vibrational lines ofH O, CO and the (X-X) system of CN; the latter data constitute a

complete survey of CN at these wavelengths. We derivedquantitative abundances for CN and addressed its origin bycomparing with quantitative production rates for HCN. Theability to quantify both primary and product species eliminatessystematic error that may be introduced when measurements areacquired with different astronomical techniques and instruments. In L1, around 3 μm, we detected fluorescence emission fromHCN, C H , and water, prompt emission from OH, and manyother features. Methane, ethane and methanol were detected bothin L3 and Lp1 settings. These species are relevant to astrobiology,owing to questions regarding the origin of pre-biotic organics andwater on terrestrial planets. The many water emission lines detected in L1-b (and M1)provided an opportunity to retrieve independent measures ofrotational temperature for ortho- and para-H O, therebyreducing systematic uncertainty in the derived ortho-para ratioand nuclear spin temperature. Deuterated species were alsosought and results will be presented. The bright Oort cloud comet E4 Lovejoy combined with the newcapabilities of iSHELL provided unique results. The individualiSHELL settings cover very wide spectral range with very highaccuracy, eliminating many sources of systematic errors whenretrieving molecular abundances; future comparisons amongstcomets will clarify the nature and meaning of cosmogonicindicators based on composition. Acknowledgments NASA’s Postdoctoral Program andAstrobiology Programs supported this work.

Author(s): Sara Faggi , Geronimo Luis Villanueva , Michael J.Mumma , Lucas PaganiniInstitution(s): 1. NASA Goddard Space Flight Center

305.03 – Opportunities for in-depth compositionalstudies of comets: Summary from semester 2017Aobservations and prospects for a 2018 observingcampaignThe period from late 2016 to mid 2017 provided unusually richobservational opportunities for compositional studies of cometsusing ground-based IR and optical spectroscopy. Three eclipticcomets – Jupiter-family comet (JFC) 45P/Honda-Mrkos-Pajdusakova, JFC 41P/Tuttle-Giacobini-Kresak, and 2P/Encke –as well as two moderately bright nearly istotropic comets from the

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Oort cloud (C/2015 ER61 PanSTARRS and C/2015 V2 Johnson)experienced highly favorable appritions.

In the IR, very long on-source integration times wereaccumulated on all targets, primarily with the powerful new high-resolution, cross-dispersed iSHELL spectrograph at the IRTF(Rayner et al. 2016 SPIE 9908:1) but also with NIRSPEC at KeckII. This enabled accurate production rates and abundance ratiosfor 8-10 native ices, and spatially resolved studies of coma physics(H O rotational temperatures and column abundances). Therecent availability of iSHELL coupled with the daytime observingcapability at the IRTF has opened a powerful window forconducting detailed compositional studies of comets over a rangeof heliocentric distances (R ), particularly at small R wherestudies are relatively sparse. Our campaign provided detections of(or stringent abundance limits for) hyper-volatiles CO and CH ,which are severely lacking in compositional studies of JFCs.

For all of these targets, optical spectra measured photo-dissociation product species using the Tull Coude spectrograph atMcDonald Observatory, and ARCES at Apache Point Observatory.When possible optical and IR observations were obtainedcontemporaneously, with the goal of addressing potential parent-product relationships.

We summarize our campaign and highlight related presentations.Prospects for investigations during the upcoming favorableapparitions of JFCs 21P/Giacobini-Zinner and 46P/Wirtanen willalso be discussed, along with increased capabilities for serialstudies (i.e., measurements at multiple R ) of newly discovered(Oort cloud) comets.

This work is supported through the NASA PlanetaryAtmospheres, Planetary Astronomy, and Astrobiology Programs,the NSF Solar and Planetary Research Program, the NASA-Postdoctoral Program, and the NASA Earth and Space ScienceFellowship Program.

Author(s): Michael A. DiSanti , Neil Dello Russo , BonchoP. Bonev , Erika L. Gibb , Nathan Roth , Ronald J. Vervack ,Adam J. McKay , Hideyo Kawakita , Anita L. CochranInstitution(s): 1. American U., 2. JHU-APL, 3. KoyamaAstronomical Observatory, 4. McDonald Observatory, 5. NASA'sGSFC, 6. U. Missouri - St. Louis, 7. Universities Space ResearchAssociation

305.04 – Evolving coma abundances and detectionof hypervolatiles in Jupiter-family comet45P/Honda-Mrkos-PajdusakovaTwo major shortcomings in chemically classifying comets atinfrared wavelengths are a lack of hypervolatile (CO and CH )detections in Jupiter-family comets and incomplete temporalcoverage of comet chemistry, particularly at small heliocentricdistances (R ). We report post-perihelion volatile abundances incomet 45P/Honda-Mrkos-Pajdusakova with the high-resolutioninfrared spectrometer iSHELL at the NASA/IRTF on UT 6 – 8January when R = 0.55 AU (DiSanti et al. 2017, Astron. J., inpress), and with NIRSPEC at the Keck Observatory on UT 13 and19 February when R = 1.0 and 1.1 AU, respectively. Favorablecomet geocentric velocities enabled the detection of CO and CHin early January and 19 February. The relative abundance of CO isseverely depleted whereas CH is typical to enriched in 45P whencompared to comets from the Oort cloud. Significant differencesare seen in relative abundances of species between January andFebruary, notably in the ratio of C H /HCN. We explore whetherthe heliocentric distances of the measurements or seasonalchanges primarily cause these differences by comparing toobservations of C/2012 S1 ISON obtained over a similar range ofheliocentric distances. NASA and NSF research grants supportthis work. We also acknowledge the expert support of the IRTFand Keck support staffs during these observations.

Author(s): Neil Dello Russo , Michael A. DiSanti , HideyoKawakita , Yoshiharu Shinnaka , Ronald J. Vervack , Boncho P.Bonev , Erika L. Gibb , Nathan Roth , Adam J. McKay , HaroldA Weaver , Anita L. CochranInstitution(s): 1. American University, 2. JHU-APL, 3.Koyama Astronomical Observatory, 4. McDonald Observatory,5. NASA-GSFC, 6. National Astronomical Observatory of Japan,7. University of Missouri-St. Louis

305.05 – The radial and azimuthal properties ofvolatiles and dust in the inner coma of Comet45P/Honda-Mrkos-PajdušákováIn February 2017 comet 45P/Honda-Mrkos-Pajdušáková (HMP)passed by the Earth at a perigee distance of 0.08 AU. Suchencounters provide an important opportunity for study of theinner coma region where gas and dust production occur. Wereport here on wide-field (30 x 30 arcminute), high-spatialresolution (35 km/pixel) observations of HMP obtained with the90Prime One imager on the 2.3m Bok telescope at Kitt Peak. Theobservations were performed on February 16 and 17, when thecomet was 0.1 AU from Earth, using a combination of a wide-band Gunn r’ filter and a subset of the HB filter library (OH, CN,C2, Blue Continuum). In this presentation we will discuss thedistribution and color of the dust, the relative production rates ofvolatiles, and the implied parent-daughter photochemicalevolution from radial expansion modeling.

Author(s): Walter M. Harris , Erin L. Ryan , AlessondraSpringmann , Beatrice E. A. Mueller , Nalin H. Samarasinha ,Jean-Baptiste Kikwaya Elou , Ellen S. Howell , CassandraLejoly , Julia Bodnarik , Ryleigh Fitzpatrick , Ricardo Maciel ,Adriana Mitchell , Zachary Tyler WatsonInstitution(s): 1. ORAU-Goddard Space Flight Center, 2.Planetary Science Institute, 3. University of Arizona Lunar andPlanetary Lab, 4. Vatican Observatory

305.06 – Particle Sizes in the Coma of Comet45P/Honda-Mrkos-Pajdušáková from AreciboRadar ObservationsRadar observations of cometary comae can provide informationabout not only the cross-section of the coma, but also constraintson the particle sizes comprising the coma. Harmon et al. (2011)described analysis of radar observations of comet 103P/Hartley 2to constrain the sizes of its coma particles, as well as modeling toanalyze the particle velocity distribution in the coma andorientation with respect to the sun. Arecibo Observatoryplanetary radar system observations of comet 45P/Honda-Mrkos-Pajdušáková were obtained 9-16 February 2017 by transmitting acontinuous wave of polarized radio waves at the comet. Byexamining the polarization ratios of the returned signal (whetherit has the same sense or opposite sense of the transmitted signal),we can look for non-zero same sense polarization signal.Detectable same sense signal indicates the presence of particleswith sizes larger than the Rayleigh transition size criteria, a =λ/2π ≈ 2 cm (for the Arecibo wavelength of 12.6 cm). The observations show strong opposite sense signal return fromthe comet nucleus, as well as a larger ‘skirt’ of surrounding grainsin the coma. Preliminary analysis of this data indicates at least aweak same sense polarized signal, implying a population of grainslarger than 2 cm in the coma. The sizes of particles in the coma,compared with the area of the coma, can help us constrain theminimum mass for particles at the Rayleigh size limit in the 45Pcoma. Further, a detectable grain halo of large particles around45P would imply significant lofting of grains from the cometnucleus. References Harmon, John K., et al. "Radar observations of comet103P/Hartley 2." The Astrophysical Journal Letters 734.1 (2011):L2.

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305.07 – CN Jet Morphology and the Very RapidlyChanging Rotation Period of Comet 41P/Tuttle-Giacobini-Kresak In the first half of 2017, Comet 41P/Tuttle-Giacobini-Kresak hadits best apparition since its first discovery in 1858, remainingwithin 0.15 AU of Earth for three weeks and within 0.20 AU overa two month interval. These circumstances allowed us to study itscoma morphology in search of possible jets, whose appearanceand motion as a function of time would yield the rotation periodand, with appropriate modeling, the pole orientation of thenucleus and source location(s). Imaging was obtained on a totalof 45 nights between February 16 and July 2, using LowellObservatory's 4.3-m Discovery Channel Telescope, the Hall 1.1-mtelescope, and the robotic 0.8-m telescope. All narrowband CNimages exhibit either one or two gas jets, and on most nights bothjets appear as partial spirals with a clockwise rotation. Only aslow evolution of the jet morphology took place from mid-Marchto early June, presumably due to viewing geometry changescoupled with seasonal changes. Our coverage in late March wassufficient to rule out aliases of the rotation period, and furtherrevealed a rapidly increasing period from about 24 hr to about 27hr at the end of the month (Knight et al. 2017, CBET 4377). Thisrate of increase is roughly consistent with the solution of 19.9 hrfound by Farnham et al. (2017, CBET 4375) in early March.Images from April 15 to May 4 yield an accelerating change inperiods, passing 48 hr approximately on April 28. This is thefastest rate of change ever measured for a comet nucleus. Theseand other results, including those from Monte Carlo jet modelingjust begun by us, will be presented.

These studies were supported by NASA Planetary Astronomygrant NNX14AG81G and the Marcus Cometary Research Fund.

Author(s): David G. Schleicher , Nora Eisner , Matthew M.Knight , Audrey ThirouinInstitution(s): 1. Lowell Obs., 2. Univ. of Maryland

305.08 – Detection of CO and HCN in the coma ofJupiter-family comet 41P/Tuttle-Giacobini-KresakComets are divided into taxonomical groups determined largelyby their orbits. Short-period Jupiter Family comets (JFCs) arethought to have formed in a trans-Neptunian disk ∼30 - 100 AU(Kuiper Belt) and then migrated inward (Edgeworth 1949, Kuiper1951, Duncan et al. 1988). This different classification may becorrelated with chemical abundance variations, and super-volatilespecies like CO can serve as an indicator of the thermal processesto which the precometary ices that led to comets where exposed(DiSainti et al. 2007). The close approach to Earth of comet 41Pon the perihelion passage of 2017 was an excellent opportunity toprobe the usually well-hidden inner coma of this Jupiter-familycomet. We searched for CO (J=2-1) and HCN (J=3-2) emissionwith the Arizona Radio Observatory (ARO) 10-m Sub-millimeterTelescope (SMT) on 2017 April 1-2, when the comet was 1.1 AUfrom the Sun and 0.14 AU from Earth. We report the detection ofboth CO and HCN emission 13 days before perihelion and presentcolumn densities and production rates. We also discussimplications for Jupiter-family comets. The SMT is operated bythe ARO, the Steward Observatory, and the University ofArizona, with support through the NSF University RadioObservatories program (AST-1140030). M.W. acknowledgessupport from NSF grant AST-1615917.

Author(s): Kacper Wierzchos , Maria WomackInstitution(s): 1. University of South Florida

305.09 – Constraining the Volatile Compositionand Coma Photochemistry in Jupiter Family Comet41P/Tuttle-Giacobini-Kresak with High ResolutionIR and Optical SpectroscopyOver the past 20 years optical and IR spectroscopy of cometarycomae has expanded our understanding both of cometary volatilecomposition and coma photochemistry. However, theseobservations tend to be biased towards Nearly Isotropic Comets(NIC's) from the Oort Cloud, rather than the generally fainter andless active Jupiter Family Comets (JFC's) that are thought tooriginate from the Scattered Disk. However, early 2017 provided arare opportunity to study several JFC's. We present preliminaryresults from IR and optical spectroscopy of JFC 41P/Tuttle-Giacobini-Kresak obtained during its 2017 apparition. IR spectrawere obtained with the NIRSPEC instrument on Keck II and thenew iSHELL spectrograph on NASA IRTF. High spectralresolution optical spectra were obtained with the Tull Coudespectrograph on the 2.7-meter Harlan J. Smith Telescope atMcDonald Observatory. We will discuss mixing ratios of HCN,NH , C H , C H , H CO, and CH OH compared to H O andcompare these to previous observations of comets. Preliminaryresults from the NIRSPEC observations indicate that 41P hastypical C H and HCN abundances compared to other JFC's,while the C H abundance is similar to that of NIC's, but isenriched compared to other JFC's. H CO appears to be heavilydepleted in 41P. Analysis of the iSHELL spectra is underway andwe will include results from these observations, whichcomplement those from NIRSPEC and extend the scope or ourcompositional study by measuring additional molecules. We willalso present abundances for CN, C , NH , C , and CH obtainedfrom the optical spectra and discuss the implications for the comaphotochemistry. This work is supported by the NASA Postdoctoral Program,administered by the Universities Space Research Association,with additional funding from the NSF and NASA PAST.

Author(s): Adam McKay , Michael A. DiSanti , Anita L.Cochran , Neil Dello Russo , Boncho P. Bonev , Ronald J.Vervack , Erika L. Gibb , Nathan X. Roth , Hideyo KawakitaInstitution(s): 1. American University, 2. Johns HopkinsApplied Physics Laboratory, 3. Kyoto Sangyo University, 4.NASA GSFC, 5. NASA GSFC/USRA, 6. University of Missouri-St.Louis, 7. University of Texas Austin/McDonald Observatory

305.10 – The Reactivations of Main-Belt Comets238P/READ, 259P/Garradd, and 288P/(300163)2006 VW139We report on the confirmation and monitoring of recurrentactivity for main-belt comets (MBCs) 238P/Read and288P/(300163) 2006 VW139 in 2016 (cf. Agarwal et al. 2016,CBET 4306; Hsieh et al. 2016, CBET 4307), as well as theidentification of activity for 288P in Sloan Digital Sky Surveyimages from November 2000. We will also report on theconfirmation of recurrent activity in 2017 (Hsieh et al. 2017,CBET 4388) and the progress of the ongoing monitoringcampaign (April 2017 through December 2017) that we areconducting for MBC 259P/Garradd. With these observations,238P and 288P have now each been observed to be active onthree separate orbit passages with intervening periods ofinactivity and 259P has been observed to be active on twoseparate orbit passages, firmly establishing the cometary (i.e.,sublimation-driven) nature of their activity. We are currentlyconducting a multi-facility observing campaign to monitor thephotometric and morphological evolution of these objects, usingthe Canada-France-Hawaii Telescope, the Gemini North andSouth telescopes (under a Gemini Large and Long Program), theMagellan telescopes, the Discovery Channel Telescope, and theLulin One-meter Telescope. During their most recent perihelionencounters, 238P was observed to be active as early as 2016 July8 at a true anomaly of 329 degrees, 288P was observed to beactive as early as 2016 June 8 at a true anomaly of 318 degrees,and 259P was observed to be active as early at 2017 April 26 at atrue anomaly of 315 degrees. We also report on the results of

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numerical modeling analyses of the morphological evolution of allthree objects aimed at assessing both the properties of theircurrent active episodes and changes in activity strength from oneepoch to the next to help constrain the active lifetimes of MBCs, akey parameter for inferring the total number of MBCs in theasteroid belt from survey results. This work was supported by theNASA Solar System Observations program under GrantNNX16AD68G.

Author(s): Henry H. Hsieh , Masateru Ishiguro , YoonyoungKim , Matthew M. Knight , Zhong-Yi Lin , Marco Micheli ,Nicholas Moskovitz , Scott S. Sheppard , Audrey Thirouin ,Chadwick TrujilloInstitution(s): 1. Carnegie Inst. of Washington, 2. ESA SSA-NEO Coordination Centre, 3. Lowell Observatory, 4. NationalCentral University, 5. Northern Arizona University, 6. PlanetaryScience Institute, 7. Seoul National University, 8. University ofMaryland

305.11 – Ex-dormant comets that come back to life:a search of reactivated cometsDormant or near-dormant short-period comets can unexpectedlyregain the ability to eject dust. In many known cases, theresurrection is short-lived and lasts less than one orbit. However,it is possible that some resurrected comets can remain active inlater perihelion passages. Here we conduct a search in thearchival images of various facilities to look for these “reactivated”comets. We identify two candidates, 297P/Beshore and332P/Ikeya-Murakami, both of which were found to be inactiveor weakly active in the previous orbit before their discovery. Wederive a reactivation rate of 0.007 events per comet per orbit,which implies that typical short-period comets only becometemporarily dormant a few times or less. Smaller comets areprone to rotational instability and may undergo temporarydormancy more frequently. Next generation high-cadence surveysmay find more reactivation events of these comets.

Author(s): YE Quan-ZhiInstitution(s): 1. Caltech

305.12 – Modeling the Thermodynamic Propertiesof the Inner Comae of CometsIntroduction: Modeling is central to understand the importantproperties of the cometary environment. We have developed acomet model, SUISEI, that self-consistently includes the relevant

physicochemical processes within a global modeling framework,from the porous subsurface layers of the nucleus to theinteraction with the solar wind. Our goal is to gain valuableinsights into the intrinsic properties of cometary nuclei so we canbetter understand observations and in situ measurements.SUISEI includes a multifluid, reactive gas dynamics simulation ofthe dusty coma (ComChem) and a suite of other couplednumerical simulations. This model has been successfully appliedto a variety of comets in previous studies over the past threedecades. We present results from a quantitative study of thethermodynamic properties and chemistry of cometary comae as afunction of cometocentric and heliocentric distance to aid ininterpretation of observations and in situ measurements ofcomets. Results and Discussion: ComChem solves the fluid dynamicequations for the mass, momentum, and energy of three neutralfluids (H, H , and the heavier bulk fluid), ions, and electrons. Inthe inner coma, the gas expands, cools, accelerates, andundergoes many photolytic and gas-phase chemical reactionstracking hundreds of sibling species. The code handles thetransition to free molecular flow and describes the spatialdistribution of species in the coma of a comet. Variations ofneutral gas temperature and velocity with cometocentric distanceand heliocentric distance for a comet approaching the Sun from2.5 to 0.3 AU are presented. Large increases in the gastemperatures (>400 K) due to photolytic heating in the comawithin ~0.5 AU are noted, with dramatic effects on the chemistry,optical depth, and other coma properties. Results are comparedto observations when available. Conclusions: SUISEI has proven to be a unique and valuablemodel to understand the relevant physical processes andproperties of small Solar System bodies, including near-Suncomets and asteroids. Acknowledgments: This work was supported by FAPESPunder Grant No. 2015/03176–8 and the National ScienceFoundation Planetary Astronomy Program Grant No. 0908529.

Author(s): Daniel C. BoiceInstitution(s): 1. Scientific Studies and Consulting

306.01 – Ceres’ Evolution and PotentialHabitability Dawn’s observations at Ceres confirm it is a volatile-rich bodythat has undergone ice-rock differentiation and global alteration[1-4], indicating that, as predicted by pre-Dawn thermochemicalmodels, Ceres harbored an ancient subsurface ocean [5,6].Density and shape data indicate that at present, Ceres has a crustcomposed of silicate, salts, clathrates and ≤ 35% water ice,overlying a denser core of hydrated silicates [7,8,9,10], whereasthe original ice-dominated outer shell was likely lost to impact-induced sublimation early in Ceres’ history [11]. The interiorstructure constrains the maximum internal temperature to havebeen only a few hundred degrees [9]; however, rather thanindicating a late formation for Ceres, it may indicate thatcirculation of fluids within Ceres modulated the temperature[12].The extent and longevity of the ocean are debatable;however, the modern surface of Ceres shows evidence of brineextrusion [e.g., 13], indicating at least pockets of subsurface liquidremain. Carbonates are found to dominate the composition of thebrightest deposits on the surface, attesting to transport ofcrystallized brine material to the surface [14]. These multiple linesof evidence point to a warm aqueous subsurface environmentwith complex chemistry early in Ceres’ history and processes thatexchanged material between the muddy ocean layer and thesurface. Such history and the presence of organic material inlocalized deposits [15, 16] make Ceres an enticing target for futureexploration.

[1] Russell et al., Science, 2016 [2] Prettyman et al., Science, 2017[3] De Sanctis et al., 2015 10.1038/nature18290 [4] Ammannitoet al., Science, 2016 [5] McCord and Sotin, JGR, 2005 [6]Castillo-Rogez and McCord, Icarus, 2010 [7] Park et al., Nature,2016 [8] Ermakov et al., JGR, 2017 [9] Fu et al., EPSL, 2017 [10]Bland et al., Nat. GeoSci., 2016 [11] Castillo-Rogez et al., LPSC,2016 [12] Travis et al., Icarus, subm. [13] Ruesch et al., Science,2106 [14] De Sanctis et al., Nature, 2016 [15] De Sanctis et al.,Science, 2017 [16] Marchi et al., this meeting. Acknowledgements: Part of this work is being carried out at theJet Propulsion Laboratory, California Institute of Technology,under contract to NASA.

Author(s): Carol Anne Raymond , Eleonora Ammannito ,Michael T. Bland , Julie Castillo-Rogez , Maria Cristina DeSanctis , Anton Ermakov , Roger Fu , Thomas McCord , RyanPark , Thomas H. Prettyman , Ottaviano Ruesch , ChristopherT. RussellInstitution(s): 1. ASI, 2. Bear Fight Institute, 3. CaliforniaInstitute of Technology, 4. ESTEC, 5. IAPS, 6. LDEO/ColumbiaUniv, 7. PSI, 8. UCLA, 9. USGSContributing team(s): Dawn Team

306.02 – On the origin of the organic-rich materialon Ceres

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Presentation of Carl Sagan Medal and Gerard P. Kuiper Prize

308 – Gerard P. Kuiper Prize: Using the Tools of the Trade to Understand PlasmaInteractions at Jupiter and Saturn, Margaret Kivelson (UCLA & Univ. of Michigan)

The detection of localized, organic-rich material on Ceres [1]poses an interesting conundrum. Either the organic-rich materialhas an exogenous origin, and thus it has been delivered to Ceresafter its formation; or it has an endogenous origin, and thus it hasbeen synthesized and/or concentrated in a specific location onCeres via internal processes. Both scenarios have shortfalls, indicating we may ultimately bemissing how organic matter has been formed, transported andreworked in solar system objects. The very location of Ceres at theboundary between the inner and outer solar system, and itsintriguing composition characterized by clays, sodium- andammonium-carbonates [2], suggest Ceres experienced a verycomplex chemical evolution. The role of organics in this evolutionis not fully understood, with important astrobiologicalimplications [3]. Here we investigate the viability of organics delivery to Ceres viaasteroidal/cometary impactors. We will present iSALE shockphysics code [4-5] simulations that explore a range of impactparameters, such as impactor sizes and velocities, and discuss thelikelihood of organics delivery. We find that comet-likeprojectiles, with relatively high impact velocities, are expected tolose almost all of their organics due to shock compression.Asteroidal-like impactors, with lower incident velocities, canretain 20-30% of their pre-impact organic material duringdelivery, especially for small impactors and very oblique impactangles. However, the spatial distribution of organics on Ceresseems difficult to reconcile with delivery from small main beltasteroids. These findings corroborate an endogenous origin forthe organics on Ceres.

[1] De Sanctis M. C. et al. Science 355, 2016. [2] De Sanctis M. C.et al. Nature 536, 2016. [3] Castillo-Rogez J. C. et al. PlanetaryScience Vision 2050 Workshop 2017 (LPI Contrib. No. 1989). [4]Amsden A. et al. LANL Report, LA-8095, 1980. [5] Collins G. S. etal. MAPS 39, 2004.

Author(s): Simone Marchi , Timothy Bowling , MariaCristina De SanctisInstitution(s): 1. Istituto Nazionale d'Astrofisica, 2. SouthwestResearch Institute, 3. University of Chicago

306.03 – Determining Ceres’ Moment-of-Inertiafrom its Degree-2 Gravity and TopographyCeres’ measured degree-2 zonal gravity, J , is smaller by about10% than that derived assuming Ceres’ rotational flattening, asmeasured by Dawn, is hydrostatic. Irrespective of Ceres’ radialdensity variation, as long as its internal structure is hydrostaticthe J predicted from the shape model is consistently larger thanmeasured. As an explanation, we have previously suggested thatCeres’ current shape may be a fossil remnant of faster rotation inthe geologic past [Mao and McKinnon, 47 LPSC, 2016]. Wepropose that up to ~7% of Ceres’ previous spin angularmomentum has been removed by dynamic perturbations such asa random walk due to impacts or a loss of satellite that slowedCeres spin as it tidally evolved outward. Alternatively, deep seateddensity anomalies, such as caused by convection or upwelling,

could explain Ceres’ unusual gravity/topography relationship atdegree-2 (the sectorial admittance is negative), as long as thelithosphere is sufficiently strong or thick to limit isostaticcompensation. We consider a formal degree-2 admittancesolution, from which we infer a range of possible non-hydrostaticcontributions to J . Ultimately, we conclude that somecombination of a faster paleospin and deeper, uncompensatedmass or masses is the most likely explanation overall, which setsuseful limits on Ceres’ average moment of inertia [Mao andMcKinnon, submitted]. The normalized mean hydrostaticmoments-of-inertia (NMOI) derived for the two explanations –faster paleospin and deep-seated density anomalies – range from0.375 for deep seated density anomalies at today’s spin to lowervalues for faster paleospins, reaching 0.353 ± 0.009 (3σ) for apurely faster paleospin explanation (the uncertainty derivingfrom the uncertainty in Ceres’ oblateness). In principle, modelingCeres’ topographic compensation (isostasy) at higher degrees andorder can further pin down the deep-seated contribution and thetrue paleospin period and hydrostatic NMOI.

Author(s): William B. McKinnon , Xiaochen MaoInstitution(s): 1. Washington Univ. in St. Louis

306.04 – Using Dawn to Observe SEP Events Past 2AUThe launch of the STEREO spacecraft provided much insight intothe longitudinal and radial distribution of solar energetic particles(SEPs) relative to their origin site. However, almost all of theobservations of SEP events have been made exclusively near 1 AU.The Dawn mission, which orbited around Vesta before arriving atCeres, provides an opportunity to analyze these events at muchfurther distances. Although Dawn's Gamma Ray and NeutronDetector (GRaND) is not optimized for SEP characterization, it issensitive to protons greater than 4 MeV, making it capable ofdetecting a solar energetic particle event in its vicinity. Solarenergetic particles in this area of the solar system are importantas they are believed to cause sputtering at bodies such as Ceresand comets (Villarreal et al., 2017; Wurz et al., 2015). In thisstudy, we use Dawn’s GRaND data from 2011-2015 when Dawnwas at distances between 2-3 AU. We compare the SEP eventsseen by Dawn with particle measurements at 1 AU usingSTEREO, Wind, and ACE to understand how the SEP eventsevolved past 1 AU. References: Villarreal, M. N., et al. (2017), The dependence of the Cereanexosphere on solar energetic particle events, Astrophys. J. Lett.,838, L8. Wurz, P. et al. (2015), Solar wind sputtering of dust on the surfaceof 67P/Churyumov-Gerasimenko, A&A, 583, A22.

Author(s): Michaela Villarreal , Christopher T. Russell ,Thomas H. PrettymanInstitution(s): 1. Planetary Science Institute, 2. UCLA

308.01 – Using the tools of the trade to understandplasma interactions at Jupiter and SaturnFor more than half a century, we have been learning howmagnetospheres work. Fluid motions and electromagneticinteractions combine to produce the plasma and fieldenvironment of a planet. Kinetic responses often control thedynamics. Initial descriptions of the terrestrial magnetospherewere often theoretical (e.g., Chapman and Ferraro, Dungey)before an explosion of spacecraft data provided an atlas of thesystem and its temporal variations. The basic structure anddynamics of the terrestrial magnetosphere are now largelyunderstood. A different situation exists for the magnetospheres ofJupiter, Saturn, and their moons. Data acquired from spacecraft

flybys or from orbit have characterized many aspects of thesesystems, but measurements are far more limited than at Earthboth in space and in time. Even after Cassini’s mission to Saturnand Juno’s prime mission at Jupiter have ended, large regions inthe plasma environments of these planets will remain unexplored.No monitors are available to characterize the upstream solarwind. Theory is challenged by the complexity introduced bydynamical effects of the planets’ rapid rotation and the unfamiliarparameter regimes governing interactions with their large moons.Simulation has come to the rescue, providing computationalmodels designed to incorporate the effects of rotation or todescribe moon-magnetosphere interactions. Yet simulations mustbe viewed with appropriate skepticism as they invariably require

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309 – Plenary Talk: The Long-Term Effects of Racial Microaggressions on People ofColor in STEM, William Smith (University of Utah)

310 – Plenary Talk: Aromatic, Alphatic, Enigmatic: The Chemistry of Titan, Sarah Hörst(Johns Hopkins Univ.)

400 – Mars: Surface

some compromise with reality. This talk will describe a symbioticapproach to understanding the dynamics of giant planetmagnetospheres and the plasma interactions betweenmagnetospheric plasma and large moons. Data acquired along aspacecraft trajectory are compared with values extracted from avirtual spacecraft moving through the same path in thesimulation. If results are similar, we use the simulation to identifythe processes responsible for puzzling aspects of the signatures. If

results differ, modifications of the simulation, such as changedboundary conditions, can improve agreement and provide moreconvincing insight into the properties of the systems.

Author(s): Margaret G. KivelsonInstitution(s): 1. UCLA

309.01 – The Long-Term Effects of RacialMicroaggressions on People of Color in STEMPeople of Color experience acute or chronic stress fromdiscriminatory treatment and racial microaggressions, decreasingtheir biopsychosocial health. Racial microaggressions include butare not limited to merciless and mundane exclusionary messages,being treated as less than fully human, and civil and human rightsviolations. Racial microaggressions are key to understandingincreases in Racial Battle Fatigue (Smith, 2004) resulting fromthe psychological and physiological stress that raciallymarginalized individuals/groups experience in response tospecific race-related interactions between them and thesurrounding dominant environment. Race-related stress taxesand exceeds available resilient coping resources for People ofColor, while many Whites easily build sociocultural and economicenvironments and resources that shield them from race-basedstress and threats to their racial entitlements.

What is at stake, here, is the quest for equilibrium versusdisequilibrium in a society that marginalizes human beings into

substandard racial groups. Identifying and counteracting thebiopsychosocial and behavioral consequences of actual orperceived racism, gendered-racism, and Racial Battle Fatigue is apremier challenge of the 21st Century. The term "racialmicroaggressions" was introduced in the 1970's to helppsychiatrists and psychologists understand the enormity andcomplications of the subtle but constant racial blows faced byPeople of Color. Today, racial microaggressions continue tocontribute to the negative workplace experiences of women,people of color, and other marginalized groups in astronomy andplanetary science (Clancy et al. 2017). This presentation will focuson the definition, identification, and long-term effects of racialmicroaggressions and the resultant racial battle fatigue in STEMwork environments.

Author(s): William SmithInstitution(s): 1. University of Utah

310.01 – Aromatic, Alphatic, Enigmatic: TheChemistry of TitanThe extraordinary complexity of Titan’s atmospheric chemistryfar surpasses that of any other solar system atmosphere. With itsthick N atmosphere and stable bodies of liquid on its surface,Titan also possesses many physical processes that are similar tothose that occur on Earth. The connection between Titan’s surfaceand atmosphere is unique in our solar system; atmosphericchemistry produces materials that are deposited on the surfaceand subsequently altered by surface-atmosphere interactionssuch as aeolian and fluvial processes resulting in the formation ofextensive dune fields and expansive lakes and seas. Titan’satmosphere is favorable for organic haze formation, whichcombined with the presence of some oxygen-bearing moleculesindicates that Titan’s atmosphere may produce molecules ofprebiotic interest. The combination of organics and liquid, in the

form of water in a subsurface ocean and methane/ethane in thesurface lakes and seas, means that Titan may be the ideal place inthe solar system to test ideas about habitability, prebioticchemistry, and the ubiquity and diversity of life in the universe. Iwill review our current understanding of chemistry on Titanforged from the powerful combination of Earth-basedobservations, remote sensing and in situ spacecraftmeasurements, laboratory experiments, and models. I willconclude with some of the questions that remain after Cassini-Huygens.

Author(s): Sarah HorstInstitution(s): 1. Johns Hopkins University

400.01 – Regional variations in the observedmorphology and activity of martian linear gulliesThe formation mechanism for martian linear gullies has beenmuch debated, because they have been suggested as possibleevidence of liquid water on Mars. This class of dune gullies isdefined by long (up to 2 km), narrow channels that are relativelyuniform in width, and range in sinuosity index. Unlike othergullies on Earth and Mars that end in depositional aprons, lineargullies end in circular depressions referred to as terminal pits.This particular morphological difference, along with the difficultyof identifying a source of water to form these features, has led toseveral ‘dry’ hypotheses. Recent observations on the morphology,distribution, and present-day activity of linear gullies suggeststhat they could be formed by subliming blocks of seasonal CO ice(“dry ice”) sliding downslope on dune faces. In our study, weaimed to further constrain the possible mechanism(s) responsiblefor the formation of linear gullies by using HiRISE images tocollect morphological data and track seasonal activity withinthree regions in the southern hemisphere-Hellespontus (~45°S,40°E), Aonia Terra (~50°S, 290°E), and Jeans (~70°S, 155°E)over the last four Mars years. General similarities in these

observations were reflective of the proposed formation process(sliding CO blocks) while differences were correlated withregional environmental conditions related to the latitude orgeneral geologic setting. This presentation describes the observedregional differences in linear gully morphology and activity, andinvestigates how environmental factors such as surface propertiesand local levels of frost may explain these variations while stillsupporting the proposed model. Determining the formationmechanism that forms these martian features can improve ourunderstanding of both the climatic and geological processes thatshape the Martian surface.

Author(s): Kimberly Marie Morales , Serina Diniega , MiaAustria , Vincent OchoaInstitution(s): 1. Jet Propulsion Laboratory, CaliforniaInstitute of Technology, 2. Arizona State University , 3.California Institute of Technology, 4. University of SouthernCaliforniaContributing team(s): HiRISE Science and Instrument Team

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400.02 – Automated Mapping andCharacterization of RSL from HiRISE data withMAARSLRecurring slope lineae (RSL) are narrow (0.5–5m) low-albedofeatures on Mars that recur, fade, and incrementally lengthen onsteep slopes throughout the year. Determining the processes thatgenerate RSL requires detailed analysis of high-resolution orbitalimages to measure RSL surface properties and seasonal variation.However, conducting this analysis manually is labor intensive,time consuming, and infeasible given the large number ofrelevant sites. This abstract describes the Mapping andAutomated Analysis of RSL (MAARSL) system, which wedesigned to aid large-scale analysis of seasonal RSL properties.MAARSL takes an ordered sequence of high spatial resolution,orthorectified, and coregistered orbital image data (e.g., MROHiRISE images) and a corresponding Digital Terrain Model(DTM) as input and performs three primary functions: (1) detectand delineate candidate RSL in each image, (2) compute statisticsof surface morphology and observed radiance for each candidate,and (3) measure temporal variation between candidates inadjacent images. The main challenge in automatic image-based RSL detection isdiscriminating true RSL from other low-albedo regions such asshadows or changes in surface materials is . To discriminate RSLfrom shadows, MAARSL constructs a linear illumination modelfor each image based on the DTM and position and orientation ofthe instrument at image acquisition time. We filter out any low-albedo regions that appear to be shadows via a least-squares fitbetween the modeled illumination and the observed intensity ineach image. False detections occur in areas where the 1m/pixelHiRISE DTM poorly captures the variability of terrain observedin the 0.25m/pixel HiRISE images. To remove these spuriousdetections, we developed an interactive machine learninggraphical interface that uses expert input to filter and validate theRSL candidates. This tool yielded 636 candidates from a well-studied sequence of 18 HiRISE images of Garni crater in VallesMarineris with minimal manual effort. We describe our analysisof RSL candidates at Garni crater and Coprates Montes andongoing studies of other regions where RSL occur.

Author(s): Brian Bue , Kiri Wagstaff , David StillmanInstitution(s): 1. Jet Propulsion Laboratory, 2. SouthwestResearch Institute

400.03 – Nonlinear Spectral Mixture Modeling toEstimate Water-Ice Abundance of Martian RegolithWe present a novel technique to estimate the abundance of water-ice in the Martian permafrost using Phoenix Surface StereoImager multispectral data. In previous work, Cull et al. (2010)estimated the abundance of water-ice in trenches dug by the MarsPhoenix lander by modeling the spectra of the icy regolith usingthe radiative transfer methods described in Hapke (2008) withoptical constants for Mauna Kea palagonite (Clancy et al., 1995)as a substitute for unknown Martian regolith optical constants.Our technique, which uses the radiative transfer methodsdescribed in Shkuratov et al. (1999), seeks to eliminate theuncertainty that stems from not knowing the composition of theMartian regolith by using observations of the Martian soil beforeand after the water-ice has sublimated away. We use observationsof the desiccated regolith sample to estimate its complex index ofrefraction from its spectrum. This removes any a prioriassumptions of Martian regolith composition, limiting our freeparameters to the estimated real index of refraction of the dryregolith at one specific wavelength, ice grain size, and regolithporosity. We can then model mixtures of regolith and water-ice,fitting to the original icy spectrum to estimate the ice abundance.To constrain the uncertainties in this technique, we performedlaboratory measurements of the spectra of known mixtures ofwater-ice and dry soils as well as those of soils after desiccationwith controlled viewing geometries. Finally, we applied thetechnique to Phoenix Surface Stereo Imager observations andestimated water-ice abundances consistent with pore-fill in thenear-surface ice. This abundance is consistent with atmosphericdiffusion, which has implications to our understanding of the

history of water-ice on Mars and the role of the regolith at highlatitudes as a reservoir of atmospheric H O.

Author(s): Szilard Gyalay , Kathryn Chu , Eldar Zeev NoeDobreaInstitution(s): 1. PSI, 2. UC Berkeley, 3. UCSC

400.04 – The Formation of Frost and Liquid Brineson Spacecraft Materials at Mars EnvironmentalConditionsThere is evidence that frost formed on the camera calibrationtarget of the Opportunity Rover [1], and that frozen brinesplashed on the struts of the Phoenix lander during landingmelted, producing droplets of liquid brine [2]. Moreover, there isevidence that tiny amounts of frost might have formed at the MSLlanding site, early in the morning during the coldest winter sols[3]. The Michigan Mars Environmental Chamber (MMEC) is capableof simulating temperatures ranging from ~90 to 500 K,atmospheric pressures ranging from ~10 to 10 Pa, and relativehumidity ranging from less than 1% to 100%. The MMEC is alsocapable of simulating the diurnal and seasonal cycles of the Marspolar, mid-latitudes, and equatorial regions (including MarsSpecial Regions). Moreover, the MMEC is equipped withinstruments to study the formation of frost and liquid brines[4,5]. We use the MMEC to study the formation of frost and brinedroplets on spacecraft materials. Our laboratory experimentsindicate that frost forms on spacecraft materials at Marsenvironmental conditions. They also indicate that small amountsof liquid brine could form on spacecraft surfaces if salts arepresent (e.g., deposited with dust aerosols or splashed duringlanding) when frost forms. These results have importantimplications for planetary protection. Our main goal is to identify the spacecraft materials on whichfrost and liquid brines are most likely and least likely to form atthe environmental conditions created by a Mars lander. This willimprove our understanding of forward contamination so thatstandards for spacecraft fabrication and operations can be refinedin order to minimize planetary contamination. References: [1] Landis, G. A. (2007). Lunar Planet. Sci. Conference 38, 2423. [2] Rennó, N. O., et al. (2009). J. Geophys. Res.: Planets (1991–2012), 114(E1). [3] Martínez, G. M., et al. (2016). Icarus, 280, 93-102. [4] Fischer, E., et al. (2014). Geophys. Res. Lett. 41(13), 4456-4462. [5] Fischer, E., et al. (2016). Astrobiology, 16(12), 937-948.

Author(s): Erik Fischer , German Martinez , DanielNeamati , Nilton O. RennoInstitution(s): 1. University of Michigan

400.05 – The Effect of Mars-relevant Minerals onthe Water Uptake of Magnesium Perchlorate andImplications for the Near-surface of MarsThe water uptake and release by hygroscopic salts such asperchlorate has been well studied in the decade since they werefirst discovered on the surface of Mars. However, there have beenfew studies on the effect of the insoluble regolith minerals on thiswell documented interaction of perchlorate and water vapor. Inthis work, we investigate the effect that two insoluble Mars-relevant minerals, montmorillonite and Mojave Mars Simulant(MMS), have on the water uptake (deliquescence), ice formation,and recrystallization (efflorescence) of pure magnesiumperchlorate. We studied mixtures of equal parts (by mass)magnesium perchlorate hexahydrate and either montmorilloniteor MMS. Although montmorillonite and MMS are insolubleminerals that may serve as nuclei for either ice nucleation or saltefflorescence, we find that these minerals did not affect any of the

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401 – Comets: Dynamics, Origins and Theory

phase transitions of magnesium perchlorate. The salt-mineralmixture behaved like pure magnesium perchlorate in all cases,with stable deliquescence as well as metastable brinesupersaturation and supercooling observed. Experiments wereperformed in both N and CO atmospheres, with no detectabledifference. We use data from the Rover EnvironmentalMonitoring Station instrument on MSL and from the Thermaland Electrical Conductivity Probe instrument on Phoenix, as wellas modeling of the shallow subsurface near the rover and lander,to determine the likelihood of liquid water and water ice at GaleCrater and the Phoenix landing site.

Author(s): Katherine Primm , Raina Gough , Edgard G.Rivera-Valentin , Margaret TolbertInstitution(s): 1. Arecibo Observatory (USRA), 2. University ofColorado

400.06 – Oxychlorine species in Gale Crater andbroader implications for Mars

Of 15 samples analyzed to date, the Sample Analysis at Mars(SAM) instrument on the Mars Science Laboratory (MSL) hasdetected oxychlorine compounds (perchlorate or chlorate) in 12samples. The presence of oxychlorine species is inferred from therelease of oxygen at temperatures <600 °C and HCl between 350-850 °C when a sample is heated to 850 °C. The O releasetemperature varies with sample, likely caused by differentcations, grain size differences, or catalytic effects of otherminerals. In the oxychlorine-containing samples, perchlorateabundances range from 0.06 ± 0.03 to 1.15 ± 0.5 wt% Cl Oequivalent. Comparing these results to the elemental Clconcentration measured by the Alpha Particle X-ray Spectrometer(APXS) instrument, oxychlorine species account for 5-40% of thetotal Cl present.

The variation in oxychlorine abundance has implications for theirproduction and preservation over time. For example, the JohnKlein (JK) and Cumberland (CB) samples were acquired within afew meters of each other and CB contained ~1.2 wt% Cl Oequivalent while JK had ~0.1 wt%. One difference between thetwo samples is that JK has a large number of veins visible in thedrill hole wall, indicating more post-deposition alteration and

removal. Finally, despite Cl concentrations similar to previous samples, thelast three Murray formation samples (Oudam, Marimba, andQuela) had no detectable oxygen released during pyrolysis. Thiscould be a result of oxygen reacting with other species in thesample during pyrolysis. Lab work has shown this is likely to haveoccurred in SAM but it is unlikely to have consumed all the Oreleased. Another explanation is that the Cl is present aschlorides, which is consistent with data from the ChemCam(Chemical Camera) and CheMin (Chemistry and Mineralogy)instruments on MSL. For example, the Quela sample has ~1 wt%elemental Cl detected by APXS, had no detectable O released,and halite (NaCl) has been tentatively identified in CheMin X-raydiffraction data. These data show that oxychlorines are likely globally distributedon Mars but the distribution is heterogenous depending on theperchlorate formation mechanism (production rate), burial, andsubsequent diagenesis.

Author(s): Paul Douglas Archer , Joanna C Hogancamp ,Douglas W Ming , Brad Sutter , Richard V Morris , BentonClark , Paul R Mahaffy , Cherie Achilles , James J. Wray , RalfGellert , Albert Yen , David F Blake , David T Vaniman ,Daniel P Glavin , Jennifer L Eigenbrode , Melissa G Trainer ,Rafael Navarro-González , Christopher P. McKay , CarolineFreissinet , Peter MartinInstitution(s): 1. Department of Geosciences, University ofArizona, 2. Division of Geological and Planetary Sciences,Caltech, 3. Geocontrols Systems Inc, 4. Georgia Institute ofTechnology, 5. Instituto de Ciencias Nucleares, UniversidadNacional Autonoma de Mexico, 6. JACOBS, NASA JohnsonSpace Center, 7. Laboratoire Atmosphères, Milieux,Observations Spatiales, Centre National de la RechercheScientifique, 8. NASA Ames Research Center, 9. NASA GoddardSpace Flight Center, 10. NASA Jet Propulsion Laboratory, 11.NASA Johnson Space Center, 12. Planetary Science Institute, 13.Space Science Institute, 14. University of Guelph

401.01 – Origin and Evolution of Short-PeriodCometsComets are icy objects that orbitally evolve from the trans-Neptunian region (the Kuiper belt and beyond) into the innerSolar System, where they are heated by solar radiation andbecome active due to sublimation of water ice. Here we performend-to-end simulations in which cometary reservoirs are formedin the early Solar System and evolved over 4.5 Gyr. Thegravitational effects of Planet 9 (P9), hypothesized to circle theSun on a wide orbit, are included in some of our simulations.Different models are considered for comets to be active, includinga simple assumption that comets remain active for Np(q)perihelion passages with perihelion distance q<2.5 au. The orbitaldistribution and number of active comets produced in our modelis compared to observations. The orbital distribution of eclipticcomets (ECs) is well reproduced in models with Np(2.5)=500 andwithout P9. With P9, the inclination distribution of model ECs iswider than the observed one. We find that the known Halley-typecomets (HTCs) have a nearly isotropic inclination distribution(with only a slight preference for prograde orbits). In our model,the HTCs appear to be an extension of the population of returningOort-cloud comets (OCCs) to shorter orbital periods. Theinclination distribution of model HTCs becomes broader withincreasing Np, but the existing observational data are not goodenough to constrain Np from orbital fits. Np(2.5)>1000 isrequired to obtain a steady-state population of large active HTCsthat is consistent with observations. To fit the ratio of thereturning-to-new OCCs, by contrast, our model implies thatNp(2.5)<10, possibly because the detected long-period comets aresmaller and much easier to disrupt than observed HTCs.

Author(s): David Nesvorny , David Vokrouhlicky , Henry C.(Luke) Dones , Harold F. Levison , Nathan A. Kaib , AlessandroMorbidelliInstitution(s): 1. Charles University, 2. Nice Observatory,CNRS, 3. SWRI, 4. The University of Oklahoma

401.02 – Can Ecliptic Comets Be Created En Routefrom the Kuiper Belt?The Kuiper Belt is thought to be the reservoir of ecliptic comets(ECs), which include the Jupiter-family comets (JFCs) andCentaurs. ECs are also the main source of Sun-orbiting impactorson the regular moons of the giant planets (Zahnle et al. 2003).Ironically, we still do not know whether the belt, specifically itsScattered Disk, provides enough ECs (Volk and Malhotra 2008).We are investigating whether cometary breakup in the planetaryregion (Fernández 2009) can substantially increase the numberof ECs. In support of this idea, the Kreutz sungrazers may derivefrom a hierarchical series of fragmentation events of a progenitorlong-period comet (e.g., Sekanina and Chodas 2007), and theJFCs 42P and 53P appear to be fragments of a comet that split in1845 (Kresák et al. 1984). On the other hand, although 16P wastidally disrupted by Jupiter in 1886, only one fragment survives. Models of the cometary orbital distribution ignore activity orapply a physical lifetime based on the number of passages within2 or 3 AU of the Sun, where sublimation of water ice occurs(Nesvorný et al. 2017). In reality, some comets (e.g., 29P, Hale-Bopp) are active beyond Jupiter due to volatiles such as CO andCO2 (Womack et al. 2017). 174P/Echeclus underwent a 7-magnitude outburst at 13 AU (Rousselot et al. 2016), and COemission was detected from Echeclus at 6 AU (Wierzchos et al.

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402 – Extrasolar Planets and Systems: Giant Planet Atmospheres I

2017). We will estimate how the number and size distribution ofcomet nuclei change with distance from the Sun due to cometaryactivity and spontaneous disruption, tidal disruption by a giantplanet, and tidal disruption of binaries (Fraser et al. 2017).

We thank the Cassini Data Analysis Program for support.

Fernández Y (2009). Planet. Space. Sci. 57, 1218. Fraser WC, et al. (2017). Nat. Astron. 1, 0088. Kresák L, et al. (1984). IAU Circular 3940. Nesvorný D, et al. (2017). arXiv:1706.07447. Rousselot P, et al. (2016). MNRAS 462, S432. Sekanina, Z, Chodas, PW (2007). Astrophys. J. 663, 657. Volk K, Malhotra R (2008). Astrophys. J. 687, 714. Wierzchos K, Womack M, Sarid G. (2017). Astron. J. 153, id 230. Womack M, Sarid G, Wierzchos, K (2017). Publ. Astron. Soc. Pac.129, 031001. Zahnle K, et al. (2003). Icarus 163, 263.

Author(s): Henry C. (Luke) Dones , Maria Womack , DavidNesvorny , Edward B. Bierhaus , Kevin Zahnle , Stuart J.Robbins , William Bottke , Jose Alvarellos , Patrick HamillInstitution(s): 1. Lockheed Martin Space Systems, 2. NASAAmes Research Center, 3. San José State University, 4.Southwest Research Inst., 5. University of South Florida

401.03 – Rapid evolution of the spin state of comet41P/Tuttle-Giacobini-KresakComet nuclei are small, dynamic objects influenced strongly bytheir individual history, orbit, rotation and inhomogeneity. Massloss due to sublimation can exert a profound influence on thephysical nature of the cometary nucleus, changing the shape, size,and rotation (Jewitt, in Comets II, 2004). The Rosetta mission tocomet 67P showed that these effects are all interrelated (Sierks etal., Science 347, 2015).

Comet 41P/Tuttle-Giacobini-Kresak passed Earth as close as0.142 au in April 2017, allowing observations of the inner comaand an assessment of the rotational state of the nucleus. Weacquired observations of comet 41P between March and May 2017using the 4.3-m Discovery Channel Telescope and theUltraViolet-Optical Telescope (UVOT) on board the Earth-orbiting Swift Gamma Ray Burst Mission. Using CN narrowband imaging and aperture photometry wefound that the apparent rotation period of comet 41P more thandoubled between March and May 2017, increasing from 20 hoursto 50 hours. Measurements of the periodicity in late-March byKnight et al. (CBET 4377, 2017) are consistent with this rate ofincrease. Comet 41P is the ninth comet for which a rotationperiod change has been observed (c.f. Samarasinha et al., inComets II, 2004), but both the fractional change and the rate ofchange of the period far exceed those observed in the othercomets. It is presumably the combination of a long rotationperiod, high surface activity, and a small nucleus that makes 41Phighly susceptible to changes in its rotational state. Extrapolating the comet’s rotation period using its current gasproduction rates and a simple activity model suggests that thenucleus will continue to spin down, possibly leading to an excitedspin state in the next few apparitions. Finally, 41P is known for itslarge outbursts, and our extrapolation suggest that the comet’srotation period may have been close to the critical period forsplitting in 2001, when it exhibited two significant outbursts.

Author(s): Dennis Bodewits , Tony Farnham , Matthew M.Knight , Michael S. KelleyInstitution(s): 1. University of Maryland

402.01 – KELT-9b: An Example of AtmosphericExtremesWe discuss the characteristics of KELT-9b, the hottest and mostirradiated hot Jupiter that has been found to date. KELT-9b hasan orbital period of ~1.5 days around a rapidly rotating A0 hoststar. The combination of short orbital period and hot (effectivetemperature of ~9,600 K) host make the hot Jupiter, KELT-9b,ideally suited for future study of an atmosphere under extremeirradiation.

The planet was confirmed with high-quality primary transitobservations in multiple bands and found to have a detectablesecondary eclipse in the far-red optical (z) that indicates abrightness temperature of ~4600 K, and therefore poor heatredistribution to the night side when compared to the equilibriumtemperature of ~3800 K. Further confirmations of planetary werederived from an absence of companions seen in deep AOobservations, radial velocity detection of the small reflex motionof the star due to the planet, and finally from the detection of adefinite Doppler tomographic signal.

The confirmation observations of KELT-9b showed it to be aplanet with a radius and mass of ~1.8 Jupiter radii and ~2.7Jupiter masses. We find the planet to be in a near-polar orbit.This should lead to a detectable orbital precession within just afew years. The high irradiation from the host star combined withthe short orbital period, extreme planetary temperature, largeplanet-to-star radius ratio, and large atmospheric scale height~1000 km, make KELT-9b a prime target for future studies ofplanetary atmospheres. It is expected that such an extremeenvironment will show equally extreme but detectablephotochemistry for future investigators.

Author(s): Michael D. Joner , B. Scott Gaudi , JoshuaPepper , Keivan G. StassunInstitution(s): 1. Brigham Young Univ., 2. Lehigh University,3. Ohio State University, 4. Vanderbilt UniversityContributing team(s): KELT Science Team, KELT Follow-upNetwork

402.02D – Dynamics of Tidally Locked, UltrafastRotating AtmospheresTidally locked gas giants, which exhibit a novel regime of day-night thermal forcing and extreme stellar irradiation, are typicallyin several-day orbits, implying slow rotation and a modest role forrotation in the atmospheric circulation. Nevertheless, there exist aclass of gas-giant, highly irradiated objects - brown dwarfsorbiting white dwarfs in extremely tight orbits - whose orbital andhence rotation periods are as short as 1-2 hours. Spitzer phasecurves and other observations have already been obtained for thisfascinating class of objects, which raise fundamental questionsabout the role of rotation in controlling the circulation. So far,most modeling studies have investigated rotation periodsexceeding a day, as appropriate for typical hot Jupiters. In thiswork we investigate the dynamics of tidally locked atmospheres inshorter rotation periods down to about two hours. Withincreasing rotation rate (decreasing rotation period), we showthat the width of the equatorial eastward jet decreases, consistentwith the narrowing of wave-mean-flow interacting region due todecrease of the equatorial deformation radius. The eastward-shifted equatorial hot spot offset decreases accordingly, and thewestward-shifted hot regions poleward of the equatorial jetassociated with Rossby gyres become increasingly distinctive. Athigh latitudes, winds becomes weaker and more geostrophic. Theday-night temperature contrast becomes larger due to thestronger influence of rotation. Our simulated atmospheres exhibitsmall-scale variability, presumably caused by shear instability.Unlike typical hot Jupiters, phase curves of fast-rotating modelsshow an alignment of peak flux to secondary eclipse. Our results

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Author(s): Xianyu Tan , Adam P. ShowmanInstitution(s): 1. University of Arizona

402.03 – The effects of disequilibrium carbonchemistry in general circulation models of hotJupitersAbundances of methane (CH4) and carbon monoxide (CO) areexpected to be in disequilibrium in the photospheres of hotJupiter exoplanets due to transport-induced quenching. It hasbeen proposed that including this effect in general circulationmodels (GCMs) could resolve the mismatch between models andthe observed 4.5 micron phase curves of hot Jupiters HD 189733band HD 209458b. We modified the SPARC/MITgcm to mimic quenched carbonchemistry by assuming a constant ratio of CH4 to CO to calculatethe opacities. Water abundances are modified accordingly so thatthe number of oxygen atoms is conserved. We ran globalcirculation models of HD 189733b assuming different values ofthe CH4/CO ratio. The change in temperature structure due tothe quenched abundances is significant enough to affect theemission spectra. Thus, the radiative effect of the quenchedabundances should be included in global circulation models We show that including disequilibrium effects does not lower the4.5 micron night side fluxes. If CO is the dominant species, aspredicted by kinetics models, the increased CO opacity is offset bya lower water opacity. In this case, the 4.5 micron band turns outto be a bad diagnostic for disequilibrium carbon chemistry. As aconsequence, disequilibrium carbon chemistry does not provide agood explanation for the small nightside flux observed at 4.5microns in HD 189733b. The 3.6 Spitzer band should be a betterindicator of disequilibrium chemistry. We find that the presenceof quenched abundances always reduces the phase curveamplitude at 3.6 microns compared to the chemical equilibriumcase, such that they are inconsistent with existing observations ofHD 189733b. Therefore, other processes such as the presence ofdrag or night side clouds must be responsible for the shape ofcurrently observed HD 189733b phase curves. We find that observations between 7 and 10 microns are a betterdiagnostic of disequilibrium carbon chemistry in the COdominated regime. Observations with the JWST will providebetter constraints on the disequilibrium processes at play on boththe dayside and the nightside of hot Jupiters.

Author(s): Maria Elisabeth Steinrueck , VivienParmentier , Adam P. ShowmanInstitution(s): 1. University of Arizona

402.04 – BARTTest: Community-StandardRadiative-Transfer Tests I: Forward ModelsAtmospheric radiative transfer codes are used both to predictplanetary spectra and in retrieval algorithms to interpret data.Observational plans, theoretical models, and scientific resultsthus depend on the correctness of these calculations. Yet, thecalculations are complex and the codes implementing them areoften written without modern software-verification techniques.The community needs a suite of test calculations with analytically,numerically, or at least communally verified results. We thereforeoffer the Bayesian Atmospheric Radiative Transfer Test Suite, orBARTTest, a collection of tests offered for community use anddevelopment.

This presentation focuses on forward models. Tests include asingle-line, single layer atmosphere verified by an independentnumerical line-broadening code included with the test, anisothermal atmoshere with hundreds of millions of lines (whichshould emit as a blackbody of the same temperature), andrealistic atmospheres verified by an independent radiativetransfer model.

BARTTest is open-source software. We propose this test suite as astandard for verifying radiative-transfer codes, analogous to the

Held-Suarez test for general circulation models. This work wassupported by NASA Planetary Atmospheres grant NX12AI69Gand NASA Astrophysics Data Analysis Program grantNNX13AF38G.

Author(s): Michael D Himes , Joseph Harrington , PatricioCubillos , Jasmina Blecic , Ryan C ChallenerInstitution(s): 1. New York University Abu Dhabi, 2. SpaceResearch Institute, Austrian Academy of Sciences, 3. Universityof Central Florida

402.05 – Artificial Intelligence in planetaryspectroscopyThe field of exoplanetary spectroscopy is as fast moving as it isnew. Analysing currently available observations of exoplanetaryatmospheres often invoke large and correlated parameter spacesthat can be difficult to map or constrain. This is true for both: thedata analysis of observations as well as the theoretical modellingof their atmospheres. Issues of low signal-to-noise data and large, non-linear parameterspaces are nothing new and commonly found in many fields ofengineering and the physical sciences. Recent years have seenvast improvements in statistical data analysis and machinelearning that have revolutionised fields as diverse astelecommunication, pattern recognition, medical physics andcosmology. In many aspects, data mining and non-linearity challengesencountered in other data intensive fields are directly transferableto the field of extrasolar planets. In this conference, I will discusshow deep neural networks can be designed to facilitate solvingsaid issues both in exoplanet atmospheres as well as foratmospheres in our own solar system. I will present a deep beliefnetwork, RobERt (Robotic Exoplanet Recognition), able to learnto recognise exoplanetary spectra and provide artificialintelligences to state-of-the-art atmospheric retrieval algorithms.Furthermore, I will present a new deep convolutional networkthat is able to map planetary surface compositions using hyper-spectral imaging and demonstrate its uses on Cassini-VIMS dataof Saturn.

Author(s): Ingo WaldmannInstitution(s): 1. University College London

402.06D – A population study of hot JupiteratmospheresIn the past two decades, we have learnt that every star hosts morethan one planet. While the hunt for new exoplanets is on-going,the current sample of more than 3500 confirmed planets reveals awide spectrum of planetary characteristics. While small planetsappear to be the most common, the big and gaseous planets play akey role in the process of planetary formation. We present herethe analysis of 30 gaseous extra-solar planets, with temperaturesbetween 600 and 2400 K and radii between 0.35 and 1.9 Jupiterradii. These planets were spectroscopically observed with theWide Field Camera 3 on-board the Hubble Space Telescope,which is currently one of the most successful instruments forobserving exoplanetary atmospheres. The quality of theHST/WFC3 spatially-scanned data combined with our specialisedanalysis tools, allows us to create the largest and most self-consistent sample of exoplanetary transmission spectra to dateand study the collective behaviour of warm and hot gaseousplanets rather than isolated case-studies. We define a new metric,the Atmospheric Detectability Index (ADI) to evaluate thestatistical significance of an atmospheric detection and findstatistically significant atmospheres around 16 planets. For mostof the Jupiters in our sample we find the detectability of theiratmospheres to be dependent on the planetary radius but not onthe planetary mass. This indicates that planetary gravity is asecondary factor in the evolution of planetary atmospheres. Wedetect the presence of water vapour in all the statisticallydetectable atmospheres and we cannot rule out its presence in theatmospheres of the others. In addition, TiO and/or VO signaturesare detected with 4σ confidence in WASP-76 b, and they are mostlikely present on WASP-121 b. We find no correlation between

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403 – Comet Physical Characteristics: Nuclei and Surfaces

404 – Mercury and The Moon

expected signal-to-noise and atmospheric detectability for mosttargets. This has important implications for future large-scalesurveys.

Author(s): Angelos Tsiaras , Ingo Waldmann , TizianoZingales , Marco Rocchetto , Giuseppe Morello , MarioDamiano , Konstantinos Karpouzas , Giovanna Tinetti , LauraMcKemmish , Jonathan Tennyson , Sergey YurchenkoInstitution(s): 1. Aristotle University of Thessaloniki, 2. UCL

403.01 – The resolved nucleus of Comet SidingSpring (C/2013 A1) in MRO HiRISE imagesComet Siding Spring (C/2013 A1) passed within 140,000 km ofMars on 19 Oct 2014. The MRO spacecraft, in orbit around Mars,used its HiRISE camera to monitor the comet during theencounter, obtaining the first resolved images of the nucleus of adynamically new comet.

MRO observed Siding Spring from 60 hr before, to 15 hr afterclose approach, obtaining 122 images in three different colorfilters. Close approach images, with a spatial scale as small as 138m/pix, reveal an elongated crescent that changes shape over thecourse of the sequence, indicating that we are seeing a ~1 km non-spherical body from different viewpoints as the comet rapidlysweeps past. To better constrain the characteristics of thenucleus, we are performing detailed analyses, including modelingof the inner coma to separate its flux contribution from that of thenucleus. In conjunction with the coma removal, we will model thenucleus as a prolate/triaxial ellipsoid and, combined with theknown illumination and viewing conditions, will use the changingaspect in the images to constrain the size, shape, orientation,albedo and possibly the phase dependence of the nucleus.

In addition to the close approach observations, the images beforeand after close approach capture the coma structure andbrightness. The photometric lightcurve from these images showsvariability with an 8.1 hr period, which is presumed to be therotational modulation of the coma activity. The observedmorphology changes as well, promising to provide a measure ofthe nucleus' spin axis orientation.

We will report on the results from our analyses, and provide thefirst direct measurements of the nucleus of a dynamically newcomet.

Author(s): Tony Farnham , Michael S. Kelley , DennisBodewits , James M BauerInstitution(s): 1. Univ. of Maryland

403.02 – Photometric comparison of smoothregions on 67P/Churyumov-Gerasimenko withother cometary nucleiCorrelating Rosetta data with previous space mission dataenables us to generalize the geological evolutionary process froma single comet to multiple JFCs, a necessary first step towardsunderstanding the geological evolution of JFCs based on missiondata. The ESA/NASA’s Rosetta escorted and observed Comet67P/Churyumov-Gerasimenko from August 2014 to September2016 along its orbit around the Sun from 4 AU pre-perihelion to 4AU post-perihelion. The images of 67P from OSIRIS-NarrowAngle Camera and Wide Angle camera enable us to do detailedphotometric comparison with models we used to study thesurface of other comet nuclei, Comet 19P/Borrelly(by DeepSpace), Comet 81P/Wild 2(by Stardust), Comet 9P/Tempel 1(byDeep Impact and Stardust-NExT) and Comet 103P/Hartley 2(byDeep Impact eXtended Investigation). We use disk-resolvedphotometry as a tool to study the geological evolution of cometarynuclei. We characterized smooth areas on 67P, and correlate

them to the smooth areas on other comets. We performed aninitial identification and preliminary characterization of smoothareas on 67P with Rosetta OSIRIS images, measuring theiralbedos, colors, phase functions, and compare them with those onother cometary nuclei, putting 67P into the context of othercometary nuclei.

Author(s): Xiaoduan Zou , Jian-Yang Li , Michael J. S.BeltonInstitution(s): 1. Belton Space Exploration Initiatives, 2.Planetary Science Institute

403.03D – Physical properties of Jupiter-familycomets and KBOs from ground-based lightcurveobservationsRotational lightcurves are among the most powerful tools to studythe physical characteristics of small bodies in the Solar system.They can be used to constrain their spin rates, shapes, densitiesand compositions. We have developed a method to derive preciselightcurves and phase functions from sparsely sampled data,calibrated using Pan-STARRS stellar magnitudes. We employ thistechnique to characterize the physical properties of JupiterFamily Comets (JFCs) and Kuiper Belt Objects (KBOs). We provide an updated study of the collective properties of JFCsby increasing the sample of comets with well-studied rotationaland surface characteristics. To collect the sample, we reviewedthe properties of 35 previously-studied JFCs and added newlightcurves and phase functions for nine JFCs observed between2004 and 2015. The new extended sample confirms the known cut-off in bulkdensity at ∼0.6 g cm if JFCs are strengthless. For typicaldensity and elongations, we determined that JFCs require tensilestrength of 10-25 Pa to remain stable against rotationalinstabilities. To provide further constraints on the physicalcharacteristics of JFCs we combine these findings with a study ofthe activity-induced spin changes of JFCs. Using the newlyderived albedos and phase functions, we found that the medianlinear phase function coefficient for JFCs is 0.046 mag/deg andthe median albedo is 4.2 per cent. We found evidence for anincreasing linear phase function coefficient with increasingalbedo. In an attempt to relate JFCs to their source populations, wecompare them to KBOs. We performed a magnitude-limitedsurvey of 40 KBOs, observed with the 3.6-m ESO NewTechnology Telescope between 2014 and 2017. This is the firstsurvey with a 4m-class telescope conducted in an entirelyhomogeneous manner (using the same telescope, observingstrategy, and data analysis). This program allows us to relate therotation rates, physical properties and surface characteristics ofJFCs and KBOs in order to test the different hypotheses for theirformation and subsequent evolution.

Author(s): Rosita Kokotanekova , Colin Snodgrass , PedroLacerda , Simon F. GreenInstitution(s): 1. Max Planck Institute for Solar SystemResearch, 2. Open University, 3. Queen’s University Belfast

404.01 – Observations of Mercury’s NeutralHydrogen Exosphere During the MESSENGER

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Because of the difficulty of observing H Lyman α at Mercuryremotely, the MESSENGER mission afforded the first chancesince the Mariner 10 flybys to investigate the neutral hydrogenexosphere of Mercury in detail. Mariner 10 discovered H atMercury, but left many questions about the puzzling temperatureand density distributions unanswered. Sparse observationsduring the MESSENGER flybys of Mercury suggested that the Hexosphere was grossly similar to what was observed by Mariner10, but with higher overall emission levels, and they provided noanswers to the outstanding issues from Mariner 10. Observationsof H Lyman α emission by the Ultraviolet and VisibleSpectrometer (UVVS) component of the Mercury Atmosphericand Surface Composition Spectrometer (MASCS) instrumentonboard MESSENGER were conducted regularly throughout theMESSENGER orbital phase. These observations provide a muchmore complete picture of the H exosphere at Mercury. Wepresent an analysis of the UVVS orbital observations, focusing onthe temporal and spatial distribution of the hydrogen about theplanet. Preliminary models will be shown, and the UVVS data willbe compared and contrasted to the Mariner 10 data to address thelong-outstanding questions about this element of Mercury’scomplex exosphere. Support from the NASA Discovery DataAnalysis Program is gratefully acknowledged.

Author(s): Ronald J. Vervack , Dana Hurley , Wayne R.PryorInstitution(s): 1. Central Arizona College, 2. Johns HopkinsApplied Physics Laboratory

404.02 – Dating Tectonic Activity on Mercury’sLarge-Scale Lobate-Scarp Thrust Faults Mercury’s widespread large-scale lobate-scarp thrust faults revealthat the planet’s tectonic history has been dominated by globalcontraction, primarily due to cooling of its interior. Constrainingthe timing and duration of this contraction provides key insightinto Mercury’s thermal and geologic evolution. We combine twotechniques to enhance the statistical validity of size-frequencydistribution crater analyses and constrain timing of the 1) earliestand 2) most recent detectable activity on several of Mercury’slargest lobate-scarp thrust faults. We use the sizes of cratersdirectly transected by or superposed on the edge of the scarp faceto define a count area around the scarp, a method we call theModified Buffered Crater Counting Technique (MBCCT). Wedeveloped the MBCCT to avoid the issue of a near-zero scarpwidth since feature widths are included in area calculations of thecommonly used Buffered Crater Counting Technique (BCCT).Since only craters directly intersecting the scarp face edgeconclusively show evidence of crosscutting relations, we increasethe number of craters in our analysis (and reduce uncertainties)by using the morphologic degradation state (i.e. relative age) ofthese intersecting craters to classify other similarly degradedcraters within the count area (i.e., those with the same relativeage) as superposing or transected. The resulting crater counts aredivided into two categories: transected craters constrain theearliest possible activity and superposed craters constrain themost recent detectable activity. Absolute ages are computed foreach population using the Marchi et al. [2009] model productionfunction. A test of the Blossom lobate scarp indicates the MBCCTgives statistically equivalent results to the BCCT. We find that allscarps in this study crosscut surfaces Tolstojan or older in age(>~3.7 Ga). The most recent detectable activity along lobate-scarpthrust faults ranges from Calorian to Kuiperian (~3.7 Ga topresent). Our results complement previous relative-age studieswith absolute ages and indicate global contraction continued overthe last ~3-4 Gyr. At least some thrust fault activity occurred onMercury in relatively recent times (<280 Ma).

Author(s): Nadine G. Barlow , Maria E BanksInstitution(s): 1. NASA Goddard Space Flight Center, 2.Northern Arizona Univ.

404.03 – Mercury as the Unaccreted Projectile:Thermal Consequences

Mercury retained substantial volatiles during its formation, in fargreater proportion than the Moon, despite losing ~2/3 of its rockymantle. Its volatile-rich geochemistry would contraindicate agiant impact because it would drive away the volatiles, as in thehypothesis for the Moon. However, the thermal consequences ofMercury formation vary considerably between the two giantimpact scenarios, ‘direct hit’ (DH; Benz et al. 1989) and ‘hit andrun’ (HR; Asphaug and Reufer 2014). Each begins with adifferentiated chondritic proto-Mercury (PM) a bit larger thanMars. In DH, PM gets eroded by a very energetic impactor half itsmass, at ~6-7 times the escape velocity. To remove half of PM’smantle, the post-impact target gets completely shock-vaporizedand is sheared apart into space. The bound remnant in DH wouldexperience a comparable deposition of shock enthalpy, as inMoon formation, and would expand into a much larger volume ofheliocentric space, leading to a dry planet. The bound remnantwill go on to re-accrete much of the silicate mantle that it just lost,another challenge for DH. In HR, PM is the projectile that slamsinto a terrestrial planet twice its size (proto-Venus or proto-Earth). For typical impact angle and speed, a typical outcome is to‘bounce”. But for HR to explain Mercury, PM must avoidaccretion every time it encounters the target, until it is scatteredor migrates away (or is accreted, in which case there is noMercury), leading to multi-HR scenarios. Tides are intense in HRbecause the projectile grazes the target core; gravity does most ofthe work of mantle stripping. Shocks play a secondary role.Whereas in DH the impactor blasts the target inside-out, in HRthe runner emerges relatively unshocked, and undispersed exceptfor losing the gravitationally-unbound material. HR is amechanism for collecting low-shocked remnants, because theintensely shocked material ends up bound to the target orescaping to heliocentric space; little of it is accreted by the runner.We compare single-HR and slower multiple-HR scenarios, withDH scenarios, evaluating enthalpy production within the boundremnant in SPH simulations.

Author(s): Erik Asphaug , Travis Gabriel , Alan Jackson ,Viranga PereraInstitution(s): 1. CPS, U. Toronto, 2. LPL, University ofArizona, 3. SESE, Arizona State University

404.04D – The Wibbly-Wobbly Moon: RotationalDynamics of the Moon After Large ImpactsThe spins of planets are not constant with time; they continuouslyevolve in response to both external and internal forces. One of themost dramatic ways a planet’s spin can change is via impacts.Impacts change the planet’s angular momentum, energy, andmoments of inertia. These changes can have importantconsequences for the geology of the planet. For the well-studiedcase of the Moon, these repercussions include everything fromchanging the orientation of the magnetic field, controlling thegeometry of fault networks, and altering the stability of volatiles(e.g. water ice) in permanently shadowed regions. While previousstudies have investigated the dynamical effects of impacts on theMoon, most use simplistic models for the impact basin formationprocess—often only considering the impulsive change in theMoon’s angular momentum, and occasionally the change in theMoon’s moments of inertia from a simplified basin geometry (e.g.a cylindrical hole surrounded by a cylindrical ejecta blanket).These simplifications obscure some of the subtler and morecomplicated dynamics that occur in the aftermath of an impact.In this work, we present new model results for the rotationaldynamics of the Moon after large, basin-forming impacts. Wecouple iSALE hydrocode simulations with the analytical andnumerical formalisms of rotational dynamics. These simulationsallow us to quantitatively track how different impact processesalter the Moon’s moments of inertia, including basin formation,mantle uplift, impact heating, and ejecta-blanket emplacement.This unique combination of techniques enables us to moreaccurately track the spin of the Moon in the aftermath of theseimpacts, including periods of non-synchronous and non-principal-axis rotation, libration, and long-term reorientation(true polar wander). We find that the perturbation of the Moon’smoments of inertia immediately after impact is several timeslarger than what is expected based on the present-day gravity

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field of the Moon. While this work focuses on the Moon, impactsare a ubiquitous process in our solar system, and the techniquesand results presented here may be applicable to a variety of rocky(and icy) solar system worlds.

Author(s): James Tuttle Keane , Brandon C Johnson ,Isamu Matsuyama , Matthew SieglerInstitution(s): 1. Brown University, 2. California Institute ofTechnology, 3. Planetary Science Institute, 4. University ofArizona

404.05D – Giordano Bruno crater on the Moon:Detection and Mapping of Hydration Features ofEndogenic and/or Exogenic NatureWe analyze high resolution spectral and spatial data from therecent lunar missions and report the presence of strong hydrationfeatures within the inner flank, hummocky floor, ejecta andimpact melt deposits of crater Giordano Bruno. Hydroxyl-bearinglithologies at Giordano Bruno are characterized primarily by aprominent absorption feature near 2800 nm, the band minima ofwhich goes beyond 3000 nm. The hydration features are found tobe associated with low-Ca pyroxene-bearing noritic lithologiesalong the inner crater flanks, whereas similar features are alsoseen within the hummocky crater floor in association withshocked plagioclase-bearing anorthositic lithology. Interestingly,the ejecta blanket is characterized by sharp, narrow featurescentered near 2800 nm similar to the features previouslyreported from Compton-Belkovich volcanic complex and centralpeak of crater Theophilus. The low-Ca pyroxene-bearing rockexposures within the crater inner flanks are characterized by bothpresence and absence of the hydration features. Enhancedhydration is also seen within the ejecta blanket covering thenearby Harkhebi K and J craters. We also analyze the impactmelts and ejecta using radar images at regions interior andexterior to the Giordano Bruno crater rim. Anomalous behaviors of hydration feature associated with low-Capyroxene-rich exposures, its nature and occurrences within theimpact melt sheets inside the crater along with the ejecta blanketscould possibly indicate endogenic and/or exogenic nature of theobserved hydration feature. Initial results indicate the presence ofstrongest hydration feature in the partially shadowed pole-facingslopes (with low-Ca pyroxene-bearing exposures) and itscomplete absence in the equator-facing sun-lit slopes. This hintsat a possible exogenic origin, whereas the same feature occurring(with same mineral) under both sun-lit and shadowed conditionssuggest it to be of magmatic origin. We propose that theheterogeneous distribution of hydration features in GiordanoBruno is a result of both indigenous and non-indigenous sources,which makes it an interesting target for further inspections usingmulti-wavelength data.

Author(s): Sriram Saran Bhiravarasu , SatadruBhattacharya , Prakash ChauhanInstitution(s): 1. Arecibo Observatory, 2. Space ApplicationsCentre

404.06 – The effects of interplanetary dust impactson the accumulation of volatiles in the lunarpermanently shadowed regionsThe lunar regolith has been formed, and remains continuallyreworked, by the intermitten impacts of comets, asteroids,meteoroids, and the continual bombardment by interplanetarydust particles (IDP). Thick atmospheres protect Venus, Earth,and Mars, ablating the incoming IDPs into “shooting stars” thatrarely reach the surface. However, the surfaces of airless bodiesnear 1 AU are directly exposed to the high-speed (>> 1 km/s) IDPimpacts. The Moon is expected to be bombarded by 5x10 kg/dayof IDPs arriving with a characteristic speed of ~ 20 km/s. The IDPsources impacting the Moon at high latitudes remain largelyuncharacterized due to the lack of optical and radar observationsin the polar regions on Earth. These high latitude sources havevery large impact speeds in the range of 30 < v < 50 km/ hencethey are expected to have a significant effect on the lunar surface,including the removal and burial of volatile deposits in the lunar

polar regions. Water is thought to be continually delivered to the Moon throughgeological timescales by water-bearing comets and asteroids, andproduced continuously in situ by the impacts of solar windprotons of oxygen rich minerals exposed on the surface. IDPs arean unlikely source of water due to their long UV exposure in theinner solar system, but their high-speed impacts can mobilizesecondary ejecta dust particles, atoms and molecules, some withhigh-enough speed to escape the Moon. Other surface processesthat can lead to mobilization, transport and loss of watermolecules and other volatiles include solar heating,photochemical processes, and solar wind sputtering. Since noneof these are at work in permanently shadowed regions (PSR), dustimpacts remain the dominant process to dictate the evolution ofvolatiles in PSRs. The competing effects of dust impacts are: a)ejecta production leading to loss out of a PSR; b) gardening andoverturning the regolith; and c) the possible accumulation ofimpact ejecta, leading to the burial of the volatiles. This talk will summarize the expected effects of dust impacts onvolatile accumulation in the lunar PSRs based on theoreticalmodels, recent laboratory results, and observations by the LADEEspacecraft.

Author(s): Mihaly Horanyi , Jamey SzalayInstitution(s): 1. Princeton University, 2. Univ. of Colorado

404.07 – Mini-RF S- and X-band BistaticObservations of the Floor of Cabeus CraterThe Mini-RF instrument aboard NASA’s Lunar ReconnaissanceOrbiter (LRO) is a hybrid dual-polarized synthetic aperture radar(SAR) and operates in concert with the Arecibo Observatory (AO)and the Goldstone deep space communications complex 34 meterantenna DSS-13 to collect S- and X-band bistatic radar data of theMoon. Bistatic radar data provide a means to probe the nearsubsurface for the presence of water ice, which exhibits a strongresponse in the form of a Coherent Backscatter Opposition Effect(CBOE). This effect has been observed in radar data for the icysurfaces of the Galilean satellites, the polar caps of Mars, polarcraters on Mercury, and terrestrial ice sheets in Greenland.Previous work using Mini-RF S-band (12.6 cm) bistatic datasuggests the presence of a CBOE associated with the floor of thelunar south polar crater Cabeus. The LRO spacecraft has begunits third extended mission. For this phase of operations Mini-RFis leveraging the existing AO architecture to make S-band radarobservations of additional polar craters (e.g., Haworth,Shoemaker, Faustini). The purpose of acquiring these data is todetermine whether other polar craters exhibit the responseobserved for Cabeus. Mini-RF has also initiated a new mode ofoperation that utilizes the X-band (4.2cm) capability of theinstrument receiver and a recently commissioned X/C-bandtransmitter within the Deep Space Network’s (DSN) Goldstonecomplex to collect bistatic X-band data of the Moon. The purposeof acquiring these data is to constrain the depth/thickness ofmaterials that exhibit a CBOE response – with an emphasis onobserving the floor of Cabeus. Recent Mini-RF X-bandobservations of the floors of the craters Cabeus do not showevidence for a CBOE. This would suggest that the upper ~0.5meters of the regolith for the floor of Cabeus do not harber waterice in a form detectable at 4.2 cm wavelengths.

Author(s): Gerald Wesley Patterson , Angela Stickle ,Franklin Turner , James Jensen , Joshua CahillInstitution(s): 1. Johns Hopkins University Applies PhysicsLaboratryContributing team(s): the Mini-RF Team

404.08 – LRO-LAMP Observations of IlluminationConditions in the Lunar South Pole: Multi-Datasetand Model ComparisonThe south pole of the Moon is an area of great interest forexploration and scientific research because many low-lyingregions are permanently shaded and are likely to trap volatiles for

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405 – Centaurs and Kuiper Belt Objects: Surveys, Dynamics, Theory, and "Planet 9"

extended periods of time, while adjacent topographic highs canexperience extended periods of sunlight. One of the goals of theLunar Reconnaissance Orbiter (LRO) mission is to characterizethe temporal variability of illumination of the lunar polar regionsfor the benefit of future exploration efforts. We use far ultraviolet(FUV) observations made by the Lyman Alpha Mapping Project(LAMP) to evaluate illumination at the lunar south pole (within5° of the pole). LAMP observations are made through passive remote sensing inthe FUV wavelength range of 57-196 nm using reflected sunlightduring daytime observations and reflected light from the IPM andUV-bright stars during nighttime observations. In this study wefocused on the region within 5° of the pole, and produced mapsusing nighttime data taken between September 2009 andFebruary 2014. Summing over long time periods is necessary toobtain sufficient signal to noise. Many of the maps produced forthis study show excess brightness in the “Off Band”, or 155-190nm, because sunlight scattered into the PSRs is most evident inthis wavelength range. LAMP observes the highest rate of scattered sunlight in two largePSRs during nighttime observations: Haworth and Shoemaker.We focus on these craters for comparisons with an illuminationmodel and other LRO datasets. We find that the observations ofscattered sunlight do not agree with model predictions. However,preliminary results comparing LAMP maps with other LROdatasets show a correlation between LAMP observations ofscattered sunlight and Diviner measurements for maximumtemperature.

Author(s): Kathleen Mandt , Erwan Mazarico , Thomas K.Greathouse , Ben Byron , Kurt D. Retherford , RandyGladstone , Yang Liu , Amanda R. Hendrix , Dana Hurley ,Angela Stickle , G. Wes Patterson , Joshua Cahill , Jean-PierreWilliamsInstitution(s): 1. Goddard Space Flight Center, 2. JohnsHopkins University Applied Physics Laboratory, 3. PlanetaryScience Institute, 4. Southwest Research Institute, 5. Universityof California at Los Angeles, 6. University of Texas at SanAntonio

404.09D – Re-impacting Debris Facilitated Coolingof the Lunar Magma OceanIt is widely believed that the Moon formed from the debris of agiant impact between the proto-Earth and a roughly Mars-sizedbody. Concomitant to this formation scenario, and also inferredfrom geochemical analyses of Apollo samples, is the pastexistence of a Lunar Magma Ocean (LMO). After about 80% ofthe LMO solidified, it is believed that the mineral plagioclasewould have become stable and crystallized out of the LMO. Rocksthat formed principally of plagioclase would have been buoyant inthe residual liquid and thus helped form a floatation crust thatacted as a thermally conductive blanket over the LMO. Previousmodelling work found that the LMO would have solidified inabout 10 Myr. However, studies have shown that, during the giantimpact event, a large quantity of debris (totaling over a Lunarmass) would have been released that was not immediatelyincorporated into the Earth and the Moon. This material wouldhave subsequently re-impacted the Earth and the Moon.Particularly for the Moon, this debris would have punctured holesinto the nascent lunar crust, attenuated its thermal blanketingeffect, and thus facilitated the cooling of the LMO. We improveupon previous studies of the solidification of the LMO byincorporating this re-impacting debris, and find that the re-impacting debris may have reduced the LMO solidification time.

Author(s): Viranga Perera , Alan Jackson , Linda T. Elkins-Tanton , Erik AsphaugInstitution(s): 1. Arizona State University, 2. University ofArizona, 3. University of Toronto

405.01 – Debiasing the Distant Solar SystemPopulations Using Pan-STARRS1We discuss our on-going effort to identify Trans-NeptunianObjects (TNOs) in the Pan-STARRS1 dataset, and to debias thesize-frequency distributions (SFD) of detected TNO sub-populations in order to estimate their true population sizes. Tomeasure our detection efficiency we used the model of Grav et al.(2011) which includes Kuiper belt Objects (KBOs), ScatteredDisc Objects (SDOs), and Centaurs. Our debiasing methodaccounts for the per-chip CCD sensitivity as well as CCD cell gaps.The search method for finding distant Solar System objects,which was developed for our initial work (Weryk et al., 2016) ,led to discovery of 29 Centaurs, 243 KBOs and 61 SDOs from Pan-STARRS data spanning years 2010-2015. Our work is extendedusing more recent PS1 data.

[1] Grav, T., et al. (2011), Publications of the Astronomical Societyof Pacific, Volume 123, Issue 902, pp. 423. [2] Weryk, R.J., et al. (2016), eprint arXiv:1607.04895.

Author(s): Eva Lilly (Schunova) , Robert J. Weryk , SergeChastel , Larry Denneau , Robert Jedicke , Richard J.Wainscoat , Kenneth C. ChambersInstitution(s): 1. University Of Hawaii

405.02 – The Outer Solar System Origin Survey fulldata release orbit catalog and characterization.The Outer Solar System Origin Survey (OSSOS) completed maindata acquisition in February 2017. Here we report the release ofour full orbit sample, which include 836 TNOs with highprecision orbit determination and classification. We combine theOSSOS orbit sample with previously release Canada-FranceEcliptic Plane Survey (CFEPS) and a precursor survey to OSSOSby Alexandersen et al. to provide a sample of over 1100 TNO

orbits with high precision classified orbits and preciselydetermined discovery and tracking circumstances(characterization). We are releasing the full sample andcharacterization to the world community, along with software forconducting ‘Survey Simulations’, so that this sample of orbits canbe used to test models of the formation of our outer solar systemagainst the observed sample. Here I will present thecharacteristics of the data set and present a parametric model forthe structure of the classical Kuiper belt.

Author(s): J. J. Kavelaars , Michele T Bannister , BrettGladman , Jean-Marc Petit , Stephen Gwyn , MikeAlexandersen , Ying-Tung Chen , Kathryn VolkInstitution(s): 1. Institut UTINAM UMR6213, 2. Institute ofAstronomy and Astrophysics, Academia Sinica, 3. NationalResearch Council of Canada, 4. Queen's University, Belfast, 5.University of Arizona, 6. University of British ColumbiaContributing team(s): The OSSOS Collaboration.

405.03 – Biases in the OSSOS Detection of LargeSemimajor Axis Trans-Neptunian ObjectsThe accumulating but small set of large semimajor axis trans-Neptunian objects (TNOs) shows an apparent clustering in theorientations of their orbits. This clustering must either berepresentative of the intrinsic distribution of these TNOs, or elsehave arisen as a result of observation biases and/or statisticallyexpected variations for such a small set of detected objects. Theclustered TNOs were detected across different and independentsurveys, which has led to claims that the detections are thereforefree of observational bias. This apparent clustering has led to theso-called “Planet 9” hypothesis that a super-Earth currentlyresides in the distant solar system and causes this clustering. TheOuter Solar System Origins Survey (OSSOS) is a large programthat ran on the Canada–France–Hawaii Telescope from 2013 to

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2017, discovering more than 800 new TNOs. One of the primarydesign goals of OSSOS was the careful determination ofobservational biases that would manifest within the detectedsample. We demonstrate the striking and non-intuitive biasesthat exist for the detection of TNOs with large semimajor axes.The eight large semimajor axis OSSOS detections are anindependent data set, of comparable size to the conglomeratesamples used in previous studies. We conclude that the orbitaldistribution of the OSSOS sample is consistent with beingdetected from a uniform underlying angular distribution.

Author(s): Brett Gladman , Cory ShankmanInstitution(s): 1. Univ. of British Columbia, 2. University ofVictoriaContributing team(s): OSSOS collaboration

405.04 – Detection Bias for Trans-NeptunianObjects on Highly Elliptical Orbits with the DarkEnergy SurveyWe report the discovery of several new "extreme" trans-Neptunian objects (ETNOs) with semimajor axis > 150 AUdiscovered using the Dark Energy Survey (DES). This currentlyongoing survey is entering its fifth planned year of operation onthe 4m Blanco telescope in Chile and is imaging 5000 deg in thegrizY passbands to a limiting magnitude of r~23.8. Recentstudies of the significance of the observed orbital clustering of theETNOs have led to directly oppositional conclusions (M. Brown,arXiv:1706:04175; and C. Shankman et. al., arXiv:1706:05348).We present a detailed and independent study of the effects ofobservational bias on the observed clustering in the argument ofperihelion and the longitude of perihelion of the most distantTNOs using the dataset of DES. This study is of particular interestdue to DES's location at high ecliptic inclinations in addition tothe wide area of sky covered by the survey, mitigating potentialbias in measurements of both the argument of perihelion and thelongitude of ascending node. The significance of observationalbias on the discoveries made using DES has importantimplications on the hypothesis of a distant ninth planet in thesolar system.

Author(s): Stephanie Hamilton , David W. GerdesInstitution(s): 1. University of Michigan

405.05 – A Wide Field Search for Extreme Trans-Neptunian Objects and a Super Earth in the SolarSystemWe are currently conducting the deepest and widest field surveyto date sensitive to Extreme Trans-Neptunian Objects (ETNOs),bodies that have semimajor axes greater than 150 au andperihelia higher than 35 au. Our survey is also sensitive to distantsuper-Earth mass planets such as that recently hypothesized toexplain the orbital characteristics of ETNOs.

Our survey instruments are Subaru Telescope Hyper Suprime-Cam (HSC) and the Cerro Tololo Interamerican Observatory DarkEnergy Camera (DECam). HSC has a field of view of 1.75 squaredegrees on an 8 meter diameter telescope and DECam has a fieldof view of about 3 square degrees on a 4 meter diametertelescope. HSC and DECam are two of the largest light graspsurvey tools in the world capable of detecting the hypothesizedplanet. We have surveyed a few thousand square degrees withDECam (magnitude 24) and HSC (magnitude 25).

We probe both specific locations in the sky which are likely tocontain the hypothesized planet as well as nearly uniformlongitude range in both hemispheres of the sky to minimize theimpact of observational bias. We will discuss current surveyprogress, which to date has found several distant objects beyond50 au with interesting orbital properties.

Author(s): Chadwick A. Trujillo , Scott S. Sheppard , DavidJ. TholenInstitution(s): 1. Carnegie Institution for Science, 2. NorthernArizona University, 3. University of Hawaii

405.06 – The search for Planet NineWe provide an update on ourtheoretical/computational/observational search for a giant planetfar beyond Neptune. Using a combination of dynamical modelingof random starting configurations for the solar system and offorward modeling of known distant KBOs we have significantlyconstrained the orbital elements and mass of the potential planet.We provide an update of the best-fit parameters to aid theongoing world wide search. Using our increaingly preciseknowledge of how such a planet would interact with the solarsystem, we are engaged in a several large surveys to detect aplanet with these parameters. We will discuss results frommassive archival surveys and from our large Subaru Observatoryprogram.

Author(s): Michael E. BrownInstitution(s): 1. Caltech

405.07 – Evaluating the Dynamical Stability ofOuter Solar System Objects in the Presence ofPlanet NineWe present the results of an N-body analysis of the dynamicalstability of a selection of outer solar system objects in thepresence of the proposed new Solar System member Planet Nine.Our simulations show that some combinations of orbital elements($a,e$) result in Planet Nine acting as a stabilizing influence onthe TNOs, which can otherwise be destabilized by interactionswith Neptune. We also see that some TNOs transition betweenseveral different mean-motion resonances during their lifetimeswhile still retaining approximate apsidal anti-alignment withPlanet Nine. This behavior suggests that remaining in oneparticular orbit is not a requirement for orbital stability. As oneproduct of our simulations, we present an {\it a posteriori}probability distribution for the semi-major axis and eccentricityof the proposed Planet Nine based on TNO stability. We discussthis result in the broader context of the Planet Nine debate andthe dynamical stability of the detached Kuiper Belt. We alsoannounce the discovery of a new large semi-major axis, highly-inclined TNO, found in the Dark Energy Survey (DES) data. Thisnew object’s orbit places it in the same population as was used topredict the existence of Planet Nine, and so this new object alsohelps constrain the orbital elements of the proposed Planet Nine.

Author(s): Juliette Becker , Fred C. Adams , Tali Khain ,Stephanie Hamilton , David W. GerdesInstitution(s): 1. University of Michigan

405.08 – Extreme Resonant Dynamics: theDyanmics of Extreme TNOs in Mean MotionResonances With Planet 9Significant clustering among the orbits of the most distant trans-Neptunian objects (TNOs) has (re)kindled interest in thehypothesis of a distant ninth planet of the solar system (Trujillo &Sheppard 2014, Batygin & Brown 2016). Recent works byMalhotra et al. (2016) and Millholland et al. (2017) find that theorbital periods of these distant TNOs could be explained as aseries of small integer ratio mean motion resonances (MMRs)with the putative `Planet 9’. The large eccentricities andinclinations of these distant TNOs, along with the proposed orbitof Planet 9, make the proposed resonant motions of these objectsa rich dynamical problem. We explore the dynamics of meanmotion resonances at large eccentricities and inclination,focussing on implications for observing a distant resonantpopulation of TNOs and constraining the orbital properties ofPlanet 9.

Author(s): Sam Hadden , Matthew J. Payne , Matthew J.Holman , Sarah MillhollandInstitution(s): 1. Harvard-Smithsonian Center forAstrophysics, 2. Yale

405.09 – Mean-Motion Resonances and the Searchfor Planet Nine

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A key line of evidence for the existence of Planet Nine in the solarsystem is the physical clustering of Kuiper belt orbits with semi-major axis greater than ~250 au. It is expected that a fraction ofthis population is entrained in mean-motion resonances withPlanet Nine, and therefore potentially holds key constraints onPlanet Nine's present-day mean anomaly. In this talk, we report asuite of numerical simulations that inform the practicalimplications of employing resonant relationships to deducePlanet Nine's current on-sky location.

Author(s): Elizabeth Bailey , Michael Brown , KonstantinBatyginInstitution(s): 1. Caltech

405.10 – Simulations of the Solar System's EarlyDynamical Evolution with a Self-GravitatingPlanetesimal DiskOver the last decade, the "Nice Model'' has dramatically changedour view of the solar system's formation and early evolution.Within the context of this model, a transient period of planet-planet scattering is triggered by gravitational interactionsbetween the giant planets and a massive primordial planetesimaldisk, leading to a successful reproduction of the solar system'spresent-day architecture. Within typical realizations of the Nicemodel, self-gravity of the planetesimal disk is routinely neglected,as it poses a computational bottleneck to the calculations.However, it is well-known that a self-gravitating disk can exhibitbehavior that is dynamically distinct from a non-self-gravitatingdisk, and this disparity may have significant implications for thesolar system's evolutionary path. In this work, we test thisdiscrepancy by running a suite of Nice Model simulations withand without a self-gravitating planetesimal disk, taking advantageof the inherently parallel nature of graphic processing units. Oursimulations show that self-consistent modeling of theplanetesimal interactions do not lead to clear differences in thefinal planetary orbits and show similar dynamical evolutions afterthe instability is triggered.

Author(s): Siteng Fan , Konstantin BatyginInstitution(s): 1. California Institute of Technology

405.11 – The Midplane of the Kuiper Belt and ItsUnexpected WarpsWe measured the mid-plane of the Kuiper belt as a function ofsemi-major axis, based on the entire current catalog of the Kuiperbelt (Volk & Malhotra, 2017, AJ 154, article id. 62). Themeasurement method we use is nearly insensitive toobservational selection effects. For the classical Kuiper belt as awhole (the non-resonant objects in the semi-major axis range 42—48 au), we find a mid-plane in accord with theoreticalexpectations of the secular effects of the known planets. Withfiner semi-major axis bins, we detect a statistically significantwarp near 40—42 au. Linear secular theory predicts a localized

warp near this location due to the ν nodal secular resonance,however the measured mean plane is inclined ~13 degrees to thepredicted plane, a nearly 3σ discrepancy. For the scattered disk(non-resonant objects of semi-major axes in the range 50—80au), the expected mid-plane is close to the solar system’sinvariable plane, however the measured mid-plane deviates fromthe invariable plane by ~7 degrees, also a nearly 3σ discrepancy.We will report on new results from our mid-plane calculationsand their measurement uncertainties for additional dynamicalsubsets of the Kuiper belt, and we will discuss implications forunseen bodies in the distant Kuiper belt. We gratefully acknowledge research funding from NASA (grantNNX14AG93G) and NSF (grant AST-1312498).

Author(s): Renu Malhotra , Kathryn VolkInstitution(s): 1. The University of Arizona

405.12 – Determining The Plane of The Kuiper Beltwith OSSOSWe present the OSSOS-based measurement of the semi-majoraxes dependent orientation of the Kuiper Belt plane. A KuiperBelt object's (KBO's) inclination can be broken down into a forcedcomponent and a free component. The inclination and longitudeof ascending node of the forced inclination define the 'forcedplane,' the plane about which the KBO's inclination will precess.Secular theory predicts that this forced plane should depend onsemi-major axis. For example, the nu18 secular resonance shouldcreate a significant warp in the forced planet near 40.5 au (Chiangand Choi 2008). Not predicted by secular theory is a warp in thedistant Kuiper Belt (semi-major axes greater than 50 au) seen byVolk and Malhotra 2016 using KBOs from the Minor PlanetCatalog. We investigate what the inclination distribution is forobjects beyond Neptune as a function of semi-major axis usingthe OSSOS characterized sample. Through use of the OSSOSsurvey simulator we test various underlying orbital distributionsand compare how the survey would have observed thosepopulations to the actual observed sample. In particular, we testvarious widths for the inclination distribution about various localforcing planes for the kernel, stirred, and hot classical KuiperBelt. Because the biases of OSSOS are extremely wellcharacterized, we can make rigorous statistical statements as towhat hypothetical Kuiper Belts are consistent with the actualKuiper Belt as observed by OSSOS.

Author(s): Christa L. Van Laerhoven , J. J. Kavelaars ,Kathryn Volk , Brett Gladman , Jean-Marc PetitInstitution(s): 1. CNRS / Observatoire De Besançon, 2.National Research Council of Canada, Herzberg, 3. University ofArizona, 4. University of British Columbia

406.01 – On the impact origin of Phobos andDeimosPhobos and Deimos, the two small satellites of Mars, are thoughteither to be captured asteroids or to have accreted in an impact-induced debris disk. Recently, we succeeded in making them in aframework of the giant impact scenario [1]. In our canonicalsimulation, large moons form from the material in the denseinner disk and then migrate outwards due to gravitationalinteractions with the remnant disk. As the large inner moonsmigrate outward, their orbital resonances sweep up and gathermaterials distributed within a thin outer disk, facilitatingaccretion of two small satellites whose sizes are similar to Phobosand Deimos. The large inner moons fall back to Mars after about5 million years due to tidal pull of Mars, and the two small outersatellites evolve into current Phobos- and Deimos-like orbits. In addition, we recently perform high-resolution SPH giantimpact simulations using sophisticated equation of states (M-ANEOS). We investigate the thermodynamic and physical aspectsof the impact-induced disk [2], such as degrees of melting and

vaporization of materials, mixing ratio of Mars and impactor’smaterials, and expected particle sizes that form Phobos andDeimos. Our results will give useful information for planning afuture sample return mission to Martian moons, such as JAXA’sMMX (Martian Moons eXploration) mission. [1] Rosenblatt, P., Charnoz, S., Dunseath, K.M., Terao-Dunseath,M., Trinh, A., Hyodo, R., Genda, H., Toupin, S., 2016. Accretionof Phobos and Deimos in an extended debris disc stirred bytransient moons. Nature Geoscience 9, 581-583. [2] Hyodo, R., Genda, H., Charnoz, S., Rosenblatt, P., 2017, Onthe impact origin of Phobos and Deimos I: Thermodynamic andphysical aspects. ApJ accepted (arXiv:1707.06282).

Author(s): Hidenori Genda , Ryuki Hyodo , SebastianChanorz , Pascal RosenblattInstitution(s): 1. Institut de Physique du Globe, 2. RoyalObservatory of Belgium, 3. Tokyo Institute of Technology

406.02 – Radiation Environment of Phobos

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408 – Extrasolar Planets and Systems: Giant Planet Atmospheres II

The innermost Martian moon Phobos is a potential way stationfor the human exploration of Mars and the solar system beyondthe orbit of Mars. It has a similar radiation environment to that at1 AU for hot plasma and more energetic particles from solar,heliospheric and galactic sources. In the past two decades therehave been many spacecraft measurements at 1 AU, andoccasionally in the Mars orbital region around the Sun, that canbe used to define a reference model for the time-averaged andtime-variable radiation environments at Mars and Phobos. Yearlyto hourly variance comes from the eleven-year solar activity cycleand its impact on solar energetic, heliospheric, and solar-modulated galactic cosmic ray particles. We report progress oncompilation of the reference model from U.S. and internationalspacecraft data sources of the NASA Space Physics Data Facilityand the Virtual Energetic Particle Observatory (VEPO), and fromtissue-equivalent dosage rate measurements by the CRaTERinstrument on the Lunar Reconnaissance Observer spacecraftnow in lunar orbit. Similar dosage rate data are also availablefrom the Mars surface via the NASA Planetary Data Systemarchive from the Radiation Assessment Detector (RAD)instrument aboard the Mars Science Laboratory (MSL) Curiosityrover. The sub-Mars surface hemisphere of Phobos is slightlyblocked from energetic particle irradiation by the body of Mars

but there is a greater global variance of interplanetary radiationexposure as we have calculated from the known topography ofthis irregularly shaped moon. Phobos receives a relatively smallflux of secondary radiation from galactic cosmic ray interactionswith the Mars surface and atmosphere, and at plasma energiesfrom pickup ions escaping out of the Mars atmosphere. Thegreater secondary radiation source is from cosmic ray interactionswith the moon surface, which we have simulated with the GEANTradiation transport code for various cases of the surface regolithcomposition. We evaluate the efficiency of these materials relativeto water for radiation shielding of human explorers on Phobos.The low-energy plasma environment is also considered for impacton surface charging.

Author(s): John F. Cooper , John H. Clark , Steven J.Sturner , Timothy Stubbs , Yongli Wang , David A. Glenar ,Nathan A. Schwadron , Colin J. Joyce , Harlan E. Spence ,William M. FarrellInstitution(s): 1. Howard University, 2. NASA Goddard SpaceFlight Center, 3. University of Maryland Baltimore County, 4.University of New Hampshire

408.01 – Non-LTE Models for the ThermalStructure of Hot JupitersNumerous models exist for the thermal structure of the lower andupper atmospheres of hot Jupiters but the middle atmosphere has yet to be investigated in detail. Wepresent the first calculations for the thermal structure of hot Jupiter atmospheres from 1 mbar to 1nbar, a region that is critical to the formation of observable spectral features, especially the strongresonance lines of alkali metals. The models connect the LTE region at the high pressure with thethermosphere at the low pressure. An important goal of this research is the description of the sharptemperature gradient that leads to the high thermospheric temperatures and is a critical factor inestablishing atmospheric escape rates. The calculations include thermal conduction, UV heating, andradiative transfer in the molecular bands and rotational lines of H2O. The radiative transfer calculations treatdepartures from LTE, that become important at pressures less than ~1 microbar. We will discuss theinterplay between radiative transfer in vibrational bands, that experience non-LTE effects, androtational lines, which do not. The implications for interpretation of Na I transit depths on HD189733B will bediscussed and well as the connection with atmospheric escape rates.

Author(s): Roger V Yelle , Tommi Koskinen , PanayiotisLavvasInstitution(s): 1. University of Arizona, 2. University of Reims

408.02 – Cassini ISS Observations of Jupiter: AnExoplanet Perspective Understanding the optical and physical properties of planets inour solar system can guide our approach to the interpretation ofobservations of exoplanets. Although some work has already beendone along these lines, there remain low-hanging fruit. Duringthe Cassini Jupiter encounter, the Imaging Science Subsystem(ISS) obtained an extensive set of images over a large range ofphase angles (near-zero to 140 degrees) and in filters from near-UV to near-IR, including three methane bands and nearbycontinuum. The ISS also obtained images using polarizers. Muchlater in the mission we also obtained distant images while in orbitaround Saturn. Some of these data have already been studied toreveal phase behavior (Dyudina et al., Astrophys. J. 822, DOI: 10.3847/0004-637X/822/2/76; Mayorga et al., 2016,Astron. J. 152, DOI: 10.3847/0004-6256/152/6/209). Here weexamine rotational modulation to determine wavelength and

phase angle dependence, and how these may depend on cloudand haze vertical structure and optical properties. The existenceof an optically thin forward-scattering and longitudinally-homogeneous haze overlying photometrically-variable cloudfields tends to suppress rotational modulation as phase angleincreases, although in the strong 890-nm methane band cloudvertical structure is important. Cloud particles (non-sphericalammonia ice, mostly) have very small polarization signatures atintermediate phase angles and rotational modulation is notapparent above the noise level of our instrument. Part of thiswork was performed by the Jet Propulsion Lab, Cal. Inst. OfTechnology.

Author(s): Robert A West , Benjamin KnowlesInstitution(s): 1. JPL/Caltech, 2. Space Science Institute

408.03 – Bayesian Analysis of Hot Jupiter RadiiPoints to Ohmic DissipationThe cause of the unexpectedly large radii of hot Jupiters has beenthe subject of many hypotheses over the past 15 years and is oneof the long-standing open issues in exoplanetary physics. In ourwork, we seek to examine the population of 300 hot Jupiters toidentify a model that best explains their radii. Using ahierarchical Bayesian framework, we match structure evolutionmodels to the observed giant planets’ masses, radii, and ages,with a prior for bulk composition based on the mass fromThorngren et al. (2016). We consider various models for therelationship between heating efficiency (the fraction of fluxabsorbed into the interior) and incident flux. For the first time,we are able to derive this heating efficiency as a function ofplanetary T_eq. Models in which the heating efficiency decreasesat the higher temperatures (above ~1600 K) are strongly andstatistically significantly preferred. Of the published models forthe radius anomaly, only the Ohmic dissipation model predictsthis feature, which it explains as being the result of magnetic dragreducing atmospheric wind speeds. We interpret our results asstrong evidence in favor of the Ohmic dissipation model.

Author(s): Daniel Thorngren , Jonathan J. FortneyInstitution(s): 1. UC Santa Cruz

408.04 – Giant Planet Interior Physics from Near-Infrared SpectroscopyTransiting planets give us excellent probes of giant exoplanetstructure (from mass and radius) and atmospheres (from transitand occultation spectroscopy). However, the combined power ofthese observations to understand how the planetary interiorstructure may impact its atmosphere has not yet been fullyexploited. This will change with JWST. In particular, near-infrared wavelengths have less water opacity than mid-IR

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wavelengths, which allows us to probe thermal emission fromdeeper, hotter regions of the atmosphere. In some circumstanceswe should be able to see thermal emission coming from below theradiative-convective boundary in the atmosphere, including theadiabat itself. This adiabat continues into the planet’s very deepinterior -- the specific entropy of this adiabat sets the planetaryradius at a given mass. Hot internal adiabats, which we should beable to ``see” in thermal emission, should be present for the mostinflated hot Jupiters, and planets like warm Neptunes that arestrongly influenced by tidal heating (e.g. GJ 436b, Morley et al.2017). Determining the flux coming from these atmosphericdepths can be an important constraint on structure models ofplanets that have aimed to understand giant planet bulk metalenrichment, which is an important constraint on formationmodels. These flux detections can also provide novel andreasonably direct constraints on planetary tidal Q for eccentricplanets. We highlight how we expect JWST to open up this newwindow into exoplanetary physics.

Author(s): Jonathan J. Fortney , Daniel Thorngren ,Michael R. Line , Caroline MorleyInstitution(s): 1. Arizona State University, 2. HarvardUniversity, 3. University of California, Santa Cruz

408.05 – First Results From The Ultimate SpitzerPhase Curve SurveyExoplanet phase curves provide a wealth of information aboutexoplanet atmospheres, including longitudinal constraints onatmospheric composition, thermal structure, and energytransport, that continue to open new doors of scientific inquiryand propel future investigations. The measured heatredistribution efficiency (or ability to transport energy from aplanet's highly-irradiated dayside to its eternally-dark nightside)shows considerable variation between exoplanets. Theoreticalmodels predict a correlation between heat redistributionefficiency and planet temperature; however, the latest results areinconsistent with current predictions. We will present first resultsfrom a 660-hour Spitzer phase curve survey program that istargeting six short-period extrasolar planets. We will compare themeasured heat redistribution efficiencies with planet temperatureand rotation rate, examine trends in the phase curve peak offset,and discuss cloud coverage constraints. We will conclude withhow to move forward with phase curve observations in the era ofJWST.

Author(s): Kevin B. Stevenson , Jacob Bean , DrakeDeming , Jean-Michel Desert , Jonathan J. Fortney , TiffanyKataria , Eliza Kempton , Nikole Lewis , Michael R. Line ,Caroline Morley , Emily Rauscher , Adam P. ShowmanInstitution(s): 1. Arizona State University, 2. Grinnell College,3. Harvard CfA, 4. JPL, 5. STScI, 6. UC Santa Cruz, 7. Universityof Amsterdam, 8. University of Arizona, 9. University ofChicago, 10. University of Maryland, 11. University of Michigan

408.06 – Atmospheric Compositions and CloudProperties of Small, Cool Transiting PlanetsOngoing transit surveys have discovered thousands of planetsorbiting nearby stars, many of which have properties that differsubstantially from those of the planets in our own solar system. Inthis talk I will focus on recent HST and Spitzer observations ofseveral relatively small (sub-Saturn-sized) and cool (<1000 K) gasgiant planets, which can be used to constrain their atmosphericproperties. Transmission spectroscopy surveys with HST havedemonstrated that high altitude cloud layers are nearlyubiquitous among this class of transiting planets; this has provento be a challenge for composition studies, as the presence of ahigh altitude cloud layer obscures the signatures of atmosphericabsorption features. In my talk I will explore our ability toconstrain cloud properties using transmission spectroscopy, aswell as the power of complementary emission spectroscopy toprovide a window into the atmospheric compositions of cloudyplanets.

Author(s): Heather KnutsonInstitution(s): 1. California Institute of Technology

408.07 – Investigating three-dimensional cloudproperties in a large hot Jupiter sampleObservations of exoplanet atmospheres have shown that cloudsand hazes are ubiquitous, but can vary widely over a range ofphysical properties. In the case of hot Jupiters, previous Spitzerand Hubble Space Telescope observations of a nine-planet sampleshow a range of alkali/water abundances, as well as Rayleighscattering at near-UV and optical wavelengths, that suggest acontinuum of atmospheres from clear to cloudy. Three-dimensional general circulation models (GCMs) of these planetsshow that the circulation and temperature structure, both ofwhich influence cloud formation and transport, varies as afunction of planet radius, gravity, orbital period, and equilibriumtemperature. However, which physical properties most stronglyinfluence cloud formation in hot Jupiters has been largelyunexplored over a large sample. Here we utilize previous 3D GCMresults of this nine-planet sample to produce 3D cloud mapsusing a simplified cloud scheme by Ackerman and Marley (2000).We examine trends in cloud types and cloud distributions thatarise from differences in each planet’s physical properties. We usethese 3D temperature and cloud maps to derive ‘cloudy’transmission spectra that we then compare to existing Hubbleand Spitzer Space Telescope data. In particular, we focus ondifferences in cloud properties between leading and trailinglimbs, each of which contribute equally to a planet’s overalltransmission spectrum. These and future analyses will have largeimplications for the cloud properties that can be explored withfuture facilities, such as the James Webb Space Telescope.

Author(s): Tiffany Kataria , Taylor Baldwin , HeatherKnutson , Hannah Wakeford , Dimitri Mawet , David K. SingInstitution(s): 1. California Institute of Technology, 2.JPL/Caltech, 3. Univ. of Exeter

408.08 – The Exoplanet Cloud AtlasClouds have been readily inferred from observations of exoplanetatmospheres, and there exists great variability in cloudinessbetween planets, such that no clear trend in exoplanet cloudinesshas so far been discerned. Equilibrium condensation calculationssuggest a myriad of species - salts, sulfides, silicates, and metals -could condense in exoplanet atmospheres, but how they behaveas clouds is uncertain. The behavior of clouds - their formation,evolution, and equilibrium size distribution - is controlled bycloud microphysics, which includes processes such as nucleation,condensation, and evaporation. In this work, we explore thecloudy exoplanet phase space by using a cloud microphysicsmodel to simulate a suite of cloud species ranging from coolercondensates such as KCl/ZnS, to hotter condensates likeperovskite and corundum. We investigate how the cloudiness andcloud particle sizes of exoplanets change due to variations intemperature, metallicity, gravity, and cloud formationmechanisms, and how these changes may be reflected in currentand future observations. In particular, we will evaluate where inphase space could cloud spectral features be observable usingJWST MIRI at long wavelengths, which will be dependent on thecloud particle size distribution and cloud species.

Author(s): Peter Gao , Mark S. Marley , Caroline Morley ,Jonathan J. FortneyInstitution(s): 1. Harvard University, 2. NASA Ames ResearchCenter, 3. University of California, Berkeley, 4. University ofCalifornia, Santa Cruz

408.09D – The Atmospheric Circulation of HotJupiters: a Hierarchical Modeling ApproachThe atmospheres of extrasolar gas giants that receive strongstellar irradiation, or “hot Jupiters,” are beginning to becharacterized as a population. Photometric full-phase light curvesof hot Jupiters allow for basic inferences of their atmosphericcirculation, providing two key observables. First, they measurethe amplitude of brightness variation, which has shown that thefractional brightness temperature difference between the daysideand nightside in the atmospheres of these tidally locked planetscan approach unity. Additionally, each planet has a significant

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407 – Io: The Volcanic Wonderland

Presentation of Harold Masursky Award, Jonathan Eberhart Planetary SciencesJournalism Award, and Harold C. Urey Prize

410 – Harold C. Urey Prize: Mars’ First Billion Years: Key Findings, Key UnsolvedParadoxes, and Future Exploration, Bethany Ehlmann (Caltech)

observed offset of the brightest point in their light curve, andoffsets in the infrared ubiquitously occur before secondaryeclipse. These infrared offsets are best explained by strong(~km/s) eastward winds in hot Jupiter atmospheres. Motivatedby these observations, we have developed a first-principlesanalytic theory that predicts dayside-nightside temperaturedifferences and horizontal and vertical wind speeds as a functionof incident stellar flux, rotation rate, frictional drag strength, andatmospheric pressure level. To complement and compare withthis theory, we have performed a hierarchy of three-dimensionalnumerical simulations of the atmospheric circulation to explorechanges with incident stellar flux, rotation rate, and dragstrength. Both the theory and numerical simulations predict thatthe dayside-nightside temperature differences of hot Jupiters andtheir wind speeds should increase with increasing incident stellarflux and decrease with increasing drag strength. So far, this has

been hinted at in the observed sample of nine hot Jupiter phasecurves, but we predict that these broad trends will be robust witha larger observed population. We extend our theory to estimatevertical mixing rates, which is critical for understanding theimpact of clouds and disequilibrium chemistry on observations ofhot Jupiters. To show the regimes that this theory applies in, wecompare numerically simulated vertical mixing rates with ouranalytic theory. As a result, one can use our theoreticallypredicted vertical mixing rates as input for one-dimensionalmodels of cloud formation and disequilibrium chemistry in hotJupiter atmospheres.

Author(s): Thaddeus D. Komacek , Adam P. ShowmanInstitution(s): 1. University of Arizona

407.01 – Recent Observations of Io's ActiveVolcanoes from IRTF: Imaging and OccultationLightcurvesWe have been observing Ionian volcanism from NASA’s InfraredTelescope Facility (IRTF) for more than two decades. Thefrequency of our observations increases dramatically whenspacecraft are observing Io in order to complement the datareturned by the spacecraft. The Juno spacecraft has beenobserving Jupiter’s interior, atmosphere and magnetospheresince July 2016. In order to investigate the possible influence ofIo volcanism on the Jovian magnetosphere, we have obtainedobservations to constrain Io's volcanic activity from the IRTF onMauna Kea on over 50 occasions beginning in January 2016. Weimaged Io at 2.2, 3.5, and 4.8 microns in eclipse and reflectedsunlight. We also observed Io during occultation by Jupiter,which allows us to locate and characterize individual volcaniceruptions, with greater spatial accuracy, on the Jupiter-facinghemisphere. Preliminary analysis indicates that Loki underwent atypical brightening episode from late February to June 2017 andthat Kanehekilli/Janus and Pillan/Marduk were also active.

Author(s): Julie A. Rathbun , John R. SpencerInstitution(s): 1. Planetary Science Institute, 2. SouthwestResearch Institute

407.02 – Diffraction-limited Mid-infrared IntegralField Spectroscopy of Io's Volcanic Activity withALES on the Large Binocular TelescopeThe Arizona Lenslet for Exoplanet Spectroscopy (ALES) is anenhancement to the Large Binocular Telescope's mid-infraredimager, LMIRcam, that permits low-resolution (R~20)spectroscopy between 2.8 and 4.2 μm of every diffraction-limitedresolution element in a 2.5"x2.5" field-of-view on a 2048x2048HAWAII-2RG 5.2 μm-cutoff array. The 1" disk of Io, dotted withpowerful self-luminous volcanic eruptions, provides an idealtarget for ALES, where the single 8.4-meter aperture diffraction-limited scale for Io at opposition ranges from 240 kilometers (80milliarcseconds) at 2.8 μm to 360 kilometers (120milliarcseconds) at 4.2 μm. ALES provides the capability to assessthe color temperature of each volcanic thermal emission site aswell as map broadband absorbers such as SO frost. A monitoringcampaign in the Spring 2017 semester provided two globalsnapshots of Io's volcanic activity with ALES as well ascharacterization of a new brightening episode at Loki Patera overfour epochs between January and May 2017.

Author(s): Michael F. Skrutskie , Katherine R. de Kleer ,Jordan Stone , Al Conrad , Ashley Davies , Imke de Pater ,Jarron Leisenring , Philip Hinz , Andrew Skemer , ChristianVeillet , Charles E. Woodward , Steve Ertel , Eckhart SpaldingInstitution(s): 1. California Institute of Technology, 2. JetPropulsion Laboratory - California Institute of Technology, 3.Large Binocular Telescope Observatory, 4. University ofArizona, 5. University of California, Berkeley, 6. University ofCalifornia, Santa Cruz, 7. University of Minnesota, 8. Universityof Virginia

407.03D – Io’s volcanoes at high spatial, spectral,and temporal resolution from ground-basedobservations Io’s dynamic volcanic eruptions provide a laboratory for studyinglarge-scale volcanism on a body vastly different from Earth, andfor unraveling the connections between tidal heating and thegeological activity it powers. Ground-based near-infraredobservatories allow for high-cadence, long-time-baselineobserving programs using diverse instrumentation, and yield newinformation into the nature and variability of this activity. I willsummarize results from four years of ground-based observationsof Io’s volcanism, including: (1) A multi-year cadence observingcampaign using adaptive optics on 8-10 meter telescopes, whichplaces constraints on tidal heating models through sampling thespatial distribution of Io’s volcanic heat flow, and providesestimates of the occurrence rate of Io’s most energetic eruptions;(2) High-spectral-resolution (R~25,000) studies of Io’s volcanicSO gas emission at 1.7 microns, which resolves this rovibronicline into its different branches, and thus contains detailedinformation on the temperature and thermal state of the gas; and(3) The highest-spatial-resolution map ever produced of theentire Loki Patera, a 20,000 km volcanic feature on Io, derivedfrom adaptive-optics observations of an occultation of Io byEuropa. The map achieves a spatial resolution of ~10 km andindicates compositional differences across the patera. Thesedatasets both reveal specific characteristics of Io’s individualeruptions, and provide clues into the sub-surface systemsconnecting Io’s tidally-heated interior to its surface expressions ofvolcanism.

Author(s): Katherine R. de Kleer , Imke de PaterInstitution(s): 1. California Institute of Technology, 2. UCBerkeley

410.01 – Mars’ First Billion Years: Key Findings,Key Unsolved Paradoxes, and Future Exploration

In the evolution of terrestrial planets, the first billion years arethe period most shrouded in mystery: How vigorous is earlyatmospheric loss? How do planetary climates respond to abrightening sun? When and how are plate tectonic recycling

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411 – Plenary Talk: Gone with the Wind: Three Years of MAVEN Measurements ofAtmospheric Loss at Mars, David Brain (Univ. of Colorado, Boulder)

412 – Plenary Talk: A Septet of Earth-Sized Planets, Amaury Triaud (Univ. of Cambridge)

413 – Origins and Planet Formation

processes initiated? How do voluminous volcanism and heavyimpact bombardment influence the composition of theatmosphere? Under what conditions might life arise? Lookingoutward to terrestrial planets around other stars, the record fromVenus, Earth and Mars in this solar system is crucial fordeveloping models of physical can chemical processes. Of thesethree worlds, Mars provides the longest record of planetaryevolution from the first billion years, comprising >50% ofexposed geologic units, which are only lightly overprinted by laterprocesses.

Orbital observations of the last decade have revealed abundantevidence for surface waters in the form of lakes, valley networks,and evidence of chemically open-system near-surface weathering.Groundwaters at temperatures ranging from just above freezingto hydrothermal have also left a rich record of process in themineralogical record. A rsuite of environments – similar indiversity to Earth’s – has been discovered on Mars with water pH,temperature, redox, and chemistries varying in space and time.

Here, I will focus on the consequences of the aqueous alterationof the Martian crust on the composition of the atmosphere basedon recent work studying aspects of the volatile budget (Usui et al.,2015; Edwards & Ehlmann, 2015; Hu et al., 2015; Jakosky et al.,2017, Wordsworth et al., 2017, and Ehlmann, in prep.). The solidcrust and mantle of Mars act as volatile reservoirs and volatilesources through volcanism, mineral precipitation, and release ofgases. We examine the extent to which the budget is understoodor ill-understood for hydrogen and carbon, and associated phasesH2O, CO2, and CH4. Additionally, I identify some keystratigraphies where a combination of focused in situ analysesand/or sample return can answer questions about the response ofthe atmosphere -- and thus Mars climate -- to endogenous andexogenous planetary processes active during the first billionyears.

Author(s): Bethany EhlmannInstitution(s): 1. Caltech

411.01 – Gone with the Wind: Three Years ofMAVEN Measurements of Atmospheric Loss atMarsThe Mars Atmosphere and Volatile EvolutioN (MAVEN) missionis making measurements of the Martian upper atmosphere andnear space environment, and their interactions with energyinputs from the Sun. A major goal of the mission is to evaluate theloss of atmospheric gases to space in the present epoch, and overMartian history. MAVEN is equipped with instruments thatmeasure both the neutral and charged upper atmospheric system(thermosphere, ionosphere, exosphere, and magnetosphere),inputs from the Sun (extreme ultraviolet flux, solar wind andsolar energetic particles, and interplanetary magnetic field), andescaping atmospheric particles. The MAVEN instruments,coupled with models, allow us to more completely understand thephysical processes that control atmospheric loss and the particlereservoirs for loss.

Here, we provide an overview of the significant results fromMAVEN over approximately 1.5 Mars years (nearly three Earthyears) of observation, from November 2014 to present. We arguethat the MAVEN measurements tell us that the loss ofatmospheric gases to space was significant over Martian history,and present the seasonal behavior of the upper atmosphere andmagnetosphere. We also discuss the influence of extreme eventssuch as solar storms, and a variety of new discoveries andobservations of the Martian system made by MAVEN.

Author(s): David BrainInstitution(s): 1. University of ColoradoContributing team(s): The MAVEN Team

412.01 – A septet of Earth-sized planetsUnderstanding the astronomical requirements for life to emerge,and to persist, on a planet is one of the most important andexciting scientific endeavours, yet without empirical answers. Toresolve this, multiple planets whose sizes and surfacetemperatures are similar to the Earth, need to be discovered.Those planets also need to possess properties enabling detailedatmospheric characterisation with forthcoming facilities, fromwhich chemical traces produced by biological activity can inprinciple be identified.

I will describe a dedicated search for such planets calledSPECULOOS. Our first detection is the TRAPPIST-1 system.Intensive ground-based and space-based observations haverevealed that at least seven planets populate this system. Wemeasured their radii and obtained first estimates of their massesthanks to transit-timing variations. I will describe our on-going

g g gobservational efforts aiming to reduce our uncertainties on theplanet properties. The incident flux on the planets ranges from Mercury to Ceres,comprising the Earth, and permitting climatic comparisonsbetween each of those worlds such as is not possible within ourSolar system. All seven planets have the potential to harbourliquid water on at least a fraction of their surfaces, given someatmospheric and geological conditions.

Author(s): Amaury TriaudInstitution(s): 1. University of BirminghamContributing team(s): The SPECULOOS team, the TRAPPIST-1 team

413.01 – Quantifying Atmospheric Mass Loss usingNovel Hydrodynamic SimulationsAfter their formation, planets may accrete or lose atmosphericmass following impacts by planetesimals. Quantifying the relationbetween the impactor energy and the mass it erodes from aplanet's atmosphere is crucial to our understanding of the finalstages in planetary formation. Particulatly, it could help explainthe significant differences between the atmospheres of the threelarger terrestrial planets in the solar system. Here we adopt a new hydrodynamic model called RICH,originally developed to solve problems in astrophysics. RICH'simplementation include a Voroni tessellation and a moving(semi-Lagrangian) mesh, which allows high resolution, efficient

modeling of shockwave propagation in thin atmospheres. Usingthis model we evaluate the role of smaller planetesimals ineroding Earth's atmosphere compared to larger, Mars-sizeobjects. Additionally, we verify the results obtained by a past 1Danalytic model which showed the current differences in Earth'sand Venus's atmospheres can potentially be explained by smalldifferences in their initial atmospheric mass and impact history.

Author(s): Lior Rubanenko , Elad Steinberg , HilkeSchlichting , David A. PaigeInstitution(s): 1. The Hebrew University, 2. University ofCalifornia, Los Angeles

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413.05 – Simulating Planet Formation - AnOptimized Population Synthesis ApproachOur current understanding of planet formation suffers from anumber of uncertainties. In particular, the evolution ofprotoplanetary disks, the transport of small particles within disks,the formation of protoplanets, and the migration of planetaryorbits are all poorly understood. For the first time, however, wehave a large data set of observed planetary systems that can beused to test models for planet formation and potentially resolvesome of these uncertainties. Here, I will describe a simple modelfor planet formation that follows the growth of a handful ofprotoplanets accreting pebble-sized particles in a low-viscositydisk. The main unknowns are encapsulated in a set of modelparameters. The model is run for a large number of stars withdifferent initial conditions. The results are compared withestimates for the real distribution of planetary orbits and massesbased on debiased surveys for extrasolar planets. The process isiterated using a particle-swarm optimization scheme to determinethe best fit set of model parameters. Here, I will discuss how wellthe simple model can match the observed distribution of planets,and what this can tell us about planet formation.

Author(s): John E. ChambersInstitution(s): 1. Carnegie Inst. of Washington

413.06 – Gap opening after merger events of 3-Earth-mass protoplanetsWhile several-Earth-mass protoplanets can gain non-negligibleeccentricities due to their interactions with the gaseous disk andongoing pebble accretion (so called hot trail effect; see thecontribution of Chrenko et al. 2017 for details), there is a openedpathway for giant-planet core formation by means of closeencounters and eventual merging. As soon as a massive (~13M_E) merger is formed, it seems necessary to account for oneadditional term in the set of hydrodynamic equations, namely thegas accretion, which may affect subsequent orbital evolution, andeventually change Type-I migration to Type-II. Using similarapproximations as Crida and Bitsch (2017), we prolong ourprevious simulations towards the onset of gap opening.

At the same time, we try to address the observability of theseevents, e.g. by ALMA in its full configuration. Because the disk isstill mostly optically thick in the vertical direction (tau =~ 100), itis necessary to properly model the disk atmosphere. In themidplane, the mean-free path of gas molecules is small enough toassure a sufficient thermal contact and equilibrium between thegas and dust. This is no more true far from the midplane and onehas to use a non-equilibrium model (e.g. Radmc-3d code) for thedescription of dust grain temperatures, resulting synthetic image,or emergent spectrum.

Author(s): Miroslav Broz , Ondrej ChrenkoInstitution(s): 1. Charles University, Astronomical Institute

413.09 – Late accretion to the terrestrial planetsIntroduction It is generally accepted that silicate-metal (`rocky') planetformation relies on coagulation from a mixture of sub-Mars sizedplanetary embryos and (smaller) planetesimals that dynamicallyemerge from the evolving circum-solar disc in the first few millionyears of our Solar System. Once the planets have, for the mostpart, assembled after a giant impact phase, they continue to bebombarded by a multitude of planetesimals left over fromaccretion. Here we place limits on the mass and evolution of theseplanetesimals based on constraints from the highly siderophileelement (HSE) budget of the Moon. The terrestrial and lunar HSEbudgets indicate that Earth’s and Moon’s additions through lateaccretion were 0.7 wt% and 0.02 wt% respectively. Thedisproportionate high accretion between the Earth and Mooncould be explained by stochastic accretion of a few remainingCeres-sized bodies that preferentially targeted the Earth.

Results

From a combination of N-body and Monte Carlo simulations ofplanet formation we conclude: 1) matching the terrestrial to lunar HSE ratio requires that lateaccretion on Earth mostly consisted of a single lunar-sizeimpactor striking the Earth before 4.45 Ga; 2) the flux of terrestrial impactors must have been low avoidwholesale melting of Earth's crust after 4.4 Ga[6], and tosimultaneously match the number of observed lunar basins; 3) after the terrestrial planets have fully formed, the mass inremnant planetesimals was ~0.001 Earth mass, lower than mostprevious models suggest. 4) Mars' HSE budget also requires a colossal impact with a Ceres-sized object before 4.43 Ga, whose visible remnant could be thehemispherical dichotomy. These conclusions lead to an Hadean eon which is more clementthan assumed previously. In addition, our dynamically andgeochemically self-consistent scenario requires that future N-body simulations of rocky planet formation either directlyincorporate collisional grinding or rely on pebble accretion.

Author(s): Ramon Brasser , Stephen Mojzsis , StephanieWerner , Soko Matsumura , Shigeru IdaInstitution(s): 1. Centre for Earth Evolution and Dynamics, 2.Earth Life Science Institute, 3. University of Colorado, 4.University of Dundee

413.10 – Atomic-scale simulation of dust graincollisions: Surface chemistry and dissipationbeyond existing theoryThe early stages of planet formation involve steps wheresubmicron-sized dust particles collide to form aggregates.However, the mechanism through which millimeter-sizedparticles aggregate to kilometer-sized planetesimals is still notunderstood. Dust grain collision experiments carried out in theenvironment of the Earth lead to the prediction of a 'bouncingbarrier' at millimeter-sizes. Theoretical models, e.g., Johnson-Kendall-Roberts and Derjaguin-Muller-Toporov theories, lacktwo key features, namely the chemistry of dust grain surfaces, anda mechanism for atomic-scale dissipation of energy. Moreover,interaction strengths in these models are parameterized based onexperiments done in the Earth's environment. To address theseissues, we performed atomic-scale simulations of collisionsbetween nonhydroxylated and hydroxylated amorphous silicananoparticles. We used the ReaxFF approach which enablesmodeling chemical reactions using an empirical potential. Wefound that nonhydroxylated nanograins tend to adhere withmuch higher probability than suggested by existing theories. Bycontrast, hydroxylated nanograins exhibit a strong tendency tobounce. Also, the interaction between dust grains has thecharacteristics of a strong chemical force instead of weak van derWaals forces. This suggests that the formation of strong chemicalbonds and dissipation via internal atomic vibration may result inaggregation beyond what is expected based on our currentunderstanding. Our results also indicate that experiments shouldmore carefully consider surface conditions to mimic the spaceenvironment. We also report results of simulations with moltensilica nanoparticles. It is found that molten particles are morelikely to adhere due to viscous dissipation, which supportstheories that suggest aggregation to kilometer scales mightrequire grains to be in a molten state.

Author(s): Abrar H. Quadery , Baochi D. Doan , William C.Tucker , Adrienne R. Dove , Patrick K. SchellingInstitution(s): 1. University of Central Florida

413.11 – HST/WFC3 Imaging and Multi-WavelengthCharacterization of Edge-On Protoplanetary DisksIn recent years, the imaging detail in resolved protoplanetarydisks has vastly improved and created a critical mass of objects tosurvey and compare properties, leading us to betterunderstandings of system formation. In particular, disks with anedge-on inclination offer an important perspective, not only forthe imaging convenience since the disk blocks stellar light, but

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414 – Comets: Origins, Dynamics, and Characterization

scientifically an edge-on disk provides an otherwise impossibleopportunity to observe vertical dust structure of a protoplanetarysystem. In this contribution, we compare seven HST-imagededge-on protoplanetary disks in the Taurus, Chamaeleon andOphiuchus star-forming regions, making note the variation inmorphology (settled vs flared), dust properties revealed bymultiwavelength color mapping, brightness variability over yearstimescales, and the presence in some systems of a blue-coloredatmosphere far above the disk midplane. By using a uniformapproach for their analysis, together these seven edge-on

protoplanetary disk systems can give insights on evolutionaryprocesses and inform future projects that explore this criticalstage of planet formation.

Author(s): Carolina Gould , Hayley Williams , GaspardDucheneInstitution(s): 1. UC Berkeley

414.01 – Mineral abundances of comet 17P/Holmesderived from the mid-infrared spectrumDust grains of crystalline silicate, which is rarely presented in aninterstellar space, were found in cometary nuclei (Messenger etal. 1996, LPI, 27, 867; Wooden et al. 1999, ApJ, 517, 1058,references therein). It is thought that these crystalline silicateshad formed by annealing or condensations of amorphous grainsnear the Sun in the solar nebula, and incorporated into acometary nucleus in a cold region (farther than formation regionsof the crystalline silicates) by radial transportation in the solarnebula. It is considered that transportation mechanisms tooutside of the solar nebula were turbulent and/or X-wind. Anabundance of the crystalline dust grains was therefore expected tobe smaller as far from the Sun (Gail, 2001, A&A, 378, 192;Bockelée-Morvan et al. 2002, A&A, 384, 1107). Namely, theabundance ratio of the crystalline silicate in cometary dust grainsrelates a degree of mass transportation and a distance from theSun when cometary nucleus formed in the Solar nebula. The mass ratio of crystalline silicates of dust grains is determinedfrom by Si-O stretching vibrational bands of silicate grainsaround 10 μm using difference of spectral band features betweencrystalline and amorphous grains. We present the crystalline-to-amorphous mass ratio of silicate grains in the comet 17P/Holmesby using the thermal emission mode of the dust grains (Ootsuboet al. 2007, P&SS, 55, 1044) applied to the mid-infrared spectraof the comet. These spectra were taken by the COMICS mountedon the Subaru Telescope on 2007 October 25, 26, 27 and 28immediately after the great outburst of the comet (started onOctober 23). We discuss about formation conditions of thenucleus of the comet based on the derived mass ratio of silicategrains of the comet.

Author(s): Yoshiharu Shinnaka , MItsuru Yamaguchi ,Takafumi Ootsubo , Hideyo Kawakita , Itsuki Sakon , MitsuhikoHonda , Jun-ichi WatanabeInstitution(s): 1. ISAS/JAXA, 2. Kurume University, 3. KyotoSangyo University, 4. National Astronomical Observatory ofJapan, 5. University of Tokyo

414.02 – Spatial variations of polarization andcolor in comets 67P/Churyumov–Gerasimenko and2P/Encke and their interpretation with a model ofrough spheroidsIn November–December 2015 and April 2016, imagingphotometry and polarimetry of comet 67P/Churyumov–Gerasimenko was performed at the SAO RAS 6-m telescope withfocal reducer SCORPIO-2 (Rosenbush et al., MNRAS, 2017).Linear polarization maps resulted from the observations in 2015showed that the polarization near the nucleus was ~8%, droppedto ~2% at the distance ~5000 km, and then gradually increased to>8% at 40000 km, whereas the coma color (filters g_sdss andr_sdss) decreased with increasing distance from the nucleus.Similar trends were observed by Jewitt (AJ, 2004) for comet2P/Encke indicating similar processes in the coma of bothcomets. Dust color and polarization are mainly defined by theparticle size and composition. To check what could cause theobserved trends in color and polarization, we modeled lightscattering by cometary dust presenting it as a mixture ofrandomly oriented polydisperse rough spheroids of a variety ofaxis ratios. Kolokolova et al. (PSS, 2015) showed that such amodel can reproduce all cometary photopolarimetriccharacteristics. We performed the modeling with the software

package by Dubovik et al. (JGR, 2006). It has pre-calculatedkernels, which allow modeling the light scattering by differentsize and shape distributions of spheroids for 25 axis ratios from0.3 to 3.0 and 41 size bins for size parameter from 0.012 to 625.We selected a power law size distribution, describing it byefficient radius and standard deviation. The range of the particlesizes in the pre-calculated kernels, for the wavelengths of ourfilters, limited us by the efficient radii from 12 to 0.07 micronwith the standard deviation equal to 0.9. We report results of ourmodeling for compositionally various, including porous, particles.All of them confirm that as size of particles decreases, theirpolarization decreases until the particles become smaller than ~2micron, then it increases. Color shows a slight, but stable,decrease with the particle size, although this trend is disrupted bythe diffraction peak for particles ~1 micron. Thus, the polarizationand color changes observed in comets 67P and 2P can beexplained by the change in particle size; the composition affectsthe rate of those changes.

Author(s): Ludmilla Kolokolova , Himadri Das ,Oleksandra Ivanova , Vera K. Rosenbush , Nikolai KiselevInstitution(s): 1. Assam University, 2. Astronomical Instituteof Slovak Academy of Sciences, 3. Main AstronomicalObservatory (MAO) of the National Academy of Sciences ofUkraine , 4. Univ. of Maryland

414.03 – PSF Effects on the Apparent Morphologyof SOHO CometsSince the launch of the Solar and Heliospheric Observatory(SOHO) in 1995, over 3300 new sungrazing and other near-Suncomets have been discovered in its two Large Angle andSpectrometric Coronagraph (LASCO) instruments. The vastmajority of these objects are unobservable by non-solarobservatories due to their small size and proximity to the Sunwhen active. Most of these comets are members of the Kreutzgroup, but members of other groups, as well as comets notassociated with any known group, have also been observed.Recent successful ground observations have suggested that atleast some of these objects may actually be asteroidal in origin,but little is otherwise known about the physical nature of most ofthese objects. Further insight may be gleaned throughmorphological analyses of these objects in LASCO images toconstrain the size of any present coma or tail. We have developedan approach to compare the apparent morphology of comets asobserved by LASCO to that expected of a true point source. Wealso show how the point spread function (PSF) produced by thecomplex LASCO optical system can mislead interpretations of anapparent coma or tail.

Author(s): Qicheng Zhang , Karl BattamsInstitution(s): 1. U.S. Naval Research Laboratory

414.04 – The sunward continuum feature of Comet45P/Honda-Mrkos-PajdušákováWe will present results of our investigation of the sunwardcontinuum feature of comet 45P/Honda-Mrkos-Pajdušáková(HMP). HMP was observed in 2017 at the University of Arizona’sKuiper 61’’ telescope on Mount Bigelow on February 8, 9, 10, 16,and March 7 with the Mont4K camera, and at the Bok 2.3mtelescope on Kitt Peak on February 16 and 17 with the 90Primeimager. The heliocentric distance of HMP varied from 0.94 au to1.32 au, the geocentric distance from 0.08 au to 0.34 au, and thesolar phase angle from 15 deg to 119 deg during that time period.

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The sunward continuum feature is present in all our images.Position angle variations and radial spatial profiles of the feature,as well as deduced physical parameters will be discussed.

Author(s): Beatrice E. A. Mueller , Nalin H. Samarasinha ,Walter M. Harris , Alessondra Springmann , Cassandra Lejoly ,Julia Bodnarik , Ellen S. Howell , Erin L. Ryan , Jean-BaptisteKikwaya Eluo , M. Ryleigh Fitzpatrick , Zachary Tyler Watson ,Ricardo Maciel , Adriana Macieira Mitchell , James VernonScottiInstitution(s): 1. Planetary Science Institute, 2. SETI Institute,3. University of Arizona, 4. Vatican Observatory

414.06 – The Inner Coma Physical Environments ofEcliptic Comets 45P/Honda-Mrkos-Pajdusakova,2P/Encke, and 41P/Tuttle-Giacobini-KresakRevealed Through Long-Slit Spectroscopy at NASAIRTFUnderstanding the physical processes in the inner regions ofcometary atmospheres is vital for interpretation of molecularcometary emission at all wavelengths. Furthermore, becauseecliptic comets are continuously evaluated as space missiontargets, understanding their coma environments is a centraltheme in both enhancing the science return of past missions(EPOXI, Rosetta) and in selecting future mission targets. Withthis motivation, we report long-slit high-resolution observationsof H2O emission in the comae of three ecliptic comets observed inearly 2017: 45P/Honda-Mrkos-Pajdusakova, 2P/Encke, and41P/Tuttle-Giacobini-Kresak. Using the new crossed-dispersedspectrograph iSHELL at NASA IRTF, we detected a suite of waterrovibrational emission lines from these comets and measured thespatial distributions of H2O rotational temperatures andmolecular column densities. Both parameters are highlydiagnostic of the physical environment in cometary comae, thecompetition between cooling and heating processes in theseenvironments, and the presence (or lack thereof) of extendedcoma sources of gas-phase H2O. Comets 2P and 45P allowed arare glimpse into coma physics at small (< 0.6 AU) heliocentricdistances, where photochemical heating is particularly important,but direct H2O observations have been sparse. Our results add tothe small sample of spatial-spectral measurements of this type.They will be discussed in the context of coma physics modelsalong with prospects for investigations during the upcomingfavorable apparitions of ecliptic comets 21P/Giacobini-Zinner and46P/Wirtanen. We gratefully acknowledge support from theNASA Solar System Workings, Planetary Atmospheres, Earth andSpace Science Fellowship, Solar System Observations, EmergingWorlds, and Astrobiology Programs, and NSF Solar and PlanetaryResearch Grants. We are grateful to the entire IRTF staff for theirhelp with these challenging observations, most of which weredone during daytime.

Author(s): Boncho P. Bonev , Michael A. DiSanti , NathanRoth , Neil Dello Russo , Ronald J. Vervack , Erika L. Gibb ,Geronimo Luis Villanueva , Michael R. Combi , NicolasFougere , Hideyo Kawakita , Adam J. McKay , MohammadSaki , Martin Cordiner , Silvia Protopapa , Miguel de Val-BorroInstitution(s): 1. American University, 2. JHU-APL, 3. KyotoSangyo University, 4. NASA's GSFC, 5. University of Maryland,6. University of Michigan, 7. University of Missouri - St. Louis, 8.USRA

414.07 – Water production rates of recent comets(2016-2017) by SOHO/SWAN: 2P/Encke,41P/Tuttle-Giacobini-Kresak, 45P/ Honda-Mrkos-Pajdusakova, and C/2015 ER61 (PanSTARRS)The all-sky hydrogen Lyman-alpha camera, SWAN (Solar WindAnisotropies), on the SOlar and Heliospheric Observatory(SOHO) satellite makes observations of the hydrogen coma ofcomets. Most water molecules produced by comets are ultimatelyphotodissociated into two H atoms and one O atom producing ahuge atomic hydrogen coma that is routinely observed in the dailyfull-sky SWAN images in comets of sufficient brightness. Waterproduction rates are calculated using our time-resolved model

(Mäkinen & Combi, 2005, Icarus 177, 217), typically yieldingabout 1 observation every 2 days on the average for each cometover the brightest part of its apparition. Here we describe theprogress in analysis of observations of comets observed in 2016and 2017. These include comets 2P/Encke, 41P/Tuttle-Giacobini-Sresak, 45P/ Honda-Mrkos-Pajdusakova, and C/2015 ER61(PanSTARRS). A status update on the entire SOHO/SWANarchive of water production rates in comets will also be given. SOHO is an international cooperative mission between ESA andNASA. Support from grants NNX15AJ81G from the NASA SolarSystem Observations Planetary Astronomy Program and aprevious grant NNX13AQ66G from the NASA Planetary MissionData Analysis Program are gratefully acknowledged, as is supportfrom CNRS, CNES, and the Finnish Meteorological Institute(FMI).

Author(s): Michael R. Combi , Terhi Mäkinen , Jean-LoupBertaux , Eric Quémerais , Stephane FerronInstitution(s): 1. ACRI-st, 2. Finnish Meteorological Institute,Helsinki, 3. LATMOS/IPSI, Université de Versailles Saint-Quentin, 4. Univ. of Michigan

414.08 – Rotation and Morphology of Comet252P/LINEARComet 252P/LINEAR had an incredibly close approach early in2016 – minimum distance 0.036 AU on March 21 – that alloweddetailed investigation of its behavior. Analysis of observations ofthe morphology of 252P have resulted in several possiblerotational periods. Knight and Schleicher found that repetition offeatures in narrowband imaging from April 2016 indicated aperiod of 7.35 +/- 0.05 hr [1]. HST broadband data obtained by Liet al. in March and April partially fit the 7.35 hr period, but found5.5 hr was a better fit for the April 4 r’ band data [2]. Given thisdiscrepancy, additional observations may shed light on the truerotation state, and we present here the pieces of the puzzleobtained by our group. We observed 252P with the Kitt Peak National Observatory WIYN0.9 m telescope on 7 nights: May 2 – 5 and June 6,8,9, 2016 usinga Harris R filter. An oscillating jet is clearly visible in our data.While there is insufficient phase coverage to determine a best fitperiod from our data alone, we will present how our observationsof the morphology fit the two proposed periods. [1] Knight, M.M and D.G. Schleicher. AAS, DPS Meeting #48,id.207.02, 2016 [2] Li, J.-Y. et al. AAS, DPS Meeting #48, id.206.03, 2016.

Author(s): Laura Woodney , Charles A. Schambeau , YangaR. FernandezInstitution(s): 1. Cal State Univ., San Bernardino, 2.University of Central Florida

414.09 – Spectroscopic Profiles of Comets Garraddand McNaught We have used the integral-field unit spectrograph (the Georgeand Cynthia Mitchell Spectrograph) on the 2.7m Harlan J. Smithtelescope at McDonald Observatory to obtain spectroscopicimages of the comae of several comets. The images were obtainedfor various radical species (C2, C3, CN, NH2). Radial andazimuthal average profiles of the radical species were created toenhance any observed cometary coma morphological features. Wecompare the observed coma features across the observed speciesand over the different observation periods in order to constrainpossible rotational states of the observed comets, as well asdetermine possible source differences in the coma between theobserved radical species. We will present results for severalcomets, including C/2009 P1 (Garradd) and 260P (McNaught).

Author(s): Ien Harris , Donna M. Pierce , Anita L. CochranInstitution(s): 1. Mississippi State University, 2. University ofTexas

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414.10 – Comet 103P/Hartley 2's Volatile SourceRegions and Temporal Dependencies as Derivedfrom HRI-IR Observations During the Deep ImpactExtended InvestigationDuring the November 4, 2010, flyby of comet 103P/Hartley 2, theHRI-IR spectrometer (1.05–4.85 μm) onboard the Deep ImpactFlyby spacecraft acquired a unique rotational data set with nomore than two hours separation between observations (A’Hearnet al. 2011). The frequent infrared scans enabled time variabilityof the coma composition and distribution to be studied. GaseousH O and CO , at 2.7 μm and 4.3 μm, respectively, were thedominant molecular emissions detected in these spectra and haddistinct spatial distributions from one another throughoutHartley 2's rotational period, suggesting different releasemechanisms or sources for the two volatiles. In contrast, based onthe positive correlation of the distribution of CO vapor and thatof water-ice particles in the near-nucleus coma, also detected inthe infrared data, it was inferred that sublimation of subsurfaceCO drives the majority of the outgassing activity of Hartley 2'snucleus near perihelion rather than H O sublimation. We utilizea subset of these data centered on closest approach and includingone rotation before and after (± 18 hr) to further explorecorrelations among the volatiles and the role of extended sourcesas well as correlations of volatile activity with rotation andillumination.

References A'Hearn, M.F. et al. 2011. Science 332, 1396–1400.

Author(s): Lori M. Feaga , Jessica M. Sunshine , SilviaProtopapa , Tony FarnhamInstitution(s): 1. Univ. of Maryland

414.11 – Water ice grains in comet C/2013 US10(Catalina)Knowledge of the the physical properties of water ice in cometarynuclei is critical in determining how the Solar System was formed.While it is difficult to directly study the properties of water ice incomet nuclei, we can study comet interiors through their comae.Cometary activity makes the interiors of these objects availablefor characterization. However, the properties (grain size,abundance, purity, chemical state) of water-ice grains detected inthe coma do not necessarily represent the characteristics of thewater ice on the surface and/or in the interior of the nucleus. Thisis due to the potential physical and chemical evolution of theemitted material. Once in the coma, water-ice grains are heatedby sunlight, and if temperatures are warm enough, they sublime.In this case, their sizes and potentially their ice-to-dust fractionsare reduced.

We present IRTF/SpeX measurements of the Oort cloud cometC/2013 US10 (Catalina), which reached perihelion in Nov 2015 ata heliocentric distance R =0.822 AU. Observations of US10 wereacquired on UT 2014-08-13, 2016-01-12, and 2016-08-13(R =5.9, 1.3, and 3.9 AU). This set of measurements, spanning abroad range in R , are rare and fundamental for estimating howice grains evolve in the coma. The spectrum obtained close toperihelion is featureless and red sloped, which is consistent with adust-dominated coma. Conversely, the spectra acquired onAugust 2014 and 2016 display neutral slopes and absorptionbands at 1.5 and 2.0 μm, consistent with the presence of water-icegrains. These variations in water ice with heliocentric distance arecorrelated with sublimation rates. Additionally, themeasurements obtained at 5.8 AU and 3.9 AU are nearlyidentical, suggesting that water-ice grains, once in the coma, donot sublime significantly. Therefore, the properties of these long-lived water-ice grains may represent their state in the nucleus orimmediately after insertion into the coma. We will presentradiative transfer models of the data and interpret the results inthe context of spacecraft data of cometary nuclei, and of our on-going compositional survey of water-ice grain halos in cometarycomae.

This work was funded by NASA SSO, NASA PAST and NASASOFIA grants.

Author(s): Silvia Protopapa , Michael S. P. Kelley , BinYang , Charles E. Woodward , Jessica M. SunshineInstitution(s): 1. European Southern Observatory, 2.Minnesota Institute for Astrophysics, University of Minnesota, 3.University of Maryland

414.12 – A Tale of “Two” Comets: The PrimaryVolatile Composition of Comet 2P/Encke AcrossApparitions2P/Encke is one of the most frequently observed comets inhistory, yet its highly favorable 2017 apparition allowed the firstcomprehensive comparison of primary volatile abundances in thesame comet across multiple apparitions. It offered an opportunityto address pressing questions in cometary science, includinginvestigating evolutionary and/or heliocentric distance effects onvolatile production, sampling the hypervolatiles CO and CH inan ecliptic comet, and probing volatile release at small R (0.4AU). The faint nature of ecliptic comets and low geocentricvelocity during most apparitions make these observations in thenear-infrared rare (in particular at small R ) and of highscientific impact. On March 21, 22, and 25 we characterized thevolatile composition of 2P post-perihelion using the high-resolution near-infrared iSHELL spectrograph at the 3 m NASA-IRTF on Maunakea, HI. We detected fluorescent emission fromeight primary volatiles (H O, CO, C H , CH OH, CH , H CO,NH , and HCN) and three secondary volatiles (OH*, NH , andCN). Upper limits were derived for OCS and C H . We reportrotational temperatures, production rates, and mixing ratios(with respect to H O). Compared to median relative abundancesin comets observed in the near-infrared to date, mixing ratios oftrace gases in 2P/Encke are depleted for all detected speciesexcept HCN and NH , which are consistent with the median. Thedetection of the hypervolatiles CO and CH is particularly notablegiven the paucity of measurements of these species in eclipticcomets. We observed significant differences in primary volatilecomposition compared to published pre-perihelion results fromthe 2003 apparition at larger R (~1.2 AU) (Radeva et al. 2013).We will discuss possible mechanisms for these effects, includingasymmetry about perihelion in 2P (Sekanina 1988a, b), anddiscuss the results in the context of findings from the Rosettamission and ground-based studies of comets. This work wassupported by the NASA Earth and Space Science Fellowship,Solar Workings, Solar System Observations, and AstrobiologyPrograms, and NSF Solar and Planetary Science Grants.

Author(s): Nathan X. Roth , Erika L. Gibb , Boncho P.Bonev , Michael A. DiSanti , Neil Dello Russo , Ronald J.Vervack , Adam J. McKay , Hideyo KawakitaInstitution(s): 1. Catholic University of America, 2. JHU-APL,3. Kyoto Sangyo University, 4. NASA GSFC, 5. University ofMissouri-St. Louis

414.13 – Search for CH D in Comets withNIRSPEC/Keck II: D/H Ratios in MethaneCometary volatiles are expected to be more enriched indeuterated species (e.g., HDO for water) and their D/H ratioslarger than that of proto-solar H gas (~2 x 10 ) if cometaryvolatiles formed via chemical reactions at very low temperaturesin the pre-solar molecular cloud and/or in the solar nebula.However, some cometary volatiles might have been chemicallyprocessed in warmer regions of the solar nebula, where the D/Hratios are expected to equilibrate with the proto-solar value,before being transported to the comet-forming region by theradial/vertical mixing. The D/H ratios of cometary water observed so far are enrichedwith respect to the proto-solar value, ranging from 1.6 x 10 to5.3 x 10 . However, because different species ultimately storedas comet ices likely have different chemical formation pathways(and perhaps distinct formative regions), it is important to extendthe searches for isotopologues to additional molecules. Here we report the upper limits of D/H ratios in methane,

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deduced from the CH D/CH ratio for several bright cometsobserved by Keck II with NIRSPEC. The much lower sublimationtemperature of methane (~30 K) compared to water (~150 K)means that methane molecules processed in the solar nebulamight not recondense efficiently in the inner warmer part ofcomet-forming regions. We discuss our results in the context ofthe formation conditions of cometary ices and the contribution ofinterstellar ices based on comparisons with astrochemicalmodels.

Author(s): Hideyo Kawakita , Neil Dello Russo , Ronald J.Vervack , Harold A Weaver , Boncho P. Bonev , Erika L. Gibb ,Michael A. DiSantiInstitution(s): 1. American University, 2. KoyamaAstronomical Observatory, 3. NASA's GSFC, 4. The JohnsHopkins University APL, 5. University of Missouri-St.Louis

414.14 – Revisiting Comets C/2012 F6 (Lemmon)and C/2012 S1 (ISON) with ALMA AutocorrelationsThe Atacama Large Millimeter/submillimeter array (ALMA) is apowerful tool for high-resolution mapping, but as aninterferometer it is insensitive to large-scale structures due to thelack of zero-spacing (autocorrelation/single-dish) measurements.This is especially limiting in studies of cometary comae, whichcan extend up to hundreds of arcseconds. In this work, we makeuse of ALMA autocorrelations, treating the entire ALMA array asa collection of single-dish telescopes, to study the large comae ofcomets C/2012 F6 (Lemmon) and C/2012 S1 (ISON). This hassignificantly improved our spectral line sensitivity, allowing forthe detection of new molecules in ISON's coma, including HCO+and H(13C)N.

We also present results from the combined use of ALMAautocorrelation (single dish) and cross-correlation(interferometric) data to create a more complete picture of thecoma gas distribution in Lemmon. Since its initial detection inHyakutake (Irvine et al. 1996), the origins of cometary HNC havebeen under investigation (Irvine et al. 1998; Rodgers & Charnley2001, 2005; Lis et al. 2008). It might be produced from thedegradation of a solid organic material. More measurements ofthe HNC parent scale length are needed to help understand thesource of HNC. Using ALMA autocorrelation data, we follow upon the detection of HNC in comet Lemmon by Cordiner et al.(2014) and, assisted by newly-developed radiativetransfer/excitation models, provide an analysis of its distributionin this comet.

References: Irvine, W. M., Bockelee-Morvan, D., Lis, D. C., et al. 1996, Nature,383, 418; Irvine, W. M., Bergin, E. A., Dickens, J. E., et al. 1998, Nature,393, 547; Rodgers, S. D., & Charnley, S. B. 2001, MNRAS, 323, 84; ---. 2005, MNRAS, 356, 1542; Lis, D. C., Bockelee-Morvan, D., Boissier, J., et al. 2008, ApJ, 675,931; Cordiner, M. A., Remijan, A. J., Boissier, J., et al. 2014, ApJL,792, L2

Acknowledgments: NASA’s Astrobiology Program supported thiswork through the Goddard Center for Astrobiology.

Author(s): Maureen Yukiko Palmer , Martin Cordiner ,Miguel de Val-Borro , Steven B. Charnley , Michael J. MummaInstitution(s): 1. NASA Goddard Space Flight Center

414.15 – Cometary Orbital Trends with SpitzerCometary mass-loss, i.e., activity, is nominally driven by thesublimation of volatiles. The three most abundant volatiles in theaverage comet are water, carbon dioxide, and carbon monoxide.Of the three, CO is the most challenging to measure directly, andcannot be observed from the ground due to telluric absorptions.Owing to observations made by several space telescopes,including ISO, Spitzer, Akari, and WISE, as well as spacecraftmissions to comets, we have a good estimate of the range of CO

abundances in the comet population (~5-30% with respect towater). However, spacecraft missions have shown that theproduction of H O, CO and CO are not fully understood. At eachof three well-studied comets (9P/Tempel 1, 103P/Hartley 2, and67P/Churyumov-Gerasimenko), CO and H O have had distinctdistributions in the coma, suggesting different releasemechanisms or heterogeneous source regions. For 67P, thisresulted in relative abundances that varied along the comet’sorbit, demonstrating that a single measurement of the CO -to-water abundance ratio in a cometary coma is not necessarilyreflective of the bulk nucleus composition. To improve our understanding of CO production in comets, webegan a time-domain survey of 24 targets with the Spitzer SpaceTelescope in 2015. Most targets are observed multiple times onmonth-long timescales, and some comets are observed on year-long timescales. We present a summary of the Spitzer project atthe 2.5-year mark, including total CO production rates atheliocentric distances beyond 3 au, number and size of CO activeareas, and seasonal variations in dust and CO production. Wealso compare the Spitzer results to comets observed in theNEOWISE survey (Bauer et al. 2017, this meeting). TheNEOWISE data is complementary in that it provides observationsof many targets with limited selection biases, whereas the OrbitalTrends Survey observes a small number of targets in detail. This work is based on observations made with the Spitzer SpaceTelescope, which is operated by the Jet Propulsion Laboratory,California Institute of Technology under a contract with NASA.Support for this work was provided by NASA through an awardissued by JPL/Caltech.

Author(s): Michael S. Kelley , Dennis Bodewits , Lori M.Feaga , Matthew M. Knight , Adam McKay , Colin Snodgrass ,Diane H. Wooden , James M BauerInstitution(s): 1. NASA Ames Research Center, 2. NASAGoddard Spaceflight Center, 3. The Open University, 4. Univ. ofMaryland

414.16 – NEOWISE Reactivated Mission CometaryCO+CO2: Preliminary Results from Years 1through 3NEOWISE has utilized the WISE spacecraft data to provided anunpresidented number of radiometrically determined diametersand mid-infrared photometric observations of small bodies.During the WISE prime mission (January 2010 - January 2011)over 158000 solar system objects were detected by thespacecraft[1] before it was placed in hibernation in February of2011. Of these, 164 comets were detected and characterized withrespect to their dust production and particle size[2,3], CO+CO2production[4], and diameters[5]. The WISE spacecraft was reactived in 2013 and survey operationswere restarted with the express purpose of searching for andcharacterizing solar system objects[6]. Re-named NEOWISE, thespacecraft continues to image the sky for Near-Earth objects andother small bodies at wavelengths of 3.4 and 4.6 μm, and is nowinto year 4 of its reactivated survey. The first 3 years of theNEOWISE reactivated mission produced detections of 11,800objects[7,8], with a larger fraction of comets than during thecryogenic mission. Over 110 comets have been detected in thefirst 3 years of the reactivated survey. With NEOWISE'swavelength coverage, the survey is sensative to CO emissionlines that are obscured by Earth's atmosphere and faint COemission that is not easily detected from groundbasedobservations. We will present a preliminary analysis of this 3-yeardata set of comets regarding CO and CO production rates,tracing the behavior of these emissions at different heliocentricdistances for several comets and for the ensemble of comets thatshow excess emission relative to dust that is indicative ofCO+CO emission, approximately two thirds of the entire sample.We will also place these in the context of the Spitzer mission dataset of targeted comet observations[9].

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[1] Mainzer, A. et al. 2011a, ApJ, 731, 53. [2] Kramer, E. 2014, PhD Dissertation, Univ. Central Florida. [3] Kramer, E. et al. 2017, ApJ, 838, 58. [4] Bauer, J. M. et al. 2015, ApJ, 814, 85. [5] Bauer, J. M. et al. 2017, J, 154, 53. [6] Mainzer, A. et al. 2014, ApJ, 792, 30. [7] Cutri, R. M. et al. 2017(http://wise2.ipac.caltech.edu/docs/release/neowise/expsup) [8] Masiero, J. et al. 2017, submitted. [9] Kelley, M. S. et al. 2017, AAS DPS meeting.

Author(s): James M. Bauer , Tommy Grav , Amy K.Mainzer , Emily A. Kramer , Joseph R. Masiero , Michael S.Kelley , Carrie R Nugent , Sarah M. Sonnett , Yanga R.Fernandez , Casey M. Lisse , Karen Jean Meech , Joshua DavidRosser , Russell G. Walker , Edward L. WrightInstitution(s): 1. Applied Physics Laboratory, 2. Dept. ofAstronomy, University of Maryland, 3. Institute for Astronomy,Univ. of Hawaii, 4. IPAC/Caltech, 5. Jet Propulsion Laboratory,6. Monterey Institute for Research in Astronomy (MIRA), 7.Planetary Science Institute, 8. UC, Los Angeles, 9. Univ. ofCentral Florida, 10. Univ. of RochesterContributing team(s): NEOWISE Team

414.17 – Correlation Between Cometary Gas/DustRatios and Heliocentric DistanceWe compiled CO-based gas/dust ratios for several comets out toheliocentric distances, r , of 8 au to probe whether there is anoticeable change in comet behavior over the range that water-icesublimation starts. Previously, gas/dust ratios were calculated foran ensemble of comets using Q(CO )/efp values derived frominfrared measurements, which showed that the gas/dust ratiofollows a r within 4 AU, but is flat at greater distances (Baueret al. 2015). Our project focuses on gas/dust ratios for which COis assumed to be the dominant gas, in order to test whethersimilar breaks in slope occur for CO. The gas/dust ratios werecalculated from measurements of CO production rates (mostlyfrom millimeter-wavelength spectroscopy) and reflected sunlightof comets (mostly via reported visual magnitudes of dustycomets). We present our new CO-based gas/dust ratios atdifferent heliocentric distances, compare them to existing CO -based gas/dust ratios, and discuss implications for CO-driven andCO -driven activity. We discuss O.H. acknowledges support fromthe Hartmann Student Travel Grant program. M.W.acknowledges support from NSF grant AST-1615917.

Author(s): Olga Harrington , Maria Womack , NathanLastraInstitution(s): 1. University of South Florida

414.19 – The Relationship of HCN, C H , & H O inComets: A Key Clue to Origins?Background: HCN, C H , and H O are three of the bestcharacterized volatiles in comets. It is often assumed that all threeare primary volatiles, native to the nucleus. Here, we comparetheir properties in 26 comets (9 JFC and 17 Oort-cloud), making 6points: 1. Both HCN and C H are poor proxies for water production.The production rate ratio (Q-ratio) of each trace gas relative towater varies by a factor of six among these comets. 2. All 26 comets have Q-ratios HCN/C H > 0.1. In 18 comets theQ-ratios HCN/H O and C H /H O are correlated, with a meanratio of 0.33. In 6 comets undergoing complete disruption, this Q-ratio exceeds 0.5. 3. Q-ratios HCN/C H are not correlated with Q(H O), nor arethey correlated with dynamical class (Oort cloud vs. JFC). 4. The nucleus-centered rotational temperatures measured forH O and other primary species (C H , CH OH) usually agreewithin error, but those for HCN are often slightly cooler. Couldthis mean that HCN is not fully developed in the warm near-nucleus region, and instead is at least in part a product species? 5. With its strong dipole moment and H-bonding character, HCNshould be linked more strongly in the nuclear ice to othermolecules with similar properties (H O, CH OH), but instead its

spatial release in some comets seems strongly coupled to volatilesthat lack a dipole moment and thus do not form H-bonds(methane, ethane). Is HCN produced in part from an apolarprecursor? 6. ALMA maps of HCN and the dust continuum show a slightdisplacement in their centroids. Is this the signature of extendedproduction of HCN? HCN as a product species: Points 4-6 suggest that HCN mayhave a significant distributed source. The astrochemical speciesammonium cyanide is a strong candidate for this HCN precursor;at moderately low temperatures (< 200K) NH CN is a stablesolid, but it dissociates into HCN and NH when warmed.Disruption could eject macroscopic solid NH CN into the comawhere subsequent warming and release could augment the comacontent of NH and HCN. Acknowledgments NASA’s Planetary Astronomy andAstrobiology Programs supported this work.

Author(s): Michael J. Mumma , Steven B. Charnley , MartinCordiner , Lucas Paganini , Geronimo Luis VillanuevaInstitution(s): 1. NASA's GSFC

414.21 – Modeling Subsidence-Like Events onCometary NucleiThere is ample evidence, particularly from the Rosetta mission,that cometary nuclei have very low tensile strength.Consequently, morphological changes are expected to occur,caused by buildup of pressure due to gas release in the interior ofthe nucleus. Such changes have been observed on the surface ofcomet 67P/Churyumov-Gerasimenko, as reported for example byGroussin et al.(2015). A mechanism for explaining comet surfacedepressions has been recently proposed by Prialnik & Sierks(2017). Here we report on a numerical study, elaborating on thismechanism. Essentially, the model considers a cometary nucleuscomposed of a low-density mixture of ice and dust, assuming thatthe ice is amorphous and traps volatile gasses, such as CO andCO2. The model assumes that the tensile strength of thesubsurface material is low and that the surface is covered by athin crust of low permeability. As the comet evolves, theamorphous ice crystallizes, and the crystallization front recedesfrom the surface, releasing the trapped gasses, which accumulatebeneath the surface, building up pressure. The gas pressureweakens the material strength, but sustains the gas-filled layeragainst hydrostatic pressure. Eventually, the gas will break itsway through the outer crust in an outburst. The rapid pressuredrop may cause the collapse of the gas depleted layer, as seen onthe nucleus of 67P/Churyumov-Gerasimenko. This mechanism issimilar to subsidence events in gas fields on earth. We have performed quasi-3D numerical simulations in anattempt to determine the extent of the area that would be affectedby such a mechanism. The frequency of such subsidence eventsand the depth of the collapse are investigated as functions of solarangle and spin axis inclination. The necessary conditions foroutburst-induced collapse are determined and confronted withobservations. References: Groussin, O., Sierks, H., et al. 2015, A&A, 583, A35 Prialnik, D. & Sierks, H., 2017, MNRAS, in press

Author(s): Eric Rosenberg , Dina PrialnikInstitution(s): 1. Eastern R&D Center, 2. Tel Aviv University

414.23 – Evidence for self-gravity in a massive HillsCloudThe Hills Cloud is a hypothesized disk of icy comets, asteroidsand minor planets left over from the formation of the SolarSystem. Spanning ~250 - 10 AU it is relatively isolated from thegravitational effects of the inner Solar System and outer Galaxy.As the least observable component of the Oort Cloud, predictionsfor its mass span at least two orders of magnitude, typicallyranging from 0.1 - 10 Earth masses. Here we show that self-

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gravity acting between bodies within the Hills Cloud dramaticallychanges their orbital distribution (the inclination instability;Madigan & McCourt, 2016). Inclinations increase exponentially,eccentricities lower (detaching the bodies from the inner SolarSystem) and orbits cluster in argument of perihelion. We showhow the orbits of Sedna and other high perihelion objects can beused to constrain the mass of the Hills cloud.

Author(s): Alexander Zderic , Ann-Marie Madigan , JacobFleisigInstitution(s): 1. University of Colorado Boulder - JILA

414.24 – Arecibo radar observations of 41P/Tuttle-Giacobini-Kresák constrain the nucleus size androtationWe obtained S-band (2380 MHz, 12.6-cm) radar echos from thenucleus of comet 41P/Tuttle-Giacobini- Kresák using the AreciboObservatory in March and May of 2017, obtaining constraints onits size and rotation state. We also reported delay-Dopplerastrometric orbit corrections accurate at the 2 microsecond and0.2 Hz level. The resulting orbital solution requires a significantnon-gravitational acceleration to explain the pre- and post-perihelion observations. The radar bandwidth is a measure of theapparent differential motion of the nucleus about its rotation axis,projected into the line of sight. The apparent bandwidth of thecomet nucleus was 30% larger in March than in May, but did notchange significantly during May 5-14. A change in apparentperiodicity from 19.9 to 27 hours in March, reported by Farnhamet al., (CBET4375, 2017) and Knight et al., (CBET4377, 2017) wasdeduced from CN jet morphology. Bodewits et al. (CBET4400,2017) report a repetition period of 42 +/- 1 hours by May 9 basedon photometry using the UVOT of the Swift Gamma-Ray BurstMission. If this is the nucleus rotation period, our observation onMay 9 requires the diameter of the nucleus to be at least 900m. Alarger size is possible but requires an extremely low radar albedoto match the measured signal to noise ratio. If the nucleus is in anexcited rotation state (non-principal axis rotation), as seemslikely, these measurements will strongly constrain the nucleussize and rotation state. Further analysis will be presented.

Author(s): Ellen S. Howell , Cassandra Lejoly , Patrick A.Taylor , Edgard G. Rivera-Valentin , Luisa Fernanda Zambrano-Marin , Jon D. Giorgini , Michael C. Nolan , Nalin H.Samarasinha , Beatrice E. A. Mueller , Betzaida Aponte-Hernandez , Sriram Saran Bhiravarasu , Carolina RodriguezSanchez-Vahamonde , Walter M. HarrisInstitution(s): 1. Jet Propulsion Laboratory, 2. PlanetaryScience Institute, 3. University of Arizona, 4. USRA/AreciboObservatory

414.25 – Determination of the rotational state ofcomet 103P/Hartley 2

We present the results based on our ongoing efforts to derive therotational state of comet 103P/Hartley 2 that satisfy spacecraftand groundbased observations. 103P/Hartley 2 was the target ofthe NASA DIXI mission and is in a non-principal axis rotationalstate. The non-principal axis rotational state of the nucleus andits temporal changes make this a challenging endeavor. However,determination of the rotational state is critical for explaining theobservations and for characterizing the nucleus. In this study, wefocus on the following observations. 1. The lightcurve as observed by the spacecraft. We reanalyze thedata using spatially fixed aperture sizes to determine theunderlying periodicities and their temporal behavior. 2. The CN coma morphology observed from the ground and theirspatial and temporal evolution. 3. The continuum features observed from the ground and fromthe spacecraft and their spatial and temporal evolution. 4. The radar observations and constraints on the rotational state. These observations are compared with coma simulations anddynamical considerations. The current status of the investigationand the results will be presented at the meeting with a description

of the additional work to be carried out in the coming year. This research is supported by the NASA DDAP Program.

Author(s): Nalin H. Samarasinha , Beatrice E. A. Mueller ,Michael J. S. Belton , Andrew Henrici , Jose BarreraInstitution(s): 1. Belton Space Exploration Initiatives, LLC, 2.Planetary Science Institute

414.26 – LRO-LAMP Detection of Atomic Oxygen,Carbon, and Hydrogen in the Pre-Perihelion Comaof Comet C/2013 A1 Siding SpringComet C/2013 A1 Siding Spring became the first comet observedby the Lyman Alpha Mapping Project (LAMP), an ultravioletimaging spectrograph onboard the Lunar Reconnaissance Orbiter(LRO). A close encounter between Siding Spring and Mars onOctober 19, 2014 provided a unique opportunity for LAMPmeasurements to contribute to the broader campaign ofobservations. Observations of the coma were obtained in twoconsecutive LRO orbits on September 5, 2014, five weeks beforethe close encounter and near in time to Earth closest approach.Emissions from the coma were spatially resolved in three detectorrows. Spectral signatures of atomic species oxygen, carbon, andhydrogen were identified. These data are useful for determiningthe distribution of the atomic dissociation products as a functionof distance from the comet’s center. To our knowledge thesemeasurements of several species fill a gap in tracking the gasproduction rates versus time for the observational campaign.

Author(s): Lizeth O. Magana , Kurt D. Retherford , Paul D.Feldman , Caleb SeifertInstitution(s): 1. Johns Hopkins University, 2. SouthwestResearch Institute, 3. St. Paul American School, 4. University ofTexas at San AntonioContributing team(s): LRO-LAMP

414.27 – 3D high-resolution radar imaging of smallbody interiorsAnswering fundamental questions about the origin and evolutionof small planetary bodies hinges on our ability to image theirinterior structure in detail and at high resolution (Asphaug,2009). We often infer internal structure from surfaceobservations, e.g. that comet 67P/Churyumov-Gerasimenko is aprimordial agglomeration of cometesimals (Massironi et al.,2015). However, the interior structure is not easily accessiblewithout systematic imaging using, e.g., radar transmission andreflection data, as suggested by the CONSERT experiment onRosetta. Interior imaging depends on observations from multipleviewpoints, as in medical tomography. We discuss radar imaging using methodology adapted fromterrestrial exploration seismology (Sava et al., 2015). Weprimarily focus on full wavefield methods that facilitate highquality imaging of small body interiors characterized by complexstructure and large contrasts of physical properties. We considerthe case of a monostatic system (co-located transmitters andreceivers) operated at two frequency bands, centered around 5and 15 MHz, from a spacecraft in slow polar orbit around aspinning comet nucleus. Assuming that the spin period issignificantly (e.g. 5x) faster than the orbital period, thisconfiguration allows repeated views from multiple directions(Safaeinili et al., 2002) Using realistic numerical experiments, we argue that (1) thecomet/asteroid imaging problem is intrinsically 3D andconventional SAR methodology does not satisfy imaging,sampling and resolution requirements; (2) imaging at differentfrequency bands can provide information about internal surfaces(through migration) and internal volumes (through tomography);(3) interior imaging can be accomplished progressively as dataare being acquired through successive orbits around the studiedobject; (4) imaging resolution can go beyond the apparent radarfrequency band by deconvolution of the point-spread-functioncharacterizing the imaging system; and (5) exploiting the known(and complex) exterior shape of the studied body facilitates high-

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resolution imaging and tomography comparable with what couldbe accomplished by bi/multi-static systems.

Author(s): Paul Sava , Erik AsphaugInstitution(s): 1. Colorado School of Mines, 2. University ofArizona

414.28 – Lifetimes and f-values of the D Σ ← X Πsystem of OH and OD The OH radical is abundant in the interstellar medium andcometary comae, where it plays a significant role in thephotochemical cycle of water. Also, the oxidising potential of theEarth atmosphere is influenced by this molecule. The OH lifetimein the presence of ultraviolet radiation is of prime interest in allthese locations. The vacuum-ultraviolet absorption of the D Σ← X Π system contributes to a reduction of this lifetime. It alsoprovides an independent way to observe the OH molecule in theinterstellar medium. But a reliable oscillator strength (f-value) isneeded.

Vacuum-ultraviolet absorption of the D Σ ← X Π system ofOH and OD was recorded with high spectral resolution in aplasma-discharge radical source and using synchrotron radiation

coupled to the unique ultraviolet Fourier-transform spectrometeron the DESIRS beamline of synchrotron SOLEIL. Line oscillatorstrengths are absolutely calibrated with respect to the well-knownA Σ ← X Π system. The new oscillator strength decreases thebest-estimate lifetime of OH in an interstellar radiation field andreduces its uncertainty. We also measured line broadening of theexcited D Σ v=0 and 1 levels for the first time and find a lifetimefor these states which is 5 times shorter than theoreticallypredicted. This new data will aid in the interpretation of astronomicalobservations and help improve photochemical models in manycontexts.

Author(s): Alan Heays , Nelson de Oliveira , Bérenger Gans ,Kenji Ito , Séverine Boyé-Péronne , Stéphane Douin , KevinHickson , Laurent Nahon , Jean-Christophe LoisonInstitution(s): 1. ASU School of Earth and Space Exploration,2. Institut des Sciences Moléculaires d’Orsay, 3. Institut desSciences Moléculaires, Univ. Bordeaux, 4. Synchrotron SOLEIL

415.01 – Surface Activity Distributions of Comet67P/Churyumov-Gerasimenko Derived fromVIRTIS ImagesThe outgassing mechanism of comets still remains a criticalquestion to better understand these objects. The Rosetta missiongave some insight regarding the potential activity distributionfrom the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, Fougere et al. (2016, Astronomy & Astrophysics,Volume 588, id.A134, 11 pp and Monthly Notices of the RoyalAstronomical Society, Volume 462, Issue Suppl_1, p.S156-S169)used a spherical harmonics inversion scheme with in-situmeasurements from the ROSINA instrument to derive mappingof the broad distribution of potential activity at the surface of thenucleus. Marschall et al. (2016, Astronomy & Astrophysics, doi:10.1051/0004-6361/201730849) based on the appearance of dustactive areas suggested that the so-called “neck” region andregions with fractured cliffs and locally steep slopes show moreactivity than the rest of comet 67P’s nucleus. Using in situROSINA measurements from a distance makes it difficult todistinguish between these two scenarios because the fastexpansion of the gas and large molecular mean free pathsprevents distinguishing small outgassing features even when thespacecraft was in bound orbits within 10 km from the nucleus. Inthis paper, we present a similar numerical inversion approachusing VIRTIS images, which should better probe the very innercoma of comet 67P and give more detailed information about theoutgassing activity.

Support from contracts JPL #1266314 and #1266313 from the USRosetta Project and grant NNX14AG84G from the NASAPlanetary Atmospheres Program are gratefully acknowledged.

Author(s): Nicolas Fougere , Michael R. Combi , ValeriyTenishev , Alessandra Migliorini , Dominique Bockelee-Morvan , Uwe Fink , Gianrico Filacchione , Giovanna Rinaldi ,Fabrizio Capaccioni , Gabor Toth , T. I. Gombosi , Kenneth C.Hansen , Zhenguang Huang , Yinsi ShouInstitution(s): 1. National Institute of Astrophysics, 2. Obs. deMeudon, 3. Univ. of Arizona, 4. University of MichiganContributing team(s): VIRTIS Team

415.02 – Large scale morphological changes in theHapi region on comet 67P/Churyumov-GerasimenkoThe Hapi region is located on the northern hemisphere of comet67P/C-G at the neck that joins the two lobes of the nucleus. Itprimarily consists of granular material that is unresolved at 0.35m/pixel resolution and that forms a smooth surface with smallslopes with respect to local gravity. The OSIRIS cameras on the

ESA spacecraft Rosetta observed Hapi regularly since itsrendezvous with the comet in August 2014. No changes were seenduring the first five months in orbit but on December 30, 2014,two spots appeared in Hapi. Over the course of two months theygrew gradually into a 110 by 70 meter shallow depression with adepth of about 0.5 meters. We use OSIRIS observations tocharacterize the morphology and spectrophotometry of theregion. We use measurements of the thermal emission of thecomet by the MIRO millimeter and submillimeter radiometer incombination with thermophysical modeling to characterize thesurface temperature, near surface temperature gradient, andthermal inertia of the region. The formation mechanism of thedepression is discussed in view of these empirical data.

Author(s): Bjorn Davidsson , Seungwon Lee , Paul vonAllmen , Peter Schloerb , Mark Hofstadter , Holger Sierks ,Cesare Barbieri , Samuel Gulkis , Horst Uwe Keller , DetlefKoschny , Philippe Lamy , Hans Rickman , Rafa RodrigoInstitution(s): 1. ESA/ESTEC, 2. International Space ScienceInstitute, 3. Jet Propulsion Laboratory, 4. Laboratoired'Astrophysique de Marseille, 5. Max-Planck-Institut fürSonnensystemforschung, 6. Technische UniversitätBraunschweig, 7. Univ. Massachusetts, 8. Univ. Padova, 9.Uppsala universityContributing team(s): The MIRO Team, The OSIRIS Team

415.03 – Analysis of observations of the Imhotepregion of 67P/C-G performed by MIRO/Rosetta in2014 and 2016 and derived constraints on the closesubsurface propertiesAfter the arrival of the Rosetta spacecraft at the 67P/Churyumov–Gerasimenko comet in August 2014, and continuinguntil the end of mission in September 2016, the MIRO(Microwave Instrument for Rosetta Orbiter, Gulkis et al. [2007])performed broadband, continuum measurements at 188 GHz (1.6mm wavelength) and 562 GHz (0.5 mm wavelength) of thenucleus and coma. The instrument measured the thermalemission from the close subsurface over a wide range of spatialresolutions (20 – 500 m) and emission angles. Themeasurements revealed a seasonal and diurnal variation of thesubsurface temperatures indicating that the submillimeterradiation originates from depths comparable to the diurnalthermal skin depth [Gulkis et al. 2015]. The observations werefound to be consistent with very low thermal inertia values overmost of the surface (between 10–60 J K−1 m−2 s-1/2, consistentwith a thermally insulating powdered surface), and they suggestvertical heterogeneities and the possible presence of ice withinthe upper few centimeters of the surface (Schloerb et al. [2015];Choukroun et al. [2015]). In addition to these global observationsmany studies are being done on specific parts of the nucleus, in

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this context we will present the work performed on high spatialresolutions observations of the Imhotep region. The Imhotepregion, located on the main lobe of the nucleus, presents asmooth surface with no obvious impacts or depressions. Thisregion was observed at least twice at high spatial resolution(approximately 18 m at submm wavelengths, 45 m in themillimeter), the first time on October 27th 2014 as a single swathobservation then again on July 9th 2016 as a raster scan. Using athermo-physical model developed at JPL to fit the observedthermal emission we will present the constraints we managed toobtain on the subsurface properties and their evolution over time.

Author(s): Anthony Lethuillier , Paul von Allmen , MarkHofstadter , Gerard Beaudin , Nicolas Biver , DominiqueBockelee-Morvan , Mathieu Choukroun , Jacques Crovisier ,Bjorn Davidsson , Pierre Encrenaz , Therese Encrenaz ,Margaret Frerking , Samuel Gulkis , Paul Hartogh , Wing-HuenIp , Michael A. Janssen , Christopher Jarchow , Seungwon Lee ,Emmanuel Lellouch , Cedric Leyrat , Ladislav Rezac , PeterSchloerb , Thomas R. SpilkerInstitution(s): 1. Jet Propulsion Laboratory/Calif. Inst. Tech.,2. LERMA-Observatoire de Paris, 3. LESIA-Observatoire deParis, 4. Max-Planck-Institut für Sonnensystemforschung, 5.National Central University, 6. Solar System Science andExploration, 7. University of MassachusettsContributing team(s): MIRO/Rosetta

415.04 – Three-dimensional views of the nucleus ofComet 67P/Churyumov-Gerasimenko: an atlas ofstereo anaglyphs from OSIRIS-NAC imagesThe Narrow Angle Camera (NAC) of the OSIRIS imaging systemaboard ESA’s Rosetta spacecraft has acquired approximately25000 images of the surface of the nucleus of comet67P/Churyumov-Gerasimenko at various spatial scales down tocentimeters per pixel. The bulk of these images have beenobtained in sequences and the combined displacement of theRosetta orbiter along its trajectory and the rotation of the nucleusallow associating many pairs of images appropriate tostereoscopic viewing. This is achieved by constructing anaglyphsafter rotating the images so that the relative shift appearshorizontal. The shift is set to limit the parallax to approximately2° (with a maximum value of 4°) for the foreground (to avoidimage deformation) and the scene is placed behind the screen foroptimal visual comfort. The rotation of the nucleus may have theadverse effect of introducing temporal incoherence, prominentlyfrom the variation of the cast shadows. Various solutions areimplemented to circumvent this problem, usually by cropping themaximum extent of the shadows. A time of writing,approximately 900 anaglyphs have been produced and we expectto reach several thousand once the systematic search of suitablepairs will be completed. We will present examples of anaglyphs.They will be searchable thanks to a dedicated data base that willdocument each one including its location on a 3D numericalmodel of the nucleus. Many possibilities of querying theparameters will be offered. It is anticipated that this atlasavailable online in the near future will be a valuable tool forfostering our understanding of the complex morphology of thecometary surface and of the processes at work , as well as offeringspectacular stereoscopic views of the nucleus enjoyable by ageneral public.

Author(s): Philippe L. Lamy , David Romeuf , GuillaumeFaury , Joelle Durand , Laurent Beigbeder , Olivier GroussinInstitution(s): 1. AKKA Informatique et Systèmes, 2. CentreNational d'Etudes Spatiales, 3. Gfi Informatique, 4. Lab.D'Astrophysique De Marseille, 5. Université Claude BernardLyon 1

415.05 – The 19 February 2016 Outburst of Comet67P/C-G: Heating of the Coma by Dust Raised in anAvalancheThe Microwave Instrument for the Rosetta Orbiter (MIRO) is aU.S. instrument with French, German, and Taiwaneseparticipation. It is on the European Space Agency's Rosetta

spacecraft which, from August 2014 through September 2016,was flying along side comet 67P/Churyumov-Gerasimenko.MIRO is designed to study the nucleus and coma of the comet asa coupled system. It makes broad-band continuum measurementsat 190 and 563 GHz (1.6 and 0.5 mm) of thermal emission fromthe nucleus and large dust particles in the coma. MIRO also has ahigh resolution (44 kHz) spectrometer fixed tuned tosubmillimeter lines of H O, H O, H O, CO, NH , and threeCH OH transitions, allowing us to determine the abundance,velocity, and temperature of these species in the coma. On 19 February 2016, most of the instruments on Rosettaobserved a strong outburst in activity (Grün et al. 2016, MNRAS).The first signs of this outburst were a large cloud of dust risingfrom the nucleus, and an increase in the excitation temperature ofgas in the coma from ~20 to ~50 K. A few minutes later there isevidence of an increase in gas density. We previously suggestedthat this sequence of events is best explained by a landslide orcollapse on the nucleus which first raises dust. The dust thenradiatively heats the entire coma, after which nucleus ices, newlyexposed by the landslide, begin sublimating and increasing comagas density. We will present our latest calculations on thefeasibility of small dust particles (which have high temperature)radiatively increasing the temperature of water molecules in thecoma, and will compare predicted with observed gastemperatures.

Author(s): Mark D. Hofstadter , Adeline Gicquel , Paul vonAllmen , Nicolas Biver , Seungwon Lee , Dominique Bockelee-Morvan , Peter Schloerb , Bjorn Davidsson , Sam Gulkis ,Gerard Beaudin , Mathieu Choukroun , Jacques Crovisier ,Pierre Encrenaz , Therese Encrenaz , Margaret Frerking , PaulHartogh , Wing-Huen Ip , Michael A. Janssen , ChristopherJarchow , Emmanuel Lellouch , Cedric Leyrat , Ladislav Rezac ,Thomas R. SpilkerInstitution(s): 1. Inst. Ast. Space Sci, 2. JPL/Caltech, 3.LERMA, Obs. Paris, 4. LESIA Obs. Paris, 5. Max Planck, 6. SolarSys. Sci. and Exploration, 7. Univ. Mass.

415.06 – Observations of Large Dust Particles inthe Coma of 67P/Churyumov-GerasimenkoThe Microwave Instrument for the Rosetta Orbiter (MIRO) is amillimeter-wave instrument with two continuum channels atwavelengths of 0.53 mm and 1.59 mm. The instrument has a30cm-diameter antenna which provides resolution of about 217mand 690m at the respective wavelengths for a spacecraft-cometdistance of 100km. During the months around the August 2015perihelion of comet 67P, a small emission excess was observedabove the sunlit limb of the nucleus. The excess emission extendsmany beam widths off the dayside limb and is attributed tothermal emission from large (mm-scale) dust particles. Mapsshow no detected emission on the night side of the nucleus,suggesting that production of these large dust particles isconfined to the sunlit portions of the nucleus. Typical antennatemperatures observed at a distance of 4km from the center of thenucleus are approximately 1K, which corresponds to a dustcolumn density of approximately 0.1 kg m . Dust emission wasdetected in both the MIRO channels with a typical relativebrightness of the 0.53 mm emission to the 1.59 mm emission of1.2. We find that this result is most consistent with particle sizedistributions which extend up to radii of at least severalcentimeters and/or flatter particle size distributions than thosetypically attributed to cometary dust. Maps show that theemission decreases with impact parameter of instrumentboresight with respect to the nucleus (b) according to a power lawwith b – b , with values changing from map to map. Thisresult is noteworthy because models of dust outflow from thesunlit side of a spherical nucleus, in which particles areaccelerated by the drag force of the outflowing gas, predictcolumn density falloff according to b . Thus, the radialdecrease in the actual maps is steeper than that predicted by thesimplest model suggesting, among other possibilities, thedestruction of the large particles in time scales of 20,000-80,000seconds. In this paper, we present new analysis and maps of the

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dust emission and describe our progress in modeling theobservations.

Author(s): F. Peter Schloerb , Samuel Gulkis , NicolasBiver , Paul von Allmen , Gerard Beaudin , DominiqueBockelee-Morvan , Mathieu Choukroun , Jacques Crovisier ,Bjorn Davidsson , Pierre Encrenaz , Therese Encrenaz ,Margaret Frerking , Adeline Gicquel , Paul Hartogh , Wing-Huen Ip , Michael A. Janssen , Christopher Jarchow , TheodoreKareta , Seungwon Lee , Emmanuel Lellouch , Cedric Leyrat ,Ladislav Rezac , Thomas R. SpilkerInstitution(s): 1. JPL, 2. LERMA - Obs. de Paris, 3. LESIA-Obs.de Paris, 4. Max-Planck-Institut fur Sonnensystemforschung, 5.National Central University, 6. University of Massachusetts atAmherstContributing team(s): MIRO Team

415.08 – Nucleus structure and dust morphology:Post-Rosetta understanding and implicationsThe structure of cometary nuclei and the morphology of dustparticles they eject have long been unknowns in cometary science.The combination of these two subjects, as revealed by the Rosettamission at 67P/C-G, is currently providing an unprecedentedinsight about Solar System formation and early evolution. Rosetta has established that the bulk porosity of 67P/C-G nucleusis high, in the 70% to 85% range, both from the determination ofits density and from permittivity measurements with CONSERTbistatic radar experiment [1-2]. CONSERT, through operationsafter Philae landing on 12-13 November 2014, has also allowed usto estimate that i) the porosity is likely to be higher inside thenucleus than on its subsurface, ii) a major component of thenucleus is refractory carbonaceous compounds, and iii) the smalllobe is homogeneous at a scale of a few wavelengths (i.e., about 10

m), while heterogeneities in the 3-m range (similar to therounded nodules noticed on walls of large pits) cannot be ruledout [2-4]. Rosetta has also established, through its 26 months rendezvouswith 67P/C-G, the aggregated structure of dust particles within awide range of sizes in the inner cometary coma. The MIDASatomic force microscope experiment has given us evidence (from3D topographic images with nano- to micrometer resolution) fori) a hierarchical structure of aggregated dust particles, down totens of nm-sized grains, ii) one extremely porous dust particle,with a fractal dimension of (1.7 ± 0.1) [5-6]. The accuracy ofcomparisons between cometary dust particles and interplanetarydust particles collected in the stratosphere (including CP-IDPs)could thus be improved. Such results should further refine the main processes (e.g., lowvelocity aggregation) that allowed the formation of comets in theearly Solar System, and the implications of a possible late heavybombardment on the interplanetary dust clouds and on telluricplanets. References. 1. Pätzold et al. Nature 530 63 2016. 2. Kofman et al.Science 349 6247 2015. 3. Herique et al. MNRAS 462 S516 2016.4. Ciarletti et al. A&A 583 A40 2015. 5. Bentley et al., Nature 53773 2016. 6. Mannel et al., MNRAS 462 S304 2016.

Author(s): A. Levasseur-Regourd , Mark Bentley , ValérieCiarletti , Woldek Kofman , Jeremie Lasue , Thurid Mannel ,Alain HeriqueInstitution(s): 1. Institut für Weltraumforschung (IWF), 2.IPAG, 3. IRAP, 4. OVSQ / LATMOS-CNRS, 5. UPMC (SorbonneUniv.) / LATMOS-CNRS

416.01 – HAT-P-16b: A Bayesian AtmosphericRetrievalHAT-P-16b is a hot (equilibrium temperature 1626 ± 40 K,assuming zero Bond albedo and efficient energy redistribution),4.19 ± 0.09 Jupiter-mass exoplanet orbiting an F8 star every2.775960 ± 0.000003 days (Buchhave et al 2010). We observedtwo secondary eclipses of HAT-P-16b using the 3.6 μm and 4.5μm channels of the Spitzer Space Telescope's Infrared ArrayCamera (program ID 60003). We applied our Photometry forOrbits, Eclipses, and Transits (POET) code to produce normalizedeclipse light curves, and our Bayesian Atmospheric RadiativeTransfer (BART) code to constrain the temperature-pressureprofiles and atmospheric molecular abundances of the planet.Spitzer is operated by the Jet Propulsion Laboratory, CaliforniaInstitute of Technology, under a contract with NASA. This workwas supported by NASA Planetary Atmospheres grantNNX12AI69G and NASA Astrophysics Data Analysis Programgrant NNX13AF38G.

Author(s): Kathleen McIntyre , Joseph Harrington ,Jasmina Blecic , Patricio Cubillos , Ryan Challener , GasparBakosInstitution(s): 1. Princeton, 2. University of Central Florida

416.02 – Dayside atmospheric structure ofHD209458b from Spitzer eclipsesHD209458b is a hot Jupiter with a radius of 1.26 ± 0.08 Jupiterradii (Richardson et al, 2006) and a mass of 0.64 ± 0.09 Jupitermasses (Snellen et al, 2010). The planet orbits a G0 type star withan orbital period of 3.52472 ± 2.81699e-05 days, and a relativelylow eccentricity of 0.0082 +0.0078/-0.0082 (Wang and Ford2013). We report the analysis of observations of HD209458bduring eclipse, taken in the 3.6 and 4.5 micron channels by theSpitzer Space Telescope's Infrared Array Camera (Program90186). We produce a photometric light curve of the eclipses inboth channels, using our Photometry for Orbits Eclipses andTransits (POET) code, and calculate the brightness temperaturesand eclipse depths. We also present best estimates of theatmospheric parameters of HD209458b using our Bayesian

Atmospheric Radiative Transfer (BART) code. These are somepreliminary results of what will be an analysis of all availableSpitzer data for HD209458b. Spitzer is operated by the JetPropulsion Laboratory, California Institute of Technology, undera contract with NASA. This work was supported by NASAPlanetary Atmospheres grant NX12AI69G and NASAAstrophysics Data Analysis Program grant NNX13AF38G.

Author(s): Matthew Reinhard , Joseph Harrington , RyanChallener , Patricio Cubillos , Jasmina BlecicInstitution(s): 1. New York University Abu Dhabi, 2. SpaceResearch Institute, Austrian Academy of Sciences, 3. Universityof Central Florida

416.03 – BARTTest: Community-StandardRadiative-Transfer Tests II: Retrieval ModelsAtmospheric radiative transfer codes are used both to predictplanetary spectra and in retrieval algorithms to interpret data.Observational plans, theoretical models, and scientific resultsthus depend on the correctness of these calculations. Yet, thecalculations are complex and the codes implementing them areoften written without modern software-verification techniques.The community needs a suite of test calculations with analytically,numerically, or at least communally verified results. We thereforeoffer the Bayesian Atmospheric Radiative Transfer Test Suite, orBARTTest, a collection of tests offered for community use anddevelopment. This presentation focuses on Bayesian retrieval. Tests includeadding noise to and retrieving the BARTTest forward modelsusing the photometric bandpasses and spectroscopic resolutionsof the Spitzer, Hubble, Webb, and larger space telescopes forseveral model exoplanets. A community-verified test on real datafor WASP-12b is also included. BARTTest is open-source software. We propose this test suite as astandard for verifying radiative-transfer codes, analogous to theHeld-Suarez test for general circulation models. This work wassupported by NASA Planetary Atmospheres grant NX12AI69Gand NASA Astrophysics Data Analysis Program grant

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Author(s): Joseph Harrington , Michael D. Himes , PatricioCubillos , Jasmina Blecic , Ryan C ChallenerInstitution(s): 1. Austrian Academy of Sciences, 2. New YorkUniversity, 3. University of Central Florida

416.04 – Pixel-Level Decorrelation and BiLinearlyInterpolated Subpixel Sensitivity applied to WASP-29bMeasured exoplanet transit and eclipse depths can varysignificantly depending on the methodology used, especially atthe low S/N levels in Spitzer eclipses. BiLinearly InterpolatedSubpixel Sensitivity (BLISS) models a physical, spatial effect,which is independent of any astrophysical effects. Pixel-LevelDecorrelation (PLD) uses the relative variations in pixels near thetarget to correct for flux variations due to telescope motion. PLDis being widely applied to all Spitzer data without a thoroughunderstanding of its behavior. It is a mathematical methodderived from a Taylor expansion, and many of its parameters donot have a physical basis. PLD also relies heavily on binning thedata to remove short time-scale variations, which can artificallysmooth the data. We applied both methods to 4 eclipseobservations of WASP-29b, a Saturn-sized planet, which wasobserved twice with the 3.6 µm and twice with the 4.5 µmchannels of Spitzer's IRAC in 2010, 2011 and 2014 (programs60003, 70084, and 10054, respectively). We compare theresulting eclipse depths and midpoints from each model, assesseach method's ability to remove correlated noise, and discuss howto choose or combine the best data analysis methods. We alsorefined the orbit from eclipse timings, detecting a significantnonzero eccentricity, and we used our Bayesian AtmosphericRadiative Transfer (BART) code to retrieve the planet'satmosphere, which is consistent with a blackbody. Spitzer isoperated by the Jet Propulsion Laboratory, California Institute ofTechnology, under a contract with NASA. This work wassupported by NASA Planetary Atmospheres grant NNX12AI69Gand NASA Astrophysics Data Analysis Program grantNNX13AF38G.

Author(s): Ryan Challener , Joseph Harrington , PatricioCubillos , Jasmina Blecic , Drake DemingInstitution(s): 1. University of Central Florida, 2. University ofMaryland

416.06 – Independent Component Analysis appliedto Ground-based observationsTransit measurements of Jovian-sized exoplanetary atmospheresallow one to study the composition of exoplanets, largelyindependent of the planet’s temperature profile. However,measurements of hot-Jupiter transits must archive a level ofaccuracy in the flux to determine the spectral modulations of theexoplanetary atmosphere. To accomplish this level of precision,we need to extract systematic errors, and, for ground-basedmeasurements, the effects of Earth’s atmosphere, from signal dueto the exoplanet, which is several orders of magnitudes smaller.

The effects of the terrestrial atmosphere and some of the timedependent systematic errors of ground-based transitmeasurements are treated mainly by dividing the host star by areference star at each wavelength and time step of the transit.Recently, Independent Component Analyses (ICA) have beenused to remove systematics effects from the raw data of space-based observations (Waldmann, 2014, 2012; Morello et al., 2016,2015). ICA is a statistical method born from the ideas of theblind-source separations studies, which can be used to de-trendseveral independent source signals of a data set (Hyvarinen andOja, 2000). This technique requires no additional priorknowledge of the data set. In addition this technique has theadvantage of requiring no reference star.

Here we apply the ICA to ground-based photometry of theexoplanet XO-2b recorded by the 61” Kuiper Telescope and

compare the results of the ICA to those of a previous analysisfrom Zellem et al. (2015), which does not use ICA. We alsosimulate the effects of various conditions (concerning thesystematic errors, noise and the stability of object on the detector)to determine the conditions under which an ICA can be used withhigh precision to extract the light curve of exoplanetaryphotometry measurements.

Author(s): Walter Martins-Filho , Caitlin Ann Griffith ,Kyle Pearson , Ingo Waldmann , Alvaro Alvarez-Candal , RobertZellemInstitution(s): 1. Jet Propulsion Laboratory, 2. Lunar andPlanetary Laboratory/UA, 3. Observatório Nacional, 4.University College London

416.09 – Mapping the Pressure–radiusRelationship of ExoplanetsThe radius of a planet is one of the most physically meaningfuland readily accessible parameters of extra-solar planets. Thisparameter is extensively used in the literature to compare planetsor study trends in the know population of exoplanets. However, inan atmosphere, the concept of a planet radius is inherently fuzzy.The atmospheric pressures probed by trasmission (transit) oremission (eclipse) spectra are not directly constrained by theobservations, they vary as a function of the atmosphericproperties and observing wavelengths, and further correlate withthe atmospheric properties producing degenerate solutions. Here, we characterize the properties of exoplanet radii using aradiative-transfer model to compute clear- atmospheretransmission and emission spectra of gas-dominated planets. Weexplore a wide range of planetary temperatures, masses, andradii, sampling from 300 to 3000 K and Jupiter- to Earth-likevalues. We will discuss how transit and photospheric radii varyover the parameter space, and map the global trends in theatmospheric pressures associated with these radii. We will alsohighlight the biases introduced by the choice of an observingband, or the assumption of a clear/cloudy atmosphere, and therelevance that these biases take as better instrumentationimproves the precision of photometric observations.

Author(s): Patricio Cubillos , Luca Fossati , DaryaKubyshkinaInstitution(s): 1. Space Research Institute

416.10 – Atmospheric and Climate Effects onPlanets Orbiting Fast-Rotating StarsFast rotation in stars can induce pole-to-equator temperaturegradients of up to several thousand Kelvin that affect both thestar’s luminosity and peak wavelength as a function of stellarlatitude. When orbiting a fast-rotating star, a planet’s averageannual insolation can strongly vary depending on its orbitgeometry. For example, an inclined orbit results in more directexposure to the host star’s hotter poles, potentially causing muchstronger temperature variations between seasons. This gradient,known as gravity-darkening, can also affect chemical processes ina planet’s atmosphere as it is exposed to solar irradiancecorresponding to different stellar effective temperatures overtime. My model accounts for gravity-darkening and models theinstantaneous insolation that a planet receives from a fast-rotatorfor any orbit geometry. These results are an important steptoward modeling climates and seasonal variations of planetsorbiting fast-rotating stars, and also lay the groundwork forperforming transmission spectroscopy in gravitydarkenedsystems.

Author(s): Johnathon AhlersInstitution(s): 1. University of Idaho

416.11 – Follow-Up Photometry of Kelt TransitingPlanet CandidatesWe have three telescopes at BYU that we use to follow-up possibletransiting planet canidates for the KELT team. These telescopeswere used to collect data on Kelt-16b and Kelt-9b, which is thehottest known exoplanet. More recently we used the newest of

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these telescopes, a robotic 8-inch telescope on the roof of ourbuilding, to confirm the most recent Kelt planet that will bepublished soon. This research has been ideal for the teaching andtraining of undergraduate students in the art of photometricobserving and data reduction. In this presentation I will highlighthow we are using our membership in the Kelt team to further theeducational objective of our undergraduate astronomy program,while contributing meaningful science to the ever growing field ofexoplanet discovery. I will also highlight a few of the moreinteresting Kelt planets and the minimum telescope requirementsfor detecting these planets. I will then discuss the sensitivitiesrequired to follow-up future TESS candidates, which may be ofinterest to others interested in joining the TESS follow-up teams.

Author(s): Denise C. Stephens , Michael D. Joner , Eric G.Hintz , Trevor Martin , Alex SpencerInstitution(s): 1. Brigham Young Univ.Contributing team(s): Kelt Follow-Up Network (FUN) Team

416.12 – The KOI 425 Multi-star SystemKepler Object of Interest 425 (KOI 425) is an eclipsing binarywith periodic features in addition to the known primary andsecondary transits. This KOI has been observed by Saterne et al.2012 with SOPHIE, who found its phase variance to be indicativeof a diluted eclipsing binary, likely produced by a multi-starsystem. We analyze the complete set of Kepler archival data forthis system along with the published SOPHIE results to assess themultiplicity and the dynamics of the system.

Author(s): Anna Hughes , Aaron C. BoleyInstitution(s): 1. The University of British Columbia

416.13 – Searching for Planetary Moons in theSpectra of Rotating StarsExoplanets that happen to transit their stars will produce a dropin integrated light

△F ~ (R /R )

as well as a measurable Doppler shift of monochromatic light

v ≤ 2πR /R P

from asymmetric masking of different regions of a rotating star(with period P and maximum limb-velocity v). The Dopplersignal is the familiar Rossiter-McLaughlin (RM) effect, andreveals the system geometry in addition to planet size. Here weexamine changes to the RM signal resulting from exoplanetarysatellites. We show that sizeable moons, exceeding the mass ofMars, are detectable in both integrated and monochromatic light,assuming a Doppler precision ≤ 1m/sec is possible with futureinstruments.

Author(s): Darren WilliamsInstitution(s): 1. Penn State Behrend

416.14 – Optimizing the TESS Planet FindingPipelineThe Transiting Exoplanet Survey Satellite (TESS) is a new NASAplanet finding all-sky survey that will observe stars within 200light years and 10-100 times brighter than that of the highlysuccessful Kepler mission. TESS is expected to detect ~1000planets smaller than Neptune and dozens of Earth size planets. Asin the Kepler mission, the Science Processing Operations Center(SPOC) processing pipeline at NASA Ames Research center istasked with calibrating the raw pixel data, generating systematicerror corrected light curves and then detecting and validatingtransit signals. The Transiting Planet Search (TPS) component ofthe pipeline must be modified and tuned for the new datacharacteristics in TESS. For example, due to each sector beingviewed for as little as 28 days, the pipeline will be identifyingtransiting planets based on a minimum of two transit signalsrather than three, as in the Kepler mission. This may result in asignificantly higher false positive rate. The study presented here is

to measure the detection efficiency of the TESS pipeline usingsimulated data. Transiting planets identified by TPS arecompared to transiting planets from the simulated transit modelusing the measured epochs, periods, transit durations and theexpected detection statistic of injected transit signals (expectedMES). From the comparisons, the recovery and false positiverates of TPS is measured. Measurements of recovery in TPS arethen used to adjust TPS configuration parameters to maximizethe planet recovery rate and minimize false detections. Theimprovements in recovery rate between initial TPS conditionsand after various adjustments will be presented and discussed.

Author(s): Aerbwong Chitamitara , Jeffrey C. Smith , PeterTenenbaumInstitution(s): 1. California State Polytechnic University,Pomona, 2. SETI InstituteContributing team(s): TESS Science Processing OperationsCenter

416.16 – Eighteenth-Century Observations of Algol:The First Suggestion of an Exoplanet?In November of 1782, 18-year old John Goodricke of York,England, was amazed to observe the star Algol (Beta Persei) dimby more than one magnitude and then return to full brightnessover a period of seven hours. Goodricke and his mentor, EdwardPigott, speculated that the dimming could only have been causedby a "dark body" passing in front of Algol. Over the succeedingmonths, the two were able to refine the period between what wenow know to be eclipses to 2.87 days. They would determine theperiods of other variable stars, including the first two Cepheidvariables known. Yet in their lifetime, their suggestion that Algol'svariation was due to an eclipse was not accepted. Mostastronomers believed the variations were due to spots on thesurface of a single star. Only a century later, with the advent ofastronomical spectroscopy, was Algol's true nature revealed.Goodricke and Pigott's work is one of the first studies of stellarvariation; their methods and occasional pitfalls are ones to whichmodern astronomers can relate.

Author(s): Linda M. FrenchInstitution(s): 1. Illinois Wesleyan Univ.

416.17 – Triboelectrification of KCl and ZnSparticles with applications to GJ1214bWhen mobilized, granular materials become charged asindividual grains undergo collisions and frictional interactions.On Earth, this process, known as triboelectrification, has beenrecognized in volcanic plumes and sandstorms (Kok & Lacks2009 )(Cimarelli et al. 2014 ) (Méndez Harper & Dufek 2016 ).Yet, frictional charging almost certainly exists on other worlds inour own Solar System (such as Mars, the Moon, and Venus) aswell as extra solar planets. Indeed, recent observations andnumerical modeling have suggested that many exoplanets mayhave processes that lift large quantities of particles into theiratmospheres (volcanic activity, for instance) (Hodosán et al. 2016) or maintain extensive condensed granular reservoirs in the formof clouds or hazes (Helling et al. 2013 )(Kreidberg et al. 2014 )(Gao & Benneke 2016 ). On these worlds, triboelectric chargingalmost certainly contributes to their global electric circuits,providing a mechanism to generate lightning, to drive chemicalprocesses in the atmospheres, and, perhaps, influencehabitability. Yet, despite the high likelihood of granularelectrification processes occurring on worlds beyond our SolarSystem, no experiments, to our knowledge, have been conductedto characterize the triboelectrification of materials expected toexist in the exoplanet atmospheres under appropriate conditions.To help close this knowledge-gap, we explore the electrification ofpotassium chloride and zinc sulfide, two substances possiblycomposing the clouds on super-Earth GJ1214b (Kreidberg et al.2014 ) (Charnay et al. 2015 ) (Gao & Benneke 2016 ). We find thatboth materials become readily electrified when mobilized,attaining charge densities similar to those found on volcanic ashparticles. Thus, if GJ1214b does indeed host salt clouds in its

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atmosphere, they are likely electrified and may be capable ofproducing lightning or corona discharge.

Author(s): Joshua Mendez , Josef DufekInstitution(s): 1. Georgia Institute of Technology

416.18 – Looking for signs of an ocean in theTRAPPIST-1 system

Since the discovery of seven temperate, earth-like planets orbitingan M dwarf earlier this year, the TRAPPIST-1 system has been ofgreat interest from a habitability perspective. Here we model thereflected light signatures from various TRAPPIST-1 planets toanswer the question: Can we see glint from an ocean on thesurface of any of these planets? Even if a liquid ocean occupied alarge fraction of the surface, there is still possibility that it mightbe obscured by a thick atmosphere with clouds or hazes. Weperform multiple scattering radiative transfer calculations usingthe model VLIDORT to produce polarized light curves for avariety of scenarios. The goal is the perform a parameter searchfor several variables including atmospheric thickness, refractiveindex of the liquid and albedo of the planet. We discuss thepossibility for detection of a liquid surface with current and nearfuture observational capabilities.

Author(s): Pushkar Kopparla , Vijay Natraj , David Crisp ,Kim Bott , Yuk YungInstitution(s): 1. California Institute of Technology, 2. JetPropulsion Lab, 3. University of Washington

416.19 – Effect of Pressure Broadening onEmission and Transmission Spectra of H OModeled for sub-Neptune/super-Earth exoplanets:An Application to JWSTWater is the most readily detected molecule over a diverse rangeof exoplanet properties (solar composition hot-Jupiters to highmetallicity super-earths/neptunes). It is also one of the mostimportant sources of opacity that govern radiative energybalance. It is well known that pressure/collisional broadeningsignificantly influences the opacity of a given molecule.Laboratory spectroscopic studies have shown that the line-broadening (i.e. Doppler, Lorentzian) is influence by severalfactors including temperature, pressure, dipole moment of thebroadeners (or bath gases), and the rotational quantum numbers.Since absorption cross-sections (or opacities) are central to bothatmospheric modeling and observational research, there is acritical need to investigate the effect of pressure line-broadeningon the absorption cross-sections and subsequent influence onobserved transmission and emission spectra of transitingexoplanets. Typical data-model comparisons (either forwardmodeling or retrieval's) generally rely upon pre-computed grids ofabsorption cross-sections that assume trace molecules arebroadened by a solar composition mixture (e.g., mainly H andHe as a bath gas). However, as the metallicity of a planetaryatmosphere increases, as anticipated for smaller planets in thesub-Neptune-Super Earth range, broadening due to other gases(e.g., N , CO , H O, CH , CO) can become significant and theH -He broadening is no longer appropriate. In this work, weassess the influence of different background broadeners on theabsorption cross-section of water, and subsequent influence onobserved transmission/emission spectra. Initial results suggestthat the choice of foreign broadener can result in up to a factor of~5 increase in pressure broadened wings of the absorption crosssections, resulting in a factor of 1.6x reduction in the atmosphericspectral modulation. Such a difference will be detectible in the hi-resolution/SNR spectra anticipated with JWST, and will certainlyinfluence the interpretation of high-metallicity atmospheres.

Author(s): Ehsan Gharib Nezhad , Michael R. Line , JamesR. LyonsInstitution(s): 1. School of Earth and Space Exploration,Arizona State University, 2. School of Molecular Sciences,Arizona State University

416.20 – The Effect of Stellar Contamination onTransmission Spectra of Low-mass ExoplanetsTransmission spectroscopy offers the exciting possibility ofstudying terrestrial exoplanet atmospheres in the near-termfuture. The Transiting Exoplanet Survey Satellite (TESS),scheduled for launch next year, is expected to discover thousandsof transiting exoplanets around bright host stars, including anestimated twenty habitable zone super-Earths. The brightness ofthe TESS host stars, combined with refined observationalstrategies and near-future facilities, will enable searches foratmospheric signatures from smaller and cooler exoplanets. These observations, however, will be increasingly subject to noiseintroduced by heterogeneities in the host star photospheres, suchas star spots and faculae. In short, the transmission spectroscopymethod relies on the assumption that the spectrum of the transitchord does not differ from that of the integrated stellar disk or, ifit does, the contribution of photospheric heterogeneities to thetransmission spectrum can be constrained by variabilitymonitoring. However, any axisymmetric populations of spots andfaculae will strongly affect transmission spectra, and theirpresence cannot be deduced from monitoring efforts. A clear needexists for a more robust understanding of stellar contaminationon transmission spectra. Here we summarize our work on the impact of heterogeneousstellar photospheres on transmission spectra and detailimplications for atmospheric characterization efforts. Bymodeling spot and faculae distributions in stellar photospheres,we find that spot-covering fractions extrapolated from observedvariability amplitudes are significantly underestimated. Likewise,corrections based on variability monitoring likely fall short of theactual stellar spectral contamination. We provide examples ofcontamination spectra for typical levels of stellar activity across arange of spectral types. For M dwarfs, molecular absorptionfeatures in spots and faculae can imprint apparent features intransmission spectra of small exoplanets, including those of theTRAPPIST-1 system. Constraining stellar contamination willlikely be a limiting factor for detecting atmospheric features intransmission spectra of low-mass exoplanets around late-typestars from TESS.

Author(s): Benjamin V Rackham , Daniel Apai , Mark S.GiampapaInstitution(s): 1. National Solar Observatory, 2. University ofArizona

416.21 – Dynamics of Massive AtmospheresThe many recently discovered terrestrial exoplanets are expectedto hold a wide range of atmospheric masses. Here the dynamic-thermodynamic effects of atmospheric mass on atmosphericcirculation are studied using an idealized global circulation modelby systematically varying the atmospheric surface pressure. On anEarth analog planet, an increase in atmospheric mass weakensthe Hadley circulation and decreases its latitudinal extent. Thesechanges are found to be related to the reduction of the convectivefluxes and net radiative cooling (due to the higher atmosphericheat capacity), which, respectively, cool the upper troposphere atmid-low latitudes and warm the troposphere at high latitudes.These together decrease the meridional temperature gradient,tropopause height and static stability. The reduction of theseparameters, which play a key role in affecting the flow propertiesof the tropical circulation, weakens and contracts the Hadleycirculation. The reduction of the meridional temperature gradientalso decreases the extraction of mean potential energy to the eddyfields and the mean kinetic energy, which weakens theextratropical circulation. The decrease of the eddy kinetic energydecreases the Rhines wavelength, which is found to follow themeridional jet scale. The contraction of the jet scale in theextratropics results in multiple jets and meridional circulationcells as the atmospheric mass increases.

Author(s): Rei Chemke , Yohai KaspiInstitution(s): 1. Weizmann Institute of Science

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416.22 – Uniform Atmospheric Retrievals ofUltracool Late-T and Early-Y dwarfsA significant number of ultracool (<600K) extrasolar objects havebeen discovered in the past decade thanks to wide-field surveyssuch as WISE. These objects present a perfect testbed forexamining the evolution of atmospheric structure as we transitionfrom typically hot extrasolar temperatures to the temperaturesfound within our Solar System. By examining these types of objects with a uniform retrievalmethod, we hope to elucidate any trends and (dis)similaritiesfound in atmospheric parameters, such as chemical abundances,temperature-pressure profile, and cloud structure, for a sample of7 ultracool brown dwarfs as we transition from hotter (~700K) tocolder objects (~450K). We perform atmospheric retrievals on two late-T and five early-Ydwarfs. We use the NEMESIS atmospheric retrieval code coupledto a Nested Sampling algorithm, along with a standard uniformmodel for all of our retrievals. The uniform model assumes theatmosphere is described by a gray radiative-convectivetemperature profile, (optionally) a gray cloud, and a number ofrelevant gases. We first verify our methods by comparing it to abenchmark retrieval for Gliese 570D, which is found to beconsistent. Furthermore, we present the retrieved gaseouscomposition, temperature structure, spectroscopic mass andradius, cloud structure and the trends associated with decreasingtemperature found in this small sample of objects.

Author(s): Ryan Garland , Patrick IrwinInstitution(s): 1. University of Oxford

416.23 – Tidal evolution and possible formation ofProxima b within the horizontal zonesProxima b is a planet within the habitable zone (HZ) aroundProxima Centauri, the Sun’s closest neighbor, which makes thisplanetary system charming to study. The orbits such aseccentricity and inclination, the interiors, mass limit andformation and so on have been investigated. We know that thisearth-like planet is very close to its host star, so it is inevitablyaffected by the stellar tides. Here, we focus on the dynamicalevolution based on the equilibrium tidal model. Results show thatthe orbital circularization during tidal decay is within 20 Myrswhen assumed the modified tidal dissipation parameter Q’=6,and the planetary orbit-spin rotation reaches synchronous in tenthousand years. Various orbital parameters are considered instudying the orbit-spin rotations. We will also discuss the possibletimescale when Proxima b has to be out of HZ due to the verylong-time stellar tidal evolution. If Proxima b has retained anonzero eccentricity (for example, <0.35 indicated by theobservations), we explore the case that another planet companioncan excite a steady eccentricity before tidal evolution dependingon the eccentricity of the companion. Finally, the planetformation via type I migration in the gaseous disk is investigated,as the result that Proxima b can reach the inner disk with a periodof 14 days, then experience the tidal evolution reaching theobserved place.

Author(s): Yao DongInstitution(s): 1. Purple Mountain Observatory, ChineseAcademy of Sciences

416.24 – LASR-Guided Variability Subtraction: TheLinear Algorithm for Significance Reduction ofStellar Seismic ActivityStellar seismic activity produces variations in brightness thatintroduce oscillations into transit light curves, which can createchallenges for traditional fitting models. These oscillationsdisrupt baseline stellar flux values and potentially mask transits.We develop a model that removes these oscillations from transitlight curves by minimizing the significance of each oscillation infrequency space. By removing stellar variability, we prepare eachlight curve for traditional fitting techniques. We apply our modelto $\delta$-Scuti KOI-976 and demonstrate that our variabilitysubtraction routine successfully allows for measuring bulk systemcharacteristics using traditional light curve fitting. These results

open a new window for characterizing bulk system parameters ofplanets orbiting seismically active stars.

Author(s): Sarah Horvath , Sam Myers , Johnathon Ahlers ,Jason W. BarnesInstitution(s): 1. University of Idaho

416.25 – Laboratory Studies of Planetary Hazes:composition of cool exoplanet atmospheric aerosolswith very high resolution mass spectrometryWe present first results of the composition oflaboratory-produced exoplanet haze analogues. Withthe Planetary HAZE Research (PHAZER) Laboratory, wesimulated nine exoplanet atmospheres of varying initialgas phase compositions representing increasingmetallicities (100x, 1000x, and 10000x solar) andexposed them to three different temperature regimes(600, 400, and 300 K) with two different “instellation”sources (a plasma source and a UV lamp). The PHAZERexoplanet experiments simulate a temperature andatmospheric composition phase space relevant to theexpected planetary yield of the Transiting ExoplanetSurvey Satellite (TESS) mission as well as recentlydiscovered potentially habitable zone exoplanets in theTRAPPIST-1, LHS-1140, and Proxima Centauri systems.Upon exposure to the energy sources, all of theseexperiments produced aerosol particles, which werecollected in a dry nitrogen glove box and then analyzedwith an LTQ Orbitrap XL™ Hybrid Ion Trap-OrbitrapMass Spectrometer utilizing m/z ranging from 50 to1000. The collected aerosol samples were found tocontain complex organics. Constraining the compositionof these aerosols allows us to better understand thephotochemical and dynamical processes ongoing inexoplanet atmospheres. Moreover, these data caninform our telescope observations of exoplanets, whichis of critical importance as we enter a new era ofexoplanet atmosphere observation science with theupcoming launch of the James Webb Space Telescope.The molecular makeup of these haze particles provideskey information for understanding exoplanetatmospheric spectra, and constraining the structure andbehavior of clouds, hazes, and other aerosols is at theforefront of exoplanet atmosphere science.

Author(s): Sarah E Moran , Sarah Horst , Chao He , LaureneFlandinet , Julianne I. Moses , Francois-Regis Orthous-Daunay , Veronique Vuitton , Cedric Wolters , Nikole LewisInstitution(s): 1. Johns Hopkins University, 2. Space ScienceInstitute, 3. Space Telescope Science Institute, 4. UniversiteGrenoble Alpes, CNRS, IPAG

416.26 – New progress on the CH and CHspectroscopy in the near infrared regionWe present recent progress on the measurement and modeling ofCH spectroscopy in the NIR region from three separate works insupport of the atmospheric remote sensing of CH for Jovian andexoplanets. [1] We have studied the H -broadened CH (v +vn =4545.70 cm ) in the Octad near 2.3 µm. A series of spectra

of CH pure and in mixtures with H were obtained at severaltemperatures (100-370 K); these spectra were analyzed using amultispectrum non-linear least squares fitting algorithm adoptinga non-Voigt line shape model with full line mixing taken intoaccount. We present the results for H -pressure broadenedwidths and shifts along with their temperature dependences forthe first time as well as their full line mixing coefficients. We willalso discuss the A/E/F rotational symmetry species dependenceof the line shape parameters. [2] A new study of CH4spectroscopy was performed for the lower part of the Tetradecadregion (5300-5550 cm ) by analyzing multiple FT-IR spectra ofpure CH4 sample recorded at room temperatures at Reims(France) and at 80 K at JPL (USA). Line positions and intensitiesretrieved from the laboratory spectra were analyzed by theeffective Hamiltonian and the effective Dipole moment in terms

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of irreducible tensor operators adapted to spherical topmolecules. Out of the new 5934 measured transitions, quantumassignments were made for 2847 transitions, which represent~90% of the integrated line intensity in the observed spectra. Allthe CH assigned line positions and 2227 selected lineintensities were fitted to an RMS standard deviations of 0.0025cm and 8.6%, respectively. The sum of observed intensitiesbetween 5300 and 5550 cm fell within 2% of the predicted valuefrom the ab initio variational calculations. [3] Similarly, for

CH in the 4970-5470 cm region, in total 1387 rovibrationaltransitions were assigned, pertaining to five cold bands of theTetradecad up to Jmax=11. Their positions were fitted to an RMSdeviation of 0.0016 cm . Measured line intensities for 737

transitions were modeled with an RMS deviation of about 10%using the effective dipole transition moments approach.

Author(s): Keeyoon Sung , Andrei V. Nikitin , EvgeniyaStarikova , Malathy Devi , D. Chris Benner , Brian J Drouin ,Timothy J Crawford , Mary-Ann H. Smith , Arlan Mantz ,Ludovic Daumont , Michael Rey , Vladimir G. TyuterevInstitution(s): 1. Connecticut College, 2. Jet PropulsionLaboratory/Caltech, 3. NASA Langley Research Center, 4.Russian Academy of Sciences, 5. The College of William andMary, 6. Tomsk State University, 7. Université de Reims

417.01 – The Venus Emissivity Mapper – gaining aglobal perspective on the surface composition ofVenusThe permanent cloud cover of Venus prohibits observations of thesurface with traditional imaging techniques over much of the EMspectral range, leading to the false notion that information aboutthe composition of Venus’ surface could only be derived fromlander missions. However, harsh environmental conditions onthe surface cause landed missions to be sole site, highly complex,and riskier than orbiting missions. It is now known that 5 transparency windows occur in the Venusatmosphere, ranging from 0.86 µm to 1.18 µm. Recent advancesin high temperature laboratory spectroscopy at the PSL at DLRthese windows are highly diagnostic for surface mineralogy.Mapping of the southern hemisphere of Venus with VIRTIS onVEX in the 1.02 µm band was a proof-of-concept for an orbitalremote sensing approach to surface composition and weatheringstudies[1-3]. The Venus Emissivity Mapper [4] proposed for the NASA’s VenusOrigins Explorer (VOX) and the ESA EnVision proposal builds onthese recent advances. It is the first flight instrument speciallydesigned with a sole focus on mapping the surface of Venus usingthe narrow atmospheric windows around 1 µm. Operating in situfrom Venus orbit, VEM will provide a global map of surfacecomposition as well as redox state of the surface, providing acomprehensive picture of surface-atmosphere interaction andsupport for landing site selection. Continuous observation of thethermal emission of the Venus will provide tight constraints onthe current day volcanic activity[5]. This is complemented bymeasurements of atmospheric water vapor abundance as well ascloud microphysics and dynamics. These data will allow foraccurate correction of atmospheric interference on the surfacemeasurements, which provide highly valuable science on theirown. A mission combining VEM with a high-resolution radarmapper such as VOX or EnVision in a low circular orbit willprovide key insights into the divergent evolution of Venus. 1. Smrekar, S.E., et al., Science, 2010. 328(5978): p. 605-8. 2. Helbert, J., et al., GRL, 2008. 35(11). 3. Mueller, N., et al., JGR, 2008. 113. 4. Helbert, J., et al. 2016. San Diego, CA: SPIE. 5. Mueller, N.T., et al., JGR, 2017.

Author(s): Joern Helbert , Melinda Dyar , ThomasWidemann , Emmanuel Marcq , Alessandro Maturilli , NilsMueller , David Kappel , Sabrina Ferrari , Mario D'Amore ,Constantine Tsang , Gabriele Arnold , Suzanne SmrekarInstitution(s): 1. DLR, 2. JPL, 3. LATMOS, 4. Mount Holoyoke,5. Observatoire de Paris, 6. SwRI, 7. Univ. degli Studi di PaviaContributing team(s): VEM team

417.02 – The Venus Emissivity Mapper –Investigating the Atmospheric Structure andDynamics of Venus’ Polar RegionVenus displays the best-known case of polar vortices evolving in afast-rotating atmosphere. Polar vortices are pervasive in the SolarSystem and may also be present in atmosphere-bearingexoplanets. While much progress has been made since the earlysuggestion that the Venus clouds are H O-H SO liquid droplets(Young 1973), several cloud parameters are still poorly

constrained, particularly in the lower cloud layer and opticallythicker polar regions. The average particle size is constant overmost of the planet but increases toward the poles. This indicatesthat cloud formation processes are different at latitudes greaterthan 60°, possibly as a result of the different dynamical regimesthat exist in the polar vortices (Carlson et al. 1993, Wilson et al.2008, Barstow et al. 2012). Few wind measurements exist in the polar region due tounfavorable viewing geometry of currently available observations.Cloud-tracking data indicate circumpolar circulation close tosolid-body rotation. E-W winds decrease to zero velocity close tothe pole. N-S circulation is marginal, with extremely variablemorphology and complex vorticity patterns (Sanchez-Lavega etal. 2008, Luz et al. 2011, Garate-Lopez et al. 2013). The Venus Emissivity Mapper (VEM; Helbert et al., 2016)proposed for NASA’s Venus Origins Explorer (VOX) and the ESAM5/EnVision orbiters has the capability to better constrain themicrophysics (vertical, horizontal, time dependence of particlesize distribution, or/and composition) of the lower cloud particlesin three spectral bands at 1.195, 1.310 and 1.510 μm at a spatialresolution of ~10 km. Circular polar orbit geometry wouldprovide an unprecedented simultaneous study of both polarregions within the same mission. In addition, VEM’s pushbroommethod will allow short timescale cloud dynamics to be assessed,as well as local wind speeds, using repeated imagery at 90 minuteintervals. Tracking lower cloud motions as proxies for windmeasurements at high spatial resolutions will greatly benefitmodeling of the vortice’s physics, as well as wave-generatingdynamical instabilities (Garate-Lopez et al. 2015).

Author(s): Thomas Widemann , Emmanuel Marcq ,Constantine Tsang , Nils Mueller , David Kappel , JoernHelbert , Melinda Dyar , Suzanne SmrekarInstitution(s): 1. German Aerospace Center (DLR), 2.LATMOS, 3. Mount Holyoke College, 4. NASA / Jet PropulsionLaboratory, 5. Paris Observatory, 6. SwRI

417.03 – In Situ Missions For Investigation of theClimate, Geology and Evolution of VenusIn situ Exploration of Venus has been recommended by theDecadal Study of the National Research Council. Many highpriority measurements, addressing outstanding first-order,fundamental questions about current processes and evolution ofVenus can only be made from in situ platforms such as entryprobes, balloons or landers. These include: measuring noble gasesand their isotopes to constrain origin and evolution; measuringstable isotopes to constrain the history of water and othervolatiles; measuring trace gas profiles and sulfur compounds forchemical cycles and surface-atmosphere interactions,constraining the coupling of radiation, dynamics and chemistry,making visible and infrared descent images, and measuringsurface and sub-surface composition. Such measurements willallow us deepen our understanding of the origin and evolution ofVenus in the context of the terrestrial planets and extrasolarplanets, to determine the level and style of current geologicalactivity and to characterize the divergent climate evolution ofVenus and Earth and extend our knowledge of the limits ofhabitability on hot terrestrial planets.

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Author(s): David GrinspoonInstitution(s): 1. Planetary Science Institute

417.04 – Laboratory Measurements of SulfuricAcid Vapor Opacity at Millimeter WavelengthsUnder Venus ConditionsRadio astronomical observations of the lower-cloud and sub-cloud regions of the Venusian atmosphere at millimeterwavelengths can provide insight into the nature of the sub-cloudsulfur chemistry. Previous observations (de Pater et al., Icarus90, 1991 and Sagawa, J. Natl. Inst. of Inf. And Comm. Tech. 55,2008) indicate substantial variations in Venus disc brightness atmillimeter wavelengths, likely due to variations in SO andH SO vapor abundances. Although previous measurements ofH SO vapor opacity provide accurate information at centimeterwavelengths (Kolodner and Steffes, Icarus 132, 1998),extrapolation to millimeter wavelength observations isspeculative. A Fabry-Perot open resonator with a quality factor inexcess of 15,000 has been designed to measure the opacity ofH SO vapor in a CO atmosphere under Venus temperature andpressure conditions below the clouds. The resonator system hasbeen designed using corrosion-resistant materials to ensure dataintegrity. Opacity measurements made with this system target the2-4 millimeter wavelength range, applicable to recent AtacamaLarge Millimeter Array observations of Venus. Initial laboratoryresults for H SO vapor opacity will be presented, and theimplications of these results for pressure broadened opacityformalisms will be discussed. In addition to radio astronomicalobservations, these results of these measurements can aid in theinterpretation of radiometer and radio occultation measurementsfrom future Venus missions, such as the Venera D orbiter. Thiswork is supported by the NASA Solar System Workings Programunder grant NNX17AB19G.

Author(s): Alexander Brooks Akins , Paul G SteffesInstitution(s): 1. Georgia Institute of Technology

417.05 – Using a Venus Atmosphere Model toInvestigate Variations in Cloud-level Winds andTemperaturesWe have developed a new Venus Middle atmosphere Model(VMM), which simulates the atmosphere from just below thecloud deck to around 100 km altitude, with the aim of focusing onthe dynamics at cloud levels and above. We take this approach asthe circulation and dynamics between the ground and cloudaltitudes are not well known. Wind velocities below ~40 kmaltitude cannot be observed remotely and there are only a few in-situ wind profiles from entry probes on the Venera and PioneerVenus missions, which are limited in spatial and temporalcoverage. However, in the atmosphere at cloud altitudessignificant information can be obtained on the circulation anddynamics of Venus' atmosphere and many more observations areavailable, including measurements from Venus Express andAkatsuki. Preliminary results from the VMM with a simplifiedradiation scheme have been validated by comparison withPioneer Venus and Venus Express measurements and showreasonable agreement with the observations. Values ofparameters near the lower boundary which are not well measuredcan be inferred by comparison with values at higher altitudes. Weuse sensitivity experiments to determine the most importantprocesses involved in shaping the wind and temperature structureat cloud altitudes. We compare the results of simulations withmeasurements from Pioneer Venus and Venera probes and fromthe Venus Express and Akatsuki missions

Author(s): Helen Parish , Jonathan MitchellInstitution(s): 1. UCLA

417.06 – Vertical profiles for SO and SO on Venusfrom different one-dimensional simulationsSulfur dioxide (SO ) plays many roles in Venus’ atmosphere. It isa precursor for the sulfuric acid that condenses to form the globalcloud layers and is likely a precursor for the unidentified UVabsorber, which, along with CO near the tops of the clouds,

appears to be responsible for absorbing about half of the energydeposited in Venus’ atmosphere [1]. Most published simulationsof Venus’ mesospheric chemistry have used one-dimensionalnumerical models intended to represent global-average ordiurnal-average conditions [eg, 2, 3, 4]. Observations, however,have found significant variations of SO and SO with latitude andlocal time throughout the mesosphere [eg, 5, 6]. Some recentsimulations have examined local time variations of SO and SOusing analytical models [5], one-dimensional steady-state solar-zenith-angle-dependent numerical models [6], and three-dimensional general circulation models (GCMs) [7]. As an initialstep towards a quantitative comparison among these differenttypes of models, this poster compares simulated SO, SO , andSO/SO from global-average, diurnal-average, and solar-zenith-angle (SZA) dependent steady-state models for the mesosphere. The Caltech/JPL photochemical model [8] was used with verticaltransport via eddy diffusion set based on observations andobservationally-defined lower boundary conditions for HCl, CO,and OCS. Solar fluxes are based on SORCE SOLSTICE andSORCE SIM measurements from 26 December 2010 [9, 10]. Theresults indicate global-average and diurnal-average models mayhave significant limitations when used to interpret latitude- andlocal-time-dependent observations of SO and SO. [1] Titov D et al (2007) in Exploring Venus as a TerrestrialPlanet, 121-138. [2] Zhang X et al (2012) Icarus, 217, 714–739. [3]Krasnopolsky V A (2012) Icarus, 218, 230–246. [4] Parkinson CD et al (2015) Planet Space Sci, 113–114, 226–236. [5] Sandor B Jet al (2010) Icarus, 208, 49–60. [6] Jessup K-L et al (2015)Icarus, 258, 309–336. [7] Stolzenbach A et al (2014) EGUGeneral Assembly 2014, 16, EGU2014-5315. [8] Allen M et al(1981) J Geophys Res, 86, 3617–3627. [9] Harder J W et al (2010)Sol Phys, 263, 3–24. [10] Snow M et al (2005) Sol Phys, 230,295–324.

Author(s): Franklin P. Mills , Kandis-Lea Jessup , YukYungInstitution(s): 1. Australian National University, 2. CaliforniaInstitute of Technology, 3. Southwest Research Institute

417.07 – The Variability of the Nightside VenusianIonosphere Observed Over a Solar CycleObservations of ionospheric electron density profiles and auroralemission on the nightside of planetary atmospheres allow for thestudy between the solar wind and the upper atmosphere of aplanet. The interaction between the solar wind and Venus isunique given Venus' thick atmosphere and lack of an intrinsicmagnetic field. Here, we study the variability of the Venusiannightside ionosphere and its connection to the solar wind(particularly after solar storms) and observed auroral-typeemission of the OI 5577.7 oxygen green line. The Venusian nightside ionosphere has two distinct electrondensity region, the V1 and V2 layers located near 125 and 145 km,respectively. They are known to be highly variable on thenightside and are even observed to “disappear” during periods ofincreased solar wind dynamic pressure (Cravens et al. 1982).However, using data from Venus Radio Science (VeRa)instrument onboard Venus Express (VEX), Gray et al. 2016(submitted) have shown an increase in the V1 peak density and adecrease in the V2 peak density during three separate CMEpassages which also coincided with observed green line emission. Here, we compare nightside electron density profiles collected byVEX between 2006 – 2009. We will bin profiles by solar zenithangle and solar wind conditions in an effort to quantify typicalnightside V1 and V2 peak electron densities and altitudes. Thesewill then be compared to profiles collected during known solarstorm conditions.

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Author(s): Candace L. Gray , Kerstin Peter , Bernd Hausler ,Martin Paetzold , Silvia TellmannInstitution(s): 1. Institut für Raumfahrttechnik undWeltraumnutzung, 2. New Mexico State University, 3.Rheinisches Institut für Umweltforschung

417.08 – Radiative transfer modeling for analyseswith Akatsuki/IR2 imagesThe 2-micron camera (IR2) onboard Japanese Venus orbiter,Akatsuki had regularly observed Venus with four narrow-bandfilters (1.735, 2.02, 2.26, and 2.32 micron) from the late of March,2016 until the electronic device was unable to control IR2 onDecember 9, 2016. For approximately nine months, weaccumulated more than 3,000 dayside and nightside images ofVenus. The main purposes of analyzing IR2 data are (i) to studythe dynamics in the upper, middle, and lower atmosphere withthe cloud-tracked winds, (ii) to derive the cloud top altitude withthe 2.02 micron channel which is located in a CO absorptionband, (iii) to deduce CO distribution, which is thought to be agood tracer of the atmospheric circulation below the massiveclouds, by utilizing the 2.26 and 2.32 micron channels, and (iv) toinvestigate aerosol properties of the lower clouds with the 1.735and 2.26 micron channels. For purposes (ii)-(iv), we havedeveloped a line-by-line based radiative transfer model forgenerating synthetic radiance at the IR2 channels. For both solarand thermal radiation cases, adding doubling method (Hovenieret al., 2004; Liu and Weng, 2006) is selected for solving multiplescattering by clouds and molecules. We considered a total of eightmolecules (H O, CO , CO, SO , HF, HCl, OCS, and N ) and lineparameters of the first three molecules are taken from HITEMP10and those of the others are from HITRAN12. For all consideredmolecules, their line shapes are modelled as Voigt function withcutoff of 125 cm . For CO , additional modification is donebased on Tonkov et al. (1996). A cloud model consisting of fourmodal cloud particles with a mixture of 75% H SO and 25%H O is taken from Haus et al. (2013). This model was tested fromnear-infrared to mid-infrared ranges for the spectral analyses ofVenus Express and Venera 15 data, which is useful forinterpreting the very limited spectral information such asAkatsuki data. In this presentation, we will show the detail of theradiative transfer modeling for analyzing the IR2 data and, as itsdemonstration, the primitive results of spatiotemporal variationsof CO abundance in the lower atmosphere.

Author(s): Takao M. Sato , Takehiko Satoh , George LHashimoto , Yeon Joo Lee , Hideo Sagawa , Yasumasa KasabaInstitution(s): 1. ISAS/JAXA, 2. Kyoto Sangyo University, 3.Okayama University, 4. Tohoku University

417.10 – Ultraviolet reflectance spectroscopymeasurements of carbonaceous meteorites andplanetary analog materials The compositions of airless solar system objects tell us about theorigin and evolutionary processes that are responsible for thecurrent state of our solar system and that shape our environment.Spectral reflectance measurements in the ultraviolet are beingused more frequently for providing compositional information ofairless solid surfaces. Most minerals absorb in the UV makingstudying surface composition both informative but alsochallenging [e.g. 1]. The UV region is sensitive to atomic andmolecular electronic absorptions such as the ligand-metal chargetransfer band that is present in oxides and silicates and theconduction band at vacuum UV wavelengths. At the JHU-APL,bidirectional UV reflectance measurements are obtained undervacuum using a McPherson monochrometer with a PMT detectorto achieve measurements over the range from ~ 140 nm to ~ 570nm. Sample temperature can also be controlled from ~ 100K to ~600K, which enables the exploring the interaction of water iceand other volatiles with refractory samples. We have measuredthe UV spectra of many carbonaceous chondrites, includingMokoia, Vigarano, Warrenton, Orgueil, SaU290, and Essebi. Inaddition to being dark, some also possess on OMCT band. Wehave also obtained IR measurement of these meteorites to explorepossible correlations between their UV and IR spectral

signatures. In addition, we have also measured the UV spectra oflow water content lunar analog glasses and have found acorrelation between the spectral nature of the OMCT band andthe abundance of iron [3]. Also, the spectral signature ofmineralic and adsorbed water in the UV has been investigated.While water-ice has a known strong absorption feature near 180nm (e.g. 4], adsorbed molecular and disassociatively adsorbedOH appear to not be optically active in this spectral region [5]. References: [1] Wagner et al. (1987) Icarus, 69, 14-28.1987; [2]Cloutis et al. (2008) Icarus, 197, 321-347; [3] Greenspon et al.(2012), 43 LPSC, 1659, 2490; [4] Hendrix, A. and C. J. Hansen(2008) Icarus, 193, 323-333; [5] Hibbitts, C.A. (2015) DPS #47,215.05.

Author(s): Charles A. Hibbitts , Karen Stockstill-Cahill ,Driss TakirInstitution(s): 1. JHU-APL, 2. SETI Institute

417.13 – Remote Observations of the Lunar SodiumCoronaWe have designed, built and installed a small robotic coronagraphat the Winer Observatory in Sonoita, Arizona, in order to observethe sodium exosphere out to one-half degree around the Moon.Observations are obtained remotely every available clear nightfrom our home base at Goddard Space Flight Center. Our dataencompass lunations in 2015, 2016, and 2017, thus we have a longbaseline of sodium exospheric calibrated images. We employ anAndover temperature-controlled 1.5 Å wide narrow-band filtercentered on the sodium D2 line, and a similar 1.5 Å filter centeredblueward of the D2 line by 5 Å. Exposures of 10 minutes arerequired to image the sodium corona at good signal to noise.Autoguiding is performed locking onto a small bright crater eachnight. Following each onband-offband exposure pair, on- and off-band images of the lunar surface are collected by taking a 0.1- 0.5second exposures with the open filter. The sodium is calibratedusing the counts in the open Moon images and the Hapkefunction. We use both dark and bright Hapke parameters forcomparison check using Mare and highlands, respectively. Inorder to obtain the sodium profile around the entire limb, theimages are transformed using a polar transform and the profilesare extracted automatically. Example of our resulting images ofthe sodium corona will be shown, with the image of the moon'sdisk (taken subsequently to the occulted coronal image)superimposed on the occulting disk, thus showing the positionand phase of the moon under the disk. We compare our lunarmodel derived from these observations with the data from the UVspectrograph onboard the LADEE spacecraft.

Author(s): Rosemary M. Killen , Thomas H. Morgan ,Andrew PotterInstitution(s): 1. NASA Goddard Space Flight Center, 2.National Solar Observatory/EmeritusContributing team(s): SSERVI DREAM2

417.14 – Detectability Factors for Earth-basedImaging of the LCROSS Ejecta PlumeNASA’s Lunar Crater Observation and Sensing Satellite(LCROSS) mission delivered a kinetic impactor into CabeusCrater on 9 October 2009 [1, 2]. Observing campaigns fromEarth-based telescopes at multiple facilities attempted to obtaintemporally-resolved imaging of the ejecta plume [3], but noEarth-based imaging detections were reported until 2013 afterprocessing images with Principal Component Analysis (PCA)filtering [4]. Subsequently, PCA filtering has revealed plumedetections in two additional cameras and also confirmed a non-detection from one telescope [5, 6]. This combination of detectionand non-detection data is useful in determining the criteria fordetectability in future observations of transient events. The goalof this work is to identify factors contributing to detectability andto establish thresholds applicable to the LCROSS event. We takethe data containing detections and then degrade a specific factorin them until the plume is no longer detectable. These derivedthresholds for factors (e.g., scattered light, temporal resolution,

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spatial resolution, field of view, and signal-to-noise of theilluminated foreground of Cabeus) can be compared to theproperties of the actual non-detection data to identify problemsspecific to its observing conditions or observational setup. Thepercent differences between the thresholds and both the detectiondata and non-detection data may also reveal the relativeimportance of these detectability factors. This work wassupported by NASA’s Lunar Data Analysis Program through grantnumber NNX15AP92G. Observations reported here wereobtained at the MMT Observatory, a joint facility of theSmithsonian Institution and the University of Arizona.

References: [1] Colaprete, A. et al. (2010) Science, 330, 463–468.[2] Schultz, P. H. et al. (2010) Science, 330, 468–472. [3]Heldmann, J. L. et al. (2012) Space Sci. Rev., 167:93–140,doi:10.1007/s11214-011-9759-y. [4] Strycker, P. D. et al. (2013)Nat. Commun., 4:2620, doi:10.1038/ncomms3620. [5] Temme,R. L. et al. (2016) LPS XLVII, Abstract #1166. [6] Schotte, J. M. etal. (2017) LPS XLVIII, Abstract #1503.

Author(s): Paul D. Strycker , Jonathan M Schotte , Ruth LTemme , Nancy J. ChanoverInstitution(s): 1. Calvary Lutheran High School, 2. ConcordiaUniversity Wisconsin, 3. New Mexico State University

417.15 – An algorithm for lunar crater accurateboundary detection based on DEM dataCrater is one of the most significant topographic features whichare widely distributed around the lunar surface. Most of thecraters are originated from the impact of small bodies into thelunar surface and some of them may also be formed by thegeological evolution from the interior of the Moon. Since thecrater dating is a classical way to predict the relative ages of thelunar geological layers, and the geomorphologic parameters of thecraters such as the diameter, depth, and boundary are also ofvalue to study the situation related to lunar surface spaceweathering and geological evolution. In this case, theidentification of lunar craters from lunar exploration data hasalways been a fundamental work for lunar crater study.Nowadays, more and more high resolution DOM and DEM datahave been acquired and released by different lunar explorationmissions such as LRO, SELENE and Chang’ e Missions. Besidesthat, many crater identification methods based on imagerecognition have been developed to automatic identify lunarcraters. Although the location and general shape of the craterscould be roughly detected with these methods, however, most ofthem couldn’t provide an accuracy boundary for the crater.Without an accurate boundary for the crater, the accuratediameter and other parameters for the crater could not bedetected accurately, which might impede the lunar crater study.To solve this problem, we developed an algorithm which coulddetect the accurate boundary for the crater from the DEM data.The main idea of this algorithm is that. Firstly, we searched forthe lowest point in the center area of the crater, and then, we triedto calculate the elevation profile from this lowest point to thepoint around the crater rim, in order to get the top points near thecrater rim, after that, least square method is used to circle fitthese top points, and at last, a accurate circle would be createdwhich could be considered as the accurate boundary of this crater.This algorithm has been implemented in the lunar craterboundary detection based on CE-2 DEM data, and the experimentresult shows that the crater boundary detected with this methodis better that others.

Author(s): Xingguo Zeng , Hongbo Zhang , Wangli ChenInstitution(s): 1. National Astronomical Observatories ofChina

417.16 – 3D terrain reconstruction using Chang’E-3PCAM imagesIn order to improve understanding of the topography of Chang’E-3 landing site, 3D terrain models are reconstructed using PCMAimages. PCAM (panoramic cameras) is a stereo camera systemwith a 27cm baseline on-board Yutu rover. It obtained panoramic

images at four detection sites, and can achieve a resolution of1.48mm/pixel at 10m. So the PCAM images reveal fine details ofthe detection region. In the method, SIFT is employed for featuredescription and feature matching. In addition to collinearityequations, the measure of baseline of the stereo system is alsoused in bundle adjustment to solve orientation parameters of allimages. And then, pair-wise depth map computation is appliedfor dense surface reconstruction. Finally, DTM of the detectionregion is generated. The DTM covers an area with radius of about20m, and centering at the location of the camera. In consequenceof the design, each individual wheel of Yutu rover can leave threetracks on the surface of moon, and the width between the firstand third track is 15cm, and these tracks are clear anddistinguishable in images. So we chose the second detection sitewhich is of the best ability of recognition of wheel tracks toevaluate the accuracy of the DTM. We measured the width ofwheel tracks every 1.5m from the center of the detection region,and obtained 13 measures. It is noticed that the area where wheeltracks are ambiguous is avoided. Result shows that the meanvalue of wheel track width is 0.155m with a standard deviation of0.007m. Generally, the closer to the center the more accurate themeasure of wheel width is. This is due to the fact that thedeformation of images aggravates with increase distance from thelocation of the camera, and this induces the decline of DTMquality in far areas. In our work, images of the four detection sitesare adjusted independently, and this means that there is no tiepoint between different sites. So deviations between the locationsof the same object measured from DTMs of adjacent detectionsites may exist.

Author(s): Wangli Chen , Xingguo Zeng , Hongbo ZhangInstitution(s): 1. Chinese Academy of Sciences

417.17 – Syzygy Information: Lunar Limb Profilesat Total Eclipses of the DecadeThe topographic 3D mapping of the lunar surface by the JapaneseKaguya and NASA's Lunar Reconnaissance Orbiter has led togreatly improved predictions of Baily's beads at total solareclipses. This information has been included in the program SolarEclipse Maestro. Matching the predictions with observations ofBaily's beads made at total solar eclipses, including the 21 August2017 eclipse as well as previous total and annular eclipses, mayeven improve the accuracy of the solar diameter used as astandard by the International Astronomical Union.

Author(s): Jay M. Pasachoff , Xavier Jubier , ErnestWrightInstitution(s): 1. NASA's GSFC, 2. Solareclipsemaestro, 3.Williams College

417.18 – Diagnostic Simulations of the LunarExosphere using Coma and TailThe characteristics of the lunar exosphere can be constrained bycomparing simulated models with observational data of the comaand tail (Lee et al., JGR, 2011); and thus far a few independentapproaches on this issue have been performed and presented inthe literature. Since there are two-different observationalconstraints for the lunar exosphere, it is interesting to find thebest exospheric model that can account for the observedcharacteristics of the coma and tail. Considering various initialconditions of different sources and space weather, we presentpreliminary time-dependent simulations between the initial andfinal stages of the development of the lunar tail. Based on anupdated 3-D model, we are planning to conduct numeroussimulations to constrain the best model parameters from thecoma images obtained from coronagraph observations supportedby a NASA monitoring program (Morgan, Killen, and Potter,AGU, 2015) and future tail data.

Author(s): Dong Wook Lee , Sang J. KimInstitution(s): 1. Kyung Hee University

417.19 – Multi-Band Polarimetry of the LunarSurface. II. Polarization Phase Curve

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Polarimetric observations will be performed for the first time bythe Korea Pathfinder Lunar Orbiter (KPLO). This study have beenpreliminarily studied for the successful performance of the KPLO.Since the degree of polarization depends on the phase angle, thepolarimetric observation is objectively expressed with themaximum-polarization. The maximum-polarization can beestimated from the degree of polarization with several phaseangles using the modified Rayleigh function. We present themaximum-polarization map of whole near-side Moon for the firsttime. The maximum-polarization maps have been constructedwith multiple parameters best-fit and then has been comparedwith the results from the fixed parameters best-fit. Therelationship between multiple parameters best-fits and fixedparameters best-fit is strongly correlated that suggests the fixedparameters best-fit can replace the multiple parameters best-fit.In addition, the maximum-polarization can be estimated withlower phase angle (α > 90°) sets. We confirm the simplifiedmethod to construct the maximum-polarization of surface ofMoon, which can be applied to future space mission whether theobservations are incomplete or with a large uncertainty.

Author(s): Sukbum A Hong , Minsup Jeong , Sungsoo SKim , Chaekyung Sim , YURIY G SHKURATOV , Il-hoon Kim ,Kilho Baek , Young-Jun ChoiInstitution(s): 1. Kharkiv V.N. Karazin National University , 2.Korean Astronomy and Space Science Institute, 3. Kyung HeeUniversity

417.20 – New equipment the ion beam irradiationequipment installed at ISAS / JAXAUnderstanding of the space weathering effect by the solar windimplantation is thought to be important for the interpretation ofthe reflectance spectra on the airless body’s surface [e.g. 1]. It isimportant to elucidate the space weathering effect by hydrogenions and helium ions which account for most of solar wind. Inparticular, it is suggested that the solar wind protons interact withthe minerals in the surface layer of the airless bodies to form OHand H O. To understanding the space weathering effect by solarwind protons will be an important clue to reveal the origin andthe abundance of lunar water [e.g. 2]. Solar wind consists of 95% protons, 4% helium and other ions [3].The energy of protons is mainly 1.1 keV and the one of heliumions is mainly 4 keV. Then, we established the ion beamirradiation equipment in ISAS/JAXA. This device consists of acold cathode ion gun, an ion irradiation chamber, a load lockchamber for specimen preparation and reflection spectrummeasurement, and FTIR. The ion sources capable of irradiationare hydrogen and helium which occupy the most of solar windand it is possible to selectively irradiate each ion with a magneticseparator. The energy can be selected from 500 eV to 5 keV. Theultimate degree of vacuum is about 10 Pa. The samples canmove between the irradiation chamber and the load lock chamberwithout being exposed to the air. Moreover, since the nitrogenpurge is possible for the optical path of FTIR, the influence of theadsorbed water can be ignored when measuring the reflectionspectra. In this presentation, we will report the first results of theperformance of ion beam irradiation equipment (e.g. beamcurrent, beam-shape) and the proton irradiation to Sun Carlosolivine.

[1] T. Noguchi et al., MPS, 49(2):188–214, 2014. [2] C.M. Pieterset al., Science, 326(5952):568–572, 2009. [3] J.T. Gosling,

Encyclopedia of the Solar System (Second Edition), pages 99 –116, 2007. Acknowledgements Part of this work has been supported by the Japan Society for thePromotion of Science KAKENHI Grant Numbers JP15H05695,JP16H04044, Core-to-Core program (International Network ofPlanetary Sciences).

Author(s): Yusuke Nakauchi , Toru Matsumoto , YumaAsada , Masanao Abe , Akira Tsuchiyama , Aki Takigawa ,Naoki WatanabeInstitution(s): 1. Institute of Low Temperature Science,Hokkaido University, 2. Japan Aerospace Exploration Agency,3. Kyoto University, 4. University of AizuContributing team(s): Yusuke Nakauchi

417.21 – Coupled Photochemical and CondensationModel for the Venus AtmosphereGround based and Venus Express observations have provided awealth of information on the vertical and latitudinal distributionof many chemical species in the Venus atmosphere [1,2]. Previous1D models have focused on the chemistry of either the lower [3]or middle atmosphere [4,5]. Photochemical models focusing onthe sulfur gas chemistry have also been independent from modelsof the sulfuric acid haze and cloud formation [6,7]. In recent yearssulfur-bearing particles have become important candidates forthe observed SO2 inversion above 80 km [5]. To test thishypothesis it is import to create a self-consistent model thatincludes photochemistry, transport, and cloud condensation. In this work we extend the domain of the 1D chemistry model ofZhang et al. (2012) [5] to encompass the region between thesurface to 110 km. This model includes a simple sulfuric acidcondensation scheme with gravitational settling. Itsimultaneously solves for the chemistry and condensationallowing for self-consistent cloud formation. We compare theresulting chemical distributions to observations at all altitudes.We have also validated our model cloud mass against pioneerVenus observations [8]. This updated full atmosphere chemistrymodel is also being applied in our 2D solver (altitude andaltitude). With this 2D model we can model how the latitudinaldistribution of chemical species depends on the meridionalcirculation. This allows us to use the existing chemicalobservations to place constraints on Venus GCMs [9-11]. References: [1] Arney et al., JGR:Planets, 2014 [2] Vandaele etal., Icarus 2017 (pt. 1 & 2) [3] Krasnopolsky, Icarus, 2007 [4]Krasnopolsky, Icarus, 2012 [5] Zhang et al., Icarus 2012 [6] Gaoet al., Icarus, 2014 [7] Krasnopolsky, Icarus, 2015 [8] Knollenbergand Hunten, JGR:Space Physics, 1980 [9] Lee et al., JGR:Planets,2007 [10] Lebonnois et al., Towards Understanding the Climateof Venus, 2013 [11] Mendoncca and Read, Planetary and SpaceScience, 2016

Author(s): Carver Bierson , Xi Zhang , Joao Mendonca ,Mao-Chang LiangInstitution(s): 1. Research Center for Environmental Changes,Academia Sinica, 2. UC Santa Cruz, 3. University of Bern

418.01 – ExoMars Trace Gas Orbiter providesatmospheric data during Aerobraking into its finalorbitAfter the arrival of the Trace Gas Orbiter (TGO) at Mars on 19October 2016 a number of initial orbit change manoeuvres wereexecuted and the spacecraft was put in an orbit with a 24 hourperiod and 74 degrees inclination. The spacecraft and its fourinstruments were thoroughly checked out after arrival and a fewmeasurements and images were taken in November 2016 and in

Feb-March 2017. The solar occultation observations havehowever not yet been possible due to lack of the proper geometry. On 15 March a long period of aerobraking to reach the final400km semi-circular frozen orbit (370x430km, with a fixedpericentre latitude). This orbit is optimised for the payloadobservations and for the communication relay with the ExoMarsRover, due to arrive in 2021. The aerobraking is proceeding well and the final orbit is expectedto be reached in April 2018. A large data set is being acquired forthe upper atmosphere of Mars, from the limit of the sensitivity of

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the accelerometer, down to lowest altitude of the aerobraking atabout 105km. Initial analysis has shown a highly variableatmosphere with a slightly lower density then predicted byexisting models. Until the time of the abstract writing no duststorms have been observed. The ExoMars programme is a joint activity by the EuropeanSpace Agency(ESA) and ROSCOSMOS, Russia. ESA is providingthe TGO spacecraft and Schiaparelli (EDM) and two of the TGOinstruments and ROSCOSMOS is providing the Proton launcherand the other two TGO instruments. After the arrival of theExoMars 2020 mission, consisting of a Rover and a Surfaceplatform also launched by a Proton rocket, the TGO will handlethe communication between the Earth and the Rover and SurfacePlatform through its (NASA provided) UHF communicationsystem.

Author(s): Hakan Svedhem , Jorge L. Vago , SeanBruinsma , Ingo Müller-WodargInstitution(s): 1. CNES, 2. ESA/ESTEC, 3. Imperial CollegeContributing team(s): ExoMars 2016 Team

418.02 – Predicting Atmospheric Ionization andExcitation by Precipitating SEP and Solar WindProtons Measured By MAVENPrecipitating energetic particles ionize and excite planetaryatmospheres, increasing electron content and producing aurora.At Mars, the solar wind and solar energetic particles (SEPs) canprecipitate directly into the atmosphere because solar windprotons can charge exchange to become neutral and pass themagnetosheath, and SEPs are sufficiently energetic to cross themagnetosheath unchanged. We will compare ionization andLyman alpha emission rates for solar wind and SEP protonsduring nominal solar activity and a CME shock front impact eventon May 16 2016. We will use the Atmospheric Scattering ofProtons and Energetic Neutrals (ASPEN) model to compareexcitation and ionization rates by SEPs and solar wind protonscurrently measured by the SWIA (Solar Wind Ion Analyzer) andSEP instruments aboard the MAVEN spacecraft. Results will helpquantify how SEP and solar wind protons influence atmosphericenergy deposition during solar minimum.

Author(s): Rebecca Jolitz , Chuanfei Dong , Christina Lee ,Rob Lillis , David Brain , Shannon Curry , Jasper Halekas ,Stephen W. Bougher , Bruce JakoskyInstitution(s): 1. Climate and Space Sciences and Engineering,University of Michigan, 2. Princeton University, 3. UC BerkeleySpace Sciences Lab, 4. University of Colorado, Boulder, 5.University of Iowa

418.03 – Observations of Highly VariableDeuterium in the Martian Upper AtmosphereOne of the key pieces of evidence for historic high levels of wateron Mars is the present elevated ratio of deuterium/hydrogen(D/H) in near-surface water. This can be explained by the loss oflarge amounts of water into space, with the lighter H atomsescaping faster than D atoms. Understanding the specific physicalprocesses and controlling factors behind the present escape of Hand D is the key objective of the MAVEN IUVS echelle channel.This knowledge can then be applied to an accurate extrapolationback in time to understand the water history of Mars.Observations of D in the martian upper atmosphere over the firstmartian year of the MAVEN mission have shown highly variableamounts of D, with a short-lived maximum just after perihelionand during southern summer. The timing and nature of thisincrease provide constraints on its possible origin. These resultswill be presented and compared with other measurements of theupper atmosphere of Mars.

Author(s): John T. Clarke , Majd A Mayyasi-Matta , DolonBhattacharyya , Jean-Yves Chaufray , Michael S. Chaffin , JustinDeighan , Nicholas M. Schneider , Sonal Jain , Bruce JakoskyInstitution(s): 1. Boston Univ., 2. LATMOS / CNRS, 3. Univ. ofColorado

418.04 – Waves in the middle and upperatmosphere of Mars as seen by the Radio ScienceExperiment MaRS on Mars ExpressAtmospheric waves play a crucial role for the dynamics in theMartian atmosphere. They are responsible for the redistributionof momentum, energy and dust and the coupling of the differentatmospheric regions on Mars. Almost all kinds of waves have been observed in the loweratmosphere (e.g. stationary and transient waves, baroclinic wavesas well as migrating and non-migrating thermal tides, and gravitywaves). Atmospheric waves are also known to exist in the middleatmosphere of Mars (~70-120 km, e.g. by the SPICAM instrumenton Mars Express). In the thermosphere, thermal tides have beenobserved e.g. by radio occultation or accelerometermeasurements on MGS. Recently, the NGIMS instrument onMAVEN reported gravity waves in the thermosphere of Mars. Radio Science profiles from the Mars Express Radio Scienceexperiment MaRS on Mars Express can analyse the temperature,pressure and neutral number density profiles in the loweratmosphere (from a few hundred metres above the surface up to~ 40-50 km) and electron density profiles in the ionosphere ofMars. Wavelike structures have been detected below the mainionospheric layers (M1 & M2) and in the topside of theionosphere. The two coherent frequencies of the MaRSexperiment allow to discriminate between plasma densityfluctuations in the ionosphere and Doppler related frequencyshifts caused by spacecraft movement. A careful analysis of the observed electron density fluctuations incombination with sensitivity studies of the radio occultationtechnique will be used to classify the observed fluctuations. The MaRS experiment is funded by DLR under grant 50QM1401.

Author(s): Silvia Anna Tellmann , Martin Paetzold , BerndHäusler , David P. Hinson , Kerstin Peter , G. Leonard TylerInstitution(s): 1. Carl Sagan Center, SETI Institute, 2.Department of Electrical Engineering, Stanford University, 3.Institut für Raumfahrttechnik und Weltraumnutzung,Universität der Bundeswehr, 4. Rheinisches Institut fürUmweltforschung

418.05 – Regions of enhanced density in theMartian exosphereThe Neutral Gas and Ion Mass Spectrometer (NGIMS)instrument on the Mars Atmosphere and Volatile EvolutioNMission (MAVEN) provides in-situ measurements of neutral andion gases in the Martian exosphere. We studied thesemeasurements for atomic oxygen, argon, and carbon dioxide for afull Martian year and discovered that in roughly 10% of the orbits,there is a significant and sharp increase in density versus altitudeabove the calculated neutral exobase. We calculate temperatureand scale height profiles for these orbits that suggest local heatingon the order of several hundred degrees Kelvin is likely occurringand investigate the causes of these features using both correlationwith other MAVEN data and atmospheric modeling. Thesefeatures do not appear to correspond with any particular locationor local time, nor do they appear to correlate with solar windvariables. Therefore, it is possible that these are either the resultof gravity waves propagating above the exobase or are producedby the stochastic ion precipitation environment. Using models,we compare both of these scenarios to the existing data.

Author(s): Hayley Williamson , Robert E. Johnson ,Meredith K Elrod , Shannon Curry , Ludivine Leclercq ,Orenthal TuckerInstitution(s): 1. NASA GSFC, 2. UC Berkeley, 3. University ofVirginia

418.06 – First Detection of the Nitric OxideDayglow on MarsNitric oxide (NO) is a well-known indicator of solar and auroralactivity in the terrestrial upper atmosphere. Direct measurementsof NO on Mars can therefore constrain studies of energetic

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processes controlling the composition and structure of its upperatmosphere (80-200 km). Identifying and quantifying theseprocesses is one of the science objectives of NASA’s MarsAtmosphere and Volatile Evolution (MAVEN) mission currentlyorbiting Mars. NO can be observed directly by solar resonancefluorescence in the mid-ultraviolet (MUV). Indeed, this approachhas routinely been used to measure terrestrial NO for 50 years.On Mars, this “dayglow” emission is very weak relative to otherbright MUV features and thus has confounded attempts at itsdetection there for nearly the same amount of time. Here, wereport the first detection of the NO dayglow in the Martianatmosphere using limb observations by the Imaging UltravioletSpectrograph (IUVS) on the MAVEN spacecraft. The detection isenabled by the spectral modeling and removal of the carbonmonoxide Cameron bands, which dominate the MUV limbspectra. We focus on the spectral region between 213.0-225.5 nm,where three NO gamma bands emit. We will infer NO densitiesfrom the dayglow spectra and compare our observations withpredictions from a photochemical model. We will discuss theimplications, particularly in the context of previous in situmeasurements.

Author(s): Michael H. Stevens , David E. Siskind , J. ScottEvans , Jane L. Fox , Sonal Jain , Justin Deighan , Nicholas M.Schneider , A. Ian F. Stewart , Matteo Crismani , ArnaudStiepen , Michael S. Chaffin , William E. McClintock , GregHolsclaw , Franck Lefevre , Daniel Lo , John T. Clarke , FranckMontmessin , Bruce JakoskyInstitution(s): 1. Boston University, 2. CPI, 3. LATMOS, 4.NRL, 5. University of Arizona, 6. University of Colorado, 7.University of Liege, 8. Wright State University

418.07 – MAVEN/IUVS observations of dayglowemissions on Mars: indicator of dynamics,energetics, physical processes, and couplingbetween lower and upper atmosphereThe dayglow emissions are a common feature of any planetaryatmosphere. These emissions provide basic information about theatmospheric composition and structure, and can be used to studyenergy deposition, dynamics, and chemistry. The ImagingUltraviolet Spectrograph (IUVS) aboard the MAVEN spacecrafthas been observing mid and far ultraviolet emissions from theMartian upper atmosphere for over one Martian year and haveprovided the first long term observations of Martian dayglow.These observations have been used to characterize Martianthermospheric temperatures, densities, and their variations withsolar activity, seasons, and dust activities. This data set hasenabled us to track short and long term seasonal and spatialvariations and their relationship with both solar forcing from topof the atmosphere and coupling from lower atmosphere (viatides/waves/dust storms). The scale heights retrieved from CO2+Ultraviolet Doublet band emission shows 25% reduction from Ls= 218 degree (near perihelion; Mars year 32) to Ls = 60 degree (ataphelion; MY 33), indicating effect of both decline in solar activityas well as increase in Mars-Sun distance. At the onset of aregional dust storm at Ls = 219 (during MY 33), we noticed about16% increase in the altitude of maximum intensities of major UVemission (indicating increase in neutral column density),however, we did not notice any significant warming inthermosphere associate with this dust storm. The results presented herein will help us better understandproperties of the Martian thermosphere.

Author(s): Sonal Jain , Justin Deighan , A. Ian Stewart ,Nicholas M. Schneider , J. Scott Evans , Michael H. Stevens ,Michael S. Chaffin , Matteo Crismani , Majd A Mayyasi-Matta ,Frank Eparvier , Ed Thiemann , Phillip C. ChamberlinInstitution(s): 1. Boston University, 2. Computational Physics,Inc., 3. Laboratory for Atmosphere and Space Physics,University of Colorado at Boulder, 4. NASA/GSFC, 5. NRL

418.08 – Sensible Ozone on Mars Based on 2-DMaps of O (a △ ) Emission for L =309° Using

iSHELL (NASA-IRTF)We report 2-D maps of the O (a △ ) emission rate (a tracer forhigh-altitude ozone) taken during mid-Northern Winter on Mars(L =309.5°, 01 Feb 2017) using iSHELL, a cross-dispersedechelle-grating spectrograph (1.1 - 5.3 µm) with a resolving powerof ~ 70,000, at the NASA-IRTF. The J2 setting encompasses 39orders (1.2 to 1.3 µm). Both the (0-0) and the (1-1) bands may bemeasured in three of these orders. The entrance slit waspositioned N-S on Mars and stepped E-W at 1.0 arc-secincrements. Spectral extracts were taken at 0.6 arc-sec intervals.A model consisting of the solar continuum with Fraunhofer lines,two-way transmission through Mars' atmosphere, and one-waytransmission through Earth's atmosphere was used to isolate andanalyze spectral emission of individual a-X lines from Mars. Theline-of-sight emission intensities were converted to verticalemission rates and O (a △ ) column densities after geometriccorrection; 2-D longitude-latitude maps of O (a △ ) wereconstructed from the stepped measurements. The map of sensible O column implied by these data will becompared with maps of total O in Mars standard atmospheremodels. Our iSHELL 2-D map shows O (a △ ) emissionconcentrated in the Northern mid-latitude region and nodetectible emissions in the tropical and Southern latitudes. These2-D maps will be compared to previously reported CSHELL mapstaken during mid-Northern Summer (L =155°) and late NorthernWinter (L =357°). Also, our 1-D map of the O (a △ ) (0-0) bandemission (Local Time ~ 14:30) will be compared with MARCI Oresults (LT ~ 15:00, Clancy et al., Icarus 266 (2016) 112-113). Oursearch for the (1-1) a-X band emissions yielded no detectionsabove the noise level. An upper limit will be presented, andimplications discussed. This work was partially funded by a grantfrom NASA's Mars Fundamental Research Program (11-MFRP11-0066). The NASA Astrobiology Institute supported this workthrough funding awarded to the Goddard Center for Astrobiologyunder proposal 13-13NAI7-0032. We thank the administrationand staff of the NASA-IRTF for awarding observing time,coordinating and supporting our observations, and instructing uson using iSHELL.

Author(s): Robert E. Novak , Michael J. Mumma ,Geronimo Luis Villanueva , Sara FaggiInstitution(s): 1. Iona College, 2. NASA-GSFC

418.09 – Diurnal Variations of Emissions of Osinglet Delta Near Mars' Northern Summer Solstice We are presenting results of O singlet Delta emission, a tracerfor ozone, in the Martian atmosphere for observations takenbefore Mars’ Northern summer solstice (L = 88 , February 10,2014 ). The data were taken using CSHELL on the NASA-IRTFtelescope located on Mauna Kea in Hawaii. The slit waspositioned east-west on Mars and we observed diurnal variationsat 20 N and 60 N. Spectral/spatial images were taken with aspectral resolution above 38,000. Mars’ relative velocity of -16km/s enabled us to separate the Martian emission lines from thetelluric absorption lines. Raw images were cleaned by removingdead and hot pixels. The images were then adjusted so that thespatial dimension was perpendicular to the spectral dimension.Extracts at 0.6 arcsec spatial resolution were taken which allowedus to measure Martian emission peaks. The Martian data werecalibrated by taking similar observations from a standard star(HR4689) using the temperature, wavelength, and intensity ofthe star to calibrate the flux density. A Boltzmann analysis wasperformed on the observed emission peaks to obtain therotational temperature of the excited O . From this, the totalemission rates were obtained. We found that at both latitudinallocations, the greatest emissions occured between 12:00- 13:00local time on Mars. The emission intensity increases during themorning hours and then decreases towards sunset. We thank the administration and staff of the NASA-IRTF forobservation time and for their assistance during operations of thetelescope. We also thank Drs. M. Mumma and G. Villanueva ofthe NASA Goddard Space Flight Center with whom wecollaborate.

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418.10 – Dust on Mars from MSL EngineeringCamerasThe Mars Science Laboratory (MSL) Engineering Cameras were designed for supporting the rover surfaceoperations. The navigation camera has a field of view of 45 square degrees, whilethe hazard avoidance camera, located at the front and rear of the rover andpointing downwards, counts with a 124 square degrees field of view. Theirimage database and sky coverage provides useful information forcharacterising the dust aerosol physical properties at Gale Crater, complementingthe data retrieved from scientific cameras. In this work, we have reviewedand calibrated the images from the MSL engineering cameras. Theatmosphere extinction values database has been extended. Observations atlow scattering angle have been used to reproduce the dust forward scatteringpeak and the dust size distribution has been inferred from the sky brightnessmeasurements using a discrete ordinates radiative transfer code.

Author(s): Hao Chen-Chen , A. Sanchez-Lavega , SantiagoPerez-HoyosInstitution(s): 1. Escuela de Ingenieria de Bilbao (UPV/EHU)

418.12 – Martian thermal tides from the surface tothe atmosphereThe presence of observational platforms both in orbit and on thesurface of Mars today provides a unique opportunity tosimultaneously study the effects of thermal tides at the surface,above that surface location and in the atmosphere. Thermal tidesare an important aspect of the atmospheric dynamics on Marsand the unique opportunity to unify landed and orbitalmeasurements can provide a comprehensive understanding ofthermal tides. Ideally, pressure measurements from the Curiosity lander andatmospheric temperature profiles from the Mars Climate Sounder(MCS) onboard Mars Reconnaissance Orbiter provide acomplimentary pair of surface and atmospheric observations tostudy. However, the unique landing site of Curiosity, in Galecrater, introduces several complicating factors to the analysis oftidal behavior, two of which are crater circulation and the impactof the dichotomy boundary topography. In order to achieve a baseline understanding of thermal tidalbehavior another complimentary pair of observations isnecessary. For this purpose, the equatorial and relativelytopographically flat landing site of the Viking 1 (VIK1) lander,along with its lengthy record of surface pressures, is the candidatesurface dataset. There are no concurrent atmosphericobservational data, so atmospheric profiles were obtained fromthe Mars Climate Database to ensure maximum coverage in spaceand time. 2-dimensional Fourier analysis in local time and longitude hasyielded amplitude and phases for the four major tidal modes onMars (diurnal and semidiurnal migrating tides, DK1 and DK2).We will present current results regarding amplitude and phasedependence on season and altitude at the VIK1 landing site. Theseresults will (in time) be tied to tidal amplitude and phase behaviorfrom observed MCS atmospheric temperature profiles from“appropriately quiet” Mars years (years without major duststorms). The understanding gathered from this approach willthen allow us to return to the pressure measurements fromCuriosity in Gale Crater, and assess to what degree the “pure”

tidal signatures are muddled by various complicating factors, e.g.topography.

Author(s): Christina Holstein-Rathlou , Paul WithersInstitution(s): 1. Boston University

418.13 – Large-Scale Traveling Weather Systems inMars’ Southern ExtratropicsBetween late fall and early spring, Mars’ middle- and high-latitude atmosphere supports strong mean equator-to-poletemperature contrasts and an accompanying mean westerly polarvortex. Observations from both the MGS Thermal EmissionSpectrometer (TES) and the MRO Mars Climate Sounder (MCS)indicate that a mean baroclinicity-barotropicity supports intense,large-scale eastward traveling weather systems (i.e., transientsynoptic-period waves). Such extratropical weather disturbancesare critical components of the global circulation as they serve asagents in the transport of heat and momentum, and generalizedscalar/tracer quantities (e.g., atmospheric dust, water-vapor andice clouds). The character of such traveling extratropical synopticdisturbances in Mars' southern hemisphere during late winterthrough early spring is investigated using a moderately high-resolution Mars global climate model (Mars GCM). This MarsGCM imposes interactively-lifted and radiatively-active dustbased on a threshold value of the surface stress. The modelexhibits a reasonable "dust cycle" (i.e., globally averaged, adustier atmosphere during southern spring and summer occurs).Compared to the northern-hemisphere counterparts, thesouthern synoptic-period weather disturbances andaccompanying frontal waves have smaller meridional and zonalscales, and are far less intense. Influences of the zonallyasymmetric (i.e., east-west varying) topography on southernlarge-scale weather are investigated, in addition to large-scale up-slope/down-slope flows and the diurnal cycle. A southern stormzone in late winter and early spring presents in the westernhemisphere via orographic influences from the Tharsis highlands,and the Argyre and Hellas impact basins. Geographically localizedtransient-wave activity diagnostics are constructed thatilluminate dynamical differences amongst the simulations andthese are presented.

Author(s): Jeffery L. Hollingsworth , Melinda A. KahreInstitution(s): 1. NASA Ames Research Center

418.14 – Spectral Generation from the Ames MarsGCM for the Study of Martian CloudsStudies of martian clouds come from two distinct groups ofresearchers: those modeling the martian system from firstprinciples and those observing Mars from ground-based andorbital platforms. The model-view begins with global circulationmodels (GCMs) or mesoscale models to track a multitude of statevariables over a prescribed set of spatial and temporalresolutions. The state variables can then be processed intodistinct maps of derived product variables, such as integratedoptical depth of aerosol (e.g., water ice cloud, dust) or columnintegrated water vapor for comparison to observational results.The observer view begins, typically, with spectral images orimaging spectra, calibrated to some form of absolute units thenrun through some form of radiative transfer model to alsoproduce distinct maps of derived product variables. Both groupsof researchers work to adjust model parameters and assumptionsuntil some level of agreement in derived product variables isachieved. While this system appears to work well, it is in somesense only an implicit confirmation of the model assumptionsthat attribute to the work from both sides. We have begun aproject of testing the NASA Ames Mars GCM and key aerosolmodel assumptions more directly by taking the model output andcreating synthetic TES-spectra from them for comparison toactual raw-reduced TES spectra. We will present somepreliminary generated GCM spectra and TES comparisons.

Author(s): David R. Klassen , Melinda A. Kahre , Michael J.Wolff , Robert Haberle , Jeffery L. HollingsworthInstitution(s): 1. NASA Ames Research Center, 2. RowanUniv., 3. Space Science Institute

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418.15 – Constraining the Surficial Liquid Waterand Resulting Atmospheric Water VaporAbundance at Recurring Slope Lineae (RSL)Locations on MarsPossible signatures of atmospheric water vapor arising fromMartian Recurring Slope Lineae (RSLs) are investigated in thisstudy. RSLs appear during local spring and summer ondownward, equator-facing slopes at southern mid-latitudes (~31-52°S; Stillman et al. 2014), and have been linked to liquid waterwhich leaves behind streaks of briny material (McEwen et al.2011, McEwen et al. 2014). Viking Orbiter Mars AtmosphericWater Detector (VO MAWD) and Mars Global Surveyor ThermalEmission Spectrometer (MGS TES) derived atmospheric watervapor abundance values are interrogated to determine whetherfour RSL locations at southern mid-latitudes (Palikir Crater, HaleCrater, Horowitz Crater, Coprates Chasma) exhibit episodic,enhanced local atmospheric water vapor abundance duringsouthern spring and summer (L = 180-360°) when RSLs areobserved to develop (Stillman et al. 2014, Ojha et al. 2015).Significant water vapor signals at these locations might revealRSLs as the source of the enhanced water vapor. Detectedatmospheric water vapor signals would expand upon currentknowledge of RSLs, whereas non-detection could provide upperlimits on RSL water source content. In order to assess how muchsurficial RSL water would be required to produce a detectablesignal, we utilize the high spatial resolution Geophysical FluidDynamics Laboratory Mars Climate General Circulation Model tosimulate the evaporation of RSL-producing surface water andquantify the magnitude and temporal duration of water vaporcontent that might be anticipated in response to inferred RSLsurface water release. Finally, we will assess the ability of past andfuture orbiter-based instruments to detect such water vaporquantities.

Author(s): Jodi Berdis , Jim Murphy , Robert John WilsonInstitution(s): 1. NASA Ames Research Center, 2. New MexicoState University

418.16 – The Role of CO Clouds on the Stability ofthe Early Mars Atmosphere Against CollapseThe early Mars atmosphere was likely significantly more massivethan it is today, given the growing body of evidence that liquidwater flowed on the surface early in the planet’s history. Althoughthe CO inventory was likely larger in the past, there is much westill do not understand about the state of that CO . As surfacepressure increases, the temperature at which CO condenses alsoincreases, making it more likely that CO ice would form andpersist on the surface when the atmospheric mass increases. Anatmosphere that is stable against collapse must contain enoughenergy, distributed globally, to prohibit the formation ofpermanents CO ice reservoirs that lead to collapse. The presenceof the “faint young sun” compounds this issue. Previous globalclimate model (GCM) investigations show that atmosphereswithin specific ranges of obliquities and atmospheric masses arestable against collapse. We use the NASA Ames Mars GCM toexpand on these works by focusing specifically on the role of COclouds in atmospheric stability. Two end member simulations areexecuted, one that includes CO cloud formation and one thatdoes not. The simulation that explicitly includes CO clouds isstable, while the simulation without CO clouds collapses intopermanent surface CO reservoirs. In both cases, significantatmospheric condensation is occurring in the atmospherethroughout the year. In the case without CO clouds, allatmospheric condensation (even if it occurs at altitude) leadsdirectly to the accumulation of surface ice, whereas in the casewith CO clouds, there is a finite settling timescale for the cloudparticles. Depending on this timescale and the local conditions,the cloud particles could stay aloft or sublimate as they falltoward the surface. Thus, the striking difference between thesetwo cases illustrates the important role of CO clouds. We plan toconduct and present further simulations to better understandhow atmospheric stability depends on the details of CO cloudmicrophysical processes and assumptions.

Author(s): Melinda A. Kahre , Robert Haberle , KathrynSteakley , Jim Murphy , Alexandre KlingInstitution(s): 1. BAER Institute, 2. NASA Ames ResearchCenter, 3. New Mexico State University

418.17 – Understanding the twists and turns ofmartian linear gulliesSince “linear gullies” were first identified on the martian surfaceon the Russell Crater megadune, these long, relatively uniform-width troughs-with-terminal-pits have engendered much debateabout their formation mechanism. A broad model of sublimingCO ice blocks sliding down the sandy slopes (Diniega et al.,2013, Icarus 225) seems the most probable, but this model needsrefinement to account for the large range of observed linear gullymorphologies. The first survey of martian linear gullies byPasquon et al. (2016, Icarus 274) identified three regionscontaining linear gullies – Hellespontus (~45°S, 40°E), AoniaTerra (~50°S, 290°E), and Jeans (~70°S, 155°E) – on the slopesof dunes with a range of shapes and sizes. Within several fieldswithin each region, we have collected morphologicalmeasurements and evidence of present-day activity, over the lastfour Mars years. Comparing our measurements with Pasquon etal.’s, we have found differences between linear gullies found inthe different fields, which we hypothesize are due to regionalenvironmental differences. This presentation focuses on theoccurrence of sinuosity within the linear gully troughs. Within asingle linear gully the trough can veer from a sinuosity ratio of 1(i.e., straight) to >1.3. The curves can have a wavelength from ~1to >10 times the trough width, and magnitude of a few times thetrough width. Within a cluster of linear gullies, the features willgenerally start and end in the same areas and go in the overallsame direction (i.e., they don’t cross or diverge significantly awayfrom each other), but can have very different amounts ofsinuosity. We investigate correlations between sinuosity and thefeeder “alcove” shape and size, the underlying slope and small-scale topography, and environmental variations such as long-retained frost deposits.

Author(s): Serina Diniega , Matthew Maclay , VicenteOchoa , Kimberly Marie Morales , Mary Bourke , CandiceHansen , Jim McElwaine , Joanna NieldInstitution(s): 1. Arizona State University, 2. Carleton College,3. Jet Propulsion Laboratory, California Institute of Technology,4. Planetary Science Institute, 5. University of SouthernCalifornia, 6. University of Southhampton

418.19 – CO2 Jets and Wind Patterns on MarsIn Martian winters, the poles get covered by a layer of transparentCO2 ice. In spring, sunlight causes substrate under the ice to heatup which sublimates CO2 under the ice. The accumulating gaseventually causes the ice above it to rupture and the CO2 andsubstrate mixture spews out like a geyser and settles back downon the surface. The shape, size, and alignment of the deposits onthe surface as viewed by the HiRISE camera are related tophysical processes like sublimation, weather, and wind on Mars.The jet deposits are identified by citizen scientists on a websitecalled Planet Four. Users are shown sections of HiRISE imagesand asked to mark different surface features with different tools.The markings are averaged, filtered, and sorted to ensure that thedata accurately represents the images. By analyzing trends in thechange of different characteristics of these surface features overtime, we conclude that different regions on Mars have differentsublimation processes and different wind patterns. We alsoconclude that wind and weather patterns generally repeat fromyear to year, and that sediment deposits affect local weather aswell.

Author(s): Chase Hatcher , K-Michael Aye , GannaPortyankinaInstitution(s): 1. The University of North Carolina at ChapelHill, 2. University of Colorado - Boulder

418.20 – Constraining physical properties ofcompositionally-distinct Martian bedrock surfaces

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using overlapping THEMIS observations and theKRC thermal modelThe physical properties of Martian surface materials (e.g. grainsize, cohesion, porosity, amount of induration, rock abundance,etc.) provide clues to the origins of, and processes involved (e.g.sedimentary, effusive volcanic, pyroclastic) in, forming rockoutcrops on Mars. Many outcrop surfaces likely possess verticalheterogeneity in the near-surface (<3 cm), caused by processessuch as sediment transport, induration, or physical weathering,that can mask the true thermal properties of outcrop materials.However, this heterogeneity can cause unique and predictabletemperature patterns both seasonally and diurnally, which we canuse to ultimately determine both the nature of verticalheterogeneity and the thermal inertia of the outcrop below. To dothis, we use the KRC thermal model to model surfacetemperatures and thermal inertias from overlapping MarsOdyssey THEMIS surface temperature observations spanningmultiple seasons and local times. We constrain top layer particlesizes from TES and CRISM spectral observations. Currently, weare focusing on chloride-bearing units in Terra Sirenum andMeridiani Planum and spectrally-distinct mafic and feldspathicbedrock units with uncertain origins and histories in NoachisTerra and Nili Fossae. The variations in apparent thermal inertiaover local times and seasons suggests that most of these surfacesare consistent with low thermal inertia materials (~200 tiu)overlying moderately-high thermal inertia (600 tiu) surfaces.Work will be ongoing to further constrain top and lower layerthermal inertias for these areas and other spectrally andphysically-distinctive outcrops over the surface of Mars.

Author(s): Alexandra Ahern , A. Deanne RogersInstitution(s): 1. Stony Brook University

418.21 – The M projectAn essential part of revealing the past conditions that occurred atthe surface of Mars is determining its mineralogy. Igneouscompositions can provide insight into mechanisms such as crustalformation, magma differentiation and volcanic activity, whileclays, salts and other altered phases can constrain the past liquidwater environments on/near the surface. The visible near-infrared imaging spectrometer OMEGA on board the ESA MarsExpress mission provided major steps in our understanding of thecomposition of the Martian surface by mapping anhydrous andhydrated minerals (Riu et al. 2017; Carter et al. 2017). Theultimate step in interpreting IR OMEGA data is a quantitativeretrieval of mineral abundances from the modeling of spectra ofselected terrains. So far, such an approach was performed onrestricted areas of the surface using a radiative transfer model(Poulet et al., 2009, 2014). The purpose of the M (ModalMineralogy of Mars) project is thus to provide global distributionsof Martian surface minerals using previous OMEGAinvestigations, and to distribute the mineral maps to the sciencecommunity through the web portal PSUP (Poulet et al. 2017).Two types of terrains are considered: type 1: mafic-bearing ones;type 2: hydrated deposits. For type-1 terrains, a 3-D global image cube was constructedcontaining atmospheric- and aerosol-corrected NIR spectradistributed over 32px/° and +/-60° of latitude with a surfacecoverage of 90%. NIR reflectance spectra were modeled toretrieve mineral abundances and particle grain sizes of the mafic-bearing terrains. This work is completed with final mapspresented this year (Riu et al. 2017). For type-2 terrains, a specific approach is required. First,signatures of hydrated minerals are detected for each singleOMEGA cube. Second, the spectral modeling is applied to eachpixel and then the modeled abundances are averaged whenoverlapping observations occur for a specific location. Thevalidation of this approach has been performed on two regionsthat exhibit the greatest mineral diversity of hydrated minerals onMars: Nilo-Syrtis region and Mawrth Vallis/Oxia Planum region.Mineral maps of various hydrated and primary phases will bepresented.

Author(s): Francois Poulet , John Carter , Lucie Riu ,Antoine Martinez , Jean-Pierre Bibring , Brigitte Gondet , YvesLangevinInstitution(s): 1. Institut d'Astrophysique Spatiale

418.22 – Effects of Martian Surface Materials onthe Thermal Decomposition of Hydrogen PeroxideWhile hydrogen peroxide (H O ) has been detected in themartian atmosphere, it has not been detected in surfacematerials. Since the Viking lander mission, we have sentinstruments to Mars with the capability to detect H O . TheSample Analysis at Mars (SAM) instrument onboard the CuriosityRover and Thermal and Evolved Gas Analyzer (TEGA) instrumenton the Phoenix lander both detected water and oxygen releasesfrom analyzed sediments but whether or not peroxide could bethe source of these gases has not been investigated. We areinvestigating the possible presence of H O in martian materialsby analyzing Mars-relevant minerals that have been mixed withhydrogen peroxide using lab instruments configured as analogs toMars mission instruments. The object of this research is to use lab instruments to find theeffects of Mars analog minerals on hydrogen peroxide gas releasetemperatures, specifically gas releases of water and oxygen andalso determine the effect of the peroxide on the minerals. Datathat we get from the lab can then be compared to the datacollected from Mars. The minerals hematite, siderite, San Carlos olivine, magnetite andnontronite were chosen as our Mars analog minerals. ~20 mg ofanalog Mars minerals with 5µl of 50% H O , and were either runimmediately or placed in a sealed tube for 2, 4, or 9 days to lookfor changes over time with two reps being done at each time stepto determine repeatability. Each sample was heated from -60 °Cto 500 °C at 20 °C/min and the evolved gases were monitoredwith a mass spectrometer. Each sample was also analyzed with anX-ray diffraction instrument to look for changes in mineralogy. Preliminary results show three potential outcomes: 1) peroxidehas no effect on the sample (e.g., hematite), 2) the mineral isunaffected but catalyzes peroxide decomposition (magnetite,siderite), or 3) peroxide alters the mineral (pyrrhotite, San Carlosolivine).

Author(s): Rudger H Dame , Paul Douglas Archer , JoannaC HogancampInstitution(s): 1. Brigham Young University, 2. GeocontrolsSystems Inc., 3. Jacobs

418.23 – Large Eddy Simulation of Dust Devils onMars Using MarsWRFLarge eddy simulations (LES) of convective cells and vortices inthe Martian convective boundary layer are performed employinga Mars version of the Weather Research and Forecasting model(WRF), adapted to use periodic boundary conditions. A windstress dust lifting scheme is used to determine dust lifting, andthe lifted dust is entrained into the vortices to form dust devils.Several cases are run at various locations in 1 deg x 1 deg domainsat horizontal resolutions of 100 to 300m. Surface albedo, thermalinertia and solar forcing are set uniform across the domain, usingvalues obtained from the MarsWRF General Circulation Model(GCM) at the same locations. This is for greater realism, and tofacilitate later comparison with planetary boundary layer (PBL)and dust devil predictions based on sub-grid scaleparameterizations in the GCM. An initial case with passive dust (no radiative response to the dustlifted) enables the tracking of dust in the vortices during theevolution of dust devils. The wind stress threshold that controlsdust particle lifting from the surface is tuned to make the columndust opacity match that of the MarsWRF GCM. The simulation isrun from 5 am to 6 pm to cover the whole Martian daytimeperiod. From 11 am, near-surface convection begins to growintensively due to the rapidly increasing solar heating, and dustdevils start to form. The dust height as well as the PBL heightreach the highest level in the afternoon. Another case withradiatively active dust is performed to investigate the feedback ofdust devils to the background atmosphere. Relationships between

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the size of convective cells, the number of dust devils, and thePBL height are also investigated. The LES results are thencompared with those of the GCM at the same location to evaluatethe existing PBL and dust devil parameterization schemes. Theinformation obtained in this work can be used to improve ourunderstanding of dust devils on Mars and to improveparameterizations used in the GCM.

Author(s): Zhaopeng Wu , Mark I. Richardson , Claire E.Newman , Xi ZhangInstitution(s): 1. Aeolis Research, 2. University of CaliforniaSanta Cruz

418.24 – A Numerical Study of Convection in aCondensing CO2 Atmosphere under Early Mars-Like ConditionsCloud convection of a CO atmosphere where the majorconstituent condenses is numerically investigated under a setupidealizing a possible warm atmosphere of early Mars, utilizing atwo-dimensional cloud-resolving model forced by a fixed coolingprofile as a substitute for a radiative process. The authorscompare two cases with different critical saturation ratios ascondensation criteria and also examine sensitivity to numbermixing ratio of condensed particles given externally. When supersaturation is not necessary for condensation, theentire horizontal domain above the condensation level iscontinuously covered by clouds irrespective of number mixingratio of condensed particles. Horizontal-mean cloud mass densitydecreases exponentially with height. The circulations below andabove the condensation level are dominated by dry cellularconvection and buoyancy waves, respectively. When 1.35 is adopted as the critical saturation ratio, cloudsappear exclusively as intense, short-lived, quasi-periodic events.Clouds start just above the condensation level and developupward, but intense updrafts exist only around the cloud top;they do not extend to the bottom of the condensation layer. Thecloud layer is rapidly warmed by latent heat during the cloudevents, and then the layer is slowly cooled by the specifiedthermal forcing, and supersaturation gradually develops leadingto the next cloud event. The periodic appearance of cloud events

does not occur when number mixing ratio of condensed particlesis large.

Author(s): Kensuke Nakajima , Tatsuya Yamashita ,Masatsugu Odaka , Ko-ichiro Sugiyama , Masaki Ishiwatari ,Seiya Nishizawa , Yoshiyuki O Takahashi , Yoshi-Yuki HayashiInstitution(s): 1. Department of Planetology, and Center forPlanetary Science, Kobe University, 2. Geodetic Department,Geospatial Information Authority of Japan, 3. Hokkaido Univ.Dept. Cosmosciences, 4. Kyushu Univ. Dept. Earth andPlanetary Sci., 5. National Institute of Technology, MatsueCollege, 6. RIKEN Advanced Institute for Computational Science

418.25 – Mars NanoOrbiter: A CubeSat for MarsSystem Science The Mars NanoOrbiter mission consists of two identical 12Uspacecraft, launched simultaneously as secondary payloads on alarger planetary mission launch, and deployed to Earth-escape, asearly as with Mars 2020. The nominal mission will last for 1 year,during which time the craft will independently navigate to Mars,enter into elliptical orbit, and achieve close flybys of Phobos andDeimos, obtaining unprecedented coverage of each moon. Thecraft will additionally provide high temporal resolution data ofMars clouds and atmospheric phenomena at multiple times ofday. Two spacecraft provide redundancy to reduce the risk inmeeting the science objectives at the Mars moons and enhancedcoverage of the dynamic Mars atmosphere. This technology isenabled by recent advances in CubeSat propulsion technology,attitude control systems, guidance, navigation and control.NanoOrbiter builds directly on the systems heritage of the MarCOmission, scheduled to launch with the 2018 Discovery missionInsight.

Author(s): Bethany Ehlmann , Andrew Klesh , TalalAlsedairyInstitution(s): 1. Caltech, 2. JPL, 3. KACST

419.01 – Collisional Cascades Following Triton'sCaptureNeptune's moon Triton is widely thought to have been capturedfrom heliocentric orbit, most likely through binary dissociation(Agnor and Hamilton, 2006). Triton's original eccentric orbitmust have been subsequently circularized by satellite tides(Goldreich et al. 1989). Cuk and Gladman (2005) found thatKozai oscillations make early tidal evolution inefficient, and haveproposed that collisions between Triton and debris from pre-existing satellites was the dominant mechanism of shrinkingTriton's large post-capture orbit. However, Cuk and Hamilton(DPS 2016), using numerical simulations and results of Stewartand Leinhardt (2012), have found that collisions between regularsatellites are unlikely to be destructive, while collisions betweenprograde moons and Triton are certainly erosive if notcatastrophic. An obvious outcome would be pre-existing moonmaterial gradually grinding down Triton and making it reaccretein the local Laplace plane, in conflict with Triton's large currentinclination. We propose that the crucial ingredient forunderstanding the early evolution of the Neptunian system arethe collisions between the moons and the prograde andretrograde debris originating from the pre-existing moons andTriton. In particular, we expect early erosive impact(s) on Tritonto generate debris that will, in subsequent collisions, disrupt theregular satellites. If the retrograde material were to dominate atsome planetocentric distances, the end result may be a large cloudor disk of retrograde debris that would be accreted by Triton,shrinking Triton's orbit. Some of the prograde debris couldsurvive in a compact disk interior to Triton's pericenter,eventually forming the inner moons of Neptune. We will presentresults of numerical modeling of these complex dynamicalprocesses at the meeting.

Author(s): Matija Cuk , Douglas P. Hamilton , Sarah T.Stewart-MukhopadhyayInstitution(s): 1. SETI Institute, 2. University of California, 3.University of Maryland

419.02 – Molecular diagnostics of FUV andaccretion-related heating in protoplanetary disksEmission lines from the terrestrial planet forming regions of disksare diagnostic of both the physical processes that heat the gas andthe chemistry that determines the inventory of nebular materialavailable during the epoch of planet formation. Interpretingemission spectra is informed by models of radiative, thermal,physical, and chemical processes, such as: (i) the radiationtransfer of X-rays and FUV --- both continuum and Ly-alpha, (ii)direct and indirect heating processes such as the photoelectriceffect and photochemical heating, (iii) heating related toturbulent processes and viscous dissipation, and (iv) gas phasechemical reaction kinetics. Many of these processes depend on athe spatial distribution of dust grains and their properties, whichtemporally evolve during the lifetime of the disk and theformation of planets. Studies of disks atmospheres often predict alayered structure of hot (a few thousand K) atomic gas overlyingwarm (a few hundred K) molecular gas, which is generallyconsistent with the isothermal slab emission models that are usedto interpret emission spectra. However, detailed comparisonbetween observed spectra and models (e.g., comparing the totalcolumns and the radial extent of warm emitting species) is rare. We present results including the implementation of Ly-alphascattering, which is an important part of the photochemicalheating and FUV heating radiation budget. By including theseprocesses we find a new component of the disk atmosphere; hotmolecular gas at ~2000K within radial distances of ~0.5AU,

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which is consistent with observations of UV-fluorescent H2emission (Ádámkovics, Najita & Glassgold, 2016). Constrainingthe most optimistic contribution of radiative heating mechanismsvia X-rays and FUV together with a favorable comparison toobservations, allows us to explore and evaluate additional heatingmechanisms. We find that the total columns of warm (90-400K)emitting molecules such as CO, arising directly below theirradiated molecular layer, are diagnostic of the role of turbulent(viscous) mechanical heating. We discuss how the total columnsof warm molecules in this layer may be diagnostic of themagnetorotational instability (Najita & Ádámkovics, 2017).

Author(s): Mate Adamkovics , Joan R. NajitaInstitution(s): 1. Clemson University, 2. National OpticalAstronomy Observatory

419.03 – Collisional Fragmentation Is Not a Barrierto Close-in Planet FormationCollisional fragmentation is shown to not be a barrier to rockyplanet formation at small distances from the host star. Simpleanalytic arguments demonstrate that rocky planet formation viacollisions of homogeneous gravity-dominated bodies is possibledown to distances of order the Roche radius. Extensive N-bodysimulations that include plausible models for fragmentation andmerging of gravity-dominated bodies confirm this conclusion anddemonstrate that rocky planet formation is possible for orbitsdown to about 1.1 times the Roche radius. At smaller distances,tidal effects cause collisions to be too fragmenting to allow massbuild-up to a final, dynamically stable planetary system. We arguethat even differentiated bodies can accumulate to form planets atdistances that are not much larger than the Roche radius.

Author(s): Joshua Wallace , Scott D. Tremaine , John E.ChambersInstitution(s): 1. Carnegie Inst. of Washington, 2. Institute forAdvanced Study, 3. Princeton University

419.04 – Collisional Mass Loss and Change ofVolatile Content in Planet FormationIt is widely accepted that the majority of Earth’s water wasdelivered to it by water carrying planetesimals and planetaryembryos from the outer part of the asteroid belt. Modern planetformation simulations show this process with high resolution, buttypically still treat embryo growth and water delivery in arudimentary way: perfect merging is assumed whenever acollision occurs. This neglects collisional loss of material –especially volatiles – and hence leads to planetary water contentsthat are far too high. Faced with the challenge of estimatingplanetary embryo growth and their water content with increasedaccuracy, we study typical collision scenarios from our previousn-body simulations. These scenarios differ in the masses of theinvolved planetary embryos, their water contents, the impactangles, and the collision speeds. We perform several suites ofdetailed simulations with our smooth particle hydrodynamics(SPH) collision code covering part of the mentioned parameterspace. We thrive for deriving a reasonable analytic estimate forcollisional mass loss and volatile transfer that can (a) be includedefficiently in planet formation simulations and (b) be used as apost-formation means to estimate realistic water budgets ofterrestrial planets. While more extensive parameter studies areneeded for deriving such a relation, we present first results validfor the simulated range of masses, velocities, and collision anglesand discuss their implications for models of terrestrial planetformation.

Author(s): Thomas I. Maindl , Nader Haghighipour ,Christoph Burger , David Bancelin , Christoph SchaeferInstitution(s): 1. Department of Astrophysics, University ofVienna, 2. Institut fuer Astronomie und Astrophysik,Universitaet Tuebingen, 3. Institute for Astronomy, Univ. ofHawaii

420.01 – New methods for deriving cometarysecular light curves: C/1995 O1 (Hale-Bopp)revisitedWe present an algorithm for reducing scatter and increasingprecision in a comet light curve. As a demonstration, weprocessed apparent magnitudes of comet Hale-Bopp from 16highly experienced observers (archived with the InternationalComet Quarterly), correcting for distance from Earth and phaseangle. Different observers tend to agree on the difference inmagnitudes of an object at different distances, but the magnitudereported by observer is shifted relative to that of another for anobject at a fixed distance. We estimated the shifts using a self-consistent statistical approach, leading to a sharper light curveand improving the precision of the measured slopes. The finalsecular lightcurve for comet Hale-Bopp ranges from -7 au (pre-perihelion) to +8 au (post-perihelion) and is the best secular lightcurve produced to date for this “great” comet. We discuss Hale-Bopp’s lightcurve evolution and possibly related physicalimplications, and potential usefulness of this light curve forcomparisons with other future bright comets. We also assess theappropriateness of using secular lightcurves to characterize dustproduction rates in Hale-Bopp and other dust-rich comets. M.W.acknowledges support from NSF grant AST-1615917.

Author(s): Maria Womack , Nathan Lastra , OlgaHarrington , Anthony Curtis , Kacper Wierzchos , NicholasRuffini , Mentzer Charles , David Rabson , Timothy Cox , IsabelRivera , Anthony MiccicheInstitution(s): 1. University of South Florida

420.02 – Chasing Manxes: Long-Period CometsWithout TailsA Manx is a minor body on a long-period comet orbit that isinactive or minimally active at small perihelion distances (wherewater would be expected to be strongly sublimating), resulting inthe lack of a significant tail. These objects are being discovered at

a rate of about a dozen per year from large all-sky surveys, andthe Pan-STARRS1 telescope in Hawai'i is the most prolific atdiscovering these weakly active objects. Manxes are theorized tobe planetesimals that formed in the inner solar system, perhapssome even in the Earth-forming region, that were subsequentlyejected out into the Oort cloud due to the migration of Jupiterand Saturn as the Solar System evolved. We use spectralreflectivities obtained with the Gemini North 8m telescope andESO's Very Large Telescope to determine the surface compositionof these objects. The observed Manxes exhibit a wide variety ofsurface properties, from primitive materials (i.e. C-, P- or D-types) to anhydrous materials (i.e. S-types). The relative numbersof objects with surface materials that are consistent withrelatively dry, rocky inner solar system material may be used toconstrain dynamical solar system formation models which makedifferent predictions about the amount and sources of materialthat gets ejected to the Oort cloud. To date, we have observed 27Manxes from 2013-2017. Here, we present preliminary resultsfrom this survey of spectral reflectivities for various Manxes. Inaddition, for some of the objects, we have sufficient heliocentricphotometry to model the activity in terms of water-icesublimation and can obtain estimates of the amount of near-surface water in comparison to comets. This work is supported inpart by an NSF award AST-1617015, and is based in part onobservations obtained at the Gemini Observatory acquiredthrough the Gemini Observatory Archive (GN2015A-FT18,GN2016A-Q15, GN2016A-FT22, GN2016B-Q19, GN-2016B-FT-24, GN-2017A-Q-14) and the European Organisation forAstronomical Research in the Southern Hemisphere under ESOprogrammes 098.C-0303 and 099.C-0787.

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Author(s): Haynes Stephens , Karen Jean Meech , JanKleyna , Jacqueline Keane , Olivier Hainaut , Bin Yang ,Richard J. Wainscoat , Marco Micheli , Bhuwan Bhatt ,Devendra SahuInstitution(s): 1. ESA SSA-NEO Coordination Centre, 2.European Southern Observatory, 3. Indian Institute ofAstrophysics, 4. University of California at Berkeley, 5.University of Hawaii

420.03 – Behavioral Characteristics and CO+COProduction Rates of Halley-Type Comets Observedby NEOWISEFrom the NEOWISE dataset of comet images, 11 different Halley-Type Comets (HTCs) were identified and analyzed for dustproduction rates (Afρ), CO+CO production rates (Q ), andnucleus size. The objects considered ranged in heliocentricdistance from 1.21 AU to 2.66 AU and were only considered whenshowing signs of reasonable activity. When multiple epochs wereincluded and when combined with data from previous WISE andNEOWISE studies, our dataset totaled to 21 observations; 13 ofwhich included active comets, and 7 for which we calculatedupper limits of production. Comet P/2010 JC81 was removedfrom consideration due to clear inactivity. For this study, activecomets are defined as those which exhibit excess signal of at least3σ in the 4.6 μm detection band, while comets for which upperlimits were calculated demonstrated excess signal of 1σ in the 4.6μm detection band. Furthermore, we confirmed the nucleus sizeof 27P, P/2006 HR30, C/2010 L5, P/2012 NJ, C/2016 S1. Wefound that given the range in heliocentric distance for this sampleof HTCs, Afρ ranged from 0.790 ± 0.036 to 2.64 ± 0.14, andQ ranged from 25.08 ± 0.08 to 26.71 ± 0.12. No significantcorrelation between dust production and heliocentric distance,nor CO+CO production with heliocentric distance was found forthis population. This poster will display production rates andother physical properties of these HTCs, as well as place theensemble of HTC production rate properties into context.

Author(s): Joshua David Rosser , James M. Bauer , Amy K.Mainzer , Emily A. Kramer , Joseph R. Masiero , CarrieNugent , Sarah M. Sonnett , Yanga R. Fernandez , Edward L.WrightInstitution(s): 1. IPAC/Caltech, 2. Jet Propulsion Laboratory,3. Planetary Science Institute, 4. University of California, 5.University of Central Florida, 6. University of RochesterContributing team(s): WISE, NEOWISE

420.04 – Radio observations of comets 41P/Tuttle–Giacobini–Kresák and 45P/Honda-Mrkos-Pajdušáková with the Green Bank TelescopeWe obtained 18cm OH spectra of comets 41P/Tuttle–Giacobini–Kresák (TGK) in early 2017 and 45P/Honda-Mrkos-Pajdušáková(HMP) in late 2016 and early 2017, using the Green BankObservatory 100m R. W. Byrd Green Bank Telescope (GBT).Spectra of both comets were obtained at 1667 and 1665 MHz(18cm wavelength) with a beam resolution of 7.4 arcminutes. Inspite of their close approaches to Earth, we only detected OHspectral lines with the telescope beam centered on the nucleus ofthe comets, so we are unable to make a direct constraint oncollisional quenching, but using estimated quenching, we canobtain estimates for gas production rates. Spectral line widthsand derived gas outflow velocities are low compared to othercomets at these heliocentric distances, particularly for HMP, withbest-fit water outflow velocities of 0.7-0.8 km/s at productionrates around 2 x 10 molecules per second. Best-fit velocities forTGK in mid-March, 2017 averaged 0.84 ± 0.04 km/s with gasproduction rates 1-2 x 10 molecules per second. In addition, weobtained Director's Discretionary Time to employ the ARGUSmapping spectrometer at 90 GHz (3mm) to constrain emissionsfrom HCN and HCO+. We will present gas outflow velocities foreach detection and gas production rates or upper limits, asderived from best fits of Monte Carlo simulations.

Author(s): Amy J. Lovell , Charlee Amason , Ellen S.Howell , Brynn A. Presler-Marshall , Sarah E. Reid , NicholCunningham , David T. Frayer , Felix J. Lockman , Sarah E.ChurchInstitution(s): 1. Agnes Scott College, 2. Green BankObservatory, 3. Lunar and Planetary Lab, University ofArizona, 4. Stanford University

421.01 – Analysis of cloud microphysical processeson extrasolar giant planet atmospheresWith an increasing rate of exoplanetary discovery, especiallyBrown dwarfs and Hot Jupiters, it is becoming necessary toprofile and characterize the atmospheres of these bodies. Transitspectroscopy plays a vital role in determining atmosphericcomposition, but the presence of cloud layers creates adegeneracy in the spectra, in that several features can beexplained equally well with cloudy and cloud-free atmospheres(e.g. Line and Parmentier, 2016). While equilibrium cloudcondensation models (ECCM) predict the presence of variouscondensable cloud layers, it is important to analyze theirdynamics and stability. This is a significant challenge, even with ageneral circulation model (GCM), as various characteristics of theatmosphere (e.g. abundance of condensable species) are difficultto obtain. We demonstrate a 1-dimensional microphysics modelfor condensable clouds with a focus on the rates of cloud growthand decay, which would allow us to diagnose the dynamics andstability of cloud formation on these exotic atmospheres. Wepresent an analysis of the timescales of microphysical processesof condensable clouds such as Fe and KCl, with attention to thosein Hot Jupiter atmospheres.

Author(s): Ramanakumar Sankar , Csaba J. PalotaiInstitution(s): 1. Florida Institute of Technology

421.02 – Searching for Exoplanets using ArtificialIntelligenceIn the last decade, over a million stars were monitored to detecttransiting planets. The large volume of data obtained fromcurrent and future missions (e.g. Kepler, K2, TESS and LSST)requires automated methods to detect the signature of a planet.Manual interpretation of potential exoplanet candidates is laborintensive and subject to human error, the results of which aredifficult to quantify. Here we present a new method of detectingexoplanet candidates in large planetary search projects which,unlike current methods uses a neural network. Neural networks,also called ``deep learning'' or ``deep nets'', are a state of the artmachine learning technique designed to give a computerperception into a specific problem by training it to recognizepatterns. Unlike past transit detection algorithms, the deep netlearns to characterize the data instead of relying on hand-codedmetrics that humans perceive as the most representative.Exoplanet transits have different shapes, as a result of, e.g. theplanet's and stellar atmosphere and transit geometry. Thus, asimple template does not suffice to capture the subtle details,especially if the signal is below the noise or strong systematics arepresent. Current false-positive rates from the Kepler data areestimated around 12.3% for Earth-like planets and there has beenno study of the false negative rates. It is therefore important toask how the properties of current algorithms exactly affect theresults of the Kepler mission and, future missions such as TESS,which flies next year. These uncertainties affect the fundamentalresearch derived from missions, such as the discovery of habitable

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planets, estimates of their occurrence rates and ourunderstanding about the nature and evolution of planetarysystems.

Author(s): Kyle Alexander Pearson , Leon Palafox , CaitlinAnn GriffithInstitution(s): 1. University of Arizona

421.03 – A Model of the Hα and Na TransmissionSpectrum of HD 189733bThe hot gas in the upper thermosphere of hot Jupiter sets theboundary condition for understanding the rate of gas escape.Among current detections, Hα and Na transmission spectrummay play an important role in understanding the conditions inthe planet's thermosphere. I present a detailed atmosphere modeland comparison of Hα and Na model transmission spectra to thedata, with the goal of constraining the temperature, particledensities and radiation field in the region where the absorptionline is formed. A hydrostatic atmosphere is constructed over the pressure range10 - 10 μbar. Ionization equilibrium and balance of heating andcooling processes are enforced at each level of the atmosphere.The Lyα radiation intensity is computed using a Monte-Carlocode which includes resonant scattering, as well as photondestruction. Both the incident stellar Lyα and internal sourcesdue to recombination cascade and collisional excitation areincluded. The atomic hydrogen level population is computedincluding both collisional and radiative transition rates. The model transmission spectra are in broad agreement with thedata. Excitation of the H(n=2) population is mainly by Lyαradiative excitation due to the large Lyα intensity. The density ofH(n=2) is nearly flat over two decades in pressure, and isoptically thick to Hα. Additional models computed for a range ofstellar Lyman continuum (LyC) flux suggest that the variability intransit depth may be due to the variability in the stellar LyC.

Since metal lines provide the dominant cooling of this part of theatmosphere, the atmosphere structure is sensitive to the densityof species such as Mg and Na which may themselves beconstrained by observations. Since the Hα and Na D lines havecomparable absorption depths, we argue that the center of the NaD lines are also formed in the atomic layer where the Hα line isformed.

Author(s): Chenliang Huang , Phil Arras , DuncanChristie , Zhi-Yun LiInstitution(s): 1. University of Florida, 2. University ofNavada, Las Vegas, 3. University of Virginia

421.04 – Mass Determination of Kepler-46b andKepler-46c from Transit Timing VariationsTransit Timing Variations (TTVs) are changes of planetary transittimes relative to a linear ephemeris. TTVs can be caused bygravitational perturbations on the transiting planet by otherplanets in the system. We use 16 quarters of the Kepler mission toconfirm that theTTVs of Kepler-46b, are produced by an outer,non trasiting planet Kepler-46c. Using a version of the symplecticintegrator SWIFT, adapted to calculate the mid-transit times ofKepler-46b, combined with the Bayesian inference algorithmMultiNest, we derive a set of 12 dynamical parameters for thesystem of two planets. We discuss the orbital configuration andstability of the planetary system, including the mass and densityof Kepler-46b.

Author(s): Ximena Beatriz Beatriz Saad Olivera , DavidNesvorny , David M. Kipping , Fernando Virgilio RoigInstitution(s): 1. Columbia University, 2. ObservatorioNacional, 3. Southwest Research Institute

422.01 – Detection of Mercury's Potassium TailGround-based observations of Mercury's exosphere bridge thegap between the MESSENGER and BepiColombo missions andprovide a broad counterpart to their in situ measurements. Herewe report the first detection of Mercury's potassium tail in bothemission lines of the D doublet. The sodium to potassiumabundance ratio at 5 planetary radii down-tail is approximately95, near the mid-point of a wide range of values that have beenquoted over the planet's disk. This is several times the Na/Kpresent in atmospheres of the Galilean satellites and more thanan order of magnitude above Mercury's usual analogue, theMoon. The observations confirm that Mercury's anomalouslyhigh Na/K ratios cannot be explained by differences in neutralloss rates. The width and structure of the Na and K tails iscomparable and both exhibit a persistent enhancement in theirnorthern lobe. We interpret this as a signature of Mercury's offsetmagnetosphere; the exosphere's source rates are locally enhancedat the southern surface, and sloshing from radiation pressure andgravity guides this population into the northern region of the tail.

Author(s): Carl Schmidt , Francois Leblanc , Luke Moore ,Thomas A. BidaInstitution(s): 1. Boston University, 2. LATMOS, 3. LowellObservatory

422.02 – Analysis of Venusian Atmospheric Two-Dimensional Winds and Features Using VenusExpress, Akatsuki, and Ground-Based ImagesWe investigate the horizontal dynamics of Venus’s atmosphere atcloud-top level. In particular, we focus on the atmosphericsuperrotation, in which the equatorial atmosphere rotates with aperiod of approximately 4-5 days (~60 times faster than the solidplanet). The superrotation’s forcing and maintenancemechanisms remain to be explained. Temporal evolution of thezonal (latitudinal direction) wind could reveal the transport ofenergy and momentum in/out of the equatorial region, andeventually shed light on mechanisms that maintain the Venusian

superrotation. As a first step, we characterize the zonal meanwind field of Venus between 2006 and 2013 in ultraviolet imagescaptured by the Venus Monitoring Camera (VMC) on board theESA Venus Express (VEX) spacecraft which observed Venus’ssouthern hemisphere. Our measurements show that, between2006 and 2013, the westward wind speed at mid- to equatoriallatitudes exhibit an increase of ~20 m/s; these results areconsistent with previous studies by Kouyama et al. 2013 andKhatuntsev et al. 2013. The meridional component of the windcould additionally help us characterize large-scale cloud featuresand their evolution that may be connected to such superrotation.We also conduct ground-based observations contemporaneouslywith JAXA’s Akatsuki orbiter at the 3.5 m Astrophysical ResearchConsortium (ARC) telescope at the Apache Point Observatory(APO) in Sunspot, NM to extend our temporal coverage topresent. Images we have captured at APO to date demonstratethat, even under unfavorable illumination, it is possible to seelarge features that could be used for large-scale feature trackingto be compared to images taken by Akatsuki. Our work has beensupported by the following grants: NASA PATM NNX14AK07G,NASA MUREP NNX15AQ03A, NSF AAG 1212216, and JAXA’sITYF Fellowship. Kouyama, T. et al (2013), J. Geophys. Res. Planets, 118, 37–46,doi:10.1029/2011JE004013. Khatuntsev et al. (2013), Icarus, 226, 140-158,doi:10.1016/j.icarus.2013.05.018

Author(s): Ryan M. McCabe , Jacob Gunnarson , Kunio M.Sayanagi , John J. Blalock , Javier Peralta , Candace L. Gray ,Kevin McGouldrick , Takeshi Imamura , Shigeto WatanabeInstitution(s): 1. Apache Point Observatory, 2. HamptonUniversity, 3. Hokkaido Information University, 4. ISAS, JAXA,5. LASP, University of Colorado

422.03 – Reconciling the Dawn–Dusk Asymmetryin Mercury’s Exosphere with the MicrometeoroidImpact Directionality

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Combining dynamical models of dust from Jupiter-family cometsand Halley-type comets, we demonstrate that the seasonalvariation of the dust/meteoroid environment at Mercury isresponsible for producing the dawn–dusk asymmetry inMercury’s exosphere observed by the MESSENGER spacecraft.Our latest models, calibrated recently from ground-based andspace-borne measurements, provide unprecedented statistics thatenable us to study the longitudinal and latitudinal distribution ofmeteoroids impacting Mercury’s surface. We predict that themicrometeoroid impact vaporization source is expected toundergo significant motion on Mercury’s surface toward thenightside during Mercury’s approach to aphelion and toward thedayside when the planet is approaching the Sun.

Author(s): Petr Pokorny , Menelaos Sarantos , DiegoJanchesInstitution(s): 1. NASA - GSFC, 2. The Catholic University ofAmerica

422.05 – Discovery of araneiforms outside of theSouth Polar Layered DepositsMars' south polar region is sculpted by the seasonal cycle offreezing and thawing of exposed carbon dioxide (CO ) ice. In theSouthern Spring, CO jets loft dust and dirt through cracks in thesublimating CO ice sheet to the surface where winds blow thematerial into the hundreds of thousands of dark fans observedfrom orbit. During this seasonal process, it is thought that theCO gas also exploits weaknesses in the surface below the icesheet to carve dendritic channels known as araneiforms. PlanetFour: Terrains (http://terrains.planetfour.org) is a citizen scienceproject enlisting the general public to review ~6 m/pixel

resolution Mars Reconnaissance Orbiter (MRO) Context Camera(CTX) subimages to identify: (1) araneiforms (including featureswith a central pit and radiating channels known as ‘spiders’); (2)erosional depressions, troughs, mesas, ridges, and quasi-circularpits characteristic of the South Polar Residual Cap (SPRC) whichwe collectively refer to as ‘Swiss cheese terrain’, and (3) craters. We provide an overview of Planet Four: Terrains and discuss thedistributions of our high confidence classic spider araneiformsand Swiss cheese terrain identifications in CTX images covering11% of the South polar regions at latitudes ≤ −75 degrees N.Previously spiders were reported as being confined to the SouthPolar Layered Deposits (SPLD). We present the firstidentification of araneiforms at locations outside of the SPLD anddiscuss the implications for the CO jet hypothesis. Acknowledgements: This work uses data generated via theZooniverse.org platform, development of which was supported bya Global Impact Award from Google, and by the Alfred P. SloanFoundation. We also thank the HIRSE and MRO Teams for theirhelp in scheduling and acquiring our requested observations.

Author(s): Megan E. Schwamb , K-Michael Aye , GannaPortyankina , Candice Hansen , Chris J. Lintott , CampbellAllen , Sarah Allen , Fred J. Calef , Simone Duca , AdamMcMaster , Grant R.M MillerInstitution(s): 1. Adler Planetarium, 2. Gemini Observatory, 3.JPL, 4. LASP, 5. Planetary Science Institute, 6. University ofOxford

500.01 – Narrow Circumstellar Debris Rings inYoung Systems: Evidence for Planetary FormationFrom Multiple Subcores?In the last few decades, a number of young debris disk systemshave been identified with extremely thin, but very bright, outercircumstellar rings composed of comet-like bodies at 75 - 200 AUfrom their parent stars (e.g. Fomalhaut, HR4796A, HD32297).Using remote observations of these systems (incl. the latest GPI,SPHERE, ALMA, and SpeX results), we show how the ringbrightnesses denote mass densification on planetesimal toplanetary mass scales. The narrowness of the rings, however,require dynamically cold, highly densified orbital populations, aswe can rule out other formation scenarios such as thin disksublimation fronts from the observations. Planetary accretionactivity, expected in such a population, would stir up thevelocities for any population to ~V of the nascent planet, sothat any accreting bodies must have Mass < M in order tohave V << V ~few km/sec. Yet more than Mworth of dust is found in these rings. The only apparent solutionto these issues is that multiple small bodies are coalescing inthese rings, and that these rings are sheparded into narrowstructures by the multiple bodies. This scenario agrees withIzidoro et al. 2015's argument that ice giant planet formationoccurs via multiple subcores. We also present evidence thatunlike Fomalhaut and HD32297, the HR4796A ring material isunusually red and devoltilized due to local thermal conditions, sothat rocky and not ice-rich planetary cores are being formedthere.

Author(s): Casey M. Lisse , Michael L. Sitko , MassimoMarengoInstitution(s): 1. Iowa State Univ., 2. Johns Hopkins Univ., 3.Univ. of Cincinnati

500.02 – On the Origin of Banded Structure inDusty Protoplanetary Discs: HL Tau and TW HyaWe present simulations of planet-planetesimal interactions thatcan reproduce major and minor banded structure in the HL Tauand TW Hya discs provided that small grains trace thedynamically cold planetesimal population. The consequences ofthe model and its limitations will be discussed. In particular, the

model requires that planetesimals form throughout the disc atearly times, that planetesimal-planetesimal collisions arepredominately among the cold population, and that pebbleaccretion leads to mass redistribution of the small grains ontoplanetesimals before the grains can undergo significant radialdrift. The meteortic record may suggest that a similar processoccurred in the Solar System. The model implies that grain sizedistributions inferred from submm/mm studies may reflect earlydebris processes rather than grain growth.

Author(s): Aaron C. BoleyInstitution(s): 1. The University of British Columbia

500.03 – Characterization of beta pic and its planetfrom Dome C, AntarcticaThe Beta Pictoris system is unique: It is a young (20Ma), verybright star, with a debris disk seen edge-on, and a directly imagedplanet, Beta Pic b. In addition, the planet, which has a probable18 years orbital period, is due to nearly transit in front of its starduring 2017. In 1981 a mysterious event has been invoked aspossibly due to the same planet transiting the star. The uniqueopportunity of this configuration led an international consortiumto follow the star photometrically and by radial velocimetry. I willpresent the observations conducted from the Concordia base,Antarctica with the ASTEP photometric telescope continuouslyfrom March to October 2017. The lightcurves of excellent qualityallow a clear determination of the pulsation frequencies of thestar (a Delta Scuti) and the possibility to detect signs of Beta Pic bor its perturbations of the disk, possible rings or large moons, andadditional planets. At the time of the presentation, theobservations will have just ended, enabling a complete analysis.

Author(s): Tristan Guillot , Djamel Mekarnia , Lyu Abe ,Abdelkrim Agabi , Francois-Xavier Schmider , Eric Chapellier ,Lionel BigotInstitution(s): 1. Obs. de La Cote D' AzurContributing team(s): ASTEP Team

500.04 – Dust production by collisional grindingduring Planetesimal-Driven Migration

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Many main-sequence stars are surrounded by optically thin disksof dust in the absence of any detectable gas (e.g. Su et al. 2006,Meyer et al. 2008). IR and sub-millimeter observations suggestthat most of the observed emission comes from grains with sizesbetween 1-100 microns. Since radiation forces are expected toremove these grains on timescales much shorter than the age ofthe parent stars (Backman & Parsce 1993, Wyatt 2008), it impliesthat some process is replenishing the dust, such as collisionalgrinding. The latter requires large impact velocities betweenplanetesimals, which can be achieved if large objects aredynamically exciting a disk of 1-10km planetesimals. Such debrisdisks could be hosting ongoing planet formation, and present apowerful tool to test planet formation theories. If a planet is embedded in a gas-free planetesimal disk, themutual gravitational interactions will force the planet to migrate(e.g. Fernandez & Ip 1984). Planetesimals situated along thedirection of migration can be trapped in mean motion resonances(MMRs) with the planet (Malhotra 1993, 1995, Hahn & Malholtra1999). Planetesimals trapped in such resonances will have theireccentricities pumped to large values as the planet continues tomigrate, thereby leading to energetic collisions and dustproduction (Wyatt 2003, Reche et al. 2008, Mustill & Wyatt2011). We have performed an extensive suite of simulations in which weexplore the likelihood that a given set of disk parameters (mass,surface density slope, number of planetesimals) can sustainplanetesimal-driven migration (PDM). We confirm the strongdependence on resolution found in previous works (e.g. Kirsch etal 2009), and find that an embryo to planetesimal mass ratio of400 is necessary to mitigate the effects of stochasticity, whichmay cause migration to stall and/or reverse. After havingidentified disks suitable for sustained PDM, we model theirevolution using LIPAD (Levison et al. 2012) taking into accountcollisional grinding. We will present results on the dust signaturesthat can be expected from such systems.

Author(s): Julien Salmon , Kevin J. Walsh , Harold F.LevisonInstitution(s): 1. Southwest Research Institute

500.05 – Evolution of migrating protoplanetsheated by pebble accretionWe study the interactions in a protoplanetary system consistingof a gas disk, a pebble disk and embedded low-mass protoplanets.The hydrodynamic simulations are performed using a new codebased on 2D FARGO (Masset 2000) which we callFARGO_THORIN (http://sirrah.troja.mff.cuni.cz/~chrenko/).The code treats the hydrodynamics of gas and pebbles within atwo-fluid approximation, accounts for the heating and coolingprocesses in the gaseous component (including heating due topebble accretion) and propagates the planets in 3D using a high-order integration scheme (IAS15; Rein & Spiegel 2015). Our aimis to investigate how pebble accretion alters the orbital evolutionof protoplanets undergoing Type-I migration.

First, we demonstrate that pebble accretion can heat the

protoplanets so that their luminosity induces the heating torque(Benítez-Llambay et al. 2015) and the hot-trail effect (Chrenko etal. 2017; Eklund & Masset 2017). The heating torque is alwayspositive and alters the migration rates and directions profoundly,thus changing the position of planet traps and deserts. The hot-trail effect, on the other hand, pumps the eccentricity of initiallycircular orbits up to e ~ h. After becoming eccentric, theprotoplanets exhibit reduced probability of resonant lockingduring the migration and moreover, their close encountersbecome more frequent and provide more opportunities forscattering or merger events. The mergers can be massive enoughto become giant planet cores. We discuss the importance of theexcited eccentricities and violent orbital evolution for theextrasolar planet population synthesis. Finally, we present anextended model with flux-mean opacities caused by a coupleddisk of coagulating dust grains with a realistic size distribution.The aim of this model is to constrain possible pathways ofmigrating planets towards the inner rim of the protoplanetarydisk.

Author(s): Ondrej Chrenko , Miroslav Broz , MichielLambrechtsInstitution(s): 1. Charles University, 2. OCA

500.06 – Insights into the Streaming Instability inProtoplanetary DisksThe streaming instability is a leading mechanism to concentrateparticles in protoplanetary disks, thereby triggering planetesimalformation. I will present recent analytical and numerical work onthe origin of the streaming instability and its robustness. Ourrecent analytic work examines the origin of, and relationshipbetween, a variety of drag-induced instabilities, including thestreaming instability as well as secular gravitational instabilities,a drag instability driven by self-gravity. We show that draginstabilities are powered by a specific phase relationship betweengas pressure and particle concentrations, which power theinstability via pressure work. This mechanism is analogous topulsating instabilities in stars. This mechanism differsqualitatively from other leading particle concentrationmechanisms in pressure bumps and vortices. Our recentnumerical work investigates the numerical robustness of non-linear particle clumping by the streaming instability, especiallywith regard to the location and boundary condition of verticalboundaries. We find that particle clumping is robust to thesechoices in boxes that are not too short. However, hydrodynamicactivity away from the particle-dominated midplane issignificantly affected by vertical boundary conditions. Thisactivity affects the observationally significant lofting of small dustgrains. We thus emphasize the need for larger scale simulationswhich connect disk surface layers, including outflowing winds, tothe planet-forming midplane.

Author(s): Andrew N Youdin , Min-Kai Lin , Rixin LiInstitution(s): 1. ASIAA, 2. University of Arizona

501.01 – Dynamics of rings around elongatedbodiesDense and narrow rings are encountered around small bodies likethe Centaur object Chariklo, and possibly Chiron. The rings andcentral bodies can be studied in great details thanks to stellaroccultations, which accuracies at the km-level. Here we presentnew results from three high-quality occultations by Charikloobserved in 2017. They provide new insights on the ring geometryand Chariklo's shape. Data are currently being analyzed, butpreliminary results are consistent with a triaxial model forChariklo, with semi-axes a>b>c, where (a-b) may reach values aslarge as 10-15 km, depending on the model.

Such large values induce a strong coupling between the body andan initial collisional debris disk from which the rings emerged.This coupling stems from Lindblad resonances between the ringparticle mean motion and Chariklo's spin rate. We find that the

resonances clear the corotation zone (estimated to lie at about 215km from Chariklo's center) in very short time scales (centuries)and pushes the material well beyond the 3/2 resonance - that liesat an estimated radius of 280 km, thus consistent with the radiusof Chariklo's main ring C1R, 390 km. Other cases will be examined in view of multi-chord stellaroccultations by Trans-Neptunian Objects successfully observed in2017, as they provide constraints for the presence of materialaround these bodies. Results and dynamical implications will bepresented. Part of this work has received funding from the EuropeanResearch Council under the European Community's H2020 2014-2020 ERC grant Agreement n°669416 "Lucky Star"

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Author(s): Bruno Sicardy , Rodrigo Leiva , Jose Luis Ortiz ,Pablo Santos Sanz , Stefan Renner , Maryame El Moutamid ,Diane Berard , Josselin Desmars , Erick Meza , Gustavo Rossi ,Felipe Braga-Ribas , Julio Camargo , Roberto Vieira-Martins ,Nicolas Morales , Rene Duffard , Francois Colas , LucieMaquet , Sylvain Bouley , Karl-Ludwig Bath , WolfgangBeisker , Jean-Luc Dauverge , Mike KretlowInstitution(s): 1. Ciel & Espace, 2. Cornell Univ. DptAstronomy, 3. GEOPS, Univ. Paris Sud, 4. IAA, 5. IOTA/ES, 6.Obs. Paris IMCCE, 7. Obs. Paris-LESIA & UPMC, 8.Observatorio Nacional and LINeA, 9. Univ. Lille 1Contributing team(s): Chariklo occultations Team, HaumeaOccultation Team

501.02 – The Centaur Chariklo and its rings systemfrom stellar occultations in 2017A stellar occultation in June 3, 2013 revealed the presence of adense ring system around the Centaur object (10199) Chariklo(Braga-Ribas et al., Nature 2014). Subsequent analysis ofoccultation data and long-term photometric variations indicatethat Chariklo's body is elongated (Leiva et al. 2017, submitted)and that the main ring exhibits significant longitudinal variationsof the radial width (Bérard et al. 2017, in press). We report threemulti-chord high-quality stellar occultation by Chariklo on April9, 2017 and June 22, 2017 from Namibia, and July 23 2017 fromSouth America. The analysis of this new data set is underway, butpreliminary results are consistent with triaxial ellipsoidal models.From this analysis we will: -present refined models for the size and shape of Chariklo's mainbody and evaluate the heights and slopes of its topographic features. -give constraints on the longitudinal width variations ofChariklo's rings and explore the possibility to obtain the rings apsidal precession rate. Chariklo's shape and topography have strong consequences onthe dynamics of the rings through Lindblad-type resonancesbetween mean motion of the ring particles and the spin of themain body, while the rings precession rate gives constraints onthe dynamical oblateness of the main body.

**Part of the research leading to these results has receivedfunding from the European Research Council under the EuropeanCommunity’s H2020 (2014-2020/ ERC Grant Agreement n669416 ”LUCKY STAR”).

Author(s): Rodrigo Leiva , Bruno Sicardy , Julio Camargo ,Jose Luis Ortiz , Diane Berard , Josselin DesmarsInstitution(s): 1. IAA, 2. Observatoire de Paris, 3. ObservatórioNacional/MCTICContributing team(s): Chariklo occultations Team, Rio Group,Lucky Star Occultation Team, Granada Occultation Team

501.03 – Long Live the Ring - A New Model for theEvolution of Chariklo's RingsWe propose a new evolutionary path for the rings of the CentaurChariklo, which were first reported by Braga-Ribas et al. (2014),and have enjoyed considerable study and debate ever since (see,e.g., Pan & Wu (2016), Wood et al. (2017), Michikoshi & Kokubo(2017), Hyodo et al. (2016), Araujo et al. (2016)). Despite thewide-ranging and sometimes contradictory conclusions of thesestudies, few challenge the expectation that the rings formed afterChariklo migrated to its current location from its original trans-Neptunian orbit, although Araujo et al. (2016) explicitly note thatthis need not be the case. This assumption is typically justified bynoting that the rings’ spreading timescale, which is believed to beas short as ~0.1 Myr (Pan & Wu 2016), is much shorter than ~10Myr, the expected average lifetime of a Centaur (Tiscareno &Malhotra 2003). Nevertheless, we argue, following the results of Hamilton et al.(2016) and Rimlinger et al. (2016), that these rings can self-confine under the right conditions, raising their spreadingtimescales by several orders of magnitude. Thus, we present anevolutionary path in which the rings formed before Chariklomigrated inward, possibly due to a collision with another trans-

Neptunian object (an idea briefly suggested by Melita et al. 2017).Perhaps more likely, the rings may have formed from the debrisresulting from a comet impact upon a small orbiting satellite.After forming, the rings reached a self-confining equilibrium andhave stayed there to this day. To test this theory, we employ the N body integrator HNBody(Rauch & Hamilton 2002), which was recently upgraded toperform simulations of self-gravitating, viscous rings orbiting anoblate spheroid (Rimlinger et al. 2017). For Chariklo, we searchthe parameter space of ring mass vs. viscosity strength forequilibria that remain stable for hundreds of millions or billionsof years. We will show examples of such equilibria and make thecase for long-lived rings around both Centaurs and Kuiper Beltobjects.

Author(s): Thomas Rimlinger , Douglas P. Hamilton ,Joseph M. HahnInstitution(s): 1. Space Science Institute, 2. University of MD,College Park

501.04 – Constraining the Formation of Haumeausing the Distribution of Haumea Family MembersCollisions are a central component of the formation and evolutionof the outer Solar System. The dwarf planet Haumea and itscompact collisional family provide a unique empirical view intohow collisions take place in the outer Solar System. Althoughthere have been many publications dedicated to understandingHaumea, there have yet to be any fully self-consistent models forthe formation of Haumea and its family. In particular, it is achallenge to explain why the relative velocities of family members("Delta v") is several times smaller than would be expected. Usinga much larger number of Haumea family members (see Maggard& Ragozzine, this meeting), we focus on finding the best empiricalmodel for the three-dimensional "Delta v" distribution of Haumeafamily members. We consider an isotropic ejection from Haumea,a planar ejection resulting from a graze and merge type impact(e.g., Leinhardt et al. 2010), and an isotropic ejection from asatellite of Haumea (e.g., Schlichting & Sari 2009). These modelscreate a large simulated family with tunable parameters thatresult in a unique distribution in a-e-i-Deltav-H space.Preliminary results indicated that the graze-and-merge impact isinconsistent with the observed distribution of family members(Ragozzine & Proudfoot, DDA 2017). We explore this morerigorously here by including tunable parameters, a Bayesianmethodology, and the influence of background interlopers.

Author(s): Benjamin Proudfoot , Darin RagozzineInstitution(s): 1. Brigham Young University

501.05 – Tracking an Exodus: Lost Children of theDwarf Planet HaumeaThe orbital properties of Kuiper Belt Objects (KBOs) refine ourunderstanding of the formation of the solar system. One object ofparticular interest is the dwarf planet Haumea which experienceda collision in the early stages of our solar system that ejectedshards form its surface and spread them over a localized part ofthe Kuiper Belt. Detailed orbital integrations are required todetermine the dynamical distances between family members, inthe form of "Delta v" as measured from conserved proper orbitalelements (Ragozzine & Brown 2007). In the past 10 years, thenumber of known KBOs has tripled; here, we perform dynamicalintegrations to triple the number of candidate Haumea familymembers. The resulting improved understanding of Haumea'sfamily will bring us closer to understanding its formation. Inorder to place more secure estimates on the dynamicalclassification of Haumea family members (and KBOs generally),we use OpenOrb to perform rigorous Bayesian uncertaintypropagation from observational uncertainty into orbital elementsand then into dynamical classifications. We will discuss ourmethodology, the new Haumea family members, and someimplications for the Haumea family.

Author(s): Steven Maggard , Darin RagozzineInstitution(s): 1. Brigham Young University

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502 – Unveiling Venus

501.06 – Testing Backwards Integration As AMethod Of Age-Determination for KBO FamiliesThe age of young asteroid collisional families is often determinedby using backwards n-body integration of the solar system. Thismethod is not used for discovering young asteroid families and islimited by the unpredictable influence of the Yarkovsky effect onindividual specific asteroids over time. Since these limitations arenot as important for objects in the Kuiper belt Marcus et al. 2011suggested that backwards integration could be used to discoverand characterize collisional families in the outer solar system.However, there are some minor effects that may be important toinclude in the integration to ensure a faithful reproduction of theactual solar system. We have created simulated families of KuiperBelt objects through a forwards integration of various objects withidentical starting locations and velocity distributions, based on

the Haumea family. After carrying this integration forwardsthrough ~4 Gyr, backwards integrations are used (1) toinvestigate which factors are of enough significance to requireinclusion in the integration (e.g., terrestrial planets, KBO self-gravity, putative Planet 9, etc.), (2) to test orbital elementclustering statistics and identify methods for assessing false alarmprobabilities, and (3) to compare the age estimates with theknown age of the simulated family to explore the viability ofbackwards integration for precise age estimates.

Author(s): Nathan Benfell , Darin RagozzineInstitution(s): 1. Brigham Young University

502.01 – Large stationary wave features appearingrepeatedly at the cloud top of VenusAt the first observation sequence after Akatsuki’s Venus orbiterre-insertion (VOI-R) on December 7, 2015, Akatsuki revealed anexistence of a large-scale “bow-shaped” feature staying at almostsame geographic location (above Aphrodite Terra) at the cloudtop level with the Longwave Infrared Camera (LIR) and UltraViolet Imager (UVI). It expanded ~10,000 km from south tonorth and bended to downstream side of the super-rotation ofVenus. A numerical calculation in Fukuhara et al. (2017)suggested that a gravity wave generated in the lower atmospherecan propagate upward to the cloud top and reproduce theobserved bow-shape structure. Because the wave can transportmomentum to the upper atmosphere which possibly deceleratesthe super-rotation, it is an interesting topic whether thestationary wave event is regular or just an occasional event. Formore than three Venus years, or four Venus solar days, Akatsukihas observed huge stationary wave features in LIR images againand again since the VOI-R. It has been confirmed that four high-altitude regions, east and west part of Aphrodite Terra, AtraRegio, and Beta Regio, accompany with the large stationaryfeatures. All four regions are located in lower latitudes (< 30°),while no clear stationary feature has been confirmed aboveMaxwell Mountain, which is the highest mountain but located ata high latitude (60°), indicating geographical and latitudinaldependencies of the generation of the stationary waves. Akatsukialso reveals the stationary features can be considered as "daily"phenomena in Venus atmosphere. At every timing when the fourhigh-altitude regions were passing afternoon region of Venus,huge stationary waves became clearer. On the other hand, whenthe high mountains were located around mid-night and morning,stationary features were much weaker than that in afternoon, orcannot be confirmed, indicating strong local time dependency ofthe appearance. Since lower latitude has more incident solar fluxand afternoon area experiences longer solar heating thanmorning area, the geographical and the local time dependenciesindicate that interaction between mountains and solar heating orsolar fixed atmospheric structure may cause the large-scalefeatures.

Author(s): Toru Kouyama , Takeshi Imamura , MakotoTaguchi , Tetsuya Fukuhara , Takao M. Sato , George LHashimoto , Masahiko Futaguchi , Mao Takamura , TakeruYamada , Takehiko Satoh , Masato NakamuraInstitution(s): 1. Japan Aerospace Exploration Agency, 2.National Institute of Advanced Industrial Science andTechnology, 3. Okayama University, 4. Rikkyo University, 5.Toho University, 6. University of TokyoContributing team(s): Akatsuki Science Team

502.02 – Limb darkening in Venus night-side diskas viewed from Akatsuki IR2Night-side hemisphere of Venus exhibits dark and bright regionsas a result of spatially inhomogeneous cloud opacity which isilluminated by infrared radiation from deeper atmosphere. The 2-μm camera (IR2) onboard Akatsuki, Japan's Venus ClimateOrbiter, is equipped with three narrow-band filters (1.735, 2.26,

and 2.32 μm) to image Venus night-side disk in well-knowntransparency windows of CO atmosphere (Allen and Crawford1984). In general, a cloud feature appears brightest when it is inthe disk center and becomes darker as the zenith angle ofemergent light increases. Such limb darkening was observed withGalileo/NIMS and mathematically approximated (Carlson et al.,1993). Limb-darkening correction helps to identify branches, in a1.74-μm vs. 2.3-μm radiances scatter plot, each of whichcorresponds to a group of aerosols with similar properties. Weanalyzed Akatsuki/IR2 images to characterize the limb darkeningfor three night-side filters. There is, however, contamination from the intense day-side diskblurred by IR2's point spread function (PSF). It is found thatinfrared light can be multiplly reflected within the Si substrate ofIR2 detector (1024x1024 pixels PtSi array), causing elongated tailin the actual PSF. We treated this in two different ways. One is tomathematically approximate the PSF (with a combination ofmodified Lorentz functions) and another is to differentiate 2.26-μm image from 2.32-μm image so that the blurred light patterncan directly be obtained. By comparing results from these twomethods, we are able to reasonablly clean up the night-sideimages and limb darkening is extracted. Physical interpretation oflimb darkening, as well as "true" time variations of cloudbrightness will be presented/discussed.

Author(s): Takehiko Satoh , Takashi Nakakushi , Takao M.Sato , George L HashimotoInstitution(s): 1. ISAS/JAXA, 2. Okayama University, 3.Wakayama University

502.03 – Sulfuric Acid Vapor in the Atmosphere ofVenus as Observed by the Venus Express RadioScience Experiment VeRaThe cloud deck within Venus' atmosphere, which covers the entireplanet between approx. 50 and 70 km altitude, consists mostly ofliquid and gaseous sulfuric acid. The gaseous part increasesstrongly just below the main clouds and builds an approx. 15 kmthick haze layer of H SO . This region is responsible for a strongabsorption of radio waves as seen in Mariner, Pioneer Venus,Magellan and Venera radio science observations. The amount ofH SO is derived from the observed absorption as a function ofaltitude and latitude. The radio science experiment VeRa onboardVenus Express probed the atmosphere of Venus between 2006and 2015 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. The orbit of the Venus Express spacecraftallowed to sound the atmosphere over a wide range of latitudesand local times providing a global picture of the sulfuric acidvapor distribution. We present absorptivity and H SO profilesderived from X-band signal attenuation for the time of the entireVenus Express mission. More than 600 H SO profiles show theglobal sulfuric acid vapor distribution covering the northern andsouthern hemisphere on the day- and night side of the planet. Adistinct latitudinal H SO gradient and a southern northernsymmetry are clearly visible. Observations over 8 years allow tostudy also long-term variations. Indications for temporal H SOvariations are found, at least at northern polar latitudes. Theresults shall be compared with observations retrieved by other

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503 – Origins of Planetary Systems II

experiments (VIRTIS, SPICAV) onboard Venus Express as well aswith previous observations like Mariner, Pioneer Venus and theMagellan spacecraft.

Author(s): Janusz Oschlisniok , Martin Pätzold , BerndHäusler , Silvia Tellmann , Michael Bird , Thomas AndertInstitution(s): 1. Institut für Raumfahrttechnik, Universitätder Bundeswehr München, 2. Rheinisches Institut fürUmweltforschung, Abteilung Planetenforschung, Universität zuKöln

502.04 – Airborne Measurements of Venus Cloud-top H O and HDO from NASA’s SOFIA in the Mid-InfraredThe determination of the D/H ratio in Venus’s atmosphere usingwater (H O) and light water (HDO) has been used as evidence forthe loss of a global sized ocean in the distant past on paleo-Venus.Measurements of atmospheric water vapour at and above thecloud level is also important as water is a key ingredient in theproduction of the hydrated H SO clouds that prevail globally onVenus. While variations in latitude and local solar time of H O atthe cloud tops has been most recently measured by ESA’s VenusExpress spacecraft, the data is sporadic due to the limb soundinggeometry needed to make these measurements.

Here we present H O and HDO measurements from January2017 from NASA’s Stratospheric Observatory for InfraredAstronomy (SOFIA) using the EXES mid-infrared spectrometerflying at 40,000 ft where the relatively low telluric absorptionmakes detection of Venusian H O possible. Two observationsequences were obtained that yielded spatially resolved maps ofH O and HDO at R~89,000 centered at 7.21 µm (1380 cm ). Wewill also discuss the preliminary retrieved values of D/H ratios atthe 65 km altitude probed at this wavelength.

Author(s): Constantine Tsang , Therese Encrenaz , CurtisN. DeWitt , Matthew Richter , Patrick IrwinInstitution(s): 1. NASA Ames Research Center, 2. Observatoirede Paris, 3. Southwest Research Institute, 4. University ofCalifornia at Davis, 5. University of Oxford

502.05 – The puzzling transition region of Venusatmosphere studied by a ground-to-thermosphere3D modelThe middle/upper atmosphere of Venus, notably between 70 and120 km, is the so-called “transition region” between theretrograde superrotating zonal flow dominating below 65 km, andthe day-to-night circulation created by inhomogeneous heating bysolar radiation above 120 km. Venus Express observations (2006-2014) showed that this region is more variable than expected,with latitude and day-to-day variations of temperature up to 80 Kabove 100 km at the terminator (Mahieux et al. 2015), andapparent zonal wind velocities measured around 96 km on theVenus nightime, highly changing in space and time (Soret et al.2014). Those variations are not fully explained by current 3Dmodels and specific processes (e.g. GW propagation, thermaltides, large scale planetary waves) responsible for driving themare still under investigation. We propose here to use the current improved version of the LMDVenus General Circulation Models (VGCM) (Lebonnois et al.2016, Gilli et al. 2017) to yield insight into the global circulation ofthis region by fostering data-model synergies. Zonal windpredictions above 60 km by our VGCM showed to be consistentwith available measurements (Peralta et al. 2017). On-goingground-based Venus observation on the cloud tops (~70 km) andbelow (Machado et al. 2017) will add complementary informationto understand the coupling between the lower and upperatmosphere of Venus. In addition, observed O ( Δ) nightglow,CO and O density (Gilli et al. 2015, Vandaele et al. 2016, Gerard etal. 2009), usually considered as sensitive transport tracers in theupper atmosphere of Venus where no direct wind measurementsare available, will be interpret with the help of 3D model results.

Author(s): Gabriella Gilli , Sebastien Lebonnois , PedroMachado , Ruben GonçalvesInstitution(s): 1. Institute of Astrophysics and Science Space,2. Laboratoire de Meteorologie Dynamique-IPSL

503.01D – Characterizing Debris Disks and theLate Stages of Planet FormationThe planet formation process shapes the morphology and grainsize distribution of circumstellar disks, encoding the formationhistory of a given system. Remnants of planet formation, such ascomets and asteroids, collisionally evolve and can replenish thedust and small solids that would otherwise be cleared on shorttimescales. These grains are observed through reprocessedstarlight at submm to cm wavelengths.

The spectrum of the mm/cm emission reveals details of the grainpopulation. However, one confounding parameter in studyingthese grains around stars is the stars themselves. The emissionfrom stars in the mm/cm is nontrivial and generally not well-constrained. I will present examples of debris systems (HD141569 and Fomalhaut) studied by ALMA and the VLA, in whichunconstrained stellar emission may be contributing to theobserved flux densities. Such contamination in turn biases theinferred emission from the disk and the corresponding dustproperties. In some cases, the behavior of the observed A/B starscan exhibit an emission profile that has similarities to that of theSun's mm/cm emission, although the same processes are notthought to necessarily occur in the atmospheres of massive stars.

To address the uncertainty in stellar emission at mm/cmwavelengths, we present ongoing radio observations (JCMT,SMA, VLA) of Sirius A, which is a bright, nearby star with noknown debris. We seek to use this system to set anobservationally determined standard for stellar atmospheremodeling and debris disk studies around A stars, as well as to takethe first step toward characterizing potential intrinsic uncertaintyin stellar emission at these wavelengths. This talk will highlight

the effort to characterize stellar atmospheres through a projectknown as MESAS (Measuring the Emission of StellarAtmospheres at Submillimeter/millimeter wavelengths) which isimperative to the success of current and future debris diskstudies.

Author(s): Jacob WhiteInstitution(s): 1. University of British Columbia

503.02D – Consequences of eccentricity andinclination damping for the in-situ formation ofSTIPsIn Boley, Granados, and Gladman (2016), we proposed that hotand warm Jupiters could form in-situ from the consolidation ofplanets in meta-stable, high-multiplicity System with Tightly-packed Inner Planets (STIPs) in the presence of gas. Under thishypothesis, the timing of instability within the STIP relative to thegas depletion timescale can lead to a wide range of planetarydiversity, from short-orbital period gas giants to high-density,massive planets. The simulations used Kepler-11 as a base andassumed that a gas giant could form if instability in the gaseousdisc led to the consolidation of a 10 Mearth core. The resultsshowed that such consolidation could work, in principle.However, in the simulations we excluded the effects ofeccentricity and inclination damping. We present newsimulations that explore this effect on the consolidationparadigm. For the parameters so far explored, gas dampingsignificantly increases the stability of the system, althoughconsolidation does occur in some cases. We further find that theeccentricity damping can lead to the formation of stable co-orbiting planets, although this is a rare outcome. Briefly, weexplore the implications of the detection of transiting co-orbitalplanets.

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504 – Centaurs and Kuiper Belt Objects: Physical Characterization

Author(s): Agueda Paula Granados ContrerasInstitution(s): 1. The University of British Columbia

504.01 – Overview of the strategies and results ofthe 2017 occultation campaigns involving (486958)2014 MU69Three stellar occultation opportunities were identified in 2017involving the New Horizons extended mission target: (486958)2014 MU69. The first event was on 2017 June 3 and predicted tobe visible from southern South America and southern Africa witha somewhat faint star with g’=15.33. The second event was on2017 June 10 under very difficult observing conditions just 16°from a full moon and the faintest star of the three with g’=15.57.The third event was on 2017 July 17 and predicted to be visiblefrom southern Argentina with the brightest star of the three withg’=12.60. We pursued each of these events with an observing planand strategy tuned to the constraints imposed by observingconditions and the anticipated prediction uncertainties. The firstand third events were amenable to a ground-based telescopedeployment and we fielded 25 telescopes. The second event waspossible only with SOFIA (Stratospheric Observatory For InfraredAstronomy). The deployment for the first event involved splittingresources between two continents and a strategy optimized toprevent a null result for a D=40km object. The second event wasoptimized for the search for dust and rings but had a 75% chanceof a solid body event for a D=40 km size. The third event wasdriven by needing to prevent a null result on a D=10 km size andproviding extra conservatism on the ground-track uncertaintywhile observing from the area of Comodoro Rivadavia, Argentina.All campaigns were successful in recording data essential for theconstraint on dust or rings around MU69: June 3, 24 lightcurves;July 10, 1 lightcurve; July 17, 23 lightcurves. Only the last eventwas able to record solid-body chords from the object with 5chords detected close to the predicted time and place. We willpresent an overview of the strategies and basic results of thecampaigns. This work would not have been possible without thefinancial support of the New Horizons mission and NASA,astrometric support of the Gaia mission, and logistical supportfrom Argentina and specifically Comodoro Rivadavia as well asassistance from the US Embassies in Buenos Aires and CapeTown.

Author(s): Marc W. Buie , Simon Bernard Porter , DirkTerrell , Peter Tamblyn , Anne J. Verbiscer , Alejandro Soto ,Lawrence H. Wasserman , Amanda Marie Zangari , Michael F.Skrutskie , Alex Parker , Eliot F. Young , Susan Benecchi , S.Alan Stern , New Horizons MU69 Occultation TeamInstitution(s): 1. Lowell Observatory, 2. Planetary ScienceInstitute, 3. Southwest Research Institute, 4. University ofVirginiaContributing team(s): New Horizons MU69 Occultation Team

504.02 – Ultra-High Resolution OrbitDetermination of (486958) 2014 MU69: Predictingan Occultation with 1% of an OrbitIn November 2015, the NASA New Horizons spacecraft burned itsthrusters to intercept the cold classical Kuiper Belt Object(486958) 2014 MU69. Then, on July 17, 2017, five smalltelescopes in Chubut Province, Argentina recorded a solid bodyoccultation of MU69. Both these events required an orbitalsolution of unprecedented accuracy, as will the January 1, 2019flyby of MU69 by New Horizons. This was especially difficultbecause there were no precoveries of MU69 prior to July 2014, itis in an extremely crowded field near the galactic core, and it isfaint enough to only be reliably detected by Hubble SpaceTelescope’s Wide Field Camera 3 (WFC3). To accomplish this, weperformed an extremely detailed analysis of 237 WFC3 images,down to the subpixel distortion level, in order to produceindividual probability distribution functions (PDFs) for theposition of MU69 in each WFC3 image. We registered each WFC3image against a pre-release version of the Gaia DR2 catalog,which produced even smaller residuals than the now-releasedDR1. We then combined these WFC3+Gaia PDFs with a high-

precision few-body numerical integrator and a Monte CarloMarkov Chain (MCMC) sampler to produce a state vector PDF forMU69 at defined epoch. Propagating those state vectors from theepoch produces an instantaneous positional cloud for MU69 atany given time. This positional cloud was then directly translatedinto a shadow path uncertainty cloud in order to plan the MU69occultation campaign. We will describe this process of fullypropagating errors from WFC3 images to telescope sites on theground, and also describe refinements for future guiding of NewHorizons to its encounter with MU69. We thank NASA, Hubble,Gaia, CONAE, the city of Comodoro Rivadavia, and thegovernment of Argentina for their assistance and support of theMU69 occultation campaign.

Author(s): Simon Bernard Porter , Marc W. Buie , John R.Spencer , William Folkner , Alex Parker , Amanda MarieZangari , Anne J. Verbiscer , Susan Benecchi , S. Alan Stern ,Dirk Terrell , Alejandro Soto , Peter Tamblyn , Lawrence H.Wasserman , Eliot F. YoungInstitution(s): 1. Jet Propulsion Laboratory, 2. LowellObservatory, 3. Planetary Science Institute, 4. SouthwestResearch Institute, 5. University of VirginiaContributing team(s): New Horizons MU69 Occultation Team

504.03 – A stellar occultation by (486958) 2014MU69: results from the 2017 July 17 portabletelescope campaignOn 2017 July 17, (486958) 2014 MU69 passed in front of a star asseen from the area north of Comodoro Rivadavia, in ChubutProvince, Argentina. Despite challenging wind conditions, twentytwo portable telescopes recorded data of the g'= 12.60 mag star ina 45-minute block centered on the predicted midtime of roughly03:50 UT. Each telescope was spaced approximately 4 km apartin a “picket fence” pattern to target an object as small as 10 km.The picket fence spanned roughly 100 km. Five telescopesobserved a solid body occultation. Occultation data provide a unique one-dimensional probe of the2014 MU69 system that is impossible to achieve from directimaging. These data will allow for fits of the size and shape of2014 MU69, and from its derived size, the albedo . Theoccultation data will also aid in navigation of NASA’s NewHorizons spacecraft toward its January 1, 2019 encounter with2014 MU69. We will detail the July 17 occultation campaign and presentanalyses of the light curves from each portable station, includingoccultation timing and constraints on dust and and other objectsin the system derived from the occultation baseline data. This work would not have been possible without the financialsupport of the New Horizons mission and NASA, astrometricsupport of the Gaia mission and HST, and logistical support fromArgentina, CONAE and specifically Comodoro Rivadavia as wellas assistance from the US Embassy in Buenos Aires.

Author(s): Amanda Marie Zangari , Marc W. Buie , S. AlanStern , Dirk Terrell , Simon Bernard Porter , Anne J.Verbiscer , Alejandro Soto , Peter Tamblyn , Susan Benecchi ,Alex Parker , Lawrence H. Wasserman , Eliot F. Young ,Michael F. SkrutskieInstitution(s): 1. Binary Astronomy LLC, 2. LowellObservatory, 3. PSI, 4. SwRI, 5. University of VirginiaContributing team(s): New Horizons MU69 OccultationObserving Team

504.04 – Multiplicity of the New HorizonsExtended Mission Target (486958) 2014 MU69New Horizons' extended mission target (486958) 2014 MU69 is asmall cold classical Kuiper Belt Object (KBO). Larger coldclassical KBOs are frequently found to host binary companions,

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but at small sizes the binary fraction is not well explored. Thepotential presence of multiple components in the 2014 MU69system presents an operational challenge to New Horizons, butadditional components would be of fantastic scientific value. Wewill compile all current observational and theoretical constraintson the multiplicity of 2014 MU69, including analysis of 2017stellar occultation data, direct imaging searches, lightcurveconstraints, and searches for barycentric motion in astrometricresiduals. Finally, we will describe the implications that anybinary components would have for the January 1, 2019 NewHorizons flyby and its scientific return.

Author(s): Alex Harrison Parker , Marc W. Buie , AmandaMarie Zangari , S. Alan Stern , John R. Spencer , Anne J.Verbiscer , Simon Bernard Porter , Susan BenecchiInstitution(s): 1. PSI, 2. Southwest Research Institute, 3.University of VirginiaContributing team(s): New Horizons MU69 Occultation Team

504.05 – Portable Telescopic Observations of the 3June 2017 Stellar Occultation by New HorizonsKuiper Extended Mission Target (486958) 2014MU69The New Horizons spacecraft will encounter the cold classicalKuiper Belt Object (486958) 2014 MU69 on 1 January 2019.Because it is extremely faint (V mag ~27), MU69 has only beendirectly observed by the Hubble Space Telescope since itsdiscovery (by HST) in 2014 (Spencer et al. 2015 EPSC 10, 417S).Current knowledge of the physical properties of MU69 istherefore limited to its red color (F606W-F814W = 0.99 ± 0.18,Benecchi et al. 2017) and a crude estimate on its size (20-40 km)based on association with other cold classical KBO visible albedos(0.04-0.15). Stellar occultations are powerful tools with which tomeasure the size and shape of objects whose distance andfaintness precludes any spatially resolved observations. Here wereport the results of a stellar occultation of a g’=15.33 magnitudestar by MU69 on 3 June 2017. The shadow path crossed bothsouthern Africa and South America. We deployed 12 portabletelescopes from Mendoza, Argentina and 13 portable telescopesfrom Clanwilliam, Western Cape, South Africa. Although 24 ofthese 25 telescopes successfully observed the occultation star atthe predicted event time, no solid body detection appeared in anyof the acquired lightcurves. Following the successful detection ofMU69 by stellar occultation on 17 July 2017, revised predictionsof the location of the shadow path on 3 June now allow thelightcurves obtained on 3 June to place important constraints onthe environment surrounding MU69 as well as upper limits onthe size of any small satellites in the regions probed. This workwould not have been possible without the financial support ofNASA, the New Horizons Project, the astrometric support of theGaia mission, and logistical support from the South AfricanAstronomical Observatory, the US Embassies in Buenos Aires andPretoria and the US Consulate in Cape Town.

Author(s): Anne J. Verbiscer , Marc W. Buie , SimonBernard Porter , Peter Tamblyn , Dirk Terrell , SusanBenecchi , Alex Parker , Alejandro Soto , Lawrence H.Wasserman , Eliot F. Young , Amanda Marie ZangariInstitution(s): 1. Lowell Observatory, 2. Planetary ScienceInstitute, 3. Southwest Research Institute, 4. University ofVirginiaContributing team(s): New Horizons MU69 Occultation Team

504.06 – Debris search around (486958) 2014MU69: Results from SOFIA and ground-basedoccultation campaignsThe New Horizons spacecraft is scheduled to fly by the coldclassical KBO 2014 MU69 on 1-Jan-2019. The spacecraft speedrelative to the MU69 will be in excess of 14 km/s. At theseencounter velocities, impact with debris could be fatal to thespacecraft. We report on searches for debris in the neighborhoodof MU69 conducted from SOFIA and ground-based sites. SOFIAobserved the star field around MU69 on 10-Jul-2017 (UT) withtheir Focal Plane Imager (FPI+), operating at 20 Hz from 7:25 to

8:10 UT, spanning the time of the predicted occultation. Severallarge fixed telescopes observed the 3-Jun-2017, 10-Jul-2017and/or the 17-Jul-2017 occultation events, including the 4-meterSOAR telescope, the 8-meter Gemini South telescope, and many16-inch portable telescopes that were arranged in picket fences inSouth Africa and Argentina. We report on the light curves fromthese observing platforms and constraints on the optical depthdue to debris or rings within the approximate Hill sphere (about60,000 km across) of MU69. This work was supported by theNew Horizons mission and NASA, with astrometric support fromthe Gaia mission and logistical support from Argentina and theUS embassies in Buenos Aires and CapeTown. At SOAR, dataacquisition has been done with a Raptor camera (visitorinstrument) funded by the Observatorio Nacional/MCTIC.

Author(s): Eliot F. Young , Marc W. Buie , Simon BernardPorter , Amanda Marie Zangari , S. Alan Stern , KimberlyEnnico , William T. Reach , Enrico Pfueller , ManuelWiedemann , Wesley Cristopher Fraser , Julio Camargo , LeslieYoung , Lawrence H. WassermanInstitution(s): 1. Deutsches SOFIA Institut, University ofStuttgart, 2. Lowell Observatory, 3. NASA/ARC, 4. ObservatorioNacional/MCTIC and LIneA, 5. Queen's University Belfast, 6.Southwest Research Inst., 7. USRAContributing team(s): New Horizons MU69 Occultation Team

504.07 – The HST Lightcurve of (486958) 2014MU To optimally plan the fly-by sequencing of (486958) 2014 MUfor the New Horizons spacecraft it is critical to determine, to thebest of our ability, if the object is binary (as is the case for ~20%of cold classical KBOs in this size range), the rotation period, sizeand shape of the body. Existing HST astrometric datasets placedconstraints on its diameter (21-41 km for an albedo of 0.15-0.04)and orbit, and early photometry suggested that a lightcurve withan amplitude of up to ~0.6 mags could be hidden within themeasurement uncertainties. However, the sampling interval ofthis dataset made it impossible to further refine those estimates.We therefore designed an HST lightcurve program to be executednear its opposition in July 2017 (GO 14627, PI Benecchi) when486958 would be brightest and provide the highest S/N data. Wecollected data using the WFC3 camera in the F350LP filter usingan exposure time of 367 seconds and tracking on the object. 5images were collected during each HST orbit and orbits werescheduled in groups of six. The 1st two sets of 6 orbits wereseparated by 0.6 days, the 2nd and 3rd by 1.4 days and the 3rdand 4th by 5.5 days. This allowed us to search for a range ofperiods from a few to a few tens of hours; combined with theastrometric photometry even longer periods can be investigated. The data were analyzed using two different PSF fitting techniques(an MCMC model and a TinyTim matching algorithm) which gavesimilar results. The lightcurve amplitude was found to be <0.15magnitudes for any period that we could fit to the data. Thisplaces significant constraints on the axis ratio of 486958 to <1.14assuming an equatorial view. This means that the timing of thefly-by does not need to be adjusted to look at the "larger" axis ofthe object, simplifying the engineering of the fly-by significantly.The small amplitude makes it difficult to uniquely identify therotation period at this time. Stacking all of the images from thiscampaign allows us to search for binary companions to a depth of>29th magnitude. At first analysis we do not identify anycompanions. This work was made possible through a STScI grantunder NASA contract NAS5-26555.

Author(s): Susan D. Benecchi , Marc W. Buie , SimonBernard Porter , John R. Spencer , Anne J. Verbiscer , S. AlanStern , Amanda Marie Zangari , Alex Parker , Keith S. NollInstitution(s): 1. NASA/GSFC, 2. Planetary Science Institute,3. Southwest Research Institute, 4. University of Virginia

504.08 – The stellar occultation by the dwarfplanet Haumea

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The dwarf planet Haumea is a very peculiar Trans-NeptunianObject (TNO) with unique and exotic characteristics. It iscurrently classified as one of the five dwarf planets of the solarsystem, and it is the only one for which size, shape, albedo,density and other basic properties were not accurately known. Tosolve that we predicted an occultation of the star GaiaDR11233009038221203584 by Haumea and organized observationswithin the expected shadow path. Medium/large telescopes wereneeded to record the occultation with enough signal to noise ratiobecause the occulted star is of similar brightness as Haumea(R~17.7 mag). We will report results derived from this successfulstellar occultation by Haumea on 2017 January 21st. Theoccultation was positive from 12 telescopes at 10 observingstations in Europe: the Asiago Observatory 1.8m telescope (Italy),the Mount Agliale Observatory 0.5m telescope (Italy), the LajaticoAstronomical Centre 0.5m telescope (Italy), the S.MarcelloPistoiese Observatory 0.6m telescope (Italy), the Crni VrhObservatory 0.6m telescope (Slovenia), the Ondrejov Observatory0.65m telescope (Czech Republic), the Bavarian PublicObservatory 0.81m telescope (Germany), the KonkolyObservatory 1m and 0.6m telescopes (Hungary), the SkalnatePleso Observatory 1.3m telescope (Slovakia), and the WendelsteinObservatory 2m and 0.4m telescopes (Germany). This is theoccultation by a TNO with the largest number of chords everrecorded.

Part of this work has received funding from the European Union’sHorizon 2020 Research and Innovation Programme under GrantAgreement No. 687378.

Author(s): Pablo Santos-Sanz , Jose Luis Ortiz , BrunoSicardy , Gustavo Rossi , Diane Berard , Nicolas Morales ,Rene Duffard , Felipe Braga-Ribas , Ulrich Hopp , ChristophRies , Valerio Nascimbeni , Francesco Marzari , ValentinaGranata , András Pál , Csaba Kiss , Theodor Pribulla ,Richard Milan Komzík , Kamil Hornoch , Petr Pravec , PaoloBacci , Martina Maestripieri , Luca Nerli , Leonardo Mazzei ,Mauro Bachini , Fabio Martinelli , Giacomo Succi , FabrizioCiabattari , Herman Mikuz , Albino Carbognani , BerndGaehrken , Stefano Mottola , Stephan Hellmich , FlaviaRommel , Estela Fernández-Valenzuela , Adriano CampoBagatinInstitution(s): 1. Astronomical Institute, Academy of Sciencesof the Czech Republic, 2. Astronomical Institute, Slovak Academyof Sciences, 3. Astronomical Observatory of the AutonomousRegion of the Aosta Valley (OAVdA), 4. AstronomicalObservatory San Marcello Pistoiese CARA Project, 5. BayerischeVolkssternwarte München, 6. Črni Vrh Observatory, 7.Departamento de Física, Ingeniería de Sistemas y Teoría de laSeñal, Universidad de Alicante, 8. Dipartimento di Fisica eAstronomia, `G. Galilei', Università degli Studi di Padova, 9.Dipartimento di Fisica, University of Padova, 10. FederalUniversity of Technology-Paraná (UTFPR / DAFIS), 11. GermanAerospace Center (DLR), 12. Instituto de Astrofísica deAndalucía-CSIC, 13. Konkoly Observatory, Research Centre forAstronomy and Earth Sciences, Hungarian Academy ofSciences, 14. Lajatico Astronomical Centre, 15. LESIA,Observatoire de Paris, PSL Research University, CNRS,Sorbonne Universités, UPMC Univ. Paris 06, Univ. ParisDiderot, Sorbonne Paris Cité, 16. Observatório Nacional/MCTIC,17. Osservatorio Astronomico di Monte Agliale, 18. Osservatorioastronomico di Tavolaia, 19. Universitäts-Sternwarte MünchenContributing team(s): Haumea occultation internationalcollaboration: https://cloud.iaa.csic.es/public.php?service=files&t=d9276f8ab1a316cef13bee28bef75add

504.09 – Stellar Occultations by TNOs andCentaurs: first results in the “Gaia era”After the first release of the GAIA catalog (in September/2016),stellar positions are now known with unprecedented accuracy,reaching values of the order of milliarcseconds. Thisimprovement reflected into a stunning accuracy on theastrometry of moving objects, such as TNOs. Unfortunately, Gaiastars proper motions will be only available on the second datarelease (DR2) next year, so there is still a need to use hybrid

stellar catalogs for occultation predictions until then. Despitethat, stellar occultations predictions are now much moreaccurate, and the biggest uncertainties comes mainly from theobject ephemerides. This issue will be overcome by large surveyssuch as the LSST, which will provide positions for the knownTNOs and it is expected to increase the number of known TNOsby nearly 40,000, with an unprecedent amount of acquiredinformation. This huge amount of data also poses a new era in stellaroccultations: predictions will be very accurate and theparticipation of professional astronomers, laboratories, and theamateur community will be crucial to observe the predictedevents; observation campaigns will need to be selected accordingto a specific scientific purpose such as the probability to detectrings or archs around a body, the presence of atmosphere or eventhe detection of topographic features; the development ofsoftwares capable of reducing the data more efficiently and aneasier method to coordinate observation campaigns are needed. Here we present some impressive results obtained frompredictions and observed occultations in 2017 (among them wehave Pluto, Chariklo and Haumea), the problems we are startingto face in the beginning of the “Gaia era” and the futurechallenges of stellar occultation.

Author(s): Gustavo Rossi , Roberto Vieira-Martins , BrunoSicardy , Jose Luis OrtizInstitution(s): 1. Instituto de Astrofísica de Andalucía (CSIC),2. Observatoire de Paris-Meudon, 3. Observatorio NacionalContributing team(s): Rio Group, Lucky Star OccultationTeam, Granada Occultation Team

504.10 – Spatially resolved thermal emission of theEris-Dysnomia systemHere we report on the detection of Dysnomia, the moon of thedwarf planet Eris, in ALMA band-7 observations, spatiallyseparated from the thermal emission of Eris. This is the firstdetection when a dwarf planet's moon is spatially resolved in thethermal emission from the ground, including infrared spacetelescopes close to Earth's orbit around the Sun. The ALMAmeasurements supplemented by far-infrared data from theHerschel Space Observatory confirms that the excess emissionobserved at 70-100um is due to the presence of a large(D~500km) and dark (pV~5%) Dysnomia, and very likely not dueto the existence of secondary dark terrains on the Eridian surface.Accordingly, the surface of Eris can be described with a veryhomogeneous, high albedo terrain, in agreement with both theoccultation size determination and the thermal emissionconstraints. Our results also highlight the great capabilities ofALMA in disentangling the thermal emission sources in the dwarfplanet systems.

Author(s): Csaba Kiss , Agnes Kospal , Attila Moor , AndrásPál , Anikó Farkas-Takács , Bernadett Ignácz , Thomas MüllerInstitution(s): 1. Max-Planck-Institut für extraterrestrischePhysik, 2. MTA CSFK, Konkoly Observatory

504.11 – Contact binaries in the Trans-neptunianBeltA contact binary is made up of two objects that are almosttouching or in contact with each other. These systems have beenfound in the Near-Earth Object population, the main belt ofasteroids, the Jupiter Trojans, the comet population and even inthe Trans-neptunian belt. Several studies suggest that up to 30% of the Trans-NeptunianObjects (TNOs) could be contact binaries (Sheppard & Jewitt2004, Lacerda 2011). Contact binaries are not resolvable with theHubble Space Telescope because of the small separation betweenthe system's components (Noll et al. 2008). Only lightcurves witha characteristic V-/U-shape at the minimum/maximum ofbrightness and a large amplitude can identify these contactbinaries. Despite an expected high fraction of contact binaries,2001 QG298 is the only confirmed contact binary in the Trans-Neptunian belt, and 2003 SQ317 is a candidate to this class ofsystems (Sheppard & Jewitt 2004, Lacerda et al. 2014).

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505 – Terrestrial Planets: Magnetospheres

Recently, using the Lowell’s 4.3m Discovery Channel Telescopeand the 6.5m Magellan Telescope, we started a search for contactbinaries at the edge of our Solar System. So far, our surveyfocused on about 40 objects in different dynamical groups of theTrans-Neptunian belt for sparse or complete lightcurves. Wereport the discovery of 5 new potential contact binariesconverting the current estimate of potential/confirmed contactbinaries to 7 objects. With one epoch of observations per object,we are not able to model in detail the systems, but we deriveestimate for basic information such as shape, size, density of bothobjects as well as the separation between the system’scomponents. In this work, we will present these new systems,their basic characteristics, and we will discuss the potential mainreservoir of contact binaries in the Trans-neptunian belt.

Author(s): Audrey Thirouin , Scott S. SheppardInstitution(s): 1. DTM-Carnegie Institution for Science, 2.Lowell Observatory

504.12 – Col-OSSOS: z Band Photometry RevealsThree Distinct TNO Surface TypesThe surface reflectance of trans-Neptunian object (TNO) surfacesin g, r, and z band provides a tool for separating TNOs into threesurface classifications: dynamically excited red surfaces,dynamically excited neutral surfaces, and red cold classicalsurfaces. Photometry of 26 TNOs obtained at Gemini and Subaru

Telescopes as part of the Colours of the Outer Solar SystemSurvey (Col-OSSOS) demonstrates that the inclusion of z banduniquely identifies cold classical surfaces. The dynamicallyexcited objects using this surface color combination areconsistent with two surface classes based on the two-componentmixing models of Fraser & Brown (2012). The reflectance of theneutral component of the models in g, r, and z band is consistentwith the speculation from that work that the neutral materialcontains silicates. Photometry in these three wavelenghtsprovides a powerful tool for identifying TNO surface types, and inparticular objects with cold classical-like surfaces. This toolenables the identification of dynamically hot interlopers in thecold classical population and primordially cold classical objects indynamically excited orbits.

Author(s): Rosemary E. Pike , Wesley Cristopher Fraser ,Megan E. Schwamb , J. J. Kavelaars , Michael Marsset , MicheleT Bannister , Matthew Lehner , Shiang-Yu Wang , MikeAlexandersen , Ying-Tung Chen , Brett Gladman , StephenGwyn , Jean-Marc Petit , Kathryn VolkInstitution(s): 1. Academia Sinica Institute of Astronomy andAstrophysics, 2. Gemini Observatory, 3. Institut UTINAM, 4.NRC Herzberg, 5. Queen's University Belfast, 6. University ofArizona, 7. University of British Columbia

505.01 – Venus Ionosphere and InducedMagnetosphere Responses to Solar Wind DynamicPressure and IMF DirectionIn this study, we focus on the responses of the ionosphere and theinduced magnetosphere of Venus to two typical changes in thesolar wind: solar wind dynamic pressure changes and theinterplanetary magnetic field (IMF) direction changes. Oftenregarded as the Earth’s ‘sister planet’, Venus has similar size andmass as Earth. But it is also remarkably different from Earth inmany respects. Even though we have some basic knowledge of thesolar wind interaction with Venus based on spacecraftobservations, little is known about how the interaction and theresulting plasma escape rates vary in response to solar windvariations due to the lack of coordinated observations of bothupstream solar wind conditions and simultaneous plasmaproperties in the Venus ionosphere. Furthermore, recentobservations suggest that plasma escape rates are significantlyenhanced during stormy space weather in response to solar windpressure pulses (Edberg et al., 2011). Thus it is important tounderstand the plasma interaction under varying solar windconditions. We use a sophisticated multi-species MHD model thathas been recently developed for Venus (Ma et al., 2013) tocharacterize the changes of the ionosphere and the inducedmagnetosphere for varying solar wind conditions. Based onmodel results, we discuss the perturbations of the magnetic fieldin the ionosphere and its variation with altitude; the variation ofthe total plasma escape-rate; and the time scale of the Venusionosphere and induced magnetosphere in responding to bothtypes of changes in the solar wind.

Author(s): Yingjuan Ma , Gabor Toth , Andew Nagy , ChrisRussellInstitution(s): 1. UCLA, 2. University of Michigan

505.02 – The complex magnetic field configurationof the Martian magnetotail as observed by MAVENThe Martian magnetosphere forms as the solar wind directlyinteracts with the planet’s upper atmosphere. During thisinteraction, the Sun’s interplanetary magnetic field (IMF) drapesaround the planet and local crustal magnetic fields, creating amagnetosphere configuration that has attributes of both aninduced magnetosphere like that of Venus, and a complex, small-scale magnetosphere like the Moon. In addition to the closedcrustal fields and draped IMF at Mars, open magnetic fields arecreated when magnetic reconnection occurs between theplanetary fields and the IMF. These various field topologies

present a complex magnetotail structure that we are now able toexplore using a combination of MAVEN observations andmagnetohydrodynamic (MHD) simulations. Preliminary MHDresults have suggested that the Martian magnetotail includes adual-lobe component, composed of open crustal fields, envelopedby an induced comet-like tail. These simulated open-field lobesare twisted by roughly 45°, either clockwise or counterclockwise,from the ecliptic plane. This rotation depends on the east-westcomponent of the IMF. We utilize MAVEN Magnetometer andSolar Wind Ion Analyzer (SWIA) measurements collected overtwo Earth years to analyze the tail magnetic field configuration asa function of IMF direction. Cross-tail views of the averagemeasured magnetic field components directed toward and awayfrom the planet are compared for a variety of solar windparameters. We find that, in agreement with simulation results,the east-west IMF component strongly affects the magnetotailstructure, twisting its sunward-antisunward polarity patterns inresponse to changing IMF orientation. Through a data-modelcomparison we are able to infer that regions of open magneticfields in the tail are likely reconnected crustal fields. Futhermore,these open fields in the tail may contribute to atmospheric escapeto space. From this investigation we are able to confirm that theMartian magnetotail is a hybrid configuration between intrinsicand induced magnetospheres, shifting the paradigm of Mars’magnetosphere as we have understood it thus far.

Author(s): Gina A DiBraccio , Janet Luhmann , ShannonCurry , Jared R. Espley , Jacob Gruesbeck , Shaosui Xu , DavidMitchell , Yasir Soobiah , John E.P. Connerney , ChuanfeiDong , Yuki Harada , Suranga Ruhunusiri , Jasper Halekas ,Takuya Hara , Yingjuan Ma , David Brain , Bruce JakoskyInstitution(s): 1. NASA GSFC, 2. Princeton Plasma PhysicsLaboratory, 3. The University of Iowa, 4. UC Berkeley, 5. UCLA,6. University of Colorado

505.03 – High-altitude closed magnetic loops atMars observed by MAVENWith electron and magnetic field data obtained by the MarsAtmosphere and Volatile EvolutioN (MAVEN) spacecraft, wehave identified closed magnetic field lines, with both footpointsembedded in the dayside ionosphere, extending up to 6200 kmaltitude (2.8 $R_m$) into the Martian tail. This topology isdeduced from photoelectrons produced in the dayside ionospherebeing observed in both parallel and anti-parallel directions alongthe magnetic field line. At perpendicular pitch angles, cases witheither solar wind electrons or photoelectrons have been found,indicative of different formation mechanisms of these closed

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506 – Extrasolar Planets and Systems: Discoveries and Dynamics

loops. These large closed loops are predicted by MHDsimulations. The case with field-aligned photoelectrons mixedwith perpendicular solar wind electrons is likely to be associatedwith reconnection, while the case with photoelectrons in alldirections are probably due to closed field lines being pulled backdown tail. We have developed an automated algorithm fordistinguishing photoelectrons from solar wind electrons in pitchangle resolved energy spectra. This allows us to systematicallyanalyze the MAVEN database and map the spatial distributionand occurrence rate of these closed magnetic loops, ranging froma few percent to a few tens percent outside of the optical shadowand less than one percent within the wake. These observations

can be used to investigate the general magnetic topology in thetail, which is relevant to ion escape, reconnection, and flux ropes.

Author(s): Shaosui Xu , David Mitchell , Janet Luhmann ,Yingjuan Ma , Xiaohua Fang , Yuki Harada , Takuya Hara ,David Brain , Tristan Webber , Christian Mazelle , Gina ADiBraccioInstitution(s): 1. Goddard Space Flight Center, 2. University ofCalifornia, Berkeley, 3. University of California, Los Angeles, 4.University of Colorado, Boulder, 5. University of Iowa, 6.University Paul Sabatier

506.01 – Orbital stability of compact three-planetssystems spaced non-uniformlyRecent discoveries unveiled a significant number of compactmulti-planetary systems, where the adjacent planets orbits aremuch closer to those found in the Solar System. For instance, therecently found system TRAPPIST-1 harbors seven planets allorbiting within 0.1 AU from their host star. Studying the orbitalstability of such compact systems provides how they form andhow long they survive. Most previous investigations of compactsystems have been done for planets that are equally-spaced interms of their mutual Hill radius. We performed a more generalstudy of three Earth-like planets orbiting a Sun-mass star incircular and coplanar prograde orbits. We first recover the resultsof previous studies done for systems of planets spaced uniformlyin mutual Hill radius. We have simulated over 500 systems withdifferent initial spacing between the adjacent inner pair of planetsand the outer pair of planets and we displayed their lifetime on agrid. We performed the simulations over a wide range of mutualHill radii. The simulations were conducted for virtual timesreaching at most 4 billion years. We characterize isochrones forlifetime of systems of equivalent spacing. We find that thestability time increases significantly for values of mutual Hill radiibeyond 8. We also study the affects of mean motion resonancesand the degree of symmetry in the grid.

Author(s): Sacha Gavino , Jack J. LissauerInstitution(s): 1. NASA Ames research Center, 2. Observatoirede Paris

506.02 – Effects of Dynamical Processes on theStructures of Sub-NeptunesThe typical low planet-star mass ratios, tight orbits, and lowaverage densities of sub-Neptunes, the dominant class of allknown exoplanets, make physical collisions extremely likely as aresult of dynamical instabilities in mult-planet systemsdiscovered by the Kepler mission. It is also abundantly clear thatthe masses of most known exoplanets are dominated by small,high-density cores, whereas, their sizes are dominated by low-density envelopes. Due to this unique core-envelope structure ofthese planets, physical collisions are not in the traditionally used`sticky-sphere' regime. Instead, a range of collision outcomes,such as `hit-and-run' and envelope disruption are allowed. Undercertain conditions, if the damping from the disrupted envelope(s)is sufficient, the cores can even become bound to each othercreating a binary planet. Similarly, due to the typically low massesin the atmospheres of these planets, planetesimal accretion, onlyby a few percent in mass, can lead to significant changes in theobservable average structural properties of these planets. We willpresent our latest results from planet-planet collision andplanetesimal accretion models to highlight these outcomes.

Author(s): Sourav Chatterjee , Jason Hwang , HowardChen , James C. Lombardi , Jason H. Steffen , Frederic A.RasioInstitution(s): 1. Allegheny College, 2. NorthwesternUniversity, 3. University of Nevada

506.03 – Differences Between Kepler's Near-Resonant and Non-Resonant Populations

The Kepler Space Telescope discovered over thousands of planetcandidates, ~1600 of which are in systems with multipletransiting exoplanets. The properties observed in these systemsgive decisive insight to the architectures of exoplanetary systems.The distribution of period ratios shows those at near-resonance tobe somewhat more common (Lissauer et al. 2011), which has beena source for theoretical discussion concerning planet formationand migration. Near-resonant pairs are also ideal for studyingTransit Timing Variations (TTV) and thereby obtaining mass anddensity estimates for planets. Understanding whether this near-resonant population is different from the non-resonantpopulation offers further insight to planetary architectures andwhether TTV planets are representative of the whole population.Previous investigations (Ragozzine & Conaway, DPS 2017) haveshown that the velocity-normalized duration ratio ("xi" fromLissauer et al. 2011) distribution is significantly different in thenear-resonant period ratio spikes compared to the non-resonantpairs. The xi distribution for Kepler’s entire planetary populationwas used by Fabrycky et al. 2014 to estimate the typicaleccentricity and inclination distributions, since these parametersare the primary determinants of the duration ratios. We usesimilar techniques to study the properties (eccentricities andinclinations) of the near-resonant population with the eventualgoal of creating a population model that, after accounting formeasurement uncertainties and Kepler’s detection criteria,reproduces all the properties of the period ratio and xidistributions.

Author(s): Neal Douglas Munson , Darin Ragozzine , EricB. Ford , Matthias Yang HeInstitution(s): 1. Brigham Young University, 2. PennsylvaniaState University

506.04 – Limits On Undetected Planets in the SixTransiting Planets Kepler-11 System The Kepler-11 has five inner planets ranging from ~ 2 - 10 timesas massive Earth in a tightly-packed configuration, with orbitalperiods between 10 and 47 days. A sixth planet, Kepler-11 g, witha period of 118 days, is also observed. The spacing betweenplanets Kepler-11 f and Kepler-11 g is wide enough to allow roomfor a planet to orbit stabily between them. We compare six andseven planet fits to measured transit timing variations (TTVs) ofthe six known planets. We find that in most cases an additionalplanet between Kepler-11 f and Kepler-11 g degrades rather thanenhances the fit to the TTV data, and where the fit is improved,the improvement provides no significant evidence of a planetbetween Kepler-11 f and Kepler-11 g. This implies that any planetin this region must be low in mass. We also provide constraintson undiscovered planets orbiting exterior to Kepler-11 g.

Author(s): Jack J. Lissauer , Daniel Jontof-Hutter , BrianWeaver , Eric B. Ford , Daniel FabryckyInstitution(s): 1. NASA Ames Research Center, 2.Pennsylvania State University, 3. University of Chicago, 4.University of the Pacific

506.05 – Leveraging the Thousands of KnownPlanets to Inform TESS Follow-Up

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507 – Mars: Lower Atmospheric Structure, Composition, and Circulation

The Solar System furnishes our most familiar planetaryarchitecture: many planets, orbiting nearly coplanar to oneanother. However, a typical system of planets in the Milky Wayorbits a much smaller M dwarf star, and these stars furnish adifferent blueprint in key ways than the conditions that nourishedevolution of life on Earth. With ensemble studies of hundreds-to-thousands of exoplanets, I will describe the emerging linksbetween planet formation from disks, orbital dynamics of planets,and the content and observability of planetary atmospheres.These quantities can be tied to observables even in discovery lightcurves, to enable judicious selection of follow-up targets from theground and from space. After TESS exoplanet discoveries start inearnest, the studies of individual planets with large, space-basedplatforms comprise the clear next step toward understanding thehospitability of the Milky Way to life. Our success hinges uponleveraging the many thousands of planet discoveries in hand todetermine how to use these precious and limited resources.

Author(s): Sarah BallardInstitution(s): 1. MIT

506.06 – Underlying Exoplanetary ArchitecturesInferred using SysSimKepler's discovery of ~700 multi-transiting systems has led torevolutionary advances in understanding planetary architectures(e.g., planetary spacings, relative sizes, etc.), particularly for smallplanets. However, precise understanding of the underlyingdistribution of planetary architectures requires accounting forcomplex detection biases and and geometric detection probabilityfor multi-planet systems. To account for Kepler's detectioncriteria, Hsu et al. 2017 expanded on work in Lissuaer et al. 2011to develop the Planetary System Simulator or "SysSim". SysSimuses generates planetary systems using general, empiricallyfocused parameters (in lieu of particular formation models). Toaccount for measurement uncertainties and Kepler's detectioncriteria, SysSim estimates which planets in which systems wouldhave been detected and compares the results to Kepler's finalDR25 catalog. The posterior distributions of the parameters areinferred using Approximate Bayesian Computation, a newtechnique that allows a Bayesian methodology to be applied tothis problem without defining a likelihood. Lissauer et al. 2011and others have found that using the observed multiplicitydistribution alone leads to a degeneracy between the true averagemultiplicity and the typical inclination distribution in planetarysystems. We use SysSim to show that we can break thisdegeneracy by including a constraint to match the period ratiodistribution. We discuss the new insights into the underlyingproperties of Kepler exoplanetary systems with implications forplanetary formation and evolution.

Author(s): Darin Ragozzine , Eric B. Ford , Danley Hsu ,Keir Ashby , Matthias Yang HeInstitution(s): 1. Brigham Young University, 2. PennsylvaniaState UniversityContributing team(s): Darin A Ragozzine

506.07 – Improving SysSim's Planetary OccurrenceRate EstimatesKepler's catalog of thousands of transiting planet candidatesenables statistical characterization of the underlying planetoccurrence rates as a function of period and radius. Due togeometric factors and general noise in measurements, we knowthat many planets--especially those with a small-radius and/orlong-period--were not observed by Kepler.To account for Kepler'sdetection criteria, Hsu et al. 2017 expanded on work in Lissuaer etal. 2011 to develop the Planetary System Simulator or "SysSim".SysSim uses a forward model to generate simulated catalogs ofexoplanet systems, determine which of those simulated planetswould have been seen by Kepler in the presence of uncertainties,and then compares those “observed planets” to those actuallyseen by Kepler. It then uses Approximate Bayesian Computationto infer the posterior probability distributions of the inputparameters used to generate the forward model. In Hsu et al.

2017, we focused on matching the observed frequency of planetsby solving for the underlying occurrence rate for each bin in a 2-dimensional grid of radius and period. After summarizing theresults of Hsu et al. 2017, we show new results that investigate theeffect on occurrence rates from including more accuratecompleteness products (from the Kepler DR25 analysis) intoSysSim.

Author(s): Keir Ashby , Darin Ragozzine , Danley Hsu , EricB. FordInstitution(s): 1. Brigham Young University, 2. PennsylvaniaState University

506.08 – Investigating Planet Formation andEvolution with KELT-11b: An Extremely InflatedPlanet Transiting a Metal-Rich Subgiant StarKELT-11b is a recently discovered transiting planet orbiting abright, metal-rich, subgiant star. The planet has a mass of just 0.2Jupiter masses and a radius of 1.4 Jupiter radii, making it one ofthe most inflated planets known to date. We will review thediscovery process for this unique exoplanet and presentobservations from the Spitzer Space Telescope that were used torefine the properties of the system. The high-precisionphotometry from Spitzer was also used to demonstrate theprecision with which we can measure stellar and planetaryparameters, when used in conjunction with to-be-released preciseparallax measurements from Gaia. Such measurements arecritical for detailed studies of exoplanets, such as our upcomingprogram to use the Hubble Space Telescope to study theatmosphere of KELT-11b via transmission spectroscopy. We willdescribe our upcoming Hubble program, which we anticipate willnot only provide one of the first water abundance measurementsfor a sub-Saturn-mass planet but will also probe the metallicity ofa planet with a metal-rich and evolved host star for the first time.We expect that the Hubble observations will enable meaningfulcomparison with objects in the Solar System as well as with theother few exoplanets known in the sub-Saturn population.Furthermore, such Hubble observations can be used to testpredictions from planet formation models of inflated exoplanets.With such unique attributes, the KELT-11 system is poised tobecome a benchmark for the study of inflated exoplanets aroundevolved stars.

Author(s): Knicole D. ColonInstitution(s): 1. NASA Goddard Space Flight CenterContributing team(s): KELT Collaboration

506.09D – A Secular Resonant Origin for theLoneliness of Hot JupitersThe origin of hot Jupiters, giant planets residing within about onetenth of an AU from their host stars, remains a long-standingproblem in exoplanetary science. Traditionally, these objects arethought to form further out, before migrating to their short-period orbits, though the possibility of an in-situ formationpathway has recently gathered theoretical support. A key clue totheir formation is their apparent "loneliness,” that all transitingexamples except one lack close-in, co-transiting planetarycompanions. In contrast, the slightly more distant "warm”Jupiters possess close-in planetary companions in about 50% ofcases. This dichotomy has led to the suggestion that two separateformation pathways are required to explain the two classes ofobjects. In this work we will demonstrate that the enhancedloneliness of hot Jupiters naturally arises owing to secularperturbations from the quadrupole moment of the host star soonafter dispersal of the protoplanetary disk. In this way, we placewarm Jupiters and hot Jupiters into a unified, theoreticalframework.

Author(s): Christopher Spalding , Konstantin BatyginInstitution(s): 1. California Institute of Technology

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507.01 – First measurements of water and D/H onMars with ExoMars / NOMADWe present preliminary data collected by the high-resolutionNOMAD (Nadir and Occultation for MArs Discovery) instrumentonboard the ExoMars / Trace Gas Orbiter (TGO) targeting severallines of water (H O), deuterated water (HDO) and carbon dioxide(CO ). TGO is the first spacecraft on Mars specifically tailored tosearch for trace constituents, with the NOMAD instrumentproviding high spectral resolution (λ/dλ~ 20,000) over the 2-5um spectral region. Such capabilities allow us to probe withunprecedented accuracy and sensitivity a multitude of organicspecies (e.g., CH , CH OH, H CO, C H ) and to map isotopicsignatures (e.g., D/H, C/ C) across the whole planet.

In particular, isotopic ratios are among the most valuableindicators for the loss of volatiles from an atmosphere. Becausethe escape rates for each isotope are slightly different (larger forthe lighter forms), over long times the atmosphere becomesenriched in the heavy isotopic forms. By probing the currentisotopic ratios, one can then infer the amount of matter lost tospace over the planet’s evolution. Deuterium fractionation alsoreveals information about the cycle of water on the planet andinforms us of its stability on short- and long-term scales,including its release from active regions on Mars having acharacteristic D/H signature.

Upon its successful launch in March/2016, we acquired criticalcalibration data in Apr/2016 and in June/2016, while during theMars-Orbit-Capture phase, we also acquired Mars nadir data inNov/2016 and in Feb-Mar/2017. Full science operations areexpected to start upon final orbit insertion in early 2018. In thispaper, we report initial retrievals of water and D/H derivedduring the Mars-Orbit-Capture phase and discuss the prospectsfor mapping of isotopic signatures during the nominal sciencephase.

Author(s): Geronimo Luis Villanueva , Giuliano Liuzzi ,Michael J. Mumma , Ann Carine Vandaele , Ian Thomas ,Michael D. Smith , Frank Daerden , Bojan Ristic , ManishPatel , Giancarlo Bellucci , Jose Lopez-MorenoInstitution(s): 1. American University, 2. Institut d'AeronomieSpatiale, 3. Instituto de Astrofisica de Andalucia, 4. Istituto diAstrofisica e Planetologia Spaziali, 5. NASA's GSFC, 6. OpenUniversityContributing team(s): NOMAD team

507.02 – New perspectives for studying organicsand the composition of Mars’ atmosphere withExoMars / NOMADThe ESA/Roscosmos Exomars Trace Gas Orbiter (TGO) missioncarries a series of instruments, whose operativity is aimed toachieve unprecedented accuracy in the detection andcharacterization of spatial distribution and temporal cycles of abroad set of trace species, organics and key isotopologues onMars. Besides this, the mission is designed for some other specificobjectives, such as the mapping of CH and D/H isotopologicratio.

In this work, we essentially focus on one of the key payloads ofExoMars, the Nadir and Occultation for Mars Discovery(NOMAD) instrument. This is a grating spectrometer whosedesign is based on that of the SPICAV/SOIR instrument, alreadyflown on board of Venus Express, and can operate both at theinfrared (IR) and visible/UV wavelengths. In addition, the IRchannel can be operated both in Solar Occultation (SO) mode,and in Limb Nadir Occultation (LNO), enabling the possibility ofa characterization of both the vertical structure of the atmosphereand the mapping of the above cited atmospheric compounds on aglobal scale.

To be prepared to exploit the outstanding possibilities and thehigh feasibility of the instrument to these science objectives, wehave worked on the calibration of the instrument both in SO andLNO modes. Using a large subset of the calibration

measurements acquired during the Mars Capture Orbit-1 phase(MCO-1), we have reckoned both the wavenumber calibrationacross all the spectral interval of the instrument, andcharacterized the response function of the Acousto-OpticalTunable Filter (AOTF) which selects diffraction orders. Theresults have been also used to elaborate a model of theinstrumental response, and a quantitative model of the observedsignal. Based on this, we also present some actual retrieval resultson SO and LNO datasets acquired in November 2016 and March2017, which will serve as a proxy for the forthcoming scienceoperations (starting early 2018). Acknowledgments NASA’s Mars Exploration Programsupported this work.

Author(s): Giuliano Liuzzi , Geronimo Luis Villanueva ,Michael J. Mumma , Ann Carine Vandaele , Ian Thomas ,Michael D. Smith , Frank Daerden , Bojan Ristic , ManishPatel , Giancarlo Bellucci , Jose Lopez-MorenoInstitution(s): 1. Belgian Institute for Space Aeronomy, BIRA-IASB, 2. IAPS-INAF, 3. Instituto de Astrofisica de Andalucia,IAA-CSIC, 4. NASA Goddard Space Flight Center, 5. The OpenUniversityContributing team(s): NOMAD team

507.03 – Spatial and Seasonal Variability ofTemperature in CO Emission from Mars'MesosphereWe have observed non-local thermodynamic equilibrium (non-LTE) emission of carbon dioxide that probes Mars’ mesosphere in2001, 2003, 2007, 2012, 2014, and 2016. These measurementswere conducted at 10.6 μm wavelength using the Goddard SpaceFlight Center Heterodyne Instrument for Planetary Winds andComposition (HIPWAC) from the NASA Infrared TelescopeFacility (IRTF) at resolving power (1–33)×10 . The Maxwellianbroadening of the emission line can be measured at thisresolution, providing a direct determination of temperature in themesosphere. The nonLTE line appears as a narrow emission corewithin a broad absorption formed by tropospheric CO , whichprovides temperature information reaching down to the martiansurface, while the mesospheric line probes temperature at about60-80 km altitude. We will report on the spatial distribution oftemperature and emission line strength with local solar time onMars, with latitude, as well as long-term variability includingseasonal effects that modify the overall thermal structure of theatmosphere. These remote measurements complement resultsfrom orbital spacecraft through access to a broad range of localsolar time on each occasion. This work has been supported by the NASA Planetary Astronomyand Solar Systems Observations Programs

Author(s): Timothy A. Livengood , Theodor Kostiuk , TilakHewagama , John R. Kolasinski , Wade Henning , KellyElizabeth Fast , Guido Sonnabend , Manuela SornigInstitution(s): 1. CRESST/GSFC, 2. DLR, 3. NASA, 4.NASA/GSFC, 5. Radiometer Physics

507.04 – Using an Instrumented Drone to SampleDust DevilsDust devils are low-pressure, small (many to tens of meters)convective vortices powered by surface heating and renderedvisible by lofted dust. Dust devils occur in arid climates on Earth,where they degrade air quality and pose a hazard to small aircraft.They also occur ubiquitously on Mars, where they may dominatethe supply of atmospheric dust. Since dust contributessignificantly to Mars’ atmospheric heat budget, dust devilsprobably play an important role in its climate. The dust-liftingcapacity of a devil likely depends sensitively on its structure,particularly the wind and pressure profiles, but the exactdependencies are poorly constrained. Thus, the exactcontribution to Mars’ atmosphere remains unresolved. Moreover,most previous studies of martian dust devils have relied onpassive sampling of the profiles via meteorology packages on

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landed spacecraft, resulting in random encounter geometrieswhich non-trivially skew the retrieved profiles. Analog studies ofterrestrial devils have employed more active sampling(instrumented vehicles or manned aircraft) but have been limitedto near-surface (few meters) or relatively high altitude (hundredsof meters) sampling. Unmanned aerial vehicles (UAVs) or drones,combined with miniature, digital instrumentation, promise anovel and uniquely powerful platform from which to sample dustdevils via (relatively) controlled geometries at a wide variety ofaltitudes. In this presentation, we will describe a pilot study usingan instrumented quadcopter on an active field site insoutheastern Oregon, which (to our knowledge) has notpreviously been surveyed for dust devils. We will presentpreliminary results from the resulting encounters, includingstereo image analysis and encounter footage collected onboardthe drone.

Author(s): Brian Jackson , Ralph Lorenz , Karan Davis ,Brock LippleInstitution(s): 1. Boise State University, 2. Empire Unmanned,3. Johns Hopkins University/Applied Physics Laboratory

507.05 – Realistic dust and water cycles in theMarsWRF GCM using coupled two-momentmicrophysicsDust and water ice aerosols significantly complicate the Martianclimate system because the evolution of the two aerosol fields iscoupled through microphysics and because both aerosols stronglyinteract with visible and thermal radiation. The combination ofstrong forcing feedback and coupling has led to various problemsin understanding and modeling of the Martian climate: inreconciling cloud abundances at different locations in theatmosphere, in generating a stable dust cycle, and in preventingnumerical instability within models.

Using a new microphysics model inside the MarsWRF GCM weshow that fully coupled simulations produce more realisticsimulation of the Martian climate system compared to a dry, dustonly simulations. In the coupled simulations, interannualvariability and intra-annual variability are increased, strong'solstitial pause' features are produced in both winter highlatitude regions, and dust storm seasons are more varied, withearly southern summer (Ls 180) dust storms and/or more thanone storm occurring in some seasons.

A new microphysics scheme was developed as a part of this workand has been included in the MarsWRF model. The scheme usessplit spectral/spatial size distribution numerics with adaptive binsizes to track particle size evolution. Significantly, this scheme ishighly accurate, numerically stable, and is capable of runningwith time steps commensurate with those of the parentatmospheric model.

Author(s): Christopher Lee , Mark Ian Richardson , MichaelA. Mischna , Claire E. NewmanInstitution(s): 1. Aeolis Research, 2. Jet PropulsionLaboratory, 3. University of Toronto

507.06 – Mars topographic clouds: MAVEN/IUVSobservations and LMD MGCM predictionsThe Imaging Ultraviolet Spectrograph (IUVS) instrument on theMars Atmosphere and Volatile EvolutioN (MAVEN) spacecrafttakes mid-UV spectral images of the Martian atmosphere. Fromthese apoapse disk images, information about clouds and aerosolscan be retrieved and comprise the only MAVEN observations oftopographic clouds and cloud morphologies. Measuring local timevariability of large-scale recurring cloud features is made possiblewith MAVEN’s ~4.5-hour elliptical orbit, something not possiblewith sun-synchronous orbits.

We have run the LMD MGCM (Mars global circulation model) at1° x 1° resolution to simulate water ice cloud formation withinputs consistent with observing parameters and Mars seasons.Topographic clouds are observed to form daily during the late

mornings of northern hemisphere spring and this phenomenonrecurs until late summer (Ls = 160°), after which topographicclouds wane in thickness. By northern fall, most topographicclouds cease to form except over Arsia Mons and Pavonis Mons,where clouds can still be observed. Our data show moderate cloudformation over these regions as late as Ls = 220°, somethingdifficult for the model to replicate. Previous studies have shownthat models have trouble simulating equatorial cloud thickness incombination with a realistic amount of water vapor and not-too-thick polar water ice clouds, implying aspects of the water cycleare not fully understood. We present data/model comparisons aswell as further refinements on parameter inputs based on IUVSobservations.

Author(s): Nicholas M. Schneider , Kyle Connour ,Francois Forget , Justin Deighan , Sonal Jain , Margaux Vals ,Michael J. Wolff , Michael S. Chaffin , Matteo Crismani , A. IanF. Stewart , William E. McClintock , Greg Holsclaw , FranckLefevre , Franck Montmessin , Arnaud Stiepen , Michael H.Stevens , J. Scott Evans , Roger Yelle , Daniel Lo , John T.Clarke , Bruce JakoskyInstitution(s): 1. Boston U., 2. CPI, 3. LASP, U. Colorado, 4.LATMOS, 5. LMD, 6. LPAP, U. Liege, 7. LPL, U. Arizona, 8. NRL,9. SSI

507.07 – Martian Mesoscale Flows overTopography Driven by the Diurnal Cycle ofTemperatureWe show results from limited area and global mesoscalesimulations for flow over regions of complex topographic relief onMars. We particularly focus on the diurnal evolution of thesurface pressure within such regions and isolate the differingcontributions of large-scale thermal tide and the various local-scale flow components. We use as examples sites over ApollinarisMons, Gusev Crater, Juventae Chasma, and Gale Crater – thelatter having detailed surface pressure measurements fromCuriosity against which the model can be tested. The sites showvarying amounts of constructive or destructive interferencebetween the thermal tides and local scale flows, with the signalsconsistently separable by use of lower resolution modeling, andspatial or spectral filtering. All of the regions of complex terrainshow a consistent pattern of surface pressure after the thermaltide has been removed, with surface pressure tending to increaseover areas of higher elevation at local times of highertemperature, and vice versa. The behavior is shown to be asexpected based on the adjustment of the atmosphere to thechanging scale height of the near surface atmosphere as the bulkair temperature varies through the day. The wind systemsassociated with this adjustment represent net lateral hydrostatic(mass redistributive) flow and can be large on Mars because thenear surface (~few km) air temperature can change dramaticallyover the course of the day. The hydrostatic adjustment flowinteracts with other topographic flow components, such as theslope sea breeze and buoyancy (gravity) flows that are morecommonly dominant in the terrestrial near-surface atmosphere.

Author(s): Mark I. Richardson , Claire E. NewmanInstitution(s): 1. Aeolis Research

507.08 – The Dusty Dynamics Within a RegionalMars Dust StormThere have never been in situ observations at or near the activelifting center of a regional dust storm on Mars. In the absence ofin situ data, it is common to employ numerical models to provideguidance on the physical processes and conditions operating in anunobserved location or weather system. Consequently, the MarsRegional Atmospheric Modeling System (MRAMS) is employed tostudy the structure and dynamics of a simulated large regionalstorm using a fully interactive dust cycle. The simulations providethe first ever glimpse of the conditions that might occur insideone of these storms. The simulated storm shows extremely complex structure withnarrow lifting centers and a variety of deep dust transport

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circulations. The active lifting centers are broadly into amesoscale system in much the same way that thunderstorms onEarth can organize into mesoscale convective structures. In manyof the active dusty plumes, the mixing ratio of dust peaks near thesurface and drops off with height. Once lifted, the largest dusttends to sediment out while the smaller dust continues to beadvected upward by the plume. This size-sorting processcombined with entrainment of less dusty air tends to drive themixing ratio profile to a maximum near the surface. In dustyplumes near the surface, the air temperature is as much as 20Kcolder than nearby areas. This is due to solar absorption higher inthe dust column limiting direct heating deeper into theatmosphere. Overall, within the plume, there is an inversion, andalthough the top of the plume is warmer than below, it is nearneutral buoyancy compared to the less dusty air on either side.Apparently, adiabatic cooling nearly offsets the expected positiveheating perturbation at the top of the dusty plume. A very stronglow level just forms in the vicinity of the storm, accompanied bysystem-wide negative pressure deficits and circulation patternsstrongly suggestive of the wind-enhanced interaction of radiationand dust (WEIRD) feedback mechanism.

Author(s): Scot C.R. Rafkin , Jorge Pla-Garcia , CeciliaLeungInstitution(s): 1. Centro de Astrobiología (CSIC-INTA), 2.SWRI, 3. University of Arizona Lunar and Planetary Institute

507.09D – Atmospheric modeling of Mars CHsubsurface clathrates releases mimicking SAM and2003 Earth-based detectionsThe aim of this work is to establish the amount of mixing duringall martian seasons to test whether CH releases inside or outsideof Gale crater are consistent with MSL-SAM observations. Severalmodeling scenarios were configured, including instantaneous andsteady releases, both inside and outside the crater. A simulationto mimic the 2003 Earth-based detections (Mumma et al. 2009

or M09) was also performed. In the instantaneous release insideGale experiments, Ls270 was shown to be the faster mixingseason when air within and outside the crater was well mixed: alltracer mass inside the crater is diluted after just 8 hours. Themixing of near surface crater air with the external environment inthe rest of the year is potentially rapid but slower than Ls270. Inthe instantaneous release outside Gale (NW) experiment, in just12 hours the CH that makes it to the MSL landing location isdiluted by six orders of magnitude. The timescale of mixing in themodel is on the order of 1 sol regardless of season. The durationof the CH peak observed by SAM is 100 sols. Therefore there is asteady release inside the crater, or there is a large magnitudesteady release outside the crater. In the steady release Galeexperiments, CH flux rate from ground is 1.8 kg m-2 s-1(Gloesener et al. 2017) and it is not predictive. In theseexperiments, ~200 times lower CH values detected by SAM aremodeled around MSL location. There are CH concentrationvariations of orders of magnitude depending on the hour, sotiming of SAM measurements is important. With a larger (butfurther away) outside crater release area compared to inside,similar CH values around MSL are modeled, so distance tosource is important. In the steady experiments mimicking M09detection release area, only 12 times lower CH values detectedby SAM are modeled around MSL. The highest value in the M09modeled scenario (0.6 ppbv) is reached in Ls270. This value is thehighest of all modeled experiments. With our initial conditions,SAM should not be able to detect CH , but if we multiply flux by12, increase the release area or move it closer to MSL (or all ofabove), it may be possible to get CH values that SAM coulddetect regardless where it comes from.

Author(s): Jorge Pla-GarciaInstitution(s): 1. Centro de Astrobiologia (CSIC-INTA,associated to NASA Astrobiology Institute)

508.01 – Continuing the investigation to tiltingUranus with a secular spin-orbit resonance

The most accepted hypothesis for the origin of Uranus’ 98°obliquity is one or more giant collisions during the late stages ofplanetary formation. Morbidelli et al. (2012) argue that twocollisions are needed to explain Uranus' satellites' progradeorbits. While this model is plausible, it does require impactors ofat least 0.3-1 Earth masses, depending on the quantity, to strikeclose to Uranus’ pole and induce a tilting. Even larger massimpactors would be required for more equatorial collisions. Herewe explore an alternative non-collision model to titling Uranus byusing a secular spin-orbit resonance between Uranus andNeptune during the earlier stages of planetary formation. Theinspiration for this model comes from a similar explanation ofSaturn’s non-negligible tilt, where a secular resonance betweenSaturn’s spin axis and Neptune’s orbital pole is responsible (Wardand Hamilton (2004) & Hamilton and Ward (2004)). Thommeset al. (1999, 2002, 2003) argue that at least the cores of Uranusand Neptune were formed in between Jupiter and Saturn, as thedensity of the protoplanetary disk was greater there.

If Neptune was scattered outward before Uranus, then a secularspin-orbit resonance between the two planets is possible. Themagnitude of this effect, however, may not be sufficient to driveUranus all the way to its current obliquity. A resonant kick, wherethe speed of the migrating planet is near the adiabatic limit, cantilt Uranus up to 40° in a reasonable timespan, and so couldreplace one of the impactors required in the collisional scenario ofMorbidelli et al. (2012). In most situations, however, the effect ofsuch a resonant kick is only of order 10°. We are now consideringvarious hybrid models that involve resonant captures and kicks asin Hamilton and Ward (2004), collisions and captures, andcollisions and kicks, and will report on our findings.

Author(s): Zeeve Rogoszinski , Douglas P. HamiltonInstitution(s): 1. University of Maryland

508.02 – Accurate Treatment of Collisions and Water-Delivery in Models of Terrestrial Planet FormationIt is widely accepted that collisions among solid bodies, ignited bytheir interactions with planetary embryos is the key process in theformation of terrestrial planets and transport of volatiles andchemical compounds to their accretion zones. Unfortunately, dueto computational complexities, these collisions are often treatedin a rudimentary way. Impacts are considered to be perfectlyinelastic and volatiles are considered to be fully transferred fromone object to the other. This perfect-merging assumption hasprofound effects on the mass and composition of final planetarybodies as it grossly overestimates the masses of these objects andthe amounts of volatiles and chemical elements transferred tothem. It also entirely neglects collisional-loss of volatiles (e.g.,water) and draws an unrealistic connection between theseproperties and the chemical structure of the protoplanetary disk(i.e., the location of their original carriers). We have developed anew and comprehensive methodology to simulate growth ofembryos to planetary bodies where we use a combination of SPHand N-body codes to accurately model collisions as well as thetransport/transfer of chemical compounds. Our methodologyaccounts for the loss of volatiles (e.g., ice sublimation) during theorbital evolution of their careers and accurately tracks theirtransfer from one body to another. Results of our simulationsshow that traditional N-body modeling of terrestrial planetformation overestimates the amount of the mass and watercontents of the final planets by over 60% implying that not onlythe amount of water they suggest is far from being realistic, smallplanets such as Mars can also form in these simulations whencollisions are treated properly. We will present details of ourmethodology and discuss its implications for terrestrial planetformation and water delivery to Earth.

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Author(s): Nader Haghighipour , Thomas Maindl ,Christoph SchaeferInstitution(s): 1. Univ. of Hawaii, 2. University of Tuebingen,3. University of Vienna

508.03 – Constraining the pre-impact orbits ofSolar System giant impactorsWe provide a fast method for computing constraints on impactorpre-impact orbits, applying this to the late giant impacts in theSolar System. These constraints can be used to make quick, broadcomparisons of different collision scenarios, identifying someimmediately as low-probability events and narrowing theparameter space in which to target follow-up studies withexpensive N-body simulations. We benchmark our parameterspace predictions, finding good agreement with existing N-bodystudies for the Moon. We suggest that high-velocity impactscenarios in the inner Solar System, including all currentlyproposed single-impact scenarios for the formation of Mercury,are low probability events, and favour a multiple hit-and-runscenario as the most probable currently proposed for theformation of Mercury.

Author(s): Alan Jackson , Travis SJ Gabriel , Erik AsphaugInstitution(s): 1. Arizona State University, 2. University ofToronto

508.04 – Mars’ Growth Stunted by an Early GiantPlanet InstabilityMany dynamical aspects of the solar system can be explained bythe outer planets experiencing a period of orbital instability.Though often correlated with a perceived delayed spike in thelunar cratering record known as the Late Heavy Bombardment(LHB), recent work suggests that this event may have occurredduring the epoch of terrestrial planet formation. Though currentsimulations of terrestrial accretion can reproduce many observedqualities of the solar system, replicating the small mass of Marsrequires modification to standard planet formation models. Herewe use direct numerical simulations to show that an earlyinstability in the outer solar system regularly yields properly sizedMars analogues. In 80% of simulations, we produce a Mars of theappropriate mass. Our most successful outcomes occur when theterrestrial planets evolve 10 million years (Myr), and accreteseveral Mars sized embryos in the Mars forming region before theinstability takes place. Mars is left behind as a stranded embryo,while the remainder of these bodies are either ejected from thesystem or scattered towards the inner solar system where theydeliver water to Earth. An early giant planet instability can thusreplicate both the inner and outer solar system in a single model.

Author(s): Matthew Clement , Nathan A. Kaib , Sean N.Raymond , Kevin J. WalshInstitution(s): 1. Laboratoire dAstrophysique de Bordeaux, 2.Southwest Research Institute, 3. University of Oklahoma

508.05 – Building the Moon from MultipleImpacts: Merger Efficiency and DynamicalConstraintsMost aspects of the Earth-Moon system can be explained by thesingle giant impact hypothesis, but such collisions are rarecompared to large impacts that produce smaller satellites. In themultiple-impact hypothesis, the Moon accretes from the mergersof several smaller satellites (moonlets), each formed from debrisdisks produced by successive impacts Myrs apart, a naturalconsequence of the Earth's growth through multiple impacts.Using N-body simulations, we assess the likelihood that pre-existing moonlets (which tidally migrate outward) remain stableduring subsequent impacts and merge with newly createdmoonlets. We find that the Earth likely had several previousmoons, many of which re-collided with the Earth. We also findthat the Moon could have formed from the mergers of severalmoonlets, which could explain the compositional similarity to theEarth. The stability of moonlets against disruption by subsequentimpacts also implies that several large impacts could post-dateMoon formation.

Author(s): Robert I. Citron , Hagai B. Perets , OdedAharonsonInstitution(s): 1. Israel Institute of Technology, 2. Universityof California, Berkeley, 3. Weizmann Institute of Science

508.06 – Boomerang SatellitesWe recently reported that the orbital architecture of the Martianenvironment allows for material in orbit around the planet to``cycle'' between orbiting the planet as a ring, or as coherentsatellites. Here we generalize our previous analysis to examineseveral factors that determine whether satellites accreting at theedge of planetary rings will cycle. In order for the orbitingmaterial to cycle, tidal evolution must decrease the semi-majoraxis of any accreting satellites. In some systems, the density of thering/satellite material, the surface mass density of the ring, thetidal parameters of the system, and the rotation rate of theprimary body contribute to a competition between resonant ringtorques and tidal dissipation that prevent this from occurring,either permanently or temporarily. Analyzing these criteria, weexamine various bodies in our solar system (such as Saturn,Uranus, and Eris) to identify systems where cycling may occur.We find that a ring-satellite cycle may give rise to the currentUranian ring-satellite system, and suggest that Miranda may haveformed from an early, more massive Uranian ring.

Author(s): Andrew Hesselbrock , David A. MintonInstitution(s): 1. Purdue University

508.07 – Dynamical shake-up and the low mass ofMarsThe low mass of Mars and the lack of planets in the asteroid beltare important constraints on theories of planet formation. Werevisit the idea that sweeping secular resonances involving the gasgiants and the Sun's dissipating protoplanetary disk can explain these features ofour Solar System. To test this "dynamical shake-up" scenario, weperform an extensive suite of simulations to track terrestrialplanet formation from planetesimals. We find that if the Sun’s gasdisk depletes in roughly a million years, then a sweepingresonance with Jupiter inhibits planet formation in the asteroidbelt and substantially limits the mass of Mars. We explore howthis phenomenon might lead to asteroid belt analogs aroundother stars with long-period, massive planets.

Author(s): Benjamin C. Bromley , Scott KenyonInstitution(s): 1. Smithsonian Astrophysical Observatory, 2.University of Utah

508.08 – Weakly Accreting Circumplanetary Disksand Satellites in Resonant OrbitsDuring the formation phase of gas giants, circumplanetarygaseous disks form around the planets. Circumplanetary disks areimportant not only for mass supply to gas giants but also forformation of regular satellites. The size-scale of circumplanetarydisks is smaller than that of protoplanetary disks and this makesmagnetic diffusion quicker. Thus, it is more difficult to sustain themagnetorotational instability (MRI) in circumplanetary disks. Inthe absence of significant angular momentum transport,continuous mass flow from the parental protoplanetary disk leadsto the formation of a massive circumplanetary disk. We havedeveloped an evolutionary disk model for this scenario and haveestimated the orbital evolution of moons within the disk. In acertain temperature range, we find that inward migration of asatellite can be stopped by a disk structure resulting from theopacity transitions. We also find that the second and thirdmigrating satellites can be captured in mean motion resonances.In this way, a compact system in Laplace resonance, which aresimilar to inner three bodies of Galilean satellites, can be formedin our disk models.

Author(s): Yuri I. Fujii , Hiroshi Kobayashi , Sanemichi Z.Takahashi , Oliver GresselInstitution(s): 1. Kogakuin University, 2. Nagoya University,3. Niels Bohr Institute

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508.09 – Mars’ peculiar formationThe formation of the terrestrial planets is a long standingproblem. Mars probably holds the key to solving this mysterybecause of the substantial amount of data gathered from spacemissions, martian meteorites and its obvious differences whencompared to Earth. Recent elemental and isotopic abundancessuggest that Mars’ composition is significantly different from thatof Earth. Therefore, Mars should have accreted most of its massin a region different from Earth’s, most likely further from theSun. These compositional differences should be explained withplanet formation models. We tested the probability of producing aMars analogue that is compositionally different from Earth in twopopular planet formation models: the Grand Tack model withtack locations of 1.5 or 2 AU for Jupiter; and the Classical modelin which all the terrestrial planets formed near their currentlocations. We performed a high number of N-body simulationswith initial conditions that are either equal-mass planetaryembryos or a semi-analytical approach to oligarch growth. Ourresults show that the probability of producing a Mars analoguewhich matches the current mass and orbit of Mars is at most 9%but reduces to mostly about 1% when it mainly accretes its massfurther than Mars’ current position of 1.5 AU. Strangely enough,in the Grand Tack model the number of Mars analogues producedis independent of the initial number of planet embryos. Hence,we conclude that both planet formation models have difficultiesto explain the observed compositional differences between Earthand Mars.

Author(s): Man Yin Woo , Ramon Brasser , StephenMojzsis , Soko Matsumura , Shigeru IdaInstitution(s): 1. Department of Geological Sciences,University of Colorado, 2. Earth Life Science Institute, TokyoInstitute of Technology, 3. School of Science and Engineering,Division of Physics, University of Dundee

508.10 – Planetesimal Sizes and Mars Formation inthe Magnetized Solar NebulaThe Hf-W chronology inferred from Martian meteorites suggeststhat Mars should be a stranded planetary embryo formed within avery short (about 2 Myr) accretion timescale. Previous studiesshow that such rapid growth can be realized when small (< 10 kmin size) planetesimals are accreted onto the embryo. Magnetizedchondrules found in Semarkona ordinary chondrite imply thatmagnetic fields and the resulting MHD turbulence played animportant role in nebular evolution. Under this circumstance,impact velocity of planetesimals can be very high due to nebulardensity fluctuations caused by turbulence, and hence collisionsbetween small planetesimals can become destructive, rather thanmergers. Here, we investigate how Mars formed in themagnetized solar nebula, focusing on MHD turbulence. Wedemonstrate what mass of planetesimals can contribute to Mars

formation and what value of the nebular mass is needed to satisfythe rapid accretion timescale. We therefore derive a more realisticcondition of the solar nebula under which Mars formation tookplace. While this study is based on the standard picture ofrunaway and oligarchic growth, we also discuss other formationmechanisms in order to compare how our results would beconsistent with the properties of the solar system. Thesemechanisms are a hypothesis that Mars formed from a narrowring of planetesimals, and the pebble accretion scenario.

Author(s): Yasuhiro Hasegawa , Ryuji MorishimaInstitution(s): 1. JPL/Caltech, 2. UCLA/JPL

508.11D – When Moons CollideImpacts between two orbiting satellites is a natural consequenceof Moon formation. Mergers between moonlets are especiallyimportant for the newly proposed multiple-impact hypothesis asthese moonlets formed from different debris disks merge togetherto form the final Moon. However, this process is relevant also forthe canonical giant impact, as previous work shows that multiplemoonlets are formed from the same debris disk. The dynamics of impacts between two orbiting bodies issubstantially different from previously heavily studied planetary-sized impacts. Firstly, the impact velocities are smaller andlimited to, thus heating is limited. Secondly, both fragments havesimilar mass therefore, they would contribute similarly andsubstantially to the final satellite. Thirdly, this process can bemore erosive than planetary impacts as the velocity of ejectedmaterial required to reach the mutual Hill sphere is smaller thanthe escape velocity, altering the merger efficiency. Previous simulations show that moonlets inherit differentisotopic signatures from their primordial debris disk, dependingon the parameters of the collision with the planet. We therefore,evaluate the degree of mixing in moonlet-moonlet collisions inthe presence of a planetary gravitational field, using SmoothParticle Hydrodynamics (SPH). Preliminary results show that theinitial thermal state of the colliding moonlets has only a minorinfluence on the amount of mixing, compared to the effects ofvelocity and impact angle over their likely ranges. For equal massbodies in accretionary collisions, impact angular momentumenhances mixing. In the hit-and-run regime, only small amountsof material are transferred between the bodies therefore mixing islimited. Overall, these impacts can impart enough energy to melt~15-30% of the mantle extending the magma ocean phase of thefinal Moon.

Author(s): Raluca Rufu , Oded AharonsonInstitution(s): 1. Weizmann Institute of Science

509.01 – The Mass Loss of Comet 67P/Churyumov-GerasimenkoThe Rosetta Radio Science Investigatios experiment (RSI)determined the mass and the degree and order two gravity field ofthe nucleus of comet 67P/Churyumov-Gerasimenko after arrivalin summer 2014 and again before the ultimate end of the missionin fall 2016. The comparison of the two mass values revealed asubstantial mass loss by gas and dust of about 10 million tons.The low bulk density of 533 kg/m3 and reasonable assumptionsof the compact dust material density implies a high porosity ofabout 75% and a high dust-to-ice mass ratio of the nucleus body.The ROSINA gas observations, however, integrated over themission time reveal a mass loss by the gas alone which does notallow a high dust-to-ice mass ratio for the material in spacebeyond a certain distance from the nucleus where the materialdoes no longer fall back to the nucleus. The dust-to-ice mass ratiomust be 0.3 in order to agree with the total mass loss determinedby RSI. Only a small amount of the lifted mass at an active spoton the surface reaches space. Most of the dust mass falls back andis redistributed on the surface.

Author(s): Martin Paetzold , Thomas Andert , Jean-PierreBarriot , Matthias Hahn , Michael Bird , Bernd Häusler , SilviaAnna TellmannInstitution(s): 1. Institut für Raumfahrttechnik undWeltraumnutzung, Universität der Bundeswehr München, 2.Rheinisches Instiut fuer Umweltforschung, DepartmentPlanetary Research, 3. Université Polynésie Francaise

509.02 – Detection of outbursts and modeling ofthe activity during the summer of 2015 withRosettaThe ESA (European Space Agency) Rosetta spacecraft waslaunched on March 2, 2004 and reached comet 67P/Churyumov-Gerasimenko (67P) in August 2014. Close to perihelion in August 2015, a display of outbursts on 67P,known as the summer fireworks (Vincent et al. 2016), wasobserved with the Optical, Spectroscopic, and Infrared RemoteImaging System (OSIRIS) and the NAVCAM. Vincent et al. (2016)reported the detection of 34 outbursts with one on average every2.4 nucleus rotations. In the case of the Microwave Instrument for the Rosetta Orbiter

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(MIRO), the most useful scan pattern for tracking gas abundancebefore, during, and after an outburst was a series of raster scansacross the nucleus along the comet-Sun direction. We identified aspectral feature that is indicative of high velocity gas movingtoward the spacecraft as being associated with outbursts. In thisparticular study, we will report the detection of 6 outbursts withMIRO during the summer of 2015. One of the outbursts detectedby MIRO was not observed with OSIRIS or the NAVCAM. We willpresent results for the gas production rate, as obtained from theH O emission line observed with MIRO and a numerical modelof the radiative transfer in the coma. Our goal is to better understand the physics of outbursts and howthe dust is lifted by the gas, by comparing model results toOSIRIS images (sensitive to the dust abundance) and MIROspectra (sensitive to the gas abundance and velocity). We used aCollisionless Gas Simulation tool developed at JPL to study thegas flow close to the nucleus and the dust trajectories asdetermined by the three main forces acting on the grains: thedrag force, gravity and the radiative pressure. Our main objectiveis to understand the mechanisms responsible for the outburst andthe activity. Past studies have shown that outbursts are in fact acombination of both gas and dust, in which the active surface atthe source of the outburst is believed to be approximately 10times more active than the average rate found in the surroundingareas (Gicquel et al. 2017). Preliminary results show that theactivity follows the insolation/illumination pattern.

Author(s): Adeline Gicquel , Paul von Allmen , MarkHofstadterInstitution(s): 1. JPL/CaltechContributing team(s): MIRO, OSIRIS

509.03 – Linking surface morphology, compositionand activity on the 67P/Churyumov-Gerasimenko’snucleusThe Rosetta mission orbited around the comet 67P/Churyumov-Gerasimenko for more than 2 years, getting an incredible amountof unique data of the comet nucleus and inner coma. This hasenabled us to study its activity continuously from 4 AU inboundto 3.6 AU outbound, including the perihelion passage at 1.25 AU. This work focuses on the identification of the regions sources offaint jets and outbursts, and on the study of theirspectrophotometric properties, from observations acquired withthe OSIRIS/NAC camera during the July-October 2015 period,i.e. close to perihelion. More than 150 jets of different intensitieswere identified directly on the nucleus from NAC color sequencesacquired in 7-11 filters covering the 250-1000 nm wavelengthrange, and their spectrophotometric properties studied for thefirst time. Some spectacular outbursts appear dominated by waterice particles, while fainter jets often show colors redder than thenucleus and appear dominated by dusty particles. Some jets arevery faint and were identified on the nucleus thanks to theunprecedented spatial and temporal resolution of theROSETTA/OSIRIS observations. Some of them have an extremelyshort lifetime, appearing on the cometary surface during the colorsequence observations, reaching their peak in flux and thenvanishing in less than a couple of minutes. We will present the results on the location, duration, and colors ofactive sources on the 67P nucleus from the relatively lowresolution (i.e. 6-10 m/pixel) images acquired close to theperihelion passage. Some of this active regions were observed andinvestigated in higher resolution (up to few dm per pixel) duringother phases of the mission. These observations allow us to studythe morphological and spectral evolution of the regions found tobe active and to further investigate the link between morphology,composition, and activity on cometary nuclei.

Author(s): Sonia Fornasier , Van Hong Hoang , Pedro H.Hasselmann , Maria Antonieta Barucci , Clement Feller ,Jasinghege Don Prasanna Deshapriya , Horst Uwe KellerInstitution(s): 1. DLR, 2. LESIA, Observatoire de Paris, PSLResearch University, CNRS, Univ. Paris Diderot, Sorbonne ParisCite', UPMC Univ. Paris 06, Sorbonne UniversitesContributing team(s): OSIRIS Team

509.04 – Spatial and Temporal Variations ofAtomic Species in the Coma of Comet67P/Churyumov-Gerasimenko as Observed byRosetta’s ALICE UV Spectrograph during GreatCircle ScansThe Alice far-ultraviolet (FUV) imaging spectrograph on theRosetta orbiter obtained spatially resolved spectra of67P/Churyumov-Gerasimenko (67P) from 700-2050 Å with aspectral resolution of 8-12 Å. Observations of 67P were obtainedby Alice continually from arrival at the comet in August 2014through the end of the mission in September 2016. “Great Circle”observations were performed every few weeks from January 2015through May 2016 to survey the coma away from the nucleus.These sequences consisted of a series of slews along a celestialgreat circle passing through the nucleus, e.g., covering off-nadirangles from approximately 0-180°, with pauses for observationsby Alice and other instruments. Alice’s line of sight during thesescans included signal to the edge of the coma, thus sampling verydifferent parts of the coma than most other instruments. We report here on observations acquired during these GreatCircle scans that allow us to investigate the spatial distributions ofvarious emissions, as well as seasonal variations in the comacomposition. Bright lines consistently included H Ly-b, the OItriplet near 1304 Å, CI near 1657 Å, and the SI triplet near 1820 Å.Spatial distributions of the OI, CI, and SI brightnesses have beendetermined and are being fitted with Haser models. The processis more complicated than for traditional remote sensing FUVobservations due to Rosetta’s location in the coma and becauseresonant scattering does not always dominate the excitation.Preliminary modeling yields H O and CO production ratesconsistent with contemporaneous measurements obtained byother instruments on Rosetta and production rates that generallypeak a few weeks after perihelion. A surprising phenomenon is aslight increase in OI brightness at large off-nadir angles for someGreat Circles while the other measured emissions continue todecrease. We are investigating possible explanations. Rosetta is an ESA mission with contributions from its memberstates and NASA. The Alice team acknowledges continuingsupport from NASA’s Jet Propulsion Laboratory through contract1336850 to the Southwest Research Institute.

Author(s): Matthew M. Knight , Harold A Weaver , RonaldJ. Vervack , Michael A'Hearn , Jean-Loup Bertaux , Lori M.Feaga , Paul D. Feldman , Joel Wm. Parker , Eric Schindhelm ,Andrew J Steffl , S. Alan Stern , Andre Bieler , Michael R.Combi , Nicolas Fougere , Brian A. Keeney , RichardMedina , John Noonan , Jon Pineau , Maarten H. VersteegInstitution(s): 1. JHU-Applied Physics Laboratory, 2. JohnsHopkins University, 3. LATMOS, 4. Lunar and PlanetaryLaboratory, 5. Southwest Research Institute, 6. SouthwestResearch Institute, 7. Stellar Solutions, 8. University ofColorado, 9. University of Maryland, 10. University of Michigan

509.05 – Analysis of the ROSINA/COPS end-of-mission measurements of the coma of comet67P/Churyumov–GerasimenkoA cometary coma is a unique phenomenon in the Solar systemthat represents an example of a planetary atmosphere influencedby little or no gravity. Due to the negligible gravity of a comet’snucleus, a coma has a characteristic size that exceeds that of thenucleus itself by many orders of magnitude. An extended dustygas cloud that forms a coma is affected mainly by molecularcollisions, radiative cooling, and photolytic, charge-exchange, andimpact-ionization reactions. Such an environment has been extensively observed during therecent Rosetta mission, which was the first mission that escorts acomet along its way through the Solar system for an extendedamount of time with the main scientific objectives ofcharacterizing comet’s nucleus, determining the surfacecomposition, and studying the comet’s activity development.

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The ROSINA (Rosetta Orbiter Spectrometer for Ion and NeutralAnalysis) Comet Pressure Sensor (COPS) onboard the Rosettaspacecraft has performed one of the most exciting observations ofthe innermost coma during the spacecraft descend maneuverduring the last ten hours of the mission when the random andoutflow directed pressures in the coma have been measured allthe way down to the comet’s surface. Performed at such closeproximity to the nucleus, these observations can help tocharacterize effects due to topological features and/or the gaslocal conditions at the surface of the nucleus.

The major focus of the presented study is analyzing of the end-of-mission pressure measurements by the ROSINA/COPSinstrument. Because the coma at a heliocentric distance of 3.8 AUwas in a collisionless regime, it can be described by solving theLiouville equation, as we have done in our analysis. We haveused the SHAP5 nucleus model to account for the topology of thevolatile source. Spacecraft trajectory and the instrumentpointing with respect to the comet’s nucleus have been obtainedwith the SPICE library. Here, we present results of our analysisand discuss the effects of the surface topology and that of the localsurface volatile injection on the distribution of gas in theinnermost coma of comet 67P/Churyumov–Gerasimenko.

Author(s): Valeriy Tenishev , Michael R. Combi , NicolasFougere , Martin Rubin , Chia-Yu Tzou , Yinsi Shou , T. I.Gombosi , Kathrin Altwegg , Zhenguang Huang , Gabor Toth ,Kenneth C. HansenInstitution(s): 1. Univ. of Bern, 2. Univ. of Michigan

509.06 – Temporal Variations of Water Vapor inthe Coma of 67P/Churyumov-Gerasimenko asObserved by Rosetta’s Alice FUV SpectrographDuring the Rosetta mission, the Alice far-ultraviolet (FUV)imaging spectrograph obtained spatially-resolved spectra of thecoma and nucleus of comet 67P/Churyumov-Gerasimenko overthe wavelength range of 700-2050Å. Typically, Alice detectedemissions from the neutral atomic daughter and granddaughterproducts (H, O, C, and S) of the primary molecular species in thecoma: H O, CO , CO, and O . However, during a six-monthperiod centered near perihelion, Alice directly detected watervapor in absorption of sunlight reflected from the nucleus. Wepresent here analyses of the water vapor column density asmeasured by the Alice FUV spectrograph. Alice is sensitive towater vapor at column densities greater than ~10 cm alongthe sum of the Sun-nucleus and nucleus-spacecraft lines of sight.Due to the excellent temporal coverage provided by the Aliceinstrument (exposures were typically obtained every 5-10minutes), we are able to show variations of water vapor in thecoma caused by the changing heliocentric distance of the comet,the comet’s ~12-hour rotation period, and short-term outbursts.We compare our water vapor column densities to those derivedfrom other instruments aboard the Rosetta spacecraft and usemodels to estimate the water production rate.

Rosetta is an ESA mission with contributions from its memberstates and NASA. The Alice team acknowledges continuingsupport from NASA’s Jet Propulsion Laboratory through contract1336850 to the Southwest Research Institute.

Author(s): Andrew J Steffl , Lori M. Feaga , MichaelA'Hearn , Jean-Loup Bertaux , Paul D. Feldman , Brian A.Keeney , Matthew M. Knight , Richard Medina , John Noonan ,Joel Wm. Parker , Jon Pineau , Eric Schindhelm , S. AlanStern , Maarten H. Versteeg , Ronald J. Vervack , Harold AWeaverInstitution(s): 1. Johns Hopkins Applied Physics Laboratory,2. Johns Hopkins University, 3. LATMOS, 4. Southwest ResearchInstitute, 5. Southwest Research Institute, 6. Stellar Solutions, 7.University of Maryland

509.07 – FUV Spectral Signatures of Molecules andthe Evolution of the Gaseous Coma of Comet67P/Churyumov-Gerasimenko

The Alice far-ultraviolet imaging spectrograph onboard Rosettaobserved emissions from atomic and molecular species fromwithin the coma of comet 67P/Churyumov-Gerasimenko duringthe entire escort phase of the mission from 2014 August to 2016September. The initial observations showed that emissions ofatomic hydrogen and oxygen close to the surface were producedby energetic electron impact dissociation of H O. Followingdelivery of the lander, Philae, on 2014 November 12, thetrajectory of Rosetta shifted to near-terminator orbits thatallowed for these emissions to be observed against the shadowednucleus that, together with the compositional heterogeneity,enabled us to identify unique spectral signatures of electronimpact excitation of H O, CO , and O . CO emissions were foundto be due to both electron and photoexcitation processes. Thus weare able, from far-ultraviolet spectroscopy, to qualitatively studythe evolution of the primary molecular constituents of thegaseous coma from start to finish of the escort phase. Our resultsshow asymmetric outgassing of H O and CO about perihelion,H O being dominant before perihelion and CO dominant after.

Author(s): Paul D. Feldman , Jean-Loup Bertaux , Lori M.Feaga , Brian A. Keeney , Matthew M. Knight , John Noonan ,Joel Wm. Parker , Eric Schindhelm , Andrew J Steffl , S. AlanStern , Ronald J. Vervack , Harold A WeaverInstitution(s): 1. Ball Aerospace, 2. Johns Hopkins AppliedPhysics Lab, 3. Johns Hopkins Univ., 4. LATMOS,CNRS/UVSQ/IPSL, 5. Southwest Research Institute, 6.University of Maryland

509.08 – Stellar Occultation by Comet67P/Churyumov-Gerasimenko Observed with theR-Alice Ultraviolet SpectrographFollowing our previous detection of ubiquitous H O and Oabsorption against the far-UV continuum of stars located near thenucleus of Comet 67P/Churyumov-Gerasimenko (Keeney et al.2017, MNRAS, 469, S158), we present a serendipitously observedstellar occultation that occurred on 13 September 2015,approximately one month after the comet’s perihelion passage.The A0 star HD 4150 appears in two consecutive 10-minutespectral images, both of which show H O absorption with columndensity > 10 cm and significant O absorption (O /H O ≈5-10%). No absorption from any other species is detected.Because the projected distance from the star to the nucleuschanges substantially between exposures, our ability to study thechanging H O production rate near the nucleus (ρ < 2 km) isunmatched by our previous observations. We find that both theH O column density and the relative O /H O abundancedecrease with increasing impact parameter, in accordance withexpectations. Rosetta is an ESA mission with contributions from its memberstates and NASA. The Alice team acknowledges continuingsupport from NASA’s Jet Propulsion Laboratory through contract1336850 to the Southwest Research Institute.

Author(s): Brian A. Keeney , S. Alan Stern , Paul D.Feldman , Michael A'Hearn , Jean-Loup Bertaux , Lori M.Feaga , Richard Medina , Joel Wm. Parker , Jon Pineau , EricSchindhelm , Andrew J Steffl , Maarten H. Versteeg , Harold AWeaverInstitution(s): 1. Applied Physics Laboratory, 2. BallAerospace Corp., 3. Johns Hopkins University, 4. LATMOS, 5.Southwest Research Institute, 6. Southwest Research Institute, 7.Stellar Solutions, Inc., 8. University of Maryland

509.09 – Ultraviolet observations of Coronal MassEjection impact on comet 67P/Churyumov-Gerasimenko by Rosetta AliceThe Rosetta Alice ultraviolet spectrograph onboard the EuropeanSpace Agency’s Rosetta spacecraft observed comet67P/Churyumov-Gerasimenko in its orbit around the Sun for justover two years. Observations taken two months after perihelion,in early 2015 October, show large increases in the Lyman-β, OI1304, OI] 1356, and CI 1657 Å atomic emission multiplets. Data

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510 – Mars: Upper Atmospheric Observations, Modeling, and Interpretations

from the Rosetta Plasma Consortium (RPC) instruments latershowed a coronal mass ejection (CME) impact at the cometcoincident with the emission increases, suggesting that the CMEimpact may have been the cause of the increase. Supporting this,the presence of the semi-forbidden OI] 1356 Å emission multipletis indicative of a considerable increase in electron impactemission from the coma and thus an increase in the electronenergy and/or density of the plasma, assuming no gaseousoutbursts occurred. Further, the strength of carbon emission linesdoes not support either CO or CO as significant sources of theoxygen emission. The mechanism responsible for this change tothe electron impact contribution could be a product of theinteraction between the CME and the coma of 67P. The observedelectron impact emission is used to determine the O /H O ratioof the coma at two peaks during the CME event. The exactrelationship between the CME and UV emission brightness is notwell constrained, but we will present several hypotheses toexplain the correlation. This research was made possible by the ESA Rosetta mission with

contributions from ESA member states and NASA. The Alice teamwould like to acknowledge the support of NASA, specificallythrough JPL contract 1336850 to the Southwest ResearchInstitute.

Author(s): John Noonan , S. Alan Stern , Paul D. Feldman ,Thomas Broiles , Cyril Simon Wedlund , Niklas JT Edberg ,Eric Schindhelm , Joel Wm. Parker , Brian A. Keeney , Andrew JSteffl , Harold A Weaver , Lori M. Feaga , Michael A'Hearn ,Jean-Loup BertauxInstitution(s): 1. Ball Aerospace, 2. Johns Hopkins University,3. Johns Hopkins University Applied Physics Laboratory, 4.LATMOS, 5. Southwest Research Institute, 6. Space ScienceInstitute, 7. Swedish Institute of Space Physics, 8. University ofArizona Lunar and Planetary Laboratory, 9. University ofMaryland, 10. University of Oslo

510.01 – Martian Metallic Ions Deposited by CometSiding Spring Defy ExpectationsOn October 19 2014, comet C/2013 A1 (Siding Spring) had aclose encounter with Mars and deposited cometary dust particlesinto the Martian atmosphere. Dust that impacted Mars wasreadily identifiable as the meteoric deposition of Mg, Fe, Na, etc.by the Imaging Ultraviolet Spectrograph (IUVS) and Neutral Gasand Ion Mass Spectrometer (NGIMS) on the NASA MarsAtmosphere and Volatile EvolutioN (MAVEN) spacecraft. WhileMg from comet Siding Spring and in a persistent layer wasidentified previously by IUVS, this is the first remote sensingreport on the abundance, spatial distribution and temporalevolution of Mg, Fe, and Fe . Subsequent evolution of thedistributions of ions and neutrals indicate distinct physicalmechanisms for distribution. We find vertical and latitudinalinhomogeneities that are inconsistent with expected dynamicaltransport mechanisms.

Author(s): Matteo Crismani , Nicholas M. Schneider , JohnPlane , Sonal Jain , Justin Deighan , Roger V Yelle , J. ScottEvansInstitution(s): 1. Computational Physics Inc. , 2. CU Boulder,3. Lunar and Planetary Institute, 4. University of Leeds

510.02 – Space weather events at Mars:atmospheric erosion during solar cycle 24The early Sun played a major role in the evolution of terrestrialatmospheres, with extreme EUV and X-ray fluxes, as well as amore intense solar wind and higher occurrences of powerful solartransient events. The Mars Atmosphere and Volatile EvolutioN(MAVEN) mission has been observing the upper atmosphere andmagnetic topology of Mars, and has made numerousmeasurements of solar transient events such as InterplanetaryCoronal Mass Ejections (ICMEs) and Stream Interaction Regions(SIRs) since November 2014. These events are characterized bydramatic changes in dynamic pressure, magnetic field strengthand substantial increases in escaping and precipitating planetaryions. We will present MAVEN observations of ICMEs and SIRsand show three of the strongest solar transient events observedduring solar cycle 24. We will also present global MHD and testparticle simulations of these events and discuss their influence onthe magnetic topology and atmospheric escape rates at Mars.Finally, using observations of the magnitude and frequency of Mand X class flares at younger, Sun-like stars, we have extrapolatedthe frequency of ICMEs at earlier stages of the Sun and willpresent simulations of the Mars-early solar wind interaction. Theextreme conditions in the Sun’s early history may have had asignificant influence on the evolution of the Martian atmosphereand may also have implications for exoplanets interacting withthe stellar winds of younger, more active stars.

Author(s): Shannon Curry , Janet Luhmann , ChuanfeiDong , Ed Thiemann , Jacob Gruesbeck , Christina Lee , Gina ADiBraccio , Yingjuan Ma , David Brain , Jasper Halekas , JaredR. Espley , John E.P. ConnerneyInstitution(s): 1. LASP, University of Colorado, Boulder, 2.NASA Goddard, 3. Princeton University , 4. SSL, University ofCalifornia, Berkeley, 5. University of California, Los Angeles, 6.University of Iowa

510.03 – Studying the seasonal changes in theMartian hydrogen exosphere near Perihelion usingHST and MAVEN observationsIn the past decade it has been discovered that the Martianexosphere exhibits significant seasonal variations in the rate ofhydrogen escape to space. The escape rate has been found tostrongly intensify as Mars approaches perihelion. It is importantto characterize these variations as the escape of hydrogen fromMars is directly tied to its water escape history. This work willpresent results from a recent study conducted on the seasonalvariation of the Martian hydrogen exosphere as Mars crossedperihelion and southern summer solstice during Mars year 33,based mainly on observations with the Hubble Space Telescope(HST). Other instruments, including the MAVEN IUVS Echelle,and MAVEN SWIA have also been used to characterize theMartian exospheric seasonal behavior around perihelion. We willprovide an overview of the data from these instruments, andcompare the derived results from their analyses, in terms of theHST images of the hydrogen exosphere.

Author(s): Dolon Bhattacharyya , John T. Clarke , Majd AMayyasi-Matta , Jasper Halekas , Jean-Yves Chaufray , MichaelS. Chaffin , Justin Deighan , Sonal Jain , Jean-Loup Bertaux ,Nicholas M. SchneiderInstitution(s): 1. Boston University, 2. Iowa University, 3.LASP, 4. LATMOS

510.04 – Mars Thermospheric TemperatureSensitivity to Solar EUV Forcing from the MAVENEUV MonitorSolar extreme ultraviolet (EUV) radiation is the primary heatsource for the Mars thermosphere, and the primary source oflong-term temperature variability. The Mars obliquity, dust cycle,tides and waves also drive thermospheric temperature variability;and it is important to quantify the role of each in order tounderstand processes in the upper atmosphere today and,ultimately, the evolution of Mars climate over time. AlthoughEUV radiation is the dominant heating mechanism, accuratelymeasuring the thermospheric temperature sensitivity to EUVforcing has remained elusive, in part, because Marsthermospheric temperature varies dramatically with latitude andlocal time (LT), ranging from 150K on the nightside to 300K onthe dayside. It follows that studies of thermospheric variabilitymust control for location.

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Instruments onboard the Mars Atmosphere and VolatileEvolutioN (MAVEN) orbiter have begun to characterizethermospheric temperature sensitivity to EUV forcing. Bougher etal. [2017] used measurements from the Imaging UltravioletSpectrograph (IUVS) and the Neutral Gas and Ion MassSpectrometer (NGIMS) to characterize solar activity trends in thethermosphere with some success. However, aside from restrictingmeasurements to solar zenith angles (SZAs) below 75 degrees,they were unable to control for latitude and LT because repeat-track observations from either instrument were limited orunavailable.

The MAVEN EUV Monitor (EUVM) has recently demonstratedthe capability to measure thermospheric density from 100 to 200km with solar occultations of its 17-22 nm channel. These newdensity measurements are ideal for tracking the long-termthermospheric temperature variability because they areinherently constrained to either 06:00 or 18:00 LT, and the orbithas precessed to include a range of ecliptic latitudes, a number ofwhich have been revisited multiple times over 2.5 years. In thisstudy we present, for the first-time, measurements ofthermospheric temperature sensitivity to EUV forcing derivedfrom the EUVM measurements. These results include sensitivesmeasured at the poles and near the equator for both terminators;therefore, we will also discuss the role of latitude on EUVtemperature sensitivity.

Author(s): Ed Thiemann , Francis Eparvier , LailaAndersson , Marcin Pilinski , Phillip Chamberlin , ChristopherFowlerInstitution(s): 1. NASA Goddard Space Flight Center(Formerly) , 2. University of ColoradoContributing team(s): MAVEN Extreme Ultraviolet MonitorTeam, MAVEN Langmuir Probe and Waves Team

510.05 – Mars Dayside ThermosphericComposition and Temperatures from the NGIMSMAVEN Instrument: Implications for ThermalBalancesThe Mars upper atmosphere, encompassing the thermosphere,ionosphere, and the lower exosphere (~100 to 500 km),constitutes the reservoir that regulates present day and historicalescape processes from the planet. The characterization of thisreservoir is therefore one of the major science objectives of theMAVEN mission. Current dayside thermospheric compositionand temperatures are the focus of this study. The primary MAVEN instrument for in situ sampling of neutralthermospheric structure is the Neutral Gas and Ion MassSpectrometer (NGIMS, Mahaffy et al. 2015) instrument. Itmeasures the neutral composition of at least 11 key gas speciesand their major isotopes, with a vertical resolution of ~5 km fortargeted species. Thermospheric temperatures are derived fromneutral density vertical structure (Bougher et al., 2017). FourNGIMS dayside sampling periods are chosen, spanning mid-April2015 to late-November 2016, for which the solar zenith angle isless than 60°. The Martian season advances from Ls ~ 335 to 256,while solar EUV fluxes are declining from solar moderate tominimum conditions. Each sampling period is composed of ~150to 200 orbits (NGIMS Level 2 V07_R02 files). We focus our studyon 5 dayside species: CO , O, N , CO, and He. Inbound densityprofiles (and derived temperatures) are extracted and averagedover various orbital intervals, in order to compute longitudeaveraged profiles, and to minimize the impact of small scale wavestructure. Corresponding Mars Global Ionosphere ThermosphereModel (M-GITM, Bougher et al., 2015) predictions for the sameseasonal/solar cycle conditions are compared to NGIMS densitymeasurements along the inbound orbit tracks below ~225 km.This M-GITM model is primarily driven by solar EUV-UV forcingat these altitudes; its simulations are used to provide a firstcomparison with the climatic trends (and variability) gleanedfrom these NGIMS datasets. M-GITM underlying dayside thermalbalances required to reproduce these measured density andtemperature profiles are also presented, with the goal ofconstraining dayside CO cooling rates.

Author(s): Stephen W. Bougher , Ryan Sharrar , Jared MBell , Paul R Mahaffy , Mehdi Benna , Meredith K Elrod , J.Scott EvansInstitution(s): 1. Computational Physics, Inc., 2. NASA GSFC,3. National Institute of Aerospace, 4. Univ. of Michigan

510.06 – First Retrieval of Thermospheric CarbonMonoxide From Mars Dayglow ObservationsAs a minor species in the Martian thermosphere, CarbonMonoxide (CO) is a tracer that can be used to constrain changingcirculation patterns between the lower thermosphere and uppermesosphere of Mars. By linking CO density distributions todynamical wind patterns, the structure and variability of theatmosphere will be better understood. Direct measurements ofCO can therefore provide insight into the magnitude and patternof winds and provide a metric for studying the response of theatmosphere to solar forcing. In addition, CO measurements canhelp solve outstanding photochemical modeling problems inexplaining the abundance of CO at Mars. CO is directlyobservable by electron impact excitation and solar resonancefluorescence emissions in the far-ultraviolet (FUV). The retrievalof CO from solar fluorescence was first proposed over 40 yearsago, but has been elusive at Mars due to significant spectralblending. However, by simulating the spectral shape of eachcontributing emission feature, electron impact excitation andsolar fluorescence brightnesses can be extracted from thecomposite spectrum using a multiple linear regression approach.We use CO Fourth Positive Group (4PG) molecular band emissionobserved on the limb (130 – 200 km) by the Imaging UltravioletSpectrograph (IUVS) on NASA’s Mars Atmosphere and VolatileEvolution (MAVEN) spacecraft over both northern and southernhemispheres from October 2014 to December 2016. We presentthe first direct retrieval of CO densities by FUV remote sensing inthe upper atmosphere of Mars. Atmospheric composition isinferred using the terrestrial Atmospheric Ultraviolet RadianceIntegrated Code adapted to the Martian atmosphere. Weinvestigate the sensitivity of CO density retrievals to variability insolar irradiance, solar longitude, and local time. We compare ourresults to predictions from the Mars Global Ionosphere-Thermosphere Model as well as in situ measurements by theNeutral Gas and Ion Mass Spectrometer on MAVEN and quantifyany differences.

Author(s): J. Scott Evans , Michael H. Stevens , Sonal Jain ,Justin Deighan , Jerry Lumpe , Nicholas M. Schneider , A. IanStewart , Matteo Crismani , Arnaud Stiepen , Michael S.Chaffin , Majd A Mayyasi-Matta , William E. McClintock , GregHolsclaw , Franck Lefevre , Daniel Lo , John T. Clarke , FranckMontmessin , Stephen W. Bougher , Jared M. Bell , FrankEparvier , Ed Thiemann , Paul R Mahaffy , Mehdi Benna ,Meredith K Elrod , Bruce JakoskyInstitution(s): 1. Boston University, 2. Computational Physics,Inc., 3. Laboratory for Atmospheric and Space Physics, 4.LATMOS/CNRS, 5. NASA Goddard Space Flight Center, 6. NavalResearch Laboratory, 7. University of Arizona, 8. University ofLiège, 9. University of Michigan

510.07 – Mars’ seasonal mesospheric transportseen through nitric oxide nightglowWe analyze the ultraviolet nightglow in the atmosphere of Marsthrough nitric oxide (NO) δ and γ band emissions as observed bythe Imaging UltraViolet Spectrograph (IUVS) instrumentonboard the Mars Atmosphere and Volatile EvolutioN (MAVEN)spacecraft when it is at apoapse and periapse. In the dayside thermosphere of Mars, solar extreme-ultravioletradiation dissociates CO and N molecules. O( P) and N( S)atoms are carried from the dayside to the nightside by the day-night hemispheric transport process, where they descend throughthe nightside mesosphere and can radiatively recombine to formNO(C Π). The excited molecules rapidly relax by emittingphotons in the UV δ and γ bands. These emissions are indicatorsof the N and O atom fluxes from the dayside to Mars’ nightsideand the descending circulation pattern from the nightside

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511 – Outer Irregular Satellites

thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ;Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérardet al., 2008 ; Stiepen et al., 2015, 2017).

Observations of these emissions are gathered from a large datasetspanning different seasonal conditions.

We present discussion on the variability in the brightness andaltitude of the emission with season, geographical position(longitude), and local time, along with possible interpretation bylocal and global changes in the mesosphere dynamics. We showthe possible impact of atmospheric waves forcing longitudinalvariability and data-to-model comparisons indicating a wave-3structure in Mars’ nightside mesosphere. Quantitativecomparison with calculations of the Laboratoire de MétéorologieDynamique-Mars Global Climate Model (LMD-MGCM) suggeststhe model reproduces both the global trend of NO nightglowemission and its seasonal variation. However, it also indicateslarge discrepancies, with the emission up to a factor 50 timesfainter in the model, suggesting that the predicted transport is tooefficient toward the night winter pole in the thermosphere by∼20° latitude to the north.

These questions are now addressed through an extensive datasetof disk images, in complement to improved simulations of theLMD-MGCM and the Mars Global Ionosphere-ThermosphereModel (MGITM) models.

Author(s): Zachariah Milby , Arnaud Stiepen , Sonal Jain ,Nicholas M. Schneider , Justin Deighan , Francisco Gonzalez-Galindo , Jean-Claude Gerard , Michael H. Stevens , StephenW. Bougher , J. Scott Evans , A. Ian Stewart , MichaelChaffin , Matteo Crismani , William E. McClintock , John T.Clarke , Greg Holsclaw , Franck Montmessin , Franck Lefevre ,Francois Forget , Daniel Y. Lo , Benoît Hubert , BruceJakoskyInstitution(s): 1. Boston University, 2. Computational Physics,Inc., 3. Instituto de Astrofísica de Andalucía, 4. Laboratoire deMétéorologie Dynamique (LMD), 5. Laboratoire de PhysiqueAtmosphérique et Planétaire, Space Sciences, Technologies, andAstrophysics Research (STAR) Institute, 6. Laboratory forAtmospheric and Space Physics, 7. LATMOS/IPSL, 8. NavalResearch Laboratory, 9. Space Sciences, Technologies, andAstrophysics Research (STAR) Institute, 10. University ofArizona, 11. University of Colorado Boulder, 12. University ofMichigan

510.08 – Variability of Martian TurbopauseAltitudesThe transition region between the well-mixed, turbulent loweratmosphere and the diffusive upper atmosphere - the turbopause- is an area of coupled physical processes that can have significantimpacts on the structure and dynamics of the mesosphere andthermosphere. Above the turbopause, molecular diffusiondominates and species fractionate according to their masses.Below, turbulence is strong and waves dissipate and break. Wehave used density measurements from MAVEN's NGIMSinstrument and temperatures from MRO's MCS to calculateturbopause altitudes over the course of a Martian year.

The homopause, or "mixing-turbopause,” is defined with respectto the mixing ratio of a given atmospheric species. The meanmolecular mass of the atmosphere remains essentially constantbelow, but each species has its own scale height above. Wedetermined this altitude for each MAVEN orbit between Feb 2015- Dec 2016 by extrapolating the ratio of N and Ar densitiesdownward to where their ratio equals that measured by Curiosity.To determine the "wave-turbopause" (Offermann et al., 2007) weused variations in monthly-averaged temperature profiles of theupper and lower atmosphere. Because the dissipation of wavesproduces turbulence the turbopause altitude is set by thetransition from strong to weak dissipation. If no energy were lost,

the amplitude of a vertically propagating gravity wave wouldincrease exponentially with altitude. Using the monthly standarddeviation in temperatures as a proxy for wave amplitude, we showthat waves are strongly dissipated at low altitudes but freelypropagating in the lower thermosphere. The altitude at which thestandard deviation begins to increase substantially from lowvalues at mid-altitudes determines the altitude of the "wave-turbopause." The observed range of turbopause altitudes is 80-140 km. Theturbopause is highest during the day and for Ls values near 270°.Homopause altitudes correlate well with changes in COdensities. The variation in turbopause altitudes means thatenergy, mass, and momentum transported vertically aredeposited at different altitudes across the planet, which can havea substantial effect on the thermal and dynamical state of themiddle-upper atmosphere.

Author(s): Marek Slipski , Bruce Jakosky , Mehdi Benna ,Paul R Mahaffy , Meredith K Elrod , David M. Kass , FranciscoGonzalez-GalindoInstitution(s): 1. Instituto de Astrofísica de Andalucía-CSIC, 2.JPL, 3. LASP, CU Boulder, 4. NASA/Goddard Space FlightCenter

510.09 – Standardizing Scale Height Computation ofMAVEN NGIMS Neutral Data and Variations BetweenExobase and Homeopause Scale HeightsThe MAVEN NGIMS team produces a level 3 product whichincludes the computation of Ar scale height an atmospherictemperatures at 200 km. In the latest version (v05_r01) this hasbeen revised to include scale height fits for CO2, N2 O and CO.Members of the MAVEN team have used various methods tocompute scale heights leading to significant variations in scaleheight values depending on fits and techniques within a few orbitseven, occasionally, the same pass. Additionally fitting scaleheights in a very stable atmosphere like the day side vs night sidecan have different results based on boundary conditions.Currently, most methods only compute Ar scale heights as it ismost stable and reacts least with the instrument. The NGIMSteam has chosen to expand these fitting techniques to includefitted scale heights for CO , N , CO, and O. Having comparedmultiple techniques, the method found to be most reliable formost conditions was determined to be a simple fit method. Wehave focused this to a fitting method that determines the exobasealtidude of the CO2 atmosphere as a maximum altitude for thehighest point for fitting, and uses the periapsis as the lowest pointand then fits the altitude versus log(density). The slope of altitudevs log(density) is -1/H where H is the scale height of theatmosphere for each species. Since this is between thehomeopause and the exobase, each species will have a differentscale height by this point. This is being released as a newstandardization for the level 3 product, with the understandingthat scientists and team members will continue to compute moreprecise scale heights and temperatures as needed based onscience and model demands. Additionally, we are examining these scale heights for variationsseasonally, diurnally, and above and below the exobase. Theatmosphere is significantly more stable on the dayside than onthe nightside. We have also found a jog or kink in the atmospherein several atmospheric profiles slightly above the exobaseindicating a change in the scale height between the super andsupra- exobase temperatures. Waves are more prevalent on thenight side and terminator sides making scale height fits moredifficult.

Author(s): Meredith K Elrod , Marek Slipski , ShannonCurry , Hayley Williamson , Mehdi Benna , Paul R MahaffyInstitution(s): 1. LASP-University of Colorado, 2. NASAGoddard SFC, 3. SSL-Berkely , 4. University of Virginia

511.01 – Compositional Analyses and Implicationsof Visible/Near Infrared Spectra of Outer Irregular

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of Visible/Near-Infrared Spectra of Outer IrregularJovian SatellitesThe existence of a visible-near infrared absorption featureattributed to aqueous alteration products has been suggested inboth grey and reddened broadband photometry of some outerirregular jovian satellites. Moderate resolution VNIR narrowbandspectroscopy was obtained of the jovian irregular satellites JVIHimalia, JVII Elara, JVIII Pasiphae, JIX Sinope, JX Lysithea, JXICarme, JXII Ananke and JXVII Callirrhoe in 2006, 2008, 2009,and 2010 using the MMT Observatory facility Red Channelspectrograph to confirm the presence of this feature. The spectraare centered near 0.64 μm in order to cover the 0.7-μm featureentirely (generally ranging from 0.57 to 0.83 μm). The spectragenerally have a dispersion/element of ~0.6 nm (6Å); somespectra are smoothed. These spectra sample three prograde (i =28 ), four retrograde (i = 149 , 165 ) and one independentsatellite.

We observe these findings among the spectra: - An absorption feature centered near 0.7 µm exists in the spectraof the three prograde (i = 28 ) satellites. This feature is spectrallybroader than the 0.7-µm feature observed in C-complex asteroids.None appears spectrally reddened. This suggests that theseprograde satellites have a common parent body. - A different absorption feature appears in the spectra of the threeretrograde (i = 149 ) satellites, also suggesting a common parentbody. Varying reddening is observed. This feature is similar inspectral location and width to the 0.7-µm feature. - Reddening is observed in the individual observation of JXICarme (i = 165 ), and independent satellite JIX Sinope, similar tothe D-class asteroid spectra dominating the Trojan population. Asuggested absorption feature is being investigated. Mixing modeling of combinations of both expected and proposedcompositions including carbonaceous materials, phyllosilicates,mafic silicates, and other opaque materials, is currentlyunderway. Results will be reported and discussed at the meeting.

Acknowledgments: The MMT Observatory is a joint facility ofthe University of Arizona and the Smithsonian Institution. Thisresearch has been supported by SSERVI CLASS.

Author(s): Faith Vilas , Amanda HendrixInstitution(s): 1. National Science Foundation, 2. PlanetaryScience Institute

511.02 – Color Survey of the Irregular PlanetarySatellitesIrregular planetary satellites are characterized by their largeorbital distance from their planet, their high eccentricity and theirhigh inclination, all indicating that they were captured. However,the mechanism of capture and the source region of the satellitesremain subjects of conjecture. This work presents the opticalmagnitudes and colors from a photometric survey of 42 irregularsatellites with data obtained from the LRIS instrument on the 10-meter telescope at the Keck Observatory in Hawaii. Color is usedas a proxy for composition. We compare the satellite populationsof different planets and compare the satellites as a whole withother solar system small-body populations. For instance, ifirregular satellites were captured from the Kuiper Belt, as iscommonly proposed, then some might contain the ultraredmaterial that is common in the trans-Neptunian and Centaurpopulations. Overall our data show that the irregular satelliteslack ultrared matter. They are color-wise more similar to thecomets, giant planet Trojans and other bodies of the middle solarsystem. Implications of our observations, and comparisons withprevious color work, will be discussed.

Author(s): Ariel Graykowski , David JewittInstitution(s): 1. University of California Los Angeles

511.03 – Investigating the origins of the Irregularsatellites using CladisticsThe irregular satellites of Jupiter and Saturn are thought to beobjects captured during a period of instability in the early solarsystem. However, the precise origins of these small bodies remainelusive. We use cladistics, a technique traditionally used bybiologists, to help constrain the origins of these bodies. Ourresearch contributes to a growing body of work that usescladistics in astronomy, collectively called astrocladistics. Wepresent one of the first instances of cladistics being used in aplanetary science context. The analysis uses physical andcompositional characteristics of three prograde Jovian irregularsatellites (Themisto, Leda & Himalia), five retrograde Jovianirregular satellites (Ananke, Carme, Pasiphae, Sinope &Callirrhoe), along with Phoebe, a retrograde irregular satellite ofSaturn, and several other regular Jovian and Saturnian satellites.Each of these members are representatives of their respectivetaxonomic groups. The irregular satellites are compared withother well-studied solar system bodies, including satellites,terrestrial planets, main belt asteroids, comets, and minorplanets. We find that the Jovian irregular satellites cluster withasteroids and Ceres. The Saturnian satellites studied here arefound to form an association with the comets, adding to thenarrative of exchange between the outer solar system andSaturnian orbital space. Both of these results demonstrate theutility of cladistics as an analysis tool for the planetary sciences.

Author(s): Timothy Holt , Jonti Horner , ChristopherTylor , David Nesvorny , Adrian Brown , Brad CarterInstitution(s): 1. Plancius Research, LLC, 2. SwRI, 3.University of Southern Queensland

511.04D – The Nice model can explain thedispersion of the prograde Himalia family ofirregular satellites at JupiterMore than 50 irregular satellites revolve around Jupiter in whichat least three distinct collisional families are identified. Amongthem, the Himalia family is unique in the large velocitydispersion--several hundred m/s--among its members,inconsistent with a purely collisional origin. We explore this puzzle in the context of the Nice scenario of earlysolar system evolution. There, the giant planets migratedsignificant distances due to interactions with a primordialplanetesimal disk. We generate a synthetic, collisionally-producedHimalia family and follow its evolution through principal eventsof the Nice model. Two situations are considered: (i) Theplanetesimal disk is solely composed of large, moon-sized objects.In this case, the family is dramatically scattered, especially insemimajor axis and eccentricity, as the planetesimals fly byJupiter. The velocity dispersion of $\sim60\%$ of familymembers is raised to several hundred m/s, satisfactorilyexplaining the observed dispersion. However, this situation is notlikely as the considered planetesimals seem unphysically massive.We now consider the alternative case (ii) within the so-called``Jumping Jupiter’’ where planetary, rather than planetesimalencounters are responsible for the observed dispersion. Here, icegiants encounter Jupiter up to a few hundred times (Nesvorn\'{y}\& Morbidelli 2012). We find $\lesssim20$ such planetaryencounters disperse the synthetic family to the observed degree.We also find that the family cannot survive $\sim100$ such fly-bys as the satellites become too widely dispersed. Reference: Nesvorn\'{y}, D., \& Morbidelli, A. 2012, AJ, 144, 117.

Author(s): Daohai Li , Apostolos ChristouInstitution(s): 1. Armagh Obervatory

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Authors IndexA'Hearn, Joseph: 212.09A'Hearn, Michael: 509.04,509.06, 509.08, 509.09Abe, Lyu: 500.03Abe, Masanao: 204.10, 417.20Abgarian, Mary: 105.05Abramov, Oleg: 203.03Abramson, Evan: 222.01Achilles, Cherie: 400.06Achterberg, Richard: 205.09,304.03, 304.04, 304.06Achterberg, Richard K.: 213.05,304.10Adamkovics, Mate: 118.04,205.05, 214.01, 304.12D,419.02Adams, Fred C.: 216.11, 405.07Adriani, Alberto: 109.02,118.04, 205.10Aftosmis, Michael: 111.05Agabi, Abdelkrim: 500.03Agarwal, Jessica: 208.08Agrawal, Parul: 106.02Aharonson, Oded: 110.24,508.05, 508.11DAhern, Alexandra: 418.20Ahlers, Johnathon: 416.10,416.24Akins, Alexander Brooks.:417.04Alcock, Charles: 216.14, 216.15Alday, Juan: 203.06Alexandersen, Mike: 216.12,218.08, 405.02, 504.12Ali-Lagoa, Victor: 110.27,117.08Allen, Campbell: 422.05Allen, Sarah: 422.05Alonso, Maria: 224.04Alsedairy, Talal: 418.25Altmann, Martin: 117.11Altobelli, Nicolas: 301.03Altwegg, Kathrin: 509.05Alvarellos, Jose: 401.02Alvarez, Fernando: 216.15Alvarez-Candal, Alvaro: 216.18,416.06Amason, Charlee: 420.04Ammannito, Eleonora: 306.01Anderson, Carrie: 304.10Anderson, John: 303.02Anderson, John D.: 109.01,115.22Anderson, Seamus: 204.12Anderson, Yanhua: 212.11Andersson, Laila: 510.04Andert, Thomas: 502.03,509.01Anupriya, Anupriya: 219.15Aoki, Shohei: 219.09Apai, Daniel: 416.20Aponte-Hernandez, Betzaida:112.09, 204.02, 414.24Araujo, Rosana: 216.13Arcand, Kimberly K.: 101.05Archer, Paul Douglas.: 400.06,418.22Arnold, Gabriele: 417.01Arras, Phil: 421.03Asada, Yuma: 417.20Ashby, Keir: 506.06, 506.07Asphaug, Erik: 404.03,404.09D, 414.27, 508.03Aspin, Colin: 111.02

Assafin, Marcelo: 216.03Atkinson, David H.: 219.21Atreya, Sushil K.: 115.20, 118.04Austin, Daniel E.: 219.15Austria, Mia: 400.01Avdellidou, Chrysa: 201.02,201.03, 204.08Avenson, Brad: 219.19Axelrod, Tim S.: 103.05, 117.04Ayala-Loera, Carmen: 216.18Aye, K-Michael: 418.19, 422.05Aznar, Amadeo: 204.02Bacci, Paolo: 504.08Bachini, Mauro: 504.08Backhaus, Udo: 200.04Badman, Sarah: 115.16, 115.24Baek, Kilho: 417.19Bagnulo, Stefano: 302.05Bailey, Elizabeth: 405.09Bailey, Samuel "Hop": 219.19Baines, Kevin: 213.09Baines, Kevin H.: 115.08,115.16, 115.20, 205.07, 205.08Baker, Emily: 212.01Bakerman, Maya: 101.09Bakos, Gaspar: 416.01Baldwin, Taylor: 408.07Ballard, Sarah: 506.05Bampasidis, Georgios: 213.05Bancelin, David: 419.04Banerdt, Bruce: 219.16Banfield, Don: 219.16Banks, Maria E.: 218.01,404.02Bannister, Michele T.: 216.12,405.02, 504.12Barbieri, Cesare: 415.02Barclay, Thomas: 224.06Barlow, Nadine G.: 116.03,404.02Barnes, Jason W.: 213.09,213.10, 219.02, 416.24Barnett, Megan: 118.04Barnouin, Olivier: 204.09Barrera, Jose: 414.25Barriot, Jean-Pierre: 509.01Barth, Erika L.: 217.01Barucci, Maria Antonieta.:110.08, 509.03Bateman, Fred: 203.10Bath, Karl-Ludwig: 501.01Battams, Karl: 414.03Battista, Corina: 219.18Batygin, Konstantin: 405.09,405.10, 506.09DBauer, James M.: 110.31, 117.10,302.03, 403.01, 414.15, 414.16,420.03Bean, Jacob: 408.05Beaudin, Gerard: 415.03,415.05, 415.06Becker, Juliette: 216.11, 405.07Becker, Kris J.: 110.05Becker, Tracy M.: 116.07,203.06, 221.03Beebe, Reta F.: 218.03, 218.04Beigbeder, Laurent: 415.04Beisker, Wolfgang: 501.01Bell, Jared M.: 510.05, 510.06Bellotti, Amadeo: 118.03Bellucci, Giancarlo: 507.01,507.02Belton, Michael J S.: 403.02,414.25

Benecchi, Susan: 216.06,504.01, 504.02, 504.03,504.04, 504.05Benecchi, Susan D.: 110.24,504.07Benfell, Nathan: 501.06Benna, Mehdi: 510.05, 510.06,510.08, 510.09Benner, D. Chris: 416.26Benner, Lance A M.: 110.12,204.01Bennett, Carina: 116.05Benson, Conor: 117.05Bentley, Mark: 415.08Berard, Diane: 216.03, 501.01,501.02, 504.08Bercovici, Benjamin: 111.11Berdis, Jodi: 218.04, 418.15Bertaux, Jean-Loup: 414.07,509.04, 509.06, 509.07,509.08, 509.09, 510.03Bertrand, Tanguy: 102.05,105.06DBeshore, Edward C.: 100.02Betremieux, Yan: 300.04Beyer, Ross A.: 102.01, 102.03,102.05, 102.06, 102.08,102.09D, 215.06, 218.01,221.02Bézard, Bruno: 115.02, 209.05,209.08, 213.01, 304.03Bhatt, Bhuwan: 420.02Bhattacharya, Satadru:404.05DBhattacharyya, Dolon: 418.03,510.03Bhiravarasu, Sriram Saran.:112.09, 204.02, 404.05D,414.24Bhure, Sakhee: 115.19Bibring, Jean-Pierre: 418.21Bida, Thomas A.: 422.01Bieler, Andre: 509.04Bierhaus, Edward B.: 401.02Bierson, Carver: 417.21Bigot, Lionel: 500.03Bills, Bruce: 220.05Binzel, Richard P.: 102.09D,110.09, 204.04, 221.02Bird, Michael: 215.07, 502.03,509.01Birkmann, Stephan: 219.10Birlan, Mirel: 208.04, 208.05Bishop, Bradley: 213.07Biver, Nicolas: 102.02, 415.03,415.05, 415.06Bjoraker, Gordon L.: 115.20,118.04, 205.05, 205.09Blacksberg, Jordana: 219.22Blain, Doriann: 115.02Blake, David F.: 400.06Blalock, John J.: 115.27, 118.01,205.11, 422.02Bland, Michael T.: 203.02,306.01Blaney, Diana L.: 214.09Blankenship, Don: 214.04Blankenship, Donald D.: 214.09Blecic, Jasmina: 402.04,416.01, 416.02, 416.03, 416.04Bloom, Anthony: 301.03Bloxham, Jeremy: 109.01,303.03Boardman, Ian: 103.01

Bockelee-Morvan, Dominique:102.02, 415.01, 415.03, 415.05,415.06Bodewits, Dennis: 401.03,403.01, 414.15Bodnarik, Julia: 305.05, 414.04Boe, Ben: 112.01Boice, Daniel C.: 305.12boissier, Jeremie: 102.02,216.07Boley, Aaron C.: 416.12,500.02Bolin, Bryce T.: 100.02, 112.01,201.02, 201.03, 208.12DBollengier, Olivier: 222.01Bolton, Scott: 109.03, 205.02Bolton, Scott J.: 109.01, 109.02,303.03Bonev, Boncho P.: 305.03,305.04, 305.09, 414.06,414.12, 414.13Boogert, Abraham C A.: 219.09Boomi, Shadi: 215.03Borisov, Galin: 302.05Boryta, Mark: 203.09Bosh, Amanda S.: 216.01,216.02, 221.03Bott, Kim: 416.18Bottke, William: 100.02,100.03, 112.01, 214.21, 401.02Bougher, Stephen W.: 418.02,510.05, 510.06, 510.07Bouley, Sylvain: 501.01Bouquet, Alexis: 214.05Bouquillon, Sebastien: 117.11Bourke, Mary: 418.17Bowling, Timothy: 306.02Boyd, Patricia T.: 224.06Boyé-Péronne, Séverine: 414.28Bozek, Brandon: 110.15Bradley, Eric Todd.: 104.04Bradley, Mary Elizabeth.:217.02Braga-Ribas, Felipe: 216.03,501.01, 504.08Brain, David: 411.01, 418.02,505.02, 505.03, 510.02Brasser, Ramon: 413.09,508.09Bratsolis, Emmanuel: 301.03Bray, Veronica: 219.19Bressi, Terry: 112.08Brisset, Julie: 204.12Britt, Daniel: 110.21, 116.07,208.01Broiles, Thomas: 509.09Bromley, Benjamin C.: 508.07Brossier, Jeremy: 213.09Brown, Adrian: 511.03Brown, J. Michael.: 222.01Brown, Michael: 203.05,302.06D, 405.09Brown, Michael E.: 405.06Brown, Robert H.: 115.16,205.07, 210.01, 212.04, 213.09,301.03Brown, Shannon: 205.02Broz, Miroslav: 110.41, 201.05,413.06, 500.05Brozovic, Marina: 110.12,204.01Brucker, Melissa: 112.08Bruinsma, Sean: 418.01Bryson, Kathryn L.: 106.02

Buckman, Miles: 110.30Bue, Brian: 400.02Buhler, Peter Benjamin.:102.04Buie, Marc W.: 110.40, 215.04,221.02, 221.03, 504.01,504.02, 504.03, 504.04,504.05, 504.06, 504.07Buratti, Bonnie J.: 101.06,102.01, 105.05, 115.16,200.02, 205.07, 213.09Burbine, Thomas H.: 110.09Burge, Johannes M.: 219.11Burger, Christoph: 419.04Burns, Joseph A.: 212.01,212.10Burt, Brian: 110.09, 204.04Bus, Schelte J.: 216.17Busch, Michael: 204.01Butler, Bryan J.: 102.02,118.04, 203.05, 216.07, 304.11Butler, Nathaniel R.: 117.04Byrne, Shane: 219.19Byron, Ben: 404.08Cable, Morgan: 216.16Cahill, Joshua: 404.07, 404.08Calef, Fred J.: 422.05Camargo, Julio: 216.03, 501.01,501.02, 504.06Cambioni, Saverio: 201.04Cammarano, Fabio: 214.05Campbell, Charissa L.: 101.08Campbell, Donald B.: 110.15Campbell, Tanner: 204.09Campins, Humberto: 117.08Campo Bagatin, Adriano:504.08Cao, Hao: 108.03, 109.01,303.03, 303.05Capaccioni, Fabrizio: 212.04,415.01Caplinger, Mike: 109.03Carbognani, Albino: 504.08Carlozzi, Alexander A.: 106.02Carpenter, Scott: 219.16Carrasco, Nathalie: 213.02,213.03Carry, Benoit: 103.06, 208.04,208.05Carter, Brad: 511.03Carter, John: 418.21Cartwright, Richard: 208.07,210.02Case, Anthony: 219.18Castillo Castellanos, Jorge:220.05Castillo-Rogez, Julie: 306.01Castro Chacón, Joel: 216.14,216.15Cavalié, Thibault: 209.05,209.08, 209.09Cellino, Alberto: 302.05Cerroni, Priscilla: 212.04Chaffin, Michael: 510.07Chaffin, Michael S.: 418.03,418.06, 418.07, 507.06, 510.03,510.06Challener, Ryan: 416.01,416.02, 416.04Challener, Ryan C.: 402.04,416.03Chamberlin, Phillip: 510.04Chamberlin, Phillip C.: 418.07Chambers, John E.: 413.05,419.03

Chambers, Kenneth C.: 100.04,112.10, 405.01Chan, Kwing L.: 115.25Chance, Quadry: 217.04Chancia, Robert Ormal.:104.06Chanorz, Sebastian: 406.01Chanover, Nancy J.: 115.08,218.03, 218.04, 224.03,304.06, 417.14Chapellier, Eric: 500.03Charles, Mentzer: 420.01Charnley, Steven B.: 304.06,304.07, 414.14, 414.19Charnoz, Sebastien: 104.03Chastel, Serge: 405.01Chatelain, Joseph: 110.35Chatterjee, Sourav: 506.02Chaufray, Jean-Yves: 418.03,510.03Chauhan, Prakash: 404.05DChemke, Rei: 416.21Chen, Haoyuan: 110.39Chen, Howard: 506.02Chen, Wangli: 219.05, 417.15,417.16Chen, Wen-Ping: 216.14, 216.15Chen, Ying-Tung: 216.12,405.02, 504.12Chen, YuanYuan: 111.10Chen-Chen, Hao: 418.10Cheng, Andrew F.: 102.01,102.03, 102.08Chesley, Steven R.: 110.06,112.04, 112.14, 219.22Chitamitara, Aerbwong: 416.14Cho, Sang-Yeon: 224.03Choi, Young-Jun: 417.19Choukroun, Mathieu: 224.04,415.03, 415.05, 415.06Chrenko, Ondrej: 413.06,500.05Christensen, Eric J.: 110.10,117.07, 204.04Christensen, Philip R.: 110.01,110.02, 203.03, 214.09Christiansen, Eric: 213.07,218.06Christie, Duncan: 421.03Christou, Apostolos: 302.05,511.04DChu, Kathryn: 400.03Chu, You-Hua: 216.14, 216.15Church, Sarah E.: 420.04Chyba, Monique: 112.01Ciabattari, Fabrizio: 504.08Ciarletti, Valérie: 415.08Ciarniello, Mauro: 104.07,212.04Cintala, Mark: 117.01Citron, Robert I.: 508.05Clark, Benton: 400.06Clark, Beth Ellen.: 110.01,110.02Clark, Joelle G.: 116.03Clark, John H.: 406.02Clark, Roger Nelson.: 104.07,115.16, 205.07, 210.01, 210.05,212.04, 213.09, 214.18Clarke, John T.: 418.03,418.06, 507.06, 510.03, 510.06,510.07Claytor, Zach: 111.02, 112.06,112.13Clement, Matthew: 508.04

Close, Sigrid: 110.17Cloutis, Edward: 110.05, 110.23Cochran, Anita L.: 305.03,305.04, 305.09, 414.09Cochrane, Corey: 219.18,224.04Colas, Francois: 302.05, 501.01Collins, Geoffrey: 214.09,220.03Colon, Knicole D.: 506.08Colwell, Josh: 104.09D, 207.04Colwell, Joshua E.: 204.12,212.06Combe, Jean-Philippe: 214.18Combi, Michael R.: 414.06,414.07, 415.01, 509.04, 509.05Cominsky, Lynn R.: 101.05Connerney, J. E P.: 109.01Connerney, John EP.: 109.02,303.03, 505.02, 510.02Connour, Kyle: 110.33, 507.06Conrad, Al: 204.07, 407.02Consolmagno, Guy: 116.01Cook, Jason C.: 105.03, 221.02Cook, Kem H.: 103.05, 216.14,216.15Cooper, Brittney A.: 101.08Cooper, John F.: 406.02Cooper, Ken: 224.04Cordiner, Martin: 304.06,304.07, 414.06, 414.14, 414.19Coren, David: 219.18Corlies, Paul: 304.09, 304.12DCornet, Thomas: 213.09Cosentino, Richard: 115.04,115.05, 205.01Cottini, Valeria: 213.05Coustenis, Athena: 213.05,301.03Couturier-Tamburelli, Isabelle:213.03Covey, Steven D.: 110.21Cox, Timothy: 420.01Cracraft, Misty: 203.04Craft, Kathleen: 220.04Cravens, Thomas: 211.02Crawford, Timothy J.: 416.26Crew, Alexander: 219.18Crismani, Matteo: 418.06,418.07, 507.06, 510.01,510.06, 510.07Crisp, David: 416.18Crombie, Kate: 218.01Crovisier, Jacques: 415.03,415.05, 415.06Crowell, Jenna L.: 110.15,204.02Cruikshank, Dale P.: 102.06,102.07, 102.09D, 105.03,107.02, 210.01, 210.05, 214.18,221.02Cubillos, Patricio: 402.04,416.01, 416.02, 416.03, 416.04,416.09Cuk, Matija: 419.01Cunningham, Nichol: 420.04Curry, Shannon: 418.02,418.05, 505.02, 510.02, 510.09Curtis, Anthony: 420.01Cutri, Roc M.: 103.03, 117.10Cuzzi, Jeffrey N.: 212.04, 212.11Cynthia, Hall: 116.07D'Amore, Mario: 417.01D'Aversa, Emiliano: 212.04,214.18

Daerden, Frank: 507.01, 507.02Dahl, Emma: 115.08Dahl, Peter: 219.19Dailey, John: 103.03Dalle Ore, Cristina M.: 102.06,102.07, 210.05, 212.04, 214.18,221.02Dame, Rudger H.: 418.22Damiano, Mario: 402.06DDas, Himadri: 414.02Daumont, Ludovic: 416.26Dauverge, Jean-Luc: 501.01David, Pedro: 103.06Davidsson, Bjorn: 415.02,415.03, 415.05, 415.06Davies, Ashley: 407.02Davis, Alex: 117.03, 302.04Davis, Karan: 119.01, 507.04Davis, Michael W.: 224.05Dawson, Rebekah Ilene.: 216.12de Kleer, Katherine: 214.01de Kleer, Katherine R.: 407.02,407.03Dde León, Julia: 117.08de Oliveira, Nelson: 414.28de Pater, Imke: 104.01, 118.04,205.03, 205.05, 211.03,214.01, 214.19, 407.02,407.03Dde Prá, Mario: 117.08De Sanctis, Maria Cristina:306.01, 306.02De Santana, Thamiris: 212.08de Val-Borro, Miguel: 414.06,414.14Deau, Estelle: 212.05Dederick, Ethan: 303.09DDeienno, Rogerio: 201.01Deighan, Justin: 418.03,418.06, 418.07, 507.06, 510.01,510.03, 510.06, 510.07del Rio-Gaztelurrutia, Teresa:205.06Del Vigna, Alessio: 103.06Delbo, Marco: 110.02, 201.02,201.03, 208.12DDelcroix, Marc: 209.07Della-Giustina, Daniella:219.19DellaGiustina, Daniella: 116.05Dello Russo, Neil: 305.03,305.04, 305.09, 414.06,414.12, 414.13dell’Oro, Aldo: 302.05DeMeo, Francesca E.: 110.09,204.04Deming, Drake: 408.05, 416.04Demura, Hirohide: 110.03,204.10Dengler, Robert: 224.04Denk, Tilmann: 200.03,214.21Denneau, Larry: 103.04, 112.01,405.01Desert, Jean-Michel: 408.05Deshapriya, Jasinghege DonPrasanna.: 509.03Desmars, Josselin: 117.11,216.03, 501.01, 501.02Deustua, Susana E.: 203.04Devi, Malathy: 416.26Devins, Spencer: 102.01, 105.05DeWitt, Curtis N.: 219.09,502.04Dhingra, Rajani: 213.10

DiBraccio, Gina A.: 505.02,505.03, 510.02Dillman, robert A.: 219.21Diniega, Serina: 400.01, 418.17DiSanti, Michael A.: 305.03,305.04, 305.09, 414.06, 414.12,414.13Doan, Baochi D.: 413.10Doan, Nhu: 214.08Dobrijevic, Michel: 209.08Dodds, Curt: 112.01Domingue, Deborah L.:Dones, Henry C (Luke).:401.01, 401.02Dong, Chuanfei: 418.02,505.02, 510.02Dong, Yao: 416.23Donnelley, Padraig: 205.02Doressoundiram, Alain: 110.08Dotson, Jessie L.: 110.18,110.19, 111.05Dougherty, Michele: 108.03Douin, Stéphane: 414.28Dove, Adrienne: 204.12Dove, Adrienne R.: 413.10Dowling, Timothy E.: 115.06,116.01, 217.02Drossart, Pierre: 115.02, 301.03Drouin, Brian J.: 416.26Drummond, Jack D.: 110.30Du, Xinnan: 208.09Duca, Simone: 422.05Duchene, Gaspard: 413.11Dufek, Josef: 416.17Duffard, Rene: 216.18, 501.01,504.08Dukes, Martin Todd.: 112.10Duncan, Andrew G.: 219.23Durand, Joelle: 415.04Durante, Daniele: 109.01,303.01, 303.03Durden, Stephen: 224.04Durech, Josef: 110.27, 208.05Dustrud, Shyanne: 301.02Dyar, Melinda: 219.06, 417.01,417.02Dyudina, Ulyana A.: 115.24,115.27, 205.11Earle, Alissa: 102.09D, 221.02Ebel, Denton: 218.01Edberg, Niklas JT.: 509.09Edgington, Scott G.: 115.20Ehlmann, Bethany: 219.22,410.01, 418.25Eichstadt, Gerald: 109.03Eichstaedt, Gerald: 205.02,205.10Eickhoff, Mark: 110.30Eigenbrode, Jennifer L.:400.06Eisner, Nora: 305.07El Moutamid, Maryame:212.02, 212.10, 501.01Elachi, Charles: 212.11, 301.03Elkins-Tanton, Linda T.:404.09DElliott, Joshua Peter.: 104.04Elrod, Meredith K.: 418.05,510.05, 510.06, 510.08, 510.09Emery, Joshua: 110.02, 110.26,208.07Emery, Joshua P.: 110.01,110.06, 110.13, 110.29, 110.34,110.35, 208.10, 210.02, 219.07

Encrenaz, Pierre: 415.03,415.05, 415.06Encrenaz, Therese: 107.01,115.02, 219.09, 415.03, 415.05,415.06, 502.04Ennico, Kimberly: 102.01,102.03, 102.06, 102.07, 102.08,102.09D, 105.04, 105.05,215.02, 215.04, 215.06, 221.01,221.02, 504.06Eparvier, Francis: 510.04Eparvier, Frank: 418.07, 510.06Erasmus, Nicolas: 204.05Ermakov, Anton: 306.01Ertel, Steve: 407.02Espley, Jared R.: 505.02,510.02Esposito, Larry: 104.04,104.09D, 207.04Esposito, Larry W.: 115.24,212.06Evans, J. Scott.: 418.06, 418.07,507.06, 510.01, 510.05,510.06, 510.07Evans, Michael W.: 212.01Ewald, Shawn: 115.27, 205.11Fabrycky, Daniel: 506.04Faggi, Sara: 305.02, 418.08Fan, Siteng: 213.04, 304.08,405.10Fane, Michael: 117.01Fang, Xiaohua: 505.03Farkas-Takács, Anikó: 216.05,504.10Farnham, Tony: 401.03,403.01, 414.10Farnocchia, Davide: 100.09,103.01, 111.08, 112.04Farrell, William M.: 406.02Fast, Kelly Elizabeth.: 507.03Faulk, Sean: 304.01, 304.02Faury, Guillaume: 415.04Fazio, Giovanni G.: 110.06Feaga, Lori M.: 414.10, 414.15,509.04, 509.06, 509.07,509.08, 509.09Feldkhun, Daniel: 224.02Feldman, Paul D.: 414.26,509.04, 509.06, 509.07,509.08, 509.09Feller, Clement: 509.03Feria, Erlan H.: 217.05Fernandes,, Joshua: 115.28Fernandez, Yanga R.: 110.15,204.02, 414.08, 414.16, 420.03Fernández-Valenzuela, Estela:216.18, 504.08Ferrante, Robert F.: 216.08Ferrari, Sabrina: 417.01Ferron, Stephane: 414.07Ferruit, Pierre: 219.10Figueroa, Liliana: 216.14, 216.15Filacchione, Gianrico: 104.07,212.04, 415.01Filwett, Rachael: 105.02Fink, Uwe: 415.01Fischer, Erik: 400.04Fitzpatrick, M. Ryleigh: 414.04Fitzpatrick, Ryleigh: 305.05Fitzsimmons, Alan: 208.06DFlandes, Alberto: 212.05Flandinet, Laurene: 416.25Flasar, F. Michael.: 205.09,213.05, 304.03, 304.04, 304.10Fleisig, Jacob: 414.23

Fletcher, Leigh: 115.05, 115.20,115.28, 205.02, 205.04, 209.04,211.02Fleury, Benjamin: 213.03Flom, Abigail: 115.06Floyd, Charmayne: 116.06Fohring, Dora: 111.02, 112.06,112.13Folkner, William: 109.01,303.03, 504.02Ford, Eric B.: 506.03, 506.04,506.06, 506.07Forget, Francois: 102.05,105.06D, 507.06, 510.07Fornasier, Sonia: 110.08,216.07, 509.03Fortney, Jonathan J.: 300.05,303.01, 303.06, 408.03,408.04, 408.05, 408.08Fossati, Luca: 416.09Fouchet, Thierry: 102.02,115.02, 209.04, 209.05,209.08Fougere, Nicolas: 414.06,415.01, 509.04, 509.05Fowler, Christopher: 510.04Fox, Jane L.: 418.06Frail, Sarah: 202.04Frantseva, Kateryna: 111.06Fraser, Wesley Cristopher.:218.08, 504.06, 504.12Frayer, David T.: 420.04Freissinet, Caroline: 400.06French, Linda M.: 110.33,416.16French, Richard G.: 104.09DFrench, Robert S.: 104.01,214.19Frerking, Margaret: 415.03,415.05, 415.06Friedson, Andrew James.:202.05DFry, Edward S.: 224.05Fry, Patrick M.: 115.17, 205.07,205.08Fu, Roger: 306.01Fujii, Yuri I.: 508.08Fujiyoshi, Takuya: 115.28,205.02Fukuhara, Tetsuya: 502.01Fulchignoni, Marcello: 110.08Fuller, Jim: 303.07Fuls, Carson: 117.07Futaguchi, Masahiko: 502.01Gabriel, Travis: 404.03Gabriel, Travis SJ.: 508.03Gaddis, Lisa: 218.01Gaehrken, Bernd: 504.08Gährken, Bernd: 200.04Gaither, Tenielle: 218.07Galanti, Eli: 109.01, 303.03Gallego, Angelina: 115.27,118.01, 205.11Gans, Bérenger: 414.28Gao, Peter: 304.08, 408.08García, Ángel: 212.05Garcia, Daniel: 205.06Garcia-Díaz, Teresa: 216.15Garcia-Muñoz, Antonio: 205.06Garland, Justin: 115.27, 118.01,205.11Garland, Ryan: 416.22Garvin, James: 219.04Gaudi, B. Scott.: 402.01Gavilan, Lisseth: 213.02

Gavino, Sacha: 506.01Gay, Pamela L.: 101.09, 116.05,119.02Ge, Huazhi: 115.28Geary, John C.: 216.14, 216.15Gellert, Ralf: 400.06Genade, Anja: 216.01, 216.02Genda, Hidenori: 104.03,406.01Gerakines, Perry A.: 202.04,216.08Gerard, Jean-Claude: 115.24,510.07Gerdes, David W.: 216.11,405.04, 405.07Gharib Nezhad, Ehsan: 416.19Ghent, Rebecca: 100.03Ghosh, Amitahba: 218.01Giampapa, Mark S.: 416.20Gibb, Erika L.: 305.03, 305.04,305.09, 414.06, 414.12, 414.13Gibbs, Alex: 117.07Gicquel, Adeline: 415.05,415.06, 509.02Giles, Rohini: 115.04, 205.04Gilli, Gabriella: 502.05Giorgini, Jon D.: 100.09,110.12, 204.01, 414.24Gladman, Brett: 216.12, 405.02,405.03, 405.12, 504.12Gladstone, Randy: 105.04,109.02, 404.08Glavin, Daniel P.: 400.06Glein, Christopher R.: 214.05,301.01Glenar, David A.: 406.02Goguen, Jay D.: 110.31Goldstein, David B.: 207.06Golubov, Oleksiy: 100.07Gombosi, T. I.: 415.01, 509.05Gomes, Rodney S.: 201.01Gomez, Edward: 110.10Gómez-Forrellad, Josep María:209.07Gonçalves, Ruben: 502.05Gondet, Brigitte: 418.21Gonzalez-Galindo, Francisco:510.07, 510.08Gorius, Nicolas: 207.01, 304.03Gough, Michael: 101.04Gough, Raina: 400.05Gould, Carolina: 413.11Graff, Paige: 116.05Granados Contreras, AguedaPaula.: 503.02DGranata, Valentina: 504.08Granvik, Mikael: 100.02,110.09, 112.01, 201.06Grassi, Davide: 205.10Grauer, Al: 117.07Grav, Tommy: 117.10, 302.03,414.16Graves, Kevin: 100.05Gray, Candace L.: 417.07,422.02Graykowski, Ariel: 511.02Grayzeck, Edwin J.: 218.01Graziano, Nancy: 101.09Greathouse, Thomas K.:109.02, 115.02, 115.04,115.05, 205.02, 209.04, 209.08,211.02, 404.08Green, Joel D.: 101.04, 219.11Green, Simon F.: 403.03D

Greenberg, Adam H.: 100.06,101.01Greenstreet, Sarah: 110.10,111.08, 116.09, 216.12Gressel, Oliver: 508.08Grey, Matthew: 219.18Grier, Jennifer A.: 116.05Griffith, Caitlin Ann.: 213.11,416.06, 421.02Grinblat, Jonny: 219.16Grinspoon, David: 417.03Gritsevich, Maria: 208.02,208.03Grodent, Denis: 115.24Groussin, Olivier: 415.04Gruesbeck, Jacob: 505.02,510.02Grundy, Will: 301.02Grundy, William M.: 102.05,102.06, 102.07, 102.08,102.09D, 110.40, 202.02,215.02, 216.06, 221.01, 221.02Gudipati, Murthy: 203.10,213.03, 214.09Guerlet, Sandrine: 209.03,209.04Guilbert, Aurelie: 219.10Guillot, Tristan: 109.01,303.03, 500.03Gulkis, Sam: 415.05Gulkis, Samuel: 415.02, 415.03,415.06Gunnarson, Jacob: 118.01,205.11, 422.02Gunnarson, Jacob L.: 115.27Gurwell, Mark A.: 102.02,216.07, 304.11Gustafsson, Annika: 110.07Gustin, Jacques: 115.24Gwyn, Stephen: 216.12, 405.02,504.12Gyalay, Szilard: 400.03Haberle, Robert: 219.03,418.14, 418.16Hadden, Sam: 216.09, 405.08Hadland, Nathan: 115.19Haghighipour, Nader: 419.04,508.02Hahn, Joseph M.: 104.02,501.03Hahn, Matthias: 509.01Hainaut, Olivier: 305.01,420.02Halekas, Jasper: 418.02,505.02, 510.02, 510.03Hamel, Mark: 105.02Hamill, Patrick: 401.02Hamilton, Douglas P.: 104.02,214.21, 215.04, 419.01, 501.03,508.01Hamilton, Gary: 212.11Hamilton, Stephanie: 405.04,405.07Hamilton, Victoria E.: 110.01,110.02Hand, Kevin: 203.04Hand, Kevin P.: 203.01,219.04Hanley, Jennifer: 301.02Hansen, Candice: 109.03,118.01, 205.02, 205.10,207.04, 418.17, 422.05Hansen, Kenneth C.: 415.01,509.05

Hanus, Josef: 110.27, 208.04,208.05Hapke, Bruce W.: 203.09Hara, Takuya: 505.02, 505.03Harada, Yuki: 505.02, 505.03Harbison, Rebecca A.: 212.03Harmon, John K.: 305.06Harper, Chad: 214.08Harrington, Joseph: 402.04,416.01, 416.02, 416.03, 416.04Harrington, Olga: 414.17,420.01Harris, Alan: 110.06Harris, Alan William.: 100.01,204.02Harris, Ien: 414.09Harris, Walter M.: 305.05,305.06, 414.04, 414.24Hartogh, Paul: 209.08, 415.03,415.05, 415.06Harvey, Ralph: 113.01Hasegawa, Yasuhiro: 508.10Hashimoto, George L.: 417.08,502.01, 502.02Hasselmann, Pedro H.: 509.03Hatcher, Chase: 418.19Häusler, Bernd: 417.07, 418.04,502.03, 509.01Hawley, C. Luke: 110.01Hay, Hamish: 203.11Hayashi, Yoshi-Yuki: 115.11,418.24Hayes, Alexander: 213.08,304.09, 304.12DHayne, Paul O.: 203.03Hayward, Rose: 218.07He, Chao: 300.01, 300.02,416.25He, Matthias Yang.: 506.03,506.06Heays, Alan: 414.28Hedman, Matthew M.: 104.06,104.07, 104.09D, 212.01,212.02, 212.04, 212.09, 213.10Heinze, Aren: 103.04Helbert, Joern: 219.06, 417.01,417.02Helled, Ravit: 109.01, 303.01,303.03Hellmich, Stephan: 504.08Henderson, Bryana: 203.10Hendrix, Amanda: 207.04,511.01Hendrix, Amanda R.: 203.06,210.03, 220.02, 404.08Henneken, Edwin A.: 223.02Henning, Wade: 207.03,507.03Henrici, Andrew: 414.25Hensley, Scott: 219.06Herique, Alain: 415.08Hernández, Benjamín: 216.14,216.15Hernández-Águila, JoannesBosco.: 216.15Hersant, Franck: 209.08Hesman, Brigette E.: 205.09Hesselbrock, Andrew: 508.06Hestroffer, Daniel: 117.11Heuer, Steven: 210.06Hewagama, Tilak: 205.05,507.03Hibbitts, Charles A.: 214.07,219.07, 417.10Hickson, Kevin: 414.28

Hidayat, Taufiq: 304.11Hillier, John K.: 105.05Himes, Michael D.: 402.04,416.03Hinkle, Mary: 204.02, 204.04Hinse, Tobias: 221.04Hinson, David: 215.07Hinson, David P.: 105.04,418.04Hintz, Eric G.: 416.11Hinz, Philip: 407.02Hirabayashi, Masatoshi:100.05, 117.03Hirata, Naru: , 110.03, 204.10Hirtzig, Mathieu: 301.03Hoang, Van Hong.: 509.03Hockney, George M.: 112.14Hodyss, Robert: 216.16Hoffmann, Harald: 214.07Hoffmann, Holger: 104.05Hofgartner, Jason D.: 102.01Hofstadter, Mark: 415.02,415.03, 509.02Hofstadter, Mark D.: 415.05Hogancamp, Joanna C.:400.06, 418.22Holler, Bryan J.: 215.02,216.17, 219.10Hollingsworth, Jeffery L.:418.13, 418.14Holman, Matthew J.: 103.01,112.14, 216.09, 405.08Holsclaw, Greg: 418.06, 507.06,510.06, 510.07Holstein-Rathlou, Christina:418.12Holt, Timothy: 511.03Honda, Mitsuhiko: 414.01Hong, Sukbum A.: 417.19Hood, Noah: 110.16Hope, Drew J.: 219.21Hopp, Ulrich: 504.08Hora, Joseph L.: 110.06, 110.07,204.05Horanyi, Mihaly: 110.16,404.06Horner, Jonti: 221.04, 511.03Hornoch, Kamil: 504.08Hornung, Danae: 218.04Horst, Sarah: 300.01, 300.02,310.01, 416.25Horvath, Sarah: 416.24Houston, Stephen: 211.02Howard, Alan D.: 102.03,102.08Howell, Ellen S.: 110.01, 110.12,110.15, 204.02, 208.10, 305.05,305.06, 414.04, 414.24,420.04Howell, Robert R.: 214.02Howell, Samuel M.: 214.23Howett, Carly: 102.09D,203.03, 207.01, 210.04,220.02, 221.02, 224.02, 224.05Hsieh, Henry H.: 305.10Hsu, Danley: 506.06, 506.07Hsu, Hsiang-Wen: 110.16Huang, Chenliang: 421.03Huang, Chung-Kai: 216.14,216.15Huang, Hsin-Hua: 220.05Huang, Zhenguang: 415.01,509.05Hubbard, William B.: 109.01,303.01, 303.03

Huber, Lyle: 218.03, 218.04Hubert, Benoît: 510.07Hudson, Reggie L.: 202.04,216.08Hue, Vincent: 105.02, 109.02,209.08Hueso, Ricardo: 205.02,205.06, 209.07Hughes, Anna: 416.12Hughes, John S.: 223.01Hui, Man-To: 208.09Hull, Robert: 115.08Hung, Denise: 111.02, 112.06,112.13Hurford, Terry: 203.07, 207.02,207.03, 210.04Hurley, Dana: 404.01, 404.08Hurst, Ken: 219.16Husker, Allen: 220.05Hutsemekers, Damien: 305.01Hwang, Jason: 506.02Hyodo, Ryuki: 104.03, 406.01Ida, Shigeru: 413.09, 508.09Iess, Luciano: 109.01, 303.03Ignácz, Bernadett: 216.05,504.10Imamura, Takeshi: 422.02,502.01Imanaka, Hiroshi: 105.01Inasawa, Tomoki: 110.03,204.10Ingersoll, Andrew P.: 102.04,109.04, 115.09, 115.27,205.02, 205.10, 205.11, 205.12,303.03Ip, Wing-Huen: 114.01, 216.12,415.03, 415.05, 415.06Irwin, Patrick: 205.04, 211.02,304.04, 304.06, 304.07,416.22, 502.04Ishiguro, Masateru: 305.10Ishioka, Keiichi: 115.11Ishiwatari, Masaki: 115.11,418.24Ito, Kenji: 414.28Ivanov, Boris A.: 214.06Ivanova, Oleksandra: 414.02Ivezic, Zeljko: 103.05, 117.09Izidoro, André: 201.01Jackson, Alan: 404.03,404.09D, 508.03Jackson, Brian: 119.01, 507.04Jacobson, Robert Arthur.:214.15Jacobson, Seth A.: 110.24,117.03, 302.05Jain, Sonal: 418.03, 418.06,418.07, 507.06, 510.01,510.03, 510.06, 510.07Jakosky, Bruce: 418.02, 418.03,418.06, 505.02, 507.06, 510.06,510.07, 510.08James, David: 110.33Janches, Diego: 422.03Janssen, Michael A.: 205.02,211.03, 212.11, 301.03, 301.04,415.03, 415.05, 415.06Jao, Joseph: 204.01Jarchow, Christopher: 209.08,415.03, 415.05, 415.06Jarmak, Stephanie: 204.12Jaumann, Ralf: 214.06, 214.07Jedicke, Robert: 100.02,112.01, 117.04, 208.06D,405.01

Jehin, Emmanuel: 305.01Jennings, Donald E.: 213.05,221.02, 304.10Jensen, Elizabeth: 117.01Jensen, Elsa: 109.03Jensen, James: 404.07Jeong, Minsup: 417.19Jerousek, Richard Gregory.:104.09DJessup, Kandis-Lea: 105.02,417.06Jewitt, David: 112.11, 208.08,208.09, 511.02Jia, Xianzhe: 211.01, 219.18Jia, Ying-Dong: 114.01Johnson, Brandon C.: 404.04DJohnson, Jess A.: 117.07Johnson, Joni J.: 218.03,218.04Johnson, Paul: 216.16Johnson, Perianne: 115.05,205.01Johnson, Robert E.: 203.12D,418.05Jolitz, Rebecca: 418.02Jolly, Antoine: 304.04Joner, Michael D.: 402.01,416.11Jones, R.: 103.05, 117.09Jontof-Hutter, Daniel: 506.04Jouchoux, Alain: 115.24Journaux, Baptiste: 222.01Joyce, Colin J.: 406.02Juaristi-Campillo, Jon: 209.07Jubier, Xavier: 417.17Juric, Mario: 103.05, 117.09Kaasalainen, Mikko: 208.05Kahre, Melinda A.: 418.13,418.14, 418.16Kaib, Nathan A.: 401.01,508.04Kammer, Joshua: 105.02,105.04, 221.03Kappel, David: 417.01, 417.02Karajeh, Zaid S.: 106.02Kareta, Theodore: 415.06Karkoschka, Erich: 301.06Karner, James: 113.01Karpouzas, Konstantinos:402.06DKasaba, Yasumasa: 115.28,205.02, 211.02, 417.08Kasper, Justin C.: 219.18Kaspi, Yohai: 109.01, 303.03,416.21Kass, David M.: 510.08Kataria, Tiffany: 408.05,408.07Kavelaars, J. J.: 216.12,405.02, 405.12, 504.12Kawaguchi, Jun'ichiro: 204.10Kawakita, Hideyo: 305.03,305.04, 305.09, 414.01, 414.06,414.12, 414.13Keane, Jacqueline: 305.01,420.02Keane, James Tuttle.:404.04DKedar, Sharon: 220.05Keeney, Brian A.: 509.04,509.06, 509.07, 509.08,509.09Kelland, John: 304.09,304.12D

Keller, Horst Uwe: 415.02,509.03Keller, Lindsay P.: 117.01Kelley, Michael S.: 208.11D,401.03, 403.01, 414.15, 414.16Kelley, Michael S. P.: 302.01,414.11Kempf, Sascha: 214.09Kempton, Eliza: 300.02,408.05Kenney, Jessica: 101.05Kenyon, Scott: 508.07Kerber, Laura: 214.02Keys, Sonia: 103.01Khain, Tali: 216.11, 405.07Khurana, Krishan: 108.03,219.18Kikwaya Elou, Jean-Baptiste:305.05Kikwaya Eluo, Jean-Baptiste:414.04Killen, Rosemary M.: 417.13Kim, Cindy: 219.18Kim, Il-hoon: 417.19Kim, Sang J.: 213.06, 417.18Kim, Sungsoo S.: 417.19Kim, Yoonyoung: 305.10Kipping, David M.: 421.04Kirchoff, Michelle: 214.17Kiselev, Nikolai: 414.02Kisiel, Zbigniew: 304.07Kiss, Csaba: 216.05, 504.08,504.10Kitazato, Kohei: 110.03,204.10, 219.07Kivelson, Margaret G.: 211.01,219.18, 308.01Klassen, David R.: 116.08,418.14Klesh, Andrew: 418.25Kleyna, Jan: 112.01, 420.02Kling, Alexandre: 418.16Knight, Katherine I.: 221.01Knight, Matthew M.: 305.07,305.10, 401.03, 414.15,509.04, 509.06, 509.07Knowles, Benjamin: 408.02Knutson, Heather: 408.06,408.07Kobayashi, Hiroshi: 508.08Kofman, Woldek: 415.08Kokotanekova, Rosita:403.03DKolasinski, John R.: 507.03Kolokolova, Ludmilla: 414.02Komacek, Thaddeus D.:408.09DKomzík, Richard Milan: 504.08Kong, Dali: 115.22, 303.02Kopparla, Pushkar: 416.18Korth, Haje: 214.09, 219.18Korycansky, Donald: 115.18Koschny, Detlef: 204.08,415.02Koskinen, Tommi: 115.21,209.03, 408.01Kospal, Agnes: 504.10Kostiuk, Theodor: 507.03Koutas, Nikko: 115.19Kouyama, Toru: 502.01Kowalski, Richard: 117.07Kramer, Emily A.: 117.10,302.03, 414.16, 420.03Kreidberg, Laura: 300.05,300.06

Kretlow, Mike: 501.01Kroner, Desire: 203.09Krupp, Norbert: 219.18Kubyshkina, Darya: 416.09Kuehn, David M.: 115.08Kuhn, Olga: 204.07Kurth, William S.: 104.06,109.02Kutsop, Nicholas: 105.05Lacerda, Pedro: 208.06D,403.03DLacy, John H.: 115.02Lai, Ian: 114.01Lai, James: 304.07Lambert, Diane: 204.09Lambrechts, Michiel: 500.05Lamy, Laurent: 115.24Lamy, Philippe: 415.02Lamy, Philippe L.: 415.04Landsman, Zoe A.: 117.01Langevin, Yves: 418.21Lantz, Cateline: 110.08, 110.09Lara, Luisa: 304.11Larsen, Jeff: 112.08Larson, Jennifer: 111.01Larson, Stephen M.: 110.10,117.07, 208.08Lastra, Nathan: 414.17, 420.01Lasue, Jeremie: 415.08Lauer, Tod R.: 102.01, 102.03,102.08, 215.04Lauretta, Dante: 110.01, 110.02Lavvas, Panayiotis: 408.01Law, Emily: 218.01Lawler, Samantha: 216.12Lawrence, Kenneth J.: 204.01,301.03Lawton, Brandon L.: 101.04Le, Tianhao: 115.26Le Beau, Raymond P.: 115.19Le Corre, Lucille: 110.05,110.23, 219.07Le Gall, Alice: 215.03, 301.03,301.04Le Mouélic, Stephane: 104.07,213.09, 301.03Leblanc, Francois: 203.12D,422.01Lebofsky, Larry A.: 116.06Lebonnois, Sebastien: 304.03,502.05Leclercq, Ludivine: 418.05Lederer, Susan M.: , 117.01Lee, Christina: 418.02, 510.02Lee, Christopher: 507.05Lee, Clement: 204.01Lee, Dong Wook: 417.18Lee, Regina SK.: 219.03Lee, Seungwon: 415.02, 415.03,415.05, 415.06Lee, Yeon Joo: 417.08Lefevre, Franck: 418.06,507.06, 510.06, 510.07Lehan, Cory: 116.05Lehner, Matthew: 216.14,216.15, 504.12Leisenring, Jarron: 407.02Leiva, Rodrigo: 216.03, 216.07,501.01, 501.02Lejoly, Cassandra: 110.12,305.05, 305.06, 414.04, 414.24Lellouch, Emmanuel: 102.02,209.05, 209.08, 209.09,214.20, 216.07, 304.11, 415.03,415.05, 415.06

Leonard, Erin Janelle.: 220.03Leonard, Gregory J.: 117.07Lethuillier, Anthony: 415.03Leung, Cecilia: 507.08Levasseur-Regourd, A.: 415.08Levin, Steven: 109.01, 109.02,303.03Levine, Stephen: 216.01, 216.02Levison, Harold F.: 110.40,401.01, 500.04Lewis, Briley Lynn.: 215.02Lewis, Corbin: 213.07Lewis, Mark C.: 220.01Lewis, Nikole: 300.01, 300.02,408.05, 416.25Leyrat, Cedric: 215.03, 415.03,415.05, 415.06Li, Cheng: 115.26, 205.02,205.10, 205.12, 304.08Li, Daohai: 511.04DLi, Jian-Yang: 110.05, 403.02Li, Jing: 208.08, 219.21Li, Rixin: 500.06Li, Zhi-Yun: 421.03Liang, Mao-Chang: 213.04,417.21Licandro, Javier: 117.08Lillis, Rob: 418.02Lilly, Eva: 100.04, 208.06DLilly (Schunova), Eva: 112.10,405.01Lim, Lucy F.: 110.02, 110.25,110.29Lin, Hsing Wen: 216.12Lin, Min-Kai: 500.06Lin, Zhong-Yi: 305.10Lindberg, Gerrick: 301.02Linder, Tyler R.: 112.12Lindsay, Sean S.: 110.26,110.34, 117.01, 208.07Line, Michael R.: 408.04,408.05, 416.19Linscott, Ivan: 215.07, 221.02Lintott, Chris J.: 422.05Lipple, Brock: 507.04Lis, Dariusz C.: 102.02Lissauer, Jack J.: 104.01,214.19, 506.01, 506.04Lisse, Casey M.: 414.16, 500.01Lister, Tim: 110.10, 111.08,216.01, 216.02Liu, Yang: 404.08Liuzzi, Giuliano: 507.01,507.02Livengood, Timothy A.: 507.03Lo, Daniel: 418.06, 507.06,510.06Lo, Daniel Y.: 510.07Lockman, Felix J.: 420.04Loison, Jean-Christophe:414.28Lombardi, James C.: 506.02Lombardo, Nicholas: 304.04Longaretti, Pierre-Yves: 212.10Lopes, Rosaly MC.: 213.11,214.02, 301.03Lopez, Eric: 300.06Lopez-Moreno, Jose: 507.01,507.02Lora, Juan: 304.01Lora, Juan M.: 304.02,304.12DLorenz, Ralph: 113.01, 207.05,215.03, 219.02, 220.05, 507.04Lorenzi, Vania: 117.08, 208.07

Lovell, Amy J.: 420.04Luan, Jing: 303.07Lucas, Michael P.: 208.07Luhmann, Janet: 505.02,505.03, 510.02Lumpe, Jerry: 510.06Lunine, Jonathan I.: 109.01,214.09, 303.03, 304.12DLunsford, Allen: 221.02Luspay-Kuti, Adrienn: 105.02Luszcz-Cook, Statia H.: 205.03Lykawka, Patryk S.: 216.12Lyons, James R.: 416.19Ma, Yingjuan: 505.01, 505.02,505.03, 510.02Ma, Yuehua: 111.10Mace, Mikayla: 116.06Machado, Pedro: 502.05Maciel, Ricardo: 305.05, 414.04MacKenzie, Shannon: 213.09Maclay, Matthew: 418.17MacLennan, Eric M.: 110.26,208.07Madigan, Ann-Marie: 414.23Maestripieri, Martina: 504.08Magana, Lizeth O.: 414.26Maggard, Steven: 501.05Magri, Christopher: 110.15Mahaffy, Paul R.: 400.06,510.05, 510.06, 510.08, 510.09Mahieux, Arnaud: 207.06Maindl, Thomas: 508.02Maindl, Thomas I.: 419.04Mainzer, Amy K.: 103.03,117.10, 219.01, 302.03, 414.16,420.03Mäkinen, Terhi: 414.07Malaska, Michael: 301.03Malhotra, Renu: 201.04,204.07, 405.11Manatt, Kenneth S.: 203.09Mandell, Avi: 203.07Mandt, Kathleen: 105.02,224.05, 404.08Manfroid, Jean: 305.01Mankovich, Chris: 303.01Mankovich, Christopher:303.06Mannel, Thurid: 415.08Mantz, Arlan: 416.26Mao, Xiaochen: 306.03Maquet, Lucie: 501.01Marchi, Simone: 306.02Marchis, Franck: 208.04,208.05Marcq, Emmanuel: 417.01,417.02Marcucci, Emma: 101.05Marcus, Philip: 118.04Marengo, Massimo: 500.01Margot, Jean-Luc: 100.06,101.01, 214.10Markham, Stephen: 303.04Markkanen, Johannes: 110.22,110.42, 208.02Marley, Mark S.: 303.06,408.08Marouf, Essam A.: 104.09DMarsden, Stephen: 221.04Marshall, David P.: 217.02Marshall, Sean E.: 110.15,204.02Marsset, Michael: 208.04,208.05, 504.12

Martikainen, Julia: 208.02,208.03Martin, Audrey: 110.34Martin, Peter: 400.06Martin, Trevor: 416.11Martin-Lagarde, Marine:209.04Martinelli, Fabio: 504.08Martinez, Antoine: 418.21Martinez, German: 400.04Martins-Filho, Walter: 416.06Marton, Gabor: 216.05Marzari, Francesco: 504.08Masci, Frank J.: 103.03Masiero, Joseph R.: 110.32,117.10, 302.03, 414.16, 420.03Mason, John: 224.05Mastaler, Ron: 112.08Matcheva, Katia: 213.12Mathé, Christophe: 213.01Matheny, Rose: 117.07Mathias, Donovan: 106.01,110.17, 110.18, 110.19, 111.05Matsoukas, Christos: 301.03Matsumoto, Toru: 417.20Matsumura, Soko: 413.09,508.09Matsuyama, Isamu: 203.11,404.04DMaturilli, Alessandro: 417.01Mauk, Barry: 109.02Mawet, Dimitri: 408.07Mayo, Louis: 101.02, 116.10Mayyasi-Matta, Majd A.:418.03, 418.07, 510.03, 510.06Mazarico, Erwan: 404.08Mazelle, Christian: 505.03Mazrouei, Sara: 100.03Mazur, Eric: 304.05Mazzei, Leonardo: 504.08McAdam, Margaret M.:208.11D, 302.01McCabe, Ryan M.: 115.27,118.01, 205.11, 422.02McCabe, Tyler: 115.18McCarthy, Donald W.: 116.06McClintock, William E.: 418.06,507.06, 510.06, 510.07McComas, Dave: 105.04McCord, Thomas: 306.01McDonald, George: 300.06McElwaine, Jim: 418.17McEwen, Alfred: 301.06McGouldrick, Kevin: 422.02McGrath, Melissa: 203.04,203.06McGraw, Allison M.: 110.23McGraw, Lauren: 110.13McGuiggan, Patricia: 300.01McIntyre, Kathleen: 416.01McKay, Adam: 305.09, 414.15McKay, Adam J.: 305.03,305.04, 414.06, 414.12McKay, Christopher P.: 400.06McKemmish, Laura: 402.06DMcKinnnon, William B.: 102.03McKinnon, William B.: 102.08,203.02, 214.05, 215.02, 221.01,306.03McLean, Will: 115.15McMahon, Jay: 111.11McMahon, Jay W.: 111.09McMaster, Adam: 422.05McMillan, Robert S.: 112.08McNeill, Andrew: 208.06D

McNutt, Ralph L.: 218.01,219.18Medina, Richard: 509.04,509.06, 509.08Meech, Karen Jean.: 305.01,414.16, 420.02Meinke, Bonnie K.: 101.04,101.05, 101.06, 116.08, 219.11Meirion-Griffith, Gareth:203.08Mekarnia, Djamel: 500.03Mellon, Michael: 203.03Mendez, Joshua: 416.17Mendonca, Joao: 417.21Merlin, Frederic: 110.08,214.20Meza, Erick: 501.01Micciche, Anthony: 420.01Michel, Patrick: 100.02Micheli, Marco: 100.04,100.09, 305.10, 420.02Migliorini, Alessandra: 415.01Mignard, Francois: 103.06Miguel, Yamila: 109.01, 303.03Mikuz, Herman: 504.08Milani, Andrea: 103.06Milby, Zachariah: 510.07Milewski, Dave Gerald.: 112.11Militzer, Burkhard: 109.01,303.01, 303.03Miller, Grant RM.: 422.05Miller, Kelly E.: 301.01Millholland, Sarah: 405.08Mills, Franklin P.: 417.06Ming, Douglas W.: 400.06Minton, David A.: 100.05,508.06Mischna, Michael A.: 507.05Mitchell, Adriana: 305.05Mitchell, Adriana Macieira.:414.04Mitchell, David: 505.02, 505.03Mitchell, Jonathan: 304.01,304.02, 304.12D, 417.05Miura, Akira: 204.10Moeckel, Chris: 211.03Moeyens, Joachim: 103.05,117.09Mojzsis, Stephen: 413.09,508.09Molaro, Jamie: 100.05, 203.01,203.08Molter, Ned: 304.06, 304.07Molyneux, Philippa M.: 203.06,224.05Momary, Thomas W.: 109.03,115.16, 115.20, 115.28, 205.02,205.07, 205.10Mommert, Michael: 110.06,110.07, 117.04, 204.04, 204.05Monje, Raquel: 224.04Monteiro, Filipe: 110.38Montiel, Edward J.: 219.09Montmessin, Franck: 418.06,507.06, 510.06, 510.07Moor, Attila: 504.10Moore, Jeffrey M.: 102.03,102.05, 102.06, 102.08, 215.06,221.01Moore, Luke: 422.01Moore, Thomas Z.: 224.05Moores, John: 101.08, 219.03Moorhead, Althea V.: 106.03Morales, Kimberly Marie.:400.01, 418.17

Morales, Nicolas: 216.18,501.01, 504.08Morales-Juberias, Raul: 115.04,115.05Moran, Sarah E.: 416.25Morate, David: 117.08Morbidelli, Alessandro: 100.02,110.09, 201.01, 201.02, 201.03,208.12D, 401.01Morello, Giuseppe: 402.06DMoreno, Raphael: 102.02,209.08, 209.09, 216.07,304.11Morgan, Thomas H.: 218.01,417.13Moriconi, Maria Luisa.: 205.10Morishima, Ryuji: 104.08,508.10Morley, Caroline: 300.05,408.04, 408.05, 408.08Morooka, Michiko: 210.06Morris, Richard V.: 400.06Moses, Julianne I.: 209.06,300.01, 300.02, 416.25Mosher, Joel A.: 105.05Moskovitz, Nicholas: 110.24,110.25, 117.05, 204.04, 305.10Mottola, Stefano: 214.21,504.08Moullet, Arielle: 102.02,209.09, 216.07, 304.11Movshovitz, Naor: 303.01,303.06MU69 Occultation Team, NewHorizons: 504.01Mueller, Beatrice E A.: 305.05,305.06, 414.04, 414.24, 414.25Mueller, Michael: 110.06,110.29, 111.06Mueller, Nils: 417.01, 417.02Muinonen, Karri: 110.22,110.42, 208.02, 208.03Müller, Thomas: 216.07, 504.10Müller-Wodarg, Ingo: 418.01Mumma, Michael J.: 203.07,304.07, 305.02, 414.14, 414.19,418.08, 507.01, 507.02Munson, Neal Douglas.:506.03Mura, Alessandro: 205.10Murph, Susan: 101.09Murphy, Jim: 418.15, 418.16murray, alex: 219.16Murray, Alison: 219.04Murray-Clay, Ruth: 216.12Mutchler, Maximilian J.:208.08Myers, Jonathan Ashley.:103.05Myers, Sam: 416.24Myhrvold, Nathan: 117.06Nagy, Andew: 505.01Nahon, Laurent: 213.02, 414.28Naidu, Shantanu P.: 112.04,204.01Najita, Joan R.: 419.02Nakajima, Kensuke: 115.11,418.24Nakakushi, Takashi: 502.02Nakamura, Masato: 502.01Nakauchi, Yusuke: 219.07,417.20Nascimbeni, Valerio: 504.08Natraj, Vijay: 416.18

Navarro-González, Rafael:400.06Navarro-Meza, Samuel: 117.04Neakrase, Lynn: 218.03,218.04Neamati, Daniel: 400.04Nebedum, Adaze: 203.09Neish, Catherine: 213.11,301.04Nelson, Robert M.: 203.09Nerli, Luca: 504.08Nesvorny, David: 100.02,201.01, 401.01, 401.02, 421.04,511.03Newman, Claire E.: 418.23,507.05, 507.07Newmiller, Cordell: 219.09Nicholson, Philip D.: 104.07,104.09D, 115.16, 205.07,212.01, 212.02, 212.03, 212.04,212.10, 213.09Nield, Joanna: 418.17Nikitin, Andrei V.: 416.26Nimmo, Francis: 102.05,203.03Nishizawa, Seiya: 418.24Nixon, Conor A.: 213.01,213.05, 304.04, 304.06, 304.07Nna-Mvondo, Delphine: 304.10Noe Dobrea, Eldar Zeev.:400.03Nolan, Michael C.: 110.12,110.15, 414.24Noll, Keith S.: 110.40, 210.03,504.07Noonan, John: 509.04, 509.06,509.07, 509.09Nordheim, Tom: 214.18Norton, Timothy: 216.14, 216.15Nosowitz, Jonathon: 418.09Novak, Robert E.: 418.08,418.09Nowicki, Keith: 224.02, 224.05Nugent, Carrie: 117.10, 420.03Nugent, Carrie R.: 103.03,414.16Obuse, Kiori: 115.12Ochoa, Vicente: 418.17Ochoa, Vincent: 400.01Odaka, Masatsugu: 418.24Ohtsuki, Keiji: 104.03Oldroyd, William Jared.:113.01Olkin, Catherine: 102.01,102.03, 102.06, 102.07, 102.08,102.09D, 105.04, 105.05,215.02, 215.04, 215.06, 221.01,221.02, 221.03Ootsubo, Takafumi: 414.01Opitom, Cyrielle: 305.01Orthous-Daunay, Francois-Regis: 416.25Ortiz, Jose Luis: 216.18, 501.01,501.02, 504.08, 504.09Orton, Glenn: 115.04, 205.05,211.02Orton, Glenn S.: 109.03, 115.05,115.28, 118.01, 118.04, 205.01,205.02, 205.04, 205.10,209.04Oschlisniok, Janusz: 502.03Owens, Ryan: 116.05Oza, Apurva V.: 203.12DPaetzold, Martin: 417.07,418.04, 509.01

Paganelli, Flora: 218.01Paganini, Lucas: 203.07,305.02, 414.19Paige, David A.: 413.01Pál, András: 504.08, 504.10Palafox, Leon: 421.02Palmer, Eric: 204.09Palmer, Maureen Yukiko.:304.07, 414.14Palotai, Csaba J.: 115.06,115.18, 115.19, 421.01Palumbo, Pasquale: 214.06Panning, Mark: 220.05Pappalardo, Robert T.: 214.08,214.09, 214.23Parish, Helen: 417.05Parisi, Marzia: 109.01, 303.03Park, Ryan: 306.01Parker, Alex: 100.03, 221.02,504.01, 504.02, 504.03,504.05, 504.07Parker, Alex Harrison.:102.09D, 504.04Parker, Joel Wm.: 509.04,509.06, 509.07, 509.08, 509.09Parkinson, Chris: 209.02Parmentier, Vivien: 402.03Parteli, Eric: 102.05Pasachoff, Jay M.: 101.03,200.04, 417.17Patel, Manish: 507.01, 507.02Patterson, G. Wes.: 404.08Patterson, Gerald Wesley.:404.07Patthoff, Alex: 214.08Patthoff, Donald Alex.: 220.03Paty, Carol: 214.09, 219.18Pätzold, Martin: 502.03Payne, Matthew: 216.09Payne, Matthew J.: 103.01,405.08Pearce, Logan: 301.02Pearson, Kyle: 416.06Pearson, Kyle Alexander.:421.02Pelzman, Charles: 224.03Pendleton, Yvonne J.: 210.05Penteado, Paulo F.: 213.11Penttilä, Antti: 110.22, 110.42,208.02, 208.03Pepper, Joshua: 402.01Peralta, Javier: 422.02Pereira, Mario: 117.02Perera, Viranga: 404.03,404.09DPerets, Hagai B.: 508.05Perez-Hoyos, Santiago: 205.06,418.10Perna, Davide: 110.08Pernot, Pascal: 213.02Perry, Jason: 301.06Perry, Mark E.: 209.01Person, Michael J.: 216.01,216.02Persoon, Ann: 210.06Peter, Kerstin: 417.07, 418.04Petit, Jean-Marc: 216.12,405.02, 405.12, 504.12Petroy, Shelley: 219.24Petry, Catherine E.: 103.05Pettit, Erin: 219.19Pfueller, Enrico: 504.06Philippe, Sylvain: 301.03Phillips, Cynthia B.: 203.01,203.08, 214.16

Pichardo, Bárbara: 117.04Pierce, Donna M.: 414.09Pike, Rosemary E.: 504.12Pike, William T.: 220.05Pilinski, Marcin: 510.04Pineau, Jon: 509.04, 509.06,509.08Pinilla-Alonso, Noemí: 117.08,208.07, 210.02Piqueux, Sylvain: 203.03Pla-Garcia, Jorge: 507.08,507.09DPlane, John: 510.01Podmore, Hugh: 219.03Pohl, Leos: 208.01Pokorny, Petr: 422.03Polishook, David: 110.24,204.04Popescu, Marcel: 110.08Poppe, Andrew R.: 209.06Porter, Simon Bernard.: 215.04,504.01, 504.02, 504.03,504.04, 504.05, 504.06, 504.07Portyankina, Ganna: 207.04,418.19, 422.05Potter, Andrew: 417.13Poulet, Francois: 418.21Powell, Kathryn: 218.01Pravec, Petr: 110.15, 504.08Presler-Marshall, Brynn A.:420.04Prettyman, Thomas H.: 306.01,306.04Prialnik, Dina: 414.21Pribulla, Theodor: 504.08Primm, Katherine: 400.05Proffitt, Charles R.: 219.10Protopapa, Silvia: 102.07,215.02, 216.17, 221.02, 414.06,414.10, 414.11Proudfoot, Benjamin: 501.04Pryor, Wayne R.: 115.24,404.01Psarev, Vladimir: 203.09Quadery, Abrar H.: 413.10Quan-Zhi, YE: 305.11Quataert, Eliot: 303.07Quémerais, Eric: 414.07Quillen, Alice C.: 111.10Quinones, John: 203.09Quintana, Elisa V.: 224.06Quirico, Eric: 214.20Rabinowitz, David L.: 216.06Rabson, David: 420.01Rackham, Benjamin V.: 416.20Radebaugh, Jani: 102.05,113.01, 213.07, 213.10, 214.02,218.06, 301.03Radioti, Aikaterini: 115.24Rafkin, Scot CR.: 507.08Ragozzine, Darin: 501.04,501.05, 501.06, 506.03,506.06, 506.07Ramanjooloo, Yudish: 111.02,112.06, 112.13Rasio, Frederic A.: 506.02Rathbun, Julie A.: 203.03,214.09, 407.01Raugh, Anne C.: 218.01,223.01Raulin, Francois: 304.10Rauscher, Emily: 408.05Raut, Ujjwal: 203.06, 224.05Ravine, Michael: 109.03Raymond, Alexander: 304.05

Raymond, Carol Anne.: 214.09,219.22, 306.01Raymond, Sean N.: 508.04Reach, William T.: 224.01,504.06Read, Mike: 112.08Read, Peter L.: 115.10, 205.10Reddy, Vishnu: 110.05, 110.15,110.23, 204.07, 208.07Reese, Daniel: 109.01Rehnberg, Morgan: 212.06Reid, Sarah E.: 420.04Reiheld, Alison: 101.09Reinhard, Matthew: 416.02Renner, Stefan: 501.01Renno, Nilton O.: 400.04Retherford, Kurt D.: 203.06,214.09, 221.03, 224.02,224.05, 404.08, 414.26Reuter, Dennie: 102.07,102.09DReuter, Dennis: 110.01, 221.02Rey, Michael: 416.26Reyes-Ruiz, Mauricio: 117.04,216.14, 216.15Reynolds, Odell: 110.30Rezac, Ladislav: 209.08,415.03, 415.05, 415.06Rhoden, Alyssa R.: 207.02,207.03Rich, Robert Michael.: 112.11Richardson, John D.: 214.13Richardson, Mark I.: 418.23,507.07Richardson, Mark Ian.: 507.05Richardson, Matthew: 116.05Richter, Matthew: 219.09,502.04Rickman, Hans: 415.02Rieger, Samantha: 100.08Ries, Christoph: 504.08Rimlinger, Thomas: 104.02,501.03Rinaldi, Giovanna: 415.01Ristic, Bojan: 507.01, 507.02Riu, Lucie: 418.21Rivera, Isabel: 420.01Rivera, Javier: 116.09Rivera-Valentin, Edgard G.:100.09, 110.12, 112.09, 204.02,214.17, 305.06, 400.05, 414.24Rivkin, Andrew S.: 110.13,110.29, 208.10Roark, Shane: 219.24Roatsch, Thomas: 214.06Robbins, Stuart J.: 116.05,401.02Roberts, James: 214.09,214.16, 220.04Robertson, Darrel: 106.01Robinson, Tyler D.: 300.05Rocchetto, Marco: 402.06DRodrigo, Rafa: 415.02Rodriguez, Sebastien: 213.09,301.03, 304.09, 304.12DRodriguez Sanchez-Vahamonde, Carolina: 204.02,214.17, 305.06, 414.24Roe, Henry G.: 301.02Rogers, A. Deanne.: 418.20Rogers, John: 109.03, 205.02,205.10Rogoszinski, Zeeve: 508.01Rohl, Derrick: 110.33

Roig, Fernando Virgilio.:421.04Rojas, Jose Felix: 209.07Rojo, Patricio: 304.12DRoman, Anthony: 116.08Romanishin, William: 302.02Romeuf, David: 415.04Rommel, Flavia: 504.08Rosenberg, Eric: 414.21Rosenblatt, Pascal: 406.01Rosenbush, Vera K.: 414.02Rosser, Joshua David.: 414.16,420.03Rossi, Gustavo: 216.03, 501.01,504.08, 504.09Roth, Lorenz: 203.06, 203.07Roth, Nathan: 305.03, 305.04,414.06Roth, Nathan X.: 305.09,414.12Roussos, Elias: 219.18Royer, Emilie M.: 220.02Rozehnal, Jakub: 110.41Rozitis, Ben: 110.02Rubanenko, Lior: 413.01Rubin, Martin: 509.05Ruesch, Ottaviano: 306.01Ruffini, Nicholas: 420.01Rufu, Raluca: 508.11DRuhunusiri, Suranga: 505.02Runco, Susan: 116.05Runyon, Cassandra: 116.07Russell, Chris: 505.01Russell, Christopher T.: 114.01,306.01, 306.04Russell, Michael J.: 202.05DRustamkulov, Zafar: 300.05Ryan, Eileen V.: 204.06Ryan, Erin L.: 110.36, 305.05,414.04Ryan, William: 100.09, 204.06Ryer, Holly: 101.05Rymer, Abigail: 210.06, 219.18Saad Olivera, Ximena BeatrizBeatriz.: 421.04Sagawa, Hideo: 417.08Sahu, Devendra: 420.02Saikia, Sarag J.: 219.21Saki, Mohammad: 414.06Sakon, Itsuki: 414.01Salama, Farid: 304.05Salmon, Julien: 500.04Samarasinha, Nalin H.: 305.05,305.06, 414.04, 414.24, 414.25Samuelson, Robert E.: 304.10Sanchez, Edilberto: 216.15Sanchez, Juan A.: 110.05,204.07, 208.07Sanchez Lana, Diego Paul.:204.11Sanchez-Lavega, A.: 418.10Sanchez-Lavega, Agustin M.:205.02, 205.06, 209.07Sankar, Ramanakumar: 115.06,115.18, 115.19, 421.01Santana-Ros, Toni: 208.04,208.05Santos Sanz, Pablo: 501.01Santos-Sanz, Pablo: 216.07,216.18, 504.08Sarantos, Menelaos: 422.03Sarid, Gal: 111.01Sasaki, Youhei: 115.11Sato, Takao M.: 115.28, 211.02,417.08, 502.01, 502.02

Satoh, Takehiko: 417.08,502.01, 502.02Saur, Joachim: 203.06, 219.18Sava, Paul: 414.27Sayanagi, Kunio M.: 115.27,118.01, 205.11, 219.21, 422.02Schaefer, Christoph: 419.04,508.02Schambeau, Charles A.: 414.08Scheeres, Daniel J.: 100.07,100.08, 117.05, 204.11, 302.04Schelling, Patrick K.: 413.10Schenk, Paul M.: 102.01,102.03, 102.08, 102.09D,214.18, 215.02, 215.06, 221.01,221.02Schindhelm, Eric: 219.24,509.04, 509.06, 509.07,509.08, 509.09Schindler, Karsten: 216.01,216.02Schleicher, David G.: 305.07Schlichting, Hilke: 413.01Schlieder, Joshua E.: 224.06Schloerb, F. Peter.: 415.06Schloerb, Peter: 415.02, 415.03,415.05Schmedemann, Nico: 214.06Schmerr, Nicholas: 219.19,220.05Schmider, Francois-Xavier:500.03Schmidt, Britney E.: 203.04,214.04, 214.09, 224.05Schmidt, Carl: 422.01Schmitt, Bernard: 102.09D,214.20, 215.02, 221.02, 301.03Schmude, Richard W.: 101.06Schneider, Glenn: 200.04Schneider, Nicholas M.: 418.03,418.06, 418.07, 507.06,510.01, 510.03, 510.06, 510.07Schoenfeld, Ashley: 301.03Schotte, Jonathan M.: 417.14Schubert, Gerald: 115.22,303.02Schultz, Cody: 110.21Schwadron, Nathan A.: 406.02Schwamb, Megan E.: 422.05,504.12Schwan, Joseph: 110.16Sciamma-O'Brien, Ella:304.05Scipioni, Francesca: 102.09D,214.18Scotti, James Vernon.: 414.04Scotti, Jim: 112.08Seale, Sandy: 116.09Seaman, Rob: 117.07Seifert, Caleb: 414.26Seiss, Martin: 104.05Senske, David A.: 214.09,220.03Serigano, Joseph: 304.06Ševeček, Pavel: 201.05Sevy, Eric: 219.15Sfair, Rafael: 216.13Shaner, Andrew: 116.11Shankman, Cory: 405.03Sharkey, Benjamin: 110.36Sharrar, Ryan: 510.05Shelly, Frank: 117.07Shemansky, D. E.: 304.08Sheppard, Scott S.: 305.10,405.05, 504.11

Shia, Run-Lie: 202.05DShinnaka, Yoshiharu: 305.01,305.04, 414.01Shkuratov, Yuriy: 203.09SHKURATOV, YURIY G.:417.19Shou, Yinsi: 415.01, 509.05Showalter, Mark: 104.01Showalter, Mark R.: 214.19,215.04Showman, Adam P.: 402.02D,402.03, 408.05, 408.09DShupla, Christine: 116.11Sicardy, Bruno: 216.03, 216.07,501.01, 501.02, 504.08,504.09Sickafoose, Amanda A.: 204.05,216.01, 216.02, 220.01Siegler, Matthew: 404.04DSierks, Holger: 415.02Siltala, Lauri: 201.06Silva, J.S.: 216.15Silva, José: 110.38Silva, Marc: 204.01Sim, Chaekyung: 417.19Simon, Amy A.: 110.01, 115.05,118.04, 205.01, 205.02, 219.21Sinclair, James Andrew.:115.28, 205.02, 205.04, 211.02Sing, David K.: 408.07Singer, Kelsi N.: 102.03,102.08, 221.01, 221.02Siskind, David E.: 418.06Sitko, Michael L.: 500.01Skemer, Andrew: 407.02Skiff, Brian: 204.04Skinner, Ron: 116.09Skrutskie, Michael F.: 407.02,504.01, 504.03Slade, Martin A.: 204.01Slater, Colin: 103.05, 117.09Slavin, James A.: 219.18Slezak, Thomas Joseph.:218.06Slipski, Marek: 510.08, 510.09Slivinski, Carolyn: 101.05Smith, Christina L.: 101.08Smith, Denise A.: 101.04,101.05Smith, Douglas: 117.01Smith, Heather D.: 219.23Smith, Howard Alan.: 110.06Smith, Howard T.: 214.13,219.18Smith, Jeffrey C.: 416.14Smith, Louis Chad.: 101.04Smith, Mary-Ann H.: 416.26Smith, Michael D.: 507.01,507.02Smith, William: 309.01Smith Hackler, Amanda: 116.11Smrekar, Suzanne: 219.06,417.01, 417.02Snedeker, Lawrence: 204.01Snodgrass, Colin: 403.03D,414.15Soderblom, Jason M.: 213.08,213.09, 214.09, 301.05Soderlund, Krista M.: 214.04Solomonidou, Anezina: 214.02,301.03Sonnabend, Guido: 507.03Sonnett, Sarah M.: 117.10,302.03, 414.16, 420.03Soobiah, Yasir: 505.02

Sornig, Manuela: 507.03Sotin, Christophe: 115.16,205.07, 213.09Soto, Alejandro: 224.02,224.05, 504.01, 504.02,504.03, 504.05Spahn, Frank: 104.05Spalding, Christopher:506.09DSpalding, Eckhart: 407.02Sparks, William B.: 203.04Spence, Harlan E.: 406.02Spencer, Alex: 416.11Spencer, John R.: 102.01,203.03, 203.04, 207.01,210.03, 210.04, 215.04, 221.01,221.02, 221.03, 407.01, 504.02,504.04, 504.07Spilker, Linda: 104.08, 108.01,212.04, 212.05, 220.02Spilker, Thomas R.: 219.21,415.03, 415.05, 415.06Spitale, Joseph N.: 207.02,207.03, 214.22Spohrer, Steven: 102.06Spoto, Federica: 103.06, 117.11Springmann, Alessondra:110.12, 305.05, 305.06, 414.04Srama, Ralf: 104.05Sremcevic, Miodrag: 212.06Sromovsky, Lawrence A.:115.17, 205.07, 205.08Stähler, Simon: 220.05Stalder, Brian: 103.04Stanley, Geoff: 217.02Stanley, Sabine: 303.08Stansberry, John: 102.02,215.02, 216.07, 219.10, 219.11Starikova, Evgeniya: 416.26Stassun, Keivan G.: 402.01Steakley, Kathryn: 418.16Steckloff, Jordan: 301.05Steffen, Jason H.: 506.02Steffes, Paul G.: 118.03, 417.04Steffl, Andrew J.: 105.04,509.04, 509.06, 509.07,509.08, 509.09Stein, Thomas: 218.01Steinberg, Elad: 413.01Steinrueck, Maria Elisabeth.:402.03Stephan, Katrin: 214.06,214.07, 301.03Stephens, Andrew W.: 118.04,205.02Stephens, Denise C.: 113.01,416.11Stephens, Haynes: 420.02Stephens, Robert: 110.33Stern, Eric: 106.01Stern, S. Alan.: 102.01, 102.02,102.05, 102.06, 102.07,102.09D, 202.03, 215.04,221.01, 221.03, 504.03, 509.06,509.07Stern, S. Alan: 102.03, 102.08,105.04, 105.05, 215.02, 215.06,221.02, 504.01, 504.02, 504.04,504.06, 504.07, 509.04,509.08, 509.09Stevens, Michael: 219.18Stevens, Michael H.: 418.06,418.07, 507.06, 510.06, 510.07Stevenson, David J.: 109.01,303.03, 303.04, 303.05

Stevenson, Kevin B.: 408.05Stevenson, Zena: 218.03,218.04Stewart, A. Ian.: 418.07, 510.06,510.07Stewart, A. Ian F.: 418.06,507.06Stewart-Mukhopadhyay, SarahT.: 419.01Stickle, Angela: 404.07, 404.08Stiepen, Arnaud: 418.06,507.06, 510.06, 510.07Stillman, David: 400.02Stockstill-Cahill, Karen: 417.10Stone, Jordan: 407.02Strobel, Darrell F.: 105.01,105.04, 215.07Strycker, Paul D.: 115.08,417.14Stubbs, Timothy: 406.02Sturner, Steven J.: 406.02Succi, Giacomo: 504.08Sugita, Seiji: , 110.05, 219.07Sugiyama, Ko-ichiro: 418.24Summers, Michael: 105.04Sung, Keeyoon: 304.04,416.26Sunshine, Jessica M.: 208.11D,302.01, 414.10, 414.11Sutter, Brad: 400.06Svedhem, Hakan: 418.01Swain, Mark R.: 300.04Swayze, Gregg A.: 210.01Sweebe, Kathrine: 218.03,218.04Szalay, Jamey: 404.06Szentgyorgyi, Andrew: 216.14,216.15Tabataba-Vakili, Fachreddin:205.02, 205.10, 205.12Taguchi, Makoto: 502.01Tajeddine, Radwan: 212.10Takahashi, Sanemichi Z.:508.08Takahashi, Yoshiyuki O.:418.24Takamura, Mao: 502.01Takehiro, Shin-ichi: 115.11Takigawa, Aki: 417.20Takir, Driss: 110.05, 219.07,417.10Tamayo, Francisco: 110.38Tamblyn, Peter: 504.01,504.02, 504.03, 504.05Tan, Xianyu: 402.02DTang, Adrian: 224.04Tanga, Paolo: 103.06, 117.11Tao, Chihiro: 211.02Tarano, Ana Maria.: 110.17,111.05Tatsumi, Eri: , 110.05Taylor, Patrick A.: 100.06,100.09, 110.12, 112.09, 204.02,305.06, 414.24Teanby, Nicholas: 304.03,304.06, 304.07Tegler, Stephen C.: 301.02,302.02Tejfel, Victor G.: 118.02Telfer, Matthew: 102.05Tellmann, Silvia: 417.07,502.03Tellmann, Silvia Anna.:418.04, 509.01Temme, Ruth L.: 417.14

Tenenbaum, Peter: 416.14Tenishev, Valeriy: 415.01,509.05Tennyson, Jonathan: 402.06DTeolis, Benjamin: 203.06Terrell, Dirk: 504.01, 504.02,504.03, 504.05Thelen, Alexander: 304.06Thiemann, Ed: 418.07, 510.02,510.04, 510.06Thirouin, Audrey: 110.05,204.04, 204.07, 216.06,305.07, 305.10, 504.11Tholen, David J.: 100.09,111.02, 112.06, 112.13, 405.05Thomas, Cristina A.: 110.02,110.13, 110.25, 110.29, 204.04,208.07Thomas, Ian: 507.01, 507.02Thompson, Garrett: 301.02Thorngren, Daniel: 303.01,408.03, 408.04Throop, Henry B.: 215.04Thuillot, William: 103.06Tian, Bob Yunsheng.: 303.08Tigges, Mattie: 214.22Tigrine, Sarah: 213.02Tinetti, Giovanna: 402.06DTiscareno, Matthew S.:108.02, 212.01, 218.01Tolbert, Margaret: 400.05Tollefson, Joshua: 118.04,205.01, 205.03Tommei, Giacomo: 103.06Tonry, John L.: 103.04Tosi, Federico: 214.18, 214.21Toth, Gabor: 415.01, 505.01,509.05Trafton, Laurence M.: 115.23,207.06, 215.02Trainer, Melissa G.: 219.02,400.06Tremaine, Scott D.: 419.03Triaud, Amaury: 412.01Trilling, David E.: 110.06,110.07, 110.25, 110.29, 110.35,117.04, 204.04, 204.05,208.06D, 208.11DTrujillo, Chadwick: 305.10Trujillo, Chadwick A.: 405.05Trumbo, Samantha K.: 203.05Tsai, Victor: 220.05Tsang, Constantine: 219.09,417.01, 417.02, 502.04Tsiaras, Angelos: 402.06DTsuchiyama, Akira: 417.20Tubbiolo, Andrew: 112.08Tucker, Orenthal: 418.05Tucker, William C.: 413.10Turner, Brandon: 219.15Turner, Franklin: 404.07Turner, Neal J.: 104.08Turtelboom, Emma V.: 110.09Turtle, Elizabeth P.: 214.09,219.02, 304.09, 304.12DTyler, G. Leonard.: 418.04Tyler, G. L.: 215.07Tylor, Christopher: 511.03Tyuterev, Vladimir G.: 416.26Tzou, Chia-Yu: 509.05Umurhan, Orkan: 102.08Umurhan, Orkan M.: 102.03,102.06, 202.02Vago, Jorge L.: 418.01

Väisänen, Timo: 110.22, 110.42,208.02Valek, Philip: 109.02Vals, Margaux: 507.06van der Tak, Floris F S.: 111.06van Gend, Carel: 204.05Van Laerhoven, Christa L.:405.12Vance, Steven: 214.05, 220.05Vandaele, Ann Carine.: 507.01,507.02Vandervoort, Kurt: 203.09Vaniman, David T.: 400.06Varghese, Philip: 207.06Veillet, Christian: 204.07,407.02Venditti, Flaviane: 112.09,204.02Verbiscer, Anne: 210.04Verbiscer, Anne J.: 207.01,215.04, 216.06, 504.01, 504.02,504.03, 504.04, 504.05,504.07Veres, Peter: 103.01Verma, Ashok K.: 100.06Verma, Ashok Kumar: 214.10Vernazza, Pierre: 208.04,208.05Versteeg, Maarten H.: 509.04,509.06, 509.08Vervack, Ronald J.: 110.15,204.02, 305.03, 305.04,305.09, 404.01, 414.06,414.12, 414.13, 509.04, 509.06,509.07Vettier, Ludovic: 213.02Vides, Christina: 203.09Vieira-Martins, Roberto:216.03, 501.01, 504.09Viikinkoski, Matti: 208.05Vilas, Faith: , 511.01Villanueva, Edward: 301.03Villanueva, Geronimo Luis.:203.07, 305.02, 414.06, 414.19,418.08, 507.01, 507.02Villard, Eric: 304.11Villarreal, Michaela: 114.01,306.04Vinatier, Sandrine: 213.01,304.03, 304.11Virkki, Anne: 110.12, 112.09,204.02, 204.03, 305.06Vodniza, Alberto: 117.02Voelz, David: 115.08, 224.03Vokrouhlicky, David: 100.02,401.01Volk, Kathryn: 216.12, 405.02,405.11, 405.12, 504.12von Allmen, Paul: 415.02,415.03, 415.05, 415.06, 509.02Vriesema, Jess William.: 115.21Vuitton, Veronique: 300.02,304.07, 416.25Wagner, Roland: 214.07Wagner, Roland Josef.: 214.06Wagstaff, Kiri: 400.02Wahl, Sean: 109.01, 303.01,303.03Wainscoat, Richard J.: 100.04,103.02, 112.10, 405.01, 420.02Waite, J. Hunter.: 211.02,214.09, 301.01Wakeford, Hannah: 408.07Waldmann, Ingo: 402.05,402.06D, 416.06

Walker, Russell G.: 414.16Wall, Stephen D.: 301.03Wallace, Joshua: 419.03Walsh, Kevin J.: 201.02,201.03, 208.12D, 500.04,508.04Wang, Shiang-Yu: 216.14,216.15, 504.12Wang, Xu: 110.16Wang, Yongli: 406.02Warner, Brian: 110.33, 204.02Warren, Ari: 115.28Wasserman, Lawrence H.:221.03, 504.01, 504.02, 504.03,504.05, 504.06Watanabe, Jun-ichi: 414.01Watanabe, Naoki: 417.20Watanabe, Shigeto: 422.02Watkins, Bryn: 214.02Watson, Zachary Tyler.: 305.05,414.04Weaver, Brian: 506.04Weaver, Harold A.: 102.01,102.02, 102.03, 102.06, 102.07,102.08, 102.09D, 105.04,105.05, 208.08, 215.02, 215.04,215.06, 221.01, 221.02, 305.04,414.13, 509.04, 509.06, 509.07,509.08, 509.09Webber, Tristan: 505.03Weber, Renee: 218.01Wedlund, Cyril Simon: 509.09Weigle, Eddie: 221.02Weinberg, Jonathan: 219.24Weirich, John: 204.09Weissman, Paul R.: 200.02Werner, Stephanie: 214.06,413.09Weryk, Robert J.: 100.04,103.02, 112.01, 405.01Werynski, Alyssa: 301.04West, Richard D.: 212.11West, Robert A.: 115.20,408.02Westlake, Joseph H.: 210.06,214.09, 219.18Wheeler, Lorien: 110.17,110.18, 111.05White, Jacob: 503.01DWhite, Oliver L.: 102.03,102.06, 102.08Whizin, Akbar: 117.01Widemann, Thomas: 417.01,417.02Wiedemann, Manuel: 504.06Wierzchos, Kacper: 305.08,420.01Wigton, Nathanael R.: 110.13Wijerathna, Erandi: 115.08Wiktorowicz, Sloane: 110.32Willacy, Karen: 202.05DWilliams, Darren: 416.13Williams, Gareth: 103.01,103.02Williams, Hayley: 413.11Williams, Jean-Pierre: 404.08Williamson, Hayley: 418.05,510.09Willman, Mark: 204.04Wilson, Eric: 115.20Wilson, Robert John.: 418.15Winter, Othon Cabo.: 212.08,216.13Witasse, Olivier: 301.03Withers, Paul: 418.12

Wolff, Michael J.: 418.14,507.06Wolters, Cedric: 416.25Womack, Maria: 305.08,401.02, 414.17, 420.01Wong, Ian: 302.06DWong, Michael H.: 118.04,205.01, 205.02, 205.03,205.05, 219.21Wong, Michael L.: 202.05DWoo, Man Yin: 508.09Wood, Jeremy R.: 221.04Wooden, Diane H.: 117.01,414.15Woodney, Laura: 414.08Woodward, Charles E.: 110.36,407.02, 414.11Worters, Hannah L.: 204.05Wray, James J.: 400.06Wright, Edward L.: 117.10,414.16, 420.03Wright, Ernest: 417.17

Wright, Joe: 116.06Wright, Rita: 116.06Wu, Zhaopeng: 418.23Xu, Shaosui: 505.02, 505.03Yakovlev, Vladislav V.: 224.05Yamada, Michio: 115.12Yamada, Takeru: 502.01Yamaguchi, MItsuru: 414.01Yamamoto, Yukio: 204.10Yamashita, Tatsuya: 418.24Yanamandra-Fisher, Padma A.:101.07, 115.15Yanez, Maya Danielle.: 216.16Yang, Bin: 208.04, 305.01,414.11, 420.02Ye, Shengyi: 104.06Yelle, Roger: 507.06Yelle, Roger V.: 115.21, 408.01,510.01Yen, Albert: 400.06Yen, Wei-Ling: 216.14, 216.15Youdin, Andrew N.: 500.06

Young, Eliot F.: 102.02, 504.01,504.02, 504.03, 504.05,504.06Young, Leslie: 102.01, 102.02,102.03, 102.06, 102.07, 102.08,102.09D, 105.03, 105.04,105.05, 215.02, 215.04, 215.06,216.17, 221.01, 221.02, 504.06Young, Roland M B.: 115.10,205.10Yu, Xinting: 300.01Yung, Yuk: 202.05D, 213.04,304.08, 416.18, 417.06Yurchenko, Sergey: 402.06DZahnle, Kevin: 300.03, 401.02Zambrano-Marin, Luisa F.:305.06Zambrano-Marin, LuisaFernanda.: 112.09, 204.02,414.24Zangari, Amanda Marie.:504.01, 504.02, 504.03,

504.04, 504.05, 504.06, 504.07Zderic, Alexander: 414.23Zellem, Robert: 416.06Zeng, Xingguo: 219.05, 417.15,417.16Zhang, Hongbo: 219.05,417.15, 417.16Zhang, Keke: 115.22, 303.02Zhang, Qicheng: 414.03Zhang, Xi: 105.01, 115.26,115.28, 417.21, 418.23Zhang, Xiaofei: 110.39Zhang, Zhi-Wei: 216.14, 216.15Zhang, Zhimeng: 212.11Zhao, Yuhui: 110.37Zingales, Tiziano: 402.06DZiobron, Elijah: 418.09Zolensky, Michael: 117.01Zou, Xiaoduan: 403.02Zube, Nicholas Gerard.: 115.26Zuluaga, Carlos: 216.01Zuluaga, Carlos A.: 216.02

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49th DPS Session Table of Contents - Microsoft...2017/10/16 · 49th DPS Provo, UT – October, 2017 Meeting Abstracts Session Table of Contents 100 – Dynamics, Origins and Theory: