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Space News Update — October 25, 2016 —

Contents

In the News

Story 1:

Titan Experiences Dramatic Seasonal Changes

Story 2:

Curious Tilt of the Sun Traced to Undiscovered Planet

Story 3:

NASA’s MAVEN Mission Observes Ups and Downs of Water Escape from Mars

Departments

The Night Sky

ISS Sighting Opportunities

NASA-TV Highlights

Space Calendar

Food for Thought

Space Image of the Week

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1. Titan Experiences Dramatic Seasonal Changes

Slipping into shadow, the south polar vortex at Saturn's moon Titan still stands out against the orange and blue haze layers that are characteristic of Titan's atmosphere. Images like this, from NASA's Cassini spacecraft, lead scientists to conclude that the polar vortex clouds form at a much higher altitude -- where sunlight can still reach -- than the lower-

altitude surrounding haze. Credits: NASA/JPL-Caltech/Space Science Institute

As Titan approaches its northern summer solstice, NASA’s Cassini spacecraft has revealed dramatic seasonal

changes in the atmospheric temperature and composition of Saturn’s largest moon. Winter is taking a grip on

the southern hemisphere and a strong vortex, enriched in trace gases, has developed in the upper atmosphere

over the south pole. These observations show a polar reversal in Titan’s atmosphere since Cassini arrived at

Saturn in 2004, when similar features were seen in the northern hemisphere.

“Cassini’s long mission and frequent visits to Titan have allowed us to observe the pattern of seasonal changes

on Titan, in exquisite detail, for the first time,” says Dr. Athena Coustenis of the Observatoire de Paris, who is

presenting results at the joint 48th meeting of the American Astronomical Society’s Division for Planetary

Sciences and 11th European Planetary Science Congress. “We arrived at the northern mid-winter and have

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now had the opportunity to monitor Titan’s atmospheric response through two full seasons. Since the equinox,

where both hemispheres received equal heating from the Sun, we have seen rapid changes.”

Heat is circulated through Titan’s atmosphere via a pole-to-pole cycle of warm gases upwelling at the summer

pole and cold gases subsiding at the winter pole. Cassini’s observations have shown a large-scale reversal of

this system immediately after the equinox in 2009.

Titan’s hemispheres have responded in different ways to these seasonal changes. The wintery effects have led

to a temperature drop of 40 degrees Celsius in the southern polar stratosphere over the last four years. This

contrasts with a much more gradual warming in the northern hemisphere, where temperatures remained

stable during the early spring and have shown a 6-degree increase only since 2014.

Within months following the equinox, the vortex in the stratosphere over the south pole had become

prominent, as had an atmospheric ‘hot spot’ at high altitudes. The corresponding features in the northern

hemisphere had almost disappeared by 2011.

Inside the polar vortex over the increasingly shadowed south pole, there has been a rapid build-up of trace

gases that accumulate in the absence of ultraviolet sunlight. These include complex hydrocarbons and nitriles

such as methylacetylene and benzene, previously seen only at high northern latitudes.

Coustenis says, “We’ve had the chance to witness the onset of winter from the beginning and are approaching

the peak time for these gas-production processes in the southern hemisphere. We are now looking for new

molecules in the atmosphere above Titan’s south polar region that have been predicted by our computer

models. Making these detections will help us understand the photochemistry going on.”

In the northern hemisphere, the trace gases have persisted well into summer. These are predicted to undergo

a slow photochemical destruction, with species disappearing at different rates depending on their chemical

lifetimes. However, since early 2016, a zone of depleted molecular gas and aerosols has developed across the

entire northern hemisphere between an altitude of 400 and 500 kilometers, suggesting a complex dynamical

effect starting at high altitudes in the atmosphere.

“As we count down to the end of the Cassini mission in September 2017, a consistent picture of Titan’s middle

and upper atmospheres is emerging,” says Coustenis. “The 13-year total mission duration will in the end

provide us with coverage of almost half a Titan year and provide an even deeper understanding of Titan’s

seasonal variability.”

Source: NASA and European Planetary Science Congress Return to Contents

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2. Curious Tilt of the Sun Traced to Undiscovered Planet

This artistic rendering shows the distant view from Planet Nine back towards the sun. The planet is thought to be

gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side. Credit: Caltech/R. Hurt (IPAC)

Planet Nine—the undiscovered planet at the edge of the Solar System that was predicted by the work of Caltech's Konstantin Batygin and Mike Brown in January 2016—appears to be responsible for the unusual tilt of the sun, according to a new study. The large and distant planet may be adding a wobble to the solar system, giving the appearance that the sun is tilted slightly. "Because Planet Nine is so massive and has an orbit tilted compared to the other planets, the solar system has no choice but to slowly twist out of alignment," says Elizabeth Bailey, a graduate student at Caltech and lead author of a study announcing the discovery. All of the planets orbit in a flat plane with respect to the sun, roughly within a couple degrees of each other. That plane, however, rotates at a six-degree tilt with respect to the sun—giving the appearance that the sun itself is cocked off at an angle. Until now, no one had found a compelling explanation to produce such an effect. "It's such a deep-rooted mystery and so difficult to explain that people just don't talk about it," says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy. Brown and Batygin's discovery of evidence that the sun is orbited by an as-yet-unseen planet—that is about 10 times the size of Earth with an orbit that is about 20 times farther from the sun on average than Neptune's—changes the physics. Planet Nine, based on their calculations, appears to orbit at about 30 degrees off from

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the other planets' orbital plane—in the process, influencing the orbit of a large population of objects in the Kuiper Belt, which is how Brown and Batygin came to suspect a planet existed there in the first place. "It continues to amaze us; every time we look carefully we continue to find that Planet Nine explains something about the solar system that had long been a mystery," says Batygin, an assistant professor of planetary science. Their findings have been accepted for publication in an upcoming issue of the Astrophysical Journal, and will be presented on October 18 at the American Astronomical Society's Division for Planetary Sciences annual meeting, held in Pasadena. The tilt of the solar system's orbital plane has long befuddled astronomers because of the way the planets formed: as a spinning cloud slowly collapsing first into a disk and then into objects orbiting a central star. Planet Nine's angular momentum is having an outsized impact on the solar system based on its location and size. A planet's angular momentum equals the mass of an object multiplied by its distance from the sun, and corresponds with the force that the planet exerts on the overall system's spin. Because the other planets in the solar system all exist along a flat plane, their angular momentum works to keep the whole disk spinning smoothly. Planet Nine's unusual orbit, however, adds a multi-billion-year wobble to that system. Mathematically, given the hypothesized size and distance of Planet Nine, a six-degree tilt fits perfectly, Brown says. The next question, then, is how did Planet Nine achieve its unusual orbit? Though that remains to be determined, Batygin suggests that the planet may have been ejected from the neighborhood of the gas giants by Jupiter, or perhaps may have been influenced by the gravitational pull of other stellar bodies in the solar system's extreme past. For now, Brown and Batygin continue to work with colleagues throughout the world to search the night sky for signs of Planet Nine along the path they predicted in January. That search, Brown says, may take three years or more.

Source: California Institute of Technology Return to Contents

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3. NASA’s MAVEN Mission Observes Ups and Downs of Water Escape from Mars

This image shows atomic hydrogen scattering sunlight in the upper atmosphere of Mars, as seen by the Imaging

Ultraviolet Spectrograph on NASA’s Mars Atmosphere and Volatile Evolution mission. About 400,000 observations, taken

over the course of four days shortly after the spacecraft entered orbit around Mars, were used to create the image.

Hydrogen is produced by the breakdown of water, which was once abundant on Mars' surface. Because hydrogen has low

atomic mass and is weakly bound by gravity, it extends far from the planet (the darkened circle) and can readily escape.

Credits: NASA/Goddard/University of Colorado

This loss had long been assumed to be more-or-less constant, like a slow leak in a tire. But previous

observations made using NASA’s Hubble Space Telescope and ESA’s Mars Express orbiter found unexpected

fluctuations. Only a handful of these measurements have been made so far, and most were essentially

snapshots, taken months or years apart. MAVEN has been tracking the hydrogen escape without interruption

over the course of a Martian year, which lasts nearly two Earth years.

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“Now that we know such large changes occur, we think of hydrogen escape from Mars less as a slow and

steady leak and more as an episodic flow – rising and falling with season and perhaps punctuated by strong

bursts,” said Michael Chaffin, a scientist at the University of Colorado at Boulder who is on the Imaging

Ultraviolet Spectrograph (IUVS) team. Chaffin is presenting some IUVS results on Oct. 19 at the joint meeting

of the Division for Planetary Sciences and the European Planetary Science Congress in Pasadena, California.

In the most detailed observations of hydrogen loss to date, four of MAVEN’s instruments detected the factor-

of-10 change in the rate of escape. Changes in the density of hydrogen in the upper atmosphere were inferred

from the flux of hydrogen ions – electrically charged hydrogen atoms – measured by the Solar Wind Ion

Analyzer and by the Suprathermal and Thermal Ion Composition instrument. IUVS observed a drop in the

amount of sunlight scattered by hydrogen in the upper atmosphere. MAVEN’s magnetometer found a decrease

in the occurrence of electromagnetic waves excited by hydrogen ions, indicating a decrease in the amount of

hydrogen present.

By investigating hydrogen escape in multiple ways, the MAVEN team will be able to work out which factors

drive the escape. Scientists already know that Mars’ elliptical orbit causes the intensity of the sunlight reaching

Mars to vary by 40 percent during a Martian year. There also is a seasonal effect that controls how much

water vapor is present in the lower atmosphere, as well as variations in how much water makes it into the

upper atmosphere. The 11-year cycle of the sun’s activity is another likely factor.

“In addition, when Mars is closest to the sun, the atmosphere becomes turbulent, resulting in global dust

storms and other activity. This could allow the water in the lower atmosphere to rise to very high altitudes,

providing an intermittent source of hydrogen that can then escape,” said John Clarke, a Boston University

scientist on the IUVS team. Clarke will present IUVS measurements of hydrogen and deuterium – a form of

hydrogen that contains a neutron and is heavier – on Oct. 19 at the planetary conference.

By making observations for a second Mars year and during different parts of the solar cycle, the scientists will

be better able to distinguish among these effects. MAVEN is continuing these observations in its extended

mission, which has been approved until at least September 2018.

“MAVEN’s findings reveal what is happening in Mars’ atmosphere now, but over time this type of loss

contributed to the global change from a wetter environment to the dry planet we see today,” said Rahmati.

MAVEN’s principal investigator is based at the University of Colorado’s Laboratory for

Atmospheric and Space Physics, Boulder. The university provided two science instruments and

leads science operations, as well as education and public outreach, for the mission. NASA’s

Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN project and provided two science

instruments for the mission. Lockheed Martin built the spacecraft and is responsible for mission

operations. The University of California at Berkeley’s Space Sciences Laboratory also provided four science

instruments for the mission. NASA’s Jet Propulsion Laboratory in Pasadena, California, provides navigation and

Deep Space Network support, as well as the Electra telecommunications relay hardware and operations.

Source: NASA Return to Contents

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The Night Sky

Source: Sky and Telescope Return to Contents

Friday, October 28

The low twilight lineup of Saturn, Venus, and Antares in the southwest now begins to bend the other

way, as Venus moves east.

Around the same time, look for Arcturus low in the west-northwest.

Saturday, October 29

The Ghost of Summer Suns: Halloween is approaching, and this means that Arcturus, the star sparkling

low in the west-northwest in twilight, is taking on its role as "the Ghost of Summer Suns." For several

days centered on October 29th every year, Arcturus occupies a special place above your local landscape.

It closely marks the spot where the Sun stood at the same time, by the clock, during hot June and July

— in broad daylight, of course.

So, in the last days of October each year, you can think of Arcturus as the chilly Halloween ghost of the

departed summer Sun.

Venus passes between Saturn and Antares low in twilight on Thursday the 27th. (The visibility of faint stars in bright twilight

is exaggerated here.)

Tuesday, October 25

Draw a line from Altair, the brightest

star high in the southwest after dark,

to Vega, the brightest high in the

west. Continue the line half as far

onward and you hit the Lozenge: the

pointy-nosed head of Draco, the

Dragon.

The Great Square of Pegasus is now

quite high in the east-southeast just

after dark — still, for now, balancing

on one corner (as seen from the

world's mid-northern latitudes).

Wednesday, October 26

Low in the southwest in twilight,

Saturn, bright Venus, and Antares

form a nearly vertical curve, in that

order from top to bottom. It's 7° tall.

Thursday, October 27

Now Saturn, bright Venus, and

Antares straighten out into a nearly

vertical line, as shown at right.

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ISS Sighting Opportunities (from Denver)

No sightings of ISS from Denver until October 30, 2016 Sighting information for other cities can be found at NASA’s Satellite Sighting Information

NASA-TV Highlights (all times Eastern Time Zone)

Tuesday, October 25

12 p.m. - NASA Television Video File News Feed of the ISS Expedition 50-51 Crew Qualification Training at

the Gagarin Cosmonaut Training Center in Star City, Russia (Whitson, Novitskiy, Pesquet; recorded on Oct.

24-25) (all channels)

1 p.m., Tuesday - NASA and the Smithsonian National Air and Space Museum Panel on Solar Hazards in

Exploration (all channels)

3 p.m. 7 p.m. and 11 p.m. - Replay of Space to Ground ISS Weekly Highlights (10/20/16) (all channels)

4 p.m. 8 p.m. and 10 p.m. - Replay of the NASA Television Video File News Feed of the ISS Expedition 50-

51 Crew Qualification Training at the Gagarin Cosmonaut Training Center in Star City, Russia (Whitson,

Novitskiy, Pesquet; recorded on Oct. 24-25) (all channels)

6 p.m. and 9 p.m. - Replay of the NASA and the Smithsonian National Air and Space Museum Panel on Solar

Hazards in Exploration (all channels)

Wednesday, October 26

8:30 a.m. - ISS Expedition 49 In-Flight Event for JAXA with Flight Engineer Takuya Onishi of the Japan

Aerospace Exploration Agency (NTV-1 with English interpretation; NTV-3 in native language) (starts at 8:40

a.m.) (all channels)

4 p.m. - Replay of the ISS Expedition 50-51 Crew News Conference at the Gagarin Cosmonaut Training

Center in Star City, Russia (Whitson, Novitskiy, Pesquet) (all channels)

4:30 p.m. - NASA Television Video File News Feed of the ISS Expedition 50-51 Crew’s Ceremonial Visit to

the Gagarin Museum at the Gagarin Cosmonaut Training Center and their Visit to Red Square and the

Kremlin in Moscow (starts at 4:45 p.m.) (all channels)

Thursday, October 27

6:30 a.m. - Video B-Roll Feed of Training and Previous Missions of ISS Expedition 50-51 Astronaut Peggy

Whitson of NASA (all channels)

7 a.m., - Live Shot Interviews with ISS Expedition 50-51 Astronaut Peggy Whitson of NASA from the Gagarin

Cosmonaut Training Center in Star City, Russia (all channels)

5 p.m. - Space to Ground ISS Weekly Highlights (all channels)

Friday, October 28

3:30 p.m. - ISS Expedition 49-50 Change of Command Ceremony (Ivanishin hands over ISS command to

Kimbrough) (all channels)

Watch NASA TV online by going to the NASA website. Return to Contents

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Space Calendar

Oct 25 - Comet 73P-BB/Schwassmann-Wachmann Closest Approach To Earth (1.572 AU)

Oct 25 - Comet P/2002 EJ57 (LINEAR) At Opposition (4.008 AU)

Oct 25 - Amor Asteroid 2016 PY78 Near-Earth Flyby (0.083 AU)

Oct 25 - Aten Asteroid 2015 KA Near-Earth Flyby (0.097 AU)

Oct 25 - Asteroid 2712 Keaton Closest Approach To Earth (1.196 AU)

Oct 25 - Asteroid 10221 Kubrick Closest Approach To Earth (1.452 AU)

Oct 25 - Centaur Object 49036 Pelion At Opposition (19.668 AU)

Oct 25-28 - Geological Society of America (GSA) Annual Meeting, Denver, Colorado

Oct 26 - Aten Asteroid 2016 UY5 Near-Earth Flyby (0.042 AU)

Oct 26 - Amor Asteroid 2016 UH Near-Earth Flyby (0.051 AU)

Oct 26 - Aten Asteroid 2016 TA57 Near-Earth Flyby (0.061 AU)

Oct 26 - Apollo Asteroid 2016 TV10 Near-Earth Flyby (0.070 AU)

Oct 26 - Amor Asteroid 2016 TJ56 Near-Earth Flyby (0.093 AU)

Oct 26 - Amor Asteroid 7088 Ishtar Closest Approach To Earth (0.658 AU)

Oct 26 - Asteroid 6312 Robheinlein Closest Approach To Earth (1.085 AU)

Oct 26 - Aten Asteroid 3362 Khufu Closest Approach To Earth (1.221 AU)

Oct 26 - Apollo Asteroid 29075 (1950 DA) Closest Approach To Earth (1.785 AU)

Oct 26 - Asteroid 7755 Haute-Provence Closest Approach To Earth (2.519 AU)

Oct 26-29 - Enchanted Skies Star Party, Magdalena, New Mexico

Oct 27 - Comet 136P/Mueller At Opposition (2.108 AU)

Oct 27 - Comet 94P/Russell Perihelion (2.230 AU)

Oct 27 - Comet 317P/WISE At Opposition (2.687 AU)

Oct 27 - Aten Asteroid 413260 (2003 TL4) Near-Earth Flyby (0.026 AU)

Oct 27 - Aten Asteroid 2012 UA34 Near-Earth Flyby (0.095 AU)

Oct 27 - Asteroid 3487 Edgeworth Closest Approach To Earth (1.559 AU)

Oct 27 - Asteroid 6984 Lewiscarroll Closest Approach To Earth (2.546 AU)

Oct 27 - Kuiper Belt Object 15760 (1992 QB1) At Opposition (40.285 AU)

Oct 28 - Comet 73P-BG/Schwassmann-Wachmann Perihelion (0.996 AU)

Oct 28 - Comet C/2016 T3 (PANSTARRS) At Opposition (3.194 AU)

Oct 28 - Comet P/2015 TP200 (LINEAR) Perihelion (3.385 AU)

Oct 28 - Asteroid 1419 Danzig Occults HIP 13327 (5.5 Magnitude Star)

Oct 28 - Asteroid 4871 Riverside Closest Approach To Earth (1.026 AU)

Oct 28 - Apollo Asteroid 1620 Geographos Closest Approach To Earth (1.339 AU)

Oct 28 - Asteroid 274300 UNESCO Closest Approach To Earth (1.478 AU)

Oct 28 - Asteroid 184784 Bettiepage Closest Approach To Earth (1.860 AU)

Oct 29 - Soyuz MS-1 Return to Earth (International Space Station)

Oct 29 - Cassini, Distant Flyby of Titan

Source: JPL Space Calendar Return to Contents

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Food for Thought

The Universe Is Expanding At An Accelerating Rate – Or Is It?

Researchers analyzed a database of supernovae — the spectacular thermonuclear explosions of dying stars. Image credit:

University of Oxford; Shutterstock.

Five years ago, the Nobel Prize in Physics was awarded to three astronomers for their discovery, in the late

1990s, that the universe is expanding at an accelerating pace.

Their conclusions were based on analysis of Type Ia supernovae – the spectacular thermonuclear explosions of

dying stars – picked up by the Hubble space telescope and large ground-based telescopes. It led to the

widespread acceptance of the idea that the universe is dominated by a mysterious substance named 'dark

energy' that drives this accelerating expansion.

Now, a team of scientists led by Professor Subir Sarkar of Oxford University's Department of Physics has cast

doubt on this standard cosmological concept. Making use of a vastly increased data set – a catalogue of 740

Type Ia supernovae, more than ten times the original sample size – the researchers have found that the

evidence for acceleration may be flimsier than previously thought, with the data being consistent with a

constant rate of expansion.

The study is published in the Nature journal Scientific Reports.

Professor Sarkar, who also holds a position at the Niels Bohr Institute in Copenhagen, said: 'The discovery of

the accelerating expansion of the universe won the Nobel Prize, the Gruber Cosmology Prize, and the

Breakthrough Prize in Fundamental Physics. It led to the widespread acceptance of the idea that the universe

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is dominated by "dark energy" that behaves like a cosmological constant – this is now the "standard model" of

cosmology.

'However, there now exists a much bigger database of supernovae on which to perform rigorous and detailed

statistical analyses. We analyzed the latest catalogue of 740 Type Ia supernovae – over ten times bigger than

the original samples on which the discovery claim was based – and found that the evidence for accelerated

expansion is, at most, what physicists call "3 sigma". This is far short of the 5 sigma standard required to claim

a discovery of fundamental significance.

'An analogous example in this context would be the recent suggestion for a new particle weighing 750 GeV

based on data from the Large Hadron Collider at CERN. It initially had even higher significance – 3.9 and 3.4

sigma in December last year – and stimulated over 500 theoretical papers. However, it was announced in

August that new data shows that the significance has dropped to less than 1 sigma. It was just a statistical

fluctuation, and there is no such particle.'

There is other data available that appears to support the idea of an accelerating universe, such as information

on the cosmic microwave background – the faint afterglow of the Big Bang – from the Planck satellite.

However, Professor Sarkar said: 'All of these tests are indirect, carried out in the framework of an assumed

model, and the cosmic microwave background is not directly affected by dark energy. Actually, there is indeed

a subtle effect, the late-integrated Sachs-Wolfe effect, but this has not been convincingly detected.

'So it is quite possible that we are being misled and that the apparent manifestation of dark energy is a

consequence of analyzing the data in an oversimplified theoretical model – one that was in fact constructed in

the 1930s, long before there was any real data. A more sophisticated theoretical framework accounting for the

observation that the universe is not exactly homogeneous and that its matter content may not behave as an

ideal gas – two key assumptions of standard cosmology – may well be able to account for all observations

without requiring dark energy. Indeed, vacuum energy is something of which we have absolutely no

understanding in fundamental theory.'

Professor Sarkar added: 'Naturally, a lot of work will be necessary to convince the physics community of this,

but our work serves to demonstrate that a key pillar of the standard cosmological model is rather shaky.

Hopefully this will motivate better analyses of cosmological data, as well as inspiring theorists to investigate

more nuanced cosmological models. Significant progress will be made when the European Extremely Large

Telescope makes observations with an ultrasensitive "laser comb" to directly measure over a ten to 15-year

period whether the expansion rate is indeed accelerating.'

Source: Oxford University Return to Contents

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Space Image of the Week

Explanation: As noted in Walter Weinig’s SNU Addendum e-mail last Friday evening, NASA’s Mars

Reconnaissance Orbiter has identified new markings on the surface of the Red Planet that are believed to be

related to ESA’s ExoMars Schiaparelli entry, descent and landing technology demonstrator module. The image

released on Friday has a resolution of 6 metres per pixel and shows two new features on the surface when

compared to an image from the same camera taken in May this year.

One of the features is bright and can be associated with the 12-m diameter parachute used in the second

stage of Schiaparelli’s descent, after the initial heat shield entry.

The other new feature is a fuzzy dark patch roughly 15 x 40 metres in size and about 1 km north of the

parachute. This is interpreted as arising from the impact of the Schiaparelli module itself following a much

longer free fall than planned, after the thrusters were switched off prematurely.

Estimates are that Schiaparelli dropped from a height of between 2 and 4 kilometres, therefore impacting at a

considerable speed, greater than 300 km/h. The relatively large size of the feature would then arise from

disturbed surface material. It is also possible that the lander exploded on impact, as its thruster propellant

tanks were likely still full. These preliminary interpretations will be refined following further analysis.

Source: NASA and ESA Return to Contents

Schiaparelli Landing Site? Image Credit: ESA and NASA