Immersive Scientific Visualization Applied to Mars Research and Exploration

PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING 1

ADVISER: Immersive Scientific Visualization Appliedto Mars Research and Exploration

James W. Head, III1, Andries van Dam2, Samuel G. Fulcomer3, Andrew Forsberg2,Prabhat3, Graham Rosser2, and Sarah Milkovich1

Submitted to Photogrammetric Engineering and Remote Sensing,October 7, 2004; reviews received, April 6, 2005. revised manuscriptaccepted June 15, 2005. (In press).

AbstractGeologists explore Earth at specific surface locations and thenintegrate these data using more synoptic approaches. Planetarygeoscientists, however, are forced by the nature of the availabledata to start from synoptic and orbital data and work downtoward the surface. We describe ADVISER (AdvancedVisualization in Solar System Exploration and Research), aproblem-solving environment that uses advanced visualizationtechniques to bridge an important gap between the cartographicdata sets derived by remote sensing and their application ingeoscientific research. ADVISER integrates and extends state-of-the-art hardware and software technologies into a set of toolsthat provide the planetary geoscientist with the capability tooperate and analyze data and to undertake mapping as if theywere on or near the surface of a planet. Application of thesetools (e.g., virtual field tools and notebook) to analysis of thenorth polar layered terrain on Mars provides insight into polarcap formation and evolution and mission planning activities.

Introduction and BackgroundGeologists explore the Earth primarily through field work andanalysis of the geological record at various points on the surface.They then integrate these individual points of understandingthrough more synoptic analyses, often aided by the integratingperspectives seen from image and topographic data acquiredfrom aircraft and Earth orbit.

Planetary geoscientists commonly work toward anunderstanding in the reverse order. The distances and timesinvolved dictate that the first data from individual moons andplanets comes from flybys and orbital spacecraft, perhaps insome cases evolving toward the deployment of a few landers androvers, and for the Moon, human explorers. Now that global datasets are available for the Moon, Mars and Venus, we can beginto undertake the detailed exploration of planetary surfaces that isrequired for the full understanding of the evolution of planets(e.g., Head, 2001).

How do we accomplish this? In only a very few cases canwe expend the resources to put a lander and rover, and thus oureyes and ears, down onto the surfaces of the planets. The

successful Pathfinder rover (e.g., Golombek et al., 1999) and thecurrently operating Mars Exploration Rovers (e.g., Squyres etal., 2004a, b) are testimony to the exciting results that can beobtained by such surface exploration. Fortunately, developmentsin advanced visualization and immersive virtual realityenvironments have created the ability to place the geoscientistback down on and near the surface, to visit virtually any part ofthe planet they wish to see, and to regain the perspective that isthe foundation for the understanding of the geologicalrelationships necessary to unlock the record of the history of theplanets. Specifically, we are using a Cave fully immersivevirtual reality system (Cruz et al., 1993) to put geoscientists inremote places such as Mars. Our Cave’s construction physicallyconsists of four 8-foot square display surfaces that have edgesseamlessly joined to form a cube-like volume. We have a frontwall, a left wall, a right wall, and a floor surface (Figure 1).Computer-generated stereo images are projected by onecomputer per wall using an Electrohome 9500 projector. Our 4-node cluster has one nVidia Quadro FX 3000G graphics cardsper machine. All of these components are synchronized topresent to one or more viewers a virtual environment of Marsthat is generated from various data sources (e.g., topography,remote sensing data, etc.).

Image and altimetry data, as well as associated data setsdescribing the physical and mineralogical properties of thesurface materials, are now available for Mars (and, to a lesserextent, for other planetary bodies), and a substantial amount ofeffort has been invested in putting these data sets in map formand placing them in a common cartographic coordinate system,an essential step before they can be used comparatively. Aspectsof this process of photogrammetric/cartographic analysis ofMars remote sensing data are described in several other papersin this special issue. Even with the key data sets available incommon cartographic coordinates, however, extracting themaximum geoscientific insight from them is a challenging taskthat depends critically on having the right software tools.What is required to overcome this major barrier to theexploitation of planetary photogrammetry and remote sensingdata? Clearly, a set of tools that can both ingest data sets frommultiple missions and present them to the user in the mosteffective way are required. Unfortunately, much of the planetaryscience community is not aware of the computer science andtechnology developments that can enable interactive virtualexploration and thus do not seek to use them in their researchand teaching. For the past several years, scientists in thePlanetary Geosciences Group have been working with personnelin the Center for Computation and Visualization (CCV) andDepartment of Computer Science at Brown University toexplore, develop, and publicize capabilities in the planetarygeosciences. These capabilities have come in two areas: 1)Advanced visualization techniques, and 2) Immersive virtualreality. In the past, high resolution terrain visualization and otherforms of planetary data visualization have taken separate paths.

1Department of Geological Sciences, Brown University,Providence, RI 02912 USA2Department of Computer Science, Brown University,Providence, RI 02912 USA3Center for Computing and Visualization, Brown University,Providence, RI 02912 USA


High resolution 3D representations of terrain data have typicallybeen computed off-line as fixed sequence movies, while at thesame time planetary data sets are commonly presented for queryin mapping format (the Planetary Data System Map-A-Planet,and the USGS Astrogeology Branch PIGWAD site). Less efforthas gone into integration of planetary data sets and recentdevelopments in visualization that can provide realtimeinteractive visualization of high-resolution data, and analysistechniques that facilitate the exploration and exploitation of thedata.

Therefore, we see the demonstration of this synergism as afundamental first step in establishing the importance of thesetechniques so that they can be developed further and be routinelyapplied to scientific problems in research throughout thecommunity. Here we describe these techniques and tools forphotogrammetry applied to address several remote sensing datasets to important scientific problems in geologic mapping andanalysis on Mars.

Approaches and Related WorkOur contribution is in the development of an immersive tool forplanetary geoscientists. In particular, we are advancing the stateof the art in user interfaces and rendering techniques as drivenby the specific science problems described later, and as much aspossible leveraging the other necessary components includingdata formats, data repositories, and data management.

Approaches that employ off-line rendering are not applicable toour current work because interactivity (i.e., rendering 30+frames per second) is a requirement for ADVISER, though pastwork of this type does illustrate some of the benefits of terrainvisualization for planetary geology (e.g., Kirk et al. 1992;Chapman et al. 1994). An existing resource whose objectivesresemble those of ADVISER is the NASA Ames Marsoweb(Deardorff et al., 2002), which offers interactive map displayand 3D visualization of Mars data sets from multiple missionsand instruments. The VRML (Virtual Reality MarkupLanguage) visualizations that this site provides over the Internetare non-immersive, however, and fall short of the performanceneeded for virtual field geology.

Data Sources.There are several technologies for managing and analyzingplanetary geosciences data. MEGIS, the Mars ExpressGeosciences Information System (Ori, 2004), focuses onproviding data management and analysis tools for the ESA MarsExpress mission; however, it was developed using the availabledata from the NASA Viking, Mars Global Surveyor (MGS) andOdyssey missions. The NASA Planetary Data System is adistributed data archive; it provides a simple web front-end(Garcia, 2005) to select, customize and download maps for avariety of planetary bodies, including Mars. There are also datamanipulation tools for specific mission instruments; forexample, Arizona State University provides tools and aclearinghouse for MGS data (Planetary Image ResearchLaboratory, 2005); USGS provides the excellent imageprocessing toolkit ISIS (ISIS Development Team, 2005). Thereare additional efforts that focus on public outreach andeducation. We are also using ArcGIS for compiling data fromthe above mentioned sources.

3D Visualization Tools.1) Immersive Planetary Exploration: There are prior examplesof the use of Immersive Virtual Reality (IVR) and semi-immersive VR visualization in planetary exploration. In earlywork at NASA Ames, McGreevy (1993) combined geometricrendering of terrains with image-based rendering (IBR)techniques to provide interactive performance with the limitedrendering capabilities of the day. McGreevy (1993) presents areview of VR techniques and applications to several NASAmissions. Recognizing the limitations of studying spatial datawith a "desktop metaphor" he encourages the use of an"exploration metaphor" for improving the operationaleffectiveness of terrain exploration. The Virtual PlanetaryExploration (VPE) system featured a Head Mounted Display andused relatively modest graphics hardware to present stereoimages to the user. Graphics hardware has improved by orders ofmagnitude since then, and coupled with better algorithms we arein a position to present topographic details to the user at muchhigher resolutions. A more recent project, the “GeoWall” (Morinet al., 2001) is a successful example of the application of low-cost virtual reality technology to geosciences research andeducation. The hardware setup typically consists of a single walldisplay and a couple of projectors in a passive stereoconfiguration. A single machine is used to drive the projectors.A variety of free 2D (standard image viewers and video players)and 3D software such as Immersaview (Spale, 2004), Vis5D(Hibbard and Santek, 1990), Walkabout (Johnson, 2004), andWiggleview (Nayak et al., 2005) are used for scientificvisualization. The hardware components of GeoWall could beuseful for our outreach and education needs, but the softwaredoes not provide the high performance our research needs.

2) Interactive Terrain Visualization: A variety of terrain

Figure 1. ADVISER system components and the Caveimmersive virtual reality system. See text for detailedexplanation.


visualization software (both commercial and research) iscurrently available (Discoe, 2002) but no single package couldmeet all of ADVISER’s requirements. For example, MOLA datafor the entire planet is available at a resolution of 46k x 22k,which produces approximately 2 billion triangles. Among thefew candidates that satisfy our performance criteria, we havefound that ROAM is the most promising (Duchaineau et al.,1997). This system supports out-of-core paging of data and aview-dependent simplification algorithm to render the visibleterrain at full resolution. Recent improvements to the algorithm(Duchaineau, 2003) use programmable features of commoditygraphics hardware and texture paging. Additionally, ROAM canalso support high resolution insets of both altimetry and texture.

Among other candidates, the SOAR algorithm (Lindstromand Pascucci, 2001) is also promising with demonstratedinteractive performance for 16k x 16k terrains. VTP software(Discoe, 2002) presents a range of features and visualizationalgorithms; unfortunately, its performance does not scale toterrains larger than 8k x 8k.

3) Immersive Multi-variable Visualization: Vis5D (Hibbard andSantek, 1990) is designed for interactive visualization of largegridded data (e.g., numerical weather models). The user cancreate isosurfaces, contour line slices, colored slices, volumerenderings, and other visual structures and interactively viewthem in real time. One can trace wind trajectories, make textannotations, and do interactive data analysis. The VisualizationToolKit (Schroeder et al., 2004) is a library of visualization toolsthat can be applied to ADVISER for vector field visualization.Neither toolkit supports high performance terrain and texturerendering of very large data sets. However, we do plan on usingcomponents of them for some scientific visualizationrequirements of ADVISER.

The ADVISER Problem Solving EnvironmentWe are working to accomplish our geologic analysis goalsthrough ADVISER, a problem-solving environment (PSE) forplanetary geosciences. We define the PSE as a toolkit, a set of

Figure 2. Views inside the Cave showing IVR portrayals of the Mars North polar cap and various tools associated with ADVISERimplementation. A) Topography and altimetry profiles. B) Topographic contours and tracing of layers in the polar layered terrain. C)Data displayed from the NASA Ames atmospheric general circulation model (GCM) (e.g., temperature, pressure, etc.). D) A wirelessPDA for use in instant navigation, data display and recording.


tools that provides the planetary geoscientist with the capabilityto explore and analyze data as if they were on or near the surfaceof a planet. Below we describe ADVISER’s components, thetechnical challenges in building the system, and our currentimplementation.

ADVISER ScopeThe ADVISER PSE has five basic parts:

1) Geoscientist on the surface. This enables planetarygeoscientists to be on or near the surface by means of immersivevirtual reality, such as the Cave (Figures 1, 2). The large volumeof high-resolution data required also places severe requirementson system performance.

2) Importation and visualization of multiple data sets. Oneof the basic components is on-demand importation, co-registration and overlay of relevant image format data sets toenhance the eyes of the geoscientists and their ability to correlateand interpret data for scientific analysis. For example, in Figure2 geoscientists are exploring the north polar cap of Mars (seen inthe background of Figure 2a-d), using topography from the MarsOrbiter Laser Altimeter, with Viking Orbiter images overlain(Figure 3a, b) and Mars Orbiter Camera (MOC) very high-resolution images (Figure 3c) inserted into the scene. Otherhigh-resolution data sets that we utilize include THEMIS(THermal EMission Imaging System), HRSC (High ResolutionStereo Camera), OMEGA Imaging Spectrometer, synoptic GRS(Gamma Ray Spectrometer), TES (Thermal EmissionSpectrometer), and other types of derived regional data sets(slope, mineralogy, temperature, etc.).

3) Field kit. This is analogous to the geologist's field kit andconsists of a set of software functions that have the capabilitiescommonly carried out by the geologist in the field using toolslike the Brunton compass (orientation, direction, slopes, strikeand dip of strata, etc.), altimeter, etc. It consists of selectableitems including such things as elevation of any point chosen,relative elevations, slope determinations, topographic and slopeprofiles, strike and dip of planes defined by several points on thesurface (e.g., a continuous layer in the polar layered terrain or anoutcrop in Valles Marineris), and the ability to determine winddirections and velocities. For example, in Figure 2a, two markers(downpointing cones) have been placed on the surface todetermine the exact elevation of each point, and to assess thenature of the topography between the points. On the left wall,the elevation of the two end points and an altimetry profilebetween the two points are displayed. In Figure 2b, contourlines (lines of equal elevation) can be displayed at specifiedintervals (e.g., every hundred meters) or special contours can behighlighted and color-coded to trace the relationships of plane-like beds in the polar terrain to topography, and to determinetheir angular orientation (strike and dip). Atmospheric data canalso be called up from the NASA Ames General CirculationModel (GCM). For example, in Figure 2c, data on localtemperature and pressure are displayed as the scientist navigatesacross the polar cap. Also displayed on the right wall aretimelines that span a full Mars year for these values. In the lowerright of Figure 2c is a menu from which many of these tools canbe selected.

4) Ancillary virtual field instruments. These are analogousto the additional tools that the geoscientist carries in the field,such as cameras, Global Positioning System (GPS), and fieldnotebooks. Specifically, we are developing the capability forvirtual photography, virtual GPS, and an electronic field

notebook that will record all relevant observations and images ina downloadable integrated data set. For example, in the upperleft of Figure 2b is seen the overview and location map thatdisplays not only the current location of the geoscientist, butalso the previous locations and stations, and a traverse mapindicating the terrain that has been navigated and investigated upto this point in the session. Preplanned traverses can also beinserted and followed using this tool. This active traverse mapforms the basis for the field notebook and its data entries. We arealso investigating the use of a wireless Personal Data Assistant(PDA) (Figure 2d) for automated click-and-go navigation and avariety of other user interface elements.

5) Geologic mapping. Culminating the use of all of thesetools is the compilation of a geologic map. Here we importgeologic map data in common vector format(s) and display themalong with other remote sensing data sets. We can create andedit geologic map information directly on the visualization andexport the results to a digital geologic mapping environment.

System DescriptionThe data, rendering, and user interface components ofADVISER are shown in Figure 1. While ADVISER willultimately be able to run in multiple display environments, weshow it driving a 4-wall Cave in this scenario. The fourinstances of the application (labeled “RENDER” in Figure 1) runin synchronized execution mode and together present the viewerwith a seamless rendering of the 3D data across the display’swalls. Each application instance generates the display for asingle wall of the 4-wall Cave. Data can be imported from localdisk or downloaded from the internet (e.g., via the Web MapServer standard). The user interface component supports basicnavigation as well as the geologist’s tools. Our implementationis written in C++ and OpenGL. Our approach to synchronizingmultiple rendering nodes is described in Lemmerman andForsberg (2004).

Current implementationWe have built a prototype system that currently implements amajor subset of the ADVISER capability. It renders stereoframes of detailed topography at 30+ frames-per-second (fps) inour Cave, supports high-resolution camera image overlays ontopography, and a subset of the geologist’s tools describedabove. A geoscientist can be immersed in a terrain that is about8192 samples square and interactively navigate through it(Figure 2). Our implementation uses an extended version of theROAM system implemented at the Department of EnergyLawrence Livermore National Laboratory (Duchaineau et al.,1997). ROAM efficiently implements the simple idea ofrendering terrain near the viewer at highest detail andsimplifying more distant terrain. ROAM's execution time isproportional to the number of underlying triangle changes perframe, which is typically a few percent of the rendered meshsize, hence ROAM performance is insensitive to the resolutionand extent of the input terrain. Twenty sub-regions of MOLAdata that collectively cover all of Mars as well as a region ofAntarctica can be viewed. We have embedded MOC (Figure 3c),Viking, and HRSC images over the MOLA data (Figure 3a,b)enabling the scientist to study multiple images in their properterrain context. Currently we use standard OpenGL texturemapping to overlay images; this limits their resolution to 4096 x4096 pixels.


The field kit currently supports a compass, an altimeter, atool for producing a terrain profile between any two points, andstrike and dip measurement capability (Figure 2a-c) . Foroperations requiring elevation data we index into a 2D heightfield grid. For strike and dip plane calculations from three or

more user-specified sample points we use the NAG singularvalue decomposition routine. Our implementation also has abasic mechanism for indexing into the Mars GCM data based ona time variable and user position. Using this we display GCMdata such as atmospheric pressure and temperature at the

Figure 3. Data types for the exploration of the North polar cap. A) Viking image data superposed on MOLA altimetry andviewed perspectively. B) Viking image data showing troughs in which the polar layered terrain is exposed. C) MOC veryhigh resolution data of the polar layered terrain. D) Landing sites and traverses investigated in the Palmer Quest missiondesign study.


viewer’s location (Figure 2c).Ancillary virtual field instruments include a heads-up-

display map that provides overviews of the current location ofthe scientist (Figure 2a,b). Multiple contour lines derived fromdynamic user-specified elevation values can also be applied tothe terrain (Figure 2b). A custom pixel shader was integratedwith ROAM to render the dynamic contour lines in real time.

Application to Current Problems in Planetary GeoscienceWe are undertaking a three-pronged geosciences investigation toassess the history of atmospheric and subsurface volatiles onMars and to demonstrate the scientific usefulness ofvisualization and IVR in planetary geosciences with theADVISER system. ADVISER was used for all of theseinvestigations thus far, but some results were made possible withconventional desktop and lab tools that in the future will beintegrated with ADVISER. The three-part science approachbuilds on central research themes in planetary geoscience, aswell as the basic NASA research and exploration theme "Followthe Water" for Mars. The basic themes are 1) Formation andevolution of the north polar cap, 2) Formation and evolution oftropical mountain glaciers, and 3) Automated and humanexploration of Mars.

The North Polar CapAmong the major questions associated with formation andevolution of the North polar cap are: 1) the age of the cap(Figure 3a), 2) the origin of the swirl-like troughs in the cap(Figure 3b), 3) the nature and origin of the layers exposed in thetroughs (Figure 3c), and 4) the lateral extent of the cap. Inrelated research, we have interpreted a range of geologicalobservations to mean that the presently 'static' Mars polar icecaps (Figure 3) underwent change in the recent geological pastdue to increased obliquity, producing a Mars 'ice age' (Head etal., 2003), during which portions of the water ice in the polarcaps underwent sublimation and transport to lower latitudeswhere it was deposited as a meters-thick dust-rich layer. Thisscenario has been supported by the Gamma Ray/NeutronSpectrometer experiment on board the Mars Odyssey Spacecraft(Feldman et al., 2002) which discovered evidence for nearsubsurface water ice at non-polar high latitudes that is consistentwith the proposed ice ages. A major scientific question is then"What is the nature of the layers in the upper part of the Northpolar cap, what is the distribution of ice in the cold-traps in thecircumpolar area, and how does this information bear on the ageand mode of emplacement of the cap?" Using our Cave IVRenvironment and the ADVISER PSE, we first investigated thedistribution of unusual domical ice deposits within circum-polarimpact craters to constrain the presence and post-emplacementbehavior and stability of this ice (e.g., Russell et al, 2004;Russell and Head, 2005). The terrain visualization capabilityenabled us to visit, explore, and compare these deposits in rapidsuccession. At each candidate cold-trap, we were able to analyzein real-time the interior geometry of the deposits, theirrelationship to internal structure of the crater, their relationshipto crater rim-crest topographic irregularities and resultingvariations in solar illumination, their asymmetry and itscorrelation with solar illumination geometry, and therelationships of deposit geometry to local temperature-pressureconditions and regional wind directions. These data permitted usto test the long-term stability of these features and the role ofinsolation geometry on their shape by detailed modeling (e.g.,Russell et al, 2004; Russell and Head, 2005).

The second part of this analysis focused on the origin oflayers in the North polar layered terrain. Key questions in thisregard are: 1) the nature of layers exposed in the polar cap

troughs (Figure 3a-c), 2) the correlation of these layers fromplace to place, 3) the orientation of these layers throughout thepolar cap, and 4) the relationship of the layer geometry totroughs and the structure of the cap as a whole. The Cave wasan ideal environment in which to address these questions and theADVISER PSE permitted us to derive quantitative data toresolve many of these questions. For example, we superposedViking and related image data on MOLA topography to assessthe broad relationship of topography, trough geometry, and layerorientation (Figure 2a,b), superposed very high resolution MOCimage data (Figure 2c) to examine individual layers, their natureand sequence, and their correlation within and between troughs,and compared the orientation of individual layers in the highresolution data to topographic contours (Figure 2b) to derivelayer orientations (strike and dip). These data and the relatedanalyses permitted us (Milkovich and Head, 2005a) to: 1)recognize four vertical stratigraphic zones in the North polarlayered terrain, 2) detect a fundamental ~30 meter climate signalin the vertical stratigraphic sequence of the upper zone of thelayered terrain, 3) correlate this signal to events associated withthe "recent ice age" (e.g., Head et al., 2003), and 4) estimate theages of various parts of the polar cap. These data and furtherassessment in the Cave and related environments then served asa basis for the analysis of the orientation of layers and theinternal structure of the polar cap (Milkovich and Head,2005b,c).

Tropical Mountain GlaciersWhere does polar ice go during periods of very high obliquity?We have recently described evidence for deposits interpreted torepresent the former presence of giant glaciers on the flanks ofthe major shield volcanoes that straddle the Mars equator (e.g.,Head and Marchant, 2003). Key to the understanding of thesefeatures is the question of the former environmental conditionsunder which ice would accumulate in tropical areas in sufficientquantities to build these extensive glaciers (e.g., Shean et al.,2004). Important to success in this modeling is the visualizationof the general circulation of the atmosphere of Mars underdifferent conditions of orbital obliquity (e.g., Haberle et al.,2003, 2004). We are currently integrating these data to assess thegeneral wind directions and how they might influenceaccumulation and ablation of the deposit interpreted to be atropical mountain glacier. Researchers at NASA Ames ResearchCenter are collaborating to provide the appropriate GCMparameters utilized in this research.

Planning for ExplorationOn the basis of our results in the investigation of the north polarcap layer formation and evolution described above, we haveused these results and outstanding questions in polar studies toformulate an exploration plan for automated and humaninvestigations of this region. Specifically, we have undertakenin cooperation with the NASA Jet Propulsion Laboratory ananalysis (the Palmer Quest design study) of the utility of nuclearpower for the exploration of the polar regions of Mars. Thestudy objectives included: 1) resolving issues of site selectionand access, 2) coordinating the science objectives for a drillingstation designed to penetrate the cap and a rover capabilitydesigned to traverse the cap (see Figure 3d), 3) determining thetypes of scientific measurements to make with both the drill androver platforms, and 4) developing mission architecture andoperational scenarios. We utilized ADVISER to: 1) convert theresults of the science studies described above into specificscience objectives that could be met by these platforms, 2)explored in real time for optimum landing sites from anoperational and illumination geometry point of view, 3)


developed traverses and tested them in terms of surface slopesand other aspects of trafficability (Figure 3e), 4) correlated thesurface exposure of layers with their predicted geometry at depthwithin the cap to optimize operational scenarios for co-planningdrilling and rover operations and measurements.

The capability of ADVISER to put the users "on thesurface" also makes it ideal for planning and training for futurehuman exploration of Mars. We are working with AstronautCandidates at the Johnson Space Center in Houston to developscenarios for such exploration missions.

Ongoing and Future WorkTo date, ADVISER has reached the form of a useful prototypethat demonstrates the potential for planetary geoscientists tooperate and analyze data in a virtual reality problem solvingenvironment as if they were on or near the surface of a planet.We have established interdisciplinary cooperation betweenfaculty, students and staff of the Department of GeologicalSciences, the Computer Sciences Department, and the Center forComputation and Visualization at Brown University that willboth define the needs for further development of the system andlead to its increasing use in academic settings ranging fromfreshmen geology seminars to cutting-edge research. The majorchallenges for ADVISER and corresponding areas of ongoingdevelopment are as follows:

• Interactive image rendering of large data sets. Rendering thehighest resolution available topographic data sets at fullresolution is beyond the capability of current computer graphicssystems, but the volume of data that can be handled and theframe rates achievable continue to increase. Embedding multiplehigh-resolution images (e.g., MOC, THEMIS and HRSC) on aterrain also presents significant computational challenges for therendering program necessitating the use of sophisticated texturesimplification and paging schemes.

• Incorporating climate model data. For problems such asstudying the polar regions on Mars, we need to visualize thegeneral circulation of the martian atmosphere under differentconditions and time scales (e.g., seasons, eccentricity and orbitalobliquity). The primary challenges are designing the generalvisual representation of a high-dimensional data set and scalinga solution to support a simulation result larger than systemmemory.

• Modeling solar insolation. We are working toward a virtualenvironment in which the scientist has control over time (andtherefore sun position) for both small and large scales (e.g.,hours, decades, or hundreds of thousands of years). Thechallenge is computing full global illumination at interactiverates. Many techniques exist for interactively rendering shadowson height-fields, but they are typically approximations and weare striving to make this work interactively on this large-scaledata set.

• Designing for multiple display environments. The challenge forthe ADVISER project in making full use of multiple displaytypes (e.g., monographic desktops, stereographic desktops andtiled wall displays) is designing the look-and-feel for eachworking environment. For example, keyboard and mousecontrol devices for a desktop are not appropriate for use in aCave. Similarly, user interaction metaphors will differ betweensome display environments (e.g., conventional desktop andCave).

• Improved data integration and communication. We aredeveloping a portal system to transmit "virtual field notebook"data and metadata between display platform systems (e.g.,between office and Cave environments), which, among otherbenefits, will facilitate remote collaborative exploration. We are

also improving data management facilities to provide efficientinteractive access to network data repositories.

• Virtual field instruments. We continue to develop the “field kit”and "virtual field instruments" for measuring, probing, orperforming other operations within ADVISER. Many of theseinstruments are inspired by tools used in fieldwork on Earth asdescribed above. Furthermore, other instruments may beinspired by the virtual environment where virtual tools can bebuilt that are hard to create in the real world.

We anticipate that, as it evolves, the ADVISER PSE willencourage and engage multidisciplinary users in the broaderscientific community through ongoing research, presentations atprofessional meetings, and telecollaboration development andexport to other platforms and community members over a widerange of science disciplines.

AcknowledgmentsSupport for this work was provided by NASA through a grantfrom the Applied Information Systems Research Program.

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Immersive Scientific Visualization Applied to Mars Research and Exploration