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Galileo's Solid State Imaging camera recorded six images at wavelengths from 0.41 to 0.99 [[micro]meter] of Europa's trailing hemisphere ([approximately]1.6 km/pixel resolution) during the G1 orbit (1st orbit - target Ganymede) of the nominal mission. We have photometrically corrected these data and extracted spectra representing Europa's diverse geologic terrains. The goals of the analysis of these spectra are (1) to determine whether Europa's geologic units differ spectrally from one another, (2) to determine the number of color components necessary to explain Europa's dark material spectral behavior, and (3) to examine how europan dark materials may change in color with time. Our data indicate that europan dark spots, lineaments and triple band side materials represent a single 'dark' and reddish endmember component. We see no evidence for more than one dark endmember; however the dark endmember seen in these G1 data is probably not a 'pure' exposure of europan dark material. Mottled terrains, brighter lineaments, and aging triple bands can be modeled by a mixture of bright plains materials and the dark component. Exposures of europan dark materials may thus be brightening with time, eventually blending into the surrounding bright plains. Key Words: Europa; Galileo; multispectral imaging.

During Galileo's G7 orbit, the Solid State Imaging (SSI) camera acquired pictures of the spacecraft shadow point on Europa's surface as well as a comparison set of images showing the same geographic region at phase angle [Alpha] = 5 [degrees]. Coverage, obtained at three spectral bandpasses (VLT, 0.41 [[micro]meter], GRN, 0.56 [[micro]meter]; and 1MC, 0.99 [[micro]meter]) at a spatial resolution of 404 m/pixel, shows a 162 x 220-km region of Europa's surface located at 30 [degrees] N, 162 [degrees] W. We have used these images to measure the near-opposition spectrophotometric behavior of four primary europan terrain materials: IR-bright icy material, IR-dark icy material, dark lineament material, and dark spot material. The high spatial resolution of the G7 images reveal low-albedo materials in dark spots that are among the darkest features (17% albedo at 0.56 [[micro]meter] and 5 [degrees] phase) yet found on icy Galilean satellites. While material of comparable albedo is found on Ganymede and Callisto, low-albedo europan materials are much redder. All europan surface materials exhibit an opposition effect; however, the strength of the effect, as measured by the total increase in reflectance as phase angle decreases from [Alpha] = 5 [degrees] to [Alpha] = 0 [degrees], varies among terrains. The opposition effects of IR-bright icy and IR-dark icy materials which dominate Europa's surface are about 1.5 times larger than predicted from pre-Galileo studies. Low-albedo materials in dark spots exhibit unusually intense opposition effects (up to four times larger than bright icy europan terrains), consistent with the presence of a strong shadow-hiding opposition surge. The strengths of the opposition surges among average europan terrains systematically vary with terrain albedo and can be explained in terms of the simultaneous contributions of shadow-hiding and coherent-backscatter to the total opposition effect. Coherent backscatter introduces a narrow angular contribution ( Key Words: Europa; photometry; regolith; spectrophotometry; ices; albedo; spectra; geological processes; Galileo; Voyager.

Four distinct classes of lineaments can be described on the basis of Galileo's improved spectral and spatial coverage of Europa: (1) incipient cracks are narrow (

Ma'adim Vallis and Gusev crater (Aeolis subquadrangle of Mars) formed a complex hydrogeologic system through time. Crater statistics over five geologic units, coupled with morphologic and geologic observations, show that this system was active over a period ranging from 0.7 to about 2 billion years. These results make the floor of Gusev crater one of the most prominent martian depositional features. The last aqueous sedimentary deposition could have occurred during Early Amazonian. Key Words: Mars; surface; geological processes; planets.

The surface of 243 Ida is dominated by the effects of impacts. No complex crater morphologies are observed. A complete range of crater degradation states is present, which also reveals optical maturation of the surface (darkening and reddening of materials with increasing exposure age). Regions of bright material associated with the freshest craters might be ballistically emplaced deposits or the result of seismic disturbance of loosely-bound surface materials. Diameter/depth ratios for fresh craters on Ida are [approximately]1:6.5, similar to Gaspra results, but greater than the 1:5 ratios common on other rocky bodies. Contributing causes include rim degradation by whole-body 'ringing,' relatively thin ejecta blankets around crater rims, or an extended strength gradient in near-surface materials due to low gravitational self-packing. Grooves probably represent expressions in surface debris of reactivated fractures in the deeper interior. Isolated positive relief features as large as 150 m are probably ejecta blocks related to large impacts. Evidence for the presence of debris on the surface includes resolved ejecta blocks, mass-wasting scars, contrasts in color and albedo of fresh crater materials, and albedo streaks oriented down local slopes. Color data indicate relatively uniform calcium abundance in pyroxenes and constant pyroxene/olivine ration. A large, relatively blue unit across the northern polar area is probably related to regolith processes involving ejecta from Azzurra rather than representing internal compositional heterogeneity. A small number of bluer, brighter craters are randomly distributed across the surface, unlike on Gaspra where these features are concentrated along ridges. This implies that debris on Ida is less mobile and/or consistently thicker than on Gaspra. Estimates of the average depth of mobile materials derived from chute depths (20-60 m), grooves ([greater than or equal to]30 m), and shallowing of the largest degraded craters (20-50 m minimum, [approximately]100 m maximum) suggest a thickness of potentially mobile materials of [approximately]50 m, and a typical thickness for the debris layer of 50-100 m.

The grooves on the surface of asteroid 951 Gaspra are fractures modified by the inward drainage of regoliths with depths ranging from 30 to 200 meters. The regoliths are noncohesive substances of various sizes. The presence of grooves indicate that Gaspra was subjected to violent collisions with other astronomical objects.

Abstract: On-board detection of cryospheric change in sea ice, lake ice, and snow cover is being conducted as part of the Autonomous Sciencecraft Experiment (ASE), using classifiers developed for the Hyperion hyper-spectral visible/infrared spectrometer on-board the Earth Observing-1 (EO-1) spacecraft. This classifier development was done with consideration for the novel limitations of on-board processing, data calibration, spacecraft targeting error and the spectral range of the instrument. During on-board tests, these algorithms were used to measure the extent of cloud, snow, and ice cover at a global suite of targets. Coupled with baseline imaging, uploaded thresholds were used to detect cryospheric changes such as the freeze and thaw of lake ice and the formation and break-up of sea ice. These thresholds were used to autonomously trigger follow-up observations, demonstrating the capability of the technique for future planetary missions where downlink is a constrained resource and there is high interest in data covering dynamic events, including cryospheric change. Before upload classifier performance was assessed with an overall accuracy of 83.3% as measured against manual labeling of 134 scenes. Performance was further assessed against field mapping conducted at Lake Mendota, Wisconsin as well as with labeling of scenes that were classified during on-board tests. [Copyright &y& Elsevier]

Abstract: Missions to explore Europa have been imagined ever since the Voyager mission first suggested that Europa was geologically very young. Subsequently, the Galileo spacecraft supplied fascinating new insights into this satellite of Jupiter. Now, an international team is proposing a return to the Jupiter system and Europa with the Europa Jupiter System Mission (EJSM). Currently, NASA and ESA are designing two orbiters that would explore the Jovian system and then each would settle into orbit around one of Jupiter’s icy satellites, Europa and Ganymede. In addition, the Japanese Aerospace eXploration Agency (JAXA) is considering a Jupiter magnetospheric orbiter and the Russian Space Agency is investigating a Europa lander. The Jupiter Europa Orbiter (JEO) would be the NASA-led portion of the EJSM; JEO would address a very important subset of the complete EJSM science objectives and is designed to function alone or in conjunction with ESA’s Jupiter Ganymede Orbiter (JGO). The JEO mission concept uses a single orbiter flight system that would travel to Jupiter by means of a multiple-gravity-assist trajectory and then perform a multi-year study of Europa and the Jupiter system, including 30months of Jupiter system science and a comprehensive Europa orbit phase of 9months. The JEO mission would investigate various options for future surface landings. The JEO mission science objectives, as defined by the international EJSM Science Definition Team, include: [A.] Europa’s ocean: Characterize the extent of the ocean and its relation to the deeper interior. [B.] Europa’s ice shell: Characterize the ice shell and any subsurface water, including their heterogeneity, and the nature of surface–ice–ocean exchange. [C.] Europa’s chemistry: Determine global surface compositions and chemistry, especially as related to habitability. [D.] Europa’s geology: Understand the formation of surface features, including sites of recent or current activity, and identify and characterize candidate sites for future in situ exploration. [E.] Jupiter system: Understand Europa in the context of the Jupiter system. The JEO orbital mission would provide critical measurements to support the scientific and technical selection of future landed options. The primary challenge of a Europa mission is to perform in Jupiter’s radiation environment, radiation damage being the life-limiting parameter for the flight system. Instilling a system-level radiation-hardened-by-design approach very early in the mission concept would mitigate the pervasive mission and system-level impacts (including trajectory, configuration, fault protection, operational scenarios, and circuit design) that can otherwise result in runaway growth of cost and mass. This paper addresses the JEO mission concept developed by a joint team from JPL and the Applied Physics Laboratory to address the science objectives defined by an international science definition team formed in 2008, while designing for the Jupiter environment. [Copyright &y& Elsevier]

Abstract: The morphology and topography of volcanic landforms provide critical information to the investigation of their tectonic setting and the physical characteristics (e.g., rheology) of their eruption products. Their investigation is also an important prerequisite for studies of comparative planetology, (e.g., the comparison between surface features of the Earth and other planetary bodies). Numerous small and low shield volcanoes on Mars and associated vents and lava flows have previously been compared to terrestrial plains-style volcanism, which is defined as being an intermediate style between flood basalts and the Hawai''ian shields. This study investigates the topography and morphology of Martian landforms associated with plains volcanism using MOLA, MOC, THEMIS, HRSC, and HiRISE data. Low shields and other landforms of plains volcanism on Mars display similarities with terrestrial basaltic volcanic fields, and we do not observe any features that do not have morphologic analogues on Earth. The most typical landforms of Martian plains-style volcanism are low shields, defined as volcanic shields with diameters of typically less than 50 km, heights of a few hundred meters only, and extremely shallow flank slopes of less than 0.5°. Other surface features related to plains-style volcanism on Mars are craters, fissure vents, cinder and spatter cones, lava flows (that are commonly associated with lava channels and tubes), lava inflation features, and volcanic rift zones. Our results reconfirm the Viking Orbiter-based conclusion that plains volcanism in the eastern Snake River Plains is perhaps the best terrestrial morphological analogue for these Martian surface features. Icelandic shields, distinct structures in Hawai''i, and other basaltic landforms also show similarities to Martian plains volcanism. Sinuous rilles, previously not described in association with plains volcanism on Mars, are interpreted as evidence for high eruption rates. The extremely shallow flank slopes of the low shields suggest the eruption of shield-building lavas with low viscosity, which might be the result of high eruption temperatures, high effusion rates, a low Si- and a high Mg-content along with a possible high Fe-content, or a combination of these factors. The spatial distribution of low shield clusters in Tharsis does not show any obvious association with large-scale tectonic features. Plains volcanism might represent a relatively recent type of volcanism on Mars, which is not related to mantle plumes but to a zone of partial melting in an anomalously warm mantle underneath a thickened crust (Schumacher and Breuer, Geophys. Res. Lett. 34, L14202, doi: 10.1029/2007GL030083, 2007). [Copyright &y& Elsevier]

Abstract: This paper focuses on the shape of 31 shield volcanoes of small to intermediate size (a few tens of kilometers in diameter) in 5 regions of Mars: Tempe Terra, Syria Planum, Pavonis Mons, Arsia Mons and central Elysium Planitia. A model for the shape of these shield volcanoes is applied, based upon the concept of porous flow of an unconfined aquifer proposed by Lacey et al. [Lacey, A., Ockendon, J.R., Turcotte, D.L., 1981. On the geometrical form of volcanoes, Earth Planet. Sci. Lett., 54(1), 139–143] and developed by Turcotte and Schubert [Turcotte, D., Schubert, G., 2002. Geodynamics. Cambridge University Press, second edition]. The agreement between the topographic profiles and the theoretical shape suggests that the model is appropriate and can be used to derive the product of flow rate and viscosity (Qµ). Estimates of Qµ are found to be homogeneous within a given volcanic region, but show large differences from one region to another, values generally decreasing with age (from oldest to youngest). Intrinsically, the method cannot separate the flow rate from the viscosity, but independent observations on individual lava flows in Syria Planum and central Elysium Planitia suggest that this evolution may be explained by decreasing magma viscosity with age. Independent constraints on the viscosity are used to interpret Q variations between volcanic regions. Except for Tempe Terra, and within error bars, relative effusion rates are essentially independent of volcano volumes, suggesting that the size of a shield volcano is principally controlled by the duration of volcanic activity. The specificity of central Elysium Planitia is emphasized, with highest flow rates associated with lowest lava viscosity. However, the lower viscosities at central Elysium Planitia cannot totally explain low Qµ values. Considering the equation of magma flow through a dike from a magma chamber at depth, to the shield, we suggest that lower volatile contents and/or deeper magma chambers may contribute to the decrease of Qµ values with time. Finally, the emplacement times of the 31 shield volcanoes were calculated using a calibration based upon terrestrial volcanoes Mauna Loa, Eldborgir, and Skjalbreiður. Emplacement times of martian volcanoes calculated in this way range from a few hundred thousand years (Tempe Terra) to a few tens of thousands of years (central Elysium Planitia). Despite the simplicity of the model, the quality of the fits and the internal consistency of the results are reasonable, encouraging development of more advanced models linking shield volcano shape to rheological properties of lavas and their characteristic time-scales of emplacement. [Copyright &y& Elsevier]

Abstract: The ability to monitor and rapidly react to remote detection of volcanic activity has been greatly improved through use of the Autonomous Sciencecraft Experiment (ASE), an advanced software application installed on a spacecraft in Earth orbit. ASE is a NASA New Millennium Program experiment demonstrating science-driven autonomous command and control of a spacecraft. Flying on the Earth Observing-1 (EO-1) spacecraft, ASE successfully detected thermal emission from the Mt. Erebus lava lake on 7 May 2004, having analyzed a Hyperion hyperspectral data product on board the spacecraft. EO-1 was re-tasked by ASE to obtain a follow-up observation 7 h later and sent a notification of detection of volcanic activity to the ground. The entire process was carried out autonomously. Initial acquisition to receipt on the ground of the positive detection took less than 3 h, a process that without ASE would have taken weeks. The ASE Thermal Classifier has detected several styles of effusive volcanic activity: active lava lakes, pahoehoe flow fields, open channel flows and lava domes. ASE successfully demonstrated that science-driven spacecraft operation greatly enhances science return per returned byte through the identification of the most valuable data, allowing prioritization of downlink products and the discarding of null data sets. This technology has applications on missions elsewhere in the solar system. Modified thermal classifiers can be used for detecting and monitoring active volcanism on the jovian satellite Io, the neptunian moon Triton, and searching for active volcanism on Mars and icy satellites. The success of ASE is an incentive for future instrument and mission designers to consider on-board data-processing requirements (especially data storage capacity, number of processors and processor speed, and RAM) in order to take advantage of this flight-proven technology. [Copyright &y& Elsevier]

Abstract: In this paper, we present a new way of detecting and monitoring flooding through the Autonomous Sciencecraft Experiment (ASE) [Chien, S. T., Debban, C., Yen, R., Sherwood, R. Castano, B., & Cichy, A. G. et al. (2001). ASC Science Study Report, available from http://ASE.jpl.nasa.gov], which is part of the Space Technology 6 effort under NASA''s New Millennium Program. Recent autonomy experiments conducted on Earth Observing 1 (EO-1) using the ASE flight software have demonstrated the ability of several science algorithms to successfully classify key features including flood-induced changes, in hyperspectral images captured by the EO-1 Hyperion instrument. Furthermore, onboard science analysis on the classified images has been performed, and then used to modify an operational plan without interaction from the ground (Sherwood, R., Chien, S., Tran, D., Cichy, B., Castano, R., Davies, A., et al. (2004). Preliminary results of the autonomous sciencecraft experiment. In: Proceedings of the IEEE Aerospace Conference, Big Sky, MT). These algorithms are used to downlink science data only when change occurs, and to detect features of scientific interests such as flooding, volcanic eruptions, and the formation and breakup of sea ice. The purpose of this paper is to demonstrate the success of ASE and its implications on detecting, mapping, and monitoring transient processes such as flooding autonomously from space. Mapping of water inundation and its change through time is part of our focus in studying transient processes from space. In 2004, hyperspectral data were acquired from the Hyperion instrument for target areas around the world that have a high potential for flooding to develop and test floodwater classifiers. In addition, classifier thresholds were determined from both normal flows and possible flood conditions. The paper introduces the development, testing, and success of the ASE software in detecting and reacting to flooding in near real-time. ASE is now operational and flight-tested, and, thus, ready to use for space-borne reconnaissance. Successful demonstration of the floodwater classifiers includes the capture of a rare flooding event of the Australian Diamantina River during ground testing in February 2004, and the detection of flood-related changes along the Brahmaputra River in Bangladesh and the Yukon River in Alaska during onboard testing on EO-1 in 2005. Both of these detections led to triggered responses onboard the spacecraft, which included acquiring additional Hyperion scenes. These results pave the way for future smart reconnaissance missions of transient processes on Earth and beyond. It is hoped that ASE will become a default in future missions to increase the science return by introducing spacecraft autonomy for detection and monitoring of science events, which otherwise would be discovered too late or altogether missed. [Copyright &y& Elsevier]