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In the Inner Basin of the Columbia Hills, Gusev Crater is Home Plate, an 80 m platform of layered elastic rocks of the Barnhill class with microscopic and macroscopic textures, including a bomb sag, suggestive of a phreatomagmatic origin. We present data acquired by the Spirit Mars Exploration Rover by Alpha Particle X-Ray Spectrometer (APXS), Mo??ssbauer Spectrometer, Miniature Thermal Emission Spectrometer (Mini-TES), and Panoramic Camera (Pancam) for the Barnhill class rocks and nearby vesicular Irvine class basalts. In major element concentrations (e.g., SiO2, Al2O3, MgO, and FeO*), the two rock classes are similar, suggesting that they are derived from a similar magmatic source. The Barnhill class, however,...
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Widespread, several-kilometer-thick successions of layered deposits occur as mounds that partly fill the troughs or chasmata that compose the Valles Marineris on Mars. Like terrestrial subice volcanoes, the layered deposits occur in a volcano-tectonic setting within basins that may have held ponded water or ice. On the basis of their dimensions, morphologies, and associated catastrophic floods and other geologic events as shown in Viking and new Mars Global Surveyor (MGS) data sets, we suggest that the interior deposits are volcanic in origin and possibly generated by subice eruptions. A tuya origin for the mounds can explain the lack of external sediment, mound heights that can rival the plateau, local flat-topped...
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The Mars Exploration Rover Spirit analyzed multiple occurrences of sulfur-rich, light-toned soils along its traverse within Gusev Crater. These hydrated deposits are not readily apparent in images of undisturbed soil but are present at shallow depths and were exposed by the actions of the rover wheels. Referred to as 'Paso Robles' class soils, they are dominated by ferric iron sulfates, silica, and Mg-sulfates. Ca-sulfates, Ca-phosphates, and other minor phases are also indicated in certain specific samples. The chemical compositions are highly variable over both centimeter-scale distances and between the widely separated exposures, but they clearly reflect the elemental signatures of nearby rocks. The quantity...
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We have developed an observational scheme for the detection and discrimination of Mars atmospheric H2O and CO2 clouds using ground-based instruments in the near infrared. We report the results of our cloud detection and characterization study using Mars near IR images obtained during the 1990 and 1993 oppositions. We focused on specific wavelengths that have the potential, based on previous laboratory studies of H2O and CO2 ices, of yielding the greatest degree of cloud detectability and compositional discriminability. We have detected and mapped absorption features at some of these wavelengths in both the northern and southern polar regions of Mars. Compositional information on the nature of these absorption features...
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We examine the various methods and parameters in common use for quantifying and reporting surface topographic "roughness." It is shown that scale-dependent roughness parameters are almost always required, though not widely used. We suggest a method of standardizing the parameters that are computed and reported so that topographic data gathered by different workers using different field techniques can be directly and easily intercompared. We illustrate the proposed method by analyzing topographic data from 60 different surfaces gathered by five different groups and examine the information for common features. We briefly discuss the implications of our analysis for studies of planetary surface roughness, lander safety,...
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The Missouri River floods of 1993 caused significant and widespread damage to the floodplains between Kansas City and St. Louis. Immediately downstream of levee breaks, flood waters scoured the bottoms. As the floodwaters continued, they spread laterally and deposited massive amounts of sand as crevasse splays on top of agricultural fields. We explore the use of radar interferometry and backscatter data for quantitative estimation of scour and deposition for Jameson Island/Arrow Rock Bottoms and Lisbon Bottoms, two bottoms that were heavily damaged during the floods and subsequently abandoned. Shuttle imaging radar C (SIR-C) L band (24 cm) HH (horizontally transmitted and horizontally received) radar backscatter...
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The Thermal Emission Spectrometer (TES) investigation on Mars Global Surveyor (MGS) is aimed at determining (1) the composition of surface minerals, rocks, and ices; (2) the temperature and dynamics of the atmosphere; (3) the properties of the atmospheric aerosols and clouds; (4) the nature of the polar regions; and (5) the thermophysical properties of the surface materials. These objectives are met using an infrared (5.8- to 50-??m) interferometric spectrometer, along with broadband thermal (5.1-to 150-??m) and visible/near-IR (0.3- to 2.9-??m) radiometers. The MGS TES instrument weighs 14.47 kg, consumes 10.6 W when operating, and is 23.6 ?? 35.5 ?? 40.0 cm in size. The TES data are calibrated to a 1-?? precision...
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The Marsokhod rover returned data from six stations that were used to decipher the geomorphology and geology of a region not previously visited by members of the geomorphology field team. Satellite images and simulated descent images provided information about the regional setting. The landing zone was on an alluvial apron flanking a mountain block to the west and a playa surface to the east. Rover color images, infrared spectra analysis of the mountains, and the apron surface provided insight into the rock composition of the nearby mountains. From the return data the geomorphology team interpreted the region to consist of compressionally deformed, ancient marine sediments and igneous rocks exposed by more recent...
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If the large Late Hesperian outflow channels were eroded by extensive floods, as appears likely, then large bodies of water must have once occupied the northern plains during that period. Previous estimates of the sizes of bodies of water in the northern lowlands range up to 3 ?? 108 km3. Several contacts have been previously mapped around the edges of the northern plains and interpreted to be shorelines remaining from these former standing bodies of water. We examine the elevations and geologic relations along these contacts in detail and find little support for their interpretation as shorelines. Some contacts are clearly of volcanic origin, and all have significant variations in elevation. Better support for...
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The Miniature Thermal Emission Spectrometer (Mini-TES) on board the Mars Exploration Rover Spirit is part of a payload designed to investigate whether a lake once existed in Gusev Crater. Mini-TES has observed hundreds of rocks along the rover's traverse into the Columbia Hills, yielding information on their distribution, bulk mineralogy, and the potential role of water at the site. Although dust in various forms produces contributions to the spectra, we have established techniques for dealing with it. All of the rocks encountered on the plains traverse from the lander to the base of the Columbia Hills share common spectral features consistent with an olivine-rich basaltic rock known as Adirondack Class. Beginning...
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We catalog 143 Ionian mountains (montes) and mountain‐like features (mensae, tholi, plana, and small peaks) in order to investigate orogenic tectonism on Io. From this comprehensive list, we select 96 mountains for which there are sufficient coverage and resolution to discern spatial relationships with surrounding geologic features. Three of the 96 mountains are probably volcanoes, 92 appear to be tectonic massifs, and 1 is ambiguous. Of the 92 tectonic mountains, 38 abut paterae (volcanic or volcano‐tectonic craters with irregular or scalloped margins). This juxtaposition is unlikely to be a coincidence as the probability of it occurring by chance is ∼0.1%. We propose instead that orogenic faults may act as conduits...
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Congruous with earlier work, Martian soil along the Spirit Rover's traverse at Gusev crater can be divided into three broad groups by size: fines (<150 μm), sand, and a mix of various grain sizes. The key chemical observation is greater homogeneity in fines relative to the other two, consistent with regional‐ and global‐scale sampling of chemical compositions by finer particle sizes. The mix class is generally more heterogeneous as are samples from the Columbia Hills within each class. Variation in the trace element Ni is consistent with a CI contribution not exceeding 3%, while that of Ti is compatible with Fe‐Ti oxide enrichment not exceeding 3%. Physical mixing models are poorly supported. Among many potential...
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In January 2004 the Mars Exploration Rover mission will land two rovers at two different landing sites that show possible evidence for past liquid‐water activity. The spacecraft design is based on the Mars Pathfinder configuration for cruise and entry, descent, and landing. Each of the identical rovers is equipped with a science payload of two remote‐sensing instruments that will view the surrounding terrain from the top of a mast, a robotic arm that can place three instruments and a rock abrasion tool on selected rock and soil samples, and several onboard magnets and calibration targets. Engineering sensors and components useful for science investigations include stereo navigation cameras, stereo hazard cameras...
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Viking infrared thermal mapping and bistatic radar data suggest that the bulk density of the north polar erg material is much lower than that of the average Martian surface or of dark dunes at lower latitudes. We have derived a thermal inertia of 245–280 J m−2 s−1/2 K−1 (5.9–6.7×10−3 cal cm−2 s−1/2 K−1) for the Proctor dune field and 25–150 J m−2 s−1/2 K−1 (0.6–3.6×10−3cal cm−2 s−1/2 K−1) for the north polar erg. The uniqueness of the thermophysical properties of the north polar erg material may be due to a unique polar process that has created them. The visible and near‐infrared spectral reflectance of the erg suggests that the dark material may be composed of basalt or ferrous clays. These data are consistent...
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The Imager for Mars Pathfinder (IMP) was used to observe several objects during the Martian night. The satellites, Phobos and Deimos, were observed on two occasions each, through the IMP geological filters covering the wavelength range 440 nm to 1 μm. The observations were converted to geometric albedo using triaxial ellipsoid models of the satellites and phase functions derived from Viking Orbiter images. The spectral slopes over the full wavelength range were 7.9(±0.5)% (100 nm)−1 and 9.6(±0.6)% (100 nm)−1, respectively, referenced to 600 nm. In the Deimos spectra, some evidence for decreased reddening toward the trailing hemisphere was found. The geometric albedoes of Phobos and Deimos were found to be 0.065...
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The localized lunar dark mantle deposits (DMDs) in Alphonsus, J. Herschel, and Oppenheimer craters were analyzed using visible-near-infrared spectroscopy data from the Moon Mineralogy Mapper. Spectra of these localized DMDs were analyzed for compositional and mineralogical variations within the deposits and were compared with nearby mare basalt units. Spectra of the three localized DMDs exhibited mafic absorption features indicating iron-rich compositions, although the DMDs were spectrally distinct from nearby mare basalts. All of the DMDs contained spectral signatures of glassy materials, suggesting the presence of volcanic glass in varying concentrations across the individual deposits. In addition, the albedo...
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Imaging spectroscopy is a tool that can be used to spectrally identify and spatially map materials based on their specific chemical bonds. Spectroscopic analysis requires significantly more sophistication than has been employed in conventional broadband remote sensing analysis. We describe a new system that is effective at material identification and mapping: a set of algorithms within an expert system decision‐making framework that we call Tetracorder. The expertise in the system has been derived from scientific knowledge of spectral identification. The expert system rules are implemented in a decision tree where multiple algorithms are applied to spectral analysis, additional expert rules and algorithms can be...
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One of the major Mars discoveries of recent years is the existence of recurring slope lineae (RSL), which suggests that liquid water occurs on or near the surface of Mars today. These dark and narrow features emerge from steep, rocky exposures and incrementally grow, fade, and reform on a seasonal basis and are detected in images from the High Resolution Imaging Science Experiment camera. RSL are known to occur at scattered midlatitude and equatorial sites with little spatial connection to one another. One major exception is the steep, low-albedo slopes of Melas and Coprates Chasmata, in Valles Marineris where RSL are detected among diverse geologic surfaces (e.g., bedrock and talus) and landforms (e.g., inselbergs...
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The Moon Mineralogy Mapper (M3) acquired high spatial and spectral resolution data of the Aristarchus Plateau with 140 m/pixel in 85 spectral bands from 0.43 to 3.0 m. The data were collected as radiance and converted to reflectance using the observational constraints and a solar spectrum scaled to the Moon-Sun distance. Summary spectral parameters for the area of mafic silicate 1 and 2 m bands were calculated from the M3 data and used to map the distribution of key units that were then analyzed in detail with the spectral data. This analysis focuses on five key compositional units in the region. (1) The central peaks are shown to be strongly enriched in feldspar and are likely from the upper plagioclase-rich crust...
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[1] A relationship between deep moonquake occurrence and tidal forcing is suggested by the monthly periodicities observed in the occurrence times of events recorded by the Apollo Passive Seismic Experiment. In addition, the typically large S wave to P wave arrival amplitude ratios observed on deep moonquake seismograms are indicative of shear failure. Tidal stress, induced in the lunar interior by the gravitational influence of the Earth, may influence moonquake activity. We investigate the relationship between tidal stress and deep moonquake occurrence by searching for a linear combination of the normal and shear components of tidal stress that best approximates a constant value when evaluated at the times of moonquakes...