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  • 1
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    Mars Science with Small Aircraft (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Mars program has articulated a strategy to answer the question "Could Life have arisen on Mars?" by pursuing an in depth understanding of the location, persistence and expression of water in the surface and sub-surface environments. In addition to the need to understand the role of water in climate and climate history, detailed understanding of the surface and interior of the planet is required as well. Return of samples from the Martian surface is expected to provide key answers and site selection to maximize the science gleaned from samples becomes critical. Current and past orbital platforms have revealed a surface and planetary history of surprising complexity. While these remote views significantly advance our understanding of the planet it is clear that detailed regional surveys can both answer specific open questions as well as provide initial reconnaissance for subsequent landed operations.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Concepts and Approaches for Mars Exploration; Part 1; 55-56; LPI-Contrib-1062
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  • 2
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    Survival of life on asteroids, comets and other small bodies (1999)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The ability of living organisms to survive on the smaller bodies in our solar system is examined. The three most significant sterilizing effects include ionizing radiation, prolonged extreme vacuum, and relentless thermal inactivation. Each could be effectively lethal, and even more so in combination, if organisms at some time resided in the surfaces of airless small bodies located near or in the inner solar system. Deep within volatile-rich bodies, certain environments theoretically might provide protection of dormant organisms against these sterilizing factors. Sterility of surface materials to tens or hundreds of centimeters of depth appears inevitable, and to greater depths for bodies which have resided for long periods sunward of about 2 A.U.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Origins of life and evolution of the biosphere : the journal of the International Society for the Study of the Origin of Life (ISSN 0169-6149); Volume 29; 5; 521-45
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  • 3
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    Transient Liquid Water as a Mechanism for Induration of Soil Crusts on Mars (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-11
    Description: The Viking and the Mars Exploration Rover missions observed that the surface of Mars is encrusted by a thinly cemented layer tagged as "duricrust". A hypothesis to explain the formation of duricrust on Mars should address not only the potential mechanisms by which these materials become cemented, but also the textural and compositional components of cemented Martian soils. Elemental analyzes at five sites on Mars show that these soils have sulfur content of up to 4%, and chlorine content of up to 1%. This is consistent with the presence of sulfates and halides as mineral cements. . For comparison, the rock "Adirondack" at the MER site, after the exterior layer was removed, had nearly five times lower sulfur and chlorine content , and the Martian meteorites have ten times lower sulfur and chlorine content, showing that the soil is highly enriched in the saltforming elements compared with rock.Here we propose two alternative models to account for the origin of these crusts, each requiring the action of transient liquid water films to mediate adhesion and cementation of grains. Two alternative versions of the transient water hypothesis are offered, a top down hypothesis that emphasizes the surface deposition of frost, melting and downward migration of liquid water and a bottom up alternative that proposes the presence of interstitial ice/brine, with the upward capillary migration of liquid water.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXV: Mars Missions; LPI-Contrib-1197
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  • 4
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    APXS on Mars: Analyses of Soils and Rocks at Gusev Crater and Meridiani Planum (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-11
    Description: Newly developed APXS (Alpha Particle X-Ray Spectrometers) are part of the Athena payload of the Mars Exploration Rovers Spirit and Opportunity [1]. The APXS determines the chemical composition of soils and rocks along the traverse of the two rovers. Spirit and Opportunity operate at Gusev Crater and Meridiani Planum, respectively. First results of soil X-ray spectra at both landing sites support the hypothesis of a global homogenization of the soil by large dust storms and impact processes in the northern and southern hemisphere.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXV: Mars Missions; LPI-Contrib-1197
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  • 5
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    Overview of the Spirit Mars Exploration Rover Mission to Gusev Crater: Landing Site to Backstay Rock in the Columbia Hills (2005)
    In:  CASI
    Details
    Publication Date: 2018-06-11
    Description: Spirit landed on the floor of Gusev Crater and conducted initial operations on soil covered, rock-strewn cratered plains underlain by olivine-bearing basalts. Plains surface rocks are covered by wind-blown dust and show evidence for surface enrichment of soluble species as vein and void-filling materials and coatings. The surface enrichment is the result of a minor amount of transport and deposition by aqueous processes. Layered granular deposits were discovered in the Columbia Hills, with outcrops that tend to dip conformably with the topography. The granular rocks are interpreted to be volcanic ash and/or impact ejecta deposits that have been modified by aqueous fluids during and/or after emplacement. Soils consist of basaltic deposits that are weakly cohesive, relatively poorly sorted, and covered by a veneer of wind blown dust. The soils have been homogenized by wind transport over at least the several kilometer length scale traversed by the rover. Mobilization of soluble species has occurred within at least two soil deposits examined. The presence of mono-layers of coarse sand on wind-blown bedforms, together with even spacing of granule-sized surface clasts, suggest that some of the soil surfaces encountered by Spirit have not been modified by wind for some time. On the other hand, dust deposits on the surface and rover deck have changed during the course of the mission. Detection of dust devils, monitoring of the dust opacity and lower boundary layer, and coordinated experiments with orbiters provided new insights into atmosphere-surface dynamics.
    Keywords: Lunar and Planetary Science and Exploration
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  • 6
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    Elemental Compositions of Comet 81P/Wild 2 Samples Collected by Stardust (2006)
    In:  CASI
    Details
    Publication Date: 2018-06-11
    Description: We measured the chemical compositions of material from 23 particles in aerogel and residue in 7 craters in aluminum foil, collected during passage of the Stardust spacecraft through the coma of Comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size-scale analyzed, ~180 nanograms. The mean chemical composition of this Wild 2 material agrees with the CI meteorite composition for the refractory elements Mg, Si, Cr, Fe, and Ni to 35%, and for Ca and Mn to 50%. The data suggest the moderately volatile elements Cu, Zn, and Ga may be enriched in this Wild 2 material.
    Keywords: Lunar and Planetary Science and Exploration
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  • 7
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    Results of the Alpha-Particle-X-Ray Spectrometer on Board of the Mars Exploration Rovers (2005)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The Mars Exploration Rovers Spirit and Opportunity landed at Gusev crater and Meridiani Planum. The Alpha Particle X-ray Spectrometer (APXS) is part of the instrument suite on both rovers. It is equipped with six 244Cm sources which provide x-ray excitation with alpha-particles (PIXE) and x-ray radiation (XRF). This combination allows x-ray spectroscopy of elements from Na to Br in the energy range of 0.9 to 16 keV. X-ray detectors with a high energy resolution of 160 eV at Fe K allow us to separate even closely spaced energy peaks, such as Na, Mg, Al and Si. The APXS is attached to the rover s arm and provides in-situ measurements of the chemical composition of soils, surfaces of rocks and outcrops and their abraded surfaces. This abstract gives an overview of APXS results obtained during the first year of operation on both landing sites.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXVI, Part 7; LPI-Contrib-1234-Pt-7
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  • 8
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    Hematite on the Surface of Meridiani Planum and Gusev Crater (2005)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Meridiani Planum was selected as a landing side for the Rover Opportunity because of an indication of hematite observed from orbit. Meridiani Planum consists of sorted sands with aeolian features like ripples and desert pavements. In impact craters, a high-albedo layered bedrock is exposed. The soil is a mixture of: (i) fine sand material in the size ranges of 50 to 150 m, (ii) sub-angular, irregular particles of 0.5 to 5 mm size with submillimeter circular voids that are most likely vesicular basaltic fragments, and (iii) spherules with a restricted grain size between 4 and 6 mm. The Mini-TES on board the rover Opportunity identified a hematite signature at distance resulting from mm-sized spherules as determined by the Moussbauer Spectrometer. Small quantities of similar spherules (2 vol. %) were found in rock exposures in Eagle crater and were interpreted as concretions that formed by precipitation from aqueous fluids inside sedimentary rocks. At Gusev crater no hematite was observed until sol 90 except for layering on a rock. Our investigations of hematite bearing materials, measured by the Alpha Particle X-ray Spectrometer (APXS), Moussbauer Spectrometer (MB), and Microscopic Imager (MI), provide a more integrated view of different occurrences of hematite on the martian surface. Chemistry of soils and rocks: Chemical compositions
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXVI, Part 2; LPI-Contrib-1234-Pt-2
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  • 9
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    Subsurface Weathering of Rocks and Soils at Gusev Crater (2005)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Data collected by the Mars Exploration Rover (MER) Spirit at Gusev Crater suggest that enhanced weathering of rocks and soils occurs beneath the immediate surface. We suggest that this alteration occurs over geological timescales under present climatic conditions and is a result of diurnal condensation of thin-films of water on subsurface materials. Additional information is included in the original extended abstract.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXVI, Part 22; LPI-Contrib-1234-Pt-22
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  • 10
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    Abundance and Speciation of Water and Sulfate at Gusev Crater and Meridiani Planum (2005)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: A major science goal of the Mars Exploration Rover (MER) mission is to search for evidence of water activity, and direct mineralogical evidence for aqueous activity has been reported for Meridiani Planum in the form of the iron sulfate hydroxide mineral jarosite and at Gusev crater in the form of goethite. The Spirit and Opportunity rovers have each collected 110+ Moessbauer (MB) and 75+ Alpha Particle X-Ray Spectrometer (APXS) spectra from Gusev crater and Meridiani Planum [1 - 4]. In this abstract, we use mineralogical and elemental data, primarily from the Moessbauer and APXS instruments, to infer the speciation and estimate the abundance of sulfate and water (as either the H2O molecule or the hydroxyl anion) at Gusev crater and Meridiani Planum. Throughout the abstract, we adopt a format for mineral formulas that shows water explicitly rather than the usual practice of structure-based formulas (e.g., for goethite we write Fe2O3xH2O instead of FeOOH).
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXVI, Part 13; LPI-Contrib-1234-Pt-13
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