Assessment of Mars Science and Mission Priorities (2003) / Chapter Skim
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3. Geochemistry and Petrology
3. Geochemistry and Petrology
Pages 18-25
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From page 18... ...
Studies of meteorites that are inferred to have come from Mars. These sources provide some zero-order compositional data on elemental concentrations in rocks and regolith at a few discrete sites on the planet; limited basic characterization of the global distribution of rock types; and some very detailed knowledge of rocks presumed to come from Mars (the meteorites)
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From page 19... ...
McSween, Jr., "The Chemical Composition of Martian Soil and Rocks Returned by the Mobile Alpha Proton X-ray Spectrometer: Preliminary Results from the X-ray Mode," Science 278: 1771-1774, 1997. Copyright 1997 by the American Association for the Advancement of Science.
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From page 20... ...
The basaltic meteorites have a high Fe/Mg ratio and low A1 content relative to terrestrial basalts, and all of the SNC meteorites have oxide minerals consistent with formation under highly oxidizing conditions. The compositions of these meteorites have been used by two different groups to estimate the bulk composition of Mars.~7 i~ i9 Though the models disagree on the extent of fractionation among the refractory elements, both models agree that the composition of the martian mantle is similar to that of Earth but with some important differences: Mars is richer in Fe3+ and in abundances of moderately volatile elements.
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From page 21... ...
Jones24 and Longhi,25 using estimated magma compositions and constraints provided by radiogenic isotopic composition, concluded that the sources for the SNC magmas had time-integrated LREE depletions significantly greater than those of terrestrial magmas. Small degrees of melting of this source could produce the parent magmas of the nakhlites and Chassigny.
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From page 22... ...
It may be possible to calculate the normative mineralogy from the chemical composition, as was done for the rocks analyzed by Pathfinder; but in an environment where significant amounts of weathering may have occurred, such a calculated mineralogy could be very misleading. Mars Exploration Rovers 2003 The Mars Exploration Rovers (MERs)
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From page 23... ...
Mars Pathfinder's APXS investigation, as outlined above, has satisfied the objective for a gross chemical analysis, but only of one rock type at one locality. Mars Global Surveyor's TES instrument has returned global spectral thermal emission data, from which a mineralogic assessment of low-albedo, basaltic, and basalticandesite terrains has been derived.303i However, it has been more problematic to determine the modal mineralogy of other regions, probably because of the confounding effects of the poorly crystalline martian dust, and thus it seems unlikely that detailed quantitative mineralogical data of the type recommended by COMPLEX will come out of that investigation.
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From page 24... ...
Clark, "Compositional Variability of Martian Olivines Using Mars Global Surveyor Thermal Emission Spectra," Lunar and Planetary Science Conference 32, Abstract #2049, 2001.
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From page 25... ...
28. Space Studies Board, National Research Council, The Search for Life's Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990.
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