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Geochemistry of Martian soil and bedrock in mantled and less mantled terrains with gamma ray data from Mars Odyssey
Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
New Mexico Museum of Natural History and Science, Albuquerque, New Mexico, USA
Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
Computer Sciences Corporation, Latham, Maryland, USA
Hawaii Institute of Geophysics and Planetology and NASA Astrobiology Institute, Honolulu, Hawaii, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Department of Astronomy, Cornell University, Ithaca, New York, USA
Surficial materials, including soil and dust, are abundant in the upper tens of centimeters of the Martian surface sensed by the Mars Odyssey Gamma Ray Spectrometer (GRS). Seven large areas (14% of the Martian surface) that represent possible compositional end-members were selected, including three regions heavily mantled with surficial materials. The selection process included mapping the ratio of exposed rocky terrain to surficial materials using high-resolution imagery. GRS data for H, Cl, Fe, Si, K, and Th were obtained for each area. The areas are chemically homogeneous within each area, given the spatial resolution and analytical uncertainty of the GRS data. However, substantial chemical differences exist among the areas, including the different mantled terrains, contrary to earlier assumptions that surficial materials are globally homogeneous due to aeolian mixing. The observed chemical differences among the areas may be due to variations in the protolith compositions, extent of alteration of the protolith regions, or post soil formation processes. The abundances of Cl, K, and Th in rockier (but still soil-rich) areas such as Syrtis Major Planum can be explained by mixing between a soil with higher concentrations of Cl, K, and Th, similar to the abundances in the mantled terrains (and some of the landing sites), and crustal rocks containing lower abundances of these elements, similar to Martian meteorites.
Received 20 January 2006; accepted 15 December 2006; published 16 February 2007.
Citation: (2007), Geochemistry of Martian soil and bedrock in mantled and less mantled terrains with gamma ray data from Mars Odyssey, J. Geophys. Res., 112, E03S12, doi:10.1029/2006JE002680.
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