Abstract
Concentration of H, Si, Cl, K, Fe, and Th in the low- and mid-latitude regions of Mars
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
Science Programs, Computer Sciences Corporation, Lanham, Maryland, USA
Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
Department of Physics, Catholic University of America, Washington, D. C., USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
TechSource, Santa Fe, New Mexico, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA
Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA
Department of Chemistry, University of California, San Diego, La Jolla, California, USA
Max-Planck-Institut für Chemie, Mainz, Germany
Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
Centre d'Etude Spatiale des Rayonnements, CNRS/UPS, Toulouse, France
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Space Research Institute (IKI), Moscow, Russia
Center for Radiophysics and Space Research, Cornell University, Ithaca, New York, USA
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Centre d'Etude Spatiale des Rayonnements, CNRS/UPS, Toulouse, France
Max-Planck-Institut für Chemie, Mainz, Germany
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
We report maps of the concentrations of H, Si, Cl, K, Fe, and Th as determined by the Gamma Ray Spectrometer (GRS) on board the 2001 Mars Odyssey Mission for ±∼45° latitudes. The procedures by which the spectra are processed to yield quantitative concentrations are described in detail. The concentrations of elements determined over the locations of the various Mars landers generally agree well with the lander values except for Fe, although the mean of the GRS Fe data agrees well with that of Martian meteorites. The water-equivalent concentration of hydrogen by mass varies from about 1.5% to 7.5% (by mass) with the most enriched areas being near Apollinaris Patera and Arabia Terra. Cl shows a distribution similar to H over the surface except that the Cl content over Medusae Fossae is much greater than elsewhere. The map of Fe shows enrichment in the northern lowlands versus the southern highlands. Silicon shows only very modest variation over the surface with mass fractions ranging from 19% to 22% over most of the planet, though a significant depletion in Si is noted in a region west of Tharsis Montes and Olympus Mons where the Si content is as low as 18%. K and Th show a very similar pattern with depletions associated with young volcanic deposits and enrichments associated with the TES Surface Type-2 material. It is noted that there appears to be no evidence of significant globally distributed thick dust deposits of uniform composition.
Received 5 January 2007; accepted 2 August 2007; published 21 December 2007.
Citation: (2007), Concentration of H, Si, Cl, K, Fe, and Th in the low- and mid-latitude regions of Mars, J. Geophys. Res., 112, E12S99, doi:10.1029/2007JE002887.
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