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Mars Odyssey Gamma Ray Spectrometer elemental abundances and apparent relative surface age: Implications for Martian crustal evolution
Department of Geosciences, State University of New York–Stony Brook, New York, USA
Department of Geosciences, State University of New York–Stony Brook, New York, USA
Hawaii Institute of Geophysics and Planetology, Honolulu, Hawaii, 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
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
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Quantifying secular variations in the chemical composition of the Martian crust provides unique insights into the processes that have guided the evolution of the Martian crust-mantle system. Using global abundances for a suite of elements determined by the Gamma Ray Spectrometer (GRS) on board the Mars Odyssey spacecraft and global mapping of apparent surface age adapted from existing geologic maps in the USGS Martian Geologic Investigation series, we report the average abundance of K, Th, Fe, Cl, H, and Si for the major Martian geologic epochs (Noachian, Hesperian, and Amazonian). Average GRS-determined K and Th abundances generally decrease by 9% and 7%, respectively, between the Hesperian and the Amazonian, possibly implying evolving magma chemistry throughout major resurfacing events (although the effects of surficial alteration processes cannot be entirely discounted). GRS-determined Fe and Cl averages increase by 12% and 19%, respectively, with younger apparent relative surface age, suggesting the possible mobilization and transport of these elements through aqueous processes (although an igneous origin for the variation in Fe also cannot be excluded). While H abundance does vary with surface age, the relationship is likely not governed by geologic processes. No statistically reliable apparent surface age relation was found for Si.
Received 29 August 2006; accepted 15 November 2006; published 25 January 2007.
Citation: (2007), Mars Odyssey Gamma Ray Spectrometer elemental abundances and apparent relative surface age: Implications for Martian crustal evolution, J. Geophys. Res., 112, E03S11, doi:10.1029/2006JE002821.
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