Mars Odyssey Gamma Ray Spectrometer elemental abundances and apparent relative surface age: Implications for Martian crustal evolution

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Read Full Article (file size: 491110 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, E03S11, doi:10.1029/2006JE002821, 2007 Mars Odyssey Gamma Ray Spectrometer elemental abundances and apparent relative surface age: Implications for Martian crustal evolution Brian C. Hahn Department of Geosciences, State University of New York–Stony Brook, New York, USA Scott M. McLennan Department of Geosciences, State University of New York–Stony Brook, New York, USA G. Jeffrey Taylor Hawaii Institute of Geophysics and Planetology, Honolulu, Hawaii, USA William V. Boynton Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA James M. Dohm Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA Mike J. Finch Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA David K. Hamara Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA Daniel M. Janes Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA Suniti Karunatillake Department of Astronomy, Cornell University, Ithaca, New York, USA John M. Keller Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA Kristopher E. Kerry Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA Albert E. Metzger Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA Remo M. S. Williams Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA Abstract 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. Keywords: GRS; crustal evolution; surface age; Mars Odyssey; crust geochemistry. Index Terms: 5410 Planetary Sciences: Solid Surface Planets: Composition (1060, 3672); 5415 Planetary Sciences: Solid Surface Planets: Erosion and weathering; 5455 Planetary Sciences: Solid Surface Planets: Origin and evolution; 5464 Planetary Sciences: Solid Surface Planets: Remote sensing; 5470 Planetary Sciences: Solid Surface Planets: Surface materials and properties. Read Full Article (file size: 491110 bytes) Cited by Citation: Hahn, B. C., et al. (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. Copyright 2007 by the American Geophysical Union.

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