HR: 11:20h
AN: P32A-05 INVITED     [Abstracts]
TI: The Spirit Rover at Gusev Crater
AU: * Yen, A
EM: Albert.Yen@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, MS 183-501, Pasadena, CA 91109, United States
AU: Science Team, A
EM: squyres@astro.cornell.edu
AF: Cornell University, Department of Astronomy, Ithaca, NY 14853, United States
AB: The Spirit rover has traversed approximately 7 km in 1100 sols of operations at the Gusev Crater landing site. Highlights relevant to the goal of understanding the role of liquid water at the martian surface include the following: (1) The discovery of ferric sulfates, likely hydrated, in deposits which have the unmistakable chemical signatures of nearby rocks. The movement of low pH hydrothermal fluids and/or vapors through local rocks prior to precipitation of these materials is consistent with the observations. (2) Goethite (alpha-FeOOH), a mineral phase which requires water to form, represents ~20% to 35% of the iron in numerous rock samples (Clovis Class) on the West Spur of the Columbia Hills. Aqueous alteration is clearly indicated by this presence of goethite. (3) Nearly isochemical signatures were found in elemental analyses of over ten distinct samples (Wishstone/Watchtower class rocks), but the ratio of ferric iron to total iron varied from ~0.4 to 0.95. Small quantities of water, insufficient to flush cations from the samples, were likely responsible for this weathering. (4) Also relevant to the characterizing the role of liquid water is the discovery of an ultramafic sequence of rocks where over 70% of the iron is in unaltered olivine and the ferric to total iron ratio is ~0.1. This result indicates that certain materials at the martian surface have been protected from aqueous alteration.
DE: 1000 GEOCHEMISTRY
DE: 1027 Composition of the planets
DE: 5400 PLANETARY SCIENCES: SOLID SURFACE PLANETS
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Joint Assembly