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Chemistry and mineralogy of outcrops at Meridiani Planum |
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| Authors: | B.C. Clark,R.V. Morris,R. Gellert,A.H. Knoll,T.K. Lowenstein,N.J. Tosca,P.R. Christensen,J. Brü ckner,G. Dreibus,G. Klingelhoefer,J. Zipfel,J. Grotzinger,R. Rieder |
| Affiliation: | a Lockheed Martin Space Systems, POB 179, MS S-8000, Denver, CO 80201, USA b NASA Johnson Space Center, Houston, TX 77058, USA c Dept. of Geosciences, State University of New York, Stony Brook, NY 11794, USA d Max Planck Institut für Chemie, Kosmochemie, Mainz, Germany e Dept. Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA f Botanical Museum, Harvard University, Cambridge MA 02138, USA g Dept. of Astronomy, Space Sciences Bldg. Cornell University, Ithaca, NY 14853, USA h Dept. Geol. Sci. and Environ. Studies, SUNY Binghamton, Binghamton, NY 13902, USA i Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA j Dept. of Geological Sciences, Arizona State University, Tempe, AZ 85287, USA k Honeybee Robotics, New York, NY 10012, USA l University of Nevada, Reno, Geol. Sci., Reno, NV 89557, USA m Space Science Institute, Boulder, CO 80301, USA n Johannes Gutenberg-University, Mainz, Germany o Massachusetts Inst. of Technology, Earth, Atmos. and Planetary Sci., Cambridge, MA 02139, USA p Dept. of Earth and Planetary Sciences, Univ. of Tennessee, Knoxville Tennessee 37996, USA |
| Abstract: | Analyses of outcrops created by the impact craters Endurance, Fram and Eagle reveal the broad lateral continuity of chemical sediments at the Meridiani Planum exploration site on Mars. Approximately ten mineralogical components are implied in these salt-rich silicic sediments, from measurements by instruments on the Opportunity rover. Compositional trends in an apparently intact vertical stratigraphic sequence at the Karatepe West ingress point at Endurance crater are consistent with non-uniform deposition or with subsequent migration of mobile salt components, dominated by sulfates of magnesium. Striking variations in Cl and enrichments of Br, combined with diversity in sulfate species, provide further evidence of episodes during which temperatures, pH, and water to rock ratios underwent significant change. To first order, the sedimentary sequence examined to date is consistent with a uniform reference composition, modified by movement of major sulfates upward and of minor chlorides downward. This reference composition has similarities to martian soils, supplemented by sulfate anion and the alteration products of mafic igneous minerals. Lesser cementation in lower stratigraphic units is reflected in decreased energies for grinding with the Rock Abrasion Tool. Survival of soluble salts in exposed outcrop is most easily explained by absence of episodes of liquid H2O in this region since the time of crater formation. |
| Keywords: | Mars outcrop Meridiani chemical sediment sulfate kieserite jarosite rover MER Opportunity |
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