HR: 1340h
AN: P43A-0897    [Abstracts]
TI: Analysis of "Meridiani Planum"-like evaporites using CheMin, an XRD/XRF instrument proposed for the Mars Science Laboratory (MSL)
AU: * Blake, D F
EM: dblake@mail.arc.nasa.gov
AF: NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035 United States
AU: Sarrazin, P
EM: psarrazin@inxitu.com
AF: InXitu, PO Box 730, Mountain View, CA 94042 United States
AU: Feldman, S
EM: sfeldman@mail.arc.nasa.gov
AF: NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035 United States
AU: Vaniman, D
EM: vaniman@lanl.gov
AF: Los Alamos National Laboratory, P.O. Box 1663, Mail Stop D-462, Los Alamos, NM 87545 United States
AU: Chipera, S
EM: chipera@lanl.gov
AF: Los Alamos National Laboratory, P.O. Box 1663, Mail Stop D-462, Los Alamos, NM 87545 United States
AU: Bish, D
EM: bish@indiana.edu
AF: Indiana University, 1001 E. 10th St., Bloomington, IN 47405 United States
AB: The discovery of up to 30-40 wt% sulfate salts in sediments at Meridiani Planum [1-2] indicates that evaporite sediments have played an important role in the hydrogeologic history of Mars. Data available to date support the presence of the mineral jarosite (a hydrous Fe-sulfate), Mg-sulfate, and lesser amounts of salts containing Cl and Br. One of the most exciting features of the Meridiani sediments is the possibility that the salts may be hydrated. Water storage in minerals may be a significant source of the elevated hydrogen abundances seen in some equatorial regions by the Odyssey spacecraft, with abundances up to 8-9 wt% water-equivalent present in areas where water ice should not be stable [3]. Is it possible that salt hydrates in evaporite sediments can account for some of this equatorial water? The ability to quantify mixed-salt mineralogies will be important for determining brine history on Mars. Definitive mineralogy, a key requirement of MSL, can be accomplished by the CheMin X-ray Diffraction / X-ray Fluorescence (XRD/XRF) instrument [4]. The MSL approach to investigating this kind of deposit can be based on the capabilities demonstrated by MER-B (visual petrography, Mossbauer, APXS, and Mini-TES). The enhanced drilling capability of MSL can be used to collect and transfer cores to the rock crusher for pulverizing and ultimate delivery of crushed material to CheMin. If MSL is able to traverse kilometers or tens of kilometers, CheMin characterization of changes in evaporite mineralogy, zonation in evaporite facies or the mineralogical identity of detrital grains could be used to conduct an analysis of the evaporative basin - lateral extent, water depth, salinity, facies changes, etc. The ability to quantify hydrated mineral assemblages will be important for reconstructing brine evolution and for determining the nature of interactions between brine minerals and detrital mineralogy. The important contribution of CheMin to a site like Meridiani will be to provide accurate and definitive mineralogical data of complex multi-mineral mixtures. Definitive mineralogical data will be highly useful in interpreting brine chemistry and the nature and extent of the ancient habitable zone that existed there. [1]. MER Rover web site (http://www.jpl.nasa.gov/mer2004/rover-images/mar-02-2004/images-3-2-04.html [2]. Kerr, R. A. (2004), "A wet early Mars seen in salty deposits," Science 303, 1450. [3]. Feldman, W. C., et al. (2003), "The global distribution of near-surface hydrogen on Mars," In: Sixth Int. Conf. on Mars, abstract #3218, Lunar and Planetary Institute, Houston (CD-ROM). [4]. Blake, D.F., P. Sarrazin, D.L. Bish, S. Feldman, S.J. Chipera, D.T. Vaniman, and S.A. Collins (2004), "Definitive Mineralogical Analysis of Mars Analogs Using the CheMin XRD/XRF Instrument," Lunar and Planetary Science Conf XXXV, abstr. #1373 (CD-ROM).
DE: 3625 Descriptive mineralogy
DE: 3694 Instruments and techniques
DE: 1060 Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
DE: 1094 Instruments and techniques
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting