HR: 14:55h
AN: P12C-06 INVITED     [PDF]
TI: Chemistry of the Martian Soils and Rocks at the Pathfinder Landing Site as Determined by the APXS.
AU: * Foley, C
EM: nfoley@fieldmuseum.org
AF: Isotope Geochemistry Laboratory, Department of Geology, The Field Museum, 1400 S. Lake Shore Dr., Chicago, IL 60605 United States
AU: Economou, T E
EM: tecon@tecon.uchicago.edu
AF: Laboratory for Astrophysics and Space Research, University of Chicago, 933 East 56th Street, Chicago, IL 60637 United States
AU: Clayton, R N
EM: r-clayton@uchicago.edu
AF: Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 United States
AB: The chemical compositions of Martian rocks and soils examined with the Alpha Proton X-ray Spectrometer (APXS) during the Mars Pathfinder 1997 lander mission were not previously fully determined. Preliminary chemical results included major element abundances determined by the incomplete calibration of the X-ray mode. The data collected from the alpha and proton detectors were not previously analyzed due to significant atmospheric contributions to the spectra. The back-up instrument of the Pathfinder Alpha Proton X-ray Spectrometer flight instrument has been used to complete the instrument calibration under simulated Martian conditions at the University of Chicago. The calibrated Pathfinder APXS instrument is capable of measuring concentrations of all major and minor rock-forming elements ranging from carbon through zirconium in atomic number. Therefore, it is capable of constraining the petrology of the measured samples. Final Pathfinder soil and rock sample abundances from the alpha, proton, and X-ray modes have been quantified. The abundances suggest that: 1.) the rocks are covered with various amounts of soil; 2.) the soil-free rocks, on a volatile-free basis, have some element ratios similar to Mars meteorites, yet have different bulk chemistry indicative of more evolved rocks with higher silica abundances; 3.) the carbon and nitrogen contents are below detection limits; and 4.) the alpha mode oxygen reveals excess amounts of oxygen in some samples which is indicative of sample-bound water (contained within minerals or glasses in samples). The presence of some water, up to 4 wt%, in some Pathfinder rocks implies that they may have been altered by some non-igneous process.
DE: 1020 Composition of the crust
DE: 1060 Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
DE: 3655 Major element composition
DE: 5464 Remote sensing
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting