HR: 0800h
AN: P21A-0126    [Abstracts]
TI: Distinguishing Na, K, and H3O+ Jarosite and Alunite on Mars using VNIR, Emittance and M”ssbauer Spectroscopy on the MER and Mars Express/OMEGA Missions
AU: * Bishop, J L
EM: jbishop@arc.nasa.gov
AF: SETI Institute & NASA-Ames Research Center, 515 N. Whisman Rd, Mountain View, CA 94560
AU: Rothstein, Y
P21A-0126 AF: Mount Holyoke College, 50 College St., South Hadley, MA 01075
AU: Dyar, M D
P21A-0126 AF: Mount Holyoke College, 50 College St., South Hadley, MA 01075
AU: Lane, M D
P21A-0126 AF: Planetary Science Institute, 620 North Sixth Avenue, Tucson, AZ 85705
AU: Klima, R L
P21A-0126 AF: Brown University, Department of Geological Sciences, Providence, RI 02912
AU: Brophy, G P
P21A-0126 AF: Amherst College, Department of Geology, Amherst, MA 01002
AB: Jarosite has been identified in layered outcrops in Meridiani by the MER Mossbauer spectrometer [Klingelh”fer, et al., 2004] and may be present elsewhere on Mars. We are studying VNIR, emittance and M”ssbauer spectroscopy of a suite of synthetic and natural samples of jarosite and alunite from the Brophy collection [e.g. Brophy and Sheridan, 1965]. The characteristic NIR overtones and combination bands in this group differ not only depending on the trivalent cation (e.g. Al for alunite and Fe for jarosite), but also depending on the type of monovalent cation (typically K, Na and/or H3O). The VNIR spectrum of K-jarosite exhibits an OH stretching band at 1.47 um, an OH stretch + 2 bend combination doublet at 1.849 and 1.864 um, plus an OH stretch + bend combination triplet at 2.215, 2.265, and 2.300 um and additional OH and SO4 combination features near 2.40, 2.46, 2.50, 2.60 and 2.62 um. H3O- and Na-jarosite spectra exhibit broader features and the doublet is less resolvable. The spectrum of Na-jarosite contains a band at 1.48 um, a broad asymmetric band near 1.85 um and a triplet near 2.235, 2.275, and 2.310 um, plus additional features near 2.42, 2.47, 2.52, 2.62 and 2.64 um. Band assignments for jarosite and alunite spectra are from Bishop and Murad [2005]. We are in the process of comparing these spectra with the mid-IR and Mossbauer spectra of this jarosite group sample suite in order to perform coordinated analyses for this sulfate group on Mars using the MER and Mars Express datasets. References: Bishop, J. L., and E. Murad (2005), The visible and infrared spectral properties of jarosite and alunite, Am. Miner., 90, 1100-1107. Brophy, G. P., and M. F. Sheridan (1965), Sulfate studies IV: The jarosite-natrojarosite-hydronium jarosite solid solution series, Am. Miner., 50, 1595-1607. Klingelh”fer, G., et al. (2004), Jarosite and hematite at Meridiani Planum from Opportunity's M”ssbauer spectrometer, Science, 306, 1740-1745.
DE: 3929 NMR, Mossbauer spectroscopy, and other magnetic techniques
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 5464 Remote sensing
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: Fall Meeting 2005