HR: 0800h
AN: P21A-0217    [Abstracts]
TI: Hydrated Iron Sulfate Minerals by FT-IR, ESEM and XRD: Effects of Hydration, Metal Ions, and Oxidative State
AU: * Mielke, R
EM: Randall.E.Mielke@jpl.nasa.gov
AF: Jet Propusion Laboratory, Caltech, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Blaney, D
EM: Diana.L.Blaney@jpl.nasa.gov
AF: Jet Propusion Laboratory, Caltech, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Nordstrom, K
EM: dkn@usgs.gov
AF: U.S. Geological Survey, Boulder, 3215 Marine St., Suite E127, Boulder, CO 80303, United States
AU: Aplers, C
EM: cnalpers@usgs.gov
AF: U.S. Geological Survey, WRD, 3020 State University Drive East, Sacramento, CA 95819, United States
AU: Coleman, M
EM: Max.Coleman@jpl.nasa.gov
AF: Jet Propusion Laboratory, Caltech, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AB: Data from the Mars Exploration Rovers (MER) and orbital remote sensing have determined that iron-bearing sulfates and iron-sulfates account for much of the mineralogical variation on Martian chemical sediments. We have begun a comprehensive study to evaluate a suite of hydrated iron sulfate minerals at different levels of oxidation or mineral phases using micro-FT-IR, ESEM and XRD. Selected minerals include jarosite, copiapite, coquimbite, halotrichite, kornelite, melanterite, rhomboclase, roemerite, rozenite, and szomolnokite. The structure and wavelength of the water bands are controlled by the immediate proximity of the water molecules to the Fe3+ and Fe2+ cores. Iron and aluminum change the fundamental vibration amplitudes and shift the energy requirement for a specific bond vibration. The original mineral spectral signature can be present even after oxidative products form on the iron sulfate surfaces and basic spectral lines can be analyzed. When mineral samples were sectioned and analysis performed on the interior mineral surfaces, the spectra showed the predominant spectral lines under both conditions with most variations occurring in peak definition. ESEM-EDAX and XRD analysis confirmed the presence of oxidative products on the mineral surfaces even when the mineral samples were stored in anoxic conditions (under mineral oil) and refrigerated in airtight containers after sampling. Spectral variability between 30 micron spots within 200x200 micron areas showed minimal compositional / spectral variability. The micro-spectroscopic approach permits the study of complex iron sulfate mineral structures (e.g. evaporite sequences, crystal formations) to determine the hydration, metal ion, and oxidative state in terrestrial analog systems and on future Mars missions, without destruction of the sample.
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
DE: 3994 Instruments and techniques
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting