¹Melissa D. Lane, ²Janice L. Bishop, ³M. Darby Dyar, ⁴Takahiro Hiroi, ⁵Stanley A. Mertzman, ⁶David L. Bish, ^7,8Penelope L. King, ⁹A. Deanne Rogers
¹Planetary Science Institute, 1700 E. Fort Lowell Road, Suite 106, Tucson, Arizona 85719, U.S.A.
²SETI Institute/NASA-Ames Research Center, Mountain View, California 94043, U.S.A.
³Mount Holyoke College, South Hadley, Massachusetts 01075, U.S.A.
⁴Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, U.S.A.
⁵Department of Earth and Environment, Franklin and Marshall College, Lancaster, Pennsylvania 17603, U.S.A.
⁶Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405, U.S.A.
⁷Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
⁸Department of Earth Sciences, University of Western Ontario, London, Ontario, N6A 3K7, Canada
⁹Department of Geosciences, State University of New York at Stony Brook, Stony Brook, New York 11790, U.S.A.

Sulfate minerals are important indicators for aqueous geochemical environments. The geology and mineralogy of Mars have been studied through the use of various remote-sensing techniques, including thermal (mid-infrared) emission and visible/near-infrared reflectance spectroscopies. Spectral analyses of spacecraft data (from orbital and landed missions) using these techniques have indicated the presence of sulfate minerals on Mars, including Fe-rich sulfates on the iron-rich planet. Each individual Fe-sulfate mineral can be used to constrain bulk chemistry and lends more information about the specific formational environment [e.g., Fe2+ sulfates are typically more water soluble than Fe3+ sulfates and their presence would imply a water-limited (and lower Eh) environment; Fe3+ sulfates form over a range of hydration levels and indicate further oxidation (biological or abiological) and increased acidification]. To enable better interpretation of past and future terrestrial or planetary data sets, with respect to the Fe-sulfates, we present a comprehensive collection of mid-infrared thermal emission (2000 to 220 cm−1; 5–45 μm) and visible/near-infrared (0.35–5 μm) spectra of 21 different ferrous- and ferric-iron sulfate minerals. Mid-infrared vibrational modes (for SO4, OH, H2O) are assigned to each thermal emissivity spectrum, and the electronic excitation and transfer bands and vibrational OH, H2O, and SO4 overtone and combination bands are assigned to the visible/near-infrared reflectance spectra. Presentation and characterization of these Fe-sulfate thermal emission and visible/near-infrared reflectance spectra will enable the specific chemical environments to be determined when individual Fe-sulfate minerals are identified.

Reference
Lane MD, Bishop JL, Dyar MD, Hiroi T, Mertzman SA, Bish DL, King PL, Rogers AD (2014) Mid-infrared emission spectroscopy and visible/near-infrared reflectance spectroscopy of Fe-sulfate Minerals. American Mineralogist 100, 66-82.
Link to Article [doi:10.2138/am-2015-4762]

Copyright: The Mineralogical Society of America