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Characterization of the Effects of Precursor Mineralogy on Hematite Spectra: Application to Martian Hematite MineralizationThe Thermal Emission Spectrometer (TES) instrument aboard Mars Global Surveyor discovered several isolated deposits of gray, crystalline hematite in Sinus Meridiani, Aram Chaos, and Valles Marineris. A variety of formation mechanisms has been proposed for the martian hematite deposits, including aqueous and nonaqueous processes. Comparison of the average Sinus Meridiani hematite spectrum measured by TES to laboratory emissivity spectra for a variety of naturally occurring hematites shows small but potentially important differences. In particular, the emissivity minimum at 300 and 445/cm in the Sinus Meridiani (SM) spectrum is displaced 10-25/cm to lower frequencies compared to some natural hematite samples. In addition, these bands in the TES data are narrower than the broad bands seen in many natural hematite spectra. These differences may imply that the natural variability of hematite spectra has not been fully characterized, especially with respect to the reaction pathway (precursor mineralogy and temperature of hematite formation) and crystal morphology. Here, we describe the thermal infrared spectral characteristics of several series of synthetic hematite samples derived by direct precipitation, dehydroxylation of fine-grained goethite and the oxidation of magnetite. Several natural hematite sample spectra are also presented for comparison. Transmission electron microscopy (TEM) and Mossbauer spectral analyses of selected samples were performed in order to help determine the causes of the changes seen in the infrared spectra.
Document ID
20030111353
Document Type
Conference Paper
Authors
Glotch, Timothy D. (Arizona State Univ. Tempe, AZ, United States)
Morris, Richard V. (NASA Johnson Space Center Houston, TX, United States)
Sharp, Thomas G. (Arizona State Univ. Tempe, AZ, United States)
Christensen, Philip R. (Arizona State Univ. Tempe, AZ, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Publication Information
Publication: Lunar and Planetary Science XXXIV
Subject Category
Lunar and Planetary Science and Exploration
Distribution Limits
Public
Copyright
Public Use Permitted.

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