A search for basaltic-to-intermediate glasses on Mars: Assessing martian crustal mineralogy |
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| Authors: | Michelle E Minitti Victoria E Hamilton |
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| Institution: | a Center for Meteorite Studies, School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404, United States
b Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, United States |
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| Abstract: | Multiple datasets have demonstrated that the crust of Mars is fundamentally basaltic. However, spectral libraries used to interrogate thermal infrared spectra of Martian dark regions through spectral deconvolution have heretofore lacked mafic glasses despite the importance of amorphous phases (or phases with amorphous-like spectral signatures) in Martian mineralogy. To establish the presence and importance of basaltic-to-intermediate glasses in Martian lithologies, we created five such glasses, obtained their thermal infrared spectra and included the spectra in a library used to deconvolve nine regional Thermal Emission Spectrometer spectra from Mars. We employed the nonnegative least squares (NNLS) deconvolution method, which yields deconvolved phase abundances and the uncertainties associated with those abundances. The basaltic-to-intermediate glasses do not appear in the deconvolution solutions, indicating they are not globally or regionally important phases. Because Martian igneous or impact processes are capable of basaltic-to-intermediate glass formation, the lack of such glasses in the deconvolved mineralogies suggests either the glasses did not form in detectable quantities or they (or their signatures) have been removed. The masking or replacement of basaltic-to-intermediate glasses through alteration is supported by the appearance in the deconvolution solutions of amorphous phases (e.g., silica-rich glasses, opal) or phases with amorphous-like spectral signatures (e.g., clays, zeolites) that commonly form through aqueous alteration of mafic glasses. The glasses may still be important to local-scale thermal infrared studies given the basaltic nature of Mars and the variety of local-scale lithologies detected by various missions. The regional mineralogies derived from the NNLS deconvolution analysis divide into five statistically separable groups, which provide insight into regional trends in mineralogy. |
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| Keywords: | Mars Mars Surface Mineralogy Spectroscopy |
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