Mathematics – Logic
Scientific paper
Oct 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009phdt........81k&link_type=abstract
ProQuest Dissertations And Theses; Thesis (Ph.D.)--Arizona State University, 2009.; Publication Number: AAT3361847; ISBN: 978110
Mathematics
Logic
Scientific paper
The distribution and nature of minerals on the Martian surface provide essential information about the planet's geological history, including the history of water. The interaction of water with the rocky materials of the planet formed new minerals that hold clues about water's history on Mars. But those same interactions of aqueous alteration and chemical weathering also complicate spectroscopic measurements: the means by which mineralogy is investigated. It is necessary to study the how chemical weathering affects spectral measurements so that the observations, and ultimately the mineralogy and aqueous history of Mars, may be better understood. Altered basalts were studied in the laboratory in order to better understand how alteration affects spectral measurements and their interpretation. Alteration causes significant changes to basalt spectra in the mid-infrared (IR). The spectra change because alteration minerals or mineraloids that form when silicate minerals breakdown in water are silica-rich, and the mineralogical redistribution of silica is strongly detectable in the mid-IR. Furthermore, the new materials form thin coatings on the original minerals in the rock that hide portions of the rock from spectral detection, which complicates modeling techniques traditionally used to analyze those data. While weathering rinds and coatings are strongly detected in the mid-IR, they are largely undetected in the near-IR, where spectral signatures expected from the hydrous weathering products cannot be seen because of the coatings configuration. Spectroscopic observations of Mars indicate regions of high-silica materials, but those same regions are devoid of near-IR hydration features. Although these observations have been interpreted as a lack of aqueous alteration, they are consistent with the laboratory investigations of chemically altered rocks. The distribution of high-silica materials on Mars is correlated with the distribution of geologically recently periglacial features. The formation model suggested here is that high-silica regions of Mars resulted from weathering of basaltic materials in icy soil environments where high-silica materials formed thin coatings on basaltic particles and rocks. Weathering likely has been an ongoing process on Mars, and there may have been enough liquid water in the near-surface environment to drive weathering reactions throughout much of Martian history.
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