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Compositional Investigation ofStratigraphic & Morphologic Unitsin the South Polar Ice Deposits of Mars
AdvisorCalvin, Wendy M
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Variable mixtures of CO2 ice, H2O ice, and dust in volatile exposures at the south pole of Mars influence interactions with the atmosphere that drive their formation, evolution, and eventual preservation as long-term climate records. However, ice composition in the south polar region has not been mapped in sufficient detail to fully track the influence of these dynamic processes and their implications for Mars climate history.This thesis is focused on expanding our understanding of south polar ice composition through a comprehensive analysis of data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Twenty-one spectral endmembers are identified and mapped at up to 18 m/pixel through k-means clustering and random forest classification of localized hyperspectral observations. Those endmembers are then mapped at 90 m/pixel across most of the CO2 ice-dominated south polar residual cap (SPRC) and key exposures of peripheral H2O ice. Evaluations of endmember spectra and associated spatial and temporal trends in classified maps are used to characterize compositional variation through time, across stratigraphic units, and within erosional morphologies. We report new findings that show complex topographic expressions and gradational transitions in the composition of H2O ice-rich deposits, which likely drive erosional processes and the formation of new climate records. Meanwhile, inter-annual variations in CO2 ice-dominated exposures demonstrate that large-scale dust events alter the deposition and retention of seasonal frost cover. Unexpectedly, residual ices outside of the SPRC are found to express CO2 ice signatures even after this seasonal cover is removed. The compositional framework revealed by these results have broad implications for continued research into the mechanisms that shape seasonal and residual ice deposits in this dynamic region.