Spatial and Temporal Variation of Mars South Polar Ice Composition from
Spectral Endmember Classification of CRISM Mapping Data
Abstract
Multispectral mapping data from the Compact Reconnaissance Imaging
Spectrometer for Mars (CRISM) provide a unique opportunity to
characterize south polar ice deposits at higher spectral sampling,
spatial resolution, or spatiotemporal coverage than previous work. This
new perspective can help to constrain the nature and distribution of
different mixtures of CO2 ice, H2O ice, and dust that influence the
formation, evolution, and preservation of Mars climate records. We
processed 1103 CRISM observations spanning southern summer of six Mars
Years (MY) through a combination of k-means clustering and random forest
classification. Using a set of 12 spectral endmembers directly tied to
previous work with high-resolution CRISM targeted data, we made a series
of temporally restricted mosaics showing surface spectral variation over
time. The mosaics show the effects of the MY 28 dust storm on the
removal of the seasonal CO2 ice cap that year and new details of how
this process differed from the years that followed. A mosaic showing
residual ice surfaces displays broad agreement with previous
compositional maps while resolving new details in the distribution of
H2O ice-rich material around the periphery of the bright CO2 ice cap. By
showing how surface composition varies across a broad swath of the south
polar region though time, the endmember set and classified mosaics
produced in this work can provide critical context for future studies of
the dynamic processes that shape south polar ice deposits.