South Residual CAP of Mars: Many Units, Many Processes

The upper units of Mars' Residual South Polar Cap (RSPC) composed essentially of CO2 ice display multiple types of deposits and several types of ongoing erosional modification. Images from Mars Reconnaissance Orbiter Context Camera (CTX) now cover three southern summer seasons, and provide essentially complete geographic coverage of both morphologic and photometric changes at the 6 m/pixel scale. The 2011 (MY 30) data compared to MY28 data show the asymmetric opening of some types of depressions, such as the "finger print terrain", uniform expansion of many depressions, and near stability of some unit boundaries. The change and morphologic data are used to model the varying sequence of deposition and erosion in the residual cap's 100+ Mars Year record. The different depositional units may reflect varying porosities, changes in net annual accumulation, or different amounts of included non-volatile materials. Variations in dust loading are the most likely driver of much of the changes in the character and rate of activity in the residual cap region.