Characteristics of the Basal Interface of the Martian South Polar Layered Deposits

We expand on previous studies of the South Polar Layered Deposits' (SPLD) basal interface using data acquired by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) to obtain detailed maps of elevation, topography, and reflected radar power. Using these maps, we derive the thickness (ranging from 0 to 3.7 km) and volume of the SPLD (similar to 1.60 x 10(6) km(3)). While most basal interfaces reflect less power than the average SPLD surface, areas with basal echo power exceeding that of the surface are widespread throughout the SPLD, including at the location of potential subglacial water bodies in Ultimi Scopuli. The occurrence of these high basal echo power signatures appears to be largely frequency independent in MARSIS data. While the cause of the relatively high basal echo power values is uncertain, our observations suggest that this behavior is widespread, and not unique to Ultimi Scopuli.