Some Mars South Polar Swiss CheeseTerrain has Warm Walls

Much of the surface of the Mars south polar residual cap (SPRC) consists of quasi-circular depressions with steep walls that have been named "Swiss Cheese" terrain. High-resolution Mars Observer Camera (MOC) images have shown that the "Swiss Cheese" mesas, consisting of CO₂ ice, are retreating on the order of 1-4 meters per martian year. Many of these "Swiss Cheese" mesas are surrounded by dark moats that appear warm in mid summer Thermal Emission Imaging System (THEMIS) IR images. These warm moats are thought to be the exposed substrate of the underlying water ice rich polar layered deposits. In addition to the thermal signatures from the warm moats, THEMIS also detects a thermal signature from the walls of some of these mesas.

By combining THEMIS IR and VIS imaging, we are able to spectrally deconvolve warm and cold temperatures at a higher spatial resolution than the nominal THEMIS resolution of 100m/pix. We take into account that each THEMIS band has a slightly offset footprint from the other bands and assume that the thermal signature is coming from the darkest regions identified by the THEMIS VIS image. Preliminary analysis of one of these warm walled mesas suggests the wall consists of a low thermal inertia dust lag, which would have significant implications for the volatile content and evolution of the SPRC.