Geologic Map of the MTM-85000 Quadrangle, Planum Australe Region of Mars

The area shown on this map includes layered polar deposits and residual polar ice, as well as some exposures of older terrain. Howard and others (1982) noted that an area (at lat 84.8 S., long 356 W.) near a 23-km diameter impact crater (Plaut and others, 1988) appears to have undergone recent deposition, as evidenced by the partial burial of secondary craters. Herkenhoff and Murray (1990a) mapped this area as a mixture of frost and defrosted ground and suggested that the presence of frost throughout the year stabilizes dust deposited in this area. This quadrangle was mapped using high-resolution Mariner 9 (table 1) and Viking Orbiter images in order to study the relations among erosional, cratering, and depositional processes on the polar layered deposits and to search for further evidence of recent deposition. Published geologic maps of the south polar region of Mars are based on images acquired by Mariner 9 (Condit and Soderblom, 1978; Scott and Carr, 1978) and the Viking Orbiters (Tanaka and Scott, 1987). The extent of the layered deposits mapped previously from Mariner 9 data is different from that mapped using Viking Orbiter images, and the present map agrees with the map by Tanaka and Scott (1987): the layered deposits extend to the northern boundary of the map area. However, the oldest unit in this area is mapped as undivided material (unit HNu) rather than the hilly unit in the plateau sequence (unit Nplh; Tanaka and Scott, 1987).