The South Pole of Mars is characterized by an asymmetric residual ice cap composed of water ice and CO2 ice. On the opposite side of the residual cap, there exists an area called cryptic region which is relatively free of ice during summer time. Many fan-shaped km-scale structures apparently caused by a wind-blown system of dust-laden gas jets occurred dozens degrees of Ls before the complete sublimation of the CO2 frost layer. We have examined the seasonal cycles of condensation and sublimation in the cryptic and non-cryptic regions by using the topographic data from the MOLA/MGS measurements. Using the MOLA topography data collected over one Martian year (1999-2001), we have studied the temporal elevation change and the seasonal cycle of the carbon dioxide frost on the southern polar caps. We have produced mapping of the seasonal CO, frost thickness variation for seven Ls (30 degrees, 60 degrees, 90 degrees, 120 degrees, 150 degrees, 180 degrees, 210 degrees, 240 degrees, 270 degrees and 330 degrees). It is found that the time variations of the CO2 frost thickness in these two regions are quite similar. The greatest thickness of the CO2 frost layer is about 0.76-0.78 in in both places occurs at Ls = 150 degrees. (C) 2008 COSPAR. Published by Elsevier Ltd. All rights reserved.
