Georgia Journal of Science


This review summarizes mostly Earth-based observations of Mars’ south polar region (SPR) made since the late 17th century along with measurements of the 2003, 2005, and 2018 south polar cap (SPC). There are four conclusions. The first one is the SPC has not underwent radius changes exceeding 3 % and 10 % for Ls < 230° and Ls = 230°–270°, respectively, in at least the last 125 years. Secondly, t test results are consistent with the SPC being larger when on the morning terminator than on the afternoon terminator. Thirdly, the dark area Depressio Magna drawn by Antoniadi (1975) and the “cryptic terrain” described by Kieffer et al. (2000) are probably the same feature. Fourthly, isolated clouds, away from the disk edges and terminators, are scarce in the SPR during Ls = 180°–330°.


ACKNOWLEDGEMENTS The writer would like to thank the individual at the 2018-GRAM meeting who suggested a large dust storm deposited dust, which is a possible cause of the Cryptic Terrain.