The geology of this region was to be explored by the failed NASA mission Mars Polar Lander, which lost contact on entry into the Martian atmosphere.

[1][2][3][4] Planum Australe is partially covered by a permanent polar ice cap composed of frozen water and carbon dioxide about 3 km thick.

[9][10][11] In 1966, Leighton and Murray proposed that the Martian polar caps provided a store of CO2 much larger than the atmospheric reservoir.

[17] Then, sublimed CO2 (and probably water) increase pressure in their interior, producing geyser-like eruptions of cold fluids often mixed with dark basaltic sand or mud.

[18][19][20][21] This process is rapid, observed happening in the space of a few days, weeks or months, a growth rate rather unusual in geology – especially for Mars.

[22][23] In September 2020, scientists confirmed the existence of several large saltwater lakes under the ice in the south polar region of the planet Mars.