Liquid carbon dioxide and the Martian polar laminae

One of the most important findings of the Mariner 9 mission was the existence of a set of apparent stacked layers in both the north and south polar regions of Mars. The total thickness of the laminated terrain is approximately several kilometers. Because the Martian atmosphere is composed largely of CO2 and because the frost point of CO2 is known to be reached in both polar regions, it has been assumed that the volatiles in the bright laminae are in appreciable part condensed CO2, although condensed H2O, and a CO2-H2O clathrate are also possible. As long as the ratio of CO2 to H2O is large, the physical properties will be dominated by the CO2.