The instability of a south polar cap on Mars composed of carbon dioxide

If the martian south polar cap were composed of solid carbon dioxide, would it be sufficiently stable against collapse under its own weight? This question is examined in the light of new experiments on the creep of solid carbon dioxide and new high-resolution topographic mapping of the south polar cap. The conclusion from a simple model is that, with the strongest of three flow laws compatible with the measurements, CO2 is strong enough to support a cap of this material with thickness about 1800 m for 10(7) years or more, which is the age suggested by the cratering record. However, none of the three possible flow laws will allow a 3000-m cap, the thickness suggested by stereogrammetry, to survive for 10(7) years, indicating that the south polar ice cap is probably not composed of pure CO2 ice. (C) 2000 Academic Press.