Exploring Martian polar atmospheric circulation and surface interactions

The northern and southern seasonal polar caps of Mars are formed in the polar night, during their respective autumn and winter seasons, by the condensation of atmospheric CO₂directly to the solid phase as ice, snow, and possibly frost. During spring and summer, the seasonal ice sublimes, returning CO₂ to the atmosphere. The caps advance and recede in response to seasonal variations in solar insolation, extending as far as 40° from the poles, and have been noted by telescopic observers since the 17th century Roughly 25% of the atmosphere, which is 95% CO₂ by volume, is cycled into and out of the seasonal caps. The CO₂ cycle dominates atmospheric circulation on Mars, and must be thoroughly understood in order to answer fundamental questions about climate history and the global distribution of near‐surface water.