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The solar and thermal flux striking the polar cap of Mars is computed for various ozone, dust, and cloud abundances and for three solar zenith angles. Ozone does not significantly affect the total energy budget of the polar cap. Hence the observed hemispherical asymmetry in ozone abundance causes only an insignificant hemispherical asymmetry in the polar caps. Vertical optical depths of dust and cloud ranging from zero to 1 cause little change in the total flux absorbed by the polar cap near its edge but increase the absorbed flux significantly as one travels poleward. Hemispherical asymmetries in dust abundance, cloud cover, and surface pressure combine to cause a significant hemispherical asymmetry in the total flux absorbed by the residual polar caps, which helps to explain the dichotomy in the residual polar caps on Mars. Other processes which affect the energy budget of the polar cap are proposed and reviewed, particularly with respect to their interaction with the radiative effects of clouds and dust.

During periods of low obliquity, The existence of permanent CO 2 polar caps in previous work has shown that martian CO 2 partial both hemispheres will act as a cold trap for pressures decreased to 0.1 mbar; CO 2 partial water vapor [Ingersoll, 1974; Toon et al., 1980; pressures decreased to 0.02 mbar prior to the Pollack and Toon, 1982]. The general circulation formation of the Tharsis bulge. The permanent patterns, strongly controlled by the seasonal polar caps act as a cold trap and projected glob-sublimation and condensation of CO 2 onto the al average water vapor abundances drop to possib-polar caps, would have transported water vapor ly as low as 10 -5 precipitable •m. As a result, from all locations on the planet to polar the odd hydrogen catalytic cycle would not be latitudes, where it would have frozen out and effective at recombining CO and O back into CO•, remained frozen. The polar cold traps would be and as much as 0.12 mbar of CO and 0.06 mbar •f very efficient, and the entire martian atmosphere OA could exist. These increased abundances would would dry out. As a result, adsorbed water in