Annual Heat Balance of Martian Polar Caps: Viking Observations

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Abstract
The Infrared Thermal Mappers aboard the two Viking orbiters obtained solar reflectance and infrared emission measurements of the Martian north and south polar regions during an entire Mars year. The observations were used to determine annual radiation budgets, infer annual carbon dioxide frost budgets, and constrain spring season surface and atmospheric properties with the aid of a polar radiative model. The results provide further confirmation of the presence of permanent CO2frost deposits near the south pole and show that the stability of these deposits can be explained by their high reflectivities. In the north, the observed absence of solid CO2 during summer was primarily the result of enhanced CO2 sublimation rates due to lower frost reflectivities during spring. The results suggest that the present asymmetric behavior of CO2frost at the Martian poles is caused by preferential contamination of the north seasonal polar cap by atmospheric dust.