THE HEMISPHERICAL ASYMMETRY IN THE MARTIAN POLAR CAPS

An energy balance model is used to study the behavior of CO2 ice on Ma rs. The effect of the solar zenith angle dependence of albedo is Lo le ngthen CO2 ice lifetimes at the poles. Hemispherical asymmetries in cl oud and dust abundance could result in the survival of seasonal CO2 ic e through summer in the south and not in the north, in agreement with observations. CO2 ice observed in the summertime polar cap in the sout h could be of recent origin, although a permanent CO2 polar cap cannot be ruled out.