Response of Martian ground ice to orbit-induced climate change

Variations in the orbit and spin axis of Mars drive climate changes that affect both surface temperatures and atmospheric water content, both of which affect the distribution of ground ice. A simple technique is presented to determine the atmospheric water content for different epochs, on the basis of the water carrying capacity of the atmosphere over surface ice. Also presented is a technique to correct the water vapor density just above the surface for depletion due to nighttime frost, reducing the effective water vapor density in contact with ground ice. Distributions of stable ground ice are generated for the present epoch with varying amounts of water vapor in the atmosphere; water vapor depletion restricts the extent of stable ground ice and ice never becomes stable at low latitudes. As the position of perihelion varies, the extent of ground ice changes several degrees in latitudinal extent. The extent of ground ice is more sensitive to obliquity; however, high obliquities are still not able to make ground ice stable at low latitudes. The finding that ice is never stable at low latitudes is consistent with the absence of ice-related landforms, like terrain softening, at low latitudes. Correlations exist between the extents of stable ground ice and the distribution of various styles of mantle deposits.