Density, Depth, and Distribution of seasonal CO2 deposition on Mars

Recent observations of the polar cap mass changes by the Neutron Detector on board Mars Odyssey combined with observations of volume change from the Mars Orbiter Laser Altimeter on board Mars Global Surveyor allow estimates of the density of the seasonal deposits. The resulting density is about 0.6 gm/cm³, and while it is somewhat lower than previous estimates based on gravity and high-energy neutrons, we do not regard the various estimates as inconsistent since the error budgets are large. The derived density is about one third that of solid CO₂ ice, implying significant pore space in the deposits. Decomposition of the MOLA height changes demonstrates a spatial heterogeneity in frost/snow thickness, that in some cases, correlates with local geologic setting.