The Penetration of Solar Radiation into Granular Carbon Dioxide and Water Ices of Varying Grain Sizes on Mars

The penetration depth of broad spectrum solar irradiation over the wavelength range 300-1,100 nm has been experimentally measured for water and carbon dioxide ices of different grain size ranges. Both of these ice compositions are found on the surface of Mars and have been observed as surface frosts, snow deposits, and ice sheets. The e-folding scale of snow and slab ice has been previously measured, but understanding the behavior between these end-member states is important for modeling the thermal behavior and surface processes associated with ice deposits on Mars, such as grain growth and slab formation via sintering, and carbon dioxide jetting leading to the formation of araneiforms. We find the penetration depth increases in a predictable way with grain size, and an empirical model is given to fit these data, varying with both ice composition and grain size.