The solid-state greenhouse effect: a model for dark Albedofeatures in the Martian polar regions

Abstract: From a morphological and spectral study of dark albedo features in theMartian polar regions, a hypothesis is made that dark dune spots on Marscould indicate seepage flow of liquid water. In order to evaluate thishypothesis, the dark dune spots are studied both with regard for theirseasonal time of appearance and composition. Using imagery from the HiRISEand CRISM instruments on the Mars Reconnaissance Orbiter, it is found thatdark dune spots appear while CO2 ice still covers the surface. In order toaccount for this in the liquid water hypothesis, two theoretical models areconstructed. One model is for the solid-state greenhouse effect in carbondioxide ice and water-based snow packs. The other is for the solar radiationintensity on the Martian surface as a function of latitude and solarlongitude. Additionally, an experiment is performed with the purpose ofinvestigating the solid-state greenhouse effect in a Martian semi-analogousenvironment. From modeled results, it is found that sufficiently opticallythin H2O snow/frost packs with low thermal conductance may allow salty liquidwater even when the surface is encrusted with a layer of CO2 ice. Also, theappearance of particle sprays in the experiment may indicate the origin andnature of the bright halos and fans that sometimes appear in conjunction withdark dune spots and geysers. These would be deposited CO2 or H2O frost, thathas been sprayed from the dark dune spots and geysers.