Sublimation Kinetics of Co2 Ice and Evolution of the Martian Polar Caps

Introduction: The martian polar caps are in majority composed of CO2 ice [1-3]. Early modeling of the polar caps suggested that they were in equilibrium with the ~6 mbar CO2 atmosphere [2], and various observations have shown a ciclicity of growth and retreat, following martian seasons [4]. However, other studies show that CO2 ice constitutes only a thin veneer on the surface of a probably much thicker ice layer [5]. This veneer is too small for the caps to be in equilibrium with the atmosphere [6,7]. This would also suggest that the polar caps are very young [8]. Therefore, there must be a much larger unidentified CO2 reservoir in the martian subsurface, possibly adsorbed CO2 in the regolith [9,10], to buffer the much larger atmosphere, or it means the total budget of CO2 is present in the atmosphere, and that Mars has today much less CO2 than other telluric planets.