Martian glaciation and the flow of solid CO2

Results are discussed for a series of laboratory deformation experiments that were conducted to determine a flow law for solid CO2 so that a physical basis could be established for considering the possibility of CO2 glaciation in the Martian polar regions. The experimentally determined flow law indicates that (1) the concept of CO2 glacial flow at the Martian poles is not physically unrealistic, (2) the strength of CO2 near its sublimation point is considerably less than the strength of water ice near its melting point, and (3) CO2 is likely to flow over a broad range of temperatures below its melting point. A glacial model for the Martian polar caps is suggested in which CO2-rich layers deposited near the poles flowed outward laterally to relieve high internal shear stresses. It is shown that this model can explain the topography of the polar caps, the uniform layering of the layered deposits, and the general extent of the polar 'sediments'. Some problematic assumptions of the model are noted, including the large amounts of CO2 necessary to move the layered deposits and the need to increase vapor pressure and temperature with depth in the deposits.