The rheological behavior of CO2 ice: application to glacial flow on Mars

Vast amounts of solid CO2 reside in topographic basins of the south polar layered deposits (SPLD) on Mars and exhibit morphological features indicative of glacial flow. Previous experimental studies showed that coarse-grained CO2 ice is 1–2 orders of magnitude weaker than water ice under Martian polar conditions. Here we present data from a series of deformation experiments on high-purity, fine-grained CO2 ice over a broader range of temperatures than previously explored (158–213 K). The experiments confirm previous observations of highly non-linear power-law creep at larger stresses, but also show a transition to a previously-unseen linear-viscous creep regime at lower stresses. We examine the viscosity of CO2 within the SPLD and predict that the CO2-rich layers may be stronger than previously thought. We also predict that CO2 ice flows much more readily than H2O ice on steep flanks of SPLD topographic basins, allowing the CO2 to pond as observed.