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

Abstract

Vast quantities 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 CO2 ice is 1–2 orders of magnitude weaker than water ice under Martian polar conditions. Here we present data from deformation experiments on pure, fine‐grained CO2 ice, over a broader range of temperatures than previously explored (158–213 K). The experiments confirm previous observations of highly nonlinear 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 deposits are modestly stronger than previously thought. Nevertheless, CO2 ice flows much more readily than H2O ice, particularly on the steep flanks of SPLD topographic basins, allowing the CO2 to pond as observed.