CO 2 permafrost and Martian topography

Abstract

The role of CO 2 permafrost as an erosive agent on Mars is considered. In the CO 2H 2O system, with a CO 2 triple point at 217°K and 5.1-bar pressure, carbon dioxide solid, liquid, or gas, CO 2 clathrate, and ice are possible stable phases in the range of temperatures and pressures likely to be encountered in the Martian regolith. It is argued that conditions may exist in which CO 2 permafrost is extensive on Mars, provided that adequate CO 2 is available: the maximum ratio of H 2O:CO 2 required in the subsurface pore space system is 17:3. Erosional processes likely to result from such permafrost are block slumping, leading to canyon development; pit chains along faults; chaotic terrain where massive permafrost destruction has occured; large-scale flows of slurry; and perhaps even the flash floods which create channels.