 Kieffer (2000) suggests no significant amount of clathrates could exist near the surface of Mars.Stewart & Nimmo (2002) find it is extremely unlikely that CO2 clathrate is present in the Martian regolith in quantities that would affect surface modification processes.They argue that long term storage of CO2 hydrate in the crust, hypothetically formed in an ancient warmer climate, is limited by the removal rates in the present climate.