HiRISE observations of new impact craters exposing Martian ground ice
Article first published online: 27 JAN 2014
©2013. American Geophysical Union. All Rights Reserved.
Journal of Geophysical Research: Planets
Volume 119, Issue 1, pages 109–127, January 2014
How to Cite
2014), HiRISE observations of new impact craters exposing Martian ground ice, J. Geophys. Res. Planets, 119, 109–127, doi:10.1002/2013JE004482., , , , , , and (
- Issue published online: 28 FEB 2014
- Article first published online: 27 JAN 2014
- Accepted manuscript online: 23 DEC 2013 01:48AM EST
- Manuscript Accepted: 18 DEC 2013
- Manuscript Revised: 25 NOV 2013
- Manuscript Received: 8 JUL 2013
- Impact Craters;
- Ground Ice
Twenty small new impact craters or clusters have been observed to excavate bright material inferred to be ice at mid-latitudes and high latitudes on Mars. In the northern hemisphere, the craters are widely distributed geographically and occur at latitudes as low as 39°N. Stability modeling suggests that this ice distribution requires a long-term average atmospheric water vapor content around 25 precipitable micrometers, more than double the present value, which is consistent with the expected effect of recent orbital variations. Alternatively, near-surface humidity could be higher than expected for current column abundances if water vapor is not well mixed with atmospheric CO2, or the vapor pressure at the ice table could be lower due to salts. Ice in and around the craters remains visibly bright for months to years, indicating that it is clean ice rather than ice-cemented regolith. Although some clean ice may be produced by the impact process, it is likely that the original ground ice was excess ice (exceeding dry soil pore space) in many cases. Observations of the craters suggest small-scale heterogeneities in this excess ice. The origin of such ice is uncertain. Ice lens formation by migration of thin films of liquid is most consistent with local heterogeneity in ice content and common surface boulders, but in some cases, nearby thermokarst landforms suggest large amounts of excess ice that may be best explained by a degraded ice sheet.