HiRISE observations of new impact craters exposing Martian ground ice

Colin M. Dundas, Shane Byrne, Alfred S. McEwen, Michael T. Mellon, Megan R. Kennedy, Ingrid J. Daubar, Lee Saper

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

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 CO 2, 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. Key Points New impact craters expose ground ice at high latitudes on Mars Ice is found at latitudes as low as 39°N Ice remains visible for many months, indicating low regolith content

Original languageEnglish (US)
Pages (from-to)109-127
Number of pages19
JournalJournal of Geophysical Research: Space Physics
Volume119
Issue number1
DOIs
StatePublished - Jan 2014

Fingerprint

Ice
craters
crater
ice
regolith
Steam
polar regions
mars
Mars
water vapor
Dry Ice
Landforms
thermokarst
landforms
Carbon Monoxide
pore space
Vapor pressure
Northern Hemisphere
vapor pressure

Keywords

  • Ground Ice
  • Impact Craters
  • Mars

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

HiRISE observations of new impact craters exposing Martian ground ice. / Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.; Mellon, Michael T.; Kennedy, Megan R.; Daubar, Ingrid J.; Saper, Lee.

In: Journal of Geophysical Research: Space Physics, Vol. 119, No. 1, 01.2014, p. 109-127.

Research output: Contribution to journalArticle

Dundas, Colin M. ; Byrne, Shane ; McEwen, Alfred S. ; Mellon, Michael T. ; Kennedy, Megan R. ; Daubar, Ingrid J. ; Saper, Lee. / HiRISE observations of new impact craters exposing Martian ground ice. In: Journal of Geophysical Research: Space Physics. 2014 ; Vol. 119, No. 1. pp. 109-127.
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