Ice on Mars

Under Heavy Construction

[Mars south polar cap]
Mosaic of the Martian South Polar Cap

[Mars north polar cap] The most dramatic evidence of water on mars is at the north and south polar caps, which are composed of water ice and carbon dioxide. the size of the caps changes dramatically with the season. The north polar cap exhibits extensive complex layering, which probably records seasonal changes in ice and layers of material deposited during global martian dust storms.

[Frost at Viking 2 Lander Site] Ground frost was recorded at dawn by the Viking 2 cameras in late northern winter. (The Viking 2 landing site was at 46.7 degrees north latitude.) This frost persisted as temperatures rose above the sublimation point of carbon dioxide, convincing evidence that the frost was at least in part water ice.

[Parana Vallis drainage system on Mars] Although there is very little water vapor or ice apparent on Mars today, there is convincing evidence that water existed in larger quanitities in the past, and probably even flowed as liquid water on the surface as shown by stream channel-like features and features which strongly resemble artifacts of large catastrophic floods on the surface. Liquid water cannot exist on Mars under the current low atmospheric pressure. There are also craters which have ejecta lobes which appear to have been fluidized, presumably by underground ice which melted due to impact and flowed briefly. Such underground permafrost may still persist on Mars.
[Yuty Crater on Mars]

Yuty Crater on Mars, showing an ejecta blanket which may be due to mobilization of fluidized material due to impact melting of sub-surface ice.

Large amounts of water in the past may also imply that glaciers were active. There is possible evidence of glacial action on Mars: eskers, tunnel channels, and kames are tentatively identified in the image below (1).
[Image of possible glacial features on Mars]

The Mars Surveyor 98 Lander will land near Mars' south pole in December, 1999. This mission will have meteorology instruments, a gas analyzer, imagers, a laser ranger/dust detector, and a robot arm to dig trenches. The lander will set down at approximately 71 degrees south latitude, the most northerly extent of the south pole layered deposits.

References

1) Evidence of ancient continental glaciation in the Martian northern plains, Kargel et al., Journal of Geophysical Research, v. 100, p. 5351, 1995
2) Polar Deposits of Mars, Thomas et al., in Mars, Univ. of Arizona Press, Tucson, p. 767, 1992
3) Water on Mars, Carr, Nature, v. 326, p. 30, 1987
4) Ice in the martian regolith, Squyres et al., in Mars, Univ. of Arizona Press, Tucson, p. 523, 1992
5) The seasonal behavior of water on Mars, Jakosky and Haberle, in Mars, Univ. of Arizona Press, Tucson, p. 969, 1992

Mars Fact Sheet
Mars Home Page
Viking
More images of Mars - Catalog of Spaceborne Imaging
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Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
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NASA Official: Ed Grayzeck, edwin.j.grayzeck@nasa.gov
Last Updated: 06 January 2005, DRW