Crater Imagery Suggests Mars Ice

Feb 11, 2009
By Aerospace Daily & Defense Report



Drastic shifts in the axis of rotation on Mars over time could have created polar ice sheets that flowed in some areas, shaping the terrain below in ways that can be seen today.

Scientists examining erosion in mid-latitude craters on both sides of the planet's equator see differences that suggest local warming from sunlight was a factor in the direction that long-gone ice-rich material - or perhaps liquid water - once flowed in.

"Studying crater degradation in potentially ice-rich environments is vital to understanding the geology of craters and their surroundings, as well as for determining whether the ice comes from the atmosphere or from below the ground," says Daniel Berman, an associate research scientist at the Planetary Science Institute (PSI) in Tucson, Ariz., who was lead author of a paper on the subject published in Icarus, the journal of the American Astronomical Society's planetary sciences division.

Berman and his group studied imagery from Mars Odyssey, Mars Global Surveyor and even the old Viking missions for patterns in such features as gullies, debris aprons and lobate flows.

Concentrating on craters larger than about 12.5 miles, they found that the latitude of the crater determined how its terrain was oriented toward the nearest pole, suggesting that "ice on walls that get more sunlight would melt faster, causing more water to flow and form the gullies and other features," according to the PSI.

On a macro scale, the results suggest that large changes in the tilt of the planet's axis led to the evaporation and formation of ice sheets at opposite poles, PSI says.

Artist's concept of Mars Global Surveyor: NASA