Trickle Down Theory of Melting Snow May Support Life on Mars.
By Leonard David
Senior Space Writer
posted: 02:00 pm ET
19 February 2003
"Intriguing and often-examined gullies on Mars might not be created by water seeping out from underground springs. Rather, they are likely caused by trickling water from melting snowpacks, an active process that could sustain biology on the Red Planet.
"A leading Mars scientist has proposed a new theory regarding gully formation on the planet, backed by images taken from NASA's Mars Odyssey spacecraft. The research bolsters the view that liquid water is sheltered by snow, preventing the fluid from rapid evaporation in Mars' thin atmosphere."
...
"Christensen points to an image taken by Odyssey of a crater in the southern mid-latitude Terra Sirenum region of Mars. It shows eroded gullies on the crater's cold, pole-facing northern wall, he said. But immediately next to those features is a section he calls "pasted-on terrain."
"This smooth deposit of material is thought to be "volatile," composed of materials that evaporate in Mars' thin atmosphere. This material characteristically occurs only in the coldest, most sheltered areas.
"Christensen reported that the most likely composition of this slowly evaporating material is water in the form of snow. From this observation, the Mars scientist suspects a relationship between the gullies and the snow."
http://www.space.com/scienceastronomy/mars_gullies_030219.html

Snow Gullies on Mars
NASA spacecraft may have finally found the mysterious source of gullies on Mars: melting snow.
http://science.nasa.gov/headlines/y2003/19feb_snow.htm

Slippery slopes: Did melting snow carve the gullies on Mars?
Nature 422, 45-48 (6 March 2003) | doi:10.1038/nature01436
http://www.nature.com/nature/links/030306/030306-1.html
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Bob Clark