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Wednesday, 17 January, 2001, 14:31 GMT
Ice may have shaped Martian surface
Anarctica and Mars AGU
Antarctic ice flow (left) is similar to Martian Ares Vallis
Some channels visible on the surface of Mars may have been gouged by ice, rather than by catastrophic flooding, as is generally believed.

The observations strongly support the notion that an ocean once existed in the northern plains of Mars

Dr Baerbel Lucchitta
Using sonar images that have only recently become available, Dr Baerbel Lucchitta of the US Geological Survey in Flagstaff, Arizona, has found features on the Antarctic sea floor which appear similar to those on Mars.

Ice flows in streams within Antarctica's ice sheets before merging with ice shelves in the surrounding ocean. Along the way it gouges the land and sea floor.

Features on the Martian surface, especially one known as Kasei Valles, look very much like Antarctic channels known to have been carved by ice.

Martian channels arise suddenly from chaotic terrains or fractures, and terminate in the northern plains, where there may once have been an ocean.

Northern Ocean

Dr Lucchitta compared the Rutford ice stream, where it joins the Ronne ice shelf, with an area of Mars called Ares Vallis. The two structures appeared identical, she said.

Anarctica and Martian features AGU
Sonar image of Antarctic sea floor (left) matches Martian feature
In Antarctica, the ice stream diverges round an area of stable ice. The Martian channel routes round an "island" of high ground and displays similar curved flow lines where it enters the hypothetical ocean

Dr Lucchitta believes that Ares Vallis was filled by material that had the characteristics of flowing ice that entered an ice covered body of water.

Dust covered ice may persist in Ares Vallis. Or it may be that rocky material left an imprint of the flow forms after the ice evaporated.

"The observations strongly support the notion that an ocean once existed in the northern plains of Mars," said Dr Lucchitta.

Her findings will be reported in the next issue of the Geophysical Research Letters, published by the American Geophysical Union.

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