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FLOWING ice may have carved the giant channels on Mars previously put down to
cataclysmic floods. The features on the floor of the Kasei Valles on Mars look
just like those at the base of Antarctic ice streams, says Baerbel Lucchitta of
the US Geological Survey in Flagstaff, Arizona.

The channels are tens of kilometres wide and hundreds of kilometres long.
Many scientists think they were created when underground ice in the uplands
melted鈥攑erhaps because of volcanic activity鈥攁nd the water rushed
downhill to the northern plains. But such floods would have been far bigger than
anything seen on Earth. What鈥檚 more, some of the channels run gently uphill.

Recent sonar images of the sea floor off the Antarctic have revealed channels
cut by flows of ice from the Ross ice shelf during the last ice age, when the
sea level was lower. 鈥淭hese look just like the markings we see in this Martian
channel,鈥� says Lucchitta.

She believes the ancient Martian water froze as it flowed downhill, forming a
large mass of ice. Some water beneath it remained liquid, lubricating the ice as
it slipped downhill. Like a moving ice dam in a partly frozen river, the ice cut
a wide swathe as it moved. Ice flowing downhill sometimes pushed the ice in
front up gentle slopes, as Lucchitta saw off Antarctica. In this way, a
relatively small amount of water could have carved the giant Martian
channels.

鈥淚t鈥檚 a perfectly reasonable explanation,鈥� says Pascal Lee of NASA鈥檚 Ames
Research Center, who last year reported that glacial meltwater may have cut the
many small valleys found in the southern highlands of Mars. 鈥淚ce may have played
a bigger role than we thought.鈥�