Melting glaciers rather than flowing surface water could have carved out the Red Planet's distinctive valleys.
Branching networks of small valleys have led many scientists to conclude that rivers of running water once flowed freely across the surface of Mars. But this would mean that the Red Planet once had a much warmer climate than it does today and, apart from its valleys, there is no evidence to suggest that Mars was ever warm (New Scientist, 17 April 1999, p 48).
But Pascal Lee, a planetary scientist at NASA's Ames Research Center in Mountain View, California, says the answer may be found on Devon Island in the Canadian Arctic, where he is studying valleys carved by glacial meltwater. "What we've been finding on Devon Island," says Lee, "is a wide variety of valley types, from canyons to little networks of small valleys, that bear an uncanny resemblance to specific counterparts on Mars."
In particular, he says, the Martian valleys "cut through a desert that otherwise has very little sign of water flowing nearby". The constant width and depth of Martian valleys over long distances, their flat floors and steep walls are all distinctive features also found on Devon Island, but uncommon on river networks.
Lee believes that other Martian landforms, notably some large canyons on the west end of Vallis Marineris, could actually have been carved by flowing glacial ice. Devon Island also has canyons like these, he told the 31st Lunar and Planetary Institute Science Conference in Houston, Texas, last week.
If Lee is correct, Mars may have had a cold climate, in which snowfall piled up to form glaciers that later melted in the heat generated inside the planet. Mars expert Jim Head of Brown University, Rhode Island, welcomes Lee's work, saying the analogy to Devon Island is helping him visualise how melting snow might have produced valleys on Mars.
Reporter: Henry Bortman
New Scientist issue: 25th March 2000
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