Deep down, Mars harbors a lot of ice

Frozen water may even be drinkable, scientists say

Keay Davidson, Chronicle Science Writer
Tuesday, December 6, 2005

Century-old fancies of a past Mars covered with warm, sparkling seas are fading, as scientists realize the planet's rust-red surface has probably been a dry, frigid icebox for almost all of its history.

That doesn't necessarily mean that Martian microbes aren't thriving at this very moment in volcanically heated subterranean swimming pools thousands of feet beneath the surface -- the scientific jury is still out on that popular hypothesis. But whenever liquid water squirted to the surface during the past 3.5 billion years, it usually sloshed around for only brief periods before freezing or vaporizing in the drier-than-Sahara wasteland, judging by scientific evidence reported Monday at the annual San Francisco meeting of the American Geophysical Union.

Still, there's a breathtaking amount of frozen water at the Martian poles and possibly also in buried craters around the planet, scientists noted at the conference. They cited evidence of abundant frozen water on or beneath the Martian surface -- more than enough water, perhaps, to quench the thirst of future human astronauts and perhaps enough to nourish subterranean microbes, if they exist.

On the one hand, the surface of "Mars is extremely dry, drier than any (place) we have on Earth," said Gerhard Neukum, a German scientist who has analyzed stereo images of the Martian surface recorded by the European Space Agency's Mars Express satellite that began orbiting the fourth planet from the Sun in late 2003.

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