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Radar probes frozen water at Martian pole

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7:54am, March 28, 2007
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If all the frozen water stored near the south pole of Mars suddenly melted, it would make a planetwide ocean 11 meters deep. That's what planetary scientists have concluded using data from a Mars-orbiting spacecraft that bounced radio waves off the Red Planet's south polar region.

The finding confirms previous studies showing that the poles of Mars contain the largest known reservoirs of water on the planet. It also provides a more accurate assessment of the frozen, layered deposits at the south pole, Jeff Plaut of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and his colleagues report in an upcoming Science.

Plaut's team relied on a radar instrument on the European Space Agency's Mars Express orbiter to record echoes from the polar-ice deposits, which cover an area larger than Texas.

Although dust darkens some of the ice layers, the strength of the radar reflections indicates that the frozen material is at least 90 percent pure water-ice. Penetrating some 3.7 kilometers through the ice to the underlying Martian crust, the radar study also revealed an area of buried depressions. Ranging in width from 50 to 200 km, the depressions may be impact craters gouged into the Martian surface before the polar ice formed. The weight of the overlying ice has not significantly compressed the crust, indicating that both it and the upper mantle of Mars are much stiffer than Earth's, probably because the Martian interior is much colder, Plaut notes.

An earlier, briefer study of the Martian north-polar region with the same radar detector found no such depressions beneath the vast deposits of water-ice there.

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