Thursday, April 21, 2011

Mars' Thick Dry Ice Sheet Points to Planet's Wetter Past

The south pole of Mars has a layer of dry ice that is 30 times thicker than previously thought, a find that suggests the Red Planet may have had more liquid water on its the surface in the distant past, scientists say. While most of the ice at the Martian south pole is frozen water, some of the ice pack is composed of dry ice — frozen carbon dioxide.

A team of scientists used a radar instrument on NASA's Mars Reconnaissance Orbiter to calculate the depth of dry ice deposits. By measuring how long it took for the radar waves to travel through the ice and bounce back to the MRO spacecraft, the researchers determined the dry ice cache was nearly 2,300 feet (700 meters) thick.

"The volume of the deposit is about the volume of Lake Superior," said study leader Roger Phillips of the Southwest Research Institute.

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