for National Geographic News
New data on Mars's underground ice shows that the red planet likely has a very active water cycle.
Using heat emission observations from the Mars Odyssey spacecraft, researchers were able to map seasonal changes in the temperature of the red planet's surface to locate and measure the buried ice.
"This gives us a more detailed picture of the underground ice on Mars," said Joshua Bandfield, a research specialist at Arizona State University's School of Earth and Space Exploration in Tempe, who led the study.
The findings, which are reported in tomorrow's issue of the journal Nature, show that the depth of the water-ice table varies greatly on Mars.
The results also suggest that water ice and water vapor in the planet's atmosphere can swap places as the planet undergoes regular cycles of warming and cooling.
Scientists have long known that the red planet has large pockets of subterranean ice. (Related: "Mars Pole Holds Enough Ice to Flood Planet, Radar Study Shows" [March 15, 2007].)
But previous measurements of the buried ice using NASA's Odyssey orbiter were somewhat blurred, because they each spanned several hundred miles. (Related: "Mars Scientists Intensify Search for Water" [December 15, 2006].)
By contrast, Odyssey's Thermal Emission Imaging System (THEMIS) uses infrared wavelengths to see details on the surface of Mars that are just 330 feet (100 meters) wide.
"The new method offers more than a hundredfold increase in spatial resolution," Bandfield said.
Infrared images were taken of several Martian regions where subsurface water was known to exist. (See a map of Mars.)
By looking at how the surface temperature changed through Mars's seasons, scientists were able to determine the depth of the ice layer in those areas.
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