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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Martian Ice on the Rocks
6 December 2002 (All day)
Space scientists have discovered a new hiding place for water on Mars. A kilometer-wide patch of frozen water at the edge of the planet's southern polar cap was exposed when an upper layer of carbon dioxide ice (“dry ice”) evaporated. This discovery might literally be the tip of an iceberg: Some Mars scientists believe that the entire southern polar cap could be water ice, covered by a veneer of dry ice.
The orbiting Mars Odyssey spacecraft first glimpsed the water ice in February. What caught scientists' attention was a relatively flat piece of land that was colder than the adjacent exposed soil. More-detailed measurements made with the spacecraft's infrared camera revealed that the plain absorbed more heat than the surrounding terrain during the day and radiated more heat at night. That strongly suggested that the surface was pure water ice.
Tracking this region's history, Phillip Christensen of Arizona State University, Tempe, and colleagues examined old photographs of the area taken by NASA's Viking orbiter mission in the 1970s. Sure enough, the photos showed sharp delineations between bright dry ice, medium-bright water ice, and dark rock. The transitions between thermally distinct regions seen by the Mars Odyssey corresponded to transitions between visibly distinct regions in the Viking photos. The icy plain, the researchers conclude, is a regular feature that has reappeared every martian summer for at least 25 years as the dry ice periodically melts off, the researchers report online 5 December in Science. Viking saw many similar medium-brightness patches around the edges of the southern ice cap, so seasonal plains of water ice might be fairly common.
The ice deposits might someday provide a record of Mars's climatic history, just as glaciers do on Earth. “In many ways, Mars should be a simpler system than Earth for understanding climate change,” says Ken Herkenhoff of the U.S. Geological Survey. “There are no oceans on Mars, and no biological community that we know of.” Thus Mars could serve as a laboratory for understanding the effects of orbital mechanics and of the sun's variations on climate.