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Mars radiation too intense for life

NASA's Mars Odyssey spacecraft has confirmed suspicions that the radiation on Mars is so intense that it could endanger astronauts sent to explore the planet, scientists said this week.

The high radiation levels measured by the unmanned probe suggest any extraterrestrial life that might call Mars home would have little chance of surviving unless it were shielded beneath the planet's dusty, cold surface, said Cary Zeitlin of the National Space Biomedical Research Institute in Houston.

"It would have to be pretty robust against all kinds of environmental horrors," said Zeitlin, one of the scientists working on the project.

The conclusions stemmed from new data released by scientists at NASA's Jet Propulsion Laboratory from the first year of scientific results from the $300-million mission.

Scientists also presented information on the minerals and elements that make up the planet's surface, including measurements that show its northern hemisphere is richer in water than its southern half. Near the planet's north pole, frozen water makes up as much as 75 percent, by volume, of the top 3 feet or so of soil, said William Boynton, one of the mission's scientists.

NASA talks vaguely of future manned missions to Mars, where astronauts could use that ice for drinking water, fuel and oxygen to breathe. The new radiation findings suggest such a mission would be risky.

Cloud cover has tamed warming of Arctic region, report says

The well-documented warmup of the Arctic region would be more drastic had it not been for a change in seasonal cloud cover over the area during the past two decades, researchers reported in a study Friday.

Arctic surface temperatures have increased by as much as 11 degrees Fahrenheit during the winter in parts of Alaska and Eurasia in the past 30 years. But while a number of researchers have monitored those temperature changes and changes in the extent of sea ice cover, few have looked at other conditions, such as cloud cover and the reflectivity of snow and ice, and how these interact.

Researchers at the University of Wisconsin-Madison found that spring and summer cloud cover has increased by 2 to 4 percent per decade over the region, but that winter cloud cover has decreased.

"It appears that if cloud conditions weren't changing, the Arctic would be getting even warmer, which means more ice would be melting," said Jeff Key, a scientist with the National Oceanic and Atmospheric Administration at Wisconsin's Cooperative Institute for Meteorological Satellite Studies and co-author of the study published in the journal Science.

Hubble spots new, melting planet

The Hubble Space Telescope has detected an extensive atmosphere of hydrogen enveloping and escaping from a newfound planet of a distant star, scientists report.

The discovery comes as no surprise, astronomers say, but it is important nonetheless as apparent confirmation that the extrasolar planets observed not only are much like the solar system's Jupiter in size but also are similarly huge gaseous bodies.

In an announcement by the European Space Agency and NASA, a French-led research team said three separate observations by the Hubble telescope had revealed a hot and puffed-up hydrogen atmosphere surrounding a planet orbiting the star HD 209458, in the constellation Pegasus 150 light-years from Earth. Details were described in Thursday's Nature.

The most astonishing aspect, said the team leader, Alfred Vidal-Madjar of the Astrophysics Institute of Paris, is the planet is so close to the searing heat of its parent star that the dense atmosphere reaches temperatures of about 18,000 degrees Fahrenheit and is boiling off and evaporating at a rate of perhaps 10,000 tons a second.

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