Moon's radiation tolerable for explorers
Published 4:00 am, Wednesday, December 16, 2009
The NASA spacecraft circling the moon on a reconnaissance mission for future astronauts has found that potentially toxic radiation from the sun is tolerable for any new generation of lunar explorers who may return there, scientists report.
The Lunar Reconnaissance Orbiter flew over the site where another spacecraft named LCROSS blasted the surface of a darkly shadowed crater with an empty rocket casing in October and confirmed that the moon holds copious amounts of water in its rocks. That spacecraft ended its mission crashing onto the surface soon after.
The orbiter is flying barely 30 miles above the moon's surface to map its environment at relatively close range and scout out potential landing sites for future manned expeditions there.
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If astronauts return to the moon, they'll find the deep craters there unbelievably cold, said David Page of UCLA, the scientist directing one of the orbiter's seven instruments. Midwinter temperatures in one shadowed crater reach 416 degrees below zero Fahrenheit - colder than any discovered anywhere else in the solar system, he said. It's hot enough in the lunar sunshine, though: 170 degrees.
The orbiter detected abundant cosmic rays raining down from the Milky Way, plus more solar radiation from magnetic storms and other charged particles kicked up from the moon's surface by the sun's activity, said Harlan Spence of Boston University and the University of New Hampshire.
The sun's surface undergoes an 11-year cycle of magnetic activity, with major storms at the cycle's peak. Although this is a quiet solar year, the spacecraft detected unexpectedly high solar radiation levels, Spence said. They were about as high as X-ray technicians or uranium miners might normally experience in a year, and would be tolerable for future lunar explorers with protective suits similar to those worn by the Apollo astronauts, he said.
Michael Wargo, NASA's chief lunar scientist at the agency's Washington headquarters, noted that if future astronauts were to spend long periods on the moon exploring or building habitats, they would need to know when to seek shelter from high radiation during major solar storms.
Predicting them today is extremely complex and far from perfect, Wargo said, and that's a field of science that needs major advances before humans can consider long-term stays on the moon, he said.