NASA Discovers Ice in Huge Crater on the Moon's South Pole
On the south pole of the moon, NASA scientists have found ice scattered across the surface of a two-mile deep crater.
New data from NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft show that frozen water makes up as much as 22 percent of the surface material in the Shackleton crater, which is 12 miles wide and permanently dark due to the tilt of the lunar axis.
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NASA scientists used laser light from the LRO altimeter to examine the floor of the crater, which they found to be brighter than the floor of nearby craters, suggesting that ice may be present.
"The brightness measurements have been puzzling us since two summers ago," said Gregory Neumann of NASA's Goddard Space Flight Center in Greenbelt, Md., a co-author on the paper. "While the distribution of brightness was not exactly what we had expected, practically every measurement related to ice and other volatile compounds on the moon is surprising, given the cosmically cold temperatures inside its polar craters."
Though it may sound like a lot, the ice that is present in the Shackleton crater may only make up less than a quarter of the first layer of the crater's floor, which is just one micron thick. A strand of human hair is about 100 microns aross. Lead investigator Maria Zuber of the Massachusetts Institute of Technology says it is about 100 gallons of frozen water, according to CNN. However, these measurements aren't at all indicative of what ice may be beneath the surface.
They were also able to use their measurements to map the terrain inside the crater, which is remarkably well-preserved for being 3 billion years old. They found that it contains several small craters that may have occurred during the collision that created the Shackleton crater.
"The crater's interior is extremely rugged," said Zuber. "It would not be easy to crawl around in there."
Another puzzling find was that the crater's floor was relatively bright, but the walls were even brighter. Scientists had thought that if ice were to form there, it would be contained to the floor, which receives no direct sunlight. The upper walls of the crater are occasionally illuminated, which could evaporate any ice that forms.
A theory offered by the team to explain the puzzle is that 'moonquakes' - seismic shaking brought on by meteorite impacts or gravitational tides from Earth - may have caused Shackleton's walls to slough off older, darker soil, revealing newer, brighter soil underneath, reports The Daily Mail.
"There may be multiple explanations for the observed brightness throughout the crater," said Zuber. "For example, newer material may be exposed along its walls, while ice may be mixed in with its floor."
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