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Moon has shrunk, scientists say

Washington -- U.S. scientists examining new images of the moon say the Earth's partner shrank in the geologically recent past and may be shrinking still.

Images from NASA's Lunar Reconnaissance Orbiter spacecraft show cliffs in the lunar crust that researchers say is evidence of cooling and contractions of the lunar interior, a NASA release reported Thursday.

The moon formed in a chaotic environment of intense bombardment by asteroids and meteors and of decay of its radioactive elements that made it hot. Scientists have long believed the moon has shrunk over time as it cooled, and say the shrinking caused the newly discovered cliffs.

"We estimate these cliffs, called lobate scarps, formed less than a billion years ago, and they could be as young as a hundred million years," Thomas Watters of the Center for Earth and Planetary Studies in Washington said.

A time period of a billion years, while extremely ancient in human terms, is less than 25 percent of the moon's age of more than 4 billion years, he said.

"Based on the size of the scarps, we estimate the distance between the moon's center and its surface shrank by about 300 feet," Watters said.

Researchers say they believe the cliffs are among the freshest features on the moon, and look crisp and relatively intact, lending more evidence to the shrinking of the moon being a fairly recent and even continuing phenomenon.

Copyright 2010 United Press International

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