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The incredible shrinking Moon

New electronic images, beamed back to Earth by NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft last week, show that the Moon is shrinking. Images of 14 recently discovered lunar cliffs reveal that our nearest neighbor in space has been slowly shrinking since it first started cooling off billions of years ago.

In Moon terms, the big cliffs aren't too old-about 100 million years young, but they reveal an odd tectonic phenomenon that happened in "recent" times. The distance between the lunar center and the surface shrank by more than 300 feet, based on the height of the largest cliff faces (that's the height of NASA's old Saturn-5 Moon rocket). The cliffs pictured in LRO images published last week are the result of global crustal contraction. They are akin to the ugly furrows of an apple left neglected on a kitchen counter for many weeks.

Called lobate scarps, Dr. Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum said the cliffs highlight the need for ongoing spacecraft-based global lunar observations. But with NASA's lunar exploration plans shrinking faster than the Moon's crust-all thanks to an anti-space White House administration-such desires may be but a sign of hypnagogia in the inauspicious Obama Space Age.

Since the Moon is over a third of the volume of the planet Mercury, its lobate scarps are smaller. As a result, according to NASA, the Moon shrank less than Mercury. And because the lunar cliffs appear to be very young, the Moon is still cooling and shrinking. Some moonquakes are probably signatures of ongoing shrinking.

Following the Apollo era, it was assumed there was nothing new in lunar geology. Since the U.S. Clementine and Lunar Prospector spacecraft of the 1990s, we now know that the Moon is truly a vast, unexplored world with lots of geological surprises just around the corner.

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