How Do You Solve a Moon Mystery? Fire a Laser at It

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https://www.nytimes.com/2020/08/15/science/moon-lasers-dust.html

Source:  By Katherine Kornei, The New York Times. 

Excerpt: The moon is drifting away. Every year, it gets about an inch and a half farther from us. Hundreds of millions of years from now, our companion in the sky will be distant enough that there will be no more total solar eclipses. For decades, scientists have measured the moon’s retreat by firing a laser at light-reflecting panels, known as retroreflectors, that were left on the lunar surface, and then timing the light’s round trip. But the moon’s five retroreflectors are old, and they’re now much less efficient at flinging back light. To determine whether a layer of moon dust might be the culprit, researchers devised an audacious plan: They bounced laser light off a much smaller but newer retroreflector mounted aboard a NASA spacecraft that was skimming over the moon’s surface at thousands of miles per hour. And it worked. These results were published this month in the journal Earth, Planets and Space [https://earth-planets-space.springeropen.com/articles/10.1186/s40623-020-01243-w].... 

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