May 21, 2008: Not so long ago, anyone claiming to see flashes of light on the Moon would be viewed with deep suspicion by professional astronomers. Such reports were filed under "L" … for lunatic.
Not anymore. Over the past two and a half years, NASA astronomers have observed the Moon flashing at them not just once but one hundred times.
"They're explosions caused by meteoroids hitting the Moon," explains Bill Cooke, head of NASA's Meteoroid Environment Office at the Marshall Space Flight Center (MSFC). "A typical blast is about as powerful as a few hundred pounds of TNT and can be photographed easily using a backyard telescope."
As an example, he offers this video of an impact near crater Gauss on January 4, 2008:
Above: A lunar impact on Jan. 4, 2008. This is number 86 on the list of 100 impacts recorded by the MEO team since their survey began in 2005. Larger movies: 0.8 MB gif, 5.9 MB avi.
The impactor was a tiny fragment of extinct comet 2003 EH1. Every year in early January, the Earth-Moon system passes through a stream of debris from that comet, producing the well-known Quadrantid meteor shower. Here on Earth, Quadrantids disintegrate as flashes of light in the atmosphere; on the airless Moon they hit the ground and explode.
"We started our monitoring program in late 2005 after NASA announced plans to return astronauts to the Moon," says team leader Rob Suggs of the MSFC. If people were going to be walking around up there, "it seemed like a good idea to measure how often the Moon was getting hit."
"Almost immediately, we detected a flash."
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