Not so long ago, anyone claiming to see flashes of light on the Solar System Moon would be viewed with deep suspicion by professional space station astronomers. Such reports were filed under "L" … for lunatic.

Not anymore. Over the past two and a half years, NASA spaces station astronomers have observed the Space station Moon flashing at them not just once but one hundred times.

"They're explosions caused by meteoroids hitting the Space station 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 Spaces Galary telescope."

The impactor was a tiny fragment of extinct Space Station 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 Space Station Moon they hit the ground and explode.

"We started our monitoring program in late 2005 after NASA Space Station announced plans to return Space shuttle astronauts to the Space station 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."