"It exploded in a flash  nearly 10 times as bright as anything we've ever seen before," said Bill  Cooke, of NASA's Meteoroid Environment Office.
NASA astronomers have  been monitoring the moon for the past eight years, looking for  explosions caused by meteoroids hitting the lunar surface. It's part of a  program to find new fields of space debris that could hit Earth. NASA  says it sees hundreds of detectable lunar meteoroid impacts a year. 
None however can match  the size of the explosion they say they saw March 17. NASA says the  meteoroid was about 40 kilograms and less than a meter wide, and it hit  the moon's surface at 56,000 mph. It glowed like a 4th magnitude star,  NASA says, thanks to an explosion equivalent to 5 tons of TNT.
Cooke says Earth was  pelted by meteoroids at about the same time, but they hit the moon  because it has no atmosphere to protect it.
"We'll be keeping an eye  out for signs of a repeat performance next year when the Earth-moon  system passes through the same region of space," Cooke said.
If you're wondering how  there can be an explosion on the moon, without oxygen, NASA has the  answer for you. It says the flash of light comes not from any type of  combustion -- as we typically think of explosions -- but rather by the  glowing molten rock at the impact site.
 

 
 
 
 
 
 
 
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