A meteoroid has smashed into the Moon, causing the biggest explosion ever seen on the lunar surface which was visible from Earth with the naked-eye, NASA said.
"On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium," said Bill Cooke of NASA's Meteoroid Environment Office.
"It exploded in a flash nearly 10 times as bright as anything we've ever seen before," said Cooke.
Anyone looking at the Moon at the moment of impact could have seen the explosion - no telescope was required. For about one second, the impact site was glowing like a 4th magnitude star, researchers said.
Ron Suggs, an analyst at the Marshall Space Flight Center, was the first to notice the impact in a digital video recorded by one of the monitoring program's 14-inch telescopes, said NASA.
"It jumped right out at me, it was so bright," he said.
The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon travelling 90123 kph. The resulting explosion packed as much punch as 5 tonnes of TNT. Cooke believes the lunar impact might have been part of a much larger event.
"On the night of March 17, NASA and University of Western Ontario all-sky cameras picked up an unusual number of deep-penetrating meteors right here on Earth," he said.
"These fireballs were travelling along nearly identical orbits between Earth and the asteroid belt," said Cooke.
This means Earth and the Moon were pelted by meteoroids at about the same time, researchers said.
"My working hypothesis is that the two events are related, and that this constitutes a short duration cluster of material encountered by the Earth-Moon system," said Cooke.
One of the goals of the lunar monitoring programme is to identify new streams of space debris that pose a potential threat to the Earth-Moon system. The March 17th event seems to be a good candidate.
Controllers of NASA's Lunar Reconnaissance Orbiter have been notified of the strike. The crater could be as wide as 20 meters, which would make it an easy target for LRO the next time the spacecraft passes over the impact site.
"Lunar meteors" crash into the ground with fair frequency. Since the monitoring programme began in 2005, NASA's lunar impact team has detected more than 300 strikes, most orders of magnitude fainter than the March 17th event.
