On 17th March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium, It exploded in a flash nearly 10 times as bright as anything seen before. Anyone looking at the Moon at the moment of impact could have seen the explosion–no telescope required. For about one second, the impact site was glowing like a 4th magnitude star.
The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon traveling 56,000 mph. The resulting explosion1 packed as much punch as 5 tons of TNT.
NASA and University of Western Ontario all-sky cameras picked up an unusual number of deep-penetrating meteors right here on Earth. These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt.
This means Earth and the Moon were pelted by meteoroids at about the same time.
NASA’s lunar monitoring program has detected hundreds of meteoroid impacts. The brightest on 17h March 2013, in Mare Imbrium, is marked by the red square on the image above.