The U.S. space agency NASA has been watching the Moon for about eight years, looking for signs of meteoroids hitting the lunar surface.
The results show that hundreds of recorded impacts occur each year. However, the biggest one ever recorded occurred on March 17th
Bill Cooke, of the Meteoroid Environment Office at NASA, stated, “On 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 we've ever seen before."
According to the March 17, 2013 NASA article Bright Explosion on the Moon, the impact was viewable by anyone who happened to be looking at the Moon at the time of the explosion. Binoculars or telescopes were not needed, only naked eye observations.
NASA stated that the explosion “packed as much punch as 5 tons of TNT.”
Cooke added that “… 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."
NASA contends that this meteor that hit the Moon and other meteors hit both the Earth and the Moon at about the same time.
For more on the story, please read the May 17, 2013 National Geographic article “NASA Announces Brightest Lunar Explosion Ever Recorded”.