The meteorite fell on March 17, crashing into the lunar surface at 56,000 mph, and Bill Cooke of NASA's Meteoroid Environment Office said it "exploded in a flash nearly 10 times as bright as anything we've ever seen before."
The impact would have been visible to the naked eye from Earth, but NASA watchers didn't notice it in real time. Ron Suggs, an analyst at NASA's Marshall Space Flight Center in Huntsville, Ala., discovered the event when reviewing video recorded by one of the moon monitoring program's 14-inch telescopes.
Scientists estimate the rock was about 1 foot wide and weighed about 88 pounds.The explosion it created was as powerful as 5 tons of TNT, according to NASA scientists.
After noticing the impact, scientists went back over March data for Earth and found other objects. "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," Cooke said. "These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt."
Earth's atmosphere protects the surface from many of these small objects, but the moon is more vulnerable. Scientists have been monitoring moon impacts to determine whether impacts and frequency pose greater danger during certain times of the year.