A meteorite the size of a compact car crashed into the Moon, creating a record-breaking impact. The event occurred on 11 September 2013, becoming the largest such impact ever seen. The collision occurred in Mare Nubium, an ancient lava basin.
The flash was bright enough to be seen from Earth, and the afterglow was seen for eight seconds.
"At that moment I realized that I had seen a very rare and extraordinary event," Jose Madiedo, who first reported the event, told the press. The astronomer works at the University of Huelva (UHU).
Because the Moon has no atmosphere, our celestial neighbor is impacted by meteors on a regular basis. To watch these events, astronomers have developed networks of telescopes designed to image the collisions. The impact in September was recorded by a pair of optical telescopes in Spain.
Normally, flashes from impacts last a small fraction of a second. Light from the impact recorded by Madiedo and his team was far brighter and lasted much longer any any collision seen before by astronomers.
Researchers estimate the meteor responsible for the collision weighed 880 pounds, and had a diameter between two and five feet across. When the object struck the Moon, it was traveling at a speed of 56,000 miles per hour. The resulting explosion was equivalent to 15 tons of TNT, and produced an impact crater 65 feet in diameter.
"It is, therefore, at least three times more powerful than the greatest impact detected to date in the Moon by NASA and was recorded by the U.S. space agency on March 17 last year," researchers wrote on the University Web site.
Because there is no way of predicting most asteroid impacts, the event was only visible to those who happened to be glancing at the Moon at the exact moment it was struck by the speedy boulder.
The atmosphere of Earth protects us from small impacts from space. As small pieces of rock and ice come hurtling toward our planet, they are heated by air friction, producing shooting stars. Analysis of meteorite strikes on the Moon suggest meteors three feet across or greater may encounter our planet ten times more often than previously believed.
A meteor which exploded above Chelyabinsk, Russia last year was 65 feet across, and the blast was equivalent to 30 Hiroshima bombs. The resulting shock waves injured over 1,100 people.
Data from the celestial impact was published in the journal Monthly Notices of the Royal Astronomical Society.