Back in September of 2013, something truly amazing happened on the surface of the Moon. Granted, small objects impact with Earth’s only satellite all the time, hence its cratered surface. But this time around, Earth-based instruments observed an impact that was caused by an object the size of a small car, ten times bigger than any previously-recorded impacts.
The burst occurred on Sept. 11, 2013, at about 20:07 GMT in a area on the moon known as Mare Nubium, producing a flash that would have been visible from Earth. It was caused by a meteor that is believed to measure between 0.6- and 1.4-meters wide, weighed some 400 kg (880 pounds) and generated a crater with a diameter of about 40 meters.
Judging from the explosion and the crater it left behind, scientists estimate that the rock hit Mare Nubium at a speed of 61,000 kph (38,000 mph), generating an explosion equivalent to roughly 15 tons of TNT. This beats the previous record, which occurred in March 2013 when a 40 kg meteoroid 0.3 or 0.4 meters wide struck the moon at about 90,000 km/hr (56,000 mph) and caused an explosion equivalent to 5 tons of TNT.
These findings appeared in the February issue of Monthly Notices of the Royal Astronomical Society (MNRAS), in a paper entitled “A large lunar impact blast on 2013 September 11”. According to the paper’s authors – Jose M. Madiedo, from the University of Huelva and Jose L. Ortiz, from the Institute of Astrophysics of Andalusia – the impact was the longest and brightest impact ever observed, as the “afterglow” remained visible for 8 seconds.
Our telescopes will continue observing the Moon as our meteor cameras monitor the Earth’s atmosphere. In this way we expect to identify clusters of rocks that could give rise to common impact events on both planetary bodies. We also want to find out where the impacting bodies come from.
Knowing how often such collisions happen on the moon could be important for future lunar explorers, one reason why NASA has set up a specific program – Lunar Impacts, working out of the Marshall Space Flight Center – to study them. This campaign started in 2005 and has already proved that lunar impacts happen about 10 times more frequently than scientists previously expected.
Because the moon is our next-door neighbor, and a place where human beings may someday live in large numbers, knowing the frequency and severity of meteoric impacts is certainly important. These latest findings also suggests that the Earth might get hit more often than we previously thought by objects of a similar size. And given the damage associated with such impacts, knowing all we can is certainly prudent.
In the meantime, check out this outreach video provided by J.M. Madiedo (co-author of the MNRAS paper) that discusses this record-breaking lunar impact: