Washington: Spanish astronomers have said that a meteorite with the mass of a small car had crashed into the Moon last September.
The impact, the biggest seen to date, produced a bright flash and would have been easy to spot from the Earth.
On 11 September 2013, Prof. Jose M. Madiedo was operating two telescopes in the south of Spain that were searching for these impact events.
At 2007 GMT he witnessed an unusually long and bright flash in Mare Nubium, an ancient lava-filled basin with a darker appearance than its surroundings.
The flash was the result of a rock crashing into the lunar surface and was briefly almost as bright as the familiar Pole Star.
The September event is the longest and brightest confirmed impact flash ever observed on the Moon. Prof. Madiedo recalls how impressed he was: "At that moment I realized that I had seen a very rare and extraordinary event."
Prof. Madiedo and Dr. Jose L. Ortiz, from the Institute of Astrophysics of Andalusia (IAA-CSIC), think that the flash was produced by an impactor of around 400 kg with a width of between 0.6 and 1.4 meters. The rock hit Mare Nubium at about 61,000 kilometers per hour and created a new crater with a diameter of around 40 meters. The impact energy was equivalent to an explosion of roughly 15 tons of TNT, at least three times higher than the largest previously seen event observed by NASA in March last year.
The research has been published in the journal Monthly Notices of the Royal Astronomical Society.