A meter-wide (3 ft) asteroid impacted the Moon's surface September 11, 2013, producing a bright explosion and digging a new crater about 40 meters (130 ft) in diameter. The video of the event shows a bright flash of light against the stark blackness of the Moon's dark side. Similar in brilliance to the brightest stars in the Big Dipper, the asteroid impact is the largest confirmed impact on the Moon since continuous monitoring started some 15 years ago.
The asteroid impact was recorded by the MIDAS (Moon Impacts Detection and Analysis System) lunar impact monitoring study, being carried out by Professor Jose Madiedo's team at the University of Huelva in Spain.
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Hundreds of lunar impacts have been recorded using video cameras gazing through amateur-class telescopes since the process began in the late 1990s, adding substance to centuries of visual observations of so-called transient lunar phenomena. Most impacts, however, were at the threshold of detection with these instruments.
For convenience, the number of video frames on which an impact event could be seen established a rough field criterion for describing its intensity. Most events are visible for a few frames, and about once a year an impact can be seen for 10-20 frames. In contrast, the September 11 impact was visible for a full eight seconds at normal video rates, indicating that it was by far the most energetic impact seen in this study.
Working out the numbers reveals that the asteroid had a mass of about 400 kg (880 lb), and was roughly a meter (3.3 ft) in size. Traveling at 17 km/s (10.5 miles-per-second), it struck the Moon's surface at 20:07 GMT. The impact is estimated to have released about 60 billion joules (17,000 kWh), the equivalent of about 15 tons of TNT.
The study has been published in the Monthly Notices of the Royal Astronomical Society. The video below is from Prof. Madiedo, and gives an idea of the magnitude of this event.
Source: Royal Astronomical Society