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[Mongo]

Astronomers spot record-breaking lunar impact

A meteorite with the mass of a small car crashed into the Moon last September, according to Spanish astronomers. The impact, the biggest seen to date, produced a bright flash and would have been easy to spot from 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, meaning that anyone on Earth who was lucky enough to be looking at the Moon at that moment would have been able to see it. In the video recording made by Prof Madiedo, an afterglow remained visible for a further eight seconds.

The October 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 realised that I had seen a very rare and extraordinary event."

Prof Madiedo and Dr Ortiz think that the flash was produced by an impactor of around 400 kg with a width of between 0.6 and 1.4 metres. The rock hit Mare Nubium at about 61,000 kilometres per hour and created a new crater with a diameter of around 40 metres. 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.

Observing impacts on the Moon gives astronomers an insight into the risk of similar (but larger) objects hitting Earth. One of the conclusions of the Spanish team is that these one metre sized objects may strike our planet about ten times as often as scientist previously thought. Fortunately, Earth's atmosphere shields us from rocks as small as the one that hit Mare Nubium, but they can lead to spectacular 'fireball' meteors.

I was not sure if this should go here or in "Telescopic Observations", but this seemed a somewhat more topic-specific location.

[charborob]

This recent lunar impact led me to wondering: what are the probabilities of LROC actually photographing an impact. Given the rate of impacts on the Moon and the rate of mapping by LROC, I suppose the chances of catching an impact in the act (so to speak) could be calculated.

[djellison]

This recent lunar impact led me to wondering: what are the probabilities of LROC actually photographing an impact. Given the rate of impacts on the Moon and the rate of mapping by LROC, I suppose the chances of catching an impact in the act (so to speak) could be calculated.

Given that it's cameras all work in a push-broom fashion.....astonishingly low.
LROC NA's field of view is (very roughly) a 5,000m by 0.5m strip.
LROC WA - approx (the filters make this a bit fuzzy) 75,000 x 1,000 m strip.
That 75sqkm of LROC WA account for about 0.000002% of the lunar surface, and of course it isn't imaging 24/7.
So -take any statistical chance of a particular area having an impact, and then factor in the likelihood of LRO seing that area at that time....pretty close to zero.
PLUS....these impacts tend to be seen on the night side of moon.....when the cameras will rarely be turned on anyway.