Lunar Impact

An image of the flash resulting from the impact of a large meteorite on the lunar surface on 11 September 2013, obtained with the MIDAS observatory. Credit: J. Madiedo / MIDAS

A meteorite with about the mass of a small car impacted the moon last September and it was seen by Spanish astronomers. I don’t often mention Spanish astronomers, more the pity and bad on me. Spain has some of the best observers and astronomers as there are anywhere.

In this case 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 UTC he witnessed an unusually long and bright flash in Mare Nubium, an ancient lava-filled basin with a darker appearance than its surroundings.

We are hearing about this now because the scientists involved published their description of the event in the journal Monthly Notices of the Royal Astronomical Society.  By the way, video links are included below the fold.

The Spanish telescopes are part of the Moon Impacts Detection and Analysis System (MIDAS) system that monitors the lunar surface. This project is being undertaken by Prof. Jose Maria Madiedo, from the University of Huelva (UHU), and by Dr. Jose L. Ortiz, from the Institute of Astrophysics of Andalusia (IAA-CSIC) and continues a pioneering program that detected sporadic lunar impact flashes for the first time.

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 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.

“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.”

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

There are a couple of videos of the impact:

The first and shortest (my favorite of the pair) is here. Watch the timer tick off after impact.

The second, longer video comes with more of an explanation is here.

One thought on “Lunar Impact

  1. 15 tons on TNT? I calculate 27 tons on TNT:

    E=M*(v*v) i.e. Energy = Mass times Velocity-square
    Energy in Joule, Mass in kg, Velocity in m/s
    3.6 km/h=1m/s

    v=61000 / 3.6 = 16944 m/s
    E = 400 * 16944 * 16944
    E = 114839654400 Joules
    E = 27 tons on TNT (www.wolframalpha.com)
    ?

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