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  • Bright Explosion on the Moon - presented by Science@NASA

  • For the past 8 years,

  • NASA astronomers have been monitoring the Moon for signs of explosions

  • caused by meteoroids hitting the lunar surface.

  • 'Lunar meteor showers'

  • have turned out to be more common than anyone expected,

  • with hundreds of detectable impacts occurring every year.

  • They've just seen the biggest explosion in the history of the program.

  • 'On March 17, 2013,

  • an object about the size of a small boulder

  • hit the lunar surface in Mare Imbrium,'

  • says Bill Cooke of NASA's Meteoroid Environment Office.

  • 'It exploded in a flash

  • nearly 10 times as bright as anything we've ever seen before.'

  • Anyone looking at the Moon at the moment of impact

  • could have seen the explosion--no telescope required.

  • For about one second,

  • the impact site was glowing like a 4th magnitude star.

  • Ron Suggs, an analyst at the Marshall Space Flight Center,

  • was the first to notice the impact in a digital video

  • recorded by one of the monitoring program's 14-inch telescopes.

  • 'It jumped right out at me,

  • it was so bright,' he recalls.

  • The 40 kg meteoroid,

  • measuring 0.3 to 0.4 meters wide,

  • hit the Moon traveling 56,000 mph.

  • The resulting explosion packed as much punch as 5 tons of TNT.

  • Cooke believes the lunar impact

  • might have been part of a much larger event.

  • 'On the night of March 17,

  • NASA and University of Western Ontario all-sky cameras

  • picked up an unusual number of deep-penetrating meteors

  • right here on Earth,' he says.

  • 'These fireballs were traveling along nearly identical orbits

  • between Earth and the asteroid belt.'

  • This means Earth and the Moon were pelted by meteoroids

  • at about the same time.

  • 'My working hypothesis is that the two events are related,

  • and that this constitutes a short duration cluster

  • of material encountered by the Earth-Moon system,' says Cooke.

  • One of the goals of the lunar monitoring program

  • is to identify new streams of space debris

  • that pose a potential threat to the Earth-Moon system.

  • The March 17th event seems to be a good candidate.

  • Controllers of NASA's Lunar Reconnaissance Orbiter

  • have been notified of the strike.

  • The crater could be as wide as 20 meters,

  • which would make it an easy target for LRO

  • the next time the spacecraft passes over the impact site.

  • Comparing the size of the crater to the brightness of the flash

  • would give researchers a valuable 'ground truth' measurement

  • to validate lunar impact models.

  • Unlike Earth,

  • which has an atmosphere to protect it,

  • the Moon is airless and exposed.

  • 'Lunar meteors' crash into the ground with fair frequency.

  • Since the monitoring program began in 2005,

  • NASA's lunar impact team has detected more than 300 strikes,

  • most orders of magnitude fainter than the March 17th event.

  • Statistically speaking,

  • more than half of all lunar meteors come from known meteoroid streams

  • such as the Perseids and Leonids.

  • The rest are sporadic meteors--

  • random bits of comet and asteroid debris of unknown parentage.

  • U.S. Space Exploration Policy

  • eventually calls for extended astronaut stays on the lunar surface.

  • Identifying the sources of lunar meteors

  • and measuring their impact rates

  • gives future lunar explorers an idea of what to expect.

  • Is it safe to go on a moonwalk, or not?

  • The middle of March might be a good time to stay inside.

  • 'We'll be keeping an eye out

  • for signs of a repeat performance next year

  • when the Earth-Moon system passes through the same region of space,' says Cooke.

  • 'Meanwhile, our analysis of the March 17th event continues.'

  • For updates about explosions on the Moon

  • - and elsewhere in the cosmos -

  • stay tuned to

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サイエンスキャスト月面での明るい爆発 (ScienceCasts: Bright Explosion on the Moon)

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