Bright explosion on the Moon

May 17, 2013 by Dr. Tony Phillips
These false-color frames extracted from the original black and white video show the explosion in progress. At its peak, the flash was as bright as a 4th magnitude star.

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 in Mare Imbrium," says Bill Cooke of NASA's 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 explosion1 packed as much punch as 5 tons of TNT.

NASA's lunar monitoring program has detected hundreds of meteoroid impacts. The brightest, detected on March 17, 2013, in Mare Imbrium, is marked by the red square.

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 video is not supported by your browser at this time.

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.

This video is not supported by your browser at this time.

One of the goals of the lunar monitoring program is to identify new streams of 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."

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User comments : 17

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fmfbrestel
1 / 5 (4) May 17, 2013
Whatever happened to the idea of using a nuke at the earth-sun L3 point as a type of "sonar" to detect near earth asteroids? The sun would shield earth from any direct effects from the blast, and you look for reflections from the bast to identify asteroids.

technical problems, or just too much political pressure surrounding the launch of an explosive nuclear device into space?
cantdrive85
1 / 5 (7) May 17, 2013
Why is it in all those laboratory impact tests you never see a flash as what is observed here? Could it possibly be because there are other processes taking place rather than one inert rock slamming into another?
Jeddy_Mctedder
1.7 / 5 (7) May 17, 2013
I imagine the far side of the moon receives far more impacts than the near side by virtue of being more exposed towards the orbital paths of asteroids. The near side is playing peekaboo, hiding itself from asteroids by facing the earth.
Is this a reasonable assuption?
El_Nose
1 / 5 (1) May 17, 2013
FYI -- this explosion is one fifth the magnitude of the explosion of the West fertilizer plant in April.

the asteroid was about 1 foot wide -- wow

@Jeddy

while it is always facing away from earth -- the exposure of the moon is merely its gravity well --- from there the tradgetory of the object determines if it will hit the moon -- and where
Jeddy_Mctedder
2 / 5 (4) May 17, 2013
El nose. I get the gravity well but conceptually. A tidally locked orbitting body should have more surface facing tangentially to asteroid trajectories because most asteroids follow certain patterned trajectories Ànd the gravity lock skews as well.

Intuitively i look at the picture above and there are clear patterns of where asteroids strike and where they do not. If this sample size is reprenstative and blies a signal. ...its bscause there are reasons. Im suggesting my belief that such a pattern extends overrepresentation of strike frequency on the far side for a number of reasons of which i may be wrong about
RealScience
4 / 5 (4) May 17, 2013
@cantdrive - it is because in our laboratories we don't accelerate a 40 kg mass to 90,000 km/h before slamming it into a target.
However when we explode 5 tons of TNT (the same energy), it makes a good flash. And the meteor packs the energy into a much smaller volume and much less mass, and so reaches a higher temperature that produces light better even than 5 tons of TNT.

@Jeddy - it would not be the far side of the moon, but the leading edge of the moon in its orbit around the earth (which is in the same direction as the earths orbit around the sun). That edge sweeps out more space and so is hit more, and impacts average faster and thus brighter, too. However the moon's orbital velocity is only ~1 km/sec, which is only a few percent of the relative velocity of most impactors, so the effect is modest.
Silverhill
5 / 5 (1) May 17, 2013
@fmfbrestel
Whatever happened to the idea of using a nuke at the earth-sun L3 point as a type of "sonar" to detect near earth asteroids? The sun would shield earth from any direct effects from the blast, and you look for reflections from the bast to identify asteroids.

technical problems, or just too much political pressure surrounding the launch of an explosive nuclear device into space?
The latter. By treaty, no nation may launch nuclear explosives into space.
Sir Arthur Clarke described what you're asking about. (I don't know if he was the first to do so.) He proposed detonating a 1-gigaton bomb at the L3 point; the microwave-spectrum part of the flash would satisfactorily illuminate everything in the inner system that had a diameter of 1 meter or more. Radio telescopes would watch for the echoes.
(Actually, this would need to be done at least 3 times, since 3 fixes on an object are required in order to compute its orbital parameters.)
geokstr
2.3 / 5 (3) May 19, 2013
I remember stories of astronomers going all the way bank to the invention of the telescope being scoffed at for reporting bright flashes on the moon and at least one on Mars. Looks like they might not have been so crazy after all.
barakn
5 / 5 (4) May 21, 2013
Why is it in all those laboratory impact tests you never see a flash as what is observed here? Could it possibly be because there are other processes taking place rather than one inert rock slamming into another?

http://spaceinima...act_test
It's time once again for cantdrive85 to apologize for posting fallacious drivel.
cantdrive85
1 / 5 (5) May 21, 2013
Why is it in all those laboratory impact tests you never see a flash as what is observed here? Could it possibly be because there are other processes taking place rather than one inert rock slamming into another?

http://spaceinima...act_test
It's time once again for cantdrive85 to apologize for posting fallacious drivel.

When you show similar results of impacts into lunar type regolith, I'll admit I'm wrong. Until then, keep mining...
antialias_physorg
5 / 5 (1) May 21, 2013
He proposed detonating a 1-gigaton bomb at the L3 point

Apart from the treaty aspect: Why L3? What makes any point better for this idea than any other? (And somehow I can't really see a 1GT nuke lighting up all that much. You'd need enormously good telescopes to catch any reflections - and enormously good telescopes only have a very limited field of view, so you'd need a LOT of them.)

The sun puts out rather more light than a 1GT nuke and it doesn't seem to light up much of anything that is that small (at least not to the point where our telescopes can make out stuff that is smaller than 100m or so in diameter)
barakn
5 / 5 (3) May 21, 2013
Why is it in all those laboratory impact tests you never see a flash as what is observed here? Could it possibly be because there are other processes taking place rather than one inert rock slamming into another?

http://spaceinima...act_test
It's time once again for cantdrive85 to apologize for posting fallacious drivel.

When you show similar results of impacts into lunar type regolith, I'll admit I'm wrong. Until then, keep mining...

Of course someone like you would move the goalpost rather than admit a mistake.
barakn
5 / 5 (4) May 21, 2013

When you show similar results of impacts into lunar type regolith, I'll admit I'm wrong. Until then, keep mining...

http://ars.els-cd...-gr2.jpg not quite regolith, but it's sand. http://www.scienc...07002400 feature hypervelocity impacts into a variety of substances (perlite, powdered dolomite, graphite, sugar, pumice) with densities and textures similar to regolith. But you of course wish to avoid the obvious, so have demanded that destructive tests be performed on a substance that's worth millions of dollars an ounce. I'm sure the other readers recognize that you have made an unreasonable demand to protect your own insane theory.
cantdrive85
1 / 5 (6) May 21, 2013
Glad you brought up Deep Impact. The double flash impact, unexpected by NASA (however predicted by Wal Thornhill) and explained away with some ad hoc explanation of a "double impact". Not to mention the total surprise by the intensity of the explosion, nor the degree to which the impact site would be obscured by impact (both predicted by Thornhill). Yep, the actual application of NASA's theories was spot on, NOT! There were a number of other predictions by Thornhill that were confirmed, NASA was shocked and awed and in the words of a team scientist, "I'm at a loss to explain it."
barakn
5 / 5 (2) May 22, 2013
Yes, try changing the subject. No one will notice.
cantdrive85
1 / 5 (4) May 22, 2013
Refer to my original post;
Could it possibly be because there are other processes taking place rather than one inert rock slamming into another?

I am merely suggesting there is an electrical aspect as well, supported by the data .
Silverhill
5 / 5 (1) May 23, 2013
[Clarke] proposed detonating a 1-gigaton bomb at the L3 point
Apart from the treaty aspect: Why L3? What makes any point better for this idea than any other?
I don't actually remember it being L3 necessarily; just on the other side of the Sun from us, to avoid damage to our orbital equipment, and reasonably far from the Sun so that the solar disc would not shadow too many of the targets.

(And somehow I can't really see a 1GT nuke lighting up all that much. You'd need enormously good telescopes to catch any reflections - and enormously good telescopes only have a very limited field of view, so you'd need a LOT of them.)
I believe that a large number of observers was to be needed, yes.

The sun puts out rather more light than a 1GT nuke and it doesn't seem to light up much of anything that is that small
The illumination was to be via microwaves, which are not as great a part of the solar emission as is visible light.