Astronomers Catch Bright Explosion On The Moon

Lawrence LeBlond for redOrbit.com – Your Universe Online

If you take a good look at the Moon it isn’t too difficult to paint a pretty clear picture of the lunar surface’s violent past. Our neighboring natural satellite is pock-marked with thousands upon thousands of craters from meteors and asteroids that have been pelting its surface for more than a billion years.

Over the past eight years, NASA astronomers have been monitoring the Moon studying impact sites and also looking for new signs of impacts. And by keeping a close watch on the Moon, astronomers have come to the realization that “lunar meteor showers” are much more common that anyone had previously expected, with hundreds of impacts occurring every year.

Many of the impacts that occur have been easily detectable by astronomers with high-tech equipment, and some even by amateur astronomers with backyard telescopes. But one impact that recently occurred on the Moon was so bright that anyone looking up with a naked eye would have had the sighting of a lifetime – the biggest explosion on the moon in at least the past eight years that lunar monitoring has occurred.

“On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium,” said Bill Cooke of NASA’s Meteoroid Environment Office (MEO). “It exploded in a flash nearly 10 times as bright as anything we’ve ever seen before.”

Anyone looking at the Moon at the very moment of impact would have been able to see the explosion without the aid of a telescope. The flash, which lasted about a second, glowed like that of a 4th magnitude star.

The first person to detect the explosion was Ron Suggs, an analyst at Marshall Space Flight Center in Alabama. Suggs caught the anomaly while sifting through digital recordings made with one of the program’s 14-inch telescopes.

“It jumped right out at me, it was so bright,” recalled Suggs. The 90-pound meteoroid responsible for the explosion was traveling at about 56,000 mph when it made impact. The small chunk of rock exploded with the force of 5 tons of TNT when it made impact.

While the meteoroid itself was small, Cooke believes the object was part of a much larger group of cosmic travelers.

“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,” Cooke said in a statement. “These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt.”

Since the Earth and Moon would have been bombarded by the same debris field at the same time, Cooke said it is likely the two events are related, adding that “this constitutes a short duration cluster of material encountered by the Earth-Moon system.”

Because one of the goals of the lunar monitoring program involves identifying space debris that could pose a significant threat to the Earth-Moon system, astronomers have labeled the March 17th impact/explosion as a good candidate for their research.

To further study the site, astronomers contacted operators of NASA’s Lunar Reconnaissance Orbiter. The LRO should be able to get a good reading of the area on a future pass since it is believed the resulting crater is as wide as 65 feet. Comparing the crater size to the explosion brightness should give researchers some valuable data that go into lunar impact models.

Unlike Earth, the Moon has no atmosphere to protect it and the surface is exposed to all meteoric bombardments of any size. As a result, meteor impacts are much more frequent on the Moon.

Since NASA began tracking lunar meteors in 2005, more than 300 impacts have been detected, none of which were as bright as the March 17th event.

NASA said that most lunar impacts hail from known meteoroid streams such as the Perseids and Leonids. However, there are some rogue meteors that happen by that occasionally strike the Moon’s surface. Most of these are stray pieces of comets and/or asteroid debris.

Cooke said astronomers will be keeping an eye out next year around the same time to see if any repeat performances occur “when the Earth-Moon system passes through the same region of space.”

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