By Deborah Netburn
9:00 AM EDT, May 18, 2013
The biggest explosion ever recorded on the moon was caused by a space rock roughly the size of a beach ball.
It weighed 80 pounds and was just over 1 foot wide, but it was going incredibly fast, traveling through space at speeds of 56,000 mph.
And when it collided with the moon, it exploded with the force of 5 tons of TNT, sending off a flash of light bright enough to see from here on Earth.
It was the largest explosion that scientists monitoring lunar impacts had ever witnessed, and it likely made a 65-foot wide hole in the already pock marked lunar surface.
The explosion took place on the dark side of the moon on March 17. This week, scientists at NASA's Marshall Space Flight Center released video of the explosion recorded through 14-inch telescopes trained at the moon. (See below.)
If a meteoroid of a similar size going just as fast had hit the Earth, it would probably have burned up in our atmosphere, creating an impressive fireball in the sky, but nothing more dramatic than that. But the moon has no atmosphere to protect it, so whatever gets hurled at it hits it.
The flash of light was created by the kinetic energy built up by the impact of a rock moving faster than a speeding bullet, and three times as fast as a space craft going into Earth orbit, said Rob Suggs, who manages the lunar impact monitoring activity at NASA's Marshall Space Flight Center.
"The kinetic energy has to go somewhere," he said. "Some of it comes out as light, some of it went into making a crater, and some of it made a seismic thump on the moon. It also caused a lot of heat."
Suggs said you would have had to have been watching the moon pretty closely to see the flash of light created by the impact from Earth. It was visible for just a fraction of a second.
"If you were looking through a telescope no doubt you would have noticed it, but even a really keen- eyed observer without a telescope might not be sure they saw anything because it was so quick," he said.
Scientists still don't know where the 80-pound space rock came from, but they think it might have been part of a larger space debris event. On the same night, NASA and University of Western Ontario all-sky cameras saw an unusual number of deep penetrating meteors here on Earth, Bill Cooke of NASA's meteoroid environment office explained in a statement.
"These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt," Cooke said. "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."
Scientists will be watching to see if the Earth and moon pass through another cluster of space rocks next March.
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