Moon hit by boulder-size meteoroid, causing 'explosion' visible from Earth
If you had been looking up at the moon at the right moment on March 17, you could have seen an unusual flash of light 鈥� a one-second burst of heat caused by the impact of a large meteoroid.
No telescope required.
鈥淔or about one second, the impact site was glowing like a 4th magnitude star,鈥� NASA said in reporting the news Friday.
This meteoroid was the size of a small boulder, and was travelling very fast. NASA estimates the size at 0.3 to 0.4 meters wide, and the speed at 56,000 miles per hour.听
The resulting explosion听 delivered a force equal to 5 tons of TNT.
NASA puts a footnote on the word 鈥渆xplosion.鈥� The bright light wasn鈥檛 combustion, since the moon has no oxygen atmosphere. Rather, it was the glow of molten rock and hot vapors after an impact of large kinetic force.
That said, this was the biggest such 鈥渆xplosion鈥� in eight years of close monitoring of the moon鈥檚 surface.
And it鈥檚 not that meteoroids on the lunar surface are rare.
The moon lacks a protective atmosphere like Earth鈥檚, in which meteoroids typically burn up. Lunar meteor showers have turned out to be more common than expected, with hundreds of detectable impacts per year.
On March 17, the pyrotechnics on the moon coincided with an active night for meteors in Earth鈥檚 atmosphere as well.
NASA鈥檚 Space Exploration Policy eventually calls for extended astronaut stays on the moon, so tracking meteor activity has long-term relevance.
鈥淚dentifying the sources of lunar meteors and measuring their impact rates gives future lunar explorers an idea of what to expect,鈥� the space agency said in announcing the bright explosion Friday. 鈥淚s it safe to go on a moonwalk, or not?听 The middle of March might be a good time to stay inside.鈥澨�
