By Nadia Drake
Meteorites colliding with the moon sometimes set off tiny lights dancing across its surface. Now scientists think they know what powers these lunar lightbulbs, in the absence of any atmosphere that would otherwise set incoming meteors ablaze: The flashes result from superhot material kicked up by the tiny objects striking the moon’s surface.
“You have just a small piece of cometary material or asteroid, about 10 centimeters, that can do a very bright flash visible from the Earth,” says study coauthor Sylvain Bouley, a planetary scientist at the Paris Observatory.
The study, which will appear in March in Icarus, settles an old debate about where the twinkling lunar lights come from. Observed for more than half a millennium, lunar impacts occur hundreds of times each year. Meteor showers, like the Leonids in November, can dump as many as 20 objects on the moon in one night.
At first, scientists didn’t think the flashes necessarily came from the moon; they might have been reflections from tumbling satellites or some other kind of phenomenon. Then, debate revolved around whether impacts or something within the moon such as volcanism produced the transient flashes. Most recently, researchers couldn’t decide between hot, charged particles or liquid droplets kicked up by impacts as the culprit.