Crashing into the Moon for science

During the Apollo missions, astronauts detonated a few small explosions. Lunar researchers weren’t sure at the time whether the Moon had moonquakes. So, astronauts brought sensing equipment to listen to the Moon’s potential rumbles. Listening to reverberations in the Moon’s outer layers can tell scientists a lot about what those layers are made of. So astronauts set off test shakes thanks to small explosives. It turns out, the Moon does have small quakes on its own, but both real and induced tremors taught researchers about the Moon’s hidden depths.

Humans largely left the Moon alone for a few decades after that. But in 2008, India launched its first lunar probe, Chandrayaan-1, which successfully reached lunar orbit. Once there, it released a small impactor, the polite research term for an artificial meteoroid they slammed into the Moon’s surface. It kicked up a plume of lunar dust, allowing its partner spacecraft still in orbit to investigate the cloud for signs of water.

Not to be outdone in explosions, NASA sent up the LCROSS mission the following year. LCROSS sent its depleted rocket stage plummeting into the Moon’s surface, studied the resulting larger plume with a shepherding spacecraft, and then crashed that spacecraft into the Moon as well for good measure, monitoring the entire process from above.

This series of impacts taught researchers about water on the Moon, which future Moon bases will have to rely on. habitability. Also, neither mission littered the Moon with radioactive debris, unlike, say, a nuclear weapon.