NASA Crashes Two Probes into a Mountain on the Moon

A pair of NASA moon-mapping probes smashed themselves into a lunar mountain on Monday, ending a year-long mission that is shedding light on how the solar system formed.

The Gravity Recovery and Interior Laboratory, or GRAIL, spacecraft had been flying around the moon, enabling scientists to make detailed gravity maps. The probes sped up slightly as they encountered stronger gravity from denser regions and slowed down as they flew over less-dense areas.

By precisely measuring the distance between the two probes, scientists discovered that the moon's crust is thinner than expected and that the impacts that battered its surface did even more damage underground.