On Dec. 17, 2012, NASA's GRAIL mission crashed into the moon.

GRAIL stands for Gravity Recovery And Interior Laboratory, and the mission consisted of two twin spacecraft named Ebb and Flow that are about the size of a washer and dryer. They orbited the moon in tandem to map the moon's gravity field.The mission lasted about nine months, and they even completed an extended mission before the spacecraft began to run low on fuel, so NASA decided it was time to power them down. Both spacecraft bit the lunar dust pretty violently, falling faster than 3,700 miles per hour.