NASA Crashes Twin Probes Into the Moon
NASA concluded its Gravity Recovery and Interior Laboratory (GRAIL) moon mission by crashing two probes into the lunar surface — on purpose. The goal of the mission is to map the moon’s gravitational field. To do this, NASA launched two washing-machine-size probes to orbit the moon in September 2011. After both craft achieved orbit, they traveled around the moon in highly synchronized patterns at 3,600 miles per hour. The probes, named Ebb and Flow by elementary school students in Montana, could detect changes in the distance between one another down to a tenth of a micron — or half a strand of human hair. Their measurements have allowed scientists to create the highest quality gravitational field map of any celestial body, including Earth.