NASA handout image of the GRAIL mission's twin spacecraft in orbit around the moon

 
NASA handout image of the GRAIL mission
NASA handout image shows an artist's concept of the Gravity Recovery and Interior Laboratory (GRAIL) mission's twin spacecraft in orbit around the moon. The GRAIL mission will fly the spacecraft, in the same orbit, over areas of greater and lesser gravity, caused both by visible features such as mountains and craters and by masses hidden beneath the lunar surface, they will move slightly toward and away from each other. The twin GRAIL spacecraft will make suicidal plunges December 17, 2012 into a mountain near the moon's north pole,after a successful year-long mission to learn what lies beneath the lunar surface, officials said on December 13. REUTERS/NASA/JPL/Handout