spacetoday.net: Twin NASA spacecraft to crash into the Moon on Monday

Posted: Fri, Dec 14, 2012, 7:59 AM ET (1259 GMT)
GRAIL illustration (NASA)

Two NASA spacecraft that have been studying the Moon's gravitational field since the beginning of the year will end their mission by crashing into the lunar surface on Monday. The twin Gravity Recovery and Interior Laboratory (GRAIL) spacecraft, dubbed "Ebb" and "Flow", will crash into a mountain in the Moon's northern polar regions at 5:29 pm EST (2229 GMT) Monday, the two impacts taking place 20 seconds apart. The spacecraft are running low on propellant needed to maintain their orbits, and the controlled crash is to ensure that the spacecraft don't instead hit one of the "heritage" sites elsewhere on the Moon associated with Apollo and other past missions. The impact site will be in shadow at the time of the impacts and thus no visible phenomena are expected. The two spacecraft, which entered lunar orbit at the beginning of 2012, have provided scientists with the best map yet of the Moon's gravity field, which in turn has provided insights on the Moon's interior structure.