NASA Grail Twin Probes Final Flight Path

The NASA GRAIL twin probes' final flight path into their crash site, imaged with data from NASA's Lunar Reconnaissance Orbiter (LRO). 

Credit: NASA/JPL-Caltech/GSFC/ASU

Two space probes that successfully mapped variations in the Moon's gravity field have been deliberately crashed into the lunar surface in a dramatic end to their mission.

They are just the latest in a string of probes to leave their shattered remains on the Moon. The impacts of the GRAIL probes, Ebb and Flow, into a 2.4 km high (1.5 miles) mountain near the lunar north pole, was deliberate and planned in great detail.

NASA decided to destroy the craft in a controlled manoeuvre rather than take the risk, however tiny, that they might later hit one of the historic landing sites of Apollo and unmanned probes.

The two spacecraft, each the size of a washing machine, fired their thrusters one last time to burn up the last of their fuel. They dropped into a lower orbit and hit the peak's southern face, near a crater called Goldschmidt, at 6,050 kph (3,760 mph).