[jmcenanly]

It was the end of the mission for the orbiting space craft, so they figured they'd end the mission on a 'bang' (crash the craft into the Moon) and see what other interesting things they can discover about the lunar surface.
Actually our 'bomb' is the empty Centaur upper stage, which was going to the Moon any way as it had the same velocity as the LRO satellite, which is now orbiting the Moon.NASA built a smaller 'shepherd' space craft to follow the empty stage down to the Lunar surface.

[egannacht]

I heard that the USA is also doing some defense department tests with these “landings” which will figure in future technology.