Mr. EICHER: We can't really understand the solar system and how it got going unless we can really understand the origins and the conditions that happened when the solar nebula, this cloud of gas and dust, contracted down and the star turned on and the planets got going.

NPR: NASA 'Deep Impact' Probe Targets Comet

By observing the cloud of dust and gas kicked up by each impact, scientists knew they could obtain valuable data about the Moon's composition.

BBC: Nasa reveals new information about moon probes crash sites