On July 4, 2005, NASA'S Deep Impact arrived at Comet Tempel 1. The goals behind the $333-million mission were to observe how the crater forms; to measure the crater's depth and diameter; to measure the composition of the interior of the crater and its eject and to determine the changes in natural out gassing produced by the impact. Deep Impact was the first space mission to break the surface of a comet. Read more about the mission.
