Goals: Deep Impact's primary mission was to deliver a special impactor spacecraft into the path of Comet Tempel 1.

Accomplishments: The spacecraft -- and many ground-based observers -- observed the impact and the ejected material. Scientists were surprised the cloud was composed of a fine, powdery material, not the expected water, ice, and dirt. The spacecraft did find the first evidence of surface ice on the surface of a comet instead of just inside a comet.

The flyby spacecraft is now on an extended assignment, called EPOXI, to study and search for planets orbiting distant stars. It also is en route to observe a second comet, Hartley 2. The spacecraft makes its closest approach to Hartley 2 in 2010. Scientists are eager to compare the two comets.