The purpose of NASA's Deep Impact mission was to probe below the surface of the comet Tempel 1 and learn more about its composition. This data provided scientists with information about the formation of the solar system as well as clues about how Earth's oceans may have formed. Deep Impact was the first mission to successfully study the interior of a comet.
Deep Impact reached Tempel 1 on July 4, 2005, and its mission ended on Sept. 20, 2013. The spacecraft was lost due to a software glitch in its fault protection software which rendered it inoperable by causing the computer to continually reboot. Before this failure, Deep Impact completed its mission to Tempel 1 and went on to survey two other comets: Hartley 2 and ISON. Its close up photographs of these comets provided an unprecedented look at their physical structure.
The spacecraft also performed a successful secondary mission of searching for planets in other solar systems; data returned by Deep Impact was used to confirm the existence of hundreds of planets and discover thousands of potential planet candidates. Additionally, Deep Impact's observations of Earth provided supporting evidence that methods used to detect liquids on Saturn's moon, Titan, were accurate.