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Space Topics

Deep Impact


Deep impact will fly by comet 103P/Hartley on November 4. Read the encounter timeline and visit The Planetary Society Weblog for updates.
What are comets made of? Are they solid rocks, or fluffy snowballs? On July 4, 2005, the Deep Impact mission attempted to find out in a dramatic way. One part of the Deep Impact spacecraft slammed into comet Tempel 1, ending its life with a smash, while the flyby spacecraft watched the birth of a new crater. By studying the size and shape of the new crater, and the composition and motion of the stuff that flew away from the impact, the Deep Impact scientists hope to learn how comets are put together.

An extended mission for Deep Impact, called EPOXI, has now been approved. In the Deep Impact Extended Investigation (DIXI), it returned to Earth for a flyby in December 2007, and use Earth's gravity to change course to encounter another comet, Jupiter-family comet 103P/Hartley (also known as Hartley 2), on November 4, 2010. (A 2008 encounter with comet Boethin was initially planned but had to be abandoned because Boethin could not be found.) In the meantime, Deep Impact's instruments were used to perform followup studies of extrasolar planets in an investigation called EPOCh (Extrasolar Planet Observation and Characterization).

Movie of the Deep Impact into Tempel 1
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Credit: NASA / JPL-Caltech / UMD / Emily Lakdawalla
Deep Impact successfully accomplished the difficult engineering challenge of splitting into two spacecraft, one of which slammed to its destruction on the comet while the other watched. Instruments aboard both the flyby and impactor spacecraft recorded the spectacular effects. Tempel 1 had many surprises in store for the science team. The biggest surprise was the dustiness of the impact; Tempel 1's surface proved to be made of a dust so fine and so weakly held together that the spray of impact ejecta formed an impenetrable barrier to the flyby craft's camera, preventing a clear view of the crater that the impactor made. However, the shape, temperature, composition, and development of the stuff that was tossed out of the hidden crater have provided a lot of information about Tempel 1, and analysis continues. Tempel 1 will be visited by another spacecraft, Stardust, on February 14, 2011.

Deep Impact Facts
Launch date: January 12, 2005
Comet Tempel 1 flyby and impact: July 4, 2005
Comet Boethin encounter: planned for December 5, 2008
Comet Hartley 2 encounter: planned for November 4, 2010