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Deep Impact Science Highlights

Originally built to conduct a mission to one comet, under the guidance of the University of Maryland science team the Deep Impact spacecraft ended up gathering information from four different comets, Earth and the Moon. In the process it provided insights into the forces that created comets 4.5 billion years ago and drive them today, and into the origin of our solar system.

  • Deep Impact’s intentional collision with Tempel 1 on July 4, 2005 provided the first hard information about the nucleus, or solid body of a comet. The collision revealed that Tempel 1 was surprisingly fluffy – like a bank of powder snow, consisting of 75 percent to 80 percent empty space, which insulated the interior from the comet’s surface heat.
  • The Tempel 1 encounter produced the first finding of water ice on the surface of a comet, and the first observations of natural impact craters on a comet, layers of material in the nucleus, flows, and other surprising features. Based on these observations and related findings, scientists now think many comets’ nuclei formed gradually, rather than in violent collisions as previously believed. 
  • In a 2007 flyby en route to a new mission, Deep Impact created video of Earth as seen from 31 million miles away. The video helped scientists know what to look for as they search for faraway Earth-like planets orbiting other stars.
  • Deep Impact proved there is water on the surface of the Moon. Deep Impact’s scientists found a thin layer of water molecules forms on the lunar surface and then dissipates each day. The discovery, confirming observations by the Chandrayaan-1 spacecraft and the Cassini space probe, was made on the fly as Deep Impact passed the Moon in 2007 and 2009.
  • As its two telescopic cameras captured spectacular images of jets of material shooting from the surface of comet Hartley 2 in October 2010, Deep Impact revealed that dry ice, or carbon dioxide gas, is the jet fuel for that comet, and perhaps for other hyperactive comets. Scientists previously thought water vapor powered the jets of dust and gas coming off the nuclei of comets.
  • Observations of comet Garrad in 2012 showed a remarkably high abundance of carbon asartmonoxide, making this comet different than others studied. This puzzling find may be explained through future observations of more comets.
  • Taken together, Deep Impact’s missions revealed that comets’ nuclei can be very different from one another. Scientists were inspired to rethink their ideas of where and how comets formed. They now think a group of comets that orbit the Sun every 20 years or less probably formed relatively close to Earth, and may be a source of our planet’s water.
  • Deep Impact’s instruments made the first systematic observations of newly discovered comet ISON, a sungrazer comet making its first approach to the Sun in December 2013.  Loss of contact with the spacecraft prevented the science team from gathering valuable data as ISON approaches the Sun.
  • The historic moment when Deep Impact’s refrigerator-sized impact craft collided with Tempel 1 made headlines worldwide, with more than a billion hits on the mission website. By boosting public enthusiasm for unmanned spacecraft exploration, Deep Impact has undoubtedly inspired a new generation of astronomers and astrophysicists.