Famous for its July 4, 2005 planned impact with comet Tempel 1 that generated a brilliant flash of light later discovered to be ice and dust debris ejecting from the fresh impact crater, the Deep Impact mission was the first attempt to peer beneath the surface of a comet.
Deep Impact, which released an impactor on comet Tempel 1 to expose materials on its surface, revealed a number of new findings about comets and their composition, including evidence of water ice and organic materials. Researchers now believe that comets may have transported these compounds to Earth at one time, playing an essential role in the formation of the solar system and life on Earth.
July 2005: Data from Deep Impact shows that a cloud of fine powdery material was released when the impactor slammed into the nucleus of comet Tempel 1.
September 2005: Researchers discover a number of surprising facts about comet Tempel 1 from the Deep Impact experiment: Tempel 1 has a very fluffy structure made up of a fine dust that is weaker than a bank of powder snow, but that's held together by gravity; what appear to be impact craters can be seen on the surface of the comet; a huge increase of carbon-containing materials were detected when analyzing the comet's ejection plume, indicating that comets contain a substantial amount of organic material and may have brought that material to Earth at one time; and the comet's interior is well shielded from solar heating, meaning that the ice and other material deep within the comet nucleus may be unchanged from the early days of the solar system.
September 2005: Astronomers, using data from NASA's Sptizer Space Telescope and Deep Impact, come up with a list of compounds thought to be the recipe for planets, comets and other bodies in the solar system. Included are silicates, or sand, clay, carbonates, iron-bearing compounds and even aromatic hydrocarbons.
February 2006: The Deep Impact team discovers water ice on comet Tempel 1.