Fact Sheet
Fanning Out
A "spray" of gas erupts from Comet Tempel 1 in this recent image from Hubble Space Telescope. Planetary scientists are hoping for an even bigger eruption in the wee hours of July 4, when an instrumented probe slams into the comet's surface. The probe is part of the Deep Impact mission. The mission is designed to learn more about the comet's original composition by blasting a deep crater in its surface and looking at material at the bottom of the crater. This mixture of ice and rock should reflect the composition of the cloud of material that gave birth to the Sun and its planets, including Earth, four and a half billion years ago. The probe will transmit its readings to a mothership that will fly several thousand miles from the comet. This craft will take its own photographs and other measurements of the impact and its aftermath. Telescopes on the ground and in orbit around Earth will also observe the impact. [NASA/ESA/P. Feldman (JHU)/H. Weaver (JHU/APL)]
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