Moving serenely through space some 130 million kilometers from Earth, Comet Tempel 1 appears no different than it did before July 4, the day a NASA spacecraft called Deep Impact fired a 372-kilogram copper projectile into the comet's icy surface. But if the impact left barely a dent in this 9-kilometer-long, fist-shaped body, the data collected from the collision have made an indelible mark on studies of comets and the formation of the solar system.
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