NASA's Deep Impact spacecraft lived up to its name when it slammed into a comet with such force that the resulting blast of icy debris stunned scientists with its size and brightness. With the flyby stage of the two-part spacecraft watching from a safe distance, an 820-pound, copper-core "impactor' craft smashed into the nucleus of comet Tempel 1 at 23,000 miles per hour, sending a huge, bright spray of debris into space. "The impact was spectacular,' said Dr Michael A'Hearn of the University of Maryland, the project's principal scientist. "It was much brighter than I expected.'