Launched on a clear winter day in January 2005, NASA's Deep Impact spacecraft spanned 268 million miles (431 million kilometers) of deep space in 172 days, then reached out and touched comet Tempel 1.

NASA has placed a copper probe in the path of the comet called Tempel 1. Scientists await a collision that could produce a crater in the comet the size of a football stadium. But first, they have to ...