Thirteen Seconds After Impact . ... Maryland , JPL-Caltech , NASA Explanation: Fireworks came early on July 4th when, at 1:52am EDT, the Deep Impact spacecraft's probe smashed into the surface of Comet Tempel 1's nucleus at ten kilometers per second . ... Tempel 1's potato-shaped nucleus is approximately 5 kilometers across as seen from this perspective. Camera's onboard the impactor probe were also able to image the nucleus and impact site up-close ... until about 3 seconds before the impact. ...