Comet Tempel 1 strikes the Deep Impact probe, July 4, 2005. A trailing craft photographed the collision.
On the 4th of July, NASA successfully arranged for a probe to get in the way of a comet. The collision produced a huge cloud of debris and reams of data for scientists to study. They now know more about the makeup of comets.
But one office pool among the scientists remains unresolved: What did the resulting crater look like?