July 4th 2005 a small copper impactor from the NASA Deep Impact spacecraft was released in the path of Comet Tempel 1, causing a collision that released fresh ice and dust, allowing astronomers for the first time to study pristine material from the formation of our solar system. Sir Patrick Moore is joined by leading comet experts who describe the science and importance of this historic achievement. While co-host Chris Lintott interviews British astronomer Richard Ellis at Palomar Mountain, California who is in charge of the observatory where professional astronomers using the historic Hale 200-inch telescope, and a team of amateur astronomers including Scott Roberts, Tony Cook, Russ and Stephanie Tanton, Dan Dickerson, John Downs, Mike West, and others who visually and photographically witnessed the actual point of impact.