Asteroids and comets: Every year, millions of these "stray bullets" streak through the skies, and tons of small meteorites strike our planet. About 65 million years ago, it is assumed that dinosaurs were wiped off the face of the Earth - in what many think was the aftermath of a massive cosmic collision. Could something like this happen again? "Experts" believe that the impact of an asteroid only a mile wide would destroy many species, including humans. Join renowned geologist Eugene Shoemaker and his wife, Carolyn, who together have remapped the heavens with their discoveries of about 30 comets and hundreds of asteroids.