The Earth has suffered thousands of violent collisions with asteroids and comets over the last four billion years. The scars from these collisions are impact craters. But the Earth hides its wounds well -- less than two hundred impact craters have been discovered. Many are buried deep below the surface. They were only found by accident during geological surveys that were part of the massive, ongoing effort to find oil for an energy-dependent world. If Russian theories about the non-biological origin of much of our oil prove to be accurate, then there may be good reasons for oil prospectors to...