Gene Shoemaker (1928-1997) founded a new branch of planetary science that her termed "astrogeology," which revolutionized our understanding of the solar system and the process of planetary evolution. He was the first to produce conclusive evidence that planet Earth had been bombarded by asteroids throughout its formative history, and that there was a very real likelihood of such an event occurring in the future.

Any doubt that this might be another brand of doomsday speculation vanished in 1994, when people worldwide watched such a cosmic spectacle from the safety of their homes and offices. Television stations broadcast live footage as Comet Shoemaker-Levy 9 torpedoed into the giant planet Jupiter in an incendiary hail of 21 fragments. The largest of these, dubbed "fragment G" struck Jupiter with a force equivalent to six trillion tons of TNT, or about 600 times the entire estimated nuclear arsenal of the world. The impact produced a fireball...