The Effort

"When dark comet UD3 was spotted near Jupiter's orbit, its existence was largely ignored. But to individuals who knew better -- scientists like Benjamin Schwartz, manager of NASA's Center for Near-Earth Object Studies -- the threat this eight-kilometer comet posed to the survival of the human race was unthinkable. The 150-million-year reign of the dinosaurs ended when an asteroid impact generated more than a billion times the energy of an atomic...