Explosive asteroids with diameters of 100 feet or more are believed to strike the Earth about every 30 years, with impacts equal to the energy released by hydrogen bombs. Many scientists believe that even larger asteroids, as wide as five miles, produced geological and climatological changes that led to the extinction of the dinosaurs and other species. Is the Earth due for another such collision? This new addition to general science collections explores the subject of asteroids: what they are, where they came from, and how their collisions with the Earth have affected life on our planet. Jon Erickson discusses scientific methods for detecting asteroid impacts and records the many known examples of asteroid collision and potentially devastating near misses that have occurred since prehistoric times. Readers also learn what scientists are doing to protect the Earth from wayward asteroids, as well as how asteroids could be mined or used as outposts for space exploration.