Asteroids and other large bodies from space have occasionally struck Earth, causing mass destruction and extinction. A. The large impactor that crashed in what is now the Arizona desert exploded with the force of a 20-megaton hydrogen bomb. B. Although the crash of a large impactor would have killed all living things near the site of impact, most animals living farther away adapted to changes in the environment. C. Scientists believe the reason the impactor that struck Earth 65 million years ago was so deadly was because it contained many toxic compounds, such as iridium. D. A worldwide sediment layer of iridium suggests that an asteroid or comet impacted Earth 65 million years ago, possibly causing the extinction of the dinosaurs. E. The large impact that caused the Yucatan crater probably produced both immediate natural disasters and a long-lasting layer of dust in the atmosphere. F. Despite the destructive effects of the large impact 65 million years ago, around 25 percent of Earth's species survived and mammals came to be dominant.