Sixty-five million years ago, a massive asteroid struck the Earth, triggering a series of catastrophic events that wiped out 70 percent of all species, including the dinosaurs. Scientists have pieced together the story of this great impact, which changed the course of evolution and led directly to the emergence of mammals and eventually humans. By analyzing geological evidence and using modern technology to simulate the impact, researchers have gained a detailed understanding of how this ancient event unfolded and its devastating consequences for life on Earth.