How do we know an asteroid hit Earth 66 million years ago?

One theory for why the dinosaurs went extinct is that an asteroid hit Earth at the end of the Cretaceous period. But since no one was alive to see it, how can we know that it really happened? Astrophysicist Jackie Faherty reveals how clues found in sedimentary rock and on the ocean floor have helped scientists piece together this millennia-old mystery.

If you want to learn more about the effect an asteroid impact would have had on life on Earth during the Cretaceous, watch this week’s Dinosaur video.