The Chicxulub asteroid An artist's rendering of the impact of a near-Earth object 66 million years ago in what is today the Caribbean region. Many scientists think that the collision of a large asteroid or comet nucleus with Earth triggered the mass extinction of dinosaurs and many other species near the end of the Cretaceous Period. (more) How Big Was the Asteroid That Contributed to Dinosaur Extinction? Written by Aman Kumar Aman Kumar is an editor at Encyclopaedia Britannica. Aman Kumar Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Jan. 29, 2026 •History Many scientists believe an asteroid that struck Earth 66 million years ago may have significantly contributed to the K–T extinction event, which wiped out the dinosaurs. Though little is known about the asteroid itself, it is estimated to have been about 10 to 15 km (6 to 9 miles) in diameter. The impact occurred near what is now the Yucatán Peninsula in Mexico and left behind the Chicxulub crater, named after the nearby town of...

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