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How Big Was the Asteroid That Contributed to Dinosaur Extinction?
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Illustration showing a massive asteroid above a city map with a dinosaur silhouette for scale, highlighting the asteroid's size compared to major urban areas.
Map of the northern Yucatan Peninsula in Mexico highlighting the location and circular outline of the Chicxulub crater, which is about 180 kilometers in diameter and partly extends into the Gulf of Mexico. The map also shows nearby cities such as Merida, Cancun, Campeche, and Playa del Carmen, as well as international borders with Belize and Guatemala. An inset globe marks the region's location in the Americas.
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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
•History
Illustration showing a massive asteroid above a city map with a dinosaur silhouette for scale, highlighting the asteroid's size compared to major urban areas.
How Big Was the Asteroid That Killed the Dinosaurs?This rock would take out more than just a T. rex.
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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.

How do we know about the asteroid?

Not the (Sole) Culprit?

Not all scientists agree that the Chicxulub asteroid killed all dinosaurs. Terrestrial factors such as extreme climate change, the rise of animals that ate dinosaur eggs, and even radiation from an exploding supernova close to the solar system may have whittled away at the dinosaurs’ habitats over time. The impact at Chicxulub may or may not have contributed to these factors, and there may also have been other asteroids that crashed into Earth and eventually led to the extinction, such as the one that made the Nadir crater off the western coast of Africa.

The impact occurred near what is now the Yucatán Peninsula in Mexico and left behind the Chicxulub crater, named after the nearby town of Chicxulub Puerto. The crater is partly buried underwater, and its full extent is not visible, but surface formations that mirror the outline of the crater or arise from the altered flow of water around the crater’s edge affect the topography of the region. Anomalies in the minerals found between layers of rock and soil through drilling samples also helped determine the shape and size of the crater. These studies tell us that the crater measures roughly 180 kilometers (112 miles) across, making it one of the largest known impact structures on Earth.

Using the contours of the crater revealed through this analysis, researchers ran impact-scaling simulations—computer models that use the size and shape of an impact crater to estimate the energy, speed, and effects of the collision—to determine that the asteroid struck Earth at roughly 64,000 kilometers (40,000 miles) per hour. Comparing this information with data on known asteroids and comets in the solar system allowed experts to estimate the size of the asteroid.

Map of the northern Yucatan Peninsula in Mexico highlighting the location and circular outline of the Chicxulub crater, which is about 180 kilometers in diameter and partly extends into the Gulf of Mexico. The map also shows nearby cities such as Merida, Cancun, Campeche, and Playa del Carmen, as well as international borders with Belize and Guatemala. An inset globe marks the region's location in the Americas.
Map of Chicxulub crater on the Yucatán PeninsulaA detailed map highlighting the location and 180 km diameter of the Chicxulub impact crater on the northern Yucatán Peninsula, the site of the massive asteroid impact that wiped out the dinosaurs 66 million years ago.
Aman Kumar