The asteroid that wiped out the dinosaurs was about the size of Mount Everest—so where is it now?

The asteroid that wiped out the dinosaurs and struck Earth about 66 million years ago was enormous—about 12 kilometers wide. So where are its remains? (Photo: Sven Bachström, Alamy)

About 66 million years ago, the age of dinosaurs ended in a fiery twilight. An asteroid approximately 12 kilometers in diameter, traveling at 43,000 km/h, slammed into Earth. The impact triggered a cascade of deadly events that led to the fifth mass extinction, wiping out the dinosaurs, with the exception of some bird species.

But what happened to the Everest-sized asteroid?

When the asteroid hit Earth, “with an energy roughly 8 billion times greater than that of a World War II nuclear bomb, it essentially vaporized,” Sean Gulick, a research professor and co-director of the Center for the Habitability of Planetary Systems at the University of Texas at Austin, told Live Science. The asteroid turned into “fine dust that, once in the upper atmosphere, rained down” on the entire planet.

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For decades, asteroid dust fell, forming what is now known as the iridium anomaly—a thin layer of rock containing 80 times more iridium than anywhere else in Earth's crust, Gulick said. While iridium is highly concentrated in asteroids, it is virtually absent from Earth's outer crust—a key piece of evidence linking this 66-million-year-old layer to the asteroid that killed the dinosaurs.

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Perhaps the only known fragment of the asteroid is a sesame-seed-sized fragment found by Frank Kite, a geochemist at the University of California, Los Angeles. This fragment was discovered in a core drilled off the coast of Hawaii, as Kite reported in the journal Nature in 1998. Even smaller fragments were allegedly discovered in 2022, but this claim has not been peer-reviewed.

“We'd have to be very lucky to find a larger fragment,” Gulick said. But if we did, scientists could learn more about the “impact process” the asteroid itself experienced, and, for example, make even more accurate estimates of the pressures and temperatures it experienced.

The asteroid left behind a number of additional clues about its journey, including a massive crater formed when the giant rock collided with Earth. The Chicxulub crater, approximately 180 km wide and about 20 km deep, in what is now Mexico, bears a massive scar left by the asteroid. Named after the city located near the impact epicenter, the crater is covered in rocks and sediments that have shifted over tens of millions of years, and much of it is hidden beneath the waters of the Gulf of Mexico. However, an arc of sinkholes formed in the softened limestone along part of its rim is still visible from the surface.

The dark layer you see here is known as the iridium anomaly—a thin layer of rock that marks the end-Cretaceous extinction event and contains 80 times more iridium than anywhere else in the Earth's crust.

The impact also generated a tsunami nearly a mile high that traveled across the ocean, propelling water at speeds of 143 km/h (89 mph). The powerful waves left marks on the seafloor, called “megarripples,” as tall as five-story buildings, that remain deep beneath Louisiana. Seismic research has shown that the water that created these marks originated from the Chicxulub crater.

Beyond the deaths of unfortunate creatures in the immediate vicinity of the asteroid impact and the resulting tsunami, the asteroid's impact caused a number of other devastating effects, including deadly acid rain and a global firestorm. But perhaps most devastating was the massive debris cloud that enveloped Earth, dramatically cooling the planet, blocking sunlight and photosynthesis, and disrupting the food chain (though the duration of this “nuclear winter” is debated). The asteroid and its aftermath are generally believed to have caused the extinction of non-avian dinosaurs and ultimately wiped out approximately 75% of Earth's species.

The asteroid that wiped out the dinosaurs struck what is now Mexico, creating the Chicxulub crater, 10 miles (180 kilometers) wide and about 12 miles (20 kilometers) deep. RELATED SECRETS

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“The energy release was like an all-out nuclear war, repeated over and over again, 10,000 times,” said Alan Hildebrand, a planetary scientist and associate professor at the University of Calgary. Hildebrand co-authored the paper on the discovery of the Chicxulub crater in 1991, a work that provided crucial evidence linking the crater to the extinction of the dinosaurs.

For Hildebrand, it is not surprising that the asteroid destroyed most of life on Earth.

In Alberta, where he was during the interview, Hildebrand was struck by the incredible force of the impact. The closest layer from the Chicxiluba impact is 1 to 2 centimeters thick, “and this material was ejected here from the Yucatan Peninsula,” he said.

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Jesse Steinmetz, Live Science contributor

Jesse Steinmetz is a freelance reporter and producer for public radio in Massachusetts. His work covers everything from seaweed farmers to a minimalist smartphone company to the big business of internet scams and more. His work has appeared in Inc. Magazine, Duolingo, CommonWealth Beacon, as well as NPR affiliates GBH, WFAE, and Connecticut Public, among other outlets. He holds a Bachelor of Arts in English from Hampshire College and a Bachelor of Music from Eastern Connecticut State University. When he's not reporting, you can probably find him biking around Boston.

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