Dinosaur-Killing Asteroid May Have Had a Friend

Fossils suggest 5-mile-wide crater off West Africa is also 66M years old
By Arden Dier,  Newser Staff
Posted Aug 18, 2022 7:30 PM CDT
Dino-Killing Asteroid May Have Had a Friend
An illustration of an asteroid about to hit.   (Getty Images/MARHARYTA MARKO)

The 6-mile-wide asteroid that wiped out the dinosaurs 66 million years ago may have had a baby cousin that struck on the opposite side of the Atlantic Ocean. Dr. Uisdean Nicholson of Scotland's Heriot-Watt University discovered a hidden depression of a similar age as the Chicxulub Crater in Mexico while analyzing seismic survey data, which show layers of rock and sediment deep underground. "These surveys are kind of like an ultrasound of Earth," Nicholson tells the BBC. "I've spent probably the last 20 years interpreting them, but I've never seen anything like this." The feature—with "a raised rim surrounding a central uplift area, and then layers of debris that extend outwards"—sure looks like an impact crater, fewer than 200 of which are confirmed on Earth.

Dubbed Nadir Crater, the depression described Thursday in Science Advances is miniature compared to the 125-mile-wide Chicxulub Crater. It's thought that an asteroid less than a third of a mile wide caused the gash that stretches more than 5 miles wide some 250 miles off the coast of Guinea. But it would have been catastrophic nonetheless. Water and rock would've been instantly vaporized. A wave more than half a mile high would've hit West Africa, researchers say, while 16-foot-high tsunamis would've struck South America, per Live Science. The impact would've also triggered an earthquake of at least 6.5 magnitude. "The air blast would have been heard across the globe, and would have itself caused severe local damage across the region," Nicholson adds, per CNN.

Though the depression itself hasn't been dated—researchers would need to drill into the crater, which lies 1,000 feet below the seabed—microfossils from nearby exploration wells indicate it was formed 66 million years ago, with a margin of error of 1 million years. It's possible it was part of a cluster of asteroids that struck Earth around the same time—the 15-mile-wide Boltysh Crater in Ukraine has also been dated to the same period—or it might have orbited Chicxulub as part of a double asteroid. "The opportunity to study an underwater impact crater of this size would help us understand the process of ocean impacts, which are the most common but least well preserved or understood," University of New Mexico asteroid expert Mark Boslough, who was not involved in the research, tells CNN. (More asteroid stories.)

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