The Dinosaur-Killing Asteroid May Have Had a Companion

A newly discovered crater suggests a second impact that would have triggered underwater landslides and tsunamis

An illustration of a T. rex watching as an asteroid hits Earth
A second asteroid may have struck the dinosaurs at the end of Cretaceous period, around 66 million years ago Mark Garlick / Science Photo Library via Getty Images

On its own, the dinosaur-killing asteroid had a staggering impact: Wildfires raged across the continents, tsunamis pummeled coastlines and about three-quarters of Earth’s species went extinct. But now, new evidence suggests this massive chunk of rock may have had a partner: Scientists discovered what might be an impact crater off the coast of Guinea that they say dates to 66 million years ago—around the same time as the collision that wiped out the dinosaurs.

This second asteroid may have broken off from the dinosaur-killer, known as Chicxulub, or it may have been part of a closely timed impact cluster, according to a new study published in Science Advances

“A lot of people have questioned: How could the Chicxulub impact—albeit a huge one—be so globally destructive?” Veronica Bray, a planetary scientist from the University of Arizona and paper co-author, tells National Geographic’s Maya Wei-Haas. “It might be that it had help.”

Researchers discovered what they dubbed the Nadir crater—named after a nearby underwater volcano—in 2020, while examining seismic survey data. “We came across a highly unusual feature,” write Bray and co-authors Uisdean Nicholson and Sean Gulick for The Conversation. “Among the flat, layered sediments of the Guinea Plateau, west of Africa, was what appeared to be a large crater, a little under 10 km wide and several hundred meters deep, buried below several hundred meters of sediment.” 

Nicholson, a geoscientist from Heriot-Watt University in the United Kingdom, has been interpreting such surveys for about 20 years. But he has “never seen anything like this,” he tells BBC News’ Jonathan Amos.

Though scientists haven’t confirmed it was caused by an asteroid, features of Nadir, including its scale, the ratio of height to width and the height of the crater rim, are consistent with an impact origin, write the authors in The Conversation. Additionally, deposits around Nadir look like materials ejected from a crater after a collision. 

Computer modeling showed that to cause this impact, an asteroid would likely have been about 0.25 miles across and hit an ocean that was more than 2,600 feet deep, per The Conversation. In comparison, the Chicxulub asteroid was likely around six miles wide. Still, this second impact would have been sizable. 

Model of the impact sequence at the Nadir Crater in four images
Model of the impact sequence at the Nadir crater Nicholson et al. via Science Advances

"The energy released would have been around 1,000 times greater than that from the January 2022 eruption and tsunami in Tonga,” Bray tells BBC News. 

The hit would have caused shock waves equivalent to a magnitude 6.5 or 7 earthquake, which would have triggered underwater landslides and a series of tsunamis, write the authors. 

“The discovery of a terrestrial impact crater is always significant, because they are very rare in the geologic record,” Mark Boslough, an earth and planetary scientist at the University of New Mexico, who was not involved in the research, tells CNN’s Katie Hunt. “There are fewer than 200 confirmed impact structures on Earth and quite a few likely candidates that haven’t yet been unequivocally confirmed.” 

To verify that Nadir was truly formed by an asteroid strike, as well as find a precise date for the collision and determine its connection to Chicxulub, scientists will need to drill into the formation and collect samples. The team has already applied for emergency funds for this additional research, per National Geographic

The drilling could also give scientists clues about how life on Earth responded to the impact. “Part of the Nadir drilling goal is to analyze the sediment that was deposited onto Nadir over time,” Bray tells Inverse’s Kiona Smith. “When did life recover? How?”