A huge crater under the North Atlantic reveals that an asteroid that killed the dinosaurs wasn’t alone

A recently discovered crater under the sea floor indicates that more than one asteroid may have hit Earth during the time when the dinosaurs became extinct.

Scientists have discovered evidence of an asteroid impact crater under the North Atlantic Ocean. It could force researchers to rethink how dinosaurs came to the end of their reign.

The team believes that the crater was caused by an asteroid colliding with Earth about 66 million years ago. This was around the same time that the Chicxulub asteroid hit Earth off the coast of today’s Yucatan, Mexico, wiping out the dinosaurs.

The crater, more than 5 miles (8 kilometers) in diameter, was discovered using seismic measurements, which allow scientists to explore deep within the Earth’s surface.

Veronica Bray, research scientist at the University of Arizona’s Planetary and Lunar Laboratory, co-author of a study in science progress In detail the discovery. It specializes in craters located throughout the solar system.

Named after a nearby seamount, Nader’s crater is buried up to 1,300 feet (400 meters) below the sea floor about 250 miles (400 kilometers) off the coast of Guinea, West Africa. According to the research team, the asteroid that created the newly discovered Nader crater may have been formed by the crash of an original asteroid or by a swarm of asteroids in that time period. If the crater is confirmed, the crater will be one of fewer than 20 confirmed marine archaeological craters found on Earth.

Veronica Bray, photographed here during a visit to the Meteor Crater in northern Arizona, is an expert in crater formation. Credit: Sarah Sutton/Moon and Planetary Laboratory

What is the asteroid impact?

Bray used computer simulations to determine what kind of collision had occurred and what the possible effects were. Simulations indicate that the crater was caused by the impact of an asteroid 1,300 feet (400 meters wide) in 1,600 to 2,600 feet (500 to 800 meters) of water.

“This could have caused a tsunami of more than 3,000 feet, as well as a 6.5-magnitude earthquake,” Bray said. “Although much smaller than the global catastrophe of the Chicxulub effect, Nader has contributed significantly to the local devastation. And if we find one of the Chicxulub ‘brothers’, it opens the question: Are there others?”

The estimated size of the asteroid would put it roughly on par asteroid bennoTarget Osiris Rexled by UArizona[{” attribute=””>NASA asteroid sample return mission. According to Bray’s calculations, the energy released from the impact that caused the Nadir crater would have been around 1,000 times greater than the tsunami caused by the massive underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano in the Polynesian country of Tonga on January 15.

“These are preliminary simulations and need to be refined when we get more data,” Bray said, “but they provide important new insights into the possible ocean depths in this area at the time of impact.”

What does the crater look like?

The crater was discovered somewhat by accident by Uisdean Nicholson, a geologist at Heriot-Watt University in Edinburgh. He was examining seismic reflection data from the seabed during a research project dedicated to seafloor spreading, the geologic process that caused the African and American continents to drift apart, thereby opening the Atlantic Ocean.

“I’ve interpreted lots of seismic data in my time, but had never seen anything like this. Instead of the flat sedimentary sequences I was expecting on the plateau, I found an 8.5-kilometer depression under the seabed, with very unusual characteristics,” Nicholson said. “It has particular features that point to a meteor impact crater. It has a raised rim and a very prominent central uplift, which is consistent for large impact craters.

“It also has what looks like ejecta outside the crater, with very chaotic sedimentary deposits extending for tens of kilometers outside of the crater,” he added. “The characteristics are just not consistent with other crater-forming processes like salt withdrawal or the collapse of a volcano.”

The asteroid crashed around same time as the dinosaur killer

“The Nadir Crater is an incredibly exciting discovery of a second impact close in time to the Cretaceous–Paleogene extinction,” said study co-author Sean Gulick, an impact expert at the University of Texas at Austin. “While much smaller than the extinction causing Chicxulub impactor, its very existence requires us to investigate the possibility of an impact cluster in the latest Cretaceous.”

According to the seismic data, the sediments impacted by the asteroid likely correspond with the Cretaceous-Paleogene boundary – a sedimentary layer demarcating the end of the Cretaceous period and last known occurrence of dinosaurs. However, there is some uncertainty about the precise time of impact, limited by the resolution of the data.

“Despite 4 billion years of impactors hitting Earth, only 200 have been discovered,” Gulick said. “It is thus exciting news whenever a new potential impact is discovered, especially in the hard-to-explore marine environment.”

Nicholson has already applied for funding to drill into the seabed to confirm that it’s an asteroid impact crater and test its precise age.

Reference: “The Nadir Crater offshore West Africa: A candidate Cretaceous-Paleogene impact structure” by Uisdean Nicholson, Veronica J. Bray, Sean P. S. Gulick and Benedict Aduomahor, 17 August 2022, Science Advances.
DOI: 10.1126/sciadv.abn3096