Massive Impact Crater Under the North Atlantic Suggests Dinosaur-Killing Asteroid Wasn’t Alone
Robert L. Ohlson Robert L. Ohlson 
According to a recently revealed impact crater beneath the seafloor, it is safe to assume that there might have been more than one asteroid that collided with the Earth during the time when dinosaur went extinct.
A team of researchers discovered an asteroid impact crater below the North Atlantic Ocean. The evidence uncovered might compel scientists to reconsider the theories behind the extinction of dinosaur.
According to these researchers, an asteroid that hit the Earth almost 66 million years ago created the crater. The event happened at the same time when the Chicxulub asteroid collided with the Earth near the coast of Mexico, Yucatan, causing dinosaur to go extinct.
The crater was discovered by applying seismic measurements to determine that the crater is spread over 8 km (5 miles) in diameter.
Veronica Bray, a research scientist from the University of Arizona Lunar and Planetary Laboratory and co-author of research in Science Advances, described the findings as she has been doing a deep study on craters discovered all over the solar system.
The Nadir crater, named after a close-by underwater mountain, has covered around 1,300 feet (400 meters) in the area under the seafloor, around 400km (250 miles) off the coast of Guinea, West Africa. A team of scientists believes that the asteroid that formed the recently discovered Nadir crater might have been created after fragments broke from its parent asteroid into several pieces or by a group of asteroids. If confirmed, this newly revealed crater can be considered among 20 confirmed marine impact craters discovered on Earth until now.
What Does the Crater Look Like?
Uisdean Nicholson, a geologist at Heriot-Watt University in Edinburgh, discovered the crater by accident. This means he was observing seismic reflection data from the seafloor at the time of a research project related to the spreading of the seabed; it is a geological process that resulted in bifurcating of the American and African continents and hence the origin of the Atlantic Ocean.
Nicholson said at that time, he had gathered seismic data greatly but never observed something like this. Rather than flat sedimentary sequences, he looked forward to the plateau, where he learned about an 8.5-kilometer depression below the seafloor with rare features. It has very specific characteristics that suggest a meteor impact.
He added that it also featured ejecta outside the crater that has littered sedimentary deposits spread over almost tens of kilometers outside the crater. The features were way too different from other crater-forming processes, such as the collapse of a volcano or salt withdrawal.
What Impact Would the Asteroid Have Had?
Bray used computer simulations to find the kind of collision that took place and its effects. According to these simulations, this newly discovered crater was caused by the clash of an asteroid 1300 feet or 400 meters wide in 500-800 meters (1,600 – 2,600 feet) of water.
This might have created an earthquake of over 6.5 magnitudes and a tsunami more than 3,000 feet high. Still, it is comparatively smaller than the impact of the Chicxulub global cataclysm.
If the projected size of the asteroid is to be considered, then it would have been equivalent to the Bennu asteroid. According to Bray’s calculations, the energy emitted from the collision that created the Nadir crater could have almost been a thousand times more than the tsunami created by the immense disruption underwater of the Hunga Tonga-Hunga Ha’apai volcano on the 15th of January.
The Asteroid that Killed the Dinosaur Collided with The Earth Around The Same Time
Sean Gulick, an impact expert at the University of Texas at Austin and co-author of the study, said that the newly discovered crater is known as a second impact at almost the same time as the Cretaceous–Paleogene extinction event.
As per seismic data, sediments impacted by the asteroid are anticipated to be linked with the Cretaceous-Paleogene timeline. The boundary is a sedimentary layer that determines the closing of the Cretaceous period and the last known existence of dinosaur. But still, the exact time of impact has been uncertain as the resolution of the data limits this.
Gulick said that it had been 4 billion years of impacts on the surface of the Earth, and during this time, scientists have discovered only 200 so far. Therefore, discovering a new potential impact has always been exciting news, mainly in marine surroundings, because it is a challenging feat to explore these areas.
