The Conversation contributed the article to Space.com's expert voices.
The lead author of the study describing the discovery is Uisdean Nicholson. He is an expert in geological topics. At the University of Texas at Austin, Sean Gulick is a research professor of geosciences. Veronica Bray is a research scientist at the University of Arizona. She studies impact cratering, channel formation, fracturing and landscape evolution on planets. They are the authors of the study.
The ocean floor is not explored as much as Mars. Our team of scientists discovered what appears to be an asteroid impact crater after mapping the seabed.
Intriguingly, the crater, named "Nadir" after the nearby volcano Nadir Seamount, is of the same age as the Chicxulub impact caused by a huge asteroid at the end of the Cretaceous period, around 66 million years ago, which wiped out the dinosaurs and many other species.
Related: Meteor crater: The hole from space that keeps on giving
The question of whether the crater is related to Chicxulub was raised by the discovery. It would be of huge general scientific interest as it would be one of a very small number of known marine asteroid impacts and so give new insights into what happens during such a collision.
As part of a larger project to reconstruct the tectonic separation of South America from Africa, the crater was identified using seismic reflection. The pressure waves that are sent through the ocean and its floor are similar to the waves that are sent into the air. The data allows for the reconstruction of the rocks.
At the end of 2020 we found a very unusual feature. There was a large crater, a little under 10 kilometers wide and several hundred meters deep, buried below several hundred meters of the flat, layers of the GuineaPlateau.
The scale of the crater, the ratio of height to width and the height of the crater rim are all consistent with an impact. There are chaotic deposits outside of the crater floor that look like ejecta.
The collapse of a submarine volcano or a pillar of salt below the sea were possibilities that we considered. There could be an explosion below the surface. None of these possibilities are compatible with the geology of the crater.
We created computer models of an impact event to see if we could recreate the crater.
An asteroid 1,300 feet in diameter hitting an ocean that was 800 m deep is the best simulation for the crater shape. There are consequences of an impact in the ocean. A large fireball could be seen hundreds of miles away, as well as a 2,600-foot-thick water column and asteroid.
The impact would cause shock waves that would be equivalent to a magnitude 7 or 6.5 earthquake. There was a train of waves.
The air blast from the explosion would be louder than any recorded history has to offer. The energy released from the recent eruption is a thousand times larger than the previous one. It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556
One of the most intriguing aspects of this crater is that it is the same age as the giant Chicxulub event which took place 66 million years ago. Is there a relationship between them if this is an impact crater?
There are three possibilities as to their relationship. They may have formed from the break up of a parent asteroid, with the larger fragment resulting in the Chicxulub event and a smaller fragment forming the Nadir crater. The mass extinction event could have been worse if the Chicxulub impact had been added to.
The break-up could have been caused by an earlier near-collision when the asteroid or comet was close to Earth. There is a chance that the collision could have happened on a subsequent flight.
This pull-apart is what happened to the Shoemaker-Levy 9 comet when it collided with Jupiter in 1994.
It's possible that Nadir was part of a larger impact cluster that formed after a collision in the asteroid belt. The little cousin hypothesis is related to this.
This collision may have sent a shower of asteroids into the inner solar system, which may have collided with Earth and other inner planets. When there were many impact events in a short period of time, we have a precedent for this.
This could be a coincidence. There is a chance of a collision of a Nadir-sized asteroid. We can't say for certain that the Nadir crater was formed by an asteroid impact until we recover samples from the crater floor. We submitted a proposal to drill the crater through the International Ocean Discovery program.
As with the main impact crater hypothesis, we can only test the little sister and little cousin hypotheses by dating the crater using samples and looking for other craters of the same age.
Could such an event happen soon? The size of the asteroid that we model is very close to the Bennu asteroid. The asteroid has a one-in-1,750 chance of colliding with Earth in the next couple of centuries, making it one of the most dangerous objects in the solar system.
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