Not just one, but two asteroids may have been responsible for the extinction of dinosaurs

(Homeland) - A structure resembling a volcano mouth, 8.5 km wide, lies hundreds of meters beneath the sea.

Chicxulub, the asteroid that wiped out most dinosaur species, could possibly have a 'sibling' that fell to Earth, smaller in size.

Off the coast of West Africa, hundreds of meters beneath the sea, scientists have identified what seems to be the remnants of an 8.5 km-wide impact crater, which they named Nadir.

The uneven seafloor off the coast of West Africa might have been shaped by an asteroid, 400 meters long, crashing into the ocean simultaneously with the impact that led to the extinction of dinosaurs.

The research team estimates that the volcano mouth formed around the same time as another asteroid - Chicxulub, the dinosaur killer - collided with what is now Mexico. Reported in the journal Science Advances on 17/8, if confirmed, this could mean that dinosaurs were not wiped out by a single asteroid impact, but instead, by up to two asteroids.

Nearly 200 impact craters have been discovered on Earth, with most of them on land. Co-author of the study, Veronica Bray, a planetary scientist at the University of Arizona in Tucson, explains that underwater craters gradually get buried under sediment layers, turning the Nadir structure into a valuable scientific find.

Uisdean Nicholson, a geologist at Heriot-Watt University in Edinburgh, serendipitously uncovered this structure while analyzing data collected by seismic waves beneath the ground to detect subsurface geological structures off the coast of Guinea.

Concealed beneath the sea - and at a depth of nearly 1 km of water - he observed a bowl-shaped structure with a broken staircase layer and a prominent central peak.

Using seismic waves transmitted through the seafloor, researchers constructed this false-color image of the buried Nadir structure. The ocean (blue) on top, the horizontal lines and bands below indicate Earth's geological layers, with older layers lower. Nadir appears as a depression (top center) at the bottom of the brown layers. The broken staircase layers, intricate central peak, and the distorted rock below the depression are typical features of large impact craters.

Based on the size of the structure, Bray, Nicholson, and their colleagues calculate that if an asteroid created this distinctive landscape, it could have been wider than 400 meters. Furthermore, the researchers estimate that the impact would cause ground shaking equivalent to a powerful 7 Richter scale earthquake and generate high tsunami waves.

Michael Rampino, a geologist from New York University not involved in the study, suggests that the impact of Nadir would be far less destructive compared to the impact from the Chicxulub asteroid, which was about 10 km wide. He says: 'It certainly won't have a global impact'.

Using adjacent geological layers with Nadir, the research team estimates the structure formed around the late Cretaceous period - 66 million years ago. Researchers speculate that the Nadir asteroid might have even formed in tandem with the Chicxulub asteroid, both later separating due to gravitational forces during a previous Earth flyby.

However, the study's conclusions raise skepticism among some experts. Geologist Philippe Claeys from Vrije Universiteit Brussel in Belgium, not part of the study, remarks: 'It looks like an impact crater, but it could be something else. Confirming this structure as an impact crater will require more in-depth investigation, especially drilling into geological layers to find conclusive evidence, such as quartz'.

The age of the Nadir structure is another uncertainty. Seismic data suggests it likely formed around the end of the Cretaceous period or possibly a bit later, Claeys notes. Rampino suggests drilling into the volcano mouth to find minerals containing radioactive elements could provide a more accurate formation date.

This isn't the first time scientists have investigated whether Chicxulub had accomplices. Some studies suggest that the Boltysh volcano in Ukraine may have formed concurrently with Chicxulub, although researchers have determined that Boltysh formed 650,000 years later.

Bray and her colleagues are currently negotiating funding to collect samples from the volcano mouth, with hopes to drill in 2024. That is expected to settle some debates around the origin of Nadir, Bray says, although new questions may arise. 'If we prove this is the twin of the 'dinosaur killer,' there could very well be many more siblings'.

References: Sciencenews; Sina; Zhihu