New research suggests that the asteroid that wiped out the dinosaurs and sent Earth into a tailspin 66 million years ago wasn’t just a one-off. Detailed scans of an underwater crater off the coast of Guinea reveal that another giant asteroid struck Earth around the same time, potentially contributing to the cataclysmic conditions that led to the dinosaurs’ extinction.
When the Chicxulub asteroid slammed into modern-day Mexico at the end of the Cretaceous period, it created a crater 180 kilometers wide under the sea off the Yucatan Peninsula. The resulting impact released a tsunami, mega-earthquake, and a slew of other environmental changes. Among them, the crater’s vaporized material sucked up plant life into the atmosphere, which cut off the food supply for herbivores and made it harder for carnivores to survive. The resulting ecological collapse put the brakes on the entire food chain and led to a mass extinction that killed off most species.
For decades, scientists thought they had the extinction story wrapped up. The asteroid that smashed into Earth had been a carbonaceous chondrite meteorite. They assumed it was responsible since it created the geological boundary layer corresponding to the dinosaurs’ extinction. Then, in the 1980s, scientists uncovered traces of iridium (a rare element found in asteroids) in rock layers worldwide, indicating that it wasn’t just the asteroid that hit.
But now researchers are reporting in Science Advances that a crater buried under the North Atlantic Ocean may also be the scar of an extraterrestrial collision. This crater, called Nadir, could be the remnant of an asteroid that slammed into Earth at the same time as the Chicxulub impact, marking the boundary between the Cretaceous and Paleogene periods.
Based on sediment thickness, the Nadir crater dates back to this interval and is 8.5 km wide. Seismic data indicate that the collision would have triggered intense tremors and liquefied sediments beneath the sea bed, creating faults and landslides that spread across the continental shelf. The tsunamis generated by the impacts, which would have been more than a kilometer high, are also recorded in the crater’s rims and central uplift.