Was it indeed two asteroids that brought an end to the dinosaur era?
Approximately 66 million years ago, a substantial asteroid struck Mexico, causing a mass extinction that led to the demise of the dinosaurs. The evidence for this catastrophic event can be found in the Chicxulub crater, which is around 200 kilometers in diameter and located on the Yucatan Peninsula. Recently, researchers have discovered another asteroid impact off the coast of Africa around the same time, leading many to question if it was a fragment of the original asteroid.
A crater approximately 9 kilometers in diameter was discovered off the coast of Guinea, buried under hundreds of meters of sediment. According to a recent study, this crater, known as the Nadir crater, was likely caused by an asteroid impact as well. Could the combination of these two impacts have sealed the fate of the dinosaurs?
"Just like an ultrasound"
Geologists led by Uisdean Nicholson of Heriot-Watt University in Edinburgh were able to use a new 3D seismic method to reveal the exact shape of the Nadir crater hidden beneath the seabed. Nicholson explained, "It's just like an ultrasound during pregnancy. A few generations ago, ultrasound only showed a grainy spot. Today, we can see the facial features of the baby in 3D, and with incredible detail."
Compared to the Chicxulub crater in Mexico, the Nadir crater off Guinea is much smaller. With a diameter of about 9.2 kilometers, it could still fit a city the size of Kassel. However, the asteroids also had varying dimensions: the Chicxulub object was about 14 kilometers in size, while the Nadir asteroid was only 450 to 500 meters in diameter.
Tsunami-inducing impact
The impact off Africa was also devastating. The asteroid struck the sea at a depth of 800 meters, traveling at an estimated 72,000 kilometers per hour. The impact caused a crater over 200 meters deep on the seabed and triggered a massive tsunami wave that rolled through the Atlantic.
Researchers can't pinpoint the exact date of the Nadir impact, but the temporal proximity to the Chicxulub event has led them to speculate that the mass extinction at the time was the result of a cosmic double strike. However, they cannot definitively establish a connection between the two events and can only suggest possible explanations, such as the breakup of a parent asteroid in near-Earth orbit or a phase of frequent impacts lasting up to 2 million years.
Impact crater in the North Sea?
Researchers have identified around 200 impact craters worldwide, with about 20 of them being underwater. Many craters have eroded over time, but the 3D method used in this study provides new possibilities for investigating the origin of other craters, such as the Silverpit crater in the North Sea, which is 2.4 kilometers in diameter.
The final confirmation that the Nadir crater off the coast of Africa was indeed caused by an asteroid impact is still pending. Future ocean drilling could provide the conclusive evidence, according to the study.
The discovery of the Nadir crater highlights the importance of studying ancient asteroid impacts, as it could provide new insights into the role of such events in major extinctions, such as the one that led to the demise of the dinosaurs. Furthermore, advancements in seismic technology, like the one used by Geologists led by Uisdean Nicholson, enable us to better understand the exact shape and size of these craters, much like how ultrasound technology has improved our ability to visualize a fetus in pregnancy.
