October, 2024

Asteroid that killed the Dinosaurs was not alone

The huge asteroid that struck Earth and wiped out the dinosaurs 66 million years ago was not alone, scientists have confirmed.

A second, smaller space rock slammed into the sea off the coast of West Africa during the same period, causing a large crater. It would have been a “catastrophic event,” the scientists said, which would have sent a tsunami at least 800 meters high across the Atlantic Ocean.

Dr. Uisdean Nicholson of Heriot-Watt University in the United Kingdom first discovered the Nadir crater in 2022, but a cloud of uncertainty hung over how it was actually formed. Now Dr. Nicholson and his colleagues are certain that the 9-km-long depression was caused by an asteroid crashing into the seafloor.

They cannot precisely date the event or say whether it came before or after the asteroid that left the 180-km-wide Chicxulub crater in Mexico. That ended the reign of the dinosaurs. But they say the smaller rock also came at the end of the Cretaceous, when they went extinct. When it crashed into Earth's atmosphere, it is said to have formed a huge fireball.

The asteroid that caused the Nadir crater was about 450-500 meters wide, and scientists believe it hit Earth at about 72,000 mph. The closest man has come to an event of this size was the Tunguska event in 1908, when a 50-meter asteroid exploded in the sky over Siberia.

The Nadir asteroid was about the same size as Bennu, currently the most dangerous object in orbit. Scientists say the most likely date Bennu could hit Earth is Sept. 24, 2182, according to Nasa. But that is still only a 1 in 2,700 chance.

There has never been an impact of an asteroid of this size in human history, and scientists normally have to study eroded craters on Earth or images of craters on other planets. To better understand the Nadir crater, Dr. Nicholson and his team analyzed high-resolution 3D data from the geophysical company TGS. Most craters have been eroded, but this one was well preserved, allowing the scientists to look further into the rock.

“This is the first time we've been able to look into an impact crater like this - it's really exciting,” says Dr. Nicholson. Nicholson adds that there are only 20 marine craters in the world, but none have been studied in this much detail.