Scientists say second 'catastrophic' asteroid hit Earth when dinosaurs wiped out

The massive asteroid that wiped out the dinosaurs when it slammed into the earth 66 million years ago was joined by a second space rock impact at around the same time, scientists have confirmed.

During the same time as the asteroid that caused the dinosaur-killing 200 km wide Chicxulub impact crater in Mexico, a second, smaller rock smashed into the sea off the coast of West Africa, creating a large crater. It would have been a “catastrophic event”, the scientists say, causing a tsunami at least 800m high to tear across the Atlantic ocean.

Dr Uisdean Nicholson of Heriot-Watt University discovered the Nadir Crater in 2022 when studying seismic reflection data of the Atlantic Ocean’s seabed, off the coast of Guinea in west Africa. The data revealed a depression over 8.5km wide, which Dr Nicholson suspected could be an asteroid impact crater. He worked with planetary scientists and geologists in the UK and the USA to classify the crater: the data suggested it was from an asteroid hundreds of metres wide hitting the planet around 66 million years ago, but they couldn’t state that definitively.

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Now they can thanks to new high-resolution, 3D seismic data captured by TGS, a global geophysical company and shared with Dr Nicholson, a geologist. The data proves that an asteroid caused the Nadir Crater.

Dr Nicholson said: “There are around 20 confirmed marine craters worldwide, and none of them has been captured in anything close to this level of detail. It’s exquisite.

“Craters on the surface are usually heavily eroded and we can only see what is exposed, whereas craters on other planetary bodies usually only show the surface expression. These data allow us to image this fully in three dimensions and peel back the layers of sedimentary rock to look at the crater at all levels.

Using the data, the scientists created a timeline of what happened in the seconds and minutes after impact.

Dr Nicholson told the BBC: “Imagine the asteroid was hitting Glasgow and you’re in Edinburgh, around 50 km away. The fireball would be about 24 times the size of the Sun in the sky - enough to set trees and plants on fire in Edinburgh."

He added: “After the impact and the central uplift forming, the soft sediments surrounding the crater flowed inwards towards the evacuated crater floor, creating a visible ‘brim’.

“The earthquake shaking caused by the impact appears to have liquefied the sediments below the seabed across the entire plateau, causing faults to form below the seabed.

“The impact was also associated with large landslides as the plateau margin collapsed below the ocean. As well as this, we see evidence for a train of tsunami waves going away from, then back towards the crater, with large resurge scars preserving evidence of this catastrophic event.”

The data allowed the scientists to reveal the minute-by-minute chaos after the event. Dr Nicholson said: “The new images paint a picture of the catastrophic event. We originally thought the asteroid would have been around 400m wide. We now think it was 450-500m wide, because of the larger crater size as shown by the 3D data.

“We can tell it came from about 20-40 degrees to the northeast, because of spiralling thrust-generated ridges surrounding the crater's central peak - those are only formed following a low-angle oblique impact.

“And we think it would have hit Earth at about 20 km per second, or 72,000 km per hour, although we still need to confirm this with a new set of impact models.”