New impact crater dates back to the end of the dinosaurs

Scientists have long known about the massive asteroid impact crater on what is now the Gulf of Mexico, which wiped out the dinosaurs and most other organisms on our planet 66 million years ago. Now, the discovery of what appears to be a second impact crater on the other side of the Atlantic – about 400 kilometers off the coast of Guinea, West Africa – raises the question of whether more than one giant meteorite bombarded the Earth on that fateful day.

The Nadir Crater, located 300 meters below the seabed, was discovered accidentally by Dr. Uisdean Nicholson, a geoscientist at the Herriot-Watt University, while he was analyzing seismic survey data to better understand past climatic changes. 

“These surveys are kind of like an ultrasound of Earth. I’ve spent probably the last 20 years interpreting them, but I’ve never seen anything like this,” Dr. Nicholson reported. “Nadir’s shape is diagnostic of an asteroid impact. It’s got a raised rim surrounding a central uplift area, and then layers of debris that extend outwards.”

While the asteroid that created the Chicxulub Crater in the Gulf of Mexico is estimated to measure over 12 kilometers in diameter, simulations suggest that the one responsible for the Nadir Crater was only about 400 meters wide. 

However, according to Veronica Bray, a planetary scientist at the University of Arizona, the impact would have generated a tsunami over one kilometer high, as well as an earthquake with a magnitude of about 6.5. “The energy released would have been around 1,000 times greater than that from the January 2022 eruption and tsunami in Tonga,”said Bray.

Yet, how closely related in time the two asteroid impacts were remains an open question. The analysis of fossils of known age drilled from a borehole near the Nadir Crater suggest that the impact may have occurred at a similar date with that in Mexico, but further examinations of rocks from the crater are needed to draw clear conclusions. 

Geologist Sean Gulick argues that while the asteroid might have fallen to Earth on the same day, it is also possible that it struck our planet a million years before or after the Mexican cataclysm. “A much smaller cousin, or sister, doesn’t necessarily add to what we know about the dinosaurs’ extinction, but it does add to our understanding of the astronomical event that was Chicxulub,” he said. 

“Was this a break-up of a parent body that had multiple fragments that hit the Earth over time? Was Chicxulub a double asteroid where a smaller object orbited a bigger one? These are interesting questions to pursue, because to learn that Chicxulub might have this extra excitement of a second crater at the same time changes the story a little bit about how Chicxulub came to be.”

The discovery of the Nadir Crater is reported in the journal Science Advances.

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By Andrei Ionescu, Earth.com Staff Writer