Impact Crater May Be Killer Dinosaur’s Baby Cousin

Dinosaur artwork

Dinosaur artwork

When an asteroid hit what is now the Gulf of Mexico 66 million years ago, wiping out the dinosaurs, did it have a mate?

Was Earth bombarded that fateful day by more than one space rock?

The discovery of what appears to be a second impact crater on the other side of the Atlantic, of a similar age, raises these questions.

It is not as big as the one we know in Chicxulub in Mexico, but it still speaks of a catastrophic event.

Named Nadir Crater, the new feature lies more than 300 meters below the sea floor, about 400 kilometers off the coast of Guinea, in west Africa.

With a diameter of 8.5 kilometers, it is possible that the asteroid that created it was just under half a kilometer in diameter.

Map

Chicxulub (Ch), Nadir (Nd) and Boltysh (Bo) craters have ages that cluster around 66 million years ago

Hidden depression was identified by Dr Uisdean Nicholson of Heriot-Watt University, Edinburgh, UK.

He was analyzing seismic survey data, looking for somewhere to drill, to better understand past climate changes on Earth.

Such surveys, often taken by oil and gas prospectors, record the different layers of rock and sediment underground, often several kilometers deep.

“These surveys are like an ultrasound of the Earth. I’ve spent probably the last 20 years interpreting them, but I’ve never seen anything like this,” he told BBC News.

“Nadir’s shape is diagnostic of an asteroid impact. It has a raised rim surrounding a central uplift area and then layers of debris extending outward.”

Seismic data

Seismic data

The asteroid that created the Chicxulub crater in the Gulf of Mexico was estimated to be about 12 km in diameter. It gouged out a depression 200 km wide and in the process triggered strong earthquakes, a tsunami and a global storm. So much dusty material was thrown into the sky that the Earth was plunged into a deep freeze. Dinosaurs could not overcome climate shock.

In comparison, the effects from a Nadir sized shock would be much, much smaller.

“Our simulations suggest that this crater was caused by the collision of a 400m-wide asteroid into 500-800m of water,” explained Dr Veronica Bray from the University of Arizona in the US.

“This would have created a tsunami over a kilometer high, as well as an earthquake of around 6.5 on the Richter scale.

“The energy released would be about 1,000 times greater than that from the January 2022 eruption and tsunami in Tonga.”

Chicxulub would be 10 million times larger.

Chicxulub map

The crater’s outer rim curves under Mexico’s Yucatan Peninsula

  • A 12 km wide object dug a hole about 100 km wide and 30 km deep

  • This bowl then collapsed, leaving a crater 200 kilometers wide and several kilometers deep

  • Today, much of the crater is buried offshore, under 600 meters of sediment

  • On land it is covered by limestone, but its rim is marked by sinkholes

  • Scientists recently drilled into the crater to learn about its formation

Cenote

Mexico’s famous cenotes have formed in weakened limestone above the crater

Dr Nicholson’s team should be cautious about linking the two effects together.

Nadir has a very similar date to Chicxulub based on an analysis of fossils of known age unearthed from a nearby borehole. But to make a definitive statement, the rocks in the crater itself will have to be pulled up and examined. This would also confirm that Nadir is indeed an asteroid impact structure and not some other, unrelated feature caused by, say, ancient volcanism.

The idea that Earth may have been hit by a cluster of large space rocks in the past is not new.

And people have already speculated that the impactor that created Boltysh Crater in Ukraine may also be related to the Chicxulub event in some way. His age is not too dissimilar.

Professor Sean Gulick, who co-led the recent Chicxulub Crater drilling project, said Nadir may have hit Earth on the same day. Or it might have hit the planet a million or two years either side of the Mexican flood. Scientists will only know for sure when rocks from the West African crater are inspected in the lab

“A much smaller cousin, or sister, doesn’t necessarily add to what we know about the dinosaur extinction, but it does add to our understanding of the astronomical event that was Chicxulub,” the University of Texas at Austin researcher told BBC News. .

“Was this a breakup of a parent body that had multiple fragments that hit Earth over time? Was Chicxulub a binary asteroid where a smaller object orbited a larger one?”

“These are interesting questions to pursue, because learning that Chicxulub can have this extra excitement of a second crater at the same time changes the story a little bit about how Chicxulub formed.”

The Nadir Crater feature is reported in the journal Science Advances.

K-Pg boundary rock layers (Tanis)

K-Pg boundary rock layers (Tanis)

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