Science

Dinosaur-killing asteroid struck at "deadliest possible angle"

Dinosaur-killing asteroid stru...
An artist's imagining of the fateful day when an asteroid slammed into Earth some 66 million years ago
An artist's imagining of the fateful day when an asteroid slammed into Earth some 66 million years ago
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An artist's imagining of the fateful day when an asteroid slammed into Earth some 66 million years ago
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An artist's imagining of the fateful day when an asteroid slammed into Earth some 66 million years ago
In the Chicxulub crater, the three centers – crater, mantle uplift and peak ring – line up in a northeast-southwest direction, telling the researchers that the asteroid struck from a northeast direction at an angle of 60 degrees
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In the Chicxulub crater, the three centers – crater, mantle uplift and peak ring – line up in a northeast-southwest direction, telling the researchers that the asteroid struck from a northeast direction at an angle of 60 degrees
A simulation of what an impact at 60 degrees looks like – and it matches the observed structures at Chicxulub crater
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A simulation of what an impact at 60 degrees looks like – and it matches the observed structures at Chicxulub crater
A simulation of what happens when a large asteroid strikes at an angle of 30 degrees. It doesn't match observed structures at Chicxulub crater, allowing the researchers to rule out this shallow angle of approach
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A simulation of what happens when a large asteroid strikes at an angle of 30 degrees. It doesn't match observed structures at Chicxulub crater, allowing the researchers to rule out this shallow angle of approach
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It turns out that the dinosaurs had far worse luck than we thought. While a gigantic asteroid slamming into the Earth is never going to be a sign of good luck, a new study has shown that the space rock hit the planet at the deadliest possible angle, maximizing the devastating climate change that followed.

About 66 million years ago, an asteroid at least 10 km (6.2 mi) wide crashed into what is now the Yucatan Peninsula in Mexico. The impact event wiped out three quarters of all life on Earth at the time, including the dinosaurs and 93 percent of mammals.

While death would have been pretty swift for anything unlucky enough to be too close to the impact zone, most life on the planet succumbed to the cascading climate effects that followed. Huge amounts of vaporized rock, sulfur, carbon dioxide and water vapor were sent into the atmosphere, where they choked the air and blocked out the Sun. In all, the sky would have darkened for about 18 months, killing off most photosynthesizing plants and toppling food chains on land and in the ocean.

Now, a new study has calculated the angle of the impact and the direction from which the asteroid approached. To do so, researchers from Imperial College London, the University of Freiburg and the University of Texas at Austin studied the shape and structure of the Chicxulub crater.

There are three parts of the crater that together can reveal the story of the impact. There’s the center of the crater itself. There’s the peak ring, which is the mountainous ring that rises up in the middle of the main crater almost like a smaller secondary crater. And there’s the mantle rocks far below the crater, which are uplifted.

In the Chicxulub crater, the three centers – crater, mantle uplift and peak ring – line up in a northeast-southwest direction, telling the researchers that the asteroid struck from a northeast direction at an angle of 60 degrees
In the Chicxulub crater, the three centers – crater, mantle uplift and peak ring – line up in a northeast-southwest direction, telling the researchers that the asteroid struck from a northeast direction at an angle of 60 degrees

Finding how the centers of these three regions line up indicates the direction and angle of the asteroid. In this case, the centers were all aligned in a southwest-northeast direction. The center of the crater itself was in the middle of this line, between the peak ring and mantle uplift centers.

When the researchers ran 3D simulations of the impact, they identified the version of events that most closely matched the observed features in the crater. According to the team, the asteroid came in from the northeast on an angle of about 60 degrees to the ground. And that has important implications for what happened next.

“We know that this was among the worst-case scenarios for the lethality on impact, because it put more hazardous debris into the upper atmosphere and scattered it everywhere – the very thing that led to a nuclear winter,” says Gareth Collins, lead researcher on the study.

This isn’t the first study to investigate just how unlucky the dinosaurs really were. A few years ago, a team of Japanese researchers found that had the asteroid hit almost anywhere else on the planet, the extinction event that followed would likely not have been so severe. That’s because the location of the impact site was rich in hydrocarbons, which would throw more soot into the atmosphere. Only 13 percent of the Earth’s surface would have this devastating effect, and that’s exactly where it hit.

The new study was published in the journal Nature Communications.

Source: Imperial College London

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4 comments
buzzclick
To think that had this event not happened 66 million years ago, our human existence would be radically different today. Makes for a great script for a disaster movie pitting the humanoids against the evil and powerful dino-sores. lol
DaveWesely
And in a related question, did the meteor impact create the Gulf of Mexico? Before the impact, were the Americas more of a unified land mass? If so, that would illustrate the scale of the event.
Karmudjun
Another great write up. Excellent explanation, good prose - I enjoy reading your informative synopses. Thank you Mr. Irving.
martinwinlow
So those darn fossil fuels had a previous go at destroying life on Earth (with a little help from a humongous asteroid)... and here we are 66m years later and humanity is providing the helping hand to do it all over again. Only, this time, not so much as with a bang... but a whimper.