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Sixty-six million years ago, the story of life on Earth changed dramatically when an asteroid collided with the Yucatan Peninsula in what is now Chicxulub, Mexico. As a result of the after-effects of the collision, an estimated 75% of animal species were killed, including most dinosaurs other than birds. But almost nothing remains of the asteroid itself.
In a new study published Thursday in the journal Science, researchers pieced together the chemical identity of the asteroid that triggered the planet’s fifth mass extinction event. The dino killer was a rare clay-rich ball of mud containing materials from the early solar system, the findings suggest.
Although the Chicxulub asteroid landed thousands of years ago, learning about this ancient space rock is important because it is “part of a bigger picture of understanding the dynamic nature of our Solar System,” said study co-author, the Dr Steven Goderis, research professor of chemistry at Vrije Universiteit in Brussels.
Outline a theory of the extinction of the Nonavian dinosaurs
Scientists hypothesized in 1980 that a collision with a giant space rock caused the death of the dinosaurs. Back then, the researchers didn’t find the asteroid itself; instead, they found a thin layer of the metal iridium in rocks around the world from 66 million years ago. Iridium is rare within the Earth’s crust but is abundant in some asteroids and meteorites.
Some members of the wider scientific community were skeptical of the hypothesis. However, in 1991, scientists discovered that the Chicxulub crater was the right age to have been formed by a massive asteroid strike at the same time as the extinction of the dinosaurs. Over the years, researchers are gathering more and more evidence that the asteroid strike was indeed the trigger for the cataclysmic extinction event.
The asteroid was huge – probably between 6 and 9 miles (9.7 and 14.5 kilometers) in diameter. But its sheer size is the reason it has largely disappeared. The rock, about the size of Mount Everest, hurtled toward Earth, traveling at 15.5 miles per second (25 kilometers per second), according to NASA.
“Essentially, all of this kinetic energy is converted into heat,” Goderis said. “When the object hits the target, it will explode more; it will evaporate.” The impact created a dust cloud made up of the asteroid itself and the rock it landed on. The dust spread across the world, cutting off sunlight and lowering temperatures for years, leading to a mass extinction.
As for the asteroid, “there’s nothing left but this chemical trail that’s deposited all over the universe,” Goderis said. “This creates this tiny layer of clay that you can recognize everywhere in the world, and it’s basically the same time, 66 million years ago.”
Chemical makeup of dinosaur-killer asteroid revealed
Asteroids (and the smaller meteoroids that break off of them) come in three major types, each with their own chemical and mineral composition: metallic, stony and chondritic. In the new study, Goderis and his colleagues, including the study’s lead author, Dr. Mario Fischer-Gödde of the University of Cologne in Germany, examined the chemical composition of the thin layer of clay to unlock the asteroid’s secrets.
The researchers took samples of 66 million year old rocks from Denmark, Italy and Spain and isolated the parts containing the metal ruthenium. (Like iridium, ruthenium is more abundant in space rocks than in Earth’s crust.) The team also analyzed ruthenium from asteroid impact sites and other meteorites. Scientists discovered the chemical composition of ruthenium 66 million years ago with the chemical composition of ruthenium present in a certain type of chondritic meteorite.
“We noticed a perfect overlap with carbonaceous chondrite signatures,” Goderis said. Therefore, the asteroid that killed the dinosaurs was probably a carbonaceous chondrite, an ancient space rock that often contains water, clay and organic compounds (carbon).
Although most of the rocks in space are carbonaceous chondrites, only about 5% of the meteorites that fall to Earth belong to this category. “There’s a lot of variation in carbonaceous chondrites, and some of them can be smelled,” Goderis said. But in the inferno, when the Chicxulub impactor landed, Goderis said, “you probably wouldn’t have time for a good sniff.”
What the results mean for the future
Impacts on the scale of Chicxulub only occur every 100 million to 500 million years. But because there’s still an outside chance that Earth will cross paths with an asteroid or another giant meteorite, Goderis said it’s good to know the “physical and chemical properties of these materials, to think about how to protect ourselves ” from a collision with a large man. space rock.
Goderis mentioned the DART 2022 mission, or the Double Asteroid Redirect Test, in which NASA sent a spacecraft to deliberately knock an asteroid off course. Knowing how different types of asteroids interact with the physical forces around them would be essential for an effective planetary defense operation.
“The carbonaceous chondrite will respond completely differently to normal chondrite – it’s much more porous, it’s much lighter and it will absorb much more impact if you send something at it. So, we need to learn about this to have a corresponding response,” said Goderis.
Dr. agreed. Ed Young, professor of cosmochemistry at the University of California, Los Angeles, who was not involved in the study, with the results.
He said the discovery “enriches our understanding of what happened” when the dinosaurs went extinct. Young noted that the researchers’ assessment was a strong conclusion that the asteroid was a carbonaceous chondrite.
Kate Golembiewski He is a Chicago-based freelance science writer covering zoology, thermodynamics and death.
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