A rare type of space rock known as a CO chondrite is the likely culprit behind the mass extinction event that wiped out 75 percent of all species 66 million years ago. Researchers from the University of British Columbia (UBC), along with colleagues in Paris, Brussels, and Vienna, identified the impactor by analyzing nickel isotopes in the Cretaceous-Paleogene (KT) clay layer, according to findings published in Science Advances.
Identifying the Chicxulub Impactor Through Nickel Isotopes
Determining the composition of an object that vaporized millions of years ago requires extreme precision. Scientists from the Institut de Physique du Globe and the Université de Paris analyzed samples of the global clay layer deposited immediately following the impact. Because the original projectile was almost entirely destroyed upon hitting Earth, only minute traces of its chemical signature remain.
By measuring nickel isotopes within these thin clay deposits, the team successfully narrowed the object’s identity to a carbonaceous chondrite of the Ornans class (CO). Dr. Philippe Claeys, a professor at Vrije Universiteit Brussel and visiting professor at UBC, notes that the process is exceptionally challenging due to the scarcity of the remaining material.
Did you know?
Carbonaceous chondrites represent only about five percent of all meteorites sampled on Earth. The CO subclass is even rarer, consisting of some of the most primitive, least altered material left over from the formation of our solar system.
Why Debris, Not Sulfur, Likely Drove the Extinction
The discovery that the impactor was a CO chondrite shifts scientific understanding of how the Chicxulub event triggered such a global catastrophe. Previous theories often pointed to sulfur as the primary driver of the mass extinction, suggesting that sulfur-rich vapor from the meteorite cooled the planet significantly.
However, the new research indicates that CO chondrites contain significantly lower levels of volatile elements, including sulfur, than other meteorite classes. According to Dr. Claeys, this makes it less likely that the meteorite’s own sulfur content was the “smoking gun.” Instead, the researchers suggest that the primary factor in the extinction was the sheer volume of fine debris blasted into the atmosphere, which blocked out the sun and stalled global ecosystems.
The Origin and Impact of the Chicxulub Meteorite
The impactor, which measured an estimated 10 to 15 kilometers (about six miles) in diameter, struck the Earth at approximately 64,000 km/h. This collision created the Chicxulub crater, now buried beneath the Yucatán Peninsula in Mexico.
While the exact origin of the meteorite remains unconfirmed, scientists believe it likely arrived from either the outer part of the asteroid belt near Jupiter or a distant, debris-heavy region of the outer Solar System. “Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were,” Dr. Claeys stated.
Frequently Asked Questions
What is a CO chondrite?
A CO chondrite, or carbonaceous chondrite of the Ornans class, is a rare type of primitive, stony meteorite that contains very few volatile elements compared to other known meteorites.
How did scientists identify the meteorite?
Researchers used highly precise nickel isotope measurements on clay samples taken from the global layer deposited 66 million years ago, which contained faint chemical traces of the vaporized impactor.
Did sulfur cause the dinosaur extinction?
While sulfur may have played a role, current findings suggest that the meteorite’s low sulfur content makes it unlikely to be the primary cause. Large amounts of atmospheric debris are now considered a more dominant factor in the extinction.
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