Dinosaur-killing asteroid identified as rare CO chondrite meteorite
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Researchers have identified the meteorite that struck Earth 66 million years ago, killing 75% of species including nonavian dinosaurs, as a rare carbonaceous chondrite of the Ornans class (CO). The finding, published in Science Advances, narrows the impactor's composition through advanced nickel isotope analysis of the global clay layer left by the event.
The Impactor's Composition
A team from the University of British Columbia (UBC), Paris, Brussels, and Vienna used high-precision nickel isotope measurements to identify the Cretaceous-Paleogene impactor as a CO chondrite. These meteorites make up a tiny fraction of the 5% of carbonaceous chondrites found on Earth. Dr. Philippe Claeys of Vrije Universiteit Brussel noted that CO chondrites contain far fewer volatile elements like sulfur, zinc, and water than other classes.
Extinction Mechanism
The impactor, 10–15 km wide, struck at 64,000 km/h, forming the Chicxulub crater in Mexico. The fine debris thrown into the atmosphere, not sulfur from the meteorite, is now considered the primary extinction driver. The meteorite entirely vaporized upon impact, leaving only a minute fraction in the global clay layer.
Unanswered Origins
The origin of the CO chondrite remains unclear. Potential sources include the outer solar system or the asteroid belt near Jupiter. Claeys emphasized the rarity of such an impact, calling the dinosaurs 'unlucky' to be struck by such a distant projectile.
What's Next
Further studies will aim to trace the meteorite's origin using isotopic signatures from other solar system bodies. It remains uncertain whether the impactor came from the outer asteroid belt or a more distant region.
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Dinosaur-killing asteroid identified as rare CO chondrite meteorite
