Researchers identify class of “oddball” meteorite that killed the dinosaurs
July 17, 2026
Earth scientists are slowly closing in on the class of impactor that caused the Cretaceous-Paleogene extinction event — new research indicates it wasn’t a garden-variety space rock.
A rare CO chondrite meteorite was the probable impactor that struck Earth 66 million years ago, wiping out 75 per cent of Earth's species, including non-avian dinosaurs.
The findings, published today in Science Advances by researchers at the University of British Columbia (UBC), Paris, Brussels and Vienna, used advanced nickel isotope analysis of samples to narrow down the composition of the deadly Cretaceous-Palaeogene meteorite.
“Carbonaceous chondrites of the Ornans class are definitely not like the typical meteors you find in museum collections,” says Dr. Philippe Claeys, who worked on the study as a visiting professor at UBC.
“A CO contains much less volatile elements—like carbon, zinc, water and particularly sulphur—than other classes of meteorites we’ve discovered so far on Earth. It doesn’t alter our theory of what caused the extinction event—but it makes it less likely that sulphur contained in the impactor was the smoking gun. The fine debris thrown into the atmosphere would have the primary factor.”
Researchers from Institut de Physique du Globe and Université de Paris conducted high-precision nickel isotope measurements of samples collected over years from a thin layer of clay created across the globe by the impact.
“This is challenging work,” adds Dr. Claeys, a professor with Vrije Universiteit Brussel currently visiting the Pacific Centre for Isotopic and Geochemical Research with Earth, Ocean and Atmospheric Sciences at UBC. “Only a minute fraction of the projectile is preserved in the planet’s KT clay layer because the entire meteorite vaporized upon impact.”
Many questions remain about the origins of the world-shattering meteorite. Potential sources include distant, debris-rich regions of the outer Solar System or even the outer area of the asteroid belt near Jupiter.
A rare impactor
Carbonaceous chondrites make up only five per cent of meteorites so far sampled on Earth. Carbonaceous chondrites of the Ornans class — CO chondrites — make up a tiny fraction of that group. They are some of the most primitive and untouched materials in the solar system.
“Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were,” says Dr. Claeys.
The Cretaceous-Paleogene impactor was roughly 10 to 15 kilometres or six miles wide. It hit at an estimated 64,000 km/h forming the massive Chicxulub crater. The impact zone is buried underneath the Yucatán Peninsula in Mexico.
