The asteroid that wiped out the dinosaurs 66 million years ago belonged to a rare and unusual class of meteorite, according to new research led by Dr. Philippe Claeys, a visiting professor at the University of British Columbia also affiliated with the Vrije Universiteit Brussel.
Using high-precision nickel isotope analysis of the globally distributed clay layer marking the boundary between the Cretaceous and Paleogene periods, researchers identified the Chicxulub impactor as a CO chondrite — a member of the Ornans class. Carbonaceous chondrites make up only about 5 percent of all meteorites that reach Earth, and CO chondrites represent a tiny fraction even within that already-rare group, making the impactor an unusual specimen among the objects that have struck the planet.
The measurements, carried out by researchers at the Institut de Physique du Globe and Université de Paris, also showed that CO chondrites contain less of the volatile elements — carbon, zinc, water, and sulphur — than other meteorite classes. That finding makes the once-popular theory that sulphur released by the impact drove the mass extinction less likely. Instead, researchers now see fine atmospheric debris thrown up by the impact as the primary mechanism that blocked sunlight and triggered the extinction of roughly 75 percent of species on Earth, including the non-avian dinosaurs.
The impactor is estimated to have been 10 to 15 kilometers (6 to 9 miles) wide and to have struck at roughly 64,000 kilometers per hour, carving out the Chicxulub crater beneath what is now Mexico’s Yucatán Peninsula.
Journal: Science Advances
Article Title: “The origin of Cretaceous-Palaeogene impactor revealed by nickel isotopes”
DOI: 10.1126/sciadv.aef4858
Publication Date: 17-Jul-2026
Source: EurekAlert