Scientists Zero In on the Meteorite That Ended the Age of Dinosaurs

It’s hard to imagine a single rock being responsible for the demise of the mighty dinosaurs, yet that’s exactly what happened about 66 million years ago. The impact created the 180‑kilometre‑wide Chicxulub crater buried beneath the Yucatán Peninsula, and the shockwaves that followed erased roughly three‑quarters of life on Earth.

Fast‑forward to today, and a group of researchers from Canada, Belgium, Austria and Mexico think they finally know what kind of space rock caused the catastrophe. In a paper debuting in Science Advances, they report that the impactor most likely belonged to a very uncommon class of meteorites called carbonaceous (CO) chondrites.

These stones aren’t your garden‑variety meteors that end up in a museum drawer. CO chondrites are some of the most primitive, least‑altered leftovers from the birth of the Solar System, making up only about five percent of all meteorites that fall to Earth – and the Ornans subgroup, to which the study points, is an even tinier slice of that pie.

How did the scientists arrive at this conclusion? Post‑doctoral researcher Georgy V. Makhatadze and his colleagues dug into the fine‑grained clay that settled across the globe right after the impact. By measuring subtle variations in the ratios of nickel isotopes—a technique that requires laboratory equipment the size of a small room—they could compare the impact’s chemical fingerprint with that of known meteorite samples.

The match, surprisingly, lined up with the signature of CO chondrites. That suggests the projectile may have originated in the outer reaches of the Main Asteroid Belt, the distant Kuiper Belt, or another debris‑rich zone far from the Sun.

“Carbonaceous chondrites of the Ornans class are definitely not like the typical meteors you see in museum collections,” explains Dr. Philippe Claeys, a co‑author from the University of British Columbia. “They contain far less carbon, zinc, water and especially sulphur. That doesn’t overturn the extinction story, but it does make sulphur‑driven climate effects less likely – the dust and debris lofted into the atmosphere were probably the real killers.”

While many mysteries still hover around the Chicxulub event – such as the exact timing of volcanic activity versus impact, or the role of a possible tsunami – this study trims down the list of suspects considerably. Knowing the type of rock that slammed into Earth could help refine models of future impact hazards and, perhaps, guide planetary‑defence strategies.

So, the next time you picture a gigantic asteroid hurtling toward our planet, picture something a bit more exotic than a simple iron ball: a fragile, ancient, carbon‑rich pebble that traveled billions of kilometres before rewriting the story of life on Earth.