A Rare Space Rock May Have Been the Dinosaur Slayer

When you picture the meteor that wiped out the dinosaurs, you probably imagine a massive, fiery boulder blazing across the sky. Turns out, the actual rock might have been something far rarer – a CO chondrite, a type of carbon‑rich meteorite that we barely ever find on Earth.

A multinational crew of geochemists from the University of British Columbia, Paris, Brussels and Vienna sifted through tiny traces of the impact – a thin, worldwide layer of clay that settled after the impact 66 million years ago. By measuring the ratios of nickel isotopes in that clay, they were able to fingerprint the projectile, much like a forensic lab matches DNA.

“Carbonaceous chondrites of the Ornans class are definitely not the run‑of‑the‑mill space rocks you see in museums,” explains Dr Philippe Claeys, a visiting professor at UBC. “They contain far less volatile stuff – think sulfur, zinc, even water – than the more common meteorites.” This low‑sulfur signature throws a wrench into the old idea that the asteroid’s own sulfur spewed into the atmosphere and poisoned the planet.

Instead, the researchers argue, the real culprit was the sheer amount of fine debris hurled high into the sky. Those microscopic particles would have blocked sunlight, cooled the climate and crippled photosynthesis – a global blackout that could have sealed the fate of non‑avian dinosaurs.

The team’s nickel isotope work was no easy feat. Only a microscopic sliver of the original object survived the cataclysmic blast; the rest vaporized in an instant. Still, the isotopic fingerprint was distinct enough to point squarely at a CO chondrite, which makes up less than five percent of all meteorites that ever land on Earth, and an even smaller slice of that group.

Where did this exotic rock come from? That remains a mystery. It could have been flung outward from the distant reaches of the outer Solar System, or perhaps it originated near the outer edge of the asteroid belt, close to Jupiter’s massive gravitational tug.

Whatever its birthplace, the fact that such an uncommon projectile struck Earth underscores how unlucky the dinosaurs were. The impactor itself was probably 10–15 km wide, slammed into the planet at around 64 000 km/h, and carved the massive Chicxulub crater beneath today’s Yucatán Peninsula.

In short, a tiny grain of nickel in a clay sheet tells a big story: the dinosaurs’ demise may have been driven less by a chemical poison and more by a planet‑wide dust storm, courtesy of a rare, ancient space rock.