The dinosaur extinction story gets weirder. Scientists dug into the dirt again. They looked at the debris left behind 66 million years ago. Specifically, the nickel.
The findings suggest the killer rock was not your average space trash. It was a CO chondrite. An exceptionally rare, primitive type of carbonaceous chondrite. The Ornans type, to be precise.
Most people know carbonaceous chondrites. They are ancient. Wet. Dirty with carbon. But CO chondrites? They are outliers. They make up a sliver of that already small slice of meteorites. Like 5% of sampled falls. This sub-group is a tiny fraction of that 5%.
Finding one? Pure luck. Or in the dinosaur case. Unlucky.
What is a CO Chondrite and why does it matter for the Chicxulub Impact
To understand why this matters, you have to look at what these rocks lack. Professor Philippe Claeys from Vrije Universiteit put it plainly. They don’t look like the museum pieces.
“A CO contains much less volatile elements,” he explained. We are talking about zinc. Carbon. Water. And critically, sulfur.
Sulfur was supposed to be the smoking gun. The theory went like this: the asteroid hit. Sulfur vaporized. Acid rain followed. Dinosaurs choked. Now, the nickel isotope data tells us that might not be the primary driver. If the rock itself had very little sulfur to begin with, then the atmosphere got its toxic cocktail from elsewhere.
The fine debris thrown into the atmosphere [was] the primary factor.
It wasn’t just the asteroid’s chemical makeup. It was the vaporization. The clay layer across the globe, the K-T boundary, holds the answer. Claeys and his team measured nickel isotopes in this thin slice of history.
It was hard work. “Only a minute fraction of the projectile is preserved,” Claeys noted. The meteorite vaporized completely. Everything we know comes from the microscopic remnants left in that clay.
Why nickel isotopes reveal the true origin of the killer asteroid
How do you track down a rock that turned into dust 66 million years ago? You trace the nickel.
Nickel isotopes act like a fingerprint. They vary between different classes of asteroids. By analyzing samples collected globally from the Chicxulub clay layer, researchers matched the signature to CO chondrites.
This narrows the search for where the rock came from.
The impactor was massive. Roughly 10 to 12 km in diameter. Maybe up to 15 km. It slammed into Earth at a estimated 64,00 km/h. The resulting crater sits under the Yucatán Peninsula in modern-day Mexico. Buried deep.
The source of the rock? Likely far away. Distant regions of the outer Solar System. Or the outer asteroid belt, near Jupiter’s gravitational grip. These are debris-rich areas. Quiet places. Until that day.
Being hit by such a rare projectile underscores a cold fact. The dinosaurs weren’t just unlucky. They were statistically improbable victims. A one-in-a-million shot from the deep dark.
The study lands in Science Advances. Published in 2026. Georgy V. Makhatadaze et al. lay out the isotope data. It changes the chemistry of the apocalypse slightly. Less asteroid sulfur. More atmospheric debris. The death sentence was sealed anyway. But the signature is now clearer.
We used to think it was a typical meteorite. Now we know it was an oddball. A CO chondrite from the void. The fine detail changes the narrative. Not the outcome.
