Researchers have identified the asteroid that killed the dinosaurs 66 million years ago as a rare CO chondrite, a primitive meteorite with minimal sulfur, according to a study published in 2026. The findings, led by Philippe Claeys, reveal how the impact’s debris and atmospheric effects caused mass extinction.
The Rare Meteorite Behind the Dinosaur Extinction
The asteroid that wiped out the dinosaurs, known as Chicxulub, was a CO chondrite—a type of meteorite so rare that it makes up just 5% of all samples found on Earth. This discovery, published in *Science Advances* in 2026, resolves a decades-old debate about the asteroid’s composition and origins. CO chondrites are among the most primitive materials in the solar system, containing minimal volatile elements like sulfur and water.
Nickel Isotopes and the Impact’s Legacy
Scientists used nickel isotopes to trace the asteroid’s origin, comparing samples from the KT boundary layer—formed by the impact—to known meteorite types. The results pointed to a CO chondrite, a rare class of carbonaceous meteorites that likely formed in the outer solar system. Only a minute fraction of the projectile is preserved in the planet’s KT clay layer because the entire meteorite vaporized upon impact,
Claeys explained.
The research team faced challenges due to the scarcity of nickel in the clay and contamination from terrestrial materials. By isolating tiny quantities and analyzing them with a high-precision mass spectrometer in Paris, they confirmed that the asteroid’s composition aligned most closely with CO chondrites. This is part of our efforts to characterize the projectile that impacted in Yucatan 66 million years ago,
Claeys said, highlighting the importance of narrowing down the asteroid’s origin to distant solar system regions or the outer asteroid belt near Jupiter.
A Drier Asteroid, A Dustier Extinction
While the asteroid’s low sulfur content reduces its role in climate-altering gases, the impact’s catastrophic effects stemmed from debris and thermal radiation. The fine debris thrown into the atmosphere would have been the primary factor,
Claeys noted. The collision vaporized sulfur-rich rocks in the Yucatán, creating a “nuclear winter” that blocked sunlight and devastated ecosystems.
Despite these insights, many questions remain. The study’s 2026 publication in *Science Advances* raises new queries about the asteroid’s exact origin and the interplay between its composition and the extinction’s scale. Future research will focus on refining models of atmospheric debris and its global effects. We are trying to document where it came from,
Claeys said, underscoring the ongoing effort to piece together the final moments of the Cretaceous period.
For now, the findings reinforce the role of cosmic impacts in shaping Earth’s history. As Claeys put it, Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were.
The study’s methods—using nickel isotopes to analyze vanished space rocks—set a new standard for understanding ancient collisions, offering a glimpse into the forces that have repeatedly altered life on Earth.
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