According to new isotope research published on July 17, 2026, in Science Advances, the 10- to 15-kilometer space rock that struck the modern-day Yucatán Peninsula 66 million years ago was an exceptionally rare carbonaceous chondrite belonging to the Ornans class. Lead author Georgy Makhatadze led an international team from the University of British Columbia, alongside researchers from Paris, Brussels, and Vienna, examining clay layers from the Cretaceous-Paleogene (K-Pg) boundary across global sites to reconstruct the composition of the impactor that triggered the mass extinction of non-avian dinosaurs.
Decoding the Impactor: Why This Carbonaceous Chondrite Matters
Carbonaceous meteorites account for approximately 5 percent of all meteorites found on Earth, and the CO-variant identified in this study represents only a small fraction of that rare group. These meteorites feature small, round granules formed in the early solar system. Because the original impactor completely vaporized upon hitting Earth at roughly 64,000 km/u—more than 50 times the cruising speed of a passenger jet—the research team analyzed nickel isotopes acting as chemical fingerprints in global clay layers.
This geochemical approach builds directly upon a 2024 ruthenium study that originally traced the impactor’s distant origin to outside the orbit of Jupiter. Philippe Claeys, a professor at the Vrije Universiteit Brussel and guest professor at the University of British Columbia, notes that these rare carbonaceous chondrites diverge sharply from standard meteorites typically housed in museum collections.
Did you know?
The Chicxulub impactor struck Earth with a diameter estimated between 10 and 15 kilometers, unleashing a cataclysm that wiped out roughly 75 percent of all species on the planet.
Shifting Scientific Focus: Fine Silicate Dust Over Sulfur
Earlier extinction models heavily emphasized sulfur released directly from the impactor. However, the new data shows that CO-chondrites contain roughly half the sulfur found in previously studied CM- and CR-variant meteorites. Furthermore, elements like carbon, zinc, and water also appear in significantly lower quantities within this specific group of space rocks.
This chemical deficit directs scientific attention toward fine silicate dust. These microscopic mineral particles, hurled into the atmosphere by the devastating collision, likely played a far more dominant role in driving the mass extinction than the meteoritic sulfur alone. Understanding the exact lethality of the event requires looking closely at what the impact blasted into the atmosphere.
The Element of Cosmic Chance
The statistical probability of an identical object striking Earth again remains low. Claeys emphasizes that an impact driven by such a rare object originating from a distant part of the solar system highlights the sheer bad luck faced by Earth’s ecosystems 66 million years ago.
Earth’s history shows that the exact chemical makeup of an incoming celestial body can significantly determine the subsequent ecological chain reaction. Analyzing trace chemical spoor in ancient geological formations helps scientists determine which specific materials trigger the greatest planetary devastation, moving beyond the simple confirmation of an ancient impact.
Frequently Asked Questions
What type of meteorite caused the dinosaur extinction?
According to the 2026 Science Advances study led by Georgy Makhatadze, the Chicxulub impactor was a rare CO-chondrite belonging to the Ornans class of carbonaceous meteorites, originating from beyond the orbit of Jupiter.
How fast was the asteroid traveling when it hit Earth?
The 10- to 15-kilometer-wide space rock struck the Yucatán region at an estimated speed of approximately 64,000 km/u.
Why is sulfur no longer considered the primary kill mechanism?
CO-chondrites contain roughly half the sulfur of other carbonaceous meteorite types, shifting researchers’ focus toward fine silicate dust as the major driver of the K-Pg boundary mass extinction.
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