Asteroid That Caused Mass Extinction Was Identified
Researchers determined the 66-million-year-old impactor was a carbonaceous chondrite, shifting the extinction theory.
Updated on Sept. 21, 2026 in Geology
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Scientists identified the asteroid that struck the Yucatan Peninsula 66 million years ago as a CO-class carbonaceous chondrite. This finding challenges previous extinction theories by suggesting atmospheric debris, not sulfur-driven collapse, triggered the event.
Why it matters
This reclassification shifts the scientific understanding of the mass extinction that eliminated 75% of Earth's species by highlighting the role of solar-blocking debris. It suggests the impactor originated in the outer solar system near Jupiter, rather than the inner asteroid belt.
The 10 to 15 kilometer wide object struck Earth at 64,000 km/h. Analysis of nickel isotopes in sediment indicates it was a carbonaceous chondrite, a class known for significantly lower sulfur and volatile element content than previously hypothesized asteroid types.
The details
Researchers determined the chemical makeup by isolating nickel isotopes preserved in a global clay layer that dates to the time of impact. Unlike other asteroid types, CO-class carbonaceous chondrites lack the high sulfur levels required for significant sulfur-driven cooling. Instead, the team concluded that microscopic debris ejected into the upper atmosphere blocked solar radiation, causing the rapid collapse of biological systems.
Timeline
66 million years ago: An asteroid struck the Yucatan Peninsula.
The Tech Race
This finding updates the long-standing understanding of the Cretaceous-Paleogene extinction event. It replaces the prevailing sulfur-driven climate model with a mechanism centered on debris-driven solar blockage.
This research clarifies the planetary-scale physics behind the extinction of 75% of species on Earth. It provides a more accurate chemical profile for scientists studying asteroid impacts and their potential to disrupt global atmospheres.
The takeaway
The study confirms that the mass extinction was triggered by material from the outer asteroid belt rather than local sources. Future research should look for additional isotopic evidence in deep-sea cores to refine the timeline of the atmospheric debris cloud.
Further reading
For more on the history of Earth's crust and impact events, visit the Geology section.
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