Asteroid's Nickel Signature Reveals Dinosaur Killer's Origin

An international team of scientists determined the asteroid that triggered the Cretaceous-Paleogene extinction event 66 million years ago was likely a CO chondrite, a rare type of meteorite, by analyzing nickel isotopes preserved in boundary clay layers across Denmark, Spain, and Italy. Researchers examined samples from five locations to compare the nickel composition with that of various carbonaceous meteorites.

The analysis revealed a close match with CO chondrites, though a closely related, unconfirmed type called CT chondrite remains a possibility. This finding refines understanding of the asteroid's composition and suggests it contained less sulfur than previously thought, potentially shifting focus from sulfur-induced climate change to the role of long-lasting silicate dust in causing the extinction.

The research builds on a 2024 study that already identified the asteroid as carbonaceous and originating beyond Jupiter. Scientists continue to investigate the asteroid's trajectory and the precise source within the outer solar system. Understanding the impactor’s origin helps to contextualize the catastrophic event that wiped out approximately 75 percent of life on Earth.