Lead author Georgy Makhatadze led an international research team from the University of British Columbia. Co-authors from institutions in Paris, Brussels, and Vienna joined the study. The group conducted high-precision isotopic measurements to pinpoint the impactor’s chemical classification. Chemical fingerprinting through isotopic analysis The Chicxulub impactor struck present day Yucatán Peninsula in Mexico at 40,000 miles per hour (64,000 kilometers per hour). The collision carved out a crater over 110 miles across. It triggered the extinction of roughly 75% of all living species, including all non-avian dinosaurs. The extreme energy of the collision vaporized the 6-to-9-mile-wide asteroid. Consequently, physical fragments of the object no longer exist. To determine the asteroid’s composition, the team extracted samples from the global Cretaceous-Paleogene (K-Pg) boundary layer. These included high-purity clay deposits from Stevns Klint, Denmark. Researchers measured stable nickel isotope ratios within the iridium-rich sediment. Different meteorite groups preserve distinct isotopic signatures established during early solar system formation. Consequently, these measurements allowed the team to match the impact debris to CO carbonaceous chondrites. Carbonaceous chondrites make up approximately 5% of all meteorites recovered on Earth. Also, the CO (Ornans-type) subtype represents a small fraction of that already rare group. Reevaluating the atmospheric extinction mechanism CO chondrites rank among the most primitive known materials in the solar system, preserving primordial chemical ratios. However, compared to other carbonaceous meteorites, they contain lower concentrations of volatile elements; carbon, zinc, water, and sulfur all fall well below typical levels. This low sulfur concentration modifies current models regarding the primary drivers of post-impact climate change: - Volatile contribution: previous theories assumed sulfur vaporized directly from the asteroid drove global cooling. - Refined climate drivers: the low sulfur mass fraction shows the asteroid contributed less sulfur than previously calculated. - Silicate dust and target rock: the findings shift scientific focus