News summary produced by Claude AI
Researchers from multiple international institutions have determined that a carbonaceous chondrite of the Ornans class likely caused the extinction event that eliminated approximately 75 percent of all species 66 million years ago. The research team, led by scientists from the University of British Columbia, Paris, Brussels, and Vienna, analyzed nickel isotope signatures preserved in clay deposits left at the impact site to reach their conclusions, which were published in Science Advances.
CO chondrites are exceptionally uncommon meteorite types, accounting for only a fraction of carbonaceous chondrites found on Earth. Unlike typical meteorites in museum collections, these objects contain significantly lower amounts of volatile elements including carbon, zinc, water, and particularly sulfur. This composition fundamentally changes understanding of the extinction mechanism, as it suggests that sulfur from the impactor itself was likely not the primary driver of the catastrophic event.
Instead, the research indicates that enormous quantities of fine debris propelled into the atmosphere following the impact played the dominant role in triggering widespread destruction. Scientists from the Institut de Physique du Globe and Université de Paris conducted highly precise measurements on samples collected from a thin clay layer deposited globally after the impact event. The work proved challenging, as only minuscule amounts of the original meteorite remained preserved, having largely vaporized upon striking Earth.
The meteorite’s precise origin remains unknown, though scientists believe it may have originated from the outer solar system’s debris-filled regions or from the outer asteroid belt near Jupiter. The impactor, measuring between 10 and 15 kilometers across, struck Earth at approximately 64,000 kilometers per hour and created the Chicxulub crater, now buried beneath Mexico’s Yucatán Peninsula. Researchers noted that impact by such a rare and distant object underscores the extraordinary nature of the extinction event.