Des chercheurs identifient la classe de météorite " bizarre " qui a tué les dinosaures

Researchers have identified a rare type of meteorite, known as a CO chondrite, as the likely cause of the mass extinction event that wiped out approximately 75% of Earth’s species around 66 million years ago. This discovery, published in Science Advances, suggests that the meteorite responsible for the Cretaceous-Paleogene (K-Pg) boundary event was an unusual and uncommon type, significantly altering previous assumptions about its composition and potential effects. The study, led by researchers from the University of British Columbia, along with institutions in Paris, Brussels, and Vienna, analyzed samples from the global clay layer formed by the impact. Using advanced nickel isotope analysis, they determined that the meteorite belonged to the CO chondrite class, which is extremely rare among meteorites found on Earth. These types of meteorites contain very low levels of volatile elements such as carbon, zinc, water, and especially sulfur compared to more common meteorite classes. Dr. Philippe Claeys, a visiting professor at the University of British Columbia and co-author of the study, noted that CO chondrites are unlike the typical meteorites displayed in museums. “They are some of the most primitive and untouched materials in the solar system,” he explained. “Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were.” The meteorite that struck Earth was estimated to be between 10 and 15 kilometers in diameter, traveling at an astonishing speed of approximately 64,000 kilometers per hour. The collision created the massive Chicxulub crater, located beneath the Yucatán Peninsula in Mexico. The energy released during the impact was equivalent to billions of atomic bombs, triggering a cascade of environmental changes that led to the extinction of non-avian dinosaurs and many other species. The team’s findings challenge earlier theories that suggested sulfur content in the meteorite played a central role in the extinction event. Instead, they propose that the fine debris ejected into the atmosphere was the primary factor contributing to the ecological collapse. “It doesn’t alter our theory of what caused the extinction event, but it makes it less likely that sulfur contained in the impacter was the smoking gun,” Claeys added. The origins of the meteorite remain uncertain, with possibilities ranging from the outer solar system to the asteroid belt near Jupiter. These locations are known for containing debris-rich regions, making them plausible sources for such a rare type of meteorite. However, further research will be needed to confirm these hypotheses. The study highlights the importance of understanding the composition of extraterrestrial objects, as their characteristics can provide critical insights into past catastrophic events. The research team continues to analyze additional samples from the K-Pg boundary layer, hoping to uncover more clues about the meteorite’s journey through space and its ultimate impact on Earth. The implications of this discovery extend beyond paleontology and planetary science. By refining models of past impact events, scientists can better assess the risks posed by future cosmic threats. As the research unfolds, new data may reshape our understanding of how life on Earth has been shaped by celestial collisions throughout history.