The meteorite that wiped out the dinosaurs was a cosmic rarity.

A rare meteorite from the early solar system triggered the mass extinction that wiped out the dinosaurs 66 million years ago, according to new research. This discovery reshapes understanding of the catastrophic event that altered life on Earth dramatically, wiping out 75 percent of all species, including the dinosaurs. The Chicxulub meteorite, which struck the Earth near present-day Mexico’s Yucatán Peninsula, was identified as a carbonaceous chondrite, a type of meteorite containing high levels of carbon. Such meteorites make up just two to three percent of all known meteorites, making them exceptionally rare. Researchers have long suspected that the impact caused a global winter effect, with dust blocking sunlight and volatile substances such as sulfur and carbon dioxide drastically altering climate and ocean chemistry. The theory linking the mass extinction to the Chicxulub impact was proposed in 1980 by geologist Walter Alvarez and his father, Nobel Prize-winning physicist Luis Alvarez. They based their hypothesis on unusually high concentrations of iridium found in rock layers marking the boundary between the Cretaceous and Paleogene periods. Iridium is more common in space rocks than on Earth, suggesting a massive extraterrestrial object had collided with the planet. About a decade later, scientists discovered the Chicxulub crater, measuring 180 kilometers in diameter, confirming the location of the impact. Since then, researchers have sought to learn more about the nature of the celestial body responsible for this cataclysmic event. An international team led by impact researcher Christian Köberl from the University of Vienna has now determined the meteorite's origin and composition. By analyzing core samples from the Chicxulub crater and examining ejecta layers, deposits formed when material from the impact site was thrown into the atmosphere, scientists found higher concentrations of extraterrestrial materials compared to the crater itself. These layers contain isotopes and chemical compositions that help identify the meteorite's type and origin. In particular, the study focused on nickel isotopes found in ejecta layers around the world and compared them to different types of carbonaceous chondrites. According to findings published in Science Advances, the Chicxulub meteorite matched the composition of a CO-chondrite, a specific type of carbonaceous chondrite. CO-chondrites are relatively dry and contain fewer volatile elements and water compared to other carbonaceous chondrites. They originate from the outer regions of the asteroid belt, close to Jupiter. When these bodies' orbits are disturbed, they can be redirected toward the inner solar system, eventually colliding with planets like Earth. Philippe Claeys, a colleague of Köberl from the Vrije Universiteit in Brussels, described the work as challenging. He noted that only a tiny fraction of the meteorite remained in the KT clay layer, the geological layer marking the Cretaceous, Paleogene boundary, because the entire meteorite likely vaporized upon impact. The study highlights how the Chicxulub meteorite was not only rare but also came from a region of the solar system far removed from Earth. Its journey through space and eventual collision with our planet underscores the unpredictable nature of cosmic events and their potential to reshape life on Earth. Researchers continue to analyze samples from various locations, including Denmark, where some of the study's samples were collected. These analyses provide further insights into the meteorite's composition and its path through the solar system before striking Earth. Scientists are now working to understand better how such rare meteorites could have been redirected from the asteroid belt to collide with Earth. Their findings contribute to broader discussions about the frequency of large impacts and their role in shaping planetary history.