The asteroid that wiped out the dinosaurs 66 million years ago originated from the outer solar system, according to a new study by scientists at the University of Cologne. By analyzing geochemical evidence from the Chicxulub crater in Mexico, the researchers revealed that the impactor was a carbon-rich asteroid from beyond Jupiter’s orbit.
The Cretaceous-Paleogene (K-Pg) extinction event, which occurred approximately 66 million years ago, was one of Earth’s five major mass extinctions, wiping out over 60% of all species, including non-avian dinosaurs. Since the 1980s, a growing body of evidence has suggested that this extinction event was caused by a city-sized object colliding with Earth. The impact would have thrown vast amounts of sulfur, dust, and soot into the atmosphere, blocking sunlight and causing global temperatures to plummet.
To determine the nature and origin of this impactor, the research team collected K-Pg rock samples from three locations and compared them to samples from eight other impact sites over the past 3.5 billion years. The team focused on the isotopes of the metal ruthenium, which is extremely rare in Earth rocks and has seven stable isotopes. The study found that the isotopic composition of ruthenium in the impactor closely matched that of carbon-rich asteroids from the outer solar system, but not with those from the inner solar system.