What Suddenly Ended the Age of Dinosaurs? Scientists Find the Answer

Scientists have discovered new evidence that the rock that crashed into Earth 66 million years ago, bringing an abrupt end to the age of dinosaurs, was a bit strange.

The nature of the object, known as Chicxulub, has been the subject of much debate, including a long-running argument over whether it was a comet or an asteroid. But in recent years, there has been growing evidence that Chicxulub, which is about 6 miles (9.65 kilometers) wide, belongs to a family of asteroids that formed outside the orbit of Jupiter and rarely collide with Earth.

Now, a team led by Mario Fischer-Gudi, a researcher at the University of Cologne in Germany, has strengthened this hypothesis with the help of the rare chemical element ruthenium. Ruthenium is abundant in asteroids but extremely rare in Earth’s crust, making it a useful tool for tracking past space rock impacts. The team searched for ruthenium isotopes in the geological remains of the Chicxulub impact.

The results revealed a uniform signature across the global debris layer left behind by the impact, known as the Cretaceous-Paleogene (K-Pg) boundary. That signature matches perfectly with the composition of a group of space rocks known as carbonaceous asteroids because of their high carbon content, according to a study published Thursday (8/15) in the journal Science.

“It’s the nail in the coffin,” said Dr. Fischer-Judy. “The ruthenium isotope signature we’re measuring can’t be anything other than a carbonaceous asteroid.”

Silicate asteroids that collide with Earth typically come from the asteroid belt. But it’s still unclear how a giant carbonaceous asteroid ended up on a collision course with our planet. One possible origin is a group of carbonaceous asteroids that today exist on the outer edge of the asteroid belt. Although these rocks originally formed beyond Jupiter, scientists think that gravitational instability in the early solar system pushed them inward to their current location.

With information from the New York Times