Scientists trace dinosaur-extinction asteroid to outer solar system

Scientists trace dinosaur-extinction asteroid to outer solar system
by Robert Schreiber
Berlin, Germany (SPX) Aug 23, 2024

Geoscientists from the University of Cologne have led an international research team in pinpointing the origins of the asteroid responsible for the extinction event that wiped out the dinosaurs around 66 million years ago. By examining samples from the boundary layer between the Cretaceous and Paleogene periods-a time that marked Earth's last major mass extinction-the researchers identified the asteroid's source as the outer regions of the solar system, beyond Jupiter's orbit. Their findings have been published in Science.

The Cretaceous-Paleogene mass extinction, which eradicated approximately 70 percent of Earth's species, is widely attributed to the impact of a large asteroid, roughly 10 kilometers in diameter, which struck near Chicxulub on Mexico's Yucatan Peninsula. The force of the collision vaporized both the asteroid and significant portions of Earth's crust, sending fine dust particles into the stratosphere. This dust, which spread globally, blocked sunlight, causing a prolonged "impact winter" that dramatically altered Earth's climate and halted photosynthesis for years.

The global dust fallout from the Chicxulub impact is preserved in a sediment layer found around the world, distinguished by its high concentrations of platinum-group metals. These metals, including the platinum-group element ruthenium, are rare in Earth's crust but are found in abundance in certain types of asteroids.

In a cleanroom lab at the University of Cologne's Institute of Geology and Mineralogy, scientists analyzed the isotopic composition of ruthenium from this sediment layer. "The asteroid's composition is consistent with that of carbonaceous asteroids that formed outside of Jupiter's orbit during the formation of the solar system," explained Dr. Mario Fischer-Godde, the study's lead author.

Further isotopic analysis of ruthenium from other Earth impact sites revealed that in the last 500 million years, Earth has primarily been struck by S-type asteroids from the inner solar system. In contrast, the Chicxulub impactor's carbonaceous composition, indicative of an outer solar system origin, marks it as an anomaly. "We found that the impact of an asteroid like the one at Chicxulub is a very rare and unique event in geological time," added Professor Dr. Carsten Munker, co-author of the study. "The fate of the dinosaurs and many other species was sealed by this projectile from the outer reaches of the solar system."

Research Report:Ruthenium isotopes show the Chicxulub impactor was a carbonaceous-type asteroid