Dinosaur-killing asteroid Chicxulub came from beyond Jupiter: study

The so-called Chicxulub impactor was a carbonaceous asteroid that formed beyond the orbit of Jupiter, according to a new article in the journal Science.

Ankylosaurus magniventrisa large armored dinosaur species, witnesses the impact of an asteroid that fell on the Yucatan Peninsula 66 million years ago. Photo credit: Fabio Manucci.

About 66 million years ago, a 10-kilometer-wide asteroid crashed into Earth near the small town of Chicxulub in what is now Mexico.

The impact released incredible amounts of climate-changing gases into the atmosphere and triggered a chain of events that led to the extinction of the dinosaurs and 75% of all life on the planet.

Evidence includes high concentrations of platinum group elements (PGEs) such as iridium, ruthenium, osmium, rhodium, platinum and palladium in the Cretaceous-Paleogene interfaces, which are rare on Earth but common in meteorites.

These elevated PGE levels were detected worldwide, suggesting that the impact scattered debris around the world.

While some have suggested large-scale volcanic activity in the Deccan Traps igneous province of India as an alternative source of PGEs, the specific PGE ratios at the Cretaceous-Paleogene boundary are consistent with asteroid impacts rather than volcanic activity.

However, much is still unclear about the nature of the Chicxulub impact body – its composition and its extraterrestrial origin.

To answer these questions, Dr. Mario Fischer-Gödde from the University of Cologne and his colleagues measured ruthenium isotopes in samples taken from three sites at the Cretaceous-Paleogene boundary.

For comparison, they also analyzed samples from five other impacts that occurred between 36 and 470 million years ago; samples from impact sphere layers that were 3.5 to 3.2 billion years old; and samples from two carbonaceous meteorites.

They found that the isotopic signatures of ruthenium in the Cretaceous-Paleogene samples were consistent and largely matched those of carbonaceous chondrites, not those of Earth or other types of meteorites. This suggests that the Chicxulub impact body likely came from a carbonaceous asteroid that formed in the outer solar system.

The isotopic signatures of the other five impact structures are more consistent with those of silicate asteroids that formed closer to the Sun.

The ancient samples from the spherule layer are consistent with impacts of carbonaceous asteroids during the final phase of Earth's accretion.

“The composition of the asteroid is consistent with that of carbonaceous asteroids that formed outside the orbit of Jupiter during the formation of the solar system,” said Dr. Fischer-Gödde.

“We have found that the impact of an asteroid like Chicxulub is a very rare and unique event in geological time,” said Professor Carsten Münker of the University of Cologne.

“The fate of the dinosaurs and many other species was sealed by this projectile from the outer reaches of the solar system.”

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Mario Fischer-Gödde et al. 2024. Ruthenium isotopes show that the Chicxulub impact body was a carbonaceous asteroid. Science 385 (6710): 752-756; doi: 10.1126/science.adk4868