The so-called Chicxulub impactor was a carbonaceous-type asteroid that had formed beyond the orbit of Jupiter, according to a new paper published in the journal Science.
About 66 million years ago, a 10-km-wide asteroid crashed into Earth near the site of the small town of Chicxulub in what is now Mexico.
The impact unleashed an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of non-avian dinosaurs and 75% of life on the planet.
Evidence includes high levels of platinum-group elements (PGEs) like iridium, ruthenium, osmium, rhodium, platinum, and palladium in Cretaceous-Paleogene boundary layers, which are rare on Earth but common in meteorites.
These elevated PGE levels have been found globally, suggesting the impact spread debris worldwide.
While some propose large-scale volcanic activity from the Deccan Traps igneous province in India as an alternative source of PGEs, the specific PGE ratios at the Cretaceous-Paleogene boundary align more with asteroid impacts than volcanic activity.
However, much about the nature of the Chicxulub impactor — its composition and extraterrestrial origin — is poorly understood.
To address these questions, Dr. Mario Fischer-Gödde from the University of Cologne and his colleagues measured ruthenium isotopes in samples taken from three Cretaceous-Paleogene boundary sites.
For comparison, they also analyzed samples from five other impacts that occurred between 36 million to 470 million years ago; samples from ancient 3.5-billion- to 3.2-billion-year-old impact spherule layers; and samples from two carbonaceous meteorites.
They found that the ruthenium isotope signatures in samples from the Cretaceous-Paleogene boundary were uniform and closely matched those of carbonaceous chondrites, not Earth or other meteorite types, suggesting that the Chicxulub impactor likely came from a carbonaceous-type asteroid that formed in the outer Solar System.
The five…
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