The asteroid, called the Chicxulub impactor, was a carbonaceous asteroid that formed outside the orbit of Jupiter. New Paper Published in the journal Science.
Ankylosaurus magniventrisA Tyrannosaurus, a type of large armored dinosaur, witnessed the impact of an asteroid that fell on the Yucatan Peninsula 66 million years ago. Image by Fabio Manucci.
About 66 million years ago, a 10-kilometer-wide asteroid struck Earth near what is now a small town called Chicxulub in Mexico.
This impact released incredible amounts of climate-changing gases into the atmosphere, setting off a chain of events that led to the extinction of the non-avian dinosaurs and 75% of life on Earth.
Evidence includes the presence of high concentrations of platinum group elements (PGE) in the Cretaceous-Paleogene boundary layer, including iridium, ruthenium, osmium, rhodium, platinum, and palladium, which are rare on Earth but common in meteorites.
These elevated PGE levels have been found worldwide, suggesting that the impact spread debris around the world.
Some have proposed large-scale volcanism in the Deccan Traps igneous province of India as an alternative source of PGEs, but the specific PGE ratios at the Cretaceous-Paleogene boundary are more consistent with an asteroid impact than volcanism.
However, little is known about the nature of the Chicxulub impactor, including its composition and 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-Palaeogene boundary.
For comparison, the team also analysed samples from five other impacts that occurred between 36 million and 470 million years ago, an ancient impact spherule from 3.5 to 3.2 billion years ago, and two carbonaceous meteorites.
The researchers found that the ruthenium isotope signature of samples taken from the Cretaceous-Paleogene boundary was uniform and matched very closely to that of carbonaceous chondrites rather than those from Earth or other types of meteorites, suggesting that the Chicxulub impactor likely came from a carbonaceous-type asteroid that formed in the outer solar system.
The other five impact structures have isotopic signatures more consistent with silicic asteroids that formed closer to the Sun.
The ancient spherulitic samples are consistent with a carbonaceous asteroid impact during the final stages of Earth's accretion.
“The composition of this asteroid is consistent with that of carbonaceous asteroids that formed outside Jupiter's orbit during the formation of the solar system,” Dr Fischer-Gödde said.
“Asteroid impacts like Chicxulub turn out to be very rare and unique events in geological time,” said Professor Carsten Müncher from the University of Cologne.
“The fate of the dinosaurs and many other species was sealed by this object that came from the outer solar system.”
_____
Mario Fischer-Gedde others2024. Ruthenium isotopes indicate that the Chicxulub impactor was a carbonaceous asteroid. Science 385 (6710): 752-756; doi: 10.1126/science.adk4868
Source: www.sci.news
