2024-08-16 14:20:12
66 million years ago, an asteroid roughly 10-15 kilometers wide slammed into Mexico’s Yucatan Peninsula, triggering a global cataclysm that wiped out about three-quarters of the planet’s species and ended the age of the dinosaurs. This is a turning point in the history of life on Earth. Now scientists provide an answer to the question of where this asteroid originated, Reuters and AFP report, referring to a publication in the journal “Science”.
The impact shatters the asteroid and scatters its debris across the globe. They are still found in a global layer of clay deposited after that fateful day. A new analysis of the debris resolves a long-standing debate about the nature of the asteroid, showing it was of a type that originated beyond Jupiter in the outer Solar System.
Based on the composition of the debris, scientists determined that it was a K-class carbonate (carbon) asteroid, so named because of its high concentration of carbon. The research rules out the possibility that the impact was caused by a comet or that the debris layer was deposited by volcanism, as some have suggested.
“A projectile originating from the outskirts of the solar system sealed the fate of the dinosaurs,” said Mario Fischer-Goede, a geochemist at the University of Cologne in Germany and lead author of the study.
The impact at the end of the Cretaceous period carved the Chicxulub Crater, 180 kilometers wide and 20 kilometers deep. The clay layer is rich in metals, including iridium, ruthenium, osmium, rhodium, platinum and palladium, which are rare on Earth but common in asteroids.
The researchers focused on ruthenium—specifically, the ratio of its isotopes present in the clay layer. Isotopes are atoms of the same element with slightly different masses due to different numbers of subatomic particles called neutrons.
Ruthenium has seven isotopes, three of which are particularly important to the results of the study. Its isotope ratio matches that of other known carbon asteroids, writes BTA.
K-class asteroids, which are among the oldest objects in the Solar System, are the most common type, followed by C-class silicate (rock) asteroids and the rarer M-class metallic asteroids.
Differences in the composition of asteroids are due to how far from the Sun they formed.
Having formed in the outer part of the Solar System, the asteroid probably later migrated inward to become part of the main asteroid belt between Mars and Jupiter before somehow being sent towards Earth, possibly as a result of collision, explains Fischer-Goede.
“All meteorites falling on our planet, which are fragments of K- and C-class asteroids, originate from the asteroid belt. So it seems most likely that the asteroid that hit the Yucatan at the end of the Cretaceous period also originated from it,” says the scientist .
The researchers analyzed samples from five other asteroid impacts, dating from 37 million to 470 million years ago, and found that they were all C-class, illustrating the rarity of impact with a carbonaceous asteroid.
Dinosaurs had long ruled the Earth, but with the exception of their avian lineage, were wiped out after the impact, as were flying reptiles called pterosaurs, large marine reptiles, and other marine life, including many species of plankton.
Mammals survived, allowing them to dominate the land and setting the stage for the emergence of our species about 300,000 years ago.
“I think that if it wasn’t for this event, life on our planet would probably have developed in a completely different way,” says Mario Fischer-Goede.