A rare style of meteorite often called a CO chondrite was likely the thing that slammed into Earth 66 million years ago and triggered the extinction of about 75 percent of all species, including every non-avian dinosaur.
Researchers from the University of British Columbia (UBC), Paris, Brussels, and Vienna reached that conclusion by analyzing nickel isotopes preserved in material left behind by the Cretaceous-Paleogene impact. Their findings were published in Science Advances.
A Rare Meteorite Behind the Dinosaur Extinction
“Carbonaceous chondrites of the Ornans class are definitely not like the everyday meteors you discover in museum collections,” says Dr. Philippe Claeys, who worked on the study as a visiting professor at UBC.
“A CO incorporates much less volatile elements — like carbon, zinc, water and particularly sulfur — than other classes of meteorites we have discovered to date on Earth. It doesn’t alter our theory of what caused the extinction event — nevertheless it makes it less likely that sulfur contained within the impactor was the smoking gun. The tremendous debris thrown into the atmosphere would have the first factor.”
That difference in composition could help scientists higher understand how the impact caused such widespread destruction. Because CO chondrites contain relatively little sulfur, the brand new evidence suggests that sulfur from the meteorite itself may not have been the important driver of the catastrophe. As a substitute, enormous quantities of tremendous debris blasted into the atmosphere can have played the dominant role.
Nickel Isotopes Reveal the Impactor’s Identity
Scientists from the Institut de Physique du Globe and Université de Paris carried out highly precise nickel isotope measurements on samples gathered over a few years. The fabric got here from a skinny layer of clay deposited all over the world after the impact.
“That is difficult work,” adds Dr. Claeys, a professor with Vrije Universiteit Brussel currently visiting the Pacific Centre for Isotopic and Geochemical Research with Earth, Ocean and Atmospheric Sciences at UBC. “Only a minute fraction of the projectile is preserved within the planet’s KT clay layer because the whole meteorite vaporized upon impact.”
The worldwide clay layer incorporates only faint traces of the unique object, making it difficult to find out exactly what struck Earth. Even so, the nickel isotope signature allowed the researchers to narrow the impactor all the way down to a rare class of carbonaceous meteorite.
Where Did the Dinosaur-Killing Meteorite Come From?
The meteorite’s original source stays uncertain. It can have come from a distant region of the outer Solar System full of rocky debris, or from the outer a part of the asteroid belt near Jupiter.
Carbonaceous chondrites account for under about five percent of meteorites sampled on Earth. CO chondrites, also called carbonaceous chondrites of the Ornans class, represent only a really small portion of that group. They’re considered a few of the most primitive and least altered materials left from the formation of the solar system.
“Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were,” says Dr. Claeys.
The Chicxulub Impact
The Cretaceous-Paleogene impactor measured an estimated 10 to fifteen kilometers across, or about six miles wide. It struck Earth at roughly 64,000 km/h and created the big Chicxulub crater.
The impact site is now buried beneath Mexico’s Yucatán Peninsula.