A rare type of meteorite, known as a CO chondrite, may have struck Earth 66 million years ago, leading to the extinction of around 75% of all species, including non-avian dinosaurs.
Researchers at the University of British Columbia (UBC), along with teams from Paris, Brussels, and Vienna, reached this groundbreaking conclusion by analyzing nickel isotopes preserved in materials from the Cretaceous-Paleogene collision. Their findings mark significant scientific progress.
The Unique Meteorite Behind Dinosaur Extinction
Dr. Philip Claeys, a visiting professor at UBC, notes, “Ornans-class carbonaceous chondrites are distinctly different from conventional meteors found in museum collections.”
“Carbon monoxide chondrites contain significantly lower amounts of volatile elements like carbon, zinc, water, and especially sulfur compared to any other meteorite types known on Earth. While this does not alter the existing extinction theory, it decreases the likelihood that sulfur from the impactor was the key factor. Instead, the vast microscopic debris ejected into the atmosphere is likely the principal cause.”
This unique composition can enhance our understanding of the catastrophic impact’s aftermath. New evidence suggests that the diminished sulfur content in CO chondrites implies that sulfur from the meteorite may not have been a major disaster contributor. Instead, it is hypothesized that the immense amount of microscopic debris propelled into the atmosphere played a more critical role.
Nickel Isotopes Unveil the Impactor’s Identity
Scientists from the Institute of Geophysics and the University of Paris conducted high-precision nickel isotope measurements on samples collected over various years. These samples were obtained from thin clay layers deposited worldwide after the impact.
“This research is challenging,” Dr. Claeys remarked, a professor at the Free University of Bruxelles currently visiting UBC’s Pacific Center for Isotope Geochemistry in Earth, Ocean, and Atmospheric Sciences. “The entire meteorite was vaporized during the impact, meaning only a minuscule portion is preserved in the planet’s KT clay layer.”
Identifying the precise object that hit Earth is difficult, as the clay layer worldwide contains merely traces of the original impactor. Nevertheless, nickel isotope signatures enabled researchers to narrow it down to a rare variety of carbonaceous meteorite.
Origin of the Meteorite That annihilated the Dinosaurs
The precise origin of the meteorite remains uncertain. It may have originated from distant regions of the outer solar system, filled with rocky debris, or from the outer sections of the asteroid belt near Jupiter.
Carbonaceous chondrites constitute only about 5% of meteorites collected on Earth. Among these, CO chondrites, also termed ornaceous carbonaceous chondrites, represent a small subset. They are thought to be among the most primitive and least altered materials remaining from the solar system’s formation.
“The fact that such a rare and distant object struck Earth underscores just how unfortunate the dinosaurs were,” Dr. Claeys emphasized.
Impact Effects of Chicxulub
The Cretaceous-Paleogene impactor was estimated to be between 10 to 15 kilometers in diameter and about 6 miles wide. It collided with Earth at speeds of approximately 64,000 km/h, forming the immense Chicxulub crater.
The impact site is now buried beneath the ground in Mexico’s Yucatán Peninsula.
Source: www.sciencedaily.com