Asteroid that killed dinosaurs came from beyond Jupiter, new study proposes

(CN) — A new study published Thursday in the academic journal Science suggests the asteroid which killed the dinosaurs has a more distant origin than previously thought.

The research, headed by a team of scientists from across Europe, indicates the killer asteroid — scientifically named the Chicxulub Impactor — belonged to a class of space rocks known as carbonaceous chondrites. These asteroids have a relatively high concentration of carbon compounds, as their name suggests, and are thought to have formed in the early outer solar system.

Gravitational forces have pulled many carbonaceous chondrites into the asteroid belt between Mars and Jupiter in the eons since then, likely including the Chicxulub Impactor. But they remain chemically distinct from asteroids which formed closer to the sun. One telltale difference is found in isotopes of Platinum group metallic elements, particularly the metal Ruthenium.

“The Ruthenium isotope signatures of noncarbonaceous meteorites are less distinct from the Ruthenium isotope composition of Earth. By contrast, carbonaceous chondrites and carbonaceous chondrite irons are derived from carbonaceous asteroids that formed at greater heliocentric distances, beyond the orbit of Jupiter,” the study authors write. “The average Ru isotope compositions of carbonaceous chondrites and carbonaceous chondrite irons are more distinct from Earth than are [noncarbonaceous meteorites].”

Rock samples the scientists took from Denmark, Spain and Italy — dating to the dinosaurs’ global extinction event roughly 66 million years ago — all showed Ruthenium isotope signatures consistent with carbonaceous chondrites.

The results of the study also contradict earlier findings which suggested the Chicxulub Impactor may have been a comet. Rare subclasses of carbonaceous chondrites are associated with some comet material, but the researchers found distinctions between the Ruthenium isotope signatures of comet material samples and those dating to the dinosaurs’ extinction.

That extinction event marked the end of the Cretaceous Period of geologic time, and the beginning of the Paleogene Period. It wasn’t an easy transition. The asteroid, by some estimates bigger than Mt. Everest, impacted in the shallow waters of what is now the Gulf of Mexico and northwestern Yucatan Peninsula. It spread debris across the planet and sparked global wildfires, tsunamis and other cataclysms, plunging Earth into a planet-wide winter.

“It’s the dust and sulfur and soot being shot into the atmosphere that’s shutting down photosynthesis … The sun was blocked out for two to three years,” one of the study’s authors, geochemistry professor Steven Goderis of the Vrije Universiteit Brussel, told Courthouse News in an interview.

It took another several decades for the impact dust to fully clear, Goderis added, during which the Earth ricocheted from sun-blocked winter conditions to a global greenhouse as the airborne particulates trapped heat in.

“It’s this rapid change that no animal can adapt to,” he said.

More than 60% of life on Earth died out in the extinction, including most animals larger than 25 kilograms, or 55 pounds. The subclass of dinosaurs we now call birds survived, but the emptying of so many other ecological niches allowed mammals to become the planet’s dominant class of vertebrates.

Scientists studying the Cretaceous-Paleogene boundary have at times attributed this mass die-off not just to an asteroid impact but to a large volcanically-formed region in western India called the Deccan Traps.

Eruptions in the area were common during the late Cretaceous Period, leading scientists to hypothesize that the global spread of ashfall and volcanic gas contributed to the dinosaurs’ extinction. There is precedent for volcanic extinction in the fossil record.

250 million years ago, before the dinosaurs even emerged, mass volcanism in the Siberian Traps region of what is now northern Russia likely caused the most severe extinction event life on Earth has ever suffered.

However, the authors of Thursday’s paper cast doubt on the idea that the Deccan Traps meaningfully contributed to the dinosaurs’ demise, once again citing analysis of Ruthenium and other Platinum group elements.

“The abundance ratios of Platinum group elements in the Cretaceous-Paleogene boundary differ from those in the Deccan Trap volcanic basalts; the Cretaceous-Paleogene Platinum group element relative abundances are more consistent with those of chondritic meteorites, not with Deccan basalts,” the authors say.

“The relative role of the Deccan Traps in the kill mechanism has been reduced,” Goderis confirmed to Courthouse News. “This is pure meteoric material. There is no volcanic material.”

Goderis nevertheless emphasized that more research is still needed to pin down the exact relationship between the Deccan Traps, the Chicxulub Impactor and the dinosaurs’ extinction. He added that with more study, scientists will also be able to more accurately determine the chain of events that led to the asteroid striking Earth in the first place.

“If we can refine what the impactor’s composition is, we can determine where in the asteroid belt it came from,” he said.

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