Splinters from an asteroid that killed the dinosaurs may have been found at a fossil site

Robert DePalma, a paleontologist, gives a presentation on his finds of fossil remains Wednesday, April 6, 2022 at the Goddard Space Flight Center in Greenbelt, Maryland. (Taylor Mickal/NASA via The New York Times)

GREENBELT, Md. — Pristine fragments of the impactor that killed the dinosaurs have been discovered, scientists studying a North Dakota site that’s a time capsule of that cataclysmic day 66 million years ago have been discovered.

The object, which impacted off the Yucatán Peninsula in modern-day Mexico, was about 6 miles across, scientists estimate, but the object’s identification has remained a subject of debate. Was it an asteroid or a comet? If it was an asteroid, what kind was it—a solid metallic one, or a rubble of rock and dust held together by gravity?

“If you can actually identify it, and we’re getting there, then you can actually say, ‘Amazing, we know what it was,'” Robert DePalma, a paleontologist leading the excavation of the site, said Wednesday during a lecture at NASA Goddard Space Flight Center in Greenbelt.

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A video of the lecture and a subsequent discussion between DePalma and prominent NASA scientists will be posted online in a week or two, a spokesman for Goddard said. Many of the same discoveries are discussed in Dinosaurs: The Final Day, a BBC documentary starring David Attenborough, which will air in the UK this month. In the United States, the PBS program Nova will air a version of the documentary next month.

A 2019 New Yorker article described the site in southwest North Dakota, named Tanis, as a wonderland of fossils buried about 2,000 miles away after the impact. Many paleontologists were intrigued but unsure of the scope of DePalma’s claims; A research paper published earlier this year by DePalma and his collaborators primarily described the geological setting of the site, which was once on the banks of a river.

As the object struck Earth, leaving a crater about 100 miles wide and nearly 20 miles deep, molten rock spattered into the air and cooled into glass globules, one of the distinctive calling cards of meteorite impacts. In the 2019 publication, DePalma and his colleagues described how globules raining down from the sky clog the gills of paddlefish and sturgeon, causing them to suffocate.

Normally, the outsides of impact spherules have been mineralogically transformed through millions of years of chemical reactions with water. But with Tanis, some of them ended up in tree sap, which formed a protective shell of amber, leaving them almost as pristine as the day they were created.

In the latest findings, which have yet to be published in a peer-reviewed scientific journal, DePalma and his research colleagues focused on unmelted rock chunks in the jar.

“All those little dirty nuggets in there, every single speck that goes off that nice clear glass, is a piece of debris,” said DePalma, a doctoral student at the University of Manchester in England and an associate professor at Florida Atlantic University.

Finding amber-encased globules, he said, is the equivalent of sending someone back in time to the day of impact, “collect a sample, bottle it, and keep it for scientists to use immediately.”

Most of the rocks are high in strontium and calcium — an indication they were part of the limestone crust where the meteor struck.

But the composition of the fragments in two of the beads was “quite different,” DePalma said.

“They weren’t fortified with calcium and strontium as expected,” he said.

Instead, they contained higher levels of elements such as iron, chromium, and nickel. This mineralogy indicates the presence of an asteroid, specifically a type known as carbonaceous chondrites.

“Seeing a piece of the perpetrator is just a chilling experience,” DePalma said.

The find supports a discovery reported in 1998 by Frank Kyte, a geochemist at UCLA. Kyte said he found a fragment of the meteor in a core sample drilled off Hawaii, more than 5,000 miles from Chicxulub Crater. Kyte said the fragment, about a tenth of an inch in diameter, came from the impact event, but other scientists were skeptical that any pieces of the meteor could have survived.

“It actually aligns with what Frank Kyte told us years ago,” DePalma said.

In an email, Kyte said it was impossible to evaluate the claim without looking at the data. “Personally, my assumption is that if there is meteoritic material in this ejecta, it is extremely rare and unlikely to be found in the vast amounts of other ejecta at this site,” he said. “But maybe they were lucky.”

DePalma said there also appears to be some bubbles in some of the beads. Because the beads don’t appear to have cracked, it’s possible they contain shreds of air from 66 million years ago.

Jim Garvin, chief scientist at NASA Goddard, said it would be fascinating to compare the Tanis fragments to samples collected by NASA’s Osiris-Rex mission, a spacecraft en route to Earth after visiting Bennu, a similar but smaller asteroids.

Cutting-edge techniques used to study space rocks, such as the recently opened samples from the Apollo missions 50 years ago, could also be applied to the Tanis material. “They would work perfectly,” Garvin said.

In the talk, DePalma also showed other fossil finds, including a well-preserved leg from a dinosaur identified as a herbivorous Thescelosaurus. “This animal was preserved in such a way that you had these three-dimensional skin casts,” he said.

There is no evidence that the dinosaur was killed by predator or disease. This suggests that the dinosaur may have died on the day of the meteorite impact, perhaps by drowning in the tides that inundated Tanis.

“It’s like dinosaur CSI,” DePalma said. “Well, as a scientist, I’m not going to say, ‘Yes, 100%, we have an animal that died in the impact wave,'” he said. “Is it compatible? Yes.”

Neil Landman, curator emeritus in the Department of Paleontology at the American Museum of Natural History in New York, visited Tanis in 2019. He saw one of the paddlefish fossils with globules in their gills and believes the site does indeed capture the day of The catastrophe and its immediate consequences. “It’s the real deal,” he said.

DePalma also shared images of an embryo of a pterodactyl, a flying reptile that lived at the time of the dinosaurs. Studies show that the egg was soft like that of modern-day geckos, and the high calcium content in the embryo’s bones and wing dimensions support existing research that the reptiles may have been able to fly once hatched.

Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland who was an adviser on the BBC documentary, is also convinced the fish died that day, but he’s not yet sure if the dinosaur and pterodactyl egg did too were victims of the impact.

“I haven’t seen any slam dunk evidence yet,” he said in an email. “It’s a credible story, but one that hasn’t been proven beyond a reasonable doubt in the peer-reviewed literature.”

But the pterosaur embryo is still “an amazing discovery,” he said. Although he was initially skeptical, after seeing photos and other information, he added: “I was blown away. To me, this is perhaps the most important fossil from Tanis.”

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