GREENBELT, Md. Pristine splinters from the impactor that killed the dinosaurs have been discovered, say scientists studying a site in North Dakota that is a time capsule from that disastrous day 66 million years ago.
The object that slammed off the Yucatán Peninsula of present-day Mexico was about six miles across, scientists estimate, but the object’s identification has remained a matter of debate. Was it an asteroid or a comet? If it was an asteroid, what kind was it — a solid metal or a mess of rocks and dust held together by gravity?
“If you can really identify it, and we’re on track to do that, then you can really say, ‘Great, we know what it was,'” Robert DePalma, the paleontologist who led the excavation of the site, said Wednesday during a lecture at the NASA Goddard Space Flight Center in Greenbelt, Maryland.
A video of the conversation and subsequent discussion between Mr. DePalma and prominent NASA scientists will be released online in a week or two, a Goddard spokesperson said. Many of the same discoveries will be discussed in “Dinosaurs: The Final Day”, a BBC documentary narrated by David Attenborough, which will air in Britain in April. In the United States, the PBS program “Nova” will air a version of the documentary next month.
When the object hit Earth, carving a crater about 100 miles wide and nearly 20 miles deep, molten rock splashed into the air and cooled into spherules of glass, one of the obvious calling cards of meteor impacts. In the 2019 paper, Mr. DePalma and his colleagues described how globules raining down from the sky clogged the gills of paddlefish and sturgeon and choked them.
Usually, the exteriors of impact spheres are mineralogically transformed by millions of years of chemical reactions with water. But at Tanis, some of them ended up in tree resin, yielding a protective sheath of amber, leaving them almost as pristine as the day they formed.
In the latest findings, which have not yet been published in a peer-reviewed scientific journal, Mr. DePalma and his research colleagues focused on pieces of unmelted rock in the glass.
“All these little dirty nuggets in there,” said Mr. DePalma, a graduate student at the University of Manchester in England and an adjunct professor at Florida Atlantic University. “Every speck that takes away from this beautiful clear glass is a piece of rubble.”
Finding amber-coated spheres, he said, was the equivalent of sending someone back in time to the day of the impact, “collecting a sample, bottle it and now keep it for scientists.”
Most of the rock sections contain high levels of strontium and calcium — indications that they were part of the limestone crust where the meteor hit.
But the composition of the fragments in two of the spheres was “very different,” Mr. DePalma said.
“They were not fortified with calcium and strontium as we expected,” he said.
Instead, they contain higher levels of elements such as iron, chromium and nickel. That mineralogy points to the presence of an asteroid, and in particular a type known as carbonaceous chondrites.
“To see part of the culprit is just a goosebumps experience,” said Mr. DePalma.
The finding supports a discovery reported in 1998 by Frank Kyte, a geochemist at the University of California, Los Angeles. dr. Kyte said he found a fragment of the meteor in a core sample drilled off the coast of Hawaii, more than 5,000 miles from Chicxulub. dr. Kyte said that fragment, about a tenth of an inch across, came from the impact, but other scientists were skeptical that any bits of the meteor would have survived.
“It actually matches what Frank Kyte told us years ago,” said Mr. DePalma.
In an email, Dr. Kyte said it was impossible to evaluate the claim without looking at the data. “Personally, I expect that if there is any meteorite material in this ejecta, it would be extremely rare and unlikely to be found in the vast amounts of other ejecta at this site,” he said. “But maybe they got lucky.”
Mr. DePalma said there also seem to be some bubbles in some of the globules. Because the spheres don’t appear to be cracked, it’s possible they could have contained bits of air from 66 million years ago.
Jim Garvin, the chief scientist at NASA Goddard, said it would be fascinating to compare the Tanis fragments with samples collected by NASA’s OSIRIS-REX mission, a spacecraft currently en route to Earth after visiting Bennu. , a similar but smaller asteroid.
State-of-the-art techniques used to study space rocks, such as the recently opened samples from the Apollo missions from 50 years ago, can also be used on the Tanis material. “They would work perfectly,” said Dr. Garvin.
In the talk, Mr. DePalma also showed other fossil finds, including a well-preserved dinosaur leg identified as a herbivorous Thescelosaurus. “This animal is so conserved that you got these three-dimensional skin impressions,” he said.
There are no signs that the dinosaur was killed by a predator or disease. That suggests the dinosaur may have died on the day of the meteor impact, perhaps drowning in the floodwaters that engulfed Tanis.
“This is like a dinosaur CSI,” said Mr. depalma. “Now, as a scientist, I’m not going to say, ‘Yeah, 100 percent, we have an animal that died during the impact wave,'” he said. “Is it compatible? Yes.”
Neil Landman, curator emeritus in the paleontology department at the American Museum of Natural History in New York, visited Tanis in 2019. He saw one of the fossils of paddlefish with bubbles in its gills and is convinced that the site was indeed the day of the disaster and its immediate aftermath. “It’s the real deal,” he said in a telephone interview.
Mr. DePalma also showed images of an embryo of a pterosaur, a flying reptile that lived during 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 bones and the size of the embryo’s wing support existing research that the reptiles would have been able to fly once they hatched.
Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland and advisor to the BBC documentary, is also convinced that the fish died that day, but he’s not sure yet that the dinosaur and pterosaur egg also suffered. were the consequence.
“I haven’t seen any slam-dunk evidence yet,” he said in an email. “It’s a credible story, but it hasn’t been proven beyond a reasonable doubt in the peer-reviewed literature.”
But the pterosaur embryo is nonetheless “an astonishing discovery,” he said. Though initially skeptical, he added that after seeing photos and other information, “I was blown away. To me, this is arguably Tanis’s most important fossil.”