Shards of Asteroid That Killed the Dinosaurs May Have Been Found in Fossil Site

GREENBELT, Md. — Pristine shards 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 calamitous day 66 million years ago.

The object that crashed off the Yucatán Peninsula of what is now Mexico was about six miles wide, scientists estimate, but identifying the object has remained a matter of debate. Was it an asteroid or a comet? If it was an asteroid, what type was it? A metallic solid or a pile of rubble of rocks and dust held together by gravity?

“If you’re able to identify it, and we’re on track to do it, then you can actually say, ‘Amazing, we know what that was,'” Robert DePalma, the head paleontologist excavations of the site. , said Wednesday during a conference at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

A video of the conference and a subsequent discussion between DePalma and leading NASA scientists will be posted online in a week or two, a Goddard spokesperson said. Many of the same findings 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 show “Nova” will air a version of the documentary next month.

When the object struck Earth, carving a crater about 100 miles wide and nearly 20 miles deep, molten rock splashed through the air and cooled into glass spherules, the one of the distinct calling cards of meteor impacts. In the 2019 paper, DePalma and his colleagues described how spherules falling from the sky clogged the gills of paddlefish and sturgeon, choking them.

Usually, the exterior of impact spherules has been mineralogically transformed by millions of years of chemical reactions with water. But in Tanis, some of them landed in tree resin, which provided a protective enclosure of amber, keeping them nearly as pristine as the day they formed.

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

“All these dirty little nuggets in there,” said DePalma, a graduate student at the University of Manchester in England and an adjunct professor at Florida Atlantic University. “Every grain that removes this beautiful transparent glass is a piece of debris.”

Finding spherules in amber, he said, was like sending someone back in time to the day of impact, “taking a sample, bottling it, and storing it for scientists in this moment”.

Most of the rock chunks contain high levels of strontium and calcium – indications that they were part of the limestone crust where the meteor struck.

But the composition of the fragments in two of the spherules was “very different”, DePalma said.

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

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

“Seeing a piece of the culprit is just an overwhelming experience,” Mr. DePalma said.

The discovery corroborates a finding 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 Hawaii, more than 8,000 kilometers from Chicxulub. Dr Kyte said this fragment, about a tenth of an inch in diameter, was from the impact event, but other scientists were skeptical whether pieces of the meteor survived.

“It actually lines up with what Frank Kyte was telling us years ago,” Mr. DePalma said.

In an email, Dr Kyte said it was impossible to assess the claim without reviewing the data. “I personally expect that if any meteorite material is found in this ejecta, it would be extremely rare and unlikely to be found in the vast volumes of other ejecta at this site,” he said. . “But maybe they were lucky.”

Mr DePalma said there also appear to be bubbles in some of the spherules. Because the spherules do not appear to be cracked, it is possible that they may contain pieces of air from 66 million years ago.

NASA Goddard chief scientist Jim Garvin 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 a visit to 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 50 years ago, could also be used on the Tanis material. “They would work perfectly,” Dr. Garvin said.

During the lecture, DePalma also showed other fossil finds, including a well-preserved dinosaur leg identified as a plant-eating Thescelosaurus. “This animal was preserved in such a way that you had these three-dimensional skin impressions,” he said.

There are no signs that the dinosaur was killed by a predator or by disease. This suggests that the dinosaur may have died on the day of the meteor impact, possibly by drowning in the floodwaters that submerged Tanis.

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

Neil Landman, curator emeritus of the American Museum of Natural History’s division of paleontology in New York, visited Tanis in 2019. He saw one of the paddlefish fossils with spherules in its gills and is convinced that the site captures well the day of the cataclysm and its immediate aftermath. “This is the real deal,” he said in a phone interview.

Mr. DePalma also showed images of a pterosaur embryo, a flying reptile that lived during the age of the dinosaurs. Studies indicate that the egg was soft like those of modern geckos, and the high levels of calcium in the bones and the dimensions of the embryo’s wings support existing research that the reptiles could have flew as soon as they hatched.

Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland who served as a consultant for the BBC documentary, is also convinced that the fish died that day, but it is not yet certain that the dinosaur and the pterosaur egg also fell victim to the impact.

“I haven’t seen any hard evidence yet,” he said in an email. “It’s a believable story but one that has yet to be proven beyond reasonable doubt in the peer-reviewed literature.”

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