Scientists researching a North Dakota site that is a time capsule of that terrible day 66 million years ago have unearthed pristine slivers of the impactor that killed the dinosaurs.
Scientists estimate that the asteroid that slammed into the Yucatán Peninsula of what is now Mexico was around 6 miles wide, but its identity has been a point of contention. Was it a comet or an asteroid? Was it a solid metallic asteroid or a rubble pile of rocks and dust kept together by gravity if it was an asteroid?
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“If you can truly identify it, which we are on the verge of accomplishing, then you can say, ‘Amazing, we know what it was,'” says the researcher. During a discussion at the NASA Goddard Space Flight Center in Greenbelt on Wednesday, palaeontologist Robert DePalma, who is overseeing the site’s excavation, said.
According to a Goddard representative, a video of the session and a subsequent debate between DePalma and top NASA scientists will be available online in a week or two. Many of the same finds will be discussed in “Dinosaurs: The Final Day,” a BBC program narrated by David Attenborough and set to debut later this month in the United Kingdom. Next month, a version of the documentary will air on the PBS show “Nova” in the United States.
In a 2019 New Yorker story, the Tanis site in southern North Dakota was described as a “wonderland of fossils” buried in the aftermath of the 2,000-mile-away impact. Many palaeontologists were fascinated but sceptical of DePalma’s statements; a study article published that year by DePalma and his partners clarified the breadth of DePalma’s findings.
Molten rock splashed into the air and froze into spherules of glass, one of the unmistakable calling cards of meteor impacts, when the item hit Earth, cutting a crater about 100 miles wide and about 20 miles deep. DePalma and his colleagues recounted how spherules showering down from the sky clogged paddlefish and sturgeon gills, causing them to suffocate.
Millions of years of chemical interactions with water have usually mineralogically changed the outsides of impact spherules. However, some of them landed in tree resin at Tanis, providing a protective amber enclosure that kept them almost as immaculate as the day they originated.
DePalma and his colleagues concentrated on pieces of unmelted rock within the glass in their latest discoveries, which have yet to be published in a peer-reviewed scientific journal.
“All these little dirty nuggets in there, every single speck that takes away from this lovely pure glass is a piece of detritus,” said DePalma, an adjunct professor at Florida Atlantic University and a PhD student at the University of Manchester in England.DePalma
He compared finding amber-encased spherules to sending someone back in time to the day of the impact and “taking a sample, bottling it up, and preserving it for scientists right now.”
The majority of the rock fragments include significant quantities of strontium and calcium, indicating that they came from the limestone crust where the meteor landed.
The makeup of fragments within two of the spherules, on the other hand, was “wildly different,” according to DePalma.
“They weren’t as calcium and strontium-enriched as we had hoped,” he remarked.
Instead, they have larger concentrations of elements such as iron, chromium, and nickel. The presence of an asteroid, namely carbonaceous chondrites, is indicated by the mineralogy.
“Seeing a bit of the perpetrator gives me goosebumps,” DePalma said.
The discovery backs up a discovery made by UCLA geochemist Frank Kyte in 1998. A component of the meteor was discovered in a core sample drilled off the coast of Hawaii, more than 5,000 miles from the Chicxulub crater, according to Kyte. The shard, approximately a tenth of an inch across, came from the impact event, according to Kyte, but other scientists doubted that any fragments of the meteor could have survived.
DePalma remarked, “It actually comes in line with what Frank Kyte was telling us years ago.”
In an email, Kyte stated that evaluating the claim without looking at the data was impossible. “If there is any meteoritic material in this ejecta,” he continued, “I expect it to be quite rare and unlikely to be detected in the large volumes of other ejecta at this site.” “However, it’s possible they got lucky.”
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Some of the spherules also appear to have bubbles, according to DePalma. It’s possible that the spherules could hold pieces of air from 66 million years ago because they don’t appear to be fractured.
The comparison of the Tanis shards with samples gathered by NASA’s Osiris-Rex mission, a spacecraft en way to Earth following a visit to Bennu, a comparable but smaller asteroid, would be fascinating, according to Jim Garvin, NASA Goddard’s top scientist.
The Tanis material might be studied using cutting-edge procedures similar to those used to investigate space rocks, such as the recently opened samples from the Apollo missions 50 years ago. “They’d be perfect,” Garvin stated.
DePalma also displayed other fossil finds during his presentation, including a well-preserved dinosaur leg identified as a plant-eating Thescelosaurus. He explained, “This animal was kept in such a way that you got these three-dimensional skin impressions.”
There is no evidence that the dinosaur died as a result of a predator or disease. This means the dinosaur died on the day of the meteor strike, maybe drowning in the floodwaters that engulfed Tanis.
“It’s like CSI for dinosaurs,” DePalma added. “As a scientist, I’m not going to claim, ‘Yes, 100%, we do have an animal that died in the impact surge,'” he explained. “Is it compatible?” says the narrator. Yes.”
In 2019, Neil Landman, emeritus curator of palaeontology at the American Museum of Natural History in New York, paid a visit to Tanis. He noticed spherules in the gills of one of the paddlefish fossils and is confident that the location accurately depicts the day of the cataclysm and its immediate aftermath. He stated, “It’s the real deal.”
DePalma also displayed photographs of a pterosaur embryo, a flying reptile that lived during the dinosaur era. The egg was soft, similar to that of modern-day geckos, and the high levels of calcium in the bones and the embryo’s wing size back up previous evidence suggesting the reptiles could have flown as soon as they hatched.
Steve Brusatte, a palaeontologist at the University of Edinburgh in Scotland who served as a consultant for the BBC documentary, is similarly persuaded that the fish perished on that fateful day, but he isn’t sure if the dinosaur and pterosaur egg were also killed.
In an email, he wrote, “I haven’t yet seen slam-dunk evidence.” “It’s a credible story, but it hasn’t yet been verified in peer-reviewed literature beyond a reasonable doubt.”
Nonetheless, the pterosaur embryo is “an extraordinary discovery,” he said. “I was blown away,” he said after seeing images and other material, despite his initial scepticism. This is, in my opinion, Tanis’ most important fossil.”