Fragment of the asteroid that killed off the dinosaurs may have been found
A tiny fragment of the asteroid that hit Earth 66 million years ago may have been found encased in amber — a discovery NASA has described as “mind-blowing. It’s one of several astounding finds at a unique fossil site in the Hell Creek Formation in North Dakota that has preserved remnants of the cataclysmic moment that ended the dinosaur era — a turning point in the history of the planet. The fossils unearthed there include fish that sucked in debris blasted out during the strike, a turtle impaled with a stick and a leg that might have belonged to a dinosaur that witnessed the asteroid strike. The story of the discoveries is revealed in a new documentary called “Dinosaur Apocalypse,” which features naturalist Sir David Attenborough and paleontologist Robert DePalma and airs Wednesday on the PBS show “Nova. DePalma, a postgraduate researcher at the University of Manchester in the United Kingdom and adjunct professor for the Florida Atlantic University’s geosciences department, first started working at Tanis, as the fossil site is known, in 2012. The dusty, exposed plains starkly contrast with what the site would have looked like at the end of the Cretaceous Period. Tanis is more than 2,000 miles away from the Chicxulub impact crater left by the asteroid that struck off the coast of Mexico, but initial discoveries made at the site convinced DePalma that it provides rare evidence of what led to the end of the dinosaur era. The site is home to thousands of well-preserved fish fossils that DePalma believed were buried alive by sediment displaced as a massive body of water unleashed by the asteroid strike moved up the interior seaway. He’s certain that the fish died within an hour of the asteroid strike, and not as a result of the massive wildfires or the nuclear winter that came in the days and months that followed. “One piece of evidence after another started stacking up and changing the story.
“It gives a moment by moment story of what happens right after impact and you end up getting such a rich resource for scientific investigation. Many of the latest discoveries revealed in the documentary haven’t been been published in scientific journals. Michael Benton, a professor of vertebrate paleontology at the University of Bristol, who acted as a scientific adviser on the documentary, said while it was a “matter of convention” that new scientific claims should go through peer review before being revealed on television, he and many other paleontologists accepted that the fossil site really does represent the dinosaurs’ “last day. “Some experts have said ‘well, it might be the day after or a month before … but I prefer the simplest explanation, which is that it really does document the day the asteroid hit in Mexico,” he said via email. Most of the glassy impact spherules that first revealed the fingerprints of the asteroid impact to DePalma are preserved as clay as a result of geological processes over millions of years. “In that amber we’ve located a number of spherules that were basically frozen in time, because, just like an insect in amber which is perfectly preserved, when these spherules entered the amber, water couldn’t get to them. It’s “like getting a sample vial, running back in time and getting a sample from the impact site and then saving it for science,” DePalma said. They were able to locate a number of little unmelted fragments of rock inside the glass spherules. DePalma said they hope to be able to confirm what the asteroid was made from and where it might be from — efforts that have caught the attention of NASA; DePalma presented his findings last month at the agency’s Goddard Space Flight Center in Greenbelt, Maryland. “This example of what might be a little tiny fragment, maybe micrograms, of the colliding asteroid — the fact that a record of that is preserved, would be mind-blowing,” said Goddard Chief Scientist Jim Garvin, who has studied impact cratering on Earth and Mars.
Research on the amber-entombed spherules hasn’t been published in a peer-reviewed journal. An exceptionally preserved dinosaur leg with skin in tact is another discovery from the Tanis site that features in the documentary, which first aired in the UK in April, and has turned heads in the paleontological world. Very few fossils from the Cretaceous Period have been found in the uppermost rocks of the geological record, and it’s possible the limb — which belongs to a Thescelosaurus, a small plant-eating dinosaur DePalma and his colleagues discovered — could have died on the very day the asteroid hit. “The only two supported scenarios here are that it died in the surge or that it died immediately before (the asteroid strike) but so close in time that it really did not have time to decay. Detailed analysis of the dinosaur’s leg bones could shed light on what conditions were like in the lead-up to the impact. Other cool finds from the site include a fossilized pterosaur egg, the first found in North America. The work being done at Tanis not only nails down in jaw-dropping detail what happened the day the asteroid struck, it also provides insight into an event that caused a mass extinction and how that extinction subsequently unfolded. “The fossil record gives us a window into the details of a global-scale hazard and the reaction of Earth’s biota to that hazard,” DePalma said.
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