Fragments of an asteroid that killed dinosaurs can be found in the fossil site

GREENBELT, Md. – Pristine fragments of the impactor that killed the dinosaurs have been discovered, said scientists studying a site in North Dakota that is a time capsule of that calamitous day 66 million years ago.

Scientists estimate that the object that collided with the Yucatan Peninsula in what is now Mexico was about six miles wide, but the identification of the object 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 pile of rubble of rocks and dust joined by gravity?

“If you’re able to really identify it and we’re on the road to it, you can say,‘ Amazing, we know what it was, ’” said Robert DePalma, the paleontologist leading the site excavation. , said Wednesday during a talk at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

A video of the talk and a subsequent discussion between Mr. DePalma and leading NASA scientists will be published online in a week or two, a Goddard spokesman said. Many of the same findings will be discussed in “Dinosaurs: The Final Day”, a BBC documentary narrated by David Attenborough, which will be broadcast in Britain in April. In the United States, the PBS program “Nova” will broadcast a version of the documentary next month.

When the object hit the Earth, cutting a crater about 100 miles wide and nearly 20 miles deep, the molten rock splashed into the air and cooled into glass spheres, one of several business cards of meteor impacts. In the 2019 document, Mr. DePalma and his colleagues described how the spheres that rained from the sky clogged the gills of shovels and sturgeons, drowning them.

In general, the outside of the impact spheres has been mineralogically transformed for millions of years of chemical reactions with water. But in Tanis, some of them landed in tree resin, which provided an amber protective enclosure, keeping them almost as pure as the day they were 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 inside the glass.

“All those dirty little nuggets in there,” Mr. DePalma, a graduate student at the University of Manchester in England and an adjunct professor at Florida Atlantic University. “Every point you take out of this beautiful clear glass is a piece of rubble.”

Finding spheres with carcass, he said, was the equivalent of sending someone in time to the day of the impact, “collecting a sample, bottling it and keeping it for scientists right now.”

Most pieces of rock contain high levels of strontium and calcium, which were part of the limestone crust where the meteor struck.

But the composition of the fragments within two of the spherules was “very different,” Mr. DePalma.

“They weren’t as rich in calcium and strontium as we would have expected,” he said.

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

“Seeing a piece of the culprit is just a goosebumps experience,” 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 had found a fragment of the meteor in a perforated core sample in Hawaii, more than 5,000 miles from Chicxulub. Dr. Kyte said the ten-inch-diameter fragment came from the impact, but other scientists were skeptical that any piece of the meteorite could have survived.

“It’s actually in line with what Frank Kyte told us years ago,” Mr. DePalma.

In an email, Dr. Kyte said it was impossible to assess the claim without looking at the data. “Personally, I hope that if there is meteoric material in this ejecta it would be extremely rare and unlikely to be found in the large volumes of other ejecta from this site,” he said. “But maybe they were lucky.”

Mr. DePalma said there also appears to be some bubbles inside some of the spherules. Because the spheres do not appear to be broken, they may have contained chunks of air from 66 million years ago.

Jim Garvin, NASA’s chief scientist Goddard, said it would be fascinating to compare the fragments of Tanis with samples collected by NASA’s OSIRIS-REX mission, a spacecraft currently heading 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 50-year-old missions, could also be used in Tanis material. “They would work perfectly,” Dr. Garvin said.

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

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

“This is like a dinosaur CSI,” Mr. DePalma. “Now, as a scientist, I won’t say, ‘Yes, 100 percent, we have an animal that died from the impact,'” he said. “Is it compatible? Yes.”

Neil Landman, emeritus curator of the paleontology division at the American Museum of Natural History in New York, visited Tanis in 2019. captures the day of the cataclysm and its immediate consequences. “It’s the real business,” 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 as soft as modern-day geckos, and high levels of calcium in the bones and the size of the embryo’s wings support existing research that reptiles may have flown as soon as possible. they hatched.

Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland who was a consultant to 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 were victims of the impact.

“I haven’t seen any slamdunk tests yet,” he said in an email. “It’s a credible story, but it hasn’t been proven beyond a reasonable doubt in peer-reviewed literature.”

However, the pterosaur embryo is “an amazing discovery,” he said. Although he was initially skeptical, he added that after seeing photos and other information, “I was stunned. For me, this may be Tanis’ most important fossil. “

Leave a Comment

Your email address will not be published.