Greenbelt, Md. — Primitive fragments of the probe that killed the dinosaurs have been discovered, say scientists studying a site in North Dakota that is a time capsule of that catastrophic day 66 million years ago.
Scientists estimate that the object that struck the Yucatan Peninsula of what is today Mexico was about six miles wide, but the exact identification of the object has remained a topic of debate. Was it an asteroid or a comet? If it’s an asteroid, what type is it – solid metal or a pile of rocks and dust held together by gravity?
“If you’re actually able to identify it, and we’re going to do that, you can actually say, ‘Wonderful, we know what it was,'” Robert De Palma, the paleontologist who led the excavations at the site, said Wednesday during a talk at the Goddard Center. NASA Space Flight Center in Greenbelt, Maryland.
A Goddard spokesperson said that a video of the conversation and subsequent discussion between Mr. de Palma and prominent NASA scientists will be posted online within a week or two. Many of the same discoveries will be discussed in Dinosaurs: The Last Day, a BBC documentary narrated by David Attenborough, which will be broadcast in Britain in April. In the US, PBS Nova will air a version of the documentary next month.
When the body hit the ground, carving a crater about 100 miles wide and nearly 20 miles deep, molten rock scattered into the air and cooled into balls of glass, one of the hallmark calling cards of meteorite impacts. In a 2019 paper, Mr. de Palma and colleagues describe how pellets raining from the sky clog the gills of sturgeon, suffocating them.
The outer sides of the shock pellets have usually been mineralized by millions of years of chemical reactions with water. But at Tanis, some fell into the tree’s resin, which provided a protective covering of amber, making it as pure as the day it formed.
In the latest findings, which have not yet been published in a peer-reviewed scientific journal, Mr. de Palma and his research colleagues focused on fragments of unmolten rock within the glass.
“All these dirty little bits are there,” said Mr. De Palma, a graduate student at the University of Manchester in England and an assistant professor at Florida Atlantic University. “Every single spot emerging from this beautiful clear glass is a piece of debris.”
Finding the amber-covered balls, he said, is the equivalent of sending someone back in time to the day of the impact, “collecting a sample, packing it up and saving it for scientists for the time being.”
Most of the rock pieces contain high levels of strontium and calcium – indicating that they were part of the limestone crust where the meteorite struck.
Mr. de Palma said the composition of the parts inside two of the balls was “completely different”.
“They were not enriched with calcium and strontium as we would expect,” he said.
Instead, they contained higher levels of elements such as iron, chromium, and nickel. This mineralogy indicates the presence of an asteroid, in particular a type known as carbonaceous chondrite.
“Seeing part of the offender is just an experience full of bumps,” Mr. de Palma said.
This finding supports a finding reported in 1998 by Frank Kite, a geochemist at the University of California, Los Angeles. Dr. Kite said he found a fragment of the meteorite in a core sample drilled off Hawaii, more than 5,000 miles from Chicxulub. Dr. Kite said the fragment, which is about a tenth of an inch in diameter, came from the impact event, but other scientists were skeptical that any bits of the meteorite might have survived.
“It’s actually in line with what Frank Kate told us years ago,” Mr. De Palma said.
In an email, Dr. Kyte said it was impossible to assess the claim without looking at the data. “Personally, I would expect that if there was any meteorite material in this projectile, it would be extremely rare and unlikely to be found in the colossal volumes of other projectiles at this location,” he said. “But maybe they got lucky.”
It also looks like there are some bubbles inside some of the balls, Mr. de Palma said. Since the pellets do not appear to be cracked, it is possible that they held chunks of air from 66 million years ago.
It would be fascinating to compare the Tanis fragments with samples collected by NASA’s OSIRIS-REx mission, a spacecraft currently on its way to Earth after visiting Bennu, a similar but smaller asteroid, Jim Garvin, NASA’s chief scientist at Goddard said.
The latest technology used to study space rocks, such as the recently opened samples from the Apollo missions 50 years ago, can also be used in Tanis material. “They will work perfectly,” Dr. Garvin said.
In the talk, Mr. de Palma also showed off other fossil finds including a well-preserved leg of a dinosaur, identified as a plant-eating Thesylosaurus. “This animal has been preserved in such a way that you have these 3D skin impressions,” he said.
There is no evidence that the dinosaur was killed by a predator or disease. This suggests that the tyrannosaurus may have died on the day of the meteor impact, possibly due to drowning in the floodwaters that submerged Tanis.
“This looks like a CSI dinosaur,” Mr. de Palma said. He said, “Now, as a scientist, I wouldn’t say, ‘Yes, 100 percent, we have an animal that died in the collision crash.'” Is it compatible? yes.”
Neil Landmann, curator emeritus in the Department of Paleontology at the American Museum of Natural History in New York, visited Tanis in 2019. He saw one of the fossils of paddle fish with globular balls in its gills and is convinced the site is indeed capturing the day of the disaster and its first-hand consequences. “It’s the real deal,” he said in a phone interview.
Mr. de Palma also showed pictures of the embryo of a flying reptile that lived in the time of the dinosaurs. Studies show that the egg was as tender as that found in modern-day geckos, and that the high levels of calcium in the bones and the dimensions of the fetus’s wing supports current research that reptiles may have been able to fly once they hatched.
Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland who served as a consultant on a BBC documentary, is also convinced that the fish died that day, but he has yet to confirm that the dinosaurs and the pterosaur egg were also the victims of an impact.
“I have not yet seen evidence of a slam dunk,” he said in an email. “It is a credible story but one that has not yet been proven beyond reasonable doubt in the peer-reviewed literature.”
But he said the pterosaur embryo was nonetheless an “amazing discovery”. Although skeptical at first, he added that after seeing the photos and other information, “I was dumbfounded. To me, this might be the most important fossil from Tanis.”