Did a comet fragment kill the dinosaurs? It is unlikely, say researchers

The global extinction event that involved curtains for dinosaurs apparently was not triggered by a comet chip that hit Earth, several planetary scientists now argue.

This latest theory has been challenged to explain how a comet (or fragments) could enter the Gulf of Mexico near Chicxulub. The recent appendix in the magazine Natural Science Reports posters that a fragment (or fragments) from a large, long comet have been pushed into Jupiter’s solar grazing orbits. As a result, they write to the effect that led to the extinction of both dinosaurs and three-quarters of all living species on Earth.

In their paper, Harvard University astronauts Amir Siraj and Avi Loeb argue that, as they approach the Sun, such large comets are severely disrupted, concluding. areas of monetary shrapnel, a portion of which appears to have entered the gulf about 66 billion years ago.

But there are still doubts that David Kring, Chief Scientist at the USRA Lunar and Planetary Institute (LPI) in Houston.

“A surviving fragment of the Chicxulub effector resembles meteoritic particles of asteroids and does not resemble the only sample we have from a comet,” Kring told me. Furthermore, Kring says that chemical traces of the impact device in debris extracted from the Chicxulub fracture are similar to the chemical composition of known meteoritic particles of asteroids.

There is also the iridium abundance problem.

Most of the Earth’s Iridium is trapped in the heart and fabric of our planet, Kring writes in an article. Thus, any large irregular size found in the Earth’s crust would mean that a new supply was brought to the surface through a kind of condenser, Kring notes.

Now colloquially known among researchers as the K-Pg Frontier, to mark the event of a major Cretaceous-Paleogene (K-Pg) edema, it is now widely accepted that the boundary marked by global density of iridium, new paper authors. appearing in the magazine Scientific advances, note last week. This iridium anomaly “thus reflects the global distribution of meteoritic matter after the effects of asteroid hypervelocity about 12-km in diameter,” the authors wrote.

“The K-Pg meteorite fragment I found was dense and resembling carbonaceous chondrites that are certainly of asteroidal origin; there is no reason to believe that comets are equivalent to this, ”Frank Kyte, geophysicist at the University of California, Los Angeles (UCLA) told me. If anything, Kyte says comets have a lot of volatile ice creams, so they may have a lot less iridium than meteorites.

In fact, the comet ‘s story contradicts iridium values ​​found at more than 100 K – Pg border sites around the world, said Philippe Claeys, a geologist at the Free University of Brussels ( VUB) in Belgium.

But Siraj, an undergraduate from Harvard University who studied astronomy at the Harvard & Smithsonian Center for Astrophysics, and lead author of the paper, said there is no conflict with their model and the iridium density at the K Borders -Pg. In fact, a detailed and updated analysis of iridium data favors the effector mass used in our model, he told me.

Nevertheless, “Siraj and Loeb’s paper does not mention iridium,” Stephen Kane, a planetary scientist at the University of California, Riverside, told me.

But Siraj says their model is not well-tuned, but is capable of influencing a wide range of sizes within orders of magnitude.

If that is true, Kane reckons, the projected size parameters of these objects become so large that they no longer provide meaningful results.

Why not asteroids?

Siraj and Loeb ‘s proven asteroids that make Chicxulub – sized events occur more frequently than once every 750 million years or so, Kring notes. “Chicxulub-sized events from a number of objects close to Earth are estimated to occur on average once every 100 million years,” he writes.

But Siraj and Loeb’s model begins with a time-comet about 60-km in diameter which, once broken, yields a comet fragment with a diameter of some of 7-km, which they propose to be the Chicxulub influencer, Kring notes. The paper does not show how a comet can produce around 7-km Chicxulub, when computer simulations published by other researchers show that something much bigger is needed, Kring writing.

“[Thus], the diameter of the modified comet is far too small to produce the Chicxulub impact pit, ”Kring told me.

Siraj and Loeb note that finer particles less than 7-km will also hit the Earth. The authors noted in their paper that one of these silver fragments may have even hit the Earth within the last million years, possibly causing a crack. Zhamanshin of 14-km diameter Kazakhstan.

If so, Kring writes in his essay, that this would have to survive money crumbs for more than 60 million years without being eradicated from the Solar System, further disrupted, and / or meeting with other organizations. This only pushes the envelope of credit further.

And why restart the Chicxulub impact wheel when asteroid influencers could operate after all?

If a piece of long-range comet hit the Earth, it would be likely to do so at speeds as high as 50 km per second compared to 20 km per second for asteroid beaters, Simone Marchi, Chief of Staff science at the Southwest Research Institute in Boulder, Colo. said, I told. So, he says, a silver crawler larger than 5-10 km combined with such a high impact speed would probably produce a much larger crater than Chicxulub.

In other words, because it affects distance, the silver effect dish may never be appropriate.

“So, it may not be necessary to start start-up money to start the K-Pg effect first,” Marchi said.

It all relaxes you to wonder if the dinosaurs themselves would have put so much thought into the cause of their own decline.

Who is right about the true origin of the Chicxulub influencer?

I think this is just a random event, that trying to introduce some sort of statistical probability proves nothing, Kyte says.

Or as Kring puts it: “While we cannot prove that the culprit was not a comet, the available data show that it was an asteroid.”