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(CNN) –– Dinosaurs could have been extinguished by a comet instead of an asteroid, according to a new study.
Harvard researchers theorized that a piece of comet smashed into Earth more than 66 million years ago and created the Chicxulub crater. This is pointed out by the study published this Monday in the journal Scientific Reports.
The Chicxulub crater is located on the Yucatán Peninsula, in what is now Mexico, and stretches for about 177 kilometers. The impact that created the crater is related to the Cretaceous-Paleogene extinction event, which wiped out dinosaurs and many other species, according to the study.
It must have been a beautiful sight. But the fun ended when the rock hit the ground, “said study co-author Abraham Loeb, a science professor at Harvard University.
Loeb’s theory is that a piece of comet was responsible for the mass extinction event, and not an asteroid as is the hypothesis of many scientists. The comet originated in the Oort Cloud, a group of icy objects located at the edge of the solar system, he noted.
A comet is a piece of space debris made up mostly of frozen gas. Meanwhile, the asteroid is a piece of rock most commonly found in the Asteroid Belt, a collection of asteroids between Mars and Jupiter, according to CNN weather correspondent Chad Myers.
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The odds that an asteroid with a diameter of at least 9.9 kilometers will cause an impact event at Chicxulub is one in every 350 million years, according to the study. Long-period comets – whose orbit is more than 200 years – that are capable of generating an event at Chicxulub are significantly more unusual. Only one occurs from 3.8 to 11 billion years, the study found.
The possible path of the comet
The researchers present a theory of how the comet could have overcome those remote probabilities.
As the comet traveled to the center of the solar system from the Oort cloud, Jupiter’s gravitational force could have given it a boost so that it was fast enough to reach the Sun, according to Loeb.
“Jupiter acts like a pinball machine,” Loeb noted. “When something comes close to you, you can kick it.”
Upon reaching the Sun, the gravitational force of our star could have broken the comet into multiple pieces, according to the researcher. By having more comet pieces, the comet is 10 times more likely to hit Earth when the pieces move away from the Sun, according to Loeb.
Other researchers question the new theory
Other researchers disagreed with the new study’s findings. In that sense, they point out that several clues suggest that an asteroid created the Chicxulub crater and wiped out the dinosaurs.
For one thing, iridium – along with a handful of other chemical elements – was found scattered around the world after the impact, said David Kring, senior scientist at the Lunar and Planetary Institute in Houston who was not involved in the study of the Kite.
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Kring noted that the proportions of those elements are the same proportions seen in asteroid meteorite samples.
The comet piece would also have been too small to form a crater of that size, said Natalia Artemieva, who was also not involved in the study. Artemieva is a senior scientist at the Institute for Planetary Sciences.
The study estimated the size of the comet piece to be about 6.4 kilometers across. But, Artemieva argued that the comet would need to be at least 12 kilometers wide to make a crater the magnitude of Chicxulub. In that sense, he explained that with the small piece of comet that “is absolutely impossible.” He also indicated that the size of the impact crater would be at least half.
On the other hand, Kring noted that the frequency with which an asteroid or comet hits Earth to create such an impact is statistically insignificant.
It doesn’t matter if it’s roughly “once every 350 million years and we had an event 66 million years ago.” Because statistically, that would be the only occurrence in 350 million years, he said.
The researchers also have a large number of asteroid samples to study in comparison to comets, Kring said.
“There is absolutely no evidence to show that your model is wrong. But on the other hand, there is a lot of evidence that still points to an asteroid being the most likely element to hit, “said Kring.
Loeb noted that he is interested in searching for remaining comet pieces from the rupture to verify his theory.
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