About 66 million years ago, a space rock more than 6 miles wide collided with Earth and hit land that is now part of Mexico.
The impact resulted in wildfires that stretched for hundreds of kilometers, causing a kilometer high tsunami and releasing billions of tons of sulfur into the atmosphere. That gaseous haze blocked the sun, cooled the earth and condemned the dinosaurs, along with 75% of all life on the planet.
But the origins of the dinosaur murder, called Chicxulub, remained a mystery.
Most theories suggest that Chicxulub was a massive asteroid; hundreds of thousands of these rocks sit in a donut-shaped ring between Mars and Jupiter. But in a study published Monday, two Harvard astrophysicists suggested an alternative idea: that Chicxulub was not an asteroid at all, but a piece of shrapnel from an icy comet that was too close to Jupiter’s gravity. sun pressed.
Asteroids and comets are both classified by NASA as space rocks, but they differ in important ways: Comets form from ice and dust outside our solar system and are generally small and fast moving, while rocky asteroids are larger, slower and closer to the sun.
“We suggest that breaking up an object when it comes close to the sun can give rise to the appropriate rate and also the kind of impact the dinosaurs killed,” Avi Loeb, an astrophysicist and cosmologist at Harvard University and co-author of the new study, said in a press release.
The solar system acts as a ‘pinball machine’ for comets
Most asteroids come from the asteroid belt between the inner and outer planets of the solar system. But NASA scientists holding tablets over space objects passing close to Earth have yet to determine where Chicxulub came from.
In the new study, published in the journal Scientific Reports, Loeb and his co-author, Amir Siraj, suggest that Chicxulub did not come from the asteroid belt. Rather, they say that it probably originated outside our solar system, in an area called the Oort Cloud.
Think of the Oort cloud as a ring of 1 trillion pieces of icy debris, which sits outside the farthest corners of the solar system and surrounds it. It is located at least 2,000 times farther from the sun than the earth is. Comets that originate in the Oort cloud are known as long-term comets because it takes so long to complete one orbit around the sun.
But these comets can sometimes be pulled off orbit by the gravity of massive planets like Jupiter. Such an adaptation to an orbit of a comet could bring it on a path much closer to the sun.
“The solar system serves as a kind of pinball machine,” Siraj said in the release.
Comets that come close to the sun are called ‘sungrazers’. The new study calculated that about 20% of the Oort cloud comets are solar eclipses. As they approach our star, gravity begins to pull them apart. Fragments of the comet descend and can look after nearby planets.
According to the authors of the study, this is “a satisfactory explanation for the origin of the impact” that killed the dinosaurs.
The asteroid-against-comet argument has not been resolved
Siraj and Loeb are not the only scientists who think that a comet, not an asteroid, doomed the dinosaurs. A group of researchers from Dartmouth College also suggested in 2013 that a high-speed comet could create the Chicxulub crater.
Chicxulub hit the earth at 43 miles per second, which is about 30 times faster than the speed of a supersonic jet. The resulting 100-mile crater extended to 12 kilometers into the depths of the Gulf of Mexico. Some scientists have estimated that the asteroid’s power was equivalent to 10 billion of the atomic bombs used in World War II.
But not all scientists are convinced that a comet caused the destruction.
Natalia Artemieva, a senior scientist at the Planetary Science Institute in Arizona, told The New York Times that comet fragments from a sonrazer would have been too small to create the Chicxulub crater. And Bill Bottke, a planetary scientist at the Southwest Research Institute in Colorado, suggested that the study overestimate the frequency of sunbathers – and consequently the amount of fragments that comets produce.
Existing evidence favors the idea that Chicxulub was an asteroid, “but it’s not conclusive,” Bottke told the Times. “There’s still winding space if anyone really wants it to be a comet. I just think it’s very difficult to make the case.”
However, Siraj and Loeb said their theory is supported by a type of material that is deep in the Chicxulub crater and other craters in South Africa and Kazakhstan. This substance, carbonaceous chondrite, may have come from comets. While only 10% of the asteroids of the asteroid belt consist of carbonaceous chondrites, the material may ‘possibly be widespread in comets’, the authors of the study wrote.
The only monsters ever collected from a comet in space were brought back in 2006. They revealed that the object, called Wild 2, consists of carbonaceous chondrite.
Finding the right answer in the Chicxulub debate is useful because it can help researchers determine the likelihood of a similar impact event in the future. Only two to three comets from the Oort cloud have hit the Earth in the last 500 million years, according to one study. In contrast, according to the Planetary Society, an asteroid from Chicxulub affects the Earth every hundred million years.
Siraj and Loeb modeled how many comets come near the sun for a long time to throw large fragments in the direction of the earth. Their numbers suggest that ten times more Chicxulub-sized objects hit the earth than scientists previously thought.
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