Comet or asteroid: What killed the dinosaurs and where did they come from?

It changed history forever when it fell to Earth about 66 million years ago.

The conqueror left the so-called Chicxulub, behind a crater off the coast of Mexico that spans 93 miles and runs 12 miles deep. Its devastating effect brought an abrupt end to the management of dinosaurs with their sudden extinction, along with the end of nearly three-quarters of the plant and animal species that live on the Land.

The enduring puzzle: Where did the asteroid or comet come from, and how did it come to hit Earth? Now, a pair of researchers at the Center for Astrophysics | Harvard & Smithsonian believe they have the answer.

In a study published today in Nature’s Scientific Reports, Harvard University astronaut undergraduate student Amir Siraj and astronaut Avi Loeb came up with a new theory that could explain the origin and course of this catastrophic object.

Using statistical analysis and gravity simulations, Siraj and Loeb conclude that a large fraction of long-range comets from the Oort cloud, a frozen area of ​​debris at the edge of the solar system, can be off-course collision with Jupiter gravitational field during orbit.

“The solar system works like a kind of pinball instrument,” explained Siraj, who pursues bachelor’s and master’s degrees in astronomy, as well as a master’s degree in piano performance at the Conservatoire of Music New England. “Jupiter, the largest planet, kicks long-distance comets into orbits that bring them very close to the sun.”

When in close proximity to the sun, the comets – nicknamed the “sungrazers” – can experience powerful tidal forces that break up pieces of rock apart and at the end. over there, extracting silver shrapnel.

“In a sunny event, the portion of the comet closer to the sun feels a stronger gravitational pull than the later part, leading to a tidal force throughout the object,” he says. Siraj says. “You’ll find something called a tidal riot event, in which a large comet breaks up into much smaller pieces. And crucially, on the way back to Oort’s cloud, there’s an improved probability of collision. one of those fragments on Earth. “

The new calculation from Siraj and Loeb ‘s theory increases the chances of long – term comets affecting the Earth by a factor of about 10, and shows that about 20 percent of long – term comets ‘become the sungrazers.

The pair say their new level of influence is consistent with Chicxulub’s age, providing a satisfactory explanation for its origins and other such influencers.

“Our paper is the basis for explaining what happened in this incident,” Loeb says. “We recommend, of course, that if you break an object as it approaches the sun, that it could cause the appropriate incident rate and also the kind of impact that killed the dinosaurs. “

Evidence found at the Chicxulub crater shows that the rock was composed of carbonaceous chondrite. Siraj and Loeb’s hypothesis may explain this strange situation.

A popular theory about the origin of Chicxulub claims that the conqueror came from the main belt, which is the number of asteroids between the orbit of Jupiter and Mars. However, carbonaceous chondrites are very rare among main-zone asteroids, but perhaps very widespread among long-lived comets, further supporting the notion of financial impact.

Other similar craters display the same writing. This includes an object that struck about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest pit ever excavated in history. of the Earth, and the conqueror who left the Zhamanshin crater in Kazakhstan, which is the largest crater tested inside the last one. million years. The researchers say the timing of these impacts supports their calculation of the expected rate of Chicxulub-sized comets.

Siraj and Loeb say that their hypothesis can be confirmed by further study of these pits, others like them, and even those on the surface of the moon to find out the composition of the effect. Comets sampling space missions can also help.

In addition to the composition of the comets, the new Vera Rubin Observatory in Chile may see a tidal wave of long-running comets after operating next year.

“We should see smaller fragments coming to Earth more often from the Oort cloud,” Loeb says. “Hopefully we can test the theory by getting more data on long-term comets, getting better statistics, and maybe seeing evidence for some snippets.”

Loeb says that understanding this is not just crucial to unraveling the mystery of Earth’s history but that it could be very important if an event like this were a threat to the planet.

“It must have been an amazing sight, but we don’t want to see that again,” he said.

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This work was supported in part by the Harvard Origins of Life Initiative and the Breakthrough Prize Foundation.

About the Astrophysics Center Harvard & Smithsonian

Astrophysics Center Harvard & Smithsonian is a collaboration between Harvard and the Smithsonian designed to ask – and ultimately answer – the most pressing questions humanity has about the nature of the universe. The Astrophysics Center is headquartered in Cambridge, MA, with research facilities throughout the U.S. and around the world.