The coast of the Mexican province of Yucatan hides the trace of one of the most momentous events in the history of the Earth. There a huge rock from space crashed 66 million years ago. The brutal crash caused an explosion equivalent to that of ten billion atomic bombs like the one in Hiroshima. Sulfur expelled into the atmosphere blocked sunlight, gigantic fires raged through forests, and a chilling tsunami occurred. The planet’s climate changed for years, wiping out three-quarters of the then-existing plant and animal species. But above all, the event is known to put an end to the reign of the dinosaurs.
The nature and origin of the rock that caused this extinction has been the subject of deep debate, with a member of the asteroid belt between Mars and Jupiter being the main suspect until now.
But Harvard University astrophysicist Avi Loeb, famous for his controversial theories about the artificial origin of the first interstellar body ever observed, believes someone else was to blame. As he explains with the student Amir Siraj in the journal ‘Scientific Reports’, it is a piece of a comet arrived by a kind of cosmic carambola from the Oort cloud, an icy sphere of debris on the edge of the solar system. A pinball machine Using statistical analysis and gravitational simulations, Siraj and Loeb calculate that a significant fraction of long-period comets originating in the Oort cloud can be deflected by Jupiter’s gravitational field during its orbit.
“The solar system acts like a kind of pinball machine,” explains Siraj. “Jupiter, the most massive planet, propels long-period incoming comets into orbits that bring them very close to the sun.” During that hit, comets, dubbed “solar scrapers,” can experience powerful tidal forces that break the rock into pieces and ultimately produce cometary shrapnel.
In a solar scrape event, the part of the comet closest to the sun feels a stronger gravitational pull than the part farther away, resulting in a tidal force through the object, ”says Siraj. That causes a large kite to break into many smaller pieces. “Most importantly, on the journey back to the Oort cloud, there is a greater chance that one of these fragments will hit Earth,” he says.
Their calculations increase the chances that these commits will impact our planet by a factor of about 10 and show that 20% of them become solar scrapers.Suitable composition, The researchers believe their calculations are consistent with the age of the Chicxulub crater, the massive 149 km long, and 19 deep seam left in Mexico by the rock strike. “We’re suggesting that if you break an object when it gets close to the sun, it could lead to the right event rate and also the kind of impact that killed the dinosaurs,” says Loeb.
There is something else that fits. Evidence found at Chicxulub suggests that the rock was composed of carbonaceous chondrite, which is rare among main-belt asteroids, but possibly very common among long-period comets, providing additional support for the cometary impact hypothesis. Other similar craters show the same composition. This includes an object that struck about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth’s history (there is a supposedly largest one in Greenland), and the impactor that left the one in Zhamanshin in Kazakhstan, the largest in the last million years. Siraj and Loeb note that their hypothesis can be tested by further studying these craters, others like them, and even those on the moon’s surface to determine the composition of impactors.
Comet sampling space missions can also help. Future threat, The new Vera Rubin Observatory in Chile, which comes online next year, can also help. “We should see smaller fragments reaching Earth more frequently from the Oort cloud,” says Loeb. I hope we can test the theory by having more data on long-period comets, get better statistics and maybe see evidence for some fragments,” he says. Loeb says that understanding this is not only crucial to solving a mystery in Earth’s history, but it could also prove critical if a new space crash threatens the planet. “The image must have been incredible – he says about the impact of the rock that killed the dinosaurs – but we don’t want to see it again.”
