Carbon chondrite found in impact craters in many places on Earth confirms the Harvard scientists’ theory of what happened 66 million years ago
A team that includes two Harvard University astronomers has been able to enrich the research debate about the origins of the comet that caused the end of 3 quarters of life on Earth about 66 million years ago, and the possibilities of similar strikes in the future.
The fringes of the solar system
The study – published in the journal Nature, Scientific Reports, and Harvard University published a press release on it on February 15th – stated that the statistical analyzes and gravity simulations conducted by the team showed that what hit the Earth was coming from the Oort cloud. (Oort Cloud).
And the Oort Cloud is the outer boundary of our solar system, and it takes a spherical shape that envelops the entire solar system, and its internal boundaries begin at a distance of 300 billion kilometers from the sun, and it was named so after the German astronomer Jan Auer, who was the first to assume its existence in 1950.
Scientists assume that this cloud contains nearly two trillion objects with a diameter greater than one kilometer, and their orbits around the sun are millions of years, and it is believed that the cause of this region is the tensions and thrusts between the planets in the early stages of formation of the solar system, which pushed some relatively small objects out.
Coming from behind
The prevailing hypothesis was that the huge rock that struck Earth about 66 million years ago in an area now known as the Yucatan Peninsula in Mexico was an asteroid coming from the asteroid belt that lies between Mars and Jupiter.
But the simulations of Harvard researchers, Avi Loeb and Saraj Amir, showed that he was a long-term comet coming from the Oort cloud, and then receiving a boost from the gravity of Jupiter that made it pass from the sun at a close distance.
These small chunks of the comet made there more statistical opportunities for one of them to fall in the path of Earth, which is what actually happened, according to the study. What hit the Earth, then, was not an asteroid, but a piece of crumbs from a comet estimated to be between 10 and 80 kilometers wide.
Astronomers divide comets into two types: a type that has an orbit that completes an orbit around the sun in a period greater than 200 years, and this type is called “long-term comets”, such as Hyakutake and Hale-Bopp. The second type will orbit the sun in less than 200 years, and are called “short-duration comets”, such as Tempel and Encke.
According to the study, long-term comets tend in 20% of cases to approach the sun and partially or completely disintegrate, and thus this raises the probability of hitting Earth 10 times compared to the previous hypothesis, which makes the chance that one of those pieces hits the Earth once every 250 And 370 thousand years.
On the other hand, the study showed that examining the composition of rocks in the collision zone in the Yucatan Peninsula indicated the presence of a large proportion of carbonaceous chondrite, which is present in greater proportions in comets of long duration compared to asteroids in the asteroid belt.
This confirms that other craters – which were due to shocks received by the Earth – contained the same material in large proportions, such as the Friedfort crater that formed two billion years ago in South Africa, which is the largest confirmed crater in Earth’s history, and the Zamanshin Crater in Kazakhstan, which is the largest confirmed crater formed in the last one million years.
Harvard researchers hope that future studies will examine the composition of the lunar craters caused by long-duration comets, to confirm the presence of carbon chondrites in proportions similar to those terrestrial craters, which will help develop our understanding of Earth’s deep past, and thus its future with this kind of risk.