It’s a story we all know. 66 million years ago, the earth would have been struck by an asteroid 11 to 81 km in diameter, which would have destroyed up to 75% of all life on earth. This impact also left its mark: the Chicxulub crater. The latter is located in Chicxulub Puerto on the Yucatán peninsula off the Mexican coast and has a diameter of about 177 kilometers and a depth of about 20 kilometers.
So far, however, we don’t know where the asteroid that led to its formation and the extinction of dinosaurs came from. Two scientists at the Harvard-Smithsonian Center for Astrophysics now believe they have the answer.
A fragment of a comet?
First, the study suggests that the celestial body may not have been an asteroid. It was published on February 15 in the journal Nature.com and suggests that it could be a fragment of a comet. In their article, Amir Siraj and Avi Loeb evoke a theory that the comet originated in the Oort Cloud, a large hypothetical spherical group of bodies located about 50,000 astronomical units from the Sun far beyond the Kuiper Belt. The trajectory of this comet would have been influenced by the gravitational force of Jupiter and the solar tide.
A destructive tidal force
According to Siraj, an astrophysics student at Harvard University, the solar system acts like a kind of pinball machine. The collision could therefore result from this mechanism. “Jupiter, the most massive planet in the solar system, places non-periodic comets in orbits that bring them very close to the sun,” he said, our colleagues at Scitechdaily.com report.
It turns out that with grazing comets (sunburn), the part closest to the Sun experiences an attraction that is greater than that applied to the more distant face. This creates a tidal force that acts on the object itself, breaking it down into several parts.
Fragments of a comet entering the earth’s atmosphere (artist’s drawing). Image credit: Shutterstock / AuntSpray
A high likelihood of impact
On their way back to the Oort Cloud, this debris can collide with the earth. Calculations have shown that about 20% of long-period (non-periodic) comets split into several parts due to the gravitational pull of the sun, which increases the likelihood of impacting the blue planet by a factor of 10.
A rate that would consistently explain what happened to dinosaurs tens of millions of years ago. “Our study provides a basis for explaining how this event occurred,” said Avi Loeb, Harvard astronomer and co-author of the article.