Flames dancing around trees as the ground shakes under a smoky sky. Loud volcanic eruptions and thundering storms result from the impact of the dooming asteroid. One can only imagine what it must have been like, the mass extinction of dinosaurs. As far as we know, about 66 million years ago, a giant rock from space pummeled into the Earth, triggering the end of the dinosaur era. But was the fate of this rock random? What factors pushed this rock to clash with Earth? A study conducted at Harvard University sheds new light on this significant phenomenon (Siraj & Loeb 2021).
Most scientists agree that the mysterious asteroid that resulted in the end of dinosaurs – or more formally, the Cretaceous–Paleogene extinction event – is known as the Chicxulub impactor. Many puzzle pieces of evidence have contributed to the credibility of this asteroid theory, such as the timing of the asteroid’s impact and fossil records, and the unusually high amounts of space metal, iridium, at the time of the extinction. Other factors such as climate change and volcanic activity are also plausible ideas, but many paleontologists argue that these factors only resulted from the impact of the asteroid.
So where did the Chicxulub impactor come from and is it truly an asteroid? Siraj & Loeb (2021) explain that this rock emerged from something called the Oort cloud. This “cloud” is an icy patch of debris on the very edge of the solar system, far, far away from Earth. Rather than a main-belt asteroid, which normally floats along the asteroid orbit between Mars and Jupiter, the researchers theorized that this is actually a broken-apart, “sungrazed” long-period comet. This is because the impact rate of such comets corresponds better to the observed Chicxulub impact than that of main-belt asteroids.
Comets are different from asteroids in that they are made of ice and dust rather than the asteroid-composition of metal. But the comet that ended the dinosaurs was different: it falls in a unique nicknamed group called “sungrazers.” As you can tell, these comets get their name from flying excitingly close to the sun. When this happens, they encounter mighty tidal forces and often break up into smaller rocks in something called a tidal disruption event. Some of these broken-off pieces can make their way back to the Oort cloud at the end of the solar system. Siraj & Loeb (2021) state that when this happens, there is an increased likelihood of one of the comet chunks hitting Earth.
The theory doesn’t stop there. The study’s complex mathematical calculations have concluded that the Chicxulub impactor was perhaps never supposed to crash Earth, but was actually flung off-course by Jupiter’s gravitational field and sent directly to a dinosaur-dominating world. Everything in space is managed by forces, such as the maintenance of planets in their respective orbits, gravity, etc. When meteors and rocks such as the Chicxulub impactor float through a path with a strong enough force, they can be pushed and pulled in completely different directions.
“The Solar System acts as a kind of pinball machine… Jupiter, the most massive planet, kicks incoming long-period comets into orbits that bring them very close to the Sun.”— Amir Siraj, the study’s co-author Harvard University undergraduate student as spoken on BBC Science Focus Magazine.
What is fascinating, nerve-wracking, and scary at the same time is the fact that these sungrazers are still flinging themselves around in the pinball machine that is space. It is possible that planets and other extraterrestrial bodies have been pulling comets and rock chunks away from the Earth, sending them into different trajectories. But it is also possible that someday another giant space rock can be pushed into the direction of our planet and pummel down the way it did 66 million years ago. On that note, perhaps this article stimulated an interest in space movies that you should check out – Gravity, Interstellar, Hidden Figures. Or good, old Zathura: A Space Adventure.
What do you think about the revelations of this astrophysics study? What are some other plausible explanations for what happened to the dinosaurs? Let us know your thoughts in the comments below!
Siraj, A., & Loeb, A. (2021). Breakup of a long-period comet as the origin of the dinosaur extinction. Scientific Reports, 11(1), 1-5.