We all know the tragic image of behemoth ancient beasts staring up at a fateful streak of light bearing down fast. The cataclysmic asteroid strike that Earth withstood 66 million years ago, wiping out nearly every single living, breathing dinosaur on the planet, caused a serious dent in its crust, and rendered the entire globe nearly uninhabitable for thousands of centuries.
In a new research paper and simulation published in the online journal Nature Communications, U.K. scientists led by Imperial College London's Gareth Collins have determined that this doomsday space rock struck our Big Blue Marble at precisely the best angle to inflict maximum damage, in a perfect storm of conditions which triggered the Cretaceous-Paleogene mass extinction.
Lurking beneath the Yucatán Peninsula and the Gulf of Mexico, the buried Chicxulub crater spans more than 90 miles in diameter. It was created when an errant 6-mile-wide asteroid or comet collided with Earth to end the Age of Dinosaurs, along with most every species of flying reptiles known as pterosaurs. This new study estimates the steep trajectory of the Chicxulub impactor to have been a "just-right" Goldilocks-style angle from horizontal, setting up the ideal situation for detonating millions of tons of vaporized rock into the sky.
Reconstructing that impact with measurements and data collected directly from the Chicxulub crater, Collins and his crew discovered that the unwanted cosmic intruder blasted into our atmosphere at a blazing 20 kilometres per second before hitting home.
"The Chicxulub impact triggered a mass extinction because it threw up huge quantities of dust and gas out of the crater and ejected this material fast enough to disperse around the globe," Collins tells SYFY WIRE. "Our work shows that the asteroid that struck Earth to form the Chicxulub crater followed a trajectory from NE to SW and collided at a steep angle to the surface — about 60 degrees above the horizon. The angle of attack is important, because it dictates how lethal the blow was. A 60-degree impact angle is a more lethal because it ejects more material fast enough to engulf the planet — even steeper impacts might make a bigger crater, but they throw out debris more slowly so most of it does not get as far; very grazing impacts, on the other hand, don’t generate anywhere near as much debris."
"An older idea was that the impact angle was much shallower and the asteroid came from a different direction (from the SE)," Collins explains further. "Our work suggests a different direction and angle based on observations that show that the crater’s central uplift is leaning slightly to the southwest and our new 3D numerical simulations of the impact that are consistent with these observations. Everyone knows that the day of the Chicxulub impact was a bad day for the dinosaurs — our work shows it was even worse. The impact was a perfect storm."
"What is most remarkable is that anything survived at all and how rapidly life recovered, albeit without the dinosaurs," Collins adds. "Our work provides the starting point for understanding the knock on effects of the impact on the climate and food chain, but much more work remains to be done to fully understand the immediate and longer-term aftermath of the impact and the subsequent chain of events that led to the mass extinction and then recovery."