Scientists have long theorized that the dinosaurs met their demise at the hands of a giant asteroid, but the circumstances of such an event have thus far remained murky. Now, a team of American and European researchers have shed new light on the incident, lending extra weight to an already widely-adopted theory.
Researchers have spent years trying to find a direct connection between the Cretaceous-Tertiary extinction event (K-T, for short) and cosmic collision. They found a lead in the late 1970s, when geophysicist Glen Penfield discovered a giant prehistoric crater near the town of Chicxulub in Mexico. At more than 110 miles wide, the crater provided evidence of an utterly massive impact — one that would have released an explosion one billion times stronger than the atomic bombs dropped on Hiroshima and Nagasaki during World War II. The only problem, however, was figuring out whether this asteroid's collision actually coincided with the extinction of the dinosaurs.
Tsunamis, dust clouds, and firestorms
Previous studies have estimated that the Chicxulub asteroid struck some 300,000 years before the dinosaurs' demise, leading some to suspect alternative causes for their extinction. But a study published this week shows that the two events happened no more than 33,000 years apart — a small margin when considering time on such a large scale. Researchers arrived at their findings after conducting high-precision radiometric dating of debris near Chicxulub, providing strong evidence that the dinosaurs died off as a direct result of the asteroid's impact.
"We've shown the impact and the mass extinction coincided as much as one can possibly demonstrate with existing dating techniques," Paul Renne, study co-author and director of the Berkeley Geochronology Center, told LiveScience. The asteroid in question is believed to have been six miles wide, and its impacts were likely devastating, blocking out the sun with a thick cloud of dust, unleashing mega-tsunamis across the world, and possibly igniting massive firestorms. The collision alone is believed to have wiped out 75 percent of life on Earth.
Renne was quick to note, however, that the dinosaurs' extinction can't be attributed to the cosmos, alone. Earth's climate was already reaching a tipping point before the asteroid ever hit, leading to long cold snaps and volcanic eruptions. "The impact was clearly the final straw that pushed Earth past the tipping point," Renne said. "We have shown that these events are synchronous to within a gnat's eyebrow, and therefore, the impact clearly played a major role in extinctions, but it probably wasn't just the impact."