Paleontologists and dinosaur nerds have long debated what killed off the "terrible lizards"—one meteor or many, volcanoes, or something else. Now one researcher says he has the answer: an asteroid believed to be about six miles wide that landed in the Caribbean about 66 million years ago. The Chicxulub impact was first floated as a theory in 1980, but as a Princeton professor explains to NPR, "If [the impact] is the cause, it had to be precisely at the time of the mass extinction. It can't be before and it can't be afterwards." And as LiveScience notes, previous research suggested the asteroid hit 300,000 years before or 180,000 years after the mass extinction event. Now, a researcher says the asteroid and die-off happened "within a gnat's eyebrow" of each other, reports the AFP.
Paul Renne, a University of California geologist, performed high-precision radiometric dating on ash deposited above fossils buried in Montana and on glass blobs found around the Chicxulub crater to determine the age of the events. "And lo and behold they are exactly the same," Renne says. The analyzed ash suggests the mass die-off occurred about 66,043,000 years ago, while the asteroid hit approximately 66,038,000 years ago. "Considering the statistical errors," the two events "may have occurred no more than 32,000 years apart," reports Science, where the study was published. "When I got started in the field, the error bars on these events were plus or minus a million years," marvels one scientist. (Click for another big dinosaur find.)