The asteroid impact that wiped out the dinosaurs may not have been an isolated event; showers of asteroids and comets striking the Earth during a period lasting 260 million years may have caused recurring mass extinction events, researchers suggest.
A hypothesis linking mass extinctions with impact craters on the Earth considered signs of such showers has been controversial and the subject of arguments for more than 30 years.
A new published paper is adding more evidence by linking the ages of the craters with episodes of mass extinctions, including the disappearance of the dinosaurs.
The study has identified a cyclical pattern during those millions of years, with impact craters along with extinction episodes seeming to occur about every 26 million years, says Michael Rampino, a New York University geologist, and Ken Caldeira, a scientist in the Carnegie Institution's Department of Global Ecology.
That cycle may be tied to periodic movements of our sun and our solar system's planets through our galaxy's dense middle plane, they suggest.
That periodic movement may cause gravitational disturbances in the far-off Oort comet cloud on the outskirts of our solar system, sending a shower of comets into the inner solar system that then impact the Earth, they propose.
Newly-gathered data that gives more accurate estimates of the ages of impact craters on the Earth and of extinction events supports their hypothesis, they say.
"The correlation between the formation of these impacts and extinction events over the past 260 million years is striking and suggests a cause-and-effect relationship," Rampino says.
At least six mass life extinctions during the period studied can be correlated with episodes of increased impact cratering on the Earth, Rampino and Caldeira say.
In addition, five of the six largest single impact craters from the last 250 million years can be correlated with distinct extinction events, they say.
Those include the 110-mile wide Chicxulub impact structure off the Yucatan Peninsula, dating to around 65 million years ago — and to the mass extinction event that ushered dinosaurs off the face of the Earth.
"This cosmic cycle of death and destruction has without a doubt affected the history of life on our planet," Rampino says.
The study appears in the Monthly Notices of the Royal Astronomical Society.
