For >30 years, scientists have argued about a controversial hypothesis relating to periodic mass extinctions and impact craters – caused by comet and asteroid showers – on Earth. Now scientists have concluded that mass extinctions occurring over the past 260 million years were likely caused by comet and asteroid showers.
A graph showing how the rate of cratering has changed on Earth over time. The arrows indicate the dates of mass extinctions. Credit: Michael Rampino / NYU
Michael Rampino, NYU geologist, and Ken Caldeira, a scientist in the Carnegie Institution’s Department of Global Ecology, offer new support linking the age of these craters with recurring mass extinctions of life, including the demise of the dinosaurs. T show a cyclical pattern, with both impacts and extinction events taking place every 26 million years.
This cycle has been linked to periodic motion of the Sun and planets through the dense mid-plane of our galaxy. Scientists have theorized that gravitational perturbations of the distant Oort comet cloud that surrounds the Sun lead to periodic comet showers in the inner solar system, where some comets strike Earth.
To test their hypothesis, Rampino and Caldeira performed time-series analyses of impacts and extinctions using newly available data offering more accurate age estimates. “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,” says Rampino.
Specifically, he and Caldeira found that 6 mass extinctions of life during the studied period correlate with times of enhanced impact cratering on Earth. One of the craters considered in the study is the large (180 km diameter) Chicxulub impact structure in the Yucatan, which dates to about 65 million years ago, the time of a great mass extinction that included the dinosaurs + 5 out of 6 largest impact craters of the last 260 million years on earth correlate with mass extinction events.
“This cosmic cycle of death and destruction has without a doubt affected the history of life on our planet,” Rampino observes. http://www.ras.org.uk/news-and-press/2729-scientists-find-link-between-comet-and-asteroid-showers-mass-extinctions
An artist’s illustration of a major asteroid impact on Earth. Credit: NASA
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