Mass extinctions linked to comet and asteroid showers

October 22, 2015

Mass extinctions occurring over the past 260 million years were likely caused by comet and asteroid showers, a new study concludes. An artist’s illustration of a major asteroid impact on Earth. (credit: NASA/Don Davis)

Mass extinctions occurring over the past 260 million years were likely caused by comet and asteroid showers, scientists conclude in a new study published in an open-access paper in Monthly Notices of the Royal Astronomical Society.

For more than 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.

In their MNRAS paper, Michael Rampino, a New York University 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 every 26 million years, including the demise of dinosaurs.

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 the Earth.

Crater formation rate per million years, with eight significant extinction events shown with solid arrows and two potential extinction events shown with broken arrows (credit: Michael R. Rampino and Ken Caldeira/MNRAS)

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.

The sinkholes clustered around the trough of the Chicxulub crater suggest a prehistoric oceanic basin in the depression left by the impact. (credit: NASA)

One of the craters considered in the study is the large (180 km diameter) Chicxulub impact structure in the Yucatan, which dates at about 65 million years ago — the time of a great mass extinction that included the dinosaurs. And five out of the six largest impact craters of the last 260 million years on earth correlate with mass extinction events.

Abstract of Periodic impact cratering and extinction events over the last 260 million years

The claims of periodicity in impact cratering and biological extinction events are controversial. A newly revised record of dated impact craters has been analyzed for periodicity, and compared with the record of extinctions over the past 260 Myr. A digital circular spectral analysis of 37 crater ages (ranging in age from 15 to 254 Myr ago) yielded evidence for a significant 25.8 ± 0.6 Myr cycle. Using the same method, we found a significant 27.0 ± 0.7 Myr cycle in the dates of the eight recognized marine extinction events over the same period. The cycles detected in impacts and extinctions have a similar phase. The impact crater dataset shows 11 apparent peaks in the last 260 Myr, at least 5 of which correlate closely with significant extinction peaks. These results suggest that the hypothesis of periodic impacts and extinction events is still viable.