According to a study, published in the journal Monthly Notices of the Royal Astronomical Society, mass extinctions occurring over the past 260 million years were likely caused by comet/asteroid showers.
For more than three decades, researchers have argued about a controversial hypothesis relating to periodic mass extinctions and asteroid/comet impact craters on Earth.
Dr Ken Caldeira of Carnegie Institution and Dr Michael Rampino of New York University offer new support linking the age of these craters with recurring mass extinctions of life, including the demise of the dinosaurs.
Specifically, they show a cyclical pattern over the studied period, 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 Milky Way 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 our planet.
To test their hypothesis, the team performed time-series analyses of impacts and extinctions using 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,” said Dr Rampino, who is the lead author on the study.
The scientists found that six 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 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.”
“Moreover, five out of the six largest impact craters of the last 260 million years on Earth correlate with mass extinction events,” they said.
“This cosmic cycle of death and destruction has without a doubt affected the history of life on our planet,” Dr Rampino concluded.
Michael Rampino & Ken Caldeira. Periodic impact cratering and extinction events over the last 260 million years. MNRAS, published online October 20, 2015
Source: www.sci-news.com, 2015