Mass Extinctions Occur Every 27 Million Years

Scientists identified 19 major mass extinctions taking place as far back as 500 million years ago.
Mass Extinctions Occur Every 27 Million Years
A mass extinction of life takes place every 27 million years on Earth, according to a study by U.S. researchers.(Kevork Djansezian/Getty Images)
2/23/2011
Updated:
10/1/2015
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A mass extinction of life takes place every 27 million years on Earth, according to a study by U.S. researchers.(Kevork Djansezian/Getty Images)
A mass extinction of life takes place every 27 million years on Earth, according to a study by U.S. researchers. The next mass extinction is due in around 16 million years, give or take a few million years.

Physicist Adrian Melott from the University of Kansas and paleontologist Richard Bambach from the Smithsonian Institution in Washington, D.C., published their paper, Nemesis Reconsidered, in the Monthly Notices of the Royal Astronomical Society in September 2010.

They said their findings are inconsistent with the “Nemesis” (or “death star”) theory, which predicts the existence of a dark companion star to the sun, which is responsible for sending showers of deadly comets into the solar system each time it crosses the Oort Cloud (a cloud of comets circling the solar system).

The scientists identified 19 major mass extinctions taking place as far back as 500 million years ago, 10 of which occurred less than 3 million years before or after the moment predicted by a 27-million-year cycle.

This includes the extinction of dinosaurs 65.5 million years ago, which took place three cycles ago almost exactly on cue. Each event caused the extinction of 10 percent to 60 percent of all species. The scientists are a little more than 99 percent sure the events were not random.

The Nemesis theory was first put forward by paleontologists in 1984 to explain periodical mass extinctions. According to Melott and Bambach, the orbital period of such a star should have changed by 15 percent to 30 percent over the last 500 million years.

Other research papers have stated that the star would take 4 percent longer to complete its orbit each time, owing to perturbations from passing stars and from the galaxy’s tidal gravitational field.

“The fossil record is inconsistent with perturbations expected in the orbit of a dark Solar companion,” Melott and Bambach wrote in their paper.

If Nemesis does exist, a NASA space telescope called WISE (Wide-field Infrared Survey Explorer), launched in January 2009, could have detected it. It will take scientists until mid-2013 to analyze the results of its search for distant objects in the infrared spectrum, which ended in October 2010 when the telescope’s coolant ran out.

The telescope scanned the sky twice to generate time-lapsed images. If a distant object moved between the times of the two scans, scientists can use the pictures to deduce its location and orbit.

Melott and Bambach did not offer an alternative explanation to Nemesis for these periodical mass extinctions, which remain a mystery.

Read the research paper at http://ow.ly/3XU2R