Asteroid impacts on Earth are random
For several decades, researchers have debated the frequency, or periodicity, of large asteroid impacts on Earth, and the link between them and mass extinctions on our planet. A study from 2015 proposes a periodicity of 26 million years. One explanation for the proposed periodicity is a “companion star” to the sun, called Nemesis. It was suggested that Nemesis approached the sun with a periodicity of 26 million years, causing an increased inflow of asteroids to Earth.
“In our study, we can see that asteroid impacts on Earth do not occur with a periodic interval of 26 million years, or any other time period for that matter”, says Sanna Alwmark, geologist at the Faculty of Science at Lund University.
In their study, the researchers have applied a statistical method of analysis based on a database of impact craters with precise ages, where the craters on Earth were formed within the last 500 million years. The method makes it possible to see whether the impacts on Earth have occurred at a particular frequency or at random.
“Our study also shows that the conclusions in the study from 2015 were drawn on the basis of impact craters for which the age had not been determined with sufficient precision. Furthermore, Nemesis – the star behind the theory – has never been found”, says Sanna Alwmark.
The occurrence of so-called cluster, or merger, impacts which form craters of almost the same age may be what led to the previous assumptions. Some of these craters, however, may have formed simultaneously, for instance, from the impact of asteroids with moons on Earth.
“According to the Nemesis theory, the next major impact, and perhaps mass extinction, will take place 10 million years from now, but based on asteroid impact, this is highly unlikely”, says Sanna Alwmark.
The present study is published in the scientific journal Monthly Notices of the Royal Astronomical Society.
Text: Dragana Trivic