Earth may have once had rings like Saturn does, say university researchers. Image: stock.
Monash University researchers believe they have found evidence that Earth may have had a ring system like Saturn’s about 466 million years ago.
This was at the start of a period of unusually intense meteorite bombardment, known as the Ordovician impact spike, the Melbourne-based university said.
This hypothesis, published in the bimonthly peer-reviewed Earth and Planetary Science Letters journal, stems from plate tectonic reconstructions for the Ordovician period which detected the locations of 21 asteroid impact craters.
A university statement noted that these craters are located within 30 degrees of the equator despite over 70 per cent of Earth’s continental crust lying outside this region.
The research team believes this localised impact pattern was produced after a large asteroid had a close encounter with Earth, broke up and formed a debris ring.
“Over millions of years, material from this ring gradually fell to Earth, creating the spike in meteorite impacts observed in the geological record,” says lead study author Professor Andy Tomkins, from Monash University’s School of Earth, Atmosphere and Environment.
“We also see that layers in sedimentary rocks from this period contain extraordinary amounts of meteorite debris.”
“What makes this finding even more intriguing is the potential climate implications of such a ring system,” Prof Tomkins says.
“The researchers speculated that the ring could have cast a shadow on Earth, blocking sunlight and contributing to a significant global cooling event known as the Hirnantian Icehouse.”
This period, which occurred near the end of the Ordovician, is recognised as one of the coldest in the last 500 million years of Earth’s history.
“The idea that a ring system could have influenced global temperatures adds a new layer of complexity to our understanding of how extra-terrestrial events may have shaped Earth’s climate,” Professor Tomkins said.
Normally, asteroids impact the Earth at random locations hence impact craters distributed evenly over the Moon and Mars, for example, the university says.
To learn if the spread of Ordovician impact craters is non-random and closer to the equator, the researchers calculated the continental surface area capable of preserving craters from that time.
Using a GIS approach (Geographic Information System), they identified geologically suitable regions across different continents like Western Australia, Africa, the North American Craton, and small parts of Europe.
Only 30 per cent of the suitable land area was found to have been close to the equator yet all impact craters from this period were found in this region. The chances of this happening are like tossing a three-sided coin and getting tails 21 times, the university said.
