Earth may have had a ring system 466 million years ago

In a discovery that challenges our understanding of Earth’s ancient history, researchers have found evidence suggesting that Earth may have had a ring system that formed about 466 million years ago, at the start of a period of unusually intense meteorite bombardment known as the Ordovician Impact Peak.

This surprising hypothesis, published in Letters on Earth and Planetary Sciencesresults from plate tectonic reconstructions for the Ordovician period, noting the positions of 21 asteroid impact craters. All of these craters are located within 30 degrees of the equator, although more than 70% of the Earth’s continental crust lies outside this region, an anomaly that conventional theories cannot explain.

The research team believes this localized impact pattern was produced after a large asteroid had a close encounter with Earth. As the asteroid passed Earth’s Roche limit, it broke apart under tidal forces, forming a ring of debris around the planet, similar to the rings seen today around Saturn and other gas giants.

“Over millions of years, material from this ring gradually fell to Earth, creating the peak of meteorite impacts seen in the geological record,” said Professor Andy Tomkins, lead author of the study and from Monash University’s School of Earth, Atmosphere and Environment. “We also found that sedimentary rock layers from this period contain extraordinary amounts of meteorite debris.”

“What makes this discovery even more intriguing are the potential climate implications of such a ring system,” he said.

Researchers hypothesize that the ring may have cast a shadow on Earth, blocking sunlight and contributing to a major global cooling event known as the “Hirnantian Icehouse.”

This period, which occurred towards the end of the Ordovician, is recognized 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 extraterrestrial events may have shaped Earth’s climate,” Professor Tomkins said.

Normally, asteroids hit the Earth at random locations. Impact craters are observed evenly distributed on the Moon and Mars, for example. To determine whether the distribution of Ordovician impact craters is not random and closer to the equator, the researchers calculated the continental surface capable of preserving craters from this period.

They focused on stable, undisturbed cratons with rocks older than the Middle Ordovician, excluding areas buried under sediment or ice, eroded regions, and those affected by tectonic activity. Using a GIS (Geographic Information System) approach, they identified geologically suitable regions on different continents.

Regions such as Western Australia, Africa, the North American Craton, and small parts of Europe were considered suitable for the preservation of such craters. Only 30% of the suitable land area was determined to be near the equator, but all impact craters from this period have been discovered in this region.

The odds of this happening are comparable to tossing a three-sided coin (if such a thing existed) and getting 21 tails.

The implications of this discovery extend beyond geology, prompting scientists to reconsider the broader impact of celestial events on Earth’s evolutionary history. It also raises new questions about the potential for other ancient ring systems that could have influenced the development of life on Earth.

Could similar rings have existed at other times in our planet’s history, affecting everything from climate to the distribution of life? This research opens a new frontier in the study of Earth’s past, offering new insights into the dynamic interactions between our planet and the cosmos as a whole.