Earth may have had a ring system 466 million years ago, study finds

Image credit: planetary.org

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The Earth’s polar regions are associated with geomagnetic forces i.e. magnetic north and south, but are there any equator-related (west-east) forces? One at least, as Wikipedia says : ‘The ring current system consists of a band, at a distance of 3 to 8 Earth radii, which lies in the equatorial plane and circulates clockwise around the Earth (when viewed from the north). The particles of this region produce a magnetic field in opposition to the Earth’s magnetic field and so an Earthly observer would observe a decrease in the magnetic field in this area.’ The article mentions Saturn’s rings, which clearly align with that planet’s equator, and looks at ‘potential climate implications’ of Earth having had something similar. The research determined that of all the places on Earth where craters should have been preserved ‘only 30% of the suitable land area was determined to have been close to the equator, yet all the impact craters from this period were found in this region.’ (NB the Van Allen radiation belts also have some affinity with the equator.)
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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 around 466 million years ago, at the beginning of a period of unusually intense meteorite bombardment known as the Ordovician impact spike, says Phys.org.

This surprising hypothesis, published in Earth and Planetary Science Letters, stems from plate tectonic reconstructions for the Ordovician period noting the positions of 21 asteroid impact craters.

All these craters are located within 30 degrees of the equator, despite more than 70% of Earth’s continental crust being 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 within Earth’s Roche limit, it broke apart due to tidal forces, forming a debris ring around the planet—similar to the rings seen around Saturn and other gas giants today.

“Over millions of years, material from this ring gradually fell to Earth, creating the spike in meteorite impacts observed in the geological record,” said 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,” he said.

The researchers speculate 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 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 extra-terrestrial events may have shaped Earth’s climate,” Professor Tomkins said.
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Could similar rings have existed at other points 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, providing new insights into the dynamic interactions between our planet and the wider cosmos.

Full article here.
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Image credit: planetary.org