Breakup of an asteroid passing within Earth’s Roche limit likely formed the debris ring during the middle Ordovician period, according to new research from Monash University.
Tomkins et al. suggest that a large chondrite asteroid had a near miss encounter with Earth 466 million years ago, which caused it to break up as it passed through Earth’s Roche limit.
All large planets in our Solar System have rings, and it has been suggested that Mars may have had a ring in the past.
This raises the question of whether our home planet also had a ring system in the past.
In new research, Monash University’s Professor Andy Tomkins and his colleagues examined the positions of 21 asteroid impact craters from a 40-million-year period of enhanced meteor impact cratering known as the Ordovician impact spike.
All these craters are located within 30 degrees of the equator, despite over 70% of Earth’s continental crust being outside this region, an anomaly that conventional theories cannot explain.
The researchers believe 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,” Professor Tomkins said.
“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 extraterrestrial events may have shaped Earth’s climate,” Professor Tomkins said.
The team’s findings appear in the journal Earth and Planetary Science Letters.
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Andrew G. Tomkins et al. 2024. Evidence suggesting that Earth had a ring in the Ordovician. Earth and Planetary Science Letters 646: 118991; doi: 10.1016/j.epsl.2024.118991
