Earth might once have twirled under a sky ringed by a colossal debris halo, scientists propose. It reads like science fiction, yet a team of Australian planetary scientists suggests Earth could have looked something like Saturn around 466 million years ago. A large asteroid skimmed past Earth, shattering and scattering fragments that briefly formed a ring around our planet. Over tens of millions of years, those pieces rained down, gradually reshaping Earth’s surface long before life had fully escaped the oceans and just before a mass extinction event.
The scenario evokes art imitating nature, much like a scene from Caza’s cult comic The World of Arkadi, where Earth’s Moon bursts apart to forge a bright ring. Aristotle’s maxim that art imitates life is echoed by geologist Andrew Tomkins and colleagues Erin Martin and Peter Cawood in their Earth & Planetary Science Letters study. They propose that nature may have mirrored a dramatic artistic vision, this time in the form of a planetary ring around Earth.
Their research suggests that for tens of millions of years during the Ordovician period, Earth could have been encircled by a shimmering ring of debris. This ring might help explain several enduring geological puzzles.
A flood of exotic meteor showers during the Ordovician
Tomkins notes that 21 major meteorite impact craters date to the middle Ordovician (roughly 485 to 444 million years ago). It was a tumultuous era, marked by extensive glaciation and one of the planet’s five greatest mass extinctions. Many of these impacts align with evidence of ancient tsunamis preserved in sediment layers containing unusual rock mixtures.
Even more intriguing are limestone formations across Europe, Russia, and China from the same period, which host unusually high levels of certain meteorite fragments. These materials were exposed to cosmic rays for shorter periods than typical meteorites, implying they originated from a shattered asteroid in the main belt that continuously rained debris onto Earth for immense spans of time.
Craters clustered near the equator
To probe further, Tomkins and his team reconstructed Ordovician paleogeography by retracing continental drift. The findings were striking: all 21 large craters cluster near the equator. Was this a coincidence or a geological fluke? When The Conversation summarized the team’s approach, they noted that only about 30% of Earth’s land during that era lay near the equator. If impacts were evenly spread, more craters would be found away from the equator. The most plausible conclusion is that debris consistently fell from a ring orbiting Earth, similar in principle to Saturn’s rings.
A planetary ring, a Roche limit, and the possibility of cooling
Is this scenario physically possible? The researchers argue that it is. Their model envisions an asteroid passing so close to Earth that it crosses the Roche limit—the distance at which tidal forces from a larger body tear a smaller one apart. This is the same dynamic that split Comet Shoemaker-Levy 9 before it plunged into Jupiter in 1994. Once shredded, the fragments could settle into an equatorial ring, creating a stable ring system that endured for millions of years.
Could such a ring have cooled the planet?
Tomkins adds an intriguing twist: if the ring orbited along Earth’s equator, it would cast shadows across parts of the globe, reducing sunlight at the surface and potentially driving long-term cooling. Indeed, global temperatures began to fall around 465 million years ago, and by about 445 million years ago Earth entered the Hirnantian ice age—the coldest interval in the last 500 million years.
Might a temporary ring have sparked that deep freeze? The researchers aim to model how such asteroid rings form, evolve, and influence climate. If their data hold up, this ancient ring may not only have circled Earth but also helped steer the course of life on our planet.
Laurent Sacco
Journalist
I was raised in Vichy in 1969, during the height of the space race, and my curiosity about space, physics, and epistemology grew alongside that era’s discoveries. I studied particle physics at Blaise-Pascal University in Clermont-Ferrand, while also exploring geosciences and paleontology. My career at Futura focuses on quantum theory, black holes, cosmology, and astrophysics, with ongoing interest in exobiology, volcanology, mathematics, and energy topics.
I have interviewed leading scientists such as Françoise Combes, Abhay Ashtekar, and Aurélien Barrau, and I've pursued advanced astrophysics studies at the Paris and Côte d’Azur Observatories. Since 2024, I’ve served on the Cosmos prize scientific committee, continuing to engage with both Western and Eastern scientific traditions that shaped my early learning.
