Did Earth Once Have a Ring Like Saturn? Geologists Find Evidence for a Halo of Orbiting Space Rocks 466 Million Years Ago

During a tumultuous period for our planet around 466 million years ago, Earth was pelted with meteorites and rocked by tsunamis. But geologists have uncovered some strange things about this moment in history. For one, sedimentary rocks from that time have a stunningly high amount of meteorite debris. And that debris shows signs of having been exposed to space radiation for much less time than the average meteorite that burns through our skies today. Then, about one million years later, Earth experienced the Hirnantian Ice Age, one of the planet’s coldest time periods in the last 500 million years.

Now, scientists suggest these mysterious occurrences might all be explained by one thing: a ring. The team, whose research was published online last week in the journal Earth and Planetary Science Letters, suggests that almost half a billion years ago, Earth may have had a ring, just like Saturn.

“The existence of such a ring, forming around 466 million years ago and persisting for a few tens of millions of years, could explain several puzzles in our planet’s past,” lead author Andrew G. Tomkins, a geologist at Monash University in Australia, writes in the Conversation.

I’m loving some of the artwork and comic responses to our Earth ring paper (https://t.co/ui6O7qnE3g). Here’s an awesome one from Oliver Hull. pic.twitter.com/J5uQMhOcQ5

— Andy Tomkins (@ProfAndyTomkins) September 17, 2024

The first clue came from a series of 21 craters that formed during a roughly 40-million-year period of intense meteorite impact known as the Ordovician impact spike. Previously, experts suggested that this high-bombardment period was caused by debris from the breakup of a large asteroid between Mars and Jupiter, per Newsweek’s Jess Thomson.

But Tomkins and his team used models of Earth’s tectonic plate movement to figure out where the craters would have been at the time of impact 466 million years ago, and they revealed an intriguing correlation. All the meteorites from this period crashed to Earth close to the equator, despite the fact that 70 percent of land suitable for preserving craters was actually at higher latitudes. Previous theories couldn’t explain this placement, per Newsweek.

“The chances of this happening are like tossing a three-sided coin (if such a thing existed) and getting tails 21 times,” according to a statement from Monash University. Normally, asteroids and meteors strike Earth in a more random distribution.

Cue the ring theory. The team suggests that half a billion years ago, a large asteroid zoomed so close to Earth that our planet’s gravitational force overcame the asteroid’s own gravity and essentially tore it apart. The distance at which this happens is called the Roche limit, and it varies depending on the celestial bodies involved in the close encounter. With time, the disintegrated asteroid pieces would have assembled into a ring shape around our planet’s equator.

Then, “over millions of years, material from this ring gradually fell to Earth, creating the spike in meteorite impacts observed in the geological record,” Tomkins says in the statement.

“So, if Earth destroyed and captured a passing asteroid around 466 million years ago, it would explain the anomalous locations of the impact craters, the meteorite debris in sedimentary rocks, craters and tsunamis, and the meteorites’ relatively brief exposure to space radiation,” he adds in the Conversation.

The presence of a ring would have also shielded part of the Earth from the sun—in turn lowering surface temperatures dramatically—which could explain the timing of the Hirnantian Ice Age. However, it also could have reflected some light toward the hemisphere experiencing summer, so researchers are hoping to gather more data on how rings affect climate.

Birger Schmitz, a geologist at Lund University in Sweden who was not involved in the study, tells New Scientist’s James Woodford that the research presents a “new and creative idea,” but he adds that “the data are not yet sufficient to say that the Earth indeed had rings.”

One discrepancy, for example, is that the craters have been mostly dated to two distinct eras, instead of originating at the same time, per Gizmodo’s Adam Kovac. The scientists say this might be because a mini-moon formed from the asteroid debris, then fell apart and dropped to Earth later on.

Their next step, however, will be to mathematically model the breakup and dispersion of asteroids in general, as well as how the resulting rings develop, in hopes of understanding how such a structure might cause global cooling.

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.