Saturn's rings are older than we thought, study suggests

A new study suggests that Saturn's rings may be as old as the planet itself, challenging previous estimates about their age. The research, led by scientists from the Japan Aerospace Exploration Agency (JAXA), the University of Tokyo, and the French National Centre for Scientific Research (CNRS), was published in the journal Nature Geoscience.

The age of Saturn's rings has long been controversial, with some researchers believing they formed along with Saturn about 4.5 billion years ago and others suggesting they are very young, possibly originating from a torn-apart comet or icy moon. The Cassini spacecraft, which arrived at Saturn in 2004, provided comprehensive data confirming that Saturn's rings are relatively bright and clean, leading to the conclusion that they formed long after Saturn itself.

However, planetary scientist Ryuki Hyodo at the Institute of Science Tokyo and lead author of the study, proposes a different perspective. "The idea that Saturn's rings are young seemed very strange in the context of the solar system's long evolutionary history," Hyodo is cited by Space.com. He explained that when Saturn formed about 4.5 billion years ago, or during the Late Heavy Bombardment about 4 billion years ago, "the solar system was far more chaotic."

Through computer modeling, Hyodo and his colleagues simulated collisions between micrometeoroids and the icy particles of the rings. These impacts typically occur at speeds of about 67,100 mph (108,000 km/h). The simulations revealed that these charged particles collide with Saturn, are dragged into its atmosphere, or escape completely from the planet's gravitational pull. As a result, very little of this material is deposited in the rings, which remain in relatively clean conditions.

"A clean appearance does not necessarily mean the rings are young," Hyodo stated, emphasizing that the cleanliness of Saturn's rings is a result of micrometeoroid impacts vaporizing on collision. The study explains that high-speed impacts can cause the vaporization of micrometeoroids, creating a high-temperature, high-pressure state. The vapor expands, cools, and condenses in Saturn's magnetic field to form charged nanoparticles and ions, which are either drawn into Saturn or into its atmosphere.

Based on the low rate of darkening that Saturn's rings experience from micrometeoroid impacts, as well as the level of contamination seen in the rings, the researchers suggest the rings may be ancient. "All together, I say that Saturn's rings are likely to be very old—about 4.5 billion to 4 billion years old," Hyodo stated. This means that Saturn's rings could actually be billions of years old and maintain a "more youthful" appearance due to their low level of contamination.

This finding challenges the prevailing "baby rings" theory, which suggested that Saturn's rings are relatively young, perhaps no more than 400 million years old. Not all scientists agree with this conclusion. Sascha Kempf from the University of Colorado Boulder led a study attempting to age Saturn's rings, explaining in a statement last year that "It's almost impossible to end up with something so clean."

"Think about the rings like the carpet in your house. If you have a clean carpet laid out, you just have to wait. Dust will settle on your carpet. The same is true for the rings," she said.

Hyodo acknowledged that the new study does not disprove the Cassini results. "Instead, we have shown that our interpretation of the Cassini data may be wrong," he said. The scientific team believes that these low levels of contamination could have misled astronomers for decades.

Planetologists speculate that Saturn's rings could come from fragments of comets, asteroids, or even from ancient moons of Saturn. "As a planetary scientist who studies the formation of the solar system, our result feels more natural," Hyodo added.

Further study, including laboratory experiments simulating micrometeoroid impacts on icy particles, is needed to determine the true age of Saturn's rings. Hyodo's colleagues are conducting such experiments in hopes of supporting these results. He emphasized that "such a mission would allow us to approach the rings at a much closer distance than Cassini did, enabling us to observe impact events directly or collect indirect evidence that could shed more light on the rings' age."

"To settle the issue, it would be ideal to collect samples from the rings and analyze their properties," suggested Gustavo Madeira, a postdoctoral researcher at the Institute of Physics of the Globe of Paris and co-author of the study.

The study also opens up new possibilities for understanding planetary ring systems elsewhere in the solar system. The team suggests: "High-velocity impacts leading to the creation of charged nanoparticles and ions could potentially occur in places such as the Uranian and Neptunian rings and icy moons around giant planets."

Saturn, the gas giant of the solar system, was born along with the other planets more than 4 billion years ago. Today, it is known that Saturn has seven rings composed mainly of water ice and to a lesser extent of minerals, extending more than 100,000 kilometers from the planet. For over 400 years, Saturn's rings have fascinated astronomers, with their detection dating back to the 17th century when the Dutch astronomer Christiaan Huygens observed them after Galileo.

Hyodo emphasized that the cleanliness of Saturn's rings is not a sign of youth but a result of the processes he and his team have modeled. "They assumed 10 percent efficiency, we reported 1 percent. You see from the equation that it becomes 1000 million years, or a billion years," he is cited in New Scientist, arguing that the lower pollution efficiency should dramatically change the age estimates.

IFLScience, Le Temps Science, Newsweek, and The Independent reported on the research, among other websites.

This article was written in collaboration with generative AI company Alchemiq