Saturn’s rings are younger than previously thought – only a few hundred million years old



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Saturn’s rings are much smaller than scientists once thought, according to new research from Indiana University professor emeritus Richard Doresen — and they’re not here to stay.

For decades, there has been debate about the origin of Saturn’s icy rings. But according to two new Durisen studies, published in Icarus, the rings are no more than a few hundred million years old – much younger than the planet itself, which formed 4.5 billion years ago. In fact, Duresen said the rings may well have formed when dinosaurs were still walking the earth.

Doresen and co-author Paul Estrada, a research scientist at NASA’s Ames Research Center in Silicon Valley, California, also concluded that the rings will last for a few hundred million years at most.

“Our inescapable conclusion is that Saturn’s rings must be relatively young by astronomical standards, only a few hundred million years old,” Dorison said. “If you look at Saturn’s satellite system, there are other indications that something exciting has happened there in the past hundreds of millions of years.”

Durisen and Estrada have long argued that Saturn’s rings are relatively young, because they expected the rings to be eroded and darkened by the influx of interplanetary meteorites. However, they were only able to use it after data became available from NASA’s Cassini spacecraft’s 13-year mission — especially its 2017 grand finale, which consisted of 22 orbits passing between Saturn and its rings. theoretical models To confidently determine the age and longevity of rings by calculating how rings have changed over long periods of time.

Of particular interest to their work were Cassini’s measurements of meteorites’ flow rate, ring mass and flow rate bell material on Saturn.

Not only does meteoroid impact contaminate the rings, but it eventually causes ring material to drift inward toward the planet. Theoretical models presented by Durisen and Estrada show that the rings should be losing mass on the planet at the staggering rate of several tons per second observed by Cassini, which means the rings’ remaining lifespan is only a few hundred million years or so. .

For the first time, detailed calculations by Estrada and Durisen have combined viscous diffusion—due to interactions of ring particles—with meteor impacts in simulations designed to extend the full lifetime of a ring system like that of Saturn. They demonstrated that it is the impacts of meteorites that ultimately dictate a short lifespan compared to that of the solar system, given the meteorite flux rate measured by Cassini.

“We’ve shown that massive rings like Saturn’s don’t last very long,” Estrada said. “One could speculate that the relatively diminutive rings around the ice and other gas giants in our solar system are remnants of rings that were as massive as Saturn. Perhaps sometime in the not-too-distant future, astronomically speaking, after Saturn’s rings dangled, and they will look like the scattered rings of Uranus. “.

Durisen’s decades-long research career has centered mostly on the evolution and stability of rotating astrophysical systems of all kinds, from planets to the galaxies. For the two decades prior to his retirement in 2010, he mainly worked Protoplanetary disksThe rotating disks of gas that surround new stars from which planets can form. But his interest in Saturn’s rings began as a postdoctoral fellow at NASA Ames in the 1970s, and has continued to study them ever since.

“When studying the universe, we often think about origins — the origins of galaxies, stars, and planets,” said Duresen. “But planets are incredibly active and diverse systems where new things are happening all the time. If Saturn’s rings aren’t as old as the planet, that means something happened to create their amazing structure, and that’s very exciting to study.”

Durisen is interested in what future space missions discover about the Saturn system. Although the planet, which is made mostly of helium and hydrogen, probably cannot support life, conditions in some of its moons may have supported it in the past or even now, he said.

“If we can figure out what happened in that system a few hundred million years ago to form the rings, we may end up discovering why Saturn’s moon Enceladus spewed out plumes of water and ice in the ocean depths and even Organic materialsDorison said. We may even end up finding the building blocks for life itself on Enceladus. ”

more information:
Richard H. Durisen et al, Large mass flow rates in Saturn’s rings due to ballistic transport and mass loading, Icarus (2023). DOI: 10.1016/j.icarus.2022.115221

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