Saturn’s rings may have formed during a surprisingly recent crash of two moons

Try to imagine Saturn without its signature rings. Now imagine two big icy moons getting closer together little by little until – boom. Chaos. What was solid is now liquid. Diamond shards scatter in the darkness. Many icy fragments tumble close to Saturn, remain there and dance in unison around the gas giant, ultimately forging the exquisite disks of the heavy body.

This spectacular scene comes from an attempt to answer one of the solar system’s greatest mysteries: where did Saturn’s rings come from and when did they form?

A study published this week in The Astrophysical Journalleans towards the idea that they are not billions of years old, but were created in the recent astronomical past – perhaps by the collision of two modest format frost-strewn moons just a few hundred million years ago.

“I’m sure it would have been amazing to see if the dinosaurs had had a good enough telescope,” he said Jacob Kegerreisa research scientist at NASA’s Ames Research Center in Mountain View, California, and one of the authors of the study.

Dr. Kegerreis and his colleagues tested the younger ring hypothesis using the UK’s Distributed Research Using Advanced Computing facility. This supercomputer system allowed the researchers to repeatedly recreate this disaster and its immediate aftermath in greater detail, discovering that this origin story is plausible.

The team’s simulations could help scientists study the formation not only of Saturn’s rings, but of all worlds. With its numerous satellites, Saturn “can be considered a mini solar system,” he says Scott Sheppard, an astronomer at the Carnegie Institution for Science in Washington, who was not involved in the new study. “Saturn is a perfect laboratory for understanding how planets and moons form.”

Saturn, 4.5 billion years old, is almost as old as the Sun. The rings were thought to be the same age until the Cassini spacecraft studied the planet up close for thirteen years. For billions of years, they should have been tainted by other dusty space debris. But the icy rings appeared too shiny and clean be ancient.

This, along with other evidence, has convinced many scientists who study Saturn that the rings appeared a few hundred million years ago. If they didn’t form during the pandemonium of the early solar system, when large objects routinely collided, that means they arose in the relatively quiet days of the recent astronomical past. But how?

Saturn now has at least 145 moons and probably possessed many before developing rings. Scientists have argued that the Sun’s immense gravity has gradually destabilized some of the moons’ orbits. culminating in a collision between two moons.

The new study found that an attack between two icy satellites would blow a lot of frozen confetti towards Saturn. If that ice were to cross and stay behind the Roche limit—a limit beyond which a planet’s gravitational tides would disintegrate moons—then it would have a chance to form those rings.

Shards that remain behind the limit may have landed on other satellites, shattering them and releasing more material — the kind that could clump together to form newborn moons.

It is not clear which of the current moons are relatively young. But Rhea, Saturn’s second-largest moon after Titan, may be an example. If it had been older, it would have endured different gravitational movements, and its orbit would have been more eccentric. But instead, Rhea is circular and flat, indicating that it was formed very recently – perhaps built from that newly released moon-making material.

Some of Saturn’s moons may have potentially habitable subsurface oceans. But if those moons are younger than thought, that possibility could be reduced.

“We still don’t know what the chances are that life will evolve there,” said Dr. Keger trip. But if some of these moons are younger than what scientists thought, “that could reduce the chances of life there.”

The long-standing debate about the origin of Saturn’s halos will not be settled by this study. But it emphasizes that the rings are ephemeral and constantly changing, rather than static decorations.

“Whether it’s Saturn or somewhere else, I like how dramatic the solar system can be,” said Dr. Keger trip.