Saturn’s famous rings younger than the dinosaurs


Computer simulations peg the birth of the gas giant's rings and moons to the Cretaceous period. Amy Middleton reports. 


A false colour, simulated image of Saturn's rings. – NASA / JPL

Saturn's iconic rings, along with some of its closest moons, may be younger than the dinosaurs, according to a new study.

A team of researchers at SETI Institute in California used computer modelling to reveal secrets about the birth of Saturn's satellites in the Astrophysical Journal.

This birthing story is the result of a study into the journeys taken by these satellites, information which can then be applied to predict their future movements and potentially draw conclusions about how they evolved.

“Moons are always changing their orbits. That’s inevitable,” explains lead author Matija Cuk.

“But that fact allows us to use computer simulations to tease out the history of Saturn’s inner moons.”

All Saturn’s moons have to share space within the planet’s surrounding atmosphere. Their orbits affect each another, and also by the tides – that is, fluid deep within the planet’s interior.

Because the moons change their orbits at different rates, they occasionally form special configurations around each other, pulling and thrusting themselves into elongated and tilted orbits, like a rubber band moving around two fingers.

By studying these patterns, the researchers were able to digitally model predicted future movements of Saturn’s moons, and also compare them with past records.

They observed a surprisingly small change in the orbital patterns of Saturn’s closest moons – Tethys, Dione and Rhea – which suggests they haven’t been circling the planet for as long as previously thought.

With some help from data collected by a NASA spacecraft on Saturn’s icy moon Enceladus, the researchers made their estimate of the age of the Saturn’s youngest moons.

“We find that they were most likely born during the most recent 2% of the planet’s history,” says Cuk.

Given that Saturn is around 4.5 billion years old, this estimate places the birth of Saturn’s closest satellites – including its bright rings – at 100 million years ago, around the time of the Cretaceous Period.

Cuk says the researchers have debated what may have caused the birth of these moons. “Our best guess is that Saturn had a similar collection of moons before, but their orbits were disturbed by a special kind of orbital resonance involving Saturn’s motion around the Sun,” Cuk explains.

“Eventually, the orbits of neighbouring moons crossed, and these objects collided. From this rubble, the present set of moons and rings formed.”

Theories about the age of Saturn’s innermost moons have been tossed around since 2012, when French astronomers noticed that Saturn’s moons grow their orbiting patterns quite quickly, hinting at a relatively young age.

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  1. http://iopscience.iop.org/article/10.3847/0004-637X/820/2/97
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