Saturn’s Moons Helped Shape Planet’s Iconic Rings

The image of Saturn, encircled by its retinue of rings, was taken with the Cassini spacecraft wide-angle camera on May 4, 2014, using a spectral filter, which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. (NASA/JPL-Caltech/Space Science Institute)

(CN) – The dazzling, icy rings around Saturn – the second largest planet in the Milky Way – were shaped by the gravitational pull of the gas giant’s small moons, astronomers said Thursday, who also discovered the rings are much younger than previously believed.

After setting out to explore the sixth planet from the Sun in 1997, NASA’s Cassini spacecraft sent back more than 450,000 stunning images of Saturn, its rings and its moons, including evidence of oceans on Enceladus and Titan.

Cassini’s last, grand feat was to provide insight on how the planet’s famous rings were formed – a phenomenon whose explanation is one that has evaded astronomers and planetary scientists for centuries.

On its final flyby of Saturn’s rings in 2017, Cassini captured optical remote-sensing data and images of the vast equatorial field of icy particles that form the planet’s main rings.

In an analysis of the data, published Thursday in Science magazine, researchers Matthew Tiscareno of the Carl Sagan Center and colleagues found that the rings’ structures are shaped by the gravitational interactions they have with Saturn’s small moons orbiting close to or within the rings.

“Each ring particle follows its own orbit around the planet,” the study said. “However, collective effects, including collisions and mutual self-gravity, affect the structure of the rings, as do interactions with larger orbiting objects.”

Researchers – using spectroscopic analyses to identify differences in ring composition and the particles – found that “embedded masses” are largely shaping the rings.

Small moons larger than the embedded masses of particles in the rings were dubbed ”propellers” by researchers because of the gravity-like disturbances in the ring system.

In a review of the study published Thursday, Shigeru Ida of the Tokyo Institute of Technology concludes that Saturn’s rings are much younger than the gas giant itself and may hold critical clues on the origin of the rings and moons.

An analysis of planetary dust contained in the rings, and the light reflected by it, found that the rings were not as old as dust in other nearby objects – which are as old as 4.5 billion years – and could be as young as 10 to 100 million years old.

“A clear answer to the long-standing question of when and how Saturn’s rings formed has not yet been obtained, but the Cassini data provide important pieces of the puzzle,” Ida wrote in the review.

Cassini – the only earthly craft to ever orbit Saturn – disintegrated in the skies above Saturn in September 2017 after its fuel tanks were depleted, ending a remarkable 20-year journey that stretched across billions of miles of our solar system.

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