This graphic shows the ring moons inspected by NASA’s Cassini spacecraft in super-close flybys. The rings and moons depicted are not to scale. NASA-JPL/Caltech
The Cassini probe finally said goodbye in 2017, when it ran out of fuel and plunged into Saturn’s atmosphere. But data from the probe continues to be analyzed, and new findings about Saturn are still emerging. Recently, research has focused on Saturn’s rings, with scientists discovering that they were formed in the relatively recent past.
Now a new study has investigated some of Saturn’s tiny far-flung moons and the way that they interact with the rings. Five moons — Daphnis, Pan, Atlas, Epimetheus, and Pandora — are nestled snugly at the edge of the rings, and data collected from a close fly-by of Cassini shows they are covered in dust and ice from the rings.
The surface of these moons is highly porous, which supports the theory that they were formed from the gradual accumulation of material that was layered on top of a dense core. Due to the porousness of the moons, they are not spherical — instead, NASA describes them as “blobby and ravioli-like” with more material accumulated around their equators than at their poles.
“We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators,” Bonnie Buratti of NASA’s Jet Propulsion Laboratory in Pasadena, California and leader of the research team, said in a statement. “A denser body would be more ball-shaped because gravity would pull the material in.”
The finding also opens up the intriguing possibility of similar activity in Saturn’s other moons. “Perhaps this process is going on throughout the rings, and the largest ring particles are also accreting ring material around them,” Linda Spilker, a Cassini Project Scientist also at JPL, said in the same statement. “Detailed views of these tiny ring moons may tell us more about the behavior of the ring particles themselves.”
“The daring, close flybys of these odd little moons let us peer into how they interact with Saturn’s rings,” Buratti said. “We’re seeing more evidence of how extremely active and dynamic the Saturn ring and moon system is.”
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