The closest-ever flybys by NASA’s Cassini spacecraft revealed that the surfaces of these tiny moons are covered with material from the planet’s rings – and from icy particles blasting out of Saturn’s larger moon Enceladus.
‘The daring, close flybys of these odd little moons let us peer into how they interact with Saturn’s rings, ‘ said Bonnie Burratti of NASA’s Jet Propulsion Laboratory. Buratti and a team of 35 co-authors have released their findings in Science.
The new study on the collection of mini-moons also targets on a long-held theory which suggests Saturn’s rings and moons may all have come from the same celestial body, which may have collided with another body and then shattered into the pieces which later formed rings.
We have known about Saturn since ancient times, of course, but we’ve only really known about the inner moons – known as Pan, Daphnis, Atlas, Pandora, and Epimetheus – pretty recently. Pan, for example, was discovered in 1985, while Daphnis only dates back to 2005. The analysis involved several instruments onboard Cassini.
Graphic shows the ring moons inspected by NASA’s Cassini spacecraft in super-close flybys.
The team used data from Cassini’s Visible and Infrared Mapping Spectrometer (VIMS) to create a spectral map of Pan, and refine our understanding of the five moons’ composition.
While Saturn has more than 60 confirmed moons, the planet’s main ring system is associated with a unique set of small moons that are either embedded within it or interact with the rings to alter their shape and composition. Researchers think these moons may have formed in stages, as ring materials fell onto dense cores that might have originally been part of a larger object destroyed during an impact.
This discovery seemed to point to two competing factors when it comes to the ring moons’ appearance. These flybys were part of Cassini’s “Grand Finale”, during which the spacecraft plunged between Saturn and its ring system before being diving into the planet’s atmosphere in order to prevent any possible contamination of larger moons that could host microbial life with microbes from the spacecraft.
Their porousness contributes to their shape as well as their makeup.
Due to the porous nature of these small moons, scientists say they’re scooping up the excess material and wearing it like a skirt around their equators – finally explaining why many of them look like ravioli. “A denser body would be more ball-shaped because gravity would pull the material in”, Buratti explained.
The process could be replicated throughout Saturn’s rings, scientists say.
“Perhaps this process is going on throughout the rings, and the largest ring particles are also accreting ring material around them”.
Daphnis and Pan, the two that sit closest to Saturn, have seen the most influence from its ring materials. Meanwhile, the moons located further away from the rings receive a greater amount of ice particles or water vapor from volcanic plumes from Enceladus.
The lunar origin stories might be replicated throughout the solar system, scientists say.
‘Do any of the moons of the ice giant planets Uranus and Neptune interact with their thinner rings to form features similar to those on Saturn’s ring moons, ‘ Buratti said.
While Cassini’s instruments gathered data on magnetic fields, dust, and plasma in the region between the rings and Saturn, scientists remain uncertain as to what may have initially started these tiny moons’ formation processes though they plan on inputting the new data into computer models in an attempt to answer this question.
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