Space

Saturn's strange moons are scooping up material from the rings and growing

Saturn's strange moons are sco...
Newly-analyzed data from Cassini shows that Saturn's moons are scooping up material from the planet's rings and growing
Newly-analyzed data from Cassini shows that Saturn's moons are scooping up material from the planet's rings and growing
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Newly-analyzed data from Cassini shows that Saturn's moons are scooping up material from the planet's rings and growing
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Newly-analyzed data from Cassini shows that Saturn's moons are scooping up material from the planet's rings and growing
Images of Saturn's moons Atlas, Daphnis and Pan to scale, showing the extent of their strange bulging shapes
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Images of Saturn's moons Atlas, Daphnis and Pan to scale, showing the extent of their strange bulging shapes

Two years ago as the Cassini probe made its daring final plunge into the atmosphere of Saturn, it flew past for a closer look at a few of the gas giant's inner moons. Now a NASA team has analyzed the data and uncovered some intriguing new details about these tiny worlds, including how they're busily scooping up material from Saturn's rings and growing into weird shapes.

Between December 2016 and April 2017, Cassini used six instruments to examine the shape, structure and composition of five of Saturn's innermost moons, Pan Daphnis, Atlas, Pandora and Epimetheus. These moons all orbit within or very near to the planet's iconic rings, so it's no surprise that they interact with the dusty disks.

"The daring, close flybys of these odd little moons let us peer into how they interact with Saturn's rings," says Bonnie Buratti, lead author of the study. "We're seeing more evidence of how extremely active and dynamic the Saturn ring and moon system is."

Images of Saturn's moons Atlas, Daphnis and Pan to scale, showing the extent of their strange bulging shapes
Images of Saturn's moons Atlas, Daphnis and Pan to scale, showing the extent of their strange bulging shapes

These Saturnian moons are famous for their weird shapes, resembling flying saucers or pieces of ravioli due to their lumpy bodies and bulging middles. The new data revealed a possible explanation for how that comes to be. The team found that the moons have porous surfaces and possibly denser cores, suggesting that they're growing bigger as they gather up particles from the rings.

"We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators," says Buratti. "A denser body would be more ball-shaped because gravity would pull the material in."

Cassini's close pass of Pan, the innermost moon, revealed more clues about what these objects are made of. The spacecraft used a Visible and Infrared Mapping Spectrometer (VIMS) to make a spectral map of the moon's surface, in both visible and infrared light.

That showed that the moons closest to Saturn – Pan and Daphnis – are reddish in color, which is similar to the main rings. While the team doesn't yet know what minerals make it that color, they suspect a mix of organic compounds and iron. Meanwhile the moons outside the main rings, including Atlas, Prometheus and Pandora, look more blue, thanks to layers of icy particles and water vapor sprayed over them by Enceladus' icy plumes.

The team still isn't really sure how these moons form, but one possibility is that a larger, denser object broke apart in the distant past and the fragments swept through Saturn's rings, collecting the dust and ice and gradually building up. The team plans to model different scenarios to find the most likely answers.

The research was published in the journal Science.

Source: NASA

6 comments
Cigarshaped
The whole problem with all these NASA based discussions is a one-track mind approach. Lateral thinking seems to go out of the window where astrophysics is concerned. All effort is concentrated on forming a GRAVITY solution to the numerous queries that space throws back from their missions. Very rarely if ever does the conversation swerve to include the most prolific force in space - electromagnetism. It is dumped at the sidelines due to a number of wrong assumptions built up over the years. Yet we have vast amounts of evidence that magnetic fields and em radiation accompany every phenomenon, star, galaxy or planet. So the intent seems to be to break the simple laws of physics and say that electric current cannot possibly be the CAUSE of magnetic fields, it is a mere 'byproduct'. Instead we have sloshing lava and other mechanistic explanations to avoid saying the 'e' word. I personally had this direct from an astrophysicist "we know there are magnetic fields but we CHOOSE TO IGNORE THE ELECTRIC CURRENTS!" This is such a such a sad state of affairs, not only due to the 100 years backward progress of astronomy but also the shear waste of public funds chasing after these gravity fairy stories. So with Saturn's moons we have a perfect opportunity to discuss the electrical nature of this gas giant. You only have to look at all her weird characteristics and magnetic fields to see that her plasma sphere is a charged body, she receives more energy electrically than simple light radiation could explain. The entire ring system displays electrical stability and has very little to do with gravity. The mini moons have been electrically etched and continue to be so. Time for an alternative viewpoint to complement the traditional thinking that currently drives progress backwards!
paul314
In a future where people mine outer-solar-system bodies for organics, these moons look like they would be tempting targets. Assuming, of course, that some kind of weird low-temperature solid-phase evolution hasn't been going on, in which case we might annoy something.
F. Tuijn
It is a matter of scale. For small moons and the even smaller items in the ring gravity will be less important than even a small electric charge.
highlandboy
It would be interesting to know the rate of accumulation and by extrapolation how long it would be until a large portion of the rings are absorbed. Of course the rate will not be constant, but exponential as they accumulate more mass. Such study would also inform the development of planets from debris. It may also allow formulation of calculations to explain the diffuse nature of the asteroid belt.
ChairmanLMAO
probably really is a mix of those two ideas plus hairy aliens mining the rings for gold.
amazed W1
"Cigarshaped", a certain professor Scott would be delighted to have your support, assuming he is still alive. He published a book about 20 years ago in which he not only put forward the view that electromagnetic forces explain the "lack of gravity" but that the detectably moving plasma plumes are probably one of the sources of such forces. He also managed to model the phenomena in more or less laboratory conditions. He unfortunately pointed out that nobody has modelled a black hole and other related intellectual constructs, now shewn to be only partially supported by what can be observed in reality. His reward was to be ostracised by the astrophysics fraternity and to have his publications rubbished by so-called peer reviews, where all the reviewers were fully paid up gravity guys, anxious about their tenures. The whole affair is an eye opener, and makes people like me mistrust the attitudes of, for instance, the caucus which insists there is only one cause of global warming, ignoring the "holes" in this hypothesis, but majoring only on the holes in all the other theories. It really is time that the so-called scientific community grew up, as you say Cigarshaped, and didn't create hard edged factions which are joined by those who want to bandwagon the most successful looking theoretician. Remember the clash between wave motion and corpuscular motion theories of light? Both were found to have got some of the story. And of course Leibnitz vs Newton in calculus, where differentiation proves to be the inverse of integration but both are substantially the same thing. Question, are some intellectuals actually stupid, or are they simply locked into a framework of limited scope. Why don't they escape such frameworks? We erks need to know.