Ring Around Rhea? Probably Not


Back in 2005, a suite of six instruments on the Cassini spacecraft detected what was thought to be an extensive debris disk around Saturn’s moon Rhea, and while there was no visible evidence, researchers thought that perhaps there was a diffuse ring around the moon. This would have been the first ring ever found around a moon. New observations, however, have nixed the idea of a ring, but there’s still something around Rhea that is causing a strange, symmetrical structure in the charged-particle environment around Saturn’s second-largest moon.

Researchers announced their findings in 2008 that there was a sharp, symmetrical drop in electrons detected around Rhea. This moon is about 1,500 kilometers (950 miles) in diameter, and scientists began searching for what could have caused the drop. If there were a debris disk around Rhea, it would have had to measure several thousand miles from end to end, and would probably be made of particles that would range from the size of small pebbles to boulders.

Testing the hypothesis, Cassini flew by the moon several times and took 65 images between 2008 and 2009, flying at what would be edge-on to the rings, where the greatest amount of material would be within its line of sight.

Using light angles to their advantage — and if the ring was there – the scientists should have been able to detect micron-sized particles up to boulder size objects.

But they saw nothing.

“There are very strong and interesting and unexplained electromagnetic effects going on around Rhea,” said Matthew Tiscareno from Cornell University, who led the imaging campaign. “But we’re making a pretty strong case that it’s not because of solid material orbiting the moon….For the amount of dust that you need to account for [the earlier] observations, if it were there, we would have seen it.”

While the ring hypothesis has been disproved, there’s still a mystery about the cause of the symmetrical structure in the charged-particles around the moon.

But the Cassini spacecraft and team are up for the challenge.

Source: Cornell University

15 Replies to “Ring Around Rhea? Probably Not”

  1. I hope the build a University on that moon – I’d buy a “U Rhea” shirt! Maybe some day it could be bigger than Uranus jokes!

  2. The tidal accelerations exerted by Saturn on Rhea make it difficult to see how such rings could exist. If rings did exist they would have to be regularly replenished by some source.


  3. I’m really gong to ‘go out on a limb’ here, and make a prediction.

    It will eventually be found that Saturn not only makes water vapor/ice through an electrodynamic ‘cold fusion’ process, it will also be found that Saturn continuously manufactures its rings and has created many of its moons as a result of that process. ALSO, it will eventually be found that Saturn is actually a captured ‘brown dwarf’ star…

    Here comes the rebuttals….

  4. @ Aqua,

    Have you been frequenting an Amsterdam ‘coffee shop’ recently?

  5. It’s not that Aqua’s limbs are too weak or crooked; the reason no one can follow is that there _is_ no limb.

    Free fall is of course a space experience, but not so harmless when you need your feet on the ground. And be able to hear those hoof beats of horses.

    Rebuttals, what rebuttals? There is nothing sane to rebut there.

  6. Aqua. Why do you think Saturn is a captured brown dwarf? Surely you realise it’s far too small. Even Juptiter is too small. At one time some thought that the excess heat from Jupiter was evidence that some sort of ‘fusion’ was going on but later this was found to be residual heat from its ongoing gravitational contraction. While the distinction bwtween small brown dwarves and large gas planets appears to be blurring even the smallest proposed BD is still substantially larger than Jupiter and certainly far larger than Saturn.

  7. Is it possible that dark or anti matter could make up the ring? Anti matter seems a bit of a stretch but dark matter could potentially exist in this scenario.

  8. “Oxygen Atmosphere Around Saturn Rings?

    Scientists were also surprised to find that the atmosphere around Saturn’s rings is largely made up of oxygen.

    Most people thought the ring atmosphere would be water molecules—H2O—and their breakdown products H [hydrogen] and OH [hydroxyl],” Cuzzi said. That the ring system would have the chemistry to turn hydrogen and hydroxyl into oxygen “was not foreseen by most.”

    The discovery could help solve a long-standing mystery of Saturn’s rings: why some of them seem stained red.

    Perhaps the color is imparted when metals in ring rocks interact with oxygen, he said. On Earth we have a name for it: rust.”

    This is from The National Geographic Daily News, March 10, 2010: http://news.nationalgeographic.com/news/2010/03/100318-saturn-rings-unstable-scitech-oxygen-atmosphere/

    Otay…. Note that the oxygen is presumed to have been created by dissociated Hydrogen and Hydroxl and has formed an ‘atmosphere’ around the rings. The rings themselves are located at the interface of Saturn’s plasma sheet and its magnetosphere. The solar wind, carrying ionized Hydrogen is pumped into the magnetosphere at the poles… This might be the mechanism I posited that might CREATE water molecules in the ring plane.

    @Paul Eaton-Jones – You are right.. how’s “proto brown dwarf” sound? From Wikipedia – “Brown dwarfs are sub-stellar objects which are too low in mass to sustain stable hydrogen fusion. Their mass is below that necessary to maintain hydrogen-burning nuclear fusion reactions in their cores, as do stars on the main sequence, but which have fully convective surfaces and interiors, with no chemical differentiation by depth. Brown dwarfs occupy the mass range between that of large gas giant planets and the lowest mass stars; this upper limit is between 75[1] and 80 Jupiter masses (MJ). *Currently there is some debate as to what criterion to use to define the separation between a brown dwarf from a giant planet at very low brown dwarf masses (~13 MJ )*, and whether brown dwarfs are required to have experienced fusion at some point in their history. In any event, brown dwarfs heavier than 13 MJ do fuse deuterium and those above ~65 MJ also fuse lithium. Some planets are known to orbit brown dwarfs: 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144?.”

  9. @AQUA

    If you want to debate the validity of your personal theory, this isnt really the proper place to be doing it. Its *very* offtopic to this story, and TBH, a wee bit ‘out there’.

    Id recommend the BAUT forums as the place to talk about it. Its properly moderated against trolls so that you can get some coherent replies, and you get access to many experts in the field who can help you.

  10. Thanks GEKKONZ… the relationship to this topic is of course the interesting and unexplained electromagnetic effects going on around Rhea.

  11. I’m afraid “sharp symmetrical drop in electrons” doesn’t tell US, your readers, anything.
    Is a sharp drop %1000?
    Is it radially symmetric? Is it spherically symmetric?
    How much was it before?
    Do the other moons have clouds of electrons?
    All you have here is a “nobody knows nuttin’ ” story. Just vague enough to bring out fringe theorists.

Comments are closed.