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Fraser
2008-Mar-07, 03:20 PM
Saturn is known for the spectacular rings that circle the planet, and the Cassini spacecraft has been exploring Saturnís rings, as well as its moons since 2004. And now Cassini has found evidence that there may be rings around one of Saturnís moons, too: Rhea, the second largest moon in Saturnís system. [...]

More... (http://www.universetoday.com/2008/03/07/rings-detected-around-saturns-moon-rhea/)

dhd40
2008-Mar-07, 03:26 PM
Saturn is known for the spectacular rings that circle the planet, and the Cassini spacecraft has been exploring Saturnís rings, as well as its moons since 2004. And now Cassini has found evidence that there may be rings around one of Saturnís moons, too: Rhea, the second largest moon in Saturnís system. [...]

More... (http://www.universetoday.com/2008/03/07/rings-detected-around-saturns-moon-rhea/)

I have "learned" that moons canīt have moons. At least not for a longer period. Now itīs said that even boulders might circle Rhea. :o

V_Zhd
2008-Mar-08, 12:51 AM
It makes sense... I wouldn't be surprised if more moons are found to have rings. Most ring systems would be sparse so it will take time to detect them. If the current theories of how they're created (collisions) are correct, then ring systems probably come and go several times over a moon's history.

Abbadon_2008
2008-Mar-08, 06:58 PM
Moons with lots of volcanic activity are more likely to have rings or satellites aorund them, IMO. Seems like volcanic spewage could encircle the moon, and perhaps even coalesce into (temporary) satellites. Also, if such material was dense enough, and in high enough orbit, it could slow down passing bodies and increase their likelihood of settling into (temporary) orbit around a moon.

Noclevername
2008-Mar-08, 08:29 PM
Moons with lots of volcanic activity are more likely to have rings or satellites aorund them, IMO. Seems like volcanic spewage could encircle the moon, and perhaps even coalesce into (temporary) satellites. Also, if such material was dense enough, and in high enough orbit, it could slow down passing bodies and increase their likelihood of settling into (temporary) orbit around a moon.

Rhea isn't volcanic, and there's been no signs of rings around those moons known to be volcanic (Io, Enceladus).

Jerry
2008-Mar-09, 06:00 PM
Rhea isn't known to be volcanic.

Noclevername
2008-Mar-09, 09:13 PM
Rhea isn't known to be volcanic.

Per Wikipedia:
Earlier it was assumed that Rhea had a rocky core in the center.[7] However measurements during a close Cassini flyby (see below) enabled to determine the moment of inertia which is 0.3911 Ī 0.0045 i.e. only slightly less then 0.4.[8][9] Such a value indicates that Rhea has almost homogeneous interior (with some compression of ice in the center) while the existence of a rocky core would imply the moment of inertia about 0.34.[7] The triaxial shape of Rhea is also consistent with a homogeneous body in hydrostatic equilibrium

If you can make a volcano out of that, you're a better man than I am, Gunga Din. ;)

parallaxicality
2008-Mar-10, 10:34 PM
Cool! A Lunar System!