[SunkenCiv]

Twelve More Moons Around Saturn Act In Strange Ways
by Lori Stiles
2001

The 12 newfound moons are in irregular orbits that suggest they are the collisional remnants of larger parent moons, once securely captured in, but later blasted from, their saturnian orbits... The 12 new-found satellites are irregular -- meaning they orbit outside the plane of Saturn's equator -- and it appears that their orbits cluster in three, possibly four, distinct groups, said Carl W. Hergenrother of the UA Lunar and Planetary Laboratory (LPL)... Astronomers in 1997 and 1999 discovered five irregular satellites around Uranus, and in 1999-2000 discovered another 12 irregular satellites around Jupiter, previously known to have eight... The most probable theory is that each cluster is the remains of a once-intact moon smashed by a collision sometime after the planets were formed, according to their analysis... Saturn must have captured the original parent moons during planetary formation, as the objects passed through Saturn's surrounding proto-planetary gas cloud, Hergenrother said... An alternative theory is that the moons were captured when Saturn suddenly increased in mass -- in which case the moons would all be prograde, moving around the planet in the same direction as the planet moves around the sun... "But we are seeing just as many retrograde as prograde irregular moons as Saturn," Hergenrother said. Objects captured as moons would move in either prograde or retograde orbits depending on their direction as they passed through and were slowed by proto-Saturn's gas cloud.

[SunkenCiv]

Saturn's Rings: Formation
Adler Planetarium

The prevailing theory as to how Saturn's rings were formed comes from the 19th century astronomer Edouard Roche. Roche predicted that if an object such as a moon were to come too close to a large planet such as Saturn, eventually it would be torn apart by tidal forces - the uneven gravitational pull upon an object due to its size.

Under a tidal force, an object experiences a greater gravitational pull on its nearer side than its farther side. If the difference in force is great enough, this can cause a strain which literally breaks an object apart. Scientists now call this limit where an object will be torn apart by tidal forces the Roche Limit.

Saturn's rings may be young
by William R. Corliss
May-Jun 1985

When the Voyager spacecraft swept past Saturn, they radioed back photos of a complex, very dynamic system of rings -- thousands of rings. Studies of these rings have led some astronomers to wonder if they are really as old as Saturn itself. Two lines of thinking suggest a recent origin:

(1) The rings are composed of both light material (very likely water ice) and dark material (probably rocks and dust). The rocky fragments, according to the prevailing nebular theory, should have condensed early in solar-system history, and then been swept gravitationally into the planet as they were slowed by friction with the uncondensed nebular material. Yet, dark material is still in the rings. (2) The incessant bombardment of the rings by meteorites should have pulverized the rings, sending fragments and vaporized material in all directions. In just 10 million years the rings should have been largely erased. They are still there.

(Cuzzi, Jeffrey N.; "Ringed Planets: Still Mysterious -- II," Sky and Telescope, 69:19, 1985.)