I tried to limit the size of this post (HA!) – but there were some great excerpts from the following article. Enjoy!
“The theory that explained how Saturn’s rings could persist through 4.6 billion years of solar system evolution also explained why Saturn was the only planet that could have a ring. Then those theories had to be revised to account for the rings of Uranus. The revisions implied that Jupiter would not have a ring. Now Jupiter has been found to have a ring and we have to invent a theory to explain it.’
The older ‘unworkable’ theory was the orbital resonance hypothesis. 52 When Saturn was the only known ringed planet, orbital resonances, due to moons of Saturn gravitationally acting on ring particles, could account for the limited ring structure visible from Earth. The resonance hypothesis ‘had been worked out with fewer than a half-dozen rings [of Saturn] known. The ring structure the Voyagers discovered is too complex to … explain thousands of rings.’ 53 ‘A thousand rings seemed a monumental problem for theorists. They had run out of resonances long ago.’ 54 , 55 NASA’s conclusion: ‘No theory has yet been developed that explains how all three of these planets could have rings for so long’, i.e. 4.6 billion years. 51
The ‘shepherd moon hypothesis’ was subsequently proposed to give planetary rings a long lifetime. As originally conceived, shepherd moons were supposed to corral ring particles, keeping entire ring systems together over eons. 56 , 57 The shepherd moon theory was, therefore, once used to account for all ring structures of Saturn, Jupiter, and Uranus. 22, 58 , 59
After the Voyager 2 flyby of Uranus’ rings in 1986, NASA scientist Bradford Smith stated, ‘We are assuming [the existence of shepherds], because we don’t know any other way to do it [i.e. preserve the rings].’ 60 Since then, conventional opinion on the antiquity of planetary rings has changed due to difficulties in the shepherd moon theory. Rings are no longer viewed as debris from the solar nebula with an age of billions of years. 61 , 62 Instead the rings have formed by the fracturing of one or more moons, and therefore must have formed ‘recently’. 63 ‘Recently’, however, is a relative term, and may signify millions of years. 19, 64
Nevertheless, shepherd moons continue to be presented as the reason planetary rings exist.65 Though ring decay occurs, it is still not acceptable to allow this fact to imply a young solar system, and shepherds are invoked to extend a ring’s chronology. Therefore, rings must be simultaneously decaying, yet confined by shepherds:
‘[Planetary rings] tend to spread … Sometimes planetary rings are kept in place by the gravitational force of shepherd moons. Saturn has a very intricate ring system with lots of moons helping to keep its rings together.’ 66
This is false—‘lots’ of shepherds have not been found. Another false claim is that the ‘“shepherding” effect has been found to confine a number of rings in the solar system’. 67 Out of hundreds of thousands of ringlets in planetary ring systems, only a few have been found with nearby moonlets interpreted as shepherds.”
Read more here: https://creation.com/the-age-and-fate-of-saturns-rings
