Are rings on a planet always the same? are the rings the same age as the planet? and...

Question

Since Saturn is not the only outer planet with rings- Jupiter, Uranus, and Neptune all have ring systems... .

Do we think the ring systems surrounding these planets are as old as the planet? Why or why not?

Do we expect that inhabitants of Earth 100 million years from now will see the same ring systems around these planets as we do now? Why or why not?

Describe the processes that determine the evolution of rings around giant planets.

Answer 1

Quite obviously, the rings of a planet are not the same, as we believed until only recently that only Saturn had rings.

I'm not sure there's a consensus on the age of the planets, let alone the age of their rings.  I lean towards the idea that rings are younger than their planets, but it can be argued that rings are actually older than their planets since the rings would begin to orbit the central mass long before it had accreted enough material to become a planet.

We know that space is not truly empty, so it is easy to speculate that the sun, planets, moons, and rings will become larger as time passes.  Jupiter, however, is likely to evolve into a brown dwarf with a solar wind that will blow its rings away.  There are those who insist that Jupiter is already a radio star, which might explain why Saturn's rings are more prominent.

Answer 2

Every planet's ring system must be analyzed and studied on an individual basis.  However, it is believed by many scientists that a ring system as expansive and complex as the Saturn and Uranus rings cannot survive for more than a million years without some stabilizing agent to keep the rings intact.  Saturn has various "shepherd" moons that exert gravity on the rings and preserve them, and Uranus may have similar shepherd moons maintaining its rings, although this has not yet been confirmed.

As for the age of the rings, the Uranian rings are believed to be no more than 600 million years old, while the Saturnian rings may be as old as Saturn itself.  Both Uranus and Saturn are somewhere between 4.5 billion and 5 billion years old, so it does appear possible for a ring to form around a planet long after that planet has taken shape.