Isn't there a theory about the material that makeup those rigs, eventually crashing into Saturn's atmoshpere or floating off?
The problem would be if the rings didn't change, but over what timescale? 25years is a fleabite in the planet's history.
Most theories of ring formation involve a moon being broken up by tidal forces. The resulting debris eventually makes its way back to the parent planet; most theories predict about a 50,000 year lifespan. In that respect, we're lucky to live at a time when Saturn is so resplendent.
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