Pluto_and_Charon

Have any preliminary calculations been done to show the effect of tidal heating on these worlds? It would be a shame if it turned out they're all as volcanic as Io

Although I'm guessing the low density of these planets indicates that they are water rich = no Io-scale volcanic activity? Could my logic here be correct?

I never got why more massive rings = older and less massive rings = younger. Can anyone explain it for me? Thanks

Is the reasoning that rings loose mass over time? So a less massive ring must have formed in the recent past because it'll only last a few hundred million years before it disappears/decays? But if that's the case, why can't the less massive rings just be a very old ring that's decayed over 4 billion years and is now much smaller than it originally was? (and surely that's a far more likely scenario, given that collision rates were orders of magnitudes higher back during the late heavy bombardment then they were 100 million years ago?)

If the planets are so close to each other and are significantly influencing each other's orbits, why haven't they collided yet?

If Hubble could rule out hydrogen rich atmospheres on the inner two planets last year, could it do the same for the newly discovered, more (potentially) habitable planets?