Theory: Saturn Moon's Heat From Decay

I seem to remember now Sir Arthur C. Clarke (and I think co-author of "Intelligent Life in the Universe" Carl Sagan) proposing a similar process might be occurring (and tidal gravity between them) with one of the moons of Saturn, Titan I think the largest, with a thin nitrogen atmosphere. This is interesting as these many satellites are in orbit around "gas giants" that might have become "suns" under other circumstances its theorized. A little closer satellite-moon Europa, in orbit around the fifth planet from the Sun, Jupiter, is thought to have an ocean under the thick water ice and shows what might be upwelling "water spots" I saw on line the other day. We should hope (former Planetary Society member) a combined EU USA (and others) might send a planetary explorer there, the "little closer" Jupiter. How about a solar sail? They had some problems with the Russian launch from the submarine experiment (it also accidentally deployed in the Baikonur Cosmodrome) as the delivery system had missed a prior upgrade, but they still are going to try, with Mrs. Sagan I think as its honorary president. They should be thanked for keeping the spirit of Apollo-Soyuz Test Project alive for this American. Newsvine - Theory: Saturn Moon's Heat From Decay