Geothermal civilization on Enceladus

We could put a civilization under the Enceladus ice.

http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2026

It would not need nuclear fuel to run.

All you need to run a powerplant is two heat reservoirs at different temperatures call them HI and LO

and the efficiency of the powerplant is limited by the ratio

(HI - LO)/HI

In the diagram you see heat reservoirs of liquid water at 273 K and ice at 77K

think about the theoretical efficiency at which those two reservoirs could be used

(273 - 77)/273

it is a high efficiency, like 70 percent

the diagram of Enceladus subsurface also shows hot rock at temperature greater than 273 K.

A civilization module designed for that environment might be something like a nuclear submarine but equipped to melt its way down into solid ice and eventually to utilize available energy rather than depend on nuclear refueling from home.

It would have to manufacture its own atmosphere, food, and replacement parts.

Technically very challenging, but perhaps worth discussing here---if anyone at SFN wishes to