I started thinking about the problem of finding places in the Solar System where humans could live. The main problems are 1) energy sources, 2) sources of water and oxygen, and 3) protection from energetic cosmic rays.
Assuming Europa does have a global subsurface ocean, wouldn't this ocean provide all of the things mentioned above?
Also, a refuge of human knowledge (and perhaps terrestrial life) deep in Europa's oceans would survive most of the disasters that could wipe out life on Earth, including close supernovae events and exposure to catastrophic cosmic / gamma ray events. It would take an *awful* lot of energy to strip the ice off of Europa's oceans, I would think.
Perhaps, in the name of the survival of humanity, you could make a case for placing a colony within Europa's oceans...?
-the other Doug