Interesting. Is what Greg Cochran said here and below reasonable?
"A lot of ice moons seem to have interior oceans, warmed by tidal flexing and possibly radioactivity. But they’re lousy candidates for life, because you need free energy; and there’s very little in the interior oceans of such system."
A primary candidate for free energy in icy moons is thermal venting at the bottom of the liquid oceans; they do have rocky cores, after all. If Jupiter's tidal forces can cause the volcanism on Io, then it's reasonable to assume that they can also cause the rocky interior of Europa to produce volcanoes that vent heat and interesting ions in to the liquid water.
There's also a surprising amount of electrolysis going on in the ice of Europa, because Jupiter has such a terrifying electrical field. I doubt that's enough to sustain an ecosystem, but it's enoug...
This is the first in a series of posts I am putting together on a personal blog I just started two days ago as a collection of my musings on astrobiology ("The Great A'Tuin" - sorry, I couldn't help it), and will be reposting here. Much has been written here about the Fermi paradox and the 'great filter'. It seems to me that going back to a somewhat more basic level of astronomy and astrobiology is extremely informative to these questions, and so this is what I will be doing. The bloggery is intended for a slightly more general audience than this site (hence much of the content of the introduction) but I think it will be of interest. Many of the points I will be making are ones I have touched on in previous comments here, but hope to explore in more detail.
This post references my first two posts - an introduction, and a discussion of our apparent position in space and time in the universe. The blog posts may be found at:
http://thegreatatuin.blogspot.com/2015/07/whats-all-this-about.html
http://thegreatatuin.blogspot.com/2015/07/space-and-time.htm