Exobiology isn't an area of as deep fascination to me as it is for some, but if it is for you, Derek Lowe has a thoughtful post on the subject.

[Update at 8:30 AM EST]

Here is some encouraging news for those looking for life off planet--bacteria that have survived being frozen for over thirty thousand years.

I know that you're not an advocate of "space for science's sake", and I can understand that. It's not enough of a constituency to get large (and sustainable) stuff done. Until we can get up there and live and turn a profit, we're not going to have the incentives to do the kinds of exobiological searches I spoke about.

Naturally, anything that enabled the sorts of missions in my post's wish list would also be pretty handy for a spacefaring human culture. If you can get an intact dirigible out to Neptune, you can get people to all sorts of useful places, too. And if I had the choice, would I want a Mars (or Titan!) rover, or would I prefer a 21st-century Harrison Schmidt out there with a bag of tools and a lab? No contest!

He quotes an interview of Brenner:

This makes inescapable the conclusion that if life is an intrinsic property of chemical reactivity, life should exist on Titan. Indeed, for life not to exist on Titan, we would have to argue that life is not an intrinsic property of the reactivity of carbon-containing molecules under conditions where they are stable. Rather, we would need to believe that either life is scarce in these conditions, or that there is something special, and better, about the environment that Earth presents (including its water).

The fallacy here is that he assumes presence of chemistry should be sufficient in itself. That ignores environmental conditions, that the environment on Earth was more conducive to life, namely, there's a lot more energy available to life in the form of sunlight and geothermal energy.

Second, the temperature is warmer, but not warm enough (usually) to damage complex molecules. That means chemical reactions occur faster. I forget the rule of thumb, but it's something like chemical reactions double in speed with every 10 degree Celsius rise in temperature. So while life can potentially live in regions near geothermal areas, most of Earth is livable and inhabited by a high concentration of life.

Finally, our inability to detect life outside of Earth is a strong indication that we're working on the Anthropic Principle. Namely, that life is somewhat rare and hard to find and we just got lucky. We may be the first space-faring civilization in the galaxy. The fact that we haven't found alien artifacts seems evidence that we're not say under quarantine.

Reminds me of a story of bacteria being revived from amber after 25 million years:

http://www.ambericawest.com/bacteria.html

What if the Exobiologists got together with the Italian Scientist who did the Mammorial Endowment study?

Most men would change their minds on the exixtence of extra-terrestrial life, IF they could be assured that female aliens have breasts.

I danced with just such an alien in Rachel, NV once. She actually only had one breast, in the middle of her back. Not much to look at, but she did like slow dance.

Karl, it’s not the high energy per se that makes the difference, but the fact that there’s a thermodynamic disequilibrium you can dump molecules down to drive your reactions. And geothermal vents are certainly hot enough for the purpose; IIRC, Alvin melted a thermometer or some other gadget trying to measure the temperature when black smokers were first discovered.

In the full text of the review, the authors suggest that geothermal sources are sufficient for the formation of life, and that planets ejected from a putative solar system might even carry life between the stars, surviving solely on geothermal energy. Granted, such life is more likely to be slime than Klingons, but the idea that life originated around geothermal vents is a fairly popular one in the evolutionary bio community. Capturing light certainly gives you a lot more energy to work with overall, but efficient light capture presumably had to wait for the development of chromophores and so forth.