One point I'd like to add is that you shouldn't get your hopes up about meeting bug-eyed aliens. Titan is cold -- so cold that even if this is a metabolic signa

One point I'd like to add is that you shouldn't get your hopes up about meeting bug-eyed aliens. Titan is cold -- so cold that even if this is a metabolic signature, whatever reactions are running are probably so slow that nothing more complex than prokaryotic bacteria has had time to evolve yet since the formation of the solar system. And even bacterial life might be a bit of a reach. (This is a guess, but based on what we know of terrestrial biochemistry. Just bear in mind that on Titan, the mean surface temperature is around -180 celsius -- methane runs like water, water ice is a rock-like substance, and so on.)