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.)
Wait, why does this strike you as a reasonable article? To me it seems like blatant pandering to the audience.
Sure, lay people want there to be life out there in other places. But this inference doesn't actually hold any water as far as I can see. In the Bayesian formalism, the question to ask is: why do you have such a high prior probability to there being life on titan that mere methane emissions are enough to make that the maximum-a-posteriori hypothesis? Isn't it more plausible that there is some other non-life chemical process generating methane? Sure, the article gives a token acknowledgment that "the authors of the latter paper provide a variety of ways to account for the acetylene shortage that don't involve an organism"... but the title of the article is pretty clearly engineered to pander to the prejudices of a scientifically clueless audience.
Indeed. Either there is a relatively simple unknown process going on in the atmosphere of a planet we've never actually been to and have only the slimmest actual knowledge, or there's a fantastically complicated unknown process called "life". For better or for worse, the odds favor the relatively simple unknown process, until more data comes in.
(I say "relatively" because it probably isn't trivial or we'd have a good guess at it. But there's still quite a gulf between "we don't know what it is yet" and "it could only be life".)
The conservationist in me always cringes whenever I hear of hydrogen or helium gases escaping gravitational pull, because I know it's never coming back. I always have to remind myself that the planets are ultimately doomed anyway, and that there's a ton more gas than I can imagine, so supply is not yet in danger of exhaustion. (that I apply these concerns to another planet I'll probably never even get near, I have decided to simply take in stride)
Nonetheless, cool article. It's interesting how many theories are coming about anymore involving life on satellites rather than planets. I understand they are probably more common than small rocky planets what with the abundance of gas giants, but are they more or less suited to life? It seems like the presence of a massive body nearby (the planet it's orbiting) would have a big impact. Plus, the distance from the sun would increase and decrease (meaning light and temperature variations), and overall incumbent light would be minimal.
By the time hydrogen supply becomes a problem, though, we'll either be long gone, or able to harness it elsewhere. Probably true for other hypothetical civilizations. Hydrogen is, after all, ridiculously abundant - and, if nothing else, weighed down by other elements.
I think we're likely to discover, as our sensing and exploration improve, that rather than being rare, life -- at least simple life -- is common throughout the universe.
(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.)