Titan is cold, so cold that bottled BBQ gas (methane & ethane) are liquid in lakes around its poles and it rains (pours really) the stuff periodically in regions closer to the equator.
Methane-Ethane lakes on Titan (Credit: Copyright 2008 Karl Kofoed)
But chemical disequilibrium, as found on Titan, is one pre-requisite for interesting long-chain chemistry (i.e. LIFE) and so there’s renewed speculation about the possibility… Life on Titan: stand well back and hold your nose! Titanian Life, so the breathless copy tells us, would stink at our ambient temperature, then burst into flames and/or choke us to death.
The idea gains new credence with the discovery of abundant microbial life in the nearest terrestrial analogue to Titan – Trinidad & Tobago’s Pitch Lake – which, while it’s a lot hotter and full of much longer chain hydrocarbons, is pretty impressively nasty. Could Life survive on a moon in lakes of methane/ethane? Could it evolve there? Isaac Asimov was a biochemistry professor in parallel with his most famous authoring period and he has some very interesting speculations on this very question in a web-reprint of his 1962 essay As We Don’t Know It. Here’s a quick summary of possible biochemistries…
There, then, is my list of life chemistries, spanning the temperature range from near red heat down to near absolute zero:
1. fluorosilicone in fluorosilicone
2. fluorocarbon in sulfur
3.*nucleic acid/protein (O) in water
4. nucleic acid/protein (N) in ammonia
5. lipid in methane
6. lipid in hydrogen
Of this half dozen, the third only is life-as-we-know-it. Lest you miss it, I’ve marked it with an asterisk.
…since then we’ve learnt a bit more about the flexible limits of life-as-we-know-it, but lipids in methane/ethane are still more likely than water-based microbes struggling in cryogenic conditions. Yet everything we’ve learnt in the nearly 50 years since his essay tells us “expect surprises”. As much as we think we know our familiar brand of life here on Earth, there’s always something new discovered when we go look.