Does the Earth harbour forms of life unrelated to the carbon-based DNA-powered stuff we know about? “Impossible,” you might say, but as pointed out by astrophysicist Paul Davies, we wouldn’t know – because we’ve never looked for it.
“Our search for life [has been] based on our assumptions of life as we know it. Weird life and normal life could be intermingled, and filtering out the things we understand about life as we know it from the things we don’t understand is tricky.”
The tools and experiments researchers use to look for new forms of life – such as those on missions to Mars – would not detect biochemistries different from our own, making it easy for scientists to miss alien life, even if was under their noses.
Alternative biochemistry is inherently a speculative field, which is why it has made plenty of appearances in science fiction – Rudy Rucker has dealt with similar ideas before, for example, and Futurismic columnist Mac Tonnies has theorised about the potential of Earth being home to beings we are not able to recognise as such.
Finding examples of alien life here on Earth might add credence to theories like panspermia – but, more importantly, it would suggest that the likelihood of life developing elsewhere in the universe is closer to one than to zero. [via SlashDot; image by Haeroldus Laudeus]
I thought they’d found some weird bacteria which weren’t carbon-based living by thermal vents on the ocean floor?
The thing with this sort of speculation is, it’s an unprovable hypothesis. It’s easy enough to say that some sort of alternative biochemistry is possible, because lots of things are possible. The trick is to come up with an alternative biochemistry that can be looked for — a hypothesis that can be tested and falsified. (Ideally, someone would identify an ecological niche that isn’t filled by the known forms of life and show that some other form of life fills that niche.)
To the commentor above me — those bacteria are still based on the same sort of biochemistry as the rest of the living world (same sort of central metabolic paths, same genetic code, etc.). They just don’t get their energy from the sun. They could be utterly isolated from the surface biome. That’s weird enough in its own right, and brings up the question of just how much life there is that doesn’t live on the surface and depend on the sun.