[oatman (OP)]

A recent article about SETI made me wonder why most if not all efforts to detect alien life center around the detection of radio waves/signals. Given the rarity of habitable planets with the right chemicals for life etc the chances of life being progressed enough/inclined to send signals in a format we can find/recognize seem massively small!

Is this just because there is no other way? Might it ever be feasible to detect biomass/organisms on planets via telescope in the same way we extrapolate the chemical make up of stars from their light, or any other techniques?

Would be interested to hear any thoughts!

[alancalverd]

Depends on your definition of life. We tend to think of carbon as the essence of terrestrial life, but it is actually the hydrogen bond that allows DNA to replicate, and the anomalous behaviour of water (thanks to the hydrogen bond) that maintains this planet in a quasi-equilibrium that can support life.

So the principal candidate would be a wet planet. But if the surface is completely covered with water there's no reason to expect to see much CO2 or CH4 (both associated with terrestrial life) in the atmosphere, even if the ocean is full of weed, bugs and fish.

Intelligent life, of course, wouldn't waste time watching television, so SETI is doomed.