This is where it starts to get exciting. Up to this point in human history, we have had no firm evidence of life on another world even though speculation runs rife. It is always just beyond our reach to detect it, but we may soon collect enough bio-signatures to infer its existence with reasonable confidence.
this post was submitted on 08 Mar 2024
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If there was oxygen, I'd basically say its alive.
I think the methane is a better marker...AFAIK, it's almost always a byproduct of some biological process.
bruh
https://science.nasa.gov/resource/trapping-of-methane-in-enceladus-ocean
We know of abiogenic sources of methane in this solar system.
Bruh...that's why I said almost.
I also got about 1/2 way through typing almost the same response below about gases that naturally degrade quickly, not being able to accumulate to high enough concentrations to be detectable at these distances but @TropicalDingDing did so more eloquently than their name would indicate possible, so I'll let you read theirs here: https://lemmy.world/comment/8258449
It’s a good biosignature but a real smoking gun would be if a planet has intelligent life that’s not always so intelligent. Then, we might detect chlorofluorocarbons or some other synthetic pollutant.
“Well, we detected an alien civilization but their atmosphere is in way worse shape than 1950’s London and they’re 100 light years away. I guess we’ll keep checking and see if they get their act together or not.”
Plot twist, they're already dead by the time we detect them, the light from them exploding the planet just hasn't reached us yet.