Okay, here& #39;s what I told folks who asked about the detection of phosphine (PH3) in the atmosphere of Venus: If you give me the options of unknown chemistry, unknown geology, or unknown biology, then biology is always going to be a distant third behind the other two options.

We see phosphine in other places in the solar system, and it& #39;s not biological. Now, terrestrial planets are not the same as gas giants, for sure! But I think we& #39;re a ways away from ruling out chemistry and geology as sources of phosphine.

And honestly, with an extraordinary claim like extraterrestrial life, you do have to 100% rule out every other possible origin.

Here& #39;s the terribly poorly-kept-secret article! https://twitter.com/NatureAstronomy/status/1305522642590588934?s=20">https://twitter.com/NatureAst...

Oh and here is a good thread by @PlanetDr (whose job it is to actually measure chemical reactions and compositions under planetary atmosphere conditions) with some more context for why it& #39;s hard to know all the ways phosphine might come to be: https://twitter.com/PlanetDr/status/1305479161218293760?s=20">https://twitter.com/PlanetDr/...

I do want to say, having read the paper, I believe the authors did as thorough a job as they were able analysing the data and discussing the possibilities.

Here& #39;s the final paragraph of the discussion, since the paper is still inexplicably paywalled.

Ah, @ProfAbelMendez has found the paper available online via @ESO& #39;s website:

https://www.eso.org/public/archives/releases/sciencepapers/eso2015/eso2015a.pdf">https://www.eso.org/public/ar...