>Given that Venus' atmosphere is a complex mixture held at very high temperature and pressure, the "sign" seems pretty weak here.
The phosphine signal is coming from a portion of Venus' atmosphere that has pressure and temperatures similar to that of the the Earth's surface, according the the Earth and Sky article.
Not really. Phosphine is broken down by UV light so having it be concentrated higher in the atmosphere, where it's exposed to more UV light, would be difficult to explain via transport from a lower altitude source.
This is a possibility but we’ll have to see what the paper makes of this, if anything. It may depend on knowing more about the motion of the atmosphere. It was also an unexpectedly large amount of phosphine apparently, more than would normally be stable at that altitude (so it’s definitely being renewed).
But again, this is just a string of tweets—hard to say anything without the paper!
The phosphine signal is coming from a portion of Venus' atmosphere that has pressure and temperatures similar to that of the the Earth's surface, according the the Earth and Sky article.