Evening reading sorted out. Tweets to come.

Ok, here we go. First I'll say I have a bit of experience in this kind of astronomy (mm/submm spectroscopy), and there are some i's that have to be dotted and t's that need to be crossed in doing this kind of observation, and Greaves et al. did that.

They took care of "ripple" in the JCMT spectrometers. They got a spectrum that was decent enough to go observe with higher resolution at ALMA. Because Venus was so bright, they did a few things to compensate for it, including dealing with "ripple" again.

They checked how good their phosphine observation was by also looking for deuterated water (not H2O but HDO, water with a deuterium replacing a plain old hydrogen). They expected to see it and they saw it. (Tagging in Star Trek completist @carlinspace because of deuterium.)

Just want to give myself a pat on the back for spelling deuterium right, because I always have to think which way around the u and the e are.

The JCMT and ALMA spectra were basically at the same velocity (that is, the same frequency) and the same width, and the ALMA line was a lot better looking.

They also checked if there was some other gas that just happened to be absorbing at the same frequency as the phosphine. There's a transition of SO2 right at that spot. But they didn't expect to see it because this transition happens in hotter gas than where the phosphine is.

They looked for another SO2 line that would be no problem to see if their phosphine was actually SO2, and they didn't see that line at all. So they feel pretty good that their phosphine is actually phosphine, and I would agree with them.

Lunch break over. Gonna have to note this from @cfroning, though. https://twitter.com/cfroning/status/1305922315100676101?s=20

Now into the rest of the paper, where I'm on less surer ground. So how do you get phosphine on Venus? It either comes from in the atmosphere, on the surface, underground, or from space.

They ran a reaction network and couldn't get any phosphine out of it. Lightning and meteorites also give you hardly any. So what are you left with?

"Unknown photochemistry or geochemistry, or possibly
...
...
...

life."