Maybe this is just a me thing but I do really find Ryland Graces theory about there being non-water based lifeforms to be like, very intriguing. I'm not sure if its something that's disagreed upon a lot in the science world because I'm not overly a science guy in terms of education or involvement, but it is something I have thought about a lot even before watching/reading PHM,, I understand that we see it (water) as such a vital thing that it's impossible to live without it but also, for a long time we (as a society) assumed there was a lot of things that didn't exist simply because we hadn't seen proof / evidence of it existing - does that make sense?
I get the impression that astrobiology has several different angles depending on what someone's core discipline is. Grace is a microbiologist, and I'm trained as a planetary astronomer, so my POV is perhaps a bit different. I never worked in that area, but I did teach a 101-level class on the subject, and one of the key ideas I wanted my students to take away was that the field was the study of conditions that might lead to life off of Earth, and that it was possible to make this a focus without ever finding alien life. (Also, that alien life would probably be microbal, based on the pattern on Earth.) From a Solar System astronomy, there is a LOT of focus on liquid water because of life on Earth. Hence you see a lot of talk about Mars, which has geology that shows past surface water (and arguments about the conditions of past Mars, and at what points the water was stable for long periods versus transitory). Many of the moons of the outer Solar System have liquid water layers below icy crusts -- this would be water-based life outside the Goldilocks zone. Enceladus (a moon of Saturn) and Europa (a moon of Jupiter) get the most attention, because those are the two worlds where the icy crust is thin enough that we might actually be able to sample ocean water. Enceladus has plumes of water vapor and ice crystals coming out of its south pole, Europa has cracks and we've seen occasional plumes of water vapor coming out of it.
But in the 'surface liquid' category, the exciting thing is Titan, another moon. Titan is the only other place in the Solar System with surface liquid -- it has polar lakes and seas of a mix of methane and ethane. And we know Titan has complex chemistry going on in its atmosphere, powered by UV light from the Sun, and Titan's atmosphere is interesting because we don't know why it still has liquid methane -- the sunlight slowly turns that into more complex organic molecules, and astronomers get suspicious of any time something should be slowly going away and we seem to catch the last gasp (Titan's atmosphere is about 5% methane and 95% nitrogen, with a pressure of about 1.5 Earth's).
So the planetary scientists are excited because this is a world that has rain and a 'water cycle' and weather and seasons and climate in ways that Mars doesn't. (Mars does have seasons climate cycles, but they come down to water and dry ice forming frost and sublimating near the poles.)
And, naturally, people are thinking about life but most planetary scientists would consider that 'bar talk' or 'I published a very speculative paper on the arXiv, but I don't think I can submit it anywhere'. (arXiv.org is a server for scientists to submit paper drafts that can be publicly be read; it started as a physics server, so less read by other fields.) The work would be on chemistry under Titan conditions, with a note that the Dragonfly mission that is being planned would be able to test some ideas. A PhD student doing a wildly speculative dissertation might be worrying to an advisor because 'how would you test things', unless there were a lot of cryogenic chemistry experiments to look at 'pre-biotic' chemistry, and notes about what the Dragonfly engineers should be planning on. The folks who do extrasolar planetary astronomy are also going to focus on 'what we can detect'. Again, that's a bias towards water as we know water-based life can exist, but Earth is also the only example of life that has altered atmospheric chemistry to a point where we can detect it, and close-in extrasolar planets are often the easiest to detect and get atmospheric data. It would be a lot easier to confirm life on Earth than Titan from Tau Ceti.
To use an example of a fringe topic, I knew a grad student who had an interest in SETI (the Search for Extraterrestrial Life). Her dissertation was on detecting 'fast radio transients' -- radio signals that suddenly appeared and then vanished. These can be natural or artificial (though so far all artificial signals have been human-made, like airport radar and people using the breakroom microwave improperly). Even if it was impossible to detect alien signals with current technology, her dissertation was useful work on weird radio signals.
Jason Wright, who I knew when he was a postdoc has made an element of his career looking at life in the universe, but he started as a standard astronomer with an interest in extrasolar planets, before looking at weird things like 'this is a very weird star; it's probably not aliens, but how would we know if it was aliens'. As a professor, he has a lot of publications on SETI and 'technosignatures', but still does normal work on transit astronomy. One of the ways we currently detect extrasolar planets is by looking for when they cross in front of their stars, having the star dim briefly once an orbit.
I don't know what astrobiology looks like from the biology end, but I suspect many of Grace's problems might have been how he conducted himself. Speculating is fine, but you need to turn that into testable predictions to show you can do science as a PhD student, get funding as a postdoc, and bring in students as a professor. I don't know what a microbiologist could have produced in terms of scientific publications without basically switching fields to chemistry; so if he's still talking to microbiologists rather than other areas of science, it could be a case of 'wrong audience, going to get missed by the people who can talk coherently about things'.
(It's also the fact that if Grace pointed out that astronomers focused too much on water and the Goldilocks zone, it might have gotten the 'sit down and listen to more than the popular science summaries of our work, and what we say to get funding' reaction, which happens a bit in cross-disciplinary fields. Mostly it comes down to 'we're searching here first, because it's the easiest to justify and know what to look for, not because we think elsewhere is impossible')
