by mtlmtlmtlmtl | 2025-04-17 11:02:39+00:00
This is very exciting. It's certainly approaching the best evidence we could possibly hope for from an exoplanet given current technology.

Of course, the weak link here is the assumption that these bio-markers can't be produced abiotically, which is a pretty big assumption. Our understanding of planetary science is still in its infancy. This is (thought to be) a hycean planet, a type of planet unknown to us until very recently(post-JWST, I believe?). And given that the solar system has no hycean planets, it's a class of planets which is fundamentally poorly studied, with pretty limited access to data. We can make models, and we can get some spectral data on the contents of their gaseous atmospheres. But we have no way of looking at their surface oceans. Thinking about what kind of chemistry might be going on there is mostly just an act of speculative modelling.

So the interesting question is, without new sources of data, can we determine whether these bio-markers are biological in origin? Not really. Not without a much better understanding of planetary science in general and hycean worlds in particular(of course, that's what this research is trying to do, and making progress at). As well as a deeper understanding of abiogenesis. I could imagine a working understanding of abiogenesis at least being able to eliminate some candidate planets, but even that assumes only one type of abiogenesis is possible, which is more or less unfounded. That is, unless the understanding includes some deep information theoretic/evolutionary perspective on abiogenesis which would probably have to include a completely unambiguous information theoretic and physical definition of what life even is. It is conceivable that such an understanding might provide very strong restrictions on what kinds of chemical systems are capable of abiogenesis, and that those restrictions could then be used to eliminate certain planets or even entire star systems from contention. And if these hycean worlds were eliminated that way, we'd know there must be some abiotic source of these "biomarkers", and knowing that, we would likely be able to figure out what it is. But ok, that's a lot of assumptions.

Maybe we get lucky, and some chemists stumble on a non-biotic chemical system that can produce these chmicals in concentrations that can be detected by JWST at a distance of hundreds of light years. Or, conversely, maybe chemists somehow manage to prove conclusively that biotic origin is the only possible source. I'm not a chemist or a microbiologist, so I have no idea what that would look like. It's probably well beyond our current understanding.

I guess what I'm rantingly saying is, while this result changes my credence that there's life on this planet about as much as is possible with current science and technology, it still barely changes it at all. Before it was maybe 0.5 + ε(habitable zone, liquid water), and it is now 0.5 + 2ε.

I guess something which could move the needle much more significantly, is if we found a large number(say 10) of chemically unrelated potential bio-markers in the atmosphere of a planet very similar to earth, in a very similar star system. Then, the assumption of the impossibility of abiotic sources would be much more plausible. I believe doing this type of research for earth-sized exoplanets with JWST is still quite borderline(please correct me if I'm wrong).

Having said all that, this result is still extremely exciting. For the first time, the field of exobiology has any contact with observational data from outside our solar system at all(besides mere astronomical data), and things will only improve from here. Future telescopes will be better at this type of observation, and our understanding of planetary science is evolving at an accelerating pace. I'm very excited to see where this research goes in the future.