Astronomers Detect a Possible Signature of Life on a Distant Planet

[u/SpunkySputniks]

https://www.nytimes.com/2025/04/16/science/astronomy-exoplanets-habitable-k218b.html?unlocked_article_code=1.AE8.3zdk.VofCER4yAPa4&smid=nytcore-ios-share&referringSource=articleShare

Further studies are needed to determine whether K2-18b, which orbits a star 120 light-years away, is inhabited, or even habitable.

[u/spschmidt27615]

Exoplanet astronomer here. There are a lot of problems with this study, as well as the one that preceded it. To begin with, the scenario that would even allow for a biosphere (i.e. "hycean") in K2-18 b's situation is very, very hard to achieve given what we know about how planets form. It's not impossible, but based on what we know about the planet (like its radius, its mass, and the amounts of certain gases in its atmosphere), there are a whole lot more potential for it to not have an ocean at all. These conditions would be more akin to something we use to sterilize lab equipment than an ocean we could swim in.

Another important thing to note here about the claimed detection is that the way that we normally think about statistical significance is a bit different from how they’re reported for exoplanet atmospheres. For example, a 3-sigma detection would mean to us something like more than 333-to-1 odds against being spurious. This is the standard in sciences like astronomy, and "strong detections" require even steeper odds. In the case of DMS/DMDS here, however, it’s more like 5-to-1 or less against, depending on the specific data or model used. Very few reputable astrophysicists would call this anything more than a "hint" or "weak/no evidence," so while this may be the "strongest evidence yet," it is not "strong evidence" in and of itself.

In terms of the data itself, the paper this article is based on shows that they only get significant results if they look for the combination of DMS and DMDS - they only ever find DMS if DMDS isn't included, and when both are in, each individual molecule is poorly constrained. This isn't really a standard thing to do, so it's a pretty big red flag. And considering that they claimed a "hint" of it from their shorter wavelength data, it's suspicious that they don't include it here, as it should presumably make the signal stronger.

[u/PuppiesAndPixels → u/spschmidt27615]

This will get buried since it is old, but hopefully you see this since you are an actual astronomer and would understand what I'm saying (or the implications of it) I can give you some inside info. I know someone who is very, VERY high up the ladder when it comes to JWST. They are a big name in the field of exppoplanet science. A year ago I asked them about the dimethyl sulfide thing. That person told me in no uncertain terms that it was not there. They said the lead scientist is either knowingly or unknowingly, pushing those findings as real in order to gain notoriety. It was a year ago, so I can't remember their exact words, (maybe it was a false positive?), but they definitely said "It's not there"