this post was submitted on 10 Oct 2025
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Searching for signs of life on exoplanets is tough. (mander.xyz)
submitted 3 months ago by Dav09@mander.xyz to c/science_memes@mander.xyz
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[–] Legianus@programming.dev 3 points 3 months ago* (last edited 3 months ago) (2 children)

Astronomer here, the "life detection" on K2-18b was dimethyl sulfide (DMS) which may be ̶I̶s̶ ̶a̶n̶d̶ ̶r̶e̶m̶a̶i̶n̶s̶ a marker for life. What you get from the James Webb Space Telescope (JWST) is raw data that needs to be treated and calibrated to some extent to be usable in scientific study. This is called data retrieval.

However, the lead scientist on this paper claiming they found DMS basically used his own very specific way to do it and found very very weak signals in that way. Other scientist tried to both reproduce it in the way he did it and also with their ways to retrieve the data, but couldn't find anything. So it turns out, it was simply a non-detection.

Edit: It might be the case that DMS can be produced abiotically (scientific works of this year) as chosensilence pointed out correctly.

My main point is, that the DMS detection itself was a non-detection in this case

[–] chosensilence@pawb.social 2 points 3 months ago (1 children)

also, may i ask a question? you say "is and remains" a marker for life. i am not well read about these things, is that because DMS is only observed as a biosignature here on Earth, or are you saying it couldn't possibly have a nonbiological origin?

[–] Legianus@programming.dev 2 points 3 months ago* (last edited 3 months ago)

Sure. Generally, it is a marker for life as we see it being produced by living organisms on Earth (e.g. Algae) and it also should vanish quickly from atmospheres if it is not replenished.

However, as you correctly put it, there may always be a non-biological explanation as well for any of these markers, which we might not know as of yet. So far as I know, DMS has no non-biological explanation and is seen as a biological marker still.

Alas, the possibility of it being proven non-biological or even (as happend here) not a real detection makes it even more important to get more data and be very careful about the statements made from it than as otherwise those statements and/or connected papers have to be corrected/retracted. And if these then reach the public (and why wouldn't they with the possibility of alien life) then this could diminish the trust in science if it turns out to be wrong.

Edit: I had a look and as you stated for DMS there may indeed be abiotic ways to produce it (scientific works from this year). They found it in comets and could reproduce it in labs as well.

My main point of the original comment was to add that the detection (paper) itself was flawed. Regardless of DMS being a sign of life.

[–] chosensilence@pawb.social 2 points 3 months ago

oh hey, wonderful. thank you!