“Most promising signs yet” of alien life on a planet beyond our Solar System

Here's the primary source

https://iopscience.iop.org/article/10.3847/2041-8213/adc1c8

They possibly detected dimethyl sulfide, which is only known to be produced by living organisms.

only know to be produced.....is a whoa bessy phrase,?¿ as in 70 years ago an undergraduate figured out that dimethyl sulfide was produced by living organisms and he asked his professor what else made it, and got shrug and "nothing else I know of" and everybody has been cutting and pasting since, OR, an international team spent years and millions working on the chemistry behind dimethyl sufide in an epic known to all quest to determine it's origins. Science does have an issue with cutting and pasting ancient mistakes, and then bieng exceptionaly reluctant to change and move forward, not to mention that SETI, and the rest of "alien" research is most definitly tainted with public fantasy and entertainment industry influence, so even with one of the notoriously oderiferous sulfide compounds present, I wont hold my breath

Ya, it’s a bit less exciting, but I bet we’re about to learn many new ways to produce dimethyl sulfide outside of a living organism

actually we know how to produce it without involving living organism

https://en.wikipedia.org/wiki/Dimethyl_sulfide#Industrial_pr...

And the question is even more complex: not whether producing dimethyl sulfide "from scratch" without involving living organisms of the familiar sort is possible (of course it is), but what the hypothesis that each of the numerous possible ways to produce dimethyl sulfide happens naturally (or that alien lifeforms want a lot of it) implies about the environment of the exoplanet.

actually a living organism is needed to produce it this way

Wikipedia says "In industry dimethyl sulfide is produced by treating hydrogen sulfide with excess methanol over an aluminium oxide catalyst”.

Which part requires a living organism?

Virtually all of them involve non-trivial design by sentient beings.

I think they are being a little glib by saying a human is need to make the industrial processes.

Well, someone needs to treat the hydrogen sulphide with excess methanol over an aluminium oxide catalyst. I suppose a robot could do it...

For a non-life explanation, you're really looking for something that could plausibly happen in (abiotic) nature, not an industrial process.

I'm not convinced about the methods. It looks a lot like p-hacking to me: they have a highly specific hypothesis drawn from a large universe—that dozen or so molecules (§3.1) in their infrared spectrum model they're fitting experimental data against. I don't buy the way they created that hypothesis. The put a handful of highly specific biosignature gases into it, things that were proposed by exobiology theory papers. One very specific hypothesis out of many, and a low likelihood one. And that's the hypothesis they get some borderline ~3σ signals for? Really?

edit: Any chance someone might have the charity to explain why my criticism is so far off-base, according to the HN consensus?

The only thing that could make a nerd happier than detecting alien life would be detecting alien robots.

> which is only known to be produced by living organisms.

Comets with DMS: https://arxiv.org/abs/2410.08724

And the interstellar medium.

"On the abiotic origin of dimethyl sulfide: discovery of DMS in the Interstellar Medium" - https://arxiv.org/abs/2501.08892

"...Although the chemistry of DMS beyond Earth is yet to be fully disclosed, this discovery provides conclusive observational evidence on its efficient abiotic production in the interstellar medium, casting doubts about using DMS as a reliable biomarker in exoplanet science..."

  Which part requires a living organism?

haha. Do you really need a hint?

So if I understand correctly, this[1] is what they did?

[1] https://xkcd.com/882/

Wait, what's the difference?

Thank you for posting this. Really balances out all the conjecture.

I'm going to double-down on my stubborn, unpopular opinion. This is my best attempt at explaining my criticism:

- Alien metabolites are a low-prior probability hypothesis. Dimethyl sulfide is a long-postulated biosignature with no natural source, so, it's low-prior

- The paper's model fits Webb data—a handful of photons—against no more than 20 candidate molecules, combined across all of their atmospheric models. Many of those gases are drawn from that low-prior "alien metabolite" class

- There's a much larger class of strongly infrared-absorbing gases, that can naturally occur in planetary atmospheres. Beyond those included in the 20 candidates. These (should!) have higher prior probability of occurring in Webb data than alien metabolites. (This class is so large and complicated, there's major spectral features in our own solar system's gas planets we haven't characterized yet)

- If you were to fit Webb data against that expanded class, those alternative hypotheses, you'd get a large number of 3-sigma detections by pure chance.

- The Webb data is too weak to distinguish between these. With only a few bits of information, you can distinguish between only a small set of alternative hypotheses

- This paper elevates the alien-metabolite hypothesis very highly, and that is why when it has a spurious statistical detection, it happens to be an alien metabolite detection. Because that hypothesis is overrepresented in their model

- The root problem is that since there's only a trickle of real data from this exoplanet, from Webb, it's unlikely one can infer anything super interesting from those few bits

Don't be bothered by the down votes. HN consensus is not something worth pursuing. Your criticism is valid, it's just that it runs against what HN readers want to believe in this instance. Readers here like to think they're motivated by reason and intelligence and whatnot, but that is laughable - examples of logical fallacies and assertions of fact rocketing to the top comments abound. Overconfidence and readiness to accept bold claims is a more dangerous cultural dysfunction than the lack of seriousness and ubiquitous monetization that plagues other platforms.

In any case this study will likely go on the pile of papers judged by time to be an overreach of conclusions and a dead end.

But in a concentration sufficient to be visible from this far away with spectroscopy?

It's not definitive but it is suggestive. A detection would require multiple pieces of evidence. We should be building specialized space telescopes designed specifically for the characterization of extrasolar planet atmospheres, since that's the best way we have to potentially detect something.

Alien life could just be microbial, while alien robots would require an advanced technological civilization, I guess

A lot of science papers are like “we found a hint of this thing, we need to do more research” and it’s reported as “ALIENS??!?”

I understand why this is the case but I think it can lead to a loss in trust in science when the reporting jumps to conclusions that aren’t supported by the research itself.

In this case the abstract is far more grounded. In particular,

> The observations also provided a tentative hint of dimethyl sulfide (DMS), a possible biosignature gas, but the inference was of low statistical significance.

> We find that the spectrum cannot be explained by most molecules predicted for K2-18 b, with the exception of DMS and dimethyl disulfide (DMDS), also a potential biosignature gas.

> More observations are needed to increase the robustness of the findings and resolve the degeneracy between DMS and DMDS. The results also highlight the need for additional experimental and theoretical work to determine accurate cross sections of important biosignature gases and identify potential abiotic sources.

Well, there could be nanobots...

The scientists are also saying ALIENS! but they're covering their backs, they want their research to make headlines too

Ugh, "alien life" is a reasonable title, IMO. I think the sensationalism is happening in your head, that you're imagining the Borg or little green men.

I'm imagining some new kind of volcanism and one less way to detect life. Or, as my wife put it, "Ah, rock babies again."

also: https://arxiv.org/abs/2504.12267

(if you want a cleaner interface)

I think you have misread the abstract. The 'low statistical significance' was a [prior work](https://iopscience.iop.org/article/10.3847/2041-8213/acf577). This paper has increased the significance to 3-sigmas which is on the lower end but still quite significant.

Yes you’re right, thanks.

I don’t think it’s an unreasonable title, but it’s also not accurate. The paper states quite clearly that they’ve found reasonable evidence of a known biomarker. They don’t know enough to say whether it’s from a biological or some abiotic process (but speculate a little about what that might mean and what evidence they would need to take that further).

That’s quite a different tone from the article, and I think the comments here and elsewhere online reflect that.

More like big green algae?

False positives are acceptable if the goal is to generate leads to follow up on. If the detection was due to chance then it won't hold up to further measurement. There's few enough hits that we don't need to worry about being more rigorous (and potentially introducing false negatives) at an earlier stage.

Given the context, a publication seems appropriate. A high profile similar example is when neutrinos supposedly broke the light speed barrier. If the mass media misrepresents things that's hardly the fault of the scientists.

Yes, this is what scientists are assuming as well. The first real step is to work with chemists to try and find a way this could be created in such large amounts so consistently, as well as additional observations to remove noise from the data.