Astronomers Detect a Possible Signature of Life on a Distant Planet (opens in new tab)

That seems like a very landbased mindset. From a high level, what is an ocean but a thick atmosphere? I could even imagine an underwater culture would be quicker to explore because they would surely discover the surface of the ocean quicker than we discovered the concept of the atmosphere and that innately leads to the questions of whether the atmosphere has a "surface" and what is above it.

It would probably be useful for high speed travel. Speedboats can go a lot faster than submarines. Airplanes can go even faster, but they might be a bit impractical since they'd have to be full of water.

Also radio communications since radio travels much better through air than through water. Of course, they could just build antennas underwater and then float them above the surface to use them.

Navigating by the stars would be really useful, and for that you need to be able to see above the surface. I guess you don't need to go above the surface. A periscope would do the trick.

It might also be useful for energy generation. Wind power if the wind is stronger than ocean currents. Or solar because the light is stronger.

Orcas could very well be smarter than us, but it is extremely unlikely they'll ever evolve hands to build tools - it would be a radical and crippling change in their skeleton with absolutely no evolutionary pressure to do so. Primates (and koalas) didn't evolve hands with opposable thumbs to build tools, we did so because our ancestors got pushed into the trees. And orcas really need their flippers to be good in the water.

"If life evolves on a planet with land, instead of only oceans, imagine how much longer it would take to discover boats and submarines that can travel on and under the water!" - Xenobiologists on K2-18b after detecting possible signs of life on the Sol system's third planet.

Earth had precious little land, if any, over the first billion or so years too. The crust takes time to differentiate and pile up into cratons.

Though in this particular case it looks like the planet is a gas giant, plausibly with a water ocean but without any higher density rocky/metal core to make "land" out of.

I wonder how oceanic life would be able to record information. If we assume that extraterrestrial oceans would have lifeforms similar to corals and barnacles, how would an aquatic civilization prevent written information from getting encrusted with biofouling or keep it from corroding away?

I highly recommend reading Adrian Tchaikovsky's Children of Time series which explores this a bit.

I listened to the series, I enjoyed it a lot.

Overcoming water->land barrier seems comparable to overcoming land->air and air->outer space in the context of rocket launches.

How high are you? :D

The Great Filter hypothesis is based on an analogy with the European conquest of the globe in the 19th century. Little by little all the white spots on the map were first explored, then annexed. The (unspoken) parallel is that an advanced civilization would explore and conquer the entire galaxy. But even if a civilization could achieve interstellar travel capabilities, it is entirely possible that they colonize, let's say, only 80% of the galaxy, not 100%. Or maybe only 50% or 10%. If our solar system is in the complement of their zone, how would we know they are out there. How would we know there are aliens around Alpha Centauri, let's say. They could be busy living their lives, broadcasting in all the regions of the radio spectrum with abandon, maybe even nuking each other from time to time. And we would just hear absolute silence. The distances between stars are just so mind-bogglingly huge.

I think it would be cool if the conversation on this post could go more into detail about hycean planets instead of the pretty standard and played out one about the Fermi Paradox and Great Filters.

That stuff is interesting but I'd rather hear experts talk about less talked about stuff like hycean planets and detection methods of them and other bodies that are that size.

i don't see the connection. being the only intelligent beings in the universe (at the moment) lends credence to the great filter, and finding large numbers of other inhabited planets eliminates it, and in between why wouldn't it monotonically decrease?

My greatest desire is to know why we don’t see any galaxy-sized colonies. A great filter would certainly be a fascinating response!

There’s no evidence yet, but we also haven’t looked very carefully or in very many places. And we only know to look for planetary life as we know it.

The middle of the galaxy could have a wildly different composition and habitat for life than the outer reaches where we are.

Time is also another factor. Maybe the galaxy is perfect for complex life, we just happen to be early on the timescale and in another billion years or two life will be clearly abundant everywhere.

For some perspective, if you take the size of the Milky Way (100k light years) and relate it to the size of NYC (~30 miles), then 120 light years ends up being ~190 feet in NYC, or less than a city block.

  Now imagine if the odds of simple life becoming intelligent life that we could detect and could become spacefaring is 1 in 1 million.

Why not assume the odds are 1 in 200 million, so that there's only one such planet in the whole galaxy and there's no Great Filter to worry about? It seems just as valid, except "200 million" is slightly less aesthetically pleasing.

We already know that human-type technological civilization is extremely unlikely, since the planet was full of somewhat intelligent bipedal dinosaurs for about 100m years, yet none of them seemed to engage in mining, large-scale construction, severely disruptive extinctions, nuclear power... (humans will leave a thick geological layer of concrete and pollution, along with plentiful unique minerals coming from slag, plastic, etc.)

I really have no patience for this sort of p(doom) nonsense. If you make up numbers you can come to any quantitative conclusion you want. Mildly tweaking totally unfalsifiable odds makes the Fermi "paradox" go away entirely.

If you assume life is very likely then the Great Filter has to be an almost perfect filter to explain the Fermi Paradox. With fewer civilisations in the galaxy (<50) you might be able to assume that if 95% of them destroy themselves it would be unlikely we'd ever find life. If we assume 170 civilisations then the great filter would have to be something akin to a natural law.

My gut says that the Great Filter is real but probably doesn't filter more than 99% of civilisations. Were I to guess complex life is uncommon, and intelligent life very uncommon. The majority of planets which do develop intelligent life destroy themselves fairly quickly.

A lot of assumptions are made here about intelligent life with the great filter ideas. Intelligent life is not a fundamental phase of matter. It took a random walk over billions of years to end up there, with any point potentially leading to a deviation and entirely different outcome. Take the number of bacteria dividing over the last 4 billion years on earth to one and there’s your rate of intelligent life in the universe based on what we’ve seen on earth. Are there even that many planets or bodies in the galaxy for what a billion to the power of a billion to one odds or whatever absurd number this is?

On a related note, Birth-Death Formalism connects Jaynes' Prior Probabilities in a paper, "Do SETI Optimists Have a Fine-Tuning Problem?"

https://arxiv.org/abs/2407.07097

One of the authors posted an approachable video explaining how the ideas connect:

https://www.youtube.com/watch?v=b6-9Hq8dV_4

This argument is fairly dated now, we no longer need alien ruins to prove that humanity will probably destroy itself.

> it's an incredibly bad sign for us.

No reason to expect other lifeforms to be as bellicose and destructive us humans.

Technically that is the only natural source, it can be made industrially with hydrogen sulfide and methanol, both of which are very abundant in the interstellar medium and on gas giants (Neptune has large clouds of hydrogen sulfide). The reaction is catalyzed by aluminum oxide, which also occurs naturally. On a world with an aluminum-rich crust, I could see dimethyl sulfide being produced in volcanoes. It was striking that this planet had thousands times higher concentration of DMS than Earth; maybe it has vastly more algae, maybe it's purely geological.

It's absolutely amazing that we can even figure out molecules at that distance. I'm sure it's accurate but it's so sciency to me that it might as well be made up entirely. I can't begin to fathom that process.

From TFA, they’re going to continue observing it with JWST to gather more data. New telescopes dedicated to detecting life are being built now - they were basically right behind dark matter in scientific interest.

They will also start to simulate hycean planets to see if these chemicals behave the same way there as they do on Earth to determine if there is some non-biological reason why they could detect this stuff.

And challenge chemists to produce these compounds abiotically ?

I wouldn't trust Starship with a pair of cheap binoculars at this point.

The article isn't overly excited imo. It clearly states nothing has been proven for certainty, which is in alignment with what you're saying.

> Astronomers Detect a Possible Signature of Life on a Distant Planet

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

It's not fair to call it "trash"

You could have just read to the end of the article and avoided wasting the time of your "qualified" friends:

> Other researchers emphasized that much research remained to be done. One question yet to be resolved is whether K2-18b is in fact a habitable, Hycean world as Dr. Madhusudhan’s team claims.

> In a paper posted online Sunday, Dr. Glein and his colleagues argued that K2-18b could instead be a massive hunk of rock with a magma ocean and a thick, scorching hydrogen atmosphere — hardly conducive to life as we know it.

> Scientists will also need to run laboratory experiments to make sense of the new study — to recreate the possible conditions on sub-Neptunes, for instance, to see whether dimethyl sulfide behaves there as it does on Earth.

> “It’s important to remember that we’re just starting to understand the nature of these exotic worlds,” said Matthew Nixon, a planetary scientist at the University of Maryland who was not involved in the new study.

>but that doesn’t make it an exclusive biosignature. There are plausible abiotic pathways for DMS formation, such as in geochemistry we can’t know entirely about because we live on earth.

I'm sorry, but this is ridiculous. You started by acknowledging that it is indeed exciting, that it is something we only understand to be produced by living organisms. I wholeheartedly agree with that. And so the plausibility of an abiotic alternative is the big question.

You suggest that there are plausible abiotic pathways, but I think that's where this all starts to go off the rails, because I don't think there are in fact plausible abiotic pathways. We absolutely should attempt to model such possibilities and should be extremely careful about assumptions before working that out. But the state of our knowledge thus far counts for something too and it would suggest that such a process is pretty rare or unique. And then it really goes off the rails because instead of an actual example, you suggest not any specific known pathway, but a kind of bizarre philosophical musing that maybe there's "geochemistry we can't entirely know about."

We most definitely are capable of modeling chemical processes even if they don't happen on Earth. And there sure as heck is no such thing as a principle that things beyond Earth's surface are things we "can't" know about. I truly can't stress enough how ridiculous an assumption like that is.

We know, for instance, that gas giants are capable of producing phosphine, even though that doesn't happen on Earth. We know that the moon likely has a molten core. We know all kinds of things about atmospheric chemistry of planets and stars, because even if the abiotic processes can't be witnessed directly on Earth, we know enough about the principles of chemistry to model them in new contexts with reasonably high confidence.

And that's before we get to the idea that such uncertainty about off-world chemistry can be treated as tantamount to evidence of known abiotic process. It's nothing of the sort, it's more like "who knows, maybe it's possible." We do indeed have to figure out if there are such things as an aviotic process, but just the idea that, hey, who knows, something offworld might be happening is nowhere near enough to count.

https://arxiv.org/abs/2504.12267 matches the title ("New Constraints on DMS and DMDS in the Atmosphere of K2-18b from JWST MIRI") reported at https://www.eurekalert.org/news-releases/1080558, and it also matches the reported results.

Those DOIs have a different prefix, I think it might be in Letters

https://iopscience.iop.org/journal/2041-8205

It's still not out yet though. Also journals are often rather tardy or just straight up don't register the doi at all and still put it on their site, but maybe this is an embargo thing.

edit - is it possibly this after publishing? https://arxiv.org/abs/2501.18477

Lol, that didn't take long: https://youtu.be/82cLukqLgME?si=7PJMoGsxf6Qtaz87

Chemistry that indicates industry is signs of industry. In earth timescales, industry existed for effectively 0% of the time. Life existed for significantly longer though.

Even if there's life in lots of places, there may be no industry as we understand it anywhere else in the universe.

original source: https://arxiv.org/abs/2504.12267

There will probably be a first, perhaps it's this one.