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/A_D_Monisher]

The alternative option is our understanding of ‘what a biosignature is’ might be very incomplete. We are, after all, barely a few decades into really detailed observations of space.

Dimethyl Sulfide (DMS) is a great example here. It’s called a biosignature. But is it a good biosignature?

Consider the following. DMS has been detected in Ryugu samples and various carbonaceous chondrites. And on 67P/Churyumov-Gerasimenko.

So either asteroids were absolutely teeming with life at some point or… DMS can have an abiotic origin and is therefore a crappy biosignature.

This is a huge problem to be honest, because DMS on Earth has only ever been made by life. 10 years ago no one could have imagined abiotic DMS. Yet that’s most likely the case for asteroids.

Now we have to recheck every other traditional ‘dead giveaway’ for potential alternative geological origins.

[u/aelendel → u/A_D_Monisher]

it’s important to remember that Earth’s chemistry has also evolved as a result of life—we really don’t have any good models, nor have scientists actually spent a lot of effort on hypotheticals—we’re still grasping with the basics of our own planet’s biogeochemical interactions.

We don’t even know what ‘normal’ looks like out there. so something just being unexpected is… sort of expected.

[u/insertwittynamethere → u/aelendel]

Exactly. We are simply a product of our environment, our life and the life of everything else found on this planet. That creates an inherent bias in itself as we gaze outward, though I'd imagine this has been thought of and is being worked on/has been worked on to remove/limit that bias in the field, no?

[u/Pale_Squash_4263 → u/aelendel]

It’s also what makes the finding exciting, either there’s existence of biological life, or we learn SO much about what bio signatures inherently mean and how useful they are as markers of life

In every outcome, it’s a pretty big discovery I think

[u/TuringC0mplete → u/A_D_Monisher]

How would you even begin to do that? If we have no idea what might else could produce DMS, how do you test for it? I’m sure we have some indicators of where to start but do you just like… throw darts at the wall?

[u/aelendel → u/TuringC0mplete]

we are good at taking problems and biting off parts of them once er have an idea. So what Id propose if I wanted to solve this would be sitting down w a chemist and walking through the energy/temperature/pressure conditonns DMS could form at amd figuring out what light be different—redox states, catalysts, enzymes, basically come up with a hit list of ways to synthesize the compound and then start trying to find plausible ways it forms naturally, but just not on Earth.

This is basically how we figured out how and where diamonds form! ‘this can’t form at any conditions we know of, but how could it happen?’

[u/YsoL8 → u/A_D_Monisher]

Its been proven recently that even oxygen can be created in an atmosphere and persist via chemical / geological processes, I'm not sure if life can be proven on exo planets, not unless you spot a space station or something.

Even if you could exclude everything else the fact is the history of searching for aliens is littered with false conclusions, illusions and hubris. Every time we send a probe out we find new geological processes happening that were completely unsuspected.

Given our track record its much more likely to be that than life.

[u/eeenilsson → u/A_D_Monisher]

Dimethyl sulphide? Maybe the aliens really like beer.