The search for extraterrestrial life as we don’t know it (opens in new tab)

Very, very unlikely like astronomically so. Most microorganisms are so small they're practically transparent so we have to exploit biochemistry to "stain" them - hence why you'll often hear of bacteria classified as either Gram positive or negative, because of the Gram stain. If the biochemistry is unique or even slightly different i.e. right handed chirality, we'd basically have zero of our usual tools at our disposal.

There's already a whole world of terrestrial microbes that we expect or even know for certain to exist but can't culture, let alone stain, which means we can't really study them. We'd (theoretically) eventually notice them on electron microscopy slides though, which is how we know there's many unculturable microbes, but whether we'd recognize them as alien is a completely different matter. The microbial world is very diverse and there's nothing I can think of that'd set something apart as alien since we can analyze the chemistry with an electron microscope.

Not at all familiar with biochemistry but octopuses are aliens on earth with very different evolutionary track having developed ‘brains’ before our ancestors did independently! It’s crazy we don’t study things like cephalopods like we do SETI etc…

"Shadow biosphere" may be a useful search term.

We didn't even know about Megaviruses[0] until 2010.

[0] https://en.wikipedia.org/wiki/Megavirus

If found, how could we even be sure that their origin was extra terrestrial?

We're not really looking for microbes.

Sure, they can still be very interesting from the bio/chemistry point of view. But it's the advanced civilizations that we're really after.

I wrote a little blog about this many years ago that’s still online on my basically unupdated site:

https://adamierymenko.com/titan/

In this I’m at least speculating that Titan might be likely to host alien life in its steamy cryotropical environment. I’d love to see NASA sink a submersible in those methane seas and look for cryowhales. (Or more likely cryobacteria but cryowhales would rule.)

I’d expect life there to be wholly biochemically alien, probably based on methane or ammonia as solvents, and probably very metabolically “slow” compared to most life here. We might miss even macroscopic Titan life without time lapse photography.

To any intelligent Titanians we would look like the Balrogs from Lord of the Rings: burning lava monsters with blood of molten water.

Counterpoint: Alien life will probably look very similar to life on earth. If you look at evolution then countless species have evolved into something crab-like: https://www.youtube.com/watch?v=wvfR3XLXPvw Turns out that their form is pretty good for survival. While biology can take on a myriad of forms, the competitive nature of life will weed out a lot of them. And since the rules for biochemistry are the same across the universe similar traits that are beneficial here will probably be beneficial there.

I am in the same boat as you.

There is also this to consider: limits of our own imagination/ comprehension.

If we are like microbes swimming inside a droplet of water, we won't be able to imagine/ comprehend / detect beings of the scale of say flies.

Our mental abilities may also be limited in similar ways. I think that puts a limit on what we can perceive / detect / understand.

Even further - not only the development of biological life forms on other planets would totally depend on the circumstances on that planet and create unimaginably variable life forms, but also these very different life forms would develop very different cultures and as a result, very different technologies. So even when we look for radio signals, we are looking for something that totally depends on our own technology, which is the product of our own civilization that is in turn the product of our own culture, which is a product of our own biology that was created by the circumstances on our planet.

Question is how does this broadening of horizons actually help with anything? When we are heavily constrained on both our ability to collect data and analyze that data, exploding the search space seems counter-productive.

We need some way of prioritizing the search work and for that purpose looking first for life as we know it makes sense as that is where we are most likely to be able to identify life.

If searching for life as we know it does not produce results then of course it makes sense to broaden the search. But that is more relevant debate for our children than for us.

The thing is, people don't realize this argument fully. If you are to accept that life could take countless forms, most which we could never recognize or begin to understand, then it's quite possible rocks are lifeforms, as we don't recognize them as life now nor understand how they could be living. Since most people seemingly don't like the argument that rocks are living, then this shows that this argument (along with others) is flawed with very definition that they want "life" to have.

It is a fun thought, but chemistry is not infinitely complex. Much like the Fermi paradox, once you start applying real world qualifiers on chemistry of complex life the search space becomes quite small.

https://youtu.be/469chceiiUQ

Life inside of stars does enable different options.

I used to think that too. Life could be anything; crystals, pure energy, eddies in the superfluid cores of neutron stars, swimming in seas of metallic hydrogen in Jupiter's core, living clouds floating in Venus' upper atmosphere.

The trouble is that when you start asking yourself about what the fundamental nature of life is, all the fun stuff starts to fall out.

For life to be life, it needs to do work. You need a metabolism. You need to "do stuff". The only way to do work ("work" in the physics sense) is to leverage an energy gradient; you need to have hot/cold, high/low pressure, bright/dark, high/low salt concentrations, high/low energy chemicals, positive/negative charge, etc. And you need to extract work from the differences between them. Therefore, you need to have a physical barrier between your high/low energy states; if you didn't, the system would reach equilibrium without you. So you need a physical barrier, it has to be a solid or liquid: you've eliminated your beings of pure energy, superfluid eddies, living clouds.

It's all well and good to use whatever weird energy gradient you want, but most energy gradients are simply too inconvenient; if you want to get energy, chemistry is ultimately going to be the only one that works. It's fine for plants to break water molecules with relatively high energy photons, but you can't build complicated structures with light. You need chemistry. And for chemistry you need to be in the liquid phase. So you've eliminated your crystal based life.

So everything is chemicals with complex structures in a liquid. It doesn't have to be proteins constructed with amino acids, it doesn't have to be ribosomes constructed from RNA, but you need some sort of 'interesting' chemical. How do you build interesting chemicals? Well you have to use carbon. You have to use carbon, no other element fits the bill. The metals are right out; they only form metallic bonds and ionic bonds which are non-structural. The noble gases are out because they don't do chemistry. The halogens are out because they can form just the one covalent bond. The chalcogens (oxygen, sulfur, etc) are also out for the same reason; with only two covalent bonding points you can form chains and rings, but not a branching structure. Nitrogen is too happy to form a triple bond with itself, producing a gas, so basically all molecules with lots of nitrogen atoms are explosive. Phosphorus is a decent candidate, but its chemistry is very finicky. Carbon is great, because it forms 4 covalent bonds that are not too strong and not too weak. Silicon is ... ok? But it cannot form double bonds, it tends to form weak bonds, and is unstable in most chemistries.

So life has to be carbon based. This puts an upper limit on temperatures, because interesting carbon chemistry breaks down at high temperatures. Venus is out, the depths of Jupiter are out.

So we're looking at other solvents besides water. Methane is a great candidate, and as a result lots of people are clamoring to get a Titan mission going. Ammonia is something people talk about, but it's unlikely to be able to form ponds or oceans on a world; it's probably going to break down into methane and molecular nitrogen, because again, carbon rules. But if we detected a large amount of ammonia in the spectra of a planet that could maintain temperatures consistent with liquid ammonia, you could bet that everyone is going to clamoring to study it in detail.

So what are we looking at? Carbon based life on planets with liquid oceans. Which is basically the same as us. We haven't gotten here because we're biased towards what we're like, we've gotten here by starting from first principals, considered everything, and eliminated the things which are impossible.

This isn't true, because information complexity and structure are measurable physical quantities.

(In the same way we recognize language vs random noise even if we can't understand it.)

Alternatives to the biochemistry of Earth life are hard to imagine. Silicon replacing carbon is one possibility but, as yet, despite silicon being vastly more common than carbon, we know there is no silicon life on Earth. It's just at too much of an inherent disadvantage, if it is even possible. I would bet on panspermia over silicon life.

"V'Ger": https://youtu.be/kHUZCVl28lg

> We're certainly not going to be detecting a world full of microbes from light years away.

JWST would be able to detect an oxygen rich atmosphere like ours, which is a sure sign of life. Oxygen rich atmospheres are not a stable equilibrium; without all the plants and plankton on Earth, the oxygen in the atmosphere would all recombine, and Earth would be left with an atmosphere with no oxygen but additional CO2.

Atmospheres can either be CO2 rich or methane rich; they can't have significant amounts of both CO2 and methane. They don't exist in equilibrium; either a planet will preferentially convert CO2 to methane or methane to CO2, and there won't be any left of the other.

There are a handful of other atmospheric biosignatures that JWST can detect. Chemical compositions that are a sure sign of life; chemical signatures that are conclusive or strong indicators that life is present, even if we can't classify or describe it. Classifying exoplanets' atmospheres is a primary mission goal of JWST; it's what it's designed to do, and it's doing it right now.

I think we're quickly moving towards living in a sort of poor man's Dyson sphere. More and more of our communications are being enclosed in optical fibers that leak virtually no radiation. Our free space comms are increasingly designed to operate on diminishing amounts of power, and to be practically indistinguishable from noise. We may be a dark planet by a couple centuries from the invention of radio.

Chemical changes to our atmosphere might be detectable from afar.

That "We're certainly not going to be detecting a world full of microbes from light years away" is debatable.

Changes that are not geological, like Earth's great oxygenation event could be vivid enough to be detectable among exoplanets.

> it seems like they are practically inevitable once those conditions exist

Given that we have exactly one occurrence of Origin of Life, how did you conclude this? From life originating quickly on Earth once it had cooled enough? That could be explained by the conditions in which life might originate not persisting for very long after a planet forms.

We inadvertently did something similar when we discovered the New World. Didn't work out so well for the natives.

That time was an honest mistake, but maybe we should stop trying to play God for a while. At least until we are advanced enough to create our own universe to experiment with.

Might be illegal, against some interstellar law.

no, common hallucinogenic tropes are just remnants of our evolved collective unconscious; not any proto-communications from other dimensions.

i am plenty familiar with them and other characters, and their lessons always seemed terrestrial, subconsciously familiar.

That's like saying studying ambien will unlock the secrets to time travel.

> there's a very significant movement happening within factions of the US government to push disclosure on potential non-human intelligence visiting earth.

<yawn> Pushing for disclosure is very different than there being anything to disclose. Get back to me when they actually disclose anything worthy of being attributed to non-human intelligence.

There is zero consensus that there is a "non-human intelligence visiting Earth". There is, one could argue, a phenomenon of some kind, either real or imagined, but nobody seems to know what it is. And yes, I’m familiar with the subject, and I’ve been following it for decades.

Also, I think "disclosure" is somewhat of a misnomer. If people don’t know what it is, there’s nothing to disclose. People have been beating the disclosure drum for years. Nothing really has happened except some people made a bit of money selling people on the idea.

And for all intents and purposes, our world-spanning civilization is much too primitive to even begin to disclose something like this if it were true. 85% of the people on this planet believe in superstitious nonsense. We aren’t ready to accept the existence of aliens on other worlds or parallel universes, let alone accept our own brothers and sisters who have a different skin color.

Given what I’ve seen of humanity, the zoo hypothesis is the best thing we can hope for. We just are incredibly stupid as a species at this time and place. I can’t imagine why any alien would want to have anything to do with us.

Funny how both UFO and Angel/Devil sightings went down just as ubiquitous personal video recording devices became commonplace...

Disclosure == Rapture for the #ufotwitter crowd. It's basically a religious cult.

"...An UFO has landed in America...the only country UFO's only seem to land in..." - https://youtu.be/HIVZa7c7WZU

The mention of silicon as a potential carbon replacement is also explored a bit in the movie "Ecolution" from 2001 - the half-life for replication is way short and (spoiler) they use an analog of cyanide to destroy the silicon-based aliens

It’s a reference to some old fashioned language used in older sex education materials.