These factors are what I call the “trappings of life”. It is a completely open question (and I mean completely) how likely life is to arise spontaneously when these factors are present. One single instance of life elsewhere or successful abiogenesis in the lab would change that, but we have neither.

The other part of the open question is how easily life is able to spread across worlds. This is why it's so vital to go look at Mars without contaminating the search. If life spreads easily (whether within the solar system or more widely), then we'll likely find traces of life there that look a lot like our own. If life arises easily, but doesn't spread easily, we may find traces of very un-earthlike biochemistry. And if life is rare, we'd expect to find nothing.

Any of the three results would have huge implications. And then rinse and repeat on Enceladus, Ganymede, Europa, and so on. And find a way to look at exoplanet atmospheres and chase stuff that comes in from outside the solar system. Even negative results will add enormously to our understanding.

At this point isn’t Mars already contaminated?

No, almost certainly not. There are individual living microbes and spores on the various landers, but unlike the microbiome that would travel with a human mission, they're not viable and have no mechanism to get to somewhere where they'd be viable.

I mean, you say that, but also this story was a thing that happened:

https://www.cnet.com/science/sea-plankton-found-on-the-outer...

The leading theory is air currents from the planet slowly contaminated the station over the decades, not contamination before launch. It's also then still pretty protected by radiation still being so close to Eath. Our probes go through pretty tight clean room packaging, shed almost all their outside layers before leaving Earth orbit while still being very toasty, and then get blasted by intense radiation for months and are finally separated by some pretty massive distances on the planet.

I agree it’s an open question, but I think it’s highly likely with lots of circumstantial evidence that life is an evolutionary emergent phenomenon where inorganic material reactions create life. We already know that’s the case in highly controlled environments. We don’t yet have confidence about the exact mechanism on Earth but based on those experiments it’s likely (& generally currently accepted as the most likely mechanism AFAIK) that the boundary layer of volcanoes (probably underwater) + some crucial initial elements being available causes life to form “spontaneously”. Given the elements required and their overall availability in the universe, it’s also highly likely these conditions reproduce quite readily & life is generally quite abundant. Similarly, significant levels of intelligence within animals seems like quite a common occurrence as well (great and lesser apes, elephants, octopuses, dolphins, wolves etc). Whether or not intelligence + physiological evolution + social evolution to take advantage of that intelligence to build things cooperatively is a huge unknown of course although I think it’s inevitable. On the other hand, how long life sticks around on a planet once it forms is an open question - it’s not clear if a life ecosystem that’s stable for billions of years is likely and I suspect there’s probably a small amount of filtering that happens where planets become inhospitable rather “quickly” and can’t support life for multiple billions of years (e.g. there were probably several events in our history where it could have collapsed).

Our type of society is probably much much rarer because you need access to mineral and energy deposits to go through each technological phase. For example, because of all the mining we’ve done, if humanity were to disappear it’s highly likely the Earth would not sustain another technological society because all the “easy to get to” deposits of crucial metals & things like oil are gone and there’s no way to bootstrap a technological society (it’s possible other kinds of resources could be developed to build other kinds of technology so who knows).

I think based on our existing body of knowledge, life is likely extremely plentiful throughout the universe at one point in time or another. Some form of intelligent life is highly likely wherever we find any life that manages to stick around through bilions of years. A highly technological adept species of life though is highly likely an extreme rarity and a planet gets one shot at developing it. Whether any manages to escape their home planet remains an open question that likely only we will manage to answer over the next thousands of years if we make it that far.

>Our type of society is probably much much rarer because you need access to mineral and energy deposits to go through each technological phase. For example, because of all the mining we’ve done, if humanity were to disappear it’s highly likely the Earth would not sustain another technological society because all the “easy to get to” deposits of crucial metals & things like oil are gone and there’s no way to bootstrap a technological society (it’s possible other kinds of resources could be developed to build other kinds of technology so who knows).

As I recall-though it's been many years-this was something of a premise in Farmer's Riverworld series. Once you've taken the first pass though historical mineral etc. resources, you don't really get a second pass.

Readily obtainable hydrocarbons are lost for the forseeable future. However, haven't we made it easier for future civilizations to obtain minerals and metals? We have extracted, refined and placed them all in concentrated surface areas all over the planet (i.e. city limits)

Except a huge amount of it is alloys. You’d have to reprocess it to extract out the raw materials which is much harder than mining ore and requires a lot more tech. Like things may be bronze plated but you’re not going to find a whole lot of bronze in 1 spot.

Wouldn't the next civilization just find itself mining the remains of human cities? IIRC, the majority of the copper ever extracted is still in use.

Cue Indiana Jones voice: you can’t just mine that—it belongs in a museum!

> I think it’s highly likely with lots of circumstantial evidence that life is an evolutionary emergent phenomenon where inorganic material reactions create life

Out of curiosity, if you reject religion, what other possibilities are there?

Just inorganic material combining at random and eventually, over about 10 billion years, randomly creating something that self replicates in some way, beginning the process of evolution through natural selection and inevitably progressing to life as we know it.

I don't think religion is needed at all for this. I also don't think this has to be a common thing (after all, here on Earth it only happened once, but it's also possible that once life is widespread it makes it very difficult for emergent new forms of life to take off).

Sorry, I meant possibilities other than "an evolutionary emergent phenomenon where inorganic material reactions create life"

Commenter is referring to the case where life is a common occurrence as an "an evolutionary emergent phenomenon where inorganic material reactions create life" in contrast to the case where life has only happened once, which would be more like an extremely lucky fluke where inorganic material reactions create life.

Where did you get 10 billion years of random chemistry?

The articles I read assert that life began just 500 million to 1 billion years after formation of earth. 3.5-4.1 billion years ago with an earth age of 4.5 billion.

The universe is about 15 billion years old, and chemistry didn't start with the formation of Earth.

Chemistry in earth certainly started with the formation of earth.

Are you suggesting that abiogenesis didn’t start on earth, but self-replicating molecules started evolving in earths protoplanetary disc?

Serious question, haven’t encountered that theory before. It’s kinda panspermia-lite.

I believe you may discussing at cross-purposes.

Presumably like your parent, I believed this was a discussion about the probability that life has originated elsewhere in the galaxy / universe, independently of life on Earth.

Kurzgesagt did a video on this recently https://m.youtube.com/watch?v=JOiGEI9pQBs

Simulation hypothesis: all this may be much younger than we expect.

Nonuniform physics—call it colliding universes or whatever, but the processes that gave rise to life on Earth may not be possible anywhere in this universe now. Including labs on Earth!

>>>I agree it’s an open question, but I think it’s highly likely with lots of circumstantial evidence that life is an evolutionary emergent phenomenon where inorganic material reactions create life. We already know that’s the case in highly controlled environments.

Did I miss some big announcements? Where has anyone created life from inorganic material reactions in a highly controlled environment?

Serious question, not trolling.

Seems to me that would be an insta-Nobel.

I overstated that life from inorganic in a controlled laboratory environment is what we have evidence for. What we do have evidence for is organic compounds forming from inorganic environments and we’ve shown certain kinds of RNA can self-replicate.

Unless life originated directly at the formation of the universe and panspermia is how life got to this planet, the only logical explanation is that life somehow emerges from “nothing”. We don’t know the exact mechanism and it seems much more likely that life originates on a planet rather than in space & arriving at a planet. The “intelligent” panspermia explanation (i.e. aliens seeding life throughout the universe to preserve it) would still require an inorganic origin for life.

This is what I referred to as "speculation" in the literature for life's origins on Earth. This speculation is a good first theoretical stab... or it might not be. Until life is created from inorganic matter in a laboratory (enabling us subsequently to estimate how rare or not it might be elsewhere in the observable universe), we should substantially dial back our confidence from "life is likely extremely plentiful throughout the universe at one point in time or another".

I agree that we are limited to "speculating" due to n=1. However, personally my sense is that simple life is more likely to be ubiquitous than not. This is informed by the fact that currently there is no evidence that conditions on early Earth were particularly unique in comparison to first principles modelling of rocky planet atmospheres**. This coupled with the relative speed with which simple life emerged points to it being a relatively probably event, though we can't be certain. I expect that with missions such as PLATO and the upcoming HWOs we'll have a better sense of the conditions on mature Earth like planets in the habitable zone. Though studying a large sample of early Earth's shortly after formation may be out of our reach for a while yet, depending on which particularly mission gets chosen.

**Not my sub-field. Extremely complex models. Much is still unknown.

To me the simpler question is “if life didn’t originate from inorganic conditions somehow, what other explanation is there? Life came into being with the creation of the universe?”. It’s possible the latter explanation is what happened, it just feels extremely unlikely. So the more likely explanation is that life originates from inorganic conditions. Then the question is where? Is it on a planet or in space? Panspermia doesn’t have a lot of traction because the mechanism of action seems too complex to have a good probability of success unless intentional (but then you have a question of how did life that started panspermia intentionally begin & you’re back to needing it forming spontaneously out of nothing).

And if “out of nothing” is the baseline condition, the most likely explanation is that it happens where there’s a lot of energy to sustain it while not enough to kill it, which means planets at the boundary of thermal activity (since we need something more direct than photosynthesis which is a relatively complex capability that came late in Earth’s cycle as far as we know).

Taking a slight sidetrack to relativity, consider just how absurd our universe is. To maintain the consistency of the speed of light from all reference frames, time (and 'real' distance) are instead the variables, and there is every reason to believe this is correct. If you didn't know this to be the actual case, it'd feel absurd to even consider it.

Trying to intuitively and logically reason about something with no answer in sight, all while assuming the truths of our era, may ultimately be pointless.

Our universe, logical though it may be, plays by its own rules, and many things will be simply irreconcilable until those rules are further elaborated on.

As an aside the big bang also does not really answer the prerequisite question of where the initial inorganic matter/energy came from. The idea there being some sort of a quantum fluctuation, which then begs the question of its origin. I suppose it's just turtles all the way down.

The Turtle way down is called 'Rechnender Raum' also known as

https://en.wikipedia.org/wiki/Calculating_Space

And if the turtles feel bored out of their minds, they go full

https://en.wikipedia.org/wiki/Ouroboros and eat their own behinds.

Which solves the problem of recursion, hen&egg nicely.

Consider black holes, white holes, wisely.

The question of free will? Just checksum errors in the substrate.

Because entropy, of course!

Chill...

> To me the simpler question is “if life didn’t originate from inorganic conditions somehow, what other explanation is there? Life came into being with the creation of the universe?”.

OK let's pretend to forget for a moment that we have no definition for "life". Here is what we know:

    - tons of examples of life turning into non-life
    - zero examples of non-life turning into life
    - a crapton of non-life around us

Based purely on that evidence what do you think is more likely: that non-life magically converts to life or, idk, how about it started with life and all that non-life you see is formerly life?

Hm what if you add a forth known:

- a lot of examples where life exists where we were thinking it should not be possible

I think it raises a bit the idea that life is in a way special and fragile at individual level but not that fragile as a whole.

I think you are taking the wrong tack in your approach to this. You keep saying life must arise at the end of an experiment. The thing we can do is work through to dna base pairs arise. If you are then in the right environment for random mixing of these base pairs for millions of years, I do think you'll get microbes.

It's a big mistake to say we have to run an experiment that produces living organisms from nothing to say we know how it works. And that likely took millions of years. That feels like an excuse to argue that it can't happen without some external power (not the sun, ha).

I don't think inorganic material reactions can be described as an evolutionary phenomenon.

It is evolutionary in the sense that the various reactions slowly changes the make up of the environment until the conditions necessary for life emerges.

idlewords was specifically mentioning that we have (found life elsewhere).

It was pretty clear to people that there would be no life 750 metres inside the earth crust below another 700m of ocean: too hot, no light, pressure, bla, bla. - And plenty was found. Of course it's an easy counter "Still Earth, haha! Doesn't count". So yes, it's back to the point that whenever we have developped tech to go look, we have found "whatever the tech could find". Except - for now - TV serials radio waves. That's true. And bacteria on Mars. Yes it's a glib way to put it but it's not an unfair answer to that criticism.

We've barely started looking. It's like picking up one piece of hay, not finding a needle and declaring there's no needle in the haystack.

No is declaring that there is no needle in the haystack. Please actually read my post.

absence of evidence is not evidence of absence

sorry your life has created this crusade of rhetorically reminding people about the absence is evidence

Not in general, just on this particular point. Because, in my opinion, we as a scientific community are currently flush with the (very cool) unexpected discovery of so many exoplanets and it is somewhat distorting our collective thinking about life and its origins.

We SHOULD (be flush and distorted). We can be realistic AND enthusiastic about it. Some technically challenging work was done and achieved results FAR FAR beyond expectations. That is a result worthy of changing outlook. Before, the outlook was on statistical grounds (the universe is so vast that there has to be). Now this outlook has been justified a billion billion times over. It's certainly time to be far more ambitious and inverse the presumptions that we had before.

I.e. before, "there had to be - some, somewhere" and now, "there is most likely all over the place".

You can make the less charged argument that expanding the search for life has in every case so far led to extremely interesting scientific discoveries. So as a pragmatic strategy, it has legs regardless of where you stand on the question of life origins.

Provided you're actively and systematically looking for evidence, then absence of evidence is evidence of absence.

But we've not even started doing that yet. None of the mars rovers have landed anywhere close to where we think is must likely to currently harbor life due to fear of contamination.

We've just now learned how to analyze atmospheres of exoplants.

5 years ago, we couldn't see exoplanets smaller than jupiter.

A decade ago, we couldn't see exoplanets at all.

We still can’t see the atmosphere of the majority of exoplanets. Can’t get around it unless we build a telescope thousands of times bigger than anything else or we make some incomprehensible breakthrough in optics. If we could we would detect life on another planet within a matter of a few hours of telescope time most likely.

I find the entire idea that life could only exist on earth farcical. A lot of people in this thread don’t seem to understand that we can’t directly image many exoplanets to begin with and that we haven’t even been trying to find life on other planets and moons in our own solar system, it has in fact been suppressed every time credible circumstantial evidence of life is found (Viking lander experiments and methane on mars both come to mind)

“I just want to be clear that we’ve definitely not actually found life. We’ve found likely precursors everywhere, habitable bodies everywhere, have plausible theories on how to go from precursors to bootstrapping, and see life in every corner of the planet we have explored. But just to be clear we haven’t actually found life anywhere else yet.”

Yeah, we know. So what then was the point of your post?

Well, perhaps you know that none of the recent findings are evidence of life, but in my conversations with others I have perceived a great deal of confusion on this point, even among scientifically literate colleagues. Also, the fact that we have zero understanding of the probability of abiogenesis is, in my experience, a greatly under-appreciated fact. I speculate that the way findings are reported contributes to this confusion.

Also, at risk of incurring a flame, I'll gently point out that you are folding into this confusion and reinforcing it with your language: "likely precursors everywhere, habitable bodies" ... we absolutely do not know that these conditions are "likely" precursors, which is a statement about a probability we know nothing about and as for "habitable" we do not actually know anything about whether or not a body is habitable in the sense of likely to spontaneously form life.

I went to a biology/astronomy talk where there was a researcher working on the sequence of chemical changes on the early earth without much water or atmosphere would need to create dna base pairs. It was stunning because they basically had a sequence of things and geological discoveries point toward the precursor chemicals being available. It's not that dna was just there.

This is not "life arising spontaneously". This is chemicals in an environment where they eventually build dna base pairs. Then after millions of years, perhaps you get microbes and go from there. Meanwhile we are getting water on earth from comets crashing down.

The “eventually build dna base pairs” (that continue self replicating) is the uncertain and possibly ludicrously improbable step. See for instance https://www.nature.com/articles/s41598-020-58060-0 which argues for a probability per exoplanet small enough that it hasn’t happened a second time in the observable universe. On the other hand, one of the self-organizing proposals cited elsewhere in this thread may turn out to be correct and the probability may be much higher.

The point is that, while there are some cool ideas on the table, everything hinges on the particular value of this probability (not just a qualitative story of how life might have arisen) and we don’t know what it is. Still relevant: https://blogs.scientificamerican.com/cross-check/pssst-dont-...

Sorry, I didn't see your posting before. The person speaking at the astronomy on tap presentation made it seem much more likely, basically given expected conditions on pre-biotic earth, very likely in a million year timeframe.

I'm a software engineer so I don't readily admit I don't know what I'm talking about. Are you in the field and can maybe elaborate on your skepticism? This fellow was pretty certain they've worked out several likely possible paths. This was last year.

typo "I readily admit that I don't know anything" ;-) And I have bad typing and proofreading skills!

Great comment! Indeed there is a recent Nature paper that's causing a lot of discussion that is investigating that missing link between the physics of matter and the emergence of the natural selection and evolution processes that give rise to life. this is a really fascinating area! https://www.nature.com/articles/s41586-023-06600-9

That link (going from basic chemical to bootstrapped evolution) is an entire field of research. Not one paper now and then. Labs, money, researchers building on each other's work... Just want to point out.

Any good (starter) books on this?

I have passed on the request to one of the scientists.

You call these factors "circumstantial evidence", but they are only circumstantial evidence if our ideas about what allows/causes/etc life are correct, which we have not validated at all.

If we can't promote abiogenesis in a lab our understanding is clearly limited, which is itself surprising. How many other processes in nature have we observed and not been able to replicate ourselves (or at least make progress towards replicating)?

“England has developed a hypothesis of the physics of the origins of life, that he calls "dissipation-driven adaptation."[3][5] The hypothesis holds that random groups of molecules can self-organize to more efficiently absorb and dissipate heat from the environment. His hypothesis states that such self-organizing systems are an inherent part of the physical world.[7]”

If Jeremy England’s hypothesis is true, then life shouldn’t be unique but rather inevitable, as life in general would be the way for matter to better dissipate heat, and better turn low entropy into high entropy.

In fact, if you watch what life is doing in terms of physics, then it’s obvious that all it does is consume low entropy (stored chemical energy, heat from heat baths), and dissipates it around very efficiently.

Even we, humans are more and more good at it: we take hydrocarbons chemical energy and turn it into work and heat. It’s not enough for us, we now consume energy stored in atomic bonds, and turn it into work and heat. We capture concentrated sunlight and also turn it into work and heat, etc.

Essentially, we are doing what we are supposed to do as a function of physical matter: we produce more entropy.

I don't think that's Jeremy England's idea.

https://en.m.wikipedia.org/wiki/Entropy_and_life

Henry Adams first put it to print in the 1910s, and Schrödinger did a fine turn on it and wrote a whole book in the 40s.

The idea that life exists as the most efficient method to facilitate thermodynamic equilibrium is older than the neutron.

It seems like a more fundamental phenomenon would be the ability to self replicate. I imagine some organic compounds forming a primitive vesicle in a relatively calm lagoon. As the vesicle collects more organics it gets too large and eventually blebs off a small vesicle (primordial fission). The heartiest vesicles that can replicate fastest tend to survive the longest and produce the most copies. Evolution takes it from there.

>> better turn low entropy into high entropy.

I took a double take and thought you'd made a typo, because I've never heard that assessment before.

I see what you're saying about dissipating heat and work... but life organizes. Most of that wasted heat from any organism is the result of its processing, consolidating and transmitting information. Which is probably the only counter-entropic (extropic) process we can observe in the universe. My view has always been that life fights against entropy.

>but life organizes

Yes, and that's the interesting part. In the right circumstances, more entropy doesn't mean less complexity. Matter can become more complex and less entropy locally if that results in increase of total entropy in the system. This can occur, for example, if we have constant flow of concentrated energy on some local areas of the environment that continuously wants to spread out. Because the system as a whole "wants" to maximize its entropy as fast as it can, and it statistically "searches" for the shortest paths possible. This may result in natural occurrence of more and more complex molecules that dissipate heat more and more efficiently.

It's like the planet's atmospheric processes, for example. Where differences in heat concentration don't just spread out in linear gradients but can form complex structures like vortexes, hurricanes or even stable geometric hexagons (like the famous hexagon storm on Saturn), etc.

>My view has always been that life fights against entropy.

Yes, it "fights" against entropy to exist, but it exists solely by processing low entropy into high entropy. Maybe that's why it even exists in the first place?

This part is better addressed in Jeremy England's work, for more basic explanations you can refer to videos like

this: https://www.youtube.com/watch?v=GcfLZSL7YGw (it's a very good video on this topic by PBS)

I would turn this argument around and say if life elsewhere is more likely, than it should be more likely that life from beyond has found us. If the likelihood of life elsewhere is so high that it has to be true, to me it would also be true that life should have found us by now

I really don’t think people are talking about intelligent life here.

We’ve also found water on the moon.

And we know at least one Jupiter satellite has water.

So that’s at least 4 bodies in the solar system that have water and all the bodies where we have successfully landed more than 1 rover have or had water (earth, moon, mars).

Every body where we could have discovered water, we have discovered water. Seems like bayes theorem indicates that water is also probably highly available in the universe.

We came across a tiresome HN comment almost instantly in this thread...

"we find evidence that life is more likely than expected"

But only after we really lowered our expectations in the first place. I have an old book, about the Viking Mars lander, describing the technical details, before the rover succesfully landed on mars. It is full of optimism and a strong expectation, that it will find evidence of at least bacteria.

And before we had strong telescopes and rockets, there was a strong expectation, that Mars has developed life.

We know, that bacteria can survive in stasis mode on asteroids - yet we have not found life on any other planet.

Those original expectations weren’t based on evidence though.

> we find evidence that life is more likely than expected

The easy steps for abiogenesis keep getting easier and easier.

Meanwhile, we keep having absolutely no idea of the difficulty of the hard steps. Yes, technically that means life is easier than we expected, by some completely insignificant margin.