“After a year of review, they have come back and they said, listen, we can’t find another explanation,” said Acting NASA Administrator Sean Duffy. “So this very well could be the clearest sign of life that we’ve ever found on Mars, which is incredibly exciting.” [1]
> The Perseverance rover has explored and sampled igneous and sedimentary rocks within Jezero Crater to characterize early Martian geological processes and habitability and search for potential biosignatures ..... the organic-carbon-bearing mudstones in the Bright Angel formation contain submillimetre-scale nodules and millimetre-scale reaction fronts enriched in ferrous iron phosphate and sulfide minerals, likely vivianite and greigite, respectively.
> Organic matter was detected in the Bright Angel area mudstone targets Cheyava Falls, Walhalla Glades and Apollo Temple by the SHERLOC instrument ..... A striking feature observed in the Cheyava Falls target (and the corresponding Sapphire Canyon core sample), is distinct spots (informally referred to as ‘leopard spots’ by the Mars 2020 Science Team) that have circular to crenulated dark-toned rims and lighter-toned cores
> PIXL XRF analyses of reaction front rims reveal they are enriched in Fe, P and Zn relative to the mudstone they occur in ..... In the reaction front cores, a phase enriched in S-, Fe-, Ni- and Zn was detected
> Given the potential challenges to the null hypothesis, we consider here an alternative biological pathway for the formation of authigenic nodules and reaction fronts. On Earth, vivianite nodules are known to form in fresh water ..... and marine ..... settings as a by-product of low-temperature microbially mediated Fe-reduction reactions.
> In summary, our analysis leads us to conclude that the Bright Angel formation contains textures, chemical and mineral characteristics, and organic signatures that warrant consideration as ‘potential biosignatures’ that is, “a feature that is consistent with biological processes and that, when encountered, challenges the researcher to attribute it either to inanimate or to biological processes, compelling them to gather more data before reaching a conclusion as to the presence or absence of life .....
> The Planetary Instrument for X-ray Lithochemistry (PIXL) is an X-ray fluorescence (XRF) spectrometer mounted on the arm of the National Aeronautics and Space Administration’s (NASA) Mars 2020 Perseverance rover (Allwood et al., 2020; Allwood et al., 2021). PIXL delivers a sub-millimeter focused, raster scannable X-ray beam, capable of determining the fine-scale distribution of elements in martian rock and regolith targets. PIXL was conceived following the work by Allwood et al. (2009) that demonstrated how micro-XRF elemental mapping could reveal the fine-textured chemistry of layered rock structures of ~3,450-million-year-old Archean stromatolitic fossils. Their work not only pushed back the accepted earliest possible window for the beginning of life on Earth, but also demonstrated that significant science return might be possible through XRF mapping. PIXL was proposed, selected, and developed to carry out petrologic exploration that provide the paleoenvironmental context required in the search for biosignatures on Mars, analogous to Allwood et al.’s earlier work.
I like your analysis, but, personally, I am struggling with "Absence of data/other possibilities is pointing us to conclusion"
It should (IMO) be reported as, we just don't know (yet), there's some really fascinating things that we cannot explain in any other way, yet, but that doesn't actually mean that we know for sure.
What's not to understand - it's precisely the argument theists have put forward for millenia
"We couldn't find anything to show it wasn't a god, so it must be a god"
Calling one group "smart" doesn't change the process or the outcome - the absence of data is not data, it's just that we couldn't yet find the full explanation.
One day we might, it might actually be life, but we don't have that right now, so, actual science demands that we withhold any wild speculation.
No, because theism is missing the first premise. The equivalent would be:
- We have observably seen and reproduced god bringing someone back from the dead
- We can find no other explanation for this thing coming back from the dead
- It was likely god who brought this thing back from the dead, but we want more data
The first premise has never happened, there is not any equivalence...
Actually (It's too late to edit) we do have this curious thing
Aliens - we claim/recognise that statistically the size of the (at least observable, if not entire) universe and number of habitable planets with all the right ingredients for life that there must be life out there... somewhere
But we don't have an ounce of evidence (neither for nor against)
God(s) - we don't have any evidence one way or the other, atheists just say "It's impossible", theists say "It's the only answer", but, as already mentioned, there isn't any actual evidence that can lead us to a conclusion. (This will be misread as an argument for god(s), but it isn't. And even if it were, there's still a massive step between that and the Abrahamic God being the dude)
Which takes me right back to where this started. The supposition that the features of mars are signatures of life, we don't know at this point, all we actually know is... we haven't found anything else that we can say they are.
Anything is possible but unlikely we would find it unless there are buried megaliths signed by humans with graphic pictures. Even on Earth it would be hard to prove we were ever here after half a billion years after we destroy ourselves. It might not even take that long. Most things will rust, decompose, shatter into something resembling dust and many coastal regions will get recycled by plate techtonic movements. Mars has been a dead planet for a long time no magnetosphere, probably how this one will end up at some point.
Eukaryogenesis != Multicellularity. There are tons of unicellular eukaryotes. Also, multicellularity has evolved a bunch of times, at least in eukaryotes, so I doubt it's that rare.
If your thesis is specifically that oxygen-powered metabolism fueling multicellularity is rare... that wasn't clear. And I'll still say that endosymbiosis being the shortest path to scaling oxygen metabolism is probably Earth happenstance (with a reminder that cellular endosymbiosis is also common). But some critter had to originally evolve oxygen metabolism before being turned into mitochondria. What if that had evolved in a cell prepared to directly take advantage of it?
But no multicellular prokaryotes. You're right that eukaryotes can be single celled. But my hypothesis is that multicellular life is rare because eukaryotes are rare.
The second half of my comment still applies then. I think Earth-style eukaryogenesis is probably just one way to achieve the energy budget and complexity needed for complex multicellularity... bearing in mind, of course, that colonial bacteria that collaborate for survival definitely exist, spirulina for instance, stromatolites, and all the gross things that form biofilms.
> Which in turn depends on the endosymbiosis of mitochondria.
Which in turn depends on existing enough atmospheric oxygen for mitochondria to make sense in first place. I believe the filter is atmospheric oxygen. If Earth had more iron in the crust, perhaps the cyanobacteria would never finish oxidizing all of it, and we would be doomed to only host microscopic life forever. Macroscopic life requires high-energy metabolism molecular oxygen allows.
It's pretty unlikely that life emerged independently on two planets in adjoining orbits.
The much more reasonable explanation is that life emerged on one planet and transferred over. Earth and Mars aren't particularly close, but they're close enough for material to transfer between them, particularly early in the solar system when there were far more asteroid impacts kicking rocks and dust out into space.
Earth is strange - a billion years of water and chemistry on every grain of sand on every beach. Every combination of temperature, sunlight, wetting and drying as tides slosh things around in every phase.
It's like a bioreactor for creating life. One could argue, it's highly unlikely given all those experiments and all that time, that life would avoid being created.
And Mars? It has a moon too, two of them. Tides as well, lunar and solar. Pretty much the same deal.
Why would you say it's unlikely? For all we know simple life could emerge very easily if conditions are right and it's the step to complex life that's the hard one.
The transfer of life from one planet to another("panspermia") seems plausible in principle. However, the immense energy released during asteroid impacts makes survival unlikely in many cases, as the very organisms hitching a ride may be destroyed in the process. That said, evidence suggests that microbes shielded deep within rocks could potentially endure the violent stages of ejection, space travel, and planetary re-entry.
Beyond panspermia, I lean toward another perspective:
Life exists because it serves as a natural means of accelerating "entropy" production. In an otherwise relatively stable system, life provides a shortcut, catalyzing processes that dissipate energy gradients far more efficiently than non-living chemistry alone.
At the microbial level, metabolism drives the dissipation of redox gradients, pushing chemical systems toward lower free-energy states. While cells locally maintain order and complexity, their activity increases the overall entropy of their environment. In this sense, life is not a violation of thermodynamic laws but a direct expression of them.
If this is true, life may be extremely common in the universe, arising naturally wherever the right conditions exist to favor energy dissipation.
What may be rare, however, is complex life. Complexity requires not only a lucky balance of stability and change, but also the ability to endure, or even be forced forward, by catastrophic events such as mass extinctions, without wiping out all of it. Earth's active techntonic plates provided yet another means to enable evolution.
Two planets in the "habitable zone" both receiving "ingredients" from the same stream of comets/meteors/cosmic dust, both with what we believe to be environments conducive to life (liquid water, surface temperatures/atmospheric pressures that aren't like Venus..:)
In fact, I'm more surprised that life didn't start independently on both planets at roughly the same time (it could turn out that life did indeed start at the same time on both planets too, just it didn't "take hold" or "last as long" on Mars)
Would you mind elaborating on this? I don’t understand the point. Maybe naively, I would think that evidence of life on mars would increase the probability of life on exoplanets.
If the solution to the Fermi Paradox is that there's a great filter that prevents many advanced civilizations from sticking around long enough to be observable, then we hope that the filter is behind us rather than in front of us.
The more common that life is, the more likely it is in front of us.
I don't even understand why people call it a paradox. A paradox has no obvious solution. This one has many obvious solutions, the most obvious one that the premise is faulty: perhaps life is not common at all.
There is another premise that is faulty: that the answer to "where's everybody" is that "since we see nobody, there is nobody". But for all we know the planets around Alpha Centauri may be teaming with life, and there would be no way for us to detect that. If only 1% of the solar systems in our galaxy host intelligent life, then the number of intelligent life forms would be truly mind-boggling, yet we wouldn't be able to detect a whisper of their presence. For the simple reason that space is also mind-blowingly vast, and all signals decay with the square root of the distance.
That's part of the Great Filter answer to the Fermi paradox. Though, I agree, it's not really a paradox. If the great filter is true, the first filter is life forming at all. We hope that the filter is behind us and that's why intelligent life in the universe seems rare, rather than ahead of us. If life is common, but intelligent life is uncommon, that's concerning because it makes it more likely that the filter is ahead of us. Meaning, something like, once an organism has control over the whole planet there's something that prevents them from going to multiple planets.
I mean, we don't have any other perspective to look through. There is no other point of reference to draw from. We try to compensate by assuming that our system, planet, and species aren't particularly special and are probably about average in terms of supporting life.
We can't know or even begin to guess at what an alien civilization may do or think or how they evolved. Best we can do is assume it's probably somewhat similar to our experience. At least it's based on something factual. Anything else is really just wild speculation.
We pretty much have to assume aliens will be sort of similar to us because we haven't met any. Our experience is the only one we've got, so it's the most reasonable baseline we have. We know that aliens will probably be wildly different from us, but it's so unknowable as to be moot. Do we base our assumptions on Heinlein's writing? Asimov? Douglas Adams? Anything other than what we know from our own experience is just fanciful fiction.
But also you're not supposed to take as read the Fermi paradox, Kardashev scale, or any other ways of thinking about aliens. It's implied that they won't be anything like us. You're not supposed to take it as a literal statement that alien species will be hairless bipeds with a warlike society who think and look like us. You're supposed to follow the assumptions that statistically, we're probably not special as a species and probably any aliens we meet will have evolved along similar lines and probably will be relatable to us. Implicitly we understand that this likely is not true. We just don't know and there aren't really any options that are more reasonable or reliable than basing assumptions on the one and only planet we know that has intelligent life.
This is too pessimistic. We can absolutely "begin to guess" at what an alien civilization might look like or how they might have evolved. Reasonable possibilities are very heavily constrained by information theory, the laws of thermodynamics, the very finite number of elements that make up the universe, chemistry, particle physics, etc. You can appeal to fantasy by dreaming up multi-dimensional energy beings, and of course such things have some tiny but nonzero probability of existing. But you can do the same thing regarding what we might find if we look at some random pond water under a microscope. Maybe we'll find crazy silicon-based life forms, or some phylum we never knew existed, or a microscopic Tyrannosaurus Rex! Maybe. But it's perfectly reasonable to ascribe an extremely small probability to such things based on everything we already know about the universe, and it's reasonable for the same reason to ascribe a very small probability to the existence multi-dimensional energy beings that would completely defy our understanding. For any given alien life form we might find, there's a very high probability (I give it at least 90%) that it would be based on chemical pathways that would make us go "oh, neat", but not go "THIS CHANGES EVERYTHING!"
I'm a complete layman, but I wonder if chemistry on Earth (and rest of our solar system) is also influenced somewhat by the particular properties of our star, its and our magnetospheres etc. and the gas clouds our planets coalesced from.
As in, different stars may encourage slightly different chemical reactions and interactions on their planets.
Like, for example, could it be possible for a planet to form with a naturally highly magnetized mineral in its crust? Would it affect the rest of the chemistry on the planet? Would it cause the ground to interact with its star's magnetic envelope, like our atmosphere within the Auroras does?
Putin and Xi fantasizing about immortality via 3D-printed organs quite starkly illustrated that many adults do not understand the difference between science and science fiction.
The elephant in the room here is that advanced intelligent life as we understand it is some inevitable step in evolution. A random walk of mutations on top of mutations lead us to this and only because the environmental context favored adaptions toward intelligence in the case of our species at the time. This is probably why most sci fi is not written by evolutionary biologists.
Yes, but as time goes to infinity there will eventually be an environment context and mutation path that will result in something that has a similar level of intelligence.
In fact, this makes the preoccupation with humans escaping a Great Filter all the more childish. Even on a single planet the species that will evolve from humans by the time Earth is swallowed by the sun will have less in common with humans than we do now with single cell organisms. Internalize that fact a little bit. Once you realize it is absurd to talk about the human species being preserved as is to the end of time, you will understand the silliness of this obsession. Cause after that point you might as well believe in a deity.
If it makes you feel warm and fuzzy inside, it suffices to hope that only single cell organisms survive the Great Filter, since given enough time it might lead to something that is as intelligent or more intelligent and kind than humans.
Embrace the silliness. The answer to "Why should we humans spread to other planets?" need only be "Why the fuck not?"
That is, unless you want to fund your rocket company. In which case you have to make people believe in a deity.
Er... No that's not a meaningful critique. There's no framework that doesn't assume it's a random process. The point is to find out how likely each step is to occur, randomly.
Even the Kardashev scale is based on the assumption that unfettered economic activity as humans conceived of it in the mid 20th century would be a common enough phenomenon to classify, including shoehorning in our wildest science fiction ideas. Only the most unscrupulous of our species probably want to maximize production of widgets beyond the limits of this planet to the point where a Dyson sphere must be built. Would a Buddhist monk have any interest in that for example, or are their metrics of “productivity” more metaphysical perhaps? Or someone considering preserving a system and not exceeding what it is capable of sustainably offering? How about a blue whale, do they have an increasing energy demand per capita as well?
We’re working off the assumption that life is rare in the universe (and thus a great filter). That is why the stars aren’t covered in life.
If this isn’t true, and life is actually common throughout the galaxy ... then the great filter might still be ahead of us — such as not surviving technological adolescence. Meaning we’re not special, we just haven’t died off yet.
Great filters start with the observation that we have detected no signs of alien technological civilization. The assumption is this means they’re rare.
That doesn’t mean much. If it is actually common and the great filter is passing technological adolescence, then at least one civilisation would need to be around at least a hundred thousand years ago to be detected by us. Then, they would need to survive the great filter. We’ve only been broadcasting for 80 years or so, and any modern technology is probably indistinguishable from noise...
In other words, even if the average technological civilisation lasts 1000 years, the odds of those civilisations overlapping are nearly zero if the great filter is ahead of us. Unless civilisations manage to last much, much longer than 1,000 years (millions of years), the chance that two blips overlap in time and space closely enough to detect each other is basically negligible.
That is why the “life on Mars” point feels ominous:
- If abiogenesis is easy, the filter isn’t there.
- If the filter is later (like surviving technological adolescence), then most civilisations blink out quickly.
Which means overlapping, detectable civilisations would be vanishingly rare, explaining the silence, but also suggesting our future may be short.
Life is pretty robust, civilization is not.
I'd say it's pretty intuitive that the filter is ahead of us - civilizations collapsing has happened multiple times already in the last few millennia. Earth becoming sterile has never happened as far as we know.
Yes, but a civilization collapsing doesn’t kill off an entire species nor (usually) wipe out knowledge completely. Thus it wouldn’t be a great filter. However, perhaps it is pretty common to create a grey goo, or nuke yourself, or whatever. That would be a life ending event.
It's still about what we are able to observe.
If there is a bronze age civilization in the vicinity of betelgeuse, how would we tell?
You'd need a civilization advanced enough to do radio communication - and that has a lot of fragile interdependencies.
Not really. The great filter idea is only one of many proposed solutions to the Fermi paradox. The Dark Forest hypothesis would have the universe filled with life, which is all in deep hiding from an intergalactic civilization hellbent on destroying all other life.
Personally I think the great filter is a dumb idea for precisely the reason you posit. The universe is (probably) infinite, which means there's an infinite probability that we aren't special or alone. Maybe we're the first; the universe is (relatively) pretty young from what we can tell. I doubt that too, but I think it's one of the most plausible explanations.
But really what it comes down to is that in an infinite universe, the probability of anything happening exaxtlt once is infinitely small. It is infinitely more probable that there is or will be other life out there.
Really, out of uncountable trillions of planets in trillions of galaxies across tens of billions of years, how could it be that exactly one planet can produce life? I think it's egotistical navel-gazing in the extreme to assume we're alone.
If you take the beginning of the cosmos to be 1 second ago, the point where other galaxies will be unobservable is in just a few seconds (at T+7–8). We’ve only had civilization for about 700-800 nanoseconds. You could fit hundreds or even thousands of advanced civilizations in there and they’d never know the other existed.
I think the building blocks of life are so common in the universe it might be a case of "easy come, easy go". It wouldn't be surprising if simple life happened anywhere it was given half a chance at all, but one would equally expect that it would die out just as quickly when conditions changed (which they certainly did on Mars).
And of course nothing is ruling out life in the nooks and crannies of Mars.
Presumably the planet became much less geologically active, causing Mars to lose it's magnetic field and thus it's atmosphere, and that caused a mass extinction. If there was life on the surface in the past, I imagine it still exists deep underground or in lava tubes or such.
That actually isn't a hard question to answer. Mars lacks an active core or a magnetosphere, so the atmosphere blew away, freezing the surface and removing almost all of the liquid water.
We have proven that Mars used to have a magnetic field like Earth that protected it from solar radiation. We also know that it does not presently have a magnetic field. At some point in the distant past, Mars's core cooled and solidified, which removes the magnetic field.
The big problem is that the solar wind strips away the atmosphere and water, but that's (probably) not what killed all Martian life. As the magnetic field decreases, more and more harmful radiation reaches the surface. The planet was probably sterilized by radiation long before the atmosphere was lost and the oceans evaporated.
We're pretty sure this is what happened. We've been studying Mars's geology for a long time and we can see evidence for most of this process.
The inner planets have exchanged a lot of material it's possible they also exchanged life. In fact I believe some theories for how life formed rely on it.
They keep pushing back the date of the LUCA - I think it's meant to be 4.2 billion years ago now, a time when Mars was more nurturing than it is now, maybe moreso than Earth at the time? I hope we find out it started on Mars and jumped to Earth, how cool would that be?
I prefer the theory that life is the natural evolution of physical chemical processes given certain conditions. That explains why we think that we’re likely to find life on Neptune. Otherwise it begs the question of why did life start on Mars, and that’s a turtles all the way down kind of situation.
"You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant." -Jeremy England
Life increases entropy and doesn't break 2nd law of thermodynamics.
In addition to one seeding the other, neighboring planets having life also gives support to extra-solar-system panspermia. An advanced civilization could've fired off the "seed" in some vehicles on calculated trajectories to all viable planets, and the Solar System happened to be within the radius of their efforts.
Panspermia is such a juvenile take. It doesn't answer the question at all, just hand-waves it all away with a "because I said so". It's like a religion.
I was never attempting to answer where life came from. It's simply that if Mars and Earth both have/had life, the probability that they came from some common cosmic seeding project in our neighborhood becomes a bit more likely.
Does it seem that way? It happened at least once (but could have happened many times without "taking over"), and certainly one sort of life seemed to successfully out-compete all others. But none of that says single-origin to me.
Early on I would expect a whole lot of "horizontal gene transfer" sort of things to have taken place. So for example in addition to actual horizontal gene transfer, there are mechanisms like one organism enveloping another to eventually become organelles, co-opting products from each other, etc. All of which would act to homogenize life and make certain process ubiquitous.
Finally, there's an outside chance that "there's only one way to do it".
This is about a quarter of the lifetime of the universe ago, and we don’t have any evidence at all that life has ever occurred in any other way. We’ve only really been looking for a hundred years or so, but we’ve not found any “fountain of life” where life is being created, we’ve not found evidence of any type of life that isn’t broadly related.
I absolutely agree that it’s not evidence, but I believe that on balance, it makes more sense to take our working hypothesis to be something that fits the evidence we do have, rather than believing the evidence must exist we just don’t have it.
To be clear, I’m not advocating that we don’t investigate both possibilities, and I wouldn’t put much weight behind my own guess here.
I think single origin event is highly likely because, for example, it's wholly conceivable that a slightly different variant of AUCG (or just one of the molecules) could've emerged and it would have similar characteristics, but not differentiated enough that one would have a very strong selective advantage over the other.
Diversity could exist in harmony and the lack of any diversity is a pretty strong signal that the only extant version is either very rare or the only to ever emerge.
Everything in nature is diverse except RNA/DNA and this fact alone is a sort of evidence.
I'm pretty sure we've checked every lifeform to see if they follow the universal genetic code, and they do. RNA is too fundamental to be a virus infection.
When you should see evidence but don't, "absence of evidence is not evidence of absence" doesn't apply. Otherwise absence becomes unprovable à la Russell's teapot.
Except for that you’d have to have a reasonable belief you know what to look for and where to look.
By comparison, we’ve looked nowhere (Earth is big and mostly inaccessible to humans) and don’t know what we should be looking for, since we don’t have any testable models for the origin of life yet.
And re RNA I was just giving one example of why all life might have it (ie RNA gave an evolutionary advantage so anything without RNA died). There’s all sorts of reasons why we don’t have evidence of multiple origins, not least of which is that we just haven’t looked in the right place and there could easily be life being created from scratch on this planet without even knowing about it. That’s what the entire field of synthetic biology is even about; just doing it in a lab instead of out in nature so that we can understand the conditions better.
Well we aren't sure that it did have a single origin. But also, anything primitive enough to generate randomly is going to be viable food itself for other already existing and more evolved lifeforms, and the conditions for life to start by itself might just be a smorgasbord of energy for existing life forms that could out compete more primitive forms or alter the environmental conditions enough to prevent more life from forming. It might just not be possible for new life forms to arise in a non-sterile environment.
There is absolutely zero evidence for this either way. We assume this is the case, but there's actually no way to ever know for sure. It's completely possible that life emerged and went extinct on this planet many times. Problem is it was so long ago that any fossil evidence has been either buried so far that we can never reach it, or subducted into the mantle and melted down. Absolutely no way to tell.
It was so long ago that it would be buried deep under the ocean and we haven’t even explored well the ocean floor. And fossils wouldn’t really tell you whether there was one origin or another.
And you’re right, assuming those fossils even managed to survive in the first place and not get destroyed. And that’s ignoring that early life would have been microscopic and we wouldn’t really see fossils of that.
Do we have evidence that it stopped? Or just that we don’t know where to look and what to look for?
But even if it did, one clear argument could be that the conditions on Earth when it happened would have been very very different than the earth today. Lots more volcanic activity, lightning storms, and UV radiation. We don’t know the exact conditions needed to create life from inorganic precursors so we don’t have a solid hypothesis of was there multiple origins or a single or is it still happening today.
But given we have the beginnings of evidence of life on Mars, Titan, and Triton, and that it would make sense since we know life must arise naturally out of non-life origins (since there was no life at the Big Bang), I would venture to guess that life is both rare and common. Intelligent life also seems common although less common than life overall (other primates, dolphins, Elephants, ravens/crows, and cephalopods are all quite intelligent). Intelligence + tool use is also not uncommon but rarer (we’ve caught animals on tape using tools). Advanced industrial civilization is the only thing so far that we only have a single existence evidence for - is that unique, can there ever only be one on a planet at a time, or can there only be one ever when conditions are right? Eg we wouldn’t have gotten very far if we were on the planet earlier and didn’t have dinosaur bones to power our industry with - the jump from whale oil to nuclear/photovoltaics/wind turbines seems unlikely but maybe it would happen anyway, just longer.
I don't think there's any reasonable way to call that a likely scenario though. If life did emerge on Mars, why wouldn't it also emerge on Earth? For both planets to have life, the most likely explanation is that it's just common.
Still seems fairly speculative to me. I think it's very likely that there was life given all the water but this is still a ways away from a smoking gun.
You are right: this is indeed no smoking gun (and it isn't hyped to be one). This is more like "we can't rule out life having created this, but there are alternate explanations which have also not been ruled out".
Unfortunately most of the evidence is going to be like this. The chances for better evidence would probably require a sample return of some sort, and even then I wouldn't expect a smoking gun (either way).
Well, not exactly. By my read, the known alternate explanations are very strained, only there for propriety. They don't have a really clear idea how this could have formed abiotically.
This is a silly comparison. The article itself does not contain any phrase like "Clearest Sign Yet of Ancient Life on Mars", it was someone else's decision to give it the clickbait title here.
I'm not an expert on the topic here, but at arm's length this sure seems like responsible scientists doing their best to rigorously study something with some crazy implications. They're not saying "OMG guys there was life on mars!!!!", they're saying from what we can tell with Perseverance's little portable lab these rocks sure seem consistent with a biosignature. Their conclusion is that gee it would be great to have samples brought back to earth for better analysis, which... maybe one day, who knows? Here's what they actually say:
Ultimately, we conclude that analysis of the core sample collected from this unit using high-sensitivity instrumentation on Earth will enable the measurements required to determine the origin of the minerals, organics and textures it contains.
> it was someone else's decision to give it the clickbait title here
Is it notable that the "someone else" is Acting NASA Administrator Sean Duffy referring to the publication with “After a year of review, they have come back and they said, listen, we can’t find another explanation, so this very well could be the clearest sign of life that we’ve ever found on Mars"?
> Is it more clear than the presence of artificial canals on the planet?
…yes. Exhibit A is TFA. Exhibit B is the claim that there is ancient life has a lower burden of proof than that there was an ancient technological civilization.
Just as a side note, this rock has been garnering lot of interest pretty much immediately as it was discovered a year ago. There were also few papers published this spring hinting at biological origin.
I think the notable thing this time is Acting NASA Administrator Sean Duffy referring to the (current) Sep 10th Nature paper by summarizing that “After a year of review, they have come back and they said, listen, we can’t find another explanation, so this very well could be the clearest sign of life that we’ve ever found on Mars, which is incredibly exciting.”
What happened with the organic gases in the upper atmosphere of Venus? I would love it if we find that the life in the universe is ubiquitous. I'm inclined to believe that this should be the case anyway.
Last I heard there was a lot of back and forth about whether that was a real signal. I guess phosphine is easy to mistake for SO2, which, well, Venus has a lot of SO2.
Theories of the origin of life on earth seem to be leaning towards it happening on/in warm damp rocks where RNA like molecules can accumulate in pores. I think there would be problems on Venus - the rocks are too hot, nothing cell like in the atmosphere. But it may be common with a warm damp rock set up which probably was there on Mars.
Organic molecules are fairly common in the solar system on asteroids and the like and probably of non biological origins.
I’ve read that NASA has chosen landing sites that specifically have evidence of ancient rather than more recent or even present day water, with the logic that they do not want to potentially contaminate a site with active martian life with earth based microbes.
Can anyone speak more towards this or identify some of these potential sites that harbor life on mars? Will we ever directly probe somewhere that likely harbors life?
>Will we ever directly probe somewhere that likely harbors life
I recall a few years ago when they believed they had seen liquid water running down a hill they didn't want to move a probe near it for fear of contaminating it.
I'm always amused when sci-fi writers think they're being deep by having ancient humans be aliens from another planet. They just completely forget about the 10 million other species we're so clearly related to? Ancient bacteria on meteorites might explain why DNA looks the same, but it doesn't explain the steady, continuously increasing genetic difference between us and our increasingly distant cousin species. It doesn't explain the dozens of "missing link" fossils between modern humans and ancient primates. If ancient humans came from another planet, then they must have brought billions of other lifeforms from millions of different species with them as well, including millions of fossils that they then buried at the appropriate strata as some sort of prank on future paleontologists, on a giant ark that has completely disappeared. It's such a weak take. The natural record is far too clear for that to make any sense.
Now, Mars / Earth cross-seeding proto-bacteria, billions of years ago, sure. Of course the energy required to kick up a rock to a trajectory where it will hit Mars (or vice versa) is orders of magnitude more than the energy required to vaporize all nearby life, so we've got a pretty big problem already. More likely, they both got seeded when our solar system passed through a cloud of primitive organic proto-life (this is my favorite theory). But eukaryotic transfer? Multi-cellular life transferring between the two worlds? No.
>the energy required to kick up a rock to a trajectory where it will hit Mars (or vice versa) is orders of magnitude more than the energy required to vaporize all nearby life, so we've got a pretty big problem already
Not necessarily. Something like the asteroid that killed the dinosaurs would have created temperatures at the impact point high enough to vapourize everything but probably also chucked a lot of more distant stuff into the sky that didn't get as hot.
Here's a Discovery channel 'simulation' of a large impact chucking stuff up https://youtu.be/bU1QPtOZQZU?t=67 Not sure it's very accurate but it gives an impression of the sort of thing that may have happened.
This. Not all ejecta from asteroid/comet impact is vaporized. Some is launched at escape velocity mostly undisturbed[1]. Mars both cooled first, giving it a leg up to allow biogenesis[2], and has lower escape velocity, making easier for rock chunks to be launched from there to Earth, rather than the reverse. From thousands of impacts and billions of rock chunks ejected from Mars in the early solar system, the successful delivery of a single viable microbe would be enough to seed Earth.
“After a year of review, they have come back and they said, listen, we can’t find another explanation,” said Acting NASA Administrator Sean Duffy. “So this very well could be the clearest sign of life that we’ve ever found on Mars, which is incredibly exciting.” [1]
[1] https://www.cnn.com/2025/09/10/science/nasa-mars-sapphire-fa...
Some interesting stuff from the Nature paper
> The Perseverance rover has explored and sampled igneous and sedimentary rocks within Jezero Crater to characterize early Martian geological processes and habitability and search for potential biosignatures ..... the organic-carbon-bearing mudstones in the Bright Angel formation contain submillimetre-scale nodules and millimetre-scale reaction fronts enriched in ferrous iron phosphate and sulfide minerals, likely vivianite and greigite, respectively.
> Organic matter was detected in the Bright Angel area mudstone targets Cheyava Falls, Walhalla Glades and Apollo Temple by the SHERLOC instrument ..... A striking feature observed in the Cheyava Falls target (and the corresponding Sapphire Canyon core sample), is distinct spots (informally referred to as ‘leopard spots’ by the Mars 2020 Science Team) that have circular to crenulated dark-toned rims and lighter-toned cores
> PIXL XRF analyses of reaction front rims reveal they are enriched in Fe, P and Zn relative to the mudstone they occur in ..... In the reaction front cores, a phase enriched in S-, Fe-, Ni- and Zn was detected
> Given the potential challenges to the null hypothesis, we consider here an alternative biological pathway for the formation of authigenic nodules and reaction fronts. On Earth, vivianite nodules are known to form in fresh water ..... and marine ..... settings as a by-product of low-temperature microbially mediated Fe-reduction reactions.
> In summary, our analysis leads us to conclude that the Bright Angel formation contains textures, chemical and mineral characteristics, and organic signatures that warrant consideration as ‘potential biosignatures’ that is, “a feature that is consistent with biological processes and that, when encountered, challenges the researcher to attribute it either to inanimate or to biological processes, compelling them to gather more data before reaching a conclusion as to the presence or absence of life .....
I had to look up PIXL XRF from this paper - https://arxiv.org/pdf/2402.01544 - it is:
> The Planetary Instrument for X-ray Lithochemistry (PIXL) is an X-ray fluorescence (XRF) spectrometer mounted on the arm of the National Aeronautics and Space Administration’s (NASA) Mars 2020 Perseverance rover (Allwood et al., 2020; Allwood et al., 2021). PIXL delivers a sub-millimeter focused, raster scannable X-ray beam, capable of determining the fine-scale distribution of elements in martian rock and regolith targets. PIXL was conceived following the work by Allwood et al. (2009) that demonstrated how micro-XRF elemental mapping could reveal the fine-textured chemistry of layered rock structures of ~3,450-million-year-old Archean stromatolitic fossils. Their work not only pushed back the accepted earliest possible window for the beginning of life on Earth, but also demonstrated that significant science return might be possible through XRF mapping. PIXL was proposed, selected, and developed to carry out petrologic exploration that provide the paleoenvironmental context required in the search for biosignatures on Mars, analogous to Allwood et al.’s earlier work.
I like your analysis, but, personally, I am struggling with "Absence of data/other possibilities is pointing us to conclusion"
It should (IMO) be reported as, we just don't know (yet), there's some really fascinating things that we cannot explain in any other way, yet, but that doesn't actually mean that we know for sure.
I don't understand this critique at all.
- We know this can happen through process A.
- Really smart people have thought a lot about it and don't see other ways that it reasonably happened in this scenario.
- This is pointing us to the conclusion that it happened through process A.
Is a perfectly reasonable logic chain for a scientific paper and their conclusion literally says "we need more data."
> compelling them to gather more data before reaching a conclusion as to the presence or absence of life”.
What's not to understand - it's precisely the argument theists have put forward for millenia
"We couldn't find anything to show it wasn't a god, so it must be a god"
Calling one group "smart" doesn't change the process or the outcome - the absence of data is not data, it's just that we couldn't yet find the full explanation.
One day we might, it might actually be life, but we don't have that right now, so, actual science demands that we withhold any wild speculation.
No, because theism is missing the first premise. The equivalent would be:
- We have observably seen and reproduced god bringing someone back from the dead - We can find no other explanation for this thing coming back from the dead - It was likely god who brought this thing back from the dead, but we want more data
The first premise has never happened, there is not any equivalence...
"- We know this can happen through process A."
doesn't really apply to theism. "We know worlds can be created by gods" was never really a thing.
We don't actually know.
We suspect that it's rubbish, but we don't have enough evidence to conclusively say one way or another.
Actually (It's too late to edit) we do have this curious thing
Aliens - we claim/recognise that statistically the size of the (at least observable, if not entire) universe and number of habitable planets with all the right ingredients for life that there must be life out there... somewhere
But we don't have an ounce of evidence (neither for nor against)
God(s) - we don't have any evidence one way or the other, atheists just say "It's impossible", theists say "It's the only answer", but, as already mentioned, there isn't any actual evidence that can lead us to a conclusion. (This will be misread as an argument for god(s), but it isn't. And even if it were, there's still a massive step between that and the Abrahamic God being the dude)
Which takes me right back to where this started. The supposition that the features of mars are signatures of life, we don't know at this point, all we actually know is... we haven't found anything else that we can say they are.
The reporting of science is causing so much grief (I mentioned it here https://news.ycombinator.com/item?id=45190544 but was voted down for some reason)
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Kind of bad news for human kind if we find out the life also started in Mars. One Great Filter down.
Anything is possible but unlikely we would find it unless there are buried megaliths signed by humans with graphic pictures. Even on Earth it would be hard to prove we were ever here after half a billion years after we destroy ourselves. It might not even take that long. Most things will rust, decompose, shatter into something resembling dust and many coastal regions will get recycled by plate techtonic movements. Mars has been a dead planet for a long time no magnetosphere, probably how this one will end up at some point.
I think the filter was eukaryogenesis [1]. (Which in turn depends on the endosymbiosis of mitochondria.)
Put simply, I expect the universe is littered with single-celled life. I think multicellular life, on the other hand, is rare.
[1] https://en.m.wikipedia.org/wiki/Eukaryogenesis
Eukaryogenesis != Multicellularity. There are tons of unicellular eukaryotes. Also, multicellularity has evolved a bunch of times, at least in eukaryotes, so I doubt it's that rare.
If your thesis is specifically that oxygen-powered metabolism fueling multicellularity is rare... that wasn't clear. And I'll still say that endosymbiosis being the shortest path to scaling oxygen metabolism is probably Earth happenstance (with a reminder that cellular endosymbiosis is also common). But some critter had to originally evolve oxygen metabolism before being turned into mitochondria. What if that had evolved in a cell prepared to directly take advantage of it?
> There are tons of unicellular eukaryotes
But no multicellular prokaryotes. You're right that eukaryotes can be single celled. But my hypothesis is that multicellular life is rare because eukaryotes are rare.
The second half of my comment still applies then. I think Earth-style eukaryogenesis is probably just one way to achieve the energy budget and complexity needed for complex multicellularity... bearing in mind, of course, that colonial bacteria that collaborate for survival definitely exist, spirulina for instance, stromatolites, and all the gross things that form biofilms.
> Which in turn depends on the endosymbiosis of mitochondria.
Which in turn depends on existing enough atmospheric oxygen for mitochondria to make sense in first place. I believe the filter is atmospheric oxygen. If Earth had more iron in the crust, perhaps the cyanobacteria would never finish oxidizing all of it, and we would be doomed to only host microscopic life forever. Macroscopic life requires high-energy metabolism molecular oxygen allows.
Could that be down to planet size?
We have lots of iron , but most of it sank to the core during the "iron catastrophe" . And Mars is red because of theres so much iron.
It's pretty unlikely that life emerged independently on two planets in adjoining orbits.
The much more reasonable explanation is that life emerged on one planet and transferred over. Earth and Mars aren't particularly close, but they're close enough for material to transfer between them, particularly early in the solar system when there were far more asteroid impacts kicking rocks and dust out into space.
Earth is strange - a billion years of water and chemistry on every grain of sand on every beach. Every combination of temperature, sunlight, wetting and drying as tides slosh things around in every phase.
It's like a bioreactor for creating life. One could argue, it's highly unlikely given all those experiments and all that time, that life would avoid being created.
And Mars? It has a moon too, two of them. Tides as well, lunar and solar. Pretty much the same deal.
Why would you say it's unlikely? For all we know simple life could emerge very easily if conditions are right and it's the step to complex life that's the hard one.
It would be very interesting to get a sample of life on Mars if there is some to see if they have the same chemistry or not.
The transfer of life from one planet to another("panspermia") seems plausible in principle. However, the immense energy released during asteroid impacts makes survival unlikely in many cases, as the very organisms hitching a ride may be destroyed in the process. That said, evidence suggests that microbes shielded deep within rocks could potentially endure the violent stages of ejection, space travel, and planetary re-entry.
Beyond panspermia, I lean toward another perspective:
Life exists because it serves as a natural means of accelerating "entropy" production. In an otherwise relatively stable system, life provides a shortcut, catalyzing processes that dissipate energy gradients far more efficiently than non-living chemistry alone.
At the microbial level, metabolism drives the dissipation of redox gradients, pushing chemical systems toward lower free-energy states. While cells locally maintain order and complexity, their activity increases the overall entropy of their environment. In this sense, life is not a violation of thermodynamic laws but a direct expression of them.
If this is true, life may be extremely common in the universe, arising naturally wherever the right conditions exist to favor energy dissipation.
What may be rare, however, is complex life. Complexity requires not only a lucky balance of stability and change, but also the ability to endure, or even be forced forward, by catastrophic events such as mass extinctions, without wiping out all of it. Earth's active techntonic plates provided yet another means to enable evolution.
My hunch was completely the opposite
Two planets in the "habitable zone" both receiving "ingredients" from the same stream of comets/meteors/cosmic dust, both with what we believe to be environments conducive to life (liquid water, surface temperatures/atmospheric pressures that aren't like Venus..:)
In fact, I'm more surprised that life didn't start independently on both planets at roughly the same time (it could turn out that life did indeed start at the same time on both planets too, just it didn't "take hold" or "last as long" on Mars)
Alternately, an impact to one world caused an upheaval that transferred the blocks to another.
I do think the "galactic seeding" theory is more likely.
Would you mind elaborating on this? I don’t understand the point. Maybe naively, I would think that evidence of life on mars would increase the probability of life on exoplanets.
If the solution to the Fermi Paradox is that there's a great filter that prevents many advanced civilizations from sticking around long enough to be observable, then we hope that the filter is behind us rather than in front of us.
The more common that life is, the more likely it is in front of us.
https://en.wikipedia.org/wiki/Great_Filter
The Fermi "Paradox" is based on so many naive self-referencing assumptions it's ridiculous that it's considered so seriously so often.
I don't even understand why people call it a paradox. A paradox has no obvious solution. This one has many obvious solutions, the most obvious one that the premise is faulty: perhaps life is not common at all.
There is another premise that is faulty: that the answer to "where's everybody" is that "since we see nobody, there is nobody". But for all we know the planets around Alpha Centauri may be teaming with life, and there would be no way for us to detect that. If only 1% of the solar systems in our galaxy host intelligent life, then the number of intelligent life forms would be truly mind-boggling, yet we wouldn't be able to detect a whisper of their presence. For the simple reason that space is also mind-blowingly vast, and all signals decay with the square root of the distance.
That's part of the Great Filter answer to the Fermi paradox. Though, I agree, it's not really a paradox. If the great filter is true, the first filter is life forming at all. We hope that the filter is behind us and that's why intelligent life in the universe seems rare, rather than ahead of us. If life is common, but intelligent life is uncommon, that's concerning because it makes it more likely that the filter is ahead of us. Meaning, something like, once an organism has control over the whole planet there's something that prevents them from going to multiple planets.
I mean, we don't have any other perspective to look through. There is no other point of reference to draw from. We try to compensate by assuming that our system, planet, and species aren't particularly special and are probably about average in terms of supporting life.
We can't know or even begin to guess at what an alien civilization may do or think or how they evolved. Best we can do is assume it's probably somewhat similar to our experience. At least it's based on something factual. Anything else is really just wild speculation.
We pretty much have to assume aliens will be sort of similar to us because we haven't met any. Our experience is the only one we've got, so it's the most reasonable baseline we have. We know that aliens will probably be wildly different from us, but it's so unknowable as to be moot. Do we base our assumptions on Heinlein's writing? Asimov? Douglas Adams? Anything other than what we know from our own experience is just fanciful fiction.
But also you're not supposed to take as read the Fermi paradox, Kardashev scale, or any other ways of thinking about aliens. It's implied that they won't be anything like us. You're not supposed to take it as a literal statement that alien species will be hairless bipeds with a warlike society who think and look like us. You're supposed to follow the assumptions that statistically, we're probably not special as a species and probably any aliens we meet will have evolved along similar lines and probably will be relatable to us. Implicitly we understand that this likely is not true. We just don't know and there aren't really any options that are more reasonable or reliable than basing assumptions on the one and only planet we know that has intelligent life.
This is too pessimistic. We can absolutely "begin to guess" at what an alien civilization might look like or how they might have evolved. Reasonable possibilities are very heavily constrained by information theory, the laws of thermodynamics, the very finite number of elements that make up the universe, chemistry, particle physics, etc. You can appeal to fantasy by dreaming up multi-dimensional energy beings, and of course such things have some tiny but nonzero probability of existing. But you can do the same thing regarding what we might find if we look at some random pond water under a microscope. Maybe we'll find crazy silicon-based life forms, or some phylum we never knew existed, or a microscopic Tyrannosaurus Rex! Maybe. But it's perfectly reasonable to ascribe an extremely small probability to such things based on everything we already know about the universe, and it's reasonable for the same reason to ascribe a very small probability to the existence multi-dimensional energy beings that would completely defy our understanding. For any given alien life form we might find, there's a very high probability (I give it at least 90%) that it would be based on chemical pathways that would make us go "oh, neat", but not go "THIS CHANGES EVERYTHING!"
I'm a complete layman, but I wonder if chemistry on Earth (and rest of our solar system) is also influenced somewhat by the particular properties of our star, its and our magnetospheres etc. and the gas clouds our planets coalesced from.
As in, different stars may encourage slightly different chemical reactions and interactions on their planets.
Like, for example, could it be possible for a planet to form with a naturally highly magnetized mineral in its crust? Would it affect the rest of the chemistry on the planet? Would it cause the ground to interact with its star's magnetic envelope, like our atmosphere within the Auroras does?
Putin and Xi fantasizing about immortality via 3D-printed organs quite starkly illustrated that many adults do not understand the difference between science and science fiction.
The elephant in the room here is that advanced intelligent life as we understand it is some inevitable step in evolution. A random walk of mutations on top of mutations lead us to this and only because the environmental context favored adaptions toward intelligence in the case of our species at the time. This is probably why most sci fi is not written by evolutionary biologists.
Yes, but as time goes to infinity there will eventually be an environment context and mutation path that will result in something that has a similar level of intelligence.
In fact, this makes the preoccupation with humans escaping a Great Filter all the more childish. Even on a single planet the species that will evolve from humans by the time Earth is swallowed by the sun will have less in common with humans than we do now with single cell organisms. Internalize that fact a little bit. Once you realize it is absurd to talk about the human species being preserved as is to the end of time, you will understand the silliness of this obsession. Cause after that point you might as well believe in a deity.
If it makes you feel warm and fuzzy inside, it suffices to hope that only single cell organisms survive the Great Filter, since given enough time it might lead to something that is as intelligent or more intelligent and kind than humans.
Embrace the silliness. The answer to "Why should we humans spread to other planets?" need only be "Why the fuck not?"
That is, unless you want to fund your rocket company. In which case you have to make people believe in a deity.
Er... No that's not a meaningful critique. There's no framework that doesn't assume it's a random process. The point is to find out how likely each step is to occur, randomly.
Even the Kardashev scale is based on the assumption that unfettered economic activity as humans conceived of it in the mid 20th century would be a common enough phenomenon to classify, including shoehorning in our wildest science fiction ideas. Only the most unscrupulous of our species probably want to maximize production of widgets beyond the limits of this planet to the point where a Dyson sphere must be built. Would a Buddhist monk have any interest in that for example, or are their metrics of “productivity” more metaphysical perhaps? Or someone considering preserving a system and not exceeding what it is capable of sustainably offering? How about a blue whale, do they have an increasing energy demand per capita as well?
If the origin is not independent, that doesn't necessarily change the position of the filter.
We’re working off the assumption that life is rare in the universe (and thus a great filter). That is why the stars aren’t covered in life.
If this isn’t true, and life is actually common throughout the galaxy ... then the great filter might still be ahead of us — such as not surviving technological adolescence. Meaning we’re not special, we just haven’t died off yet.
> assumption that life is rare in the universe
Great filters start with the observation that we have detected no signs of alien technological civilization. The assumption is this means they’re rare.
That doesn’t mean much. If it is actually common and the great filter is passing technological adolescence, then at least one civilisation would need to be around at least a hundred thousand years ago to be detected by us. Then, they would need to survive the great filter. We’ve only been broadcasting for 80 years or so, and any modern technology is probably indistinguishable from noise...
In other words, even if the average technological civilisation lasts 1000 years, the odds of those civilisations overlapping are nearly zero if the great filter is ahead of us. Unless civilisations manage to last much, much longer than 1,000 years (millions of years), the chance that two blips overlap in time and space closely enough to detect each other is basically negligible.
That is why the “life on Mars” point feels ominous:
- If abiogenesis is easy, the filter isn’t there.
- If the filter is later (like surviving technological adolescence), then most civilisations blink out quickly.
Which means overlapping, detectable civilisations would be vanishingly rare, explaining the silence, but also suggesting our future may be short.
Life is pretty robust, civilization is not. I'd say it's pretty intuitive that the filter is ahead of us - civilizations collapsing has happened multiple times already in the last few millennia. Earth becoming sterile has never happened as far as we know.
Yes, but a civilization collapsing doesn’t kill off an entire species nor (usually) wipe out knowledge completely. Thus it wouldn’t be a great filter. However, perhaps it is pretty common to create a grey goo, or nuke yourself, or whatever. That would be a life ending event.
It's still about what we are able to observe. If there is a bronze age civilization in the vicinity of betelgeuse, how would we tell? You'd need a civilization advanced enough to do radio communication - and that has a lot of fragile interdependencies.
Or just really hard to detect with existing technology. Combine that with the vastness of the universe, it's not a unreasonable take.
Not really. The great filter idea is only one of many proposed solutions to the Fermi paradox. The Dark Forest hypothesis would have the universe filled with life, which is all in deep hiding from an intergalactic civilization hellbent on destroying all other life.
Personally I think the great filter is a dumb idea for precisely the reason you posit. The universe is (probably) infinite, which means there's an infinite probability that we aren't special or alone. Maybe we're the first; the universe is (relatively) pretty young from what we can tell. I doubt that too, but I think it's one of the most plausible explanations.
But really what it comes down to is that in an infinite universe, the probability of anything happening exaxtlt once is infinitely small. It is infinitely more probable that there is or will be other life out there.
Really, out of uncountable trillions of planets in trillions of galaxies across tens of billions of years, how could it be that exactly one planet can produce life? I think it's egotistical navel-gazing in the extreme to assume we're alone.
If you take the beginning of the cosmos to be 1 second ago, the point where other galaxies will be unobservable is in just a few seconds (at T+7–8). We’ve only had civilization for about 700-800 nanoseconds. You could fit hundreds or even thousands of advanced civilizations in there and they’d never know the other existed.
Oh, we thought that?
We aren’t special. We will die off.
I guess the question is: If there was life on mars, what happened to it?
I think the building blocks of life are so common in the universe it might be a case of "easy come, easy go". It wouldn't be surprising if simple life happened anywhere it was given half a chance at all, but one would equally expect that it would die out just as quickly when conditions changed (which they certainly did on Mars).
And of course nothing is ruling out life in the nooks and crannies of Mars.
Presumably the planet became much less geologically active, causing Mars to lose it's magnetic field and thus it's atmosphere, and that caused a mass extinction. If there was life on the surface in the past, I imagine it still exists deep underground or in lava tubes or such.
That actually isn't a hard question to answer. Mars lacks an active core or a magnetosphere, so the atmosphere blew away, freezing the surface and removing almost all of the liquid water.
We have proven that Mars used to have a magnetic field like Earth that protected it from solar radiation. We also know that it does not presently have a magnetic field. At some point in the distant past, Mars's core cooled and solidified, which removes the magnetic field.
The big problem is that the solar wind strips away the atmosphere and water, but that's (probably) not what killed all Martian life. As the magnetic field decreases, more and more harmful radiation reaches the surface. The planet was probably sterilized by radiation long before the atmosphere was lost and the oceans evaporated.
We're pretty sure this is what happened. We've been studying Mars's geology for a long time and we can see evidence for most of this process.
It may still be there doing it's thing, mostly underground. The surface of Mars is currently very dry for any life we know but there seems to be water underground https://www.bbc.co.uk/news/science-environment-54337779
Likely, when Mars went bad, their planet B was Earth. Nowadays they call themselves Earthlings (AKA us).
The inner planets have exchanged a lot of material it's possible they also exchanged life. In fact I believe some theories for how life formed rely on it.
For all we know, life started on Mars, not here. Hence the "sudden explosion" of life.
They keep pushing back the date of the LUCA - I think it's meant to be 4.2 billion years ago now, a time when Mars was more nurturing than it is now, maybe moreso than Earth at the time? I hope we find out it started on Mars and jumped to Earth, how cool would that be?
I prefer the theory that life is the natural evolution of physical chemical processes given certain conditions. That explains why we think that we’re likely to find life on Neptune. Otherwise it begs the question of why did life start on Mars, and that’s a turtles all the way down kind of situation.
"You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant." -Jeremy England
Life increases entropy and doesn't break 2nd law of thermodynamics.
Actually it's enough to have a sufficiently large amount of hydrogen. No extra light necessary.
In addition to one seeding the other, neighboring planets having life also gives support to extra-solar-system panspermia. An advanced civilization could've fired off the "seed" in some vehicles on calculated trajectories to all viable planets, and the Solar System happened to be within the radius of their efforts.
Panspermia is such a juvenile take. It doesn't answer the question at all, just hand-waves it all away with a "because I said so". It's like a religion.
I was never attempting to answer where life came from. It's simply that if Mars and Earth both have/had life, the probability that they came from some common cosmic seeding project in our neighborhood becomes a bit more likely.
Vs it’s a natural inevitable process when the conditions support it?
Where do the turtles start?
If that is true, then why does it seem that there has been only a single origin event on Earth?
Does it seem that way? It happened at least once (but could have happened many times without "taking over"), and certainly one sort of life seemed to successfully out-compete all others. But none of that says single-origin to me.
Early on I would expect a whole lot of "horizontal gene transfer" sort of things to have taken place. So for example in addition to actual horizontal gene transfer, there are mechanisms like one organism enveloping another to eventually become organelles, co-opting products from each other, etc. All of which would act to homogenize life and make certain process ubiquitous.
Finally, there's an outside chance that "there's only one way to do it".
Absence of evidence is of course not evidence of absence, but all life on earth today seems to be descended from a single organism, 3-4 billion years ago: https://en.m.wikipedia.org/wiki/Last_universal_common_ancest...
This is about a quarter of the lifetime of the universe ago, and we don’t have any evidence at all that life has ever occurred in any other way. We’ve only really been looking for a hundred years or so, but we’ve not found any “fountain of life” where life is being created, we’ve not found evidence of any type of life that isn’t broadly related.
I absolutely agree that it’s not evidence, but I believe that on balance, it makes more sense to take our working hypothesis to be something that fits the evidence we do have, rather than believing the evidence must exist we just don’t have it.
To be clear, I’m not advocating that we don’t investigate both possibilities, and I wouldn’t put much weight behind my own guess here.
I think single origin event is highly likely because, for example, it's wholly conceivable that a slightly different variant of AUCG (or just one of the molecules) could've emerged and it would have similar characteristics, but not differentiated enough that one would have a very strong selective advantage over the other.
Diversity could exist in harmony and the lack of any diversity is a pretty strong signal that the only extant version is either very rare or the only to ever emerge.
Everything in nature is diverse except RNA/DNA and this fact alone is a sort of evidence.
Or the basic life that forms is going to look the same regardless of where it starts on Earth, meaning that you’d never have evidence of two origins.
Or RNA was just a winning virus that infected all other life or killed all competition to make it seem like there was only one origin.
Absence of evidence is not evidence of absence.
I'm pretty sure we've checked every lifeform to see if they follow the universal genetic code, and they do. RNA is too fundamental to be a virus infection.
When you should see evidence but don't, "absence of evidence is not evidence of absence" doesn't apply. Otherwise absence becomes unprovable à la Russell's teapot.
Except for that you’d have to have a reasonable belief you know what to look for and where to look.
By comparison, we’ve looked nowhere (Earth is big and mostly inaccessible to humans) and don’t know what we should be looking for, since we don’t have any testable models for the origin of life yet.
And re RNA I was just giving one example of why all life might have it (ie RNA gave an evolutionary advantage so anything without RNA died). There’s all sorts of reasons why we don’t have evidence of multiple origins, not least of which is that we just haven’t looked in the right place and there could easily be life being created from scratch on this planet without even knowing about it. That’s what the entire field of synthetic biology is even about; just doing it in a lab instead of out in nature so that we can understand the conditions better.
Well we aren't sure that it did have a single origin. But also, anything primitive enough to generate randomly is going to be viable food itself for other already existing and more evolved lifeforms, and the conditions for life to start by itself might just be a smorgasbord of energy for existing life forms that could out compete more primitive forms or alter the environmental conditions enough to prevent more life from forming. It might just not be possible for new life forms to arise in a non-sterile environment.
There is absolutely zero evidence for this either way. We assume this is the case, but there's actually no way to ever know for sure. It's completely possible that life emerged and went extinct on this planet many times. Problem is it was so long ago that any fossil evidence has been either buried so far that we can never reach it, or subducted into the mantle and melted down. Absolutely no way to tell.
It was so long ago that it would be buried deep under the ocean and we haven’t even explored well the ocean floor. And fossils wouldn’t really tell you whether there was one origin or another.
And you’re right, assuming those fossils even managed to survive in the first place and not get destroyed. And that’s ignoring that early life would have been microscopic and we wouldn’t really see fossils of that.
Why did it stop?
Do we have evidence that it stopped? Or just that we don’t know where to look and what to look for?
But even if it did, one clear argument could be that the conditions on Earth when it happened would have been very very different than the earth today. Lots more volcanic activity, lightning storms, and UV radiation. We don’t know the exact conditions needed to create life from inorganic precursors so we don’t have a solid hypothesis of was there multiple origins or a single or is it still happening today.
But given we have the beginnings of evidence of life on Mars, Titan, and Triton, and that it would make sense since we know life must arise naturally out of non-life origins (since there was no life at the Big Bang), I would venture to guess that life is both rare and common. Intelligent life also seems common although less common than life overall (other primates, dolphins, Elephants, ravens/crows, and cephalopods are all quite intelligent). Intelligence + tool use is also not uncommon but rarer (we’ve caught animals on tape using tools). Advanced industrial civilization is the only thing so far that we only have a single existence evidence for - is that unique, can there ever only be one on a planet at a time, or can there only be one ever when conditions are right? Eg we wouldn’t have gotten very far if we were on the planet earlier and didn’t have dinosaur bones to power our industry with - the jump from whale oil to nuclear/photovoltaics/wind turbines seems unlikely but maybe it would happen anyway, just longer.
neptune?
Sorry, I meant a moon of Neptune (Triton). There's also a recent research study suggesting Titan also has life.
I don't think there's any reasonable way to call that a likely scenario though. If life did emerge on Mars, why wouldn't it also emerge on Earth? For both planets to have life, the most likely explanation is that it's just common.
Still seems fairly speculative to me. I think it's very likely that there was life given all the water but this is still a ways away from a smoking gun.
Smoking gun needs sample return, and the current outlook for that mission is not great.
You are right: this is indeed no smoking gun (and it isn't hyped to be one). This is more like "we can't rule out life having created this, but there are alternate explanations which have also not been ruled out".
Unfortunately most of the evidence is going to be like this. The chances for better evidence would probably require a sample return of some sort, and even then I wouldn't expect a smoking gun (either way).
Well, not exactly. By my read, the known alternate explanations are very strained, only there for propriety. They don't have a really clear idea how this could have formed abiotically.
> Clearest sign' yet of ancient life on Mars
Is it more clear than the presence of artificial canals on the planet? Because at the time, the signs were quite clear as well.
https://en.wikipedia.org/wiki/Martian_canals
This is a silly comparison. The article itself does not contain any phrase like "Clearest Sign Yet of Ancient Life on Mars", it was someone else's decision to give it the clickbait title here.
I'm not an expert on the topic here, but at arm's length this sure seems like responsible scientists doing their best to rigorously study something with some crazy implications. They're not saying "OMG guys there was life on mars!!!!", they're saying from what we can tell with Perseverance's little portable lab these rocks sure seem consistent with a biosignature. Their conclusion is that gee it would be great to have samples brought back to earth for better analysis, which... maybe one day, who knows? Here's what they actually say:
> it was someone else's decision to give it the clickbait title here
Is it notable that the "someone else" is Acting NASA Administrator Sean Duffy referring to the publication with “After a year of review, they have come back and they said, listen, we can’t find another explanation, so this very well could be the clearest sign of life that we’ve ever found on Mars"?
> Is it more clear than the presence of artificial canals on the planet?
…yes. Exhibit A is TFA. Exhibit B is the claim that there is ancient life has a lower burden of proof than that there was an ancient technological civilization.
Just as a side note, this rock has been garnering lot of interest pretty much immediately as it was discovered a year ago. There were also few papers published this spring hinting at biological origin.
https://edition.cnn.com/2024/07/26/science/nasa-perseverance...
https://earthsky.org/space/life-on-mars-leopard-spots-poppy-...
So if you feel like you heard this story before, then it's probably one of the previous times this rock made the rounds
I think the notable thing this time is Acting NASA Administrator Sean Duffy referring to the (current) Sep 10th Nature paper by summarizing that “After a year of review, they have come back and they said, listen, we can’t find another explanation, so this very well could be the clearest sign of life that we’ve ever found on Mars, which is incredibly exciting.”
What happened with the organic gases in the upper atmosphere of Venus? I would love it if we find that the life in the universe is ubiquitous. I'm inclined to believe that this should be the case anyway.
Last I heard there was a lot of back and forth about whether that was a real signal. I guess phosphine is easy to mistake for SO2, which, well, Venus has a lot of SO2.
Theories of the origin of life on earth seem to be leaning towards it happening on/in warm damp rocks where RNA like molecules can accumulate in pores. I think there would be problems on Venus - the rocks are too hot, nothing cell like in the atmosphere. But it may be common with a warm damp rock set up which probably was there on Mars.
Organic molecules are fairly common in the solar system on asteroids and the like and probably of non biological origins.
I think the idea with Venus is that life in the atmosphere was a leftover from a more habitable period.
I’ve read that NASA has chosen landing sites that specifically have evidence of ancient rather than more recent or even present day water, with the logic that they do not want to potentially contaminate a site with active martian life with earth based microbes.
Can anyone speak more towards this or identify some of these potential sites that harbor life on mars? Will we ever directly probe somewhere that likely harbors life?
>Will we ever directly probe somewhere that likely harbors life
I recall a few years ago when they believed they had seen liquid water running down a hill they didn't want to move a probe near it for fear of contaminating it.
> NASA has chosen landing sites that specifically have evidence of ancient rather than more recent or even present day water
Source?
https://nap.nationalacademies.org/read/11937/chapter/9
NASA Sharing Details of New Perseverance Mars Rover Finding [Video] https://youtu.be/-StZggK4hhA?t=1041
(see https://news.ycombinator.com/edit?id=45205855)
Related comics: https://www.badspacecomics.com/post/apostles-of-mercy
If we eventually find martian microbes, or at least their fossils, my bet is that we'll find them to be related to us.
I'm always amused when sci-fi writers think they're being deep by having ancient humans be aliens from another planet. They just completely forget about the 10 million other species we're so clearly related to? Ancient bacteria on meteorites might explain why DNA looks the same, but it doesn't explain the steady, continuously increasing genetic difference between us and our increasingly distant cousin species. It doesn't explain the dozens of "missing link" fossils between modern humans and ancient primates. If ancient humans came from another planet, then they must have brought billions of other lifeforms from millions of different species with them as well, including millions of fossils that they then buried at the appropriate strata as some sort of prank on future paleontologists, on a giant ark that has completely disappeared. It's such a weak take. The natural record is far too clear for that to make any sense.
Now, Mars / Earth cross-seeding proto-bacteria, billions of years ago, sure. Of course the energy required to kick up a rock to a trajectory where it will hit Mars (or vice versa) is orders of magnitude more than the energy required to vaporize all nearby life, so we've got a pretty big problem already. More likely, they both got seeded when our solar system passed through a cloud of primitive organic proto-life (this is my favorite theory). But eukaryotic transfer? Multi-cellular life transferring between the two worlds? No.
>the energy required to kick up a rock to a trajectory where it will hit Mars (or vice versa) is orders of magnitude more than the energy required to vaporize all nearby life, so we've got a pretty big problem already
Not necessarily. Something like the asteroid that killed the dinosaurs would have created temperatures at the impact point high enough to vapourize everything but probably also chucked a lot of more distant stuff into the sky that didn't get as hot.
Here's a Discovery channel 'simulation' of a large impact chucking stuff up https://youtu.be/bU1QPtOZQZU?t=67 Not sure it's very accurate but it gives an impression of the sort of thing that may have happened.
This. Not all ejecta from asteroid/comet impact is vaporized. Some is launched at escape velocity mostly undisturbed[1]. Mars both cooled first, giving it a leg up to allow biogenesis[2], and has lower escape velocity, making easier for rock chunks to be launched from there to Earth, rather than the reverse. From thousands of impacts and billions of rock chunks ejected from Mars in the early solar system, the successful delivery of a single viable microbe would be enough to seed Earth.
[1] https://fire.biol.wwu.edu/cmoyer/zztemp_fire/biol345_F10/pap...
[2] https://arxiv.org/pdf/astro-ph/0403049
>Some is launched at escape velocity mostly undisturbed[1].
Does that mean there could be bit's of actual dinosaurs floating out in space?
I have no idea.
I didn't think of it that way around. So maybe we are all Martians really.
Is this like a banded iron formation?
Similar idea I think: organics depositing iron
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