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What If Life Did Not Originate on Earth?

300 points by laurex 7y ago

wahern 7y ago
> The reason this news registered among scientists is that methane is often a sign of life; although the gas can be produced by various chemical reactions, most of it comes from animate beings. This doesn't sound right at all. There are literally lakes of methane on Titan. The atmospheres of Jupiter, Saturn, Uranus, and Neptune all contain significant methane--it's what makes Uranus and Neptune blue. Pluto has methane ice. IIRC from the original reporting, some recent research suggested that there's more methane than contemporary geological models of Mars predict. Which likely says more about the [non-biological] deficiencies in those models than it does the likelihood of life. I'm not an astro-anything, so feel free to correct me. But it's telling that the interviewee never comes close to confirming the reporter's claims; they're simply quoted as saying, "I think probably many people would like the idea of methanogens on Mars", and "the idea that they might be related to methanogens on Earth is not crazy." Isaac Chotiner is a name I'll try to remember so I can avoid his articles.
- BurningFrog 7y ago
  There is ancient methane in those places. But something on Mars is producing methane. Methane breaks down pretty fast in Mars' atmosphere, and yet it reappears there occasionally. That can certainly have non life explanations. But they're fairly exotic.
- jvanderbot 7y ago
  IIRC, methane should not persist on Mars, and theres not been a global phenomenon detected that can explain its occasional detection. Therefore, transient detections are considered indicators of possible life, since nothing else seems to explain it. It's not that it's rare everywhere, it's that it's rare on Mars.
- mturmon 7y ago
  The author (Chotiner) has indeed made a mis-statement about the state of knowledge on planetary CH4, but that doesn't pertain directly to most of the article's content, which is about DNA/RNA. As you point out, the state of Mars CH4 is quite complex and extremely controversial, with 3 different measurements (Curiosity + 2 orbiters), low concentrations observed (~10 ppb) and multiple physical processes going on. Here's a pretty good recent summary: https://www.abc.net.au/news/science/2019-04-02/mars-express-confirms-methane-spike-detected-by-curiosity-rover/10563160 https://www.abc.net.au/news/science/2019-04-02/mars-express-... The DNA-sensing instrument that's being prototyped is here: http://setg.mit.edu http://setg.mit.edu
api 7y ago
I've wondered for years if maybe the idea of life originating on Earth might be the final geocentrism.
- perl4ever 7y ago
  We have a seemingly pretty firm age for the universe of 13.7 billion years; earth is 4.5 billion years old, and life on earth is at least 3.5 billion years old. So I think the step of going from nothing to the first single celled life is implausibly large to happen in a few million to a billion years, and to me, Occam's razor would imply that something necessary was developing during the previous 9 billion years, such as the development of chemotrophs underground in deep space.
- natechols 7y ago
  We haven't yet collected evidence that says terrestrial life originating on Earth is impossible or even unlikely, nor has anyone produced an alternative explanation that doesn't involve introducing additional external factors. It may indeed turn out to be incorrect (although I wouldn't be on it), but it's in no way comparable to geocentrism which simply couldn't be reconciled with experimental observation.
  - perl4ever 7y ago
    If you lived on Long Island, and didn't know where humans came from, but you knew about how big the earth was, would it be rational or in accordance with Occam's razor to assume homo sapiens originated in your vicinity? Most people would in fact be wrong if they even assumed humans originated on their continent. I feel like people get sidetracked into talking about evidence, when the issue is that life originating on Earth should not be the default assumption. I feel like someone more lucid than me could make a good Bayesian sort of argument.
    - Avshalom 7y ago
      It's not exactly the default assumption though. Historically the default is that life was magicked into existence or came here from a previous world or some other creation story. The current abiogenisis story of molecules->proteins->cells->Life is relatively recent. The other thing is that because we have a fairly... ?linear record of evolution: if life did originate somewhere else it got to Earth in something like prokaryotic single cell form 3.5 billion years ago. Which means we can't use the idea of panspermia to tell us anything. It's neither predictive or explanatory. It tells us nothing of how or where life did originate or how life got started on Earth or what or where we should look for or expect in the rest of the Universe. The current theory suggests life could pop up extremely quickly, which itself already implies life is likely to exist in the rest of universe on some level so panspermia doesn't even mean anything with regards to how likely life is anywhere else.
reggieband 7y ago
What I find more interesting is the potential frequency with which new life from origins other than earth has been mixed together with what is here. A lot of stuff falls into our atmosphere and I doubt we know where all of it comes from. I commented today on a bit of dermatological discussion where they claim our skin has a biome of bacteria. This is in addition to the gut biome that is starting to look like it contributes to a wide array of human health issues. Part of me wonders how much of those biomes (e.g. how many bacteria within that biome) are from sources outside our planet.
- rossdavidh 7y ago
  Well, if they did, then the fact that the basic DNA machinery is the same implies that we and the alien bacteria had a common ancestor somewhere back there.
  - reggieband 7y ago
    > implies that we and the alien bacteria had a common ancestor My intuition suggests that wouldn't be necessary. For example, if I saw a snowflake like structure on another planet I wouldn't be surprised since that kind of structure is a result of the physical properties of the elements involved. It could be the case DNA is very similar in that respect, a mathematical necessity given the properties of hydro-carbons. I suspect the science on that issue isn't settled.
    - perl4ever 7y ago
      I'm thinking someone may have proved by construction that DNA isn't the only possible code. Didn't someone make "artificial" DNA by substituting something chemically for some of it?
      - reggieband 7y ago
        That sounds slightly different than what I mean. You appear to be saying: "It is possible something DNA-like could be constructed from different materials in different codes and it would still be viable". I was saying: "It is possible hydrogen, carbon, oxygen, etc. will form into DNA as long as suitable conditions exist and this is common enough occurrence that multiple sources of DNA independently developed across the galaxy/universe". I only say this to assert that the appearance of DNA from a source other than Earth should not necessarily imply a common ancestor.
derekp7 7y ago
Even though we have only one datapoint, I wonder how much can be inferred from this planet's life characteristics. First, life came about rather shortly after the planet was able to sustain it. So this timing is either very unlikely, or biogenesis has a high probability of happening, or the initial life got seeded from off planet (from a very rare initial phenomenon). Second, all the biosignatures from all forms of life are similar. For example, corality (left handed versus right handed molecules) is the same in all life examples we had. So that means that biogenesis happened only once. Otherwise we would have multiple unrelated examples (yes, there is the possibility that one form "ate everything else", but we have all kinds of variety instead of only one organism becoming dominate). So if biogenesis happened only once (for all of our bio examples), then it is either a rare event that just happened to occur very shortly after the planet cooled, or it happened sometime before Earth was hospitable for life and elsewhere in the universe. Does any of this make sense? Or am I reading too much into the tea leaves?
- inflatableDodo 7y ago
  >Even though we have only one datapoint I think we can wrangle a few more datapoints if we are creative with perspective, for example, we have extremely good evidence to suggest that the planet Mars is currently inhabited by alien robots.
- infectoid 7y ago
  Your tea leaves are sound. I think this is why those of us interested in this are very much hanging out for results from our explorations of Mars. It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. What are the chances? On the positive side Mars had pretty much all the ingredients for life (chemically) and had a long enough period for at least something intersting to develop. On the negative side, the environment was still different to ours (gravity, climate, whether, etc). We still aren't clear on what conditions need to met for like to get going. This is why both positive or negative results on Mars are exciting. My favourite theory is that life actually takes ages to get started so much so that it started on Mars and finished on Earth (from Mars being impacted and debris making it to Earth). Kind of like a passing of the torch. Mars: "Crap. I'm dying. Hey Earth, can you take this thing I've been working on?" Earth: "Yep. No worries. I got this. Will try to send some back in a few billions years. Take care."
kleer001 7y ago
What if life is a fundamental property of a sufficiently complex universe and a stable energy gradient? That's where I'd put my money.
- keithwhor 7y ago
  This right here. Provided a body that can retain and emit heat from a star, it intuitively makes sense that given correct conditions the warm body would trend towards more complex head dissipation mechanisms. Life is just a more complex — and sustainable — exothermic reaction than standard oxidative mechanisms (fire). By the way: this isn't a new concept. Jeremy England at MIT has been espousing the concept for a while [0]. [0] https://www.quantamagazine.org/first-support-for-a-physics-theory-of-life-20170726/ https://www.quantamagazine.org/first-support-for-a-physics-t...
- Koshkin 7y ago
  Hm. Also, money could be a fundamental property of a sufficiently complex life.
  - kleer001 7y ago
    I understand the downvote, but I also agree with the statement. IMHO money, markets, even democracy seem to me to follow directly from the challenges of living in a complex society which follows from the benefits of working at large scales. They even seem to me to be simply abstracted versions of more naturally evolved systems baked into life on Earth a billion years ago, i.e. ATP metabolism and multi-cellular life
  - asfarley 7y ago
    The real question is - are iPhones a fundamental property of sufficiently complex life? Will the first alien culture we encounter have a 2D vision & touch-based thin interface to their global (galatic) network?
- not_kurt_godel 7y ago
  Seems like a bad bet given that from the evidence we have so far, life is an unbelievable statistical anomaly. There's no reason why life had to have evolve on Earth or survive long-term; it is sheer luck that we haven't been hit by gamma ray bursts or a supernova or any one of the other nasty, super-deadly things the cosmos could throw at us.
hirundo 7y ago
Maybe we could test this someday with petri dishes in orbit. Outfit satellites with catch basins that funnel into various potentially habitable pods and see what grows. Park them in a lagrange point for better isolation. But if panspermia is true such critters in the cosmic wind would be cousins of life on earth, and it would be difficult (impossible?) to distinguish an alien microbe from domestic contamination. If it's false we see nothing, and wonder if it's because space is sterile or we're just not yet offering it the right primeval soup.
- bdamm 7y ago
  Panspermia doesn’t only work (if it works) by microbes floating in space. Rather the idea is that microbes are embedded and somewhat protected in asteroids which then land somewhere habitable. The occasional close brushes between stars and their asteroid clouds provide the medium where microbes could be transferred between stars quickly enough to launch and land before the radiation destroys any hope of survival (like 20 thousand years.)
- sjg007 7y ago
  Cosmic rays sterilize everything in time, so it seems unlikely we would find anything.
mellosouls 7y ago
Minor fun fact: Fred Hoyle, possibly the most public proponent of Panspermia in the last few decades, also coined the phrase "Big Bang theory" to dismiss an alternative to his preferred Steady State theory of the universe. Sometime champion of arch positions, he was once quoted as saying "it is better to be interesting and wrong than boring and right". https://en.m.wikipedia.org/wiki/Fred_Hoyle https://en.m.wikipedia.org/wiki/Fred_Hoyle
- throwaway2048 7y ago
  It is a pretty out there theory, but at one point the universe would have cooled enough from the very hot big bang origins to allow liquid water to exist everywhere, but not cooled sufficiently to cause everything to freeze. If any rocky planets existed at the time, maybe that was the origin of life which was much more able to spread widely due to the small size of the early universe. https://arxiv.org/abs/1312.0613 https://arxiv.org/abs/1312.0613
  - minitoar 7y ago
    This just sounds like a cool sci-fi setting/backstory.
- RachelF 7y ago
  Hoyle was great man, who said what he thought. His outspoken character probably cost him a Nobel Prize, though.
opportune 7y ago
Methane is not nearly as good a signal to look for life as larger organic molecules are. Methane can easily be created by abiotic processes and remain stable when not directly exposed to radiation or oxidizers indefinitely: this happens on earth, and we do have oxidizers everywhere. Larger organic molecules are less likely to have abiotic origins by any known process and are almost always much less stable. On earth you can test whether methane has organic or abiotic origins by testing its isotopes. We can do this because we understand decently well how the geologic past of earth unfolded. We could probably do a similar thing for mars >The Earth is 4.5 billion years old. And the universe, at least based on estimates from the Big Bang, is something like fourteen billion years. So, if life evolved somewhere else, that buys you about ten billion years of time. Obviously I'm no expert, but you have to keep in mind, it took a decent amount of time for non-violent stars to become the norm / stellar neighborhoods to calm down and for overall metallicity to become significant enough to allow for the formation of terrestrial planets.
- sandworm101 7y ago
  >> and for overall metallicity to become significant enough to allow for the formation of terrestrial planets. You don't need much metallicity before terrestrial planets start forming. They would certainly be rarer in the early universe, but stars filter material very quickly (pushing light stuff further away, stripping new planets to their dense cores). So even with 10% of today's metallicity, there would still be plenty of terrestrial planets. (lol. My spellcheck corrects "metallicity" to "Metallica".)
  - irrational 7y ago
    So even with 10% of today's Metallica, there would still be plenty of terrestrial planets.
    - ivolimmen 7y ago
      Username checks out
- tlb 7y ago
gojomo 7y ago
The idea life emerged long before Earth, and may be widespread in the universe, is fairly old: https://en.wikipedia.org/wiki/Panspermia https://en.wikipedia.org/wiki/Panspermia I suspect that a formal, anonymous survey of astrobiologists would find that the idea is far more prevalent among experts than Ruvkin's estimate that "one per cent would buy into the idea of life spreading the way I’m sort of promoting it". It's just risky to express, for cultural reasons, until there's tangible proof. Many scientists are temperamentally reluctant to speculate without conclusive evidence, especially given the penchant of the press to sensationalize any such theories. It'd raise difficult questions about our place in the universe, and possibly popular fears. Thinking science had already settled on a consensus that simple life is everywhere might even paradoxically reduce funding for new missions to test the idea. After all, there have been tantalizing hints of life-processes on Mars going back to the Viking lander experiments of the 1970s – and yet we still can't seem to send a lab package that'd definitively answer the question! But the hope of figuring it out motivates new missions. (As should be clear, I'm strongly in Ruvkin's camp – and regularly comment to that effect here on HN: https://hn.algolia.com/?query=gojomo%20panspermia&sort=byDate&prefix=false&page=0&dateRange=all&type=comment https://hn.algolia.com/?query=gojomo%20panspermia&sort=byDat... )
- deleted 7y ago
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dboreham 7y ago
Wasn't there a movie about this?
Causality1 7y ago
>It just seems like, once it evolves, it spreads. Hence why I draw exactly the opposite conclusion. It's my thinking that if life existed throughout our 13 billion year old galaxy it would have evolved to saoience and consumed all available resources long before the rise of humanity. The fact our planet hasn't been strip mined or colonized is, absent hard data, good reason to believe we're alone.
- roca 7y ago
  There's a big difference between microbial life and intelligent life. Bostrom and others have argued that, based on how long evolutionary milestones took on Earth, the "difficult step" is actually complex multicellular life.
  - Causality1 7y ago
    The timeline implies that but experimentation indicates it may not have been that hard. https://www.nature.com/articles/s41598-019-39558-8 https://www.nature.com/articles/s41598-019-39558-8 https://www.sciencemag.org/news/2018/06/momentous-transition-multicellular-life-may-not-have-been-so-hard-after-all https://www.sciencemag.org/news/2018/06/momentous-transition...
    - roca 7y ago
      That's interesting. I agree with your conclusion that Fermi's paradox simply means there is no other intelligent life, though I think the jury's still out as to where the filter is.
      - Causality1 7y ago
        Indeed. There's quite a lot of debate surrounding it and a couple of mathematicians arguing we haven't hit the filter yet, but I maintain hope we're past it. It wounds my sci-fi loving heart to say this but humanity is probably better off alone.
  - DoctorBit 7y ago
Darthy 7y ago
There was this interesting article posted here some time ago that plotted the complexity of life found on earth vs time, and by using the right methodology and logarithmic scales, it arrived at a nice linear line over many data points and several billions of years. And the line converged to a 0 point, but that point was a few billion years before earth was created 4.5 billion years ago, adding more credibility to a panspermia theory. Can anybody remember that article and its url?
- Darthy 7y ago
  Update: found it. Apparently the theory is contentious, with accusations that they cherry-picked their data points. Discussion: https://news.ycombinator.com/item?id=5580334 https://news.ycombinator.com/item?id=5580334
- drewrv 7y ago
  Is this it? https://www.technologyreview.com/s/513781/moores-law-and-the-origin-of-life/ https://www.technologyreview.com/s/513781/moores-law-and-the... (I found it elsewhere among these comments)
stewbrew 7y ago
"It could be that I’ve never had a religious thought in my life." The very idea that life has to originate from somewhere/somewhat and cannot just happen sounds like a secular reformulation of a typically religious statement.
tychomaz 7y ago
James Tour: The Mystery of the Origin of Life https://www.youtube.com/watch?v=zU7Lww-sBPg https://www.youtube.com/watch?v=zU7Lww-sBPg
ShamelessC 7y ago
I wish he had posited a theory for how life from Mars would have even gotten here. Some comments have said an asteroid hit Mars and then redirected to Earth with early life on it? Is that possible/likely?
- AgentME 7y ago
  Yes, it happens. There are about 200 meteorites found on Earth that are known to have come from Mars: https://en.wikipedia.org/wiki/Martian_meteorite https://en.wikipedia.org/wiki/Martian_meteorite
deleted 7y ago
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apo 7y ago
The question of where life originated will have no good answer until we figure out how to create life from basic components. We still don't know how to do that yet. Yes, Urey and Miller showed that you could get simple organic molecules by passing an electric charge through gasses thought to be present around the early Earth. But going from low molecular weight inputs to life is a vastly different problem. You could think of it as the most complicated bootstrapping problem in the universe. Nobody has managed to do it in the lab, either. What can't be built from scratch can't be understood very well, and therein lies the problem. If we had a stepwise procedure for building a self-replicating, self-feeding organism of any level of complexity from base components, we would know exactly what to look for. Until then, the idea of sending a DNA amplifier to Mars isn't a bad fallback position.
- dvfjsdhgfv 7y ago
  If we succeed, it would be the most important breakthrough in the history of humanity, and would have very deep existential implications. It wouldn't definitely rule out a supreme being as the creator of the universe we live in, but it would make the gap between us and that being much smaller than millions of people on earth believe now.
  - acqq 7y ago
    > would have very deep existential implications. I doubt that. > It wouldn't definitely rule out a supreme being as the creator of the universe we live in Yes, that's exactly what the believers will tell you even then. Think about it: the science knows today that every atom in our bodies is either produced 13.8 billion years ago (is it is H2) or in the explosion of some star. It's true for every element that you learn in the chemistry class. We know that the Earth is 4.7 billion years old. And we already know that humans share 99% percent of the DNA with chimps. And that 0.006 billion years ago on the Earth neither humans nor chimps existed, but their common ancestor. Do people who believe in a "miracle" divine intervention that supposedly happened only some 0.000002 billion years ago (or even only 0.0000014 billion years ago) when only at that point their deity became involved with the believers, do these people in anyway feel affected by all that? No. Compared to what we know today, their religious "messages from the deity" obviously prove that they were written by plain humans of older times, because these messages don't contain any knowledge we have today, but instead the "eternal" truths like "at the end of the day the Sun sets in the muddy pond" or that the Earth's sky is a solid dome: https://en.wikipedia.org/wiki/Firmament#Biblical_use https://en.wikipedia.org/wiki/Firmament#Biblical_use Do the believers feel affected by that? No.
rectangletangle 7y ago
An interesting phenomenon I rarely see brought up in support of panspermia is the apparent universality of the genetic code. The fact that all known life shares a common genetic structure implies a common ancestor. The lack of competing genetic codes could be interpreted to imply that life only started on earth once, or that it only made it to earth once. Natural selection is a constant force, presumably new genetic codes could offer an advantage, e.g., robustness against damaging mutation, resulting in multiple competing genetic codes. The notion of abiogenesis occurring only once on earth seems improbable considering complex organs like eyes have evolved independently several different times. Or the fact that convergent evolution "reinvents" similar species in response to similar selective pressures. Selective pressures constantly "push" life in the same directions, so it would seem that whatever forces gave rise to life would have happened so repeatedly, but there doesn't seem to be any evidence for that. A clean explanation for this would be that life didn't start on earth, and earth may have never had the right conditions to originate life, hence no competing genetic codes. But it was still hospitable enough to maintain life, so one universal genetic code flourishes with no emergent competition.
- rjurney 7y ago
  Yeah, it seems to have been incredibly unlikely. It took a long time.
- hdfbdtbcdg 7y ago
  Or life started multiple times but the results of one of those times outcompeted all the others.
  - rectangletangle 7y ago
    This is true, but if that did happen presumably we could find some evidence for it, since it would be a relatively common occurrence during the period where earth was capable of abiogenesis. Because if it occurred at least twice, it probably happened many more times. The counterpoint is that the fossil record is very incomplete when going that far back, seeing as tectonic subduction literally wipes the slate clean.
edoo 7y ago
Given the complexity of DNA I think it is near obvious life did not originate on earth. If you assume it did not originate on earth that gives you at least another 10 billion years to work with.
- gomijacogeo 7y ago
  No, it really doesn't; it took a few generations of stars exploding and slamming into each other to make all those heavy elements we kinda consider important. You might be able to move it back another 3-4 billion years, which is admittedly a good long time. But really there's nothing yet that even remotely necessitates an extra-terrestrial origin for life. The problem is that, each time there was a "winner" in the very earliest more-chemistry-than-life arms-races, it essentially obliterated all record of what the competition looked like. It's not until pretty late in the game that no one new strategy obliterated all its peers - at that point we got the biological domains (prokaryotes and eukaryotes (which subsumed other prokaryotes as mitochondria and chloroplasts)) and viruses. From then on, the arms-races have been at higher levels of abstraction and the fight over the basics of biochemistry is 'settled'.
gremlinsinc 7y ago
What if we began a 'seeding' experiment, suppose there could be more life but isn't because life doesn't spread well in the vacuum of space. What if we began sending bacteria and other micro-organisms to potentially habitable planets via tiny spacecrafts. If we were to seed as many planets as we could possibly find, then eventually (in a million years or so), this entire galaxy could be teaming with life and the fermi paradox will be refuted as there will be no way not to see the life that is out there. We may still not be able to traverse the stars by that time at least not without generation ships but our descendents could at least wave from afar and maybe communicate across vast distances with intelligent life that we today helped seed/create.
- titzer 7y ago
  I'm not really on board with the idea of just blindly infecting all habitable planets with Earth life. We should look but don't touch until we have some clue what the heck we are doing and why.
DanielBMarkham 7y ago
Based on nothing but faith and an irreducible cynicism, my money says we end up going full circle, from "Earth is alone in the universe in regards to life" to "Life is a fungus, found anywhere the most basic of conditions are met" (at least over periods of millions of years at stellar scales) People forget that this discussion is not necessarily related to life. When various European explorers went out, in many cases they didn't know what to expect. When they met strange peoples, most of them refused to believe these were actually human. It takes a good long while for humans to recognize other lifeforms like us. We naturally think that we're unique, that wherever we call home is special and the center of things. Combine that with galactic distances and it might be a good while before we realize that the universe is actually full of aliens that look just like humans only with bumpy heads (Obligatory Star Trek joke)
wycy 7y ago
My biology knowledge is admittedly weak, but a question for those who might know: a lot of the discussion here is about how we only know of "life" based on nucleic acids (DNA). However, prions seem to replicate themselves without the help of nucleic acids. Could this in some way be seen as a competing form of "life"?
- ecoled_ame 7y ago
  Prions don't synthesize themselves, they just self-assemble. RNA can encode it's own information while also catalyzing self-replication.
DebtDeflation 7y ago
It always seemed to me that the biggest argument against panspermia is the relative hostility to "life" of space versus a planet like Earth. The heliosphere protects the solar system from a significant amount of interstellar cosmic rays and x-rays, Earth's magnetosphere offers additional protection, and our atmosphere, particularly the ozone layer, offers additional protection while also protecting against UV and high energy particles from the Sun. Ionizing radiation and short wavelength EM radiation are destructive to life and really the persistence of any large complex molecules. Combine that with the vacuum of space and temperatures barely above absolute zero and life originating via panspermia seems significantly less likely than originating natively on Earth.
- koboll 7y ago
  Not to mention atmospheric entry and asteroid impact.
- mywittyname 7y ago
  I'd say the biggest argument against panspermia is that the organisms responsible for it need to be successful locally and universally, at the same time. Reproduction is expensive and intrastellar reproduction is incredibly low yield. So organisms would need to have evolved to both capture an entire ecosystem AND waste a bunch of energy blowing their seed into the solar system. The idea just doesn't jibe with my understanding of evolution.
pfdietz 7y ago
I have wondered if panspermia could have occurred in the Sun's birth cluster. This cluster would have had a very high density of stars, with gas around them to slow and capture material ejected from their neighbor systems. And the asteroids in orbit around these stars would have still be warm enough to have liquid water in them, so life could potentially have been seeded in a wide variety of environments. This possibility, if true, means SETI might be worthwhile even if the actual origin of life is astronomically rare, much less than once per observable volume of the universe. SETI would look at the other stars that were in that cluster. Even if the rest of the universe were devoid of life, they (like the continents of Earth, or planets in our solar system) could share the same origin event. This scenario might also explain why life apparently originated so early in the history of our solar system: this sort of natal panspermia would statistically amplify origin-of-life events that happened early on, by multiplying the number of systems they'd affect. This amplification would occur even if OoL was extremely rare.
tempodox 7y ago
And what if life did originate on Earth? That's one of those hypothetical questions where the answer wouldn't make any practical difference, if we even had an answer. If and when we find extraterrestrial life, maybe we can come up with questions where the answers would be of practical value.
newsgremlin 7y ago
Don't know if anyone has ever considered this (ignoring gross simplifications), but as depictions of aliens are typically conceptualized from creatures we see on earth. Is it possible that if we are the only living creatures that have (yet) gained heightened consciousness, then spreading the DNA of all life on earth across the universe in a similar fashion to how our microbial life arrived on earth is how we ensure that life truly goes on if we fail?
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AILove 7y ago
What if this entire universe is an organism?
Grustaf 7y ago
“...what if it started here and then spread elsewhere? And so we found some sort of DNA on Mars, but that’s because it spread there from Earth. Is that possible? Yeah, but that sort of places us at the center of the universe, and all the force of history is to say, “Don’t think of us as the center. We’re nothing.”” What kind of argument is that? Sounds like some kind of anti-geocentric dogma, not an actual argument.
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300 points by laurex 7y ago

> The reason this news registered among scientists is that methane is often a sign of life; although the gas can be produced by various chemical reactions, most of it comes from animate beings. This doesn't sound right at all. There are literally lakes of methane on Titan. The atmospheres of Jupiter, Saturn, Uranus, and Neptune all contain significant methane--it's what makes Uranus and Neptune blue. Pluto has methane ice. IIRC from the original reporting, some recent research suggested that there's more methane than contemporary geological models of Mars predict. Which likely says more about the [non-biological] deficiencies in those models than it does the likelihood of life. I'm not an astro-anything, so feel free to correct me. But it's telling that the interviewee never comes close to confirming the reporter's claims; they're simply quoted as saying, "I think probably many people would like the idea of methanogens on Mars", and "the idea that they might be related to methanogens on Earth is not crazy." Isaac Chotiner is a name I'll try to remember so I can avoid his articles.

BurningFrog 7y ago
There is ancient methane in those places. But something on Mars is producing methane. Methane breaks down pretty fast in Mars' atmosphere, and yet it reappears there occasionally. That can certainly have non life explanations. But they're fairly exotic.
jvanderbot 7y ago
IIRC, methane should not persist on Mars, and theres not been a global phenomenon detected that can explain its occasional detection. Therefore, transient detections are considered indicators of possible life, since nothing else seems to explain it. It's not that it's rare everywhere, it's that it's rare on Mars.
mturmon 7y ago
The author (Chotiner) has indeed made a mis-statement about the state of knowledge on planetary CH4, but that doesn't pertain directly to most of the article's content, which is about DNA/RNA. As you point out, the state of Mars CH4 is quite complex and extremely controversial, with 3 different measurements (Curiosity + 2 orbiters), low concentrations observed (~10 ppb) and multiple physical processes going on. Here's a pretty good recent summary: https://www.abc.net.au/news/science/2019-04-02/mars-express-confirms-methane-spike-detected-by-curiosity-rover/10563160 https://www.abc.net.au/news/science/2019-04-02/mars-express-... The DNA-sensing instrument that's being prototyped is here: http://setg.mit.edu http://setg.mit.edu

api 7y ago

I've wondered for years if maybe the idea of life originating on Earth might be the final geocentrism.

perl4ever 7y ago
We have a seemingly pretty firm age for the universe of 13.7 billion years; earth is 4.5 billion years old, and life on earth is at least 3.5 billion years old. So I think the step of going from nothing to the first single celled life is implausibly large to happen in a few million to a billion years, and to me, Occam's razor would imply that something necessary was developing during the previous 9 billion years, such as the development of chemotrophs underground in deep space.
natechols 7y ago
We haven't yet collected evidence that says terrestrial life originating on Earth is impossible or even unlikely, nor has anyone produced an alternative explanation that doesn't involve introducing additional external factors. It may indeed turn out to be incorrect (although I wouldn't be on it), but it's in no way comparable to geocentrism which simply couldn't be reconciled with experimental observation.
- perl4ever 7y ago
  If you lived on Long Island, and didn't know where humans came from, but you knew about how big the earth was, would it be rational or in accordance with Occam's razor to assume homo sapiens originated in your vicinity? Most people would in fact be wrong if they even assumed humans originated on their continent. I feel like people get sidetracked into talking about evidence, when the issue is that life originating on Earth should not be the default assumption. I feel like someone more lucid than me could make a good Bayesian sort of argument.
  - Avshalom 7y ago
    It's not exactly the default assumption though. Historically the default is that life was magicked into existence or came here from a previous world or some other creation story. The current abiogenisis story of molecules->proteins->cells->Life is relatively recent. The other thing is that because we have a fairly... ?linear record of evolution: if life did originate somewhere else it got to Earth in something like prokaryotic single cell form 3.5 billion years ago. Which means we can't use the idea of panspermia to tell us anything. It's neither predictive or explanatory. It tells us nothing of how or where life did originate or how life got started on Earth or what or where we should look for or expect in the rest of the Universe. The current theory suggests life could pop up extremely quickly, which itself already implies life is likely to exist in the rest of universe on some level so panspermia doesn't even mean anything with regards to how likely life is anywhere else.

reggieband 7y ago

What I find more interesting is the potential frequency with which new life from origins other than earth has been mixed together with what is here. A lot of stuff falls into our atmosphere and I doubt we know where all of it comes from. I commented today on a bit of dermatological discussion where they claim our skin has a biome of bacteria. This is in addition to the gut biome that is starting to look like it contributes to a wide array of human health issues. Part of me wonders how much of those biomes (e.g. how many bacteria within that biome) are from sources outside our planet.

rossdavidh 7y ago
Well, if they did, then the fact that the basic DNA machinery is the same implies that we and the alien bacteria had a common ancestor somewhere back there.
- reggieband 7y ago
  > implies that we and the alien bacteria had a common ancestor My intuition suggests that wouldn't be necessary. For example, if I saw a snowflake like structure on another planet I wouldn't be surprised since that kind of structure is a result of the physical properties of the elements involved. It could be the case DNA is very similar in that respect, a mathematical necessity given the properties of hydro-carbons. I suspect the science on that issue isn't settled.
  - perl4ever 7y ago
    I'm thinking someone may have proved by construction that DNA isn't the only possible code. Didn't someone make "artificial" DNA by substituting something chemically for some of it?
    - reggieband 7y ago
      That sounds slightly different than what I mean. You appear to be saying: "It is possible something DNA-like could be constructed from different materials in different codes and it would still be viable". I was saying: "It is possible hydrogen, carbon, oxygen, etc. will form into DNA as long as suitable conditions exist and this is common enough occurrence that multiple sources of DNA independently developed across the galaxy/universe". I only say this to assert that the appearance of DNA from a source other than Earth should not necessarily imply a common ancestor.

derekp7 7y ago

Even though we have only one datapoint, I wonder how much can be inferred from this planet's life characteristics. First, life came about rather shortly after the planet was able to sustain it. So this timing is either very unlikely, or biogenesis has a high probability of happening, or the initial life got seeded from off planet (from a very rare initial phenomenon). Second, all the biosignatures from all forms of life are similar. For example, corality (left handed versus right handed molecules) is the same in all life examples we had. So that means that biogenesis happened only once. Otherwise we would have multiple unrelated examples (yes, there is the possibility that one form "ate everything else", but we have all kinds of variety instead of only one organism becoming dominate). So if biogenesis happened only once (for all of our bio examples), then it is either a rare event that just happened to occur very shortly after the planet cooled, or it happened sometime before Earth was hospitable for life and elsewhere in the universe. Does any of this make sense? Or am I reading too much into the tea leaves?

inflatableDodo 7y ago
>Even though we have only one datapoint I think we can wrangle a few more datapoints if we are creative with perspective, for example, we have extremely good evidence to suggest that the planet Mars is currently inhabited by alien robots.
infectoid 7y ago
Your tea leaves are sound. I think this is why those of us interested in this are very much hanging out for results from our explorations of Mars. It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. What are the chances? On the positive side Mars had pretty much all the ingredients for life (chemically) and had a long enough period for at least something intersting to develop. On the negative side, the environment was still different to ours (gravity, climate, whether, etc). We still aren't clear on what conditions need to met for like to get going. This is why both positive or negative results on Mars are exciting. My favourite theory is that life actually takes ages to get started so much so that it started on Mars and finished on Earth (from Mars being impacted and debris making it to Earth). Kind of like a passing of the torch. Mars: "Crap. I'm dying. Hey Earth, can you take this thing I've been working on?" Earth: "Yep. No worries. I got this. Will try to send some back in a few billions years. Take care."

kleer001 7y ago

What if life is a fundamental property of a sufficiently complex universe and a stable energy gradient? That's where I'd put my money.

keithwhor 7y ago
This right here. Provided a body that can retain and emit heat from a star, it intuitively makes sense that given correct conditions the warm body would trend towards more complex head dissipation mechanisms. Life is just a more complex — and sustainable — exothermic reaction than standard oxidative mechanisms (fire). By the way: this isn't a new concept. Jeremy England at MIT has been espousing the concept for a while [0]. [0] https://www.quantamagazine.org/first-support-for-a-physics-theory-of-life-20170726/ https://www.quantamagazine.org/first-support-for-a-physics-t...
Koshkin 7y ago
Hm. Also, money could be a fundamental property of a sufficiently complex life.
- kleer001 7y ago
  I understand the downvote, but I also agree with the statement. IMHO money, markets, even democracy seem to me to follow directly from the challenges of living in a complex society which follows from the benefits of working at large scales. They even seem to me to be simply abstracted versions of more naturally evolved systems baked into life on Earth a billion years ago, i.e. ATP metabolism and multi-cellular life
- asfarley 7y ago
  The real question is - are iPhones a fundamental property of sufficiently complex life? Will the first alien culture we encounter have a 2D vision & touch-based thin interface to their global (galatic) network?
not_kurt_godel 7y ago
Seems like a bad bet given that from the evidence we have so far, life is an unbelievable statistical anomaly. There's no reason why life had to have evolve on Earth or survive long-term; it is sheer luck that we haven't been hit by gamma ray bursts or a supernova or any one of the other nasty, super-deadly things the cosmos could throw at us.

hirundo 7y ago

Maybe we could test this someday with petri dishes in orbit. Outfit satellites with catch basins that funnel into various potentially habitable pods and see what grows. Park them in a lagrange point for better isolation. But if panspermia is true such critters in the cosmic wind would be cousins of life on earth, and it would be difficult (impossible?) to distinguish an alien microbe from domestic contamination. If it's false we see nothing, and wonder if it's because space is sterile or we're just not yet offering it the right primeval soup.

bdamm 7y ago
Panspermia doesn’t only work (if it works) by microbes floating in space. Rather the idea is that microbes are embedded and somewhat protected in asteroids which then land somewhere habitable. The occasional close brushes between stars and their asteroid clouds provide the medium where microbes could be transferred between stars quickly enough to launch and land before the radiation destroys any hope of survival (like 20 thousand years.)
sjg007 7y ago
Cosmic rays sterilize everything in time, so it seems unlikely we would find anything.

mellosouls 7y ago

Minor fun fact: Fred Hoyle, possibly the most public proponent of Panspermia in the last few decades, also coined the phrase "Big Bang theory" to dismiss an alternative to his preferred Steady State theory of the universe. Sometime champion of arch positions, he was once quoted as saying "it is better to be interesting and wrong than boring and right". https://en.m.wikipedia.org/wiki/Fred_Hoyle https://en.m.wikipedia.org/wiki/Fred_Hoyle

throwaway2048 7y ago
It is a pretty out there theory, but at one point the universe would have cooled enough from the very hot big bang origins to allow liquid water to exist everywhere, but not cooled sufficiently to cause everything to freeze. If any rocky planets existed at the time, maybe that was the origin of life which was much more able to spread widely due to the small size of the early universe. https://arxiv.org/abs/1312.0613 https://arxiv.org/abs/1312.0613
- minitoar 7y ago
  This just sounds like a cool sci-fi setting/backstory.
RachelF 7y ago
Hoyle was great man, who said what he thought. His outspoken character probably cost him a Nobel Prize, though.

opportune 7y ago

Methane is not nearly as good a signal to look for life as larger organic molecules are. Methane can easily be created by abiotic processes and remain stable when not directly exposed to radiation or oxidizers indefinitely: this happens on earth, and we do have oxidizers everywhere. Larger organic molecules are less likely to have abiotic origins by any known process and are almost always much less stable. On earth you can test whether methane has organic or abiotic origins by testing its isotopes. We can do this because we understand decently well how the geologic past of earth unfolded. We could probably do a similar thing for mars >The Earth is 4.5 billion years old. And the universe, at least based on estimates from the Big Bang, is something like fourteen billion years. So, if life evolved somewhere else, that buys you about ten billion years of time. Obviously I'm no expert, but you have to keep in mind, it took a decent amount of time for non-violent stars to become the norm / stellar neighborhoods to calm down and for overall metallicity to become significant enough to allow for the formation of terrestrial planets.

sandworm101 7y ago
>> and for overall metallicity to become significant enough to allow for the formation of terrestrial planets. You don't need much metallicity before terrestrial planets start forming. They would certainly be rarer in the early universe, but stars filter material very quickly (pushing light stuff further away, stripping new planets to their dense cores). So even with 10% of today's metallicity, there would still be plenty of terrestrial planets. (lol. My spellcheck corrects "metallicity" to "Metallica".)
- irrational 7y ago
  So even with 10% of today's Metallica, there would still be plenty of terrestrial planets.
  - ivolimmen 7y ago
    Username checks out
tlb 7y ago

gojomo 7y ago

The idea life emerged long before Earth, and may be widespread in the universe, is fairly old: https://en.wikipedia.org/wiki/Panspermia https://en.wikipedia.org/wiki/Panspermia I suspect that a formal, anonymous survey of astrobiologists would find that the idea is far more prevalent among experts than Ruvkin's estimate that "one per cent would buy into the idea of life spreading the way I’m sort of promoting it". It's just risky to express, for cultural reasons, until there's tangible proof. Many scientists are temperamentally reluctant to speculate without conclusive evidence, especially given the penchant of the press to sensationalize any such theories. It'd raise difficult questions about our place in the universe, and possibly popular fears. Thinking science had already settled on a consensus that simple life is everywhere might even paradoxically reduce funding for new missions to test the idea. After all, there have been tantalizing hints of life-processes on Mars going back to the Viking lander experiments of the 1970s – and yet we still can't seem to send a lab package that'd definitively answer the question! But the hope of figuring it out motivates new missions. (As should be clear, I'm strongly in Ruvkin's camp – and regularly comment to that effect here on HN: https://hn.algolia.com/?query=gojomo%20panspermia&sort=byDate&prefix=false&page=0&dateRange=all&type=comment https://hn.algolia.com/?query=gojomo%20panspermia&sort=byDat... )

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dboreham 7y ago

Wasn't there a movie about this?

Causality1 7y ago

>It just seems like, once it evolves, it spreads. Hence why I draw exactly the opposite conclusion. It's my thinking that if life existed throughout our 13 billion year old galaxy it would have evolved to saoience and consumed all available resources long before the rise of humanity. The fact our planet hasn't been strip mined or colonized is, absent hard data, good reason to believe we're alone.

roca 7y ago
There's a big difference between microbial life and intelligent life. Bostrom and others have argued that, based on how long evolutionary milestones took on Earth, the "difficult step" is actually complex multicellular life.
- Causality1 7y ago
  The timeline implies that but experimentation indicates it may not have been that hard. https://www.nature.com/articles/s41598-019-39558-8 https://www.nature.com/articles/s41598-019-39558-8 https://www.sciencemag.org/news/2018/06/momentous-transition-multicellular-life-may-not-have-been-so-hard-after-all https://www.sciencemag.org/news/2018/06/momentous-transition...
  - roca 7y ago
    That's interesting. I agree with your conclusion that Fermi's paradox simply means there is no other intelligent life, though I think the jury's still out as to where the filter is.
    - Causality1 7y ago
      Indeed. There's quite a lot of debate surrounding it and a couple of mathematicians arguing we haven't hit the filter yet, but I maintain hope we're past it. It wounds my sci-fi loving heart to say this but humanity is probably better off alone.
- DoctorBit 7y ago

Darthy 7y ago

There was this interesting article posted here some time ago that plotted the complexity of life found on earth vs time, and by using the right methodology and logarithmic scales, it arrived at a nice linear line over many data points and several billions of years. And the line converged to a 0 point, but that point was a few billion years before earth was created 4.5 billion years ago, adding more credibility to a panspermia theory. Can anybody remember that article and its url?

Darthy 7y ago
Update: found it. Apparently the theory is contentious, with accusations that they cherry-picked their data points. Discussion: https://news.ycombinator.com/item?id=5580334 https://news.ycombinator.com/item?id=5580334
drewrv 7y ago
Is this it? https://www.technologyreview.com/s/513781/moores-law-and-the-origin-of-life/ https://www.technologyreview.com/s/513781/moores-law-and-the... (I found it elsewhere among these comments)

stewbrew 7y ago

"It could be that I’ve never had a religious thought in my life." The very idea that life has to originate from somewhere/somewhat and cannot just happen sounds like a secular reformulation of a typically religious statement.

tychomaz 7y ago

James Tour: The Mystery of the Origin of Life https://www.youtube.com/watch?v=zU7Lww-sBPg https://www.youtube.com/watch?v=zU7Lww-sBPg

ShamelessC 7y ago

I wish he had posited a theory for how life from Mars would have even gotten here. Some comments have said an asteroid hit Mars and then redirected to Earth with early life on it? Is that possible/likely?

AgentME 7y ago
Yes, it happens. There are about 200 meteorites found on Earth that are known to have come from Mars: https://en.wikipedia.org/wiki/Martian_meteorite https://en.wikipedia.org/wiki/Martian_meteorite

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apo 7y ago

The question of where life originated will have no good answer until we figure out how to create life from basic components. We still don't know how to do that yet. Yes, Urey and Miller showed that you could get simple organic molecules by passing an electric charge through gasses thought to be present around the early Earth. But going from low molecular weight inputs to life is a vastly different problem. You could think of it as the most complicated bootstrapping problem in the universe. Nobody has managed to do it in the lab, either. What can't be built from scratch can't be understood very well, and therein lies the problem. If we had a stepwise procedure for building a self-replicating, self-feeding organism of any level of complexity from base components, we would know exactly what to look for. Until then, the idea of sending a DNA amplifier to Mars isn't a bad fallback position.

dvfjsdhgfv 7y ago
If we succeed, it would be the most important breakthrough in the history of humanity, and would have very deep existential implications. It wouldn't definitely rule out a supreme being as the creator of the universe we live in, but it would make the gap between us and that being much smaller than millions of people on earth believe now.
- acqq 7y ago
  > would have very deep existential implications. I doubt that. > It wouldn't definitely rule out a supreme being as the creator of the universe we live in Yes, that's exactly what the believers will tell you even then. Think about it: the science knows today that every atom in our bodies is either produced 13.8 billion years ago (is it is H2) or in the explosion of some star. It's true for every element that you learn in the chemistry class. We know that the Earth is 4.7 billion years old. And we already know that humans share 99% percent of the DNA with chimps. And that 0.006 billion years ago on the Earth neither humans nor chimps existed, but their common ancestor. Do people who believe in a "miracle" divine intervention that supposedly happened only some 0.000002 billion years ago (or even only 0.0000014 billion years ago) when only at that point their deity became involved with the believers, do these people in anyway feel affected by all that? No. Compared to what we know today, their religious "messages from the deity" obviously prove that they were written by plain humans of older times, because these messages don't contain any knowledge we have today, but instead the "eternal" truths like "at the end of the day the Sun sets in the muddy pond" or that the Earth's sky is a solid dome: https://en.wikipedia.org/wiki/Firmament#Biblical_use https://en.wikipedia.org/wiki/Firmament#Biblical_use Do the believers feel affected by that? No.

rectangletangle 7y ago

An interesting phenomenon I rarely see brought up in support of panspermia is the apparent universality of the genetic code. The fact that all known life shares a common genetic structure implies a common ancestor. The lack of competing genetic codes could be interpreted to imply that life only started on earth once, or that it only made it to earth once. Natural selection is a constant force, presumably new genetic codes could offer an advantage, e.g., robustness against damaging mutation, resulting in multiple competing genetic codes. The notion of abiogenesis occurring only once on earth seems improbable considering complex organs like eyes have evolved independently several different times. Or the fact that convergent evolution "reinvents" similar species in response to similar selective pressures. Selective pressures constantly "push" life in the same directions, so it would seem that whatever forces gave rise to life would have happened so repeatedly, but there doesn't seem to be any evidence for that. A clean explanation for this would be that life didn't start on earth, and earth may have never had the right conditions to originate life, hence no competing genetic codes. But it was still hospitable enough to maintain life, so one universal genetic code flourishes with no emergent competition.

rjurney 7y ago
Yeah, it seems to have been incredibly unlikely. It took a long time.
hdfbdtbcdg 7y ago
Or life started multiple times but the results of one of those times outcompeted all the others.
- rectangletangle 7y ago
  This is true, but if that did happen presumably we could find some evidence for it, since it would be a relatively common occurrence during the period where earth was capable of abiogenesis. Because if it occurred at least twice, it probably happened many more times. The counterpoint is that the fossil record is very incomplete when going that far back, seeing as tectonic subduction literally wipes the slate clean.

edoo 7y ago

Given the complexity of DNA I think it is near obvious life did not originate on earth. If you assume it did not originate on earth that gives you at least another 10 billion years to work with.

gomijacogeo 7y ago
No, it really doesn't; it took a few generations of stars exploding and slamming into each other to make all those heavy elements we kinda consider important. You might be able to move it back another 3-4 billion years, which is admittedly a good long time. But really there's nothing yet that even remotely necessitates an extra-terrestrial origin for life. The problem is that, each time there was a "winner" in the very earliest more-chemistry-than-life arms-races, it essentially obliterated all record of what the competition looked like. It's not until pretty late in the game that no one new strategy obliterated all its peers - at that point we got the biological domains (prokaryotes and eukaryotes (which subsumed other prokaryotes as mitochondria and chloroplasts)) and viruses. From then on, the arms-races have been at higher levels of abstraction and the fight over the basics of biochemistry is 'settled'.

gremlinsinc 7y ago

What if we began a 'seeding' experiment, suppose there could be more life but isn't because life doesn't spread well in the vacuum of space. What if we began sending bacteria and other micro-organisms to potentially habitable planets via tiny spacecrafts. If we were to seed as many planets as we could possibly find, then eventually (in a million years or so), this entire galaxy could be teaming with life and the fermi paradox will be refuted as there will be no way not to see the life that is out there. We may still not be able to traverse the stars by that time at least not without generation ships but our descendents could at least wave from afar and maybe communicate across vast distances with intelligent life that we today helped seed/create.

titzer 7y ago
I'm not really on board with the idea of just blindly infecting all habitable planets with Earth life. We should look but don't touch until we have some clue what the heck we are doing and why.

DanielBMarkham 7y ago

Based on nothing but faith and an irreducible cynicism, my money says we end up going full circle, from "Earth is alone in the universe in regards to life" to "Life is a fungus, found anywhere the most basic of conditions are met" (at least over periods of millions of years at stellar scales) People forget that this discussion is not necessarily related to life. When various European explorers went out, in many cases they didn't know what to expect. When they met strange peoples, most of them refused to believe these were actually human. It takes a good long while for humans to recognize other lifeforms like us. We naturally think that we're unique, that wherever we call home is special and the center of things. Combine that with galactic distances and it might be a good while before we realize that the universe is actually full of aliens that look just like humans only with bumpy heads (Obligatory Star Trek joke)

wycy 7y ago

My biology knowledge is admittedly weak, but a question for those who might know: a lot of the discussion here is about how we only know of "life" based on nucleic acids (DNA). However, prions seem to replicate themselves without the help of nucleic acids. Could this in some way be seen as a competing form of "life"?

ecoled_ame 7y ago
Prions don't synthesize themselves, they just self-assemble. RNA can encode it's own information while also catalyzing self-replication.

DebtDeflation 7y ago

It always seemed to me that the biggest argument against panspermia is the relative hostility to "life" of space versus a planet like Earth. The heliosphere protects the solar system from a significant amount of interstellar cosmic rays and x-rays, Earth's magnetosphere offers additional protection, and our atmosphere, particularly the ozone layer, offers additional protection while also protecting against UV and high energy particles from the Sun. Ionizing radiation and short wavelength EM radiation are destructive to life and really the persistence of any large complex molecules. Combine that with the vacuum of space and temperatures barely above absolute zero and life originating via panspermia seems significantly less likely than originating natively on Earth.

koboll 7y ago
Not to mention atmospheric entry and asteroid impact.
mywittyname 7y ago
I'd say the biggest argument against panspermia is that the organisms responsible for it need to be successful locally and universally, at the same time. Reproduction is expensive and intrastellar reproduction is incredibly low yield. So organisms would need to have evolved to both capture an entire ecosystem AND waste a bunch of energy blowing their seed into the solar system. The idea just doesn't jibe with my understanding of evolution.

pfdietz 7y ago

I have wondered if panspermia could have occurred in the Sun's birth cluster. This cluster would have had a very high density of stars, with gas around them to slow and capture material ejected from their neighbor systems. And the asteroids in orbit around these stars would have still be warm enough to have liquid water in them, so life could potentially have been seeded in a wide variety of environments. This possibility, if true, means SETI might be worthwhile even if the actual origin of life is astronomically rare, much less than once per observable volume of the universe. SETI would look at the other stars that were in that cluster. Even if the rest of the universe were devoid of life, they (like the continents of Earth, or planets in our solar system) could share the same origin event. This scenario might also explain why life apparently originated so early in the history of our solar system: this sort of natal panspermia would statistically amplify origin-of-life events that happened early on, by multiplying the number of systems they'd affect. This amplification would occur even if OoL was extremely rare.

tempodox 7y ago

And what if life did originate on Earth? That's one of those hypothetical questions where the answer wouldn't make any practical difference, if we even had an answer. If and when we find extraterrestrial life, maybe we can come up with questions where the answers would be of practical value.

newsgremlin 7y ago

Don't know if anyone has ever considered this (ignoring gross simplifications), but as depictions of aliens are typically conceptualized from creatures we see on earth. Is it possible that if we are the only living creatures that have (yet) gained heightened consciousness, then spreading the DNA of all life on earth across the universe in a similar fashion to how our microbial life arrived on earth is how we ensure that life truly goes on if we fail?

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AILove 7y ago

What if this entire universe is an organism?

Grustaf 7y ago

“...what if it started here and then spread elsewhere? And so we found some sort of DNA on Mars, but that’s because it spread there from Earth. Is that possible? Yeah, but that sort of places us at the center of the universe, and all the force of history is to say, “Don’t think of us as the center. We’re nothing.”” What kind of argument is that? Sounds like some kind of anti-geocentric dogma, not an actual argument.

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