4 ms·

The timing of the delivery is what's important here. These building blocks, organic matter, and water would have been depleted in the proto-Earth due to Solar i

The timing of the delivery is what's important here. These building blocks, organic matter, and water would have been depleted in the proto-Earth due to Solar irradiation. There needs to be some mechanism that delivers these ingredients from the outer Solar System. Bombardment by smaller rocks makes the most sense, and was likely triggered by the migration of Giant Planets, leading to a period of heavy bombardment (on a bare Earth -- no oceans, no volcanoes).. https://en.wikipedia.org/wiki/Nice_model https://en.wikipedia.org/wiki/Nice_model

lazide 7mo ago
Huh? Those smaller rocks would be even more irradiated, as they have no atmosphere? They’d also have to contend with re-entry.
- BinaryAsteroid 7mo ago
  The smaller rocks are composed of those materials in solid state (e.g., ice not water). They are less irradiated as they are further away from the Sun (think the asteroid belt and beyond). Atmospheric entry (if that's what you mean) is irrelevant. What matters here is the transport of materials from a place where they could have formed, to a place where they couldn't.
  - naasking 7mo ago
    > Atmospheric entry (if that's what you mean) is irrelevant. I think the OP meant that Earths magnetic field and atmosphere shields any terrestrial matter far more than than a bare asteroid that has no such protections, so it seems implausible at first glance that these things would develop or survive in open space rather than here.
    - Supermancho 7mo ago
      > it seems implausible at first glance that these things would develop or survive in open space rather than here. I don't think "organics developed in the vacuum of space" is implied. Survived? Well we have samples now confirming, if I'm understanding the basis for the discussion (the article).
      - lazide 7mo ago
        We have some organic ‘building block’ compounds confirmed frozen on some asteroids. But what we don’t have is any examples of them surviving re-entry. We also have a massive amount of those same compounds already here on the planet. Causality is… tenuous. But not impossible.
        beowulfey 7mo ago
        Causality was not the point. The point was to refute the seeding hypothesis, and because they found those molecules, the effort to falsify the hypothesis failed. Now we can move on to the next attempt to refute, which, as you say, might be to study whether molecules can survive conditions of reentry. Experiments do not tell us that something IS a certain way; only the ways it is not.
        lazide 7mo ago
        The ideal situation for an expert is to prove causality! It’s nearly impossible, but it is the holy grail! This experiment was to try to falsify one theory, yes, but as you note that is a very long way from the actual goal - or the level of certainty that the article is trying to imply. These articles are written due to funding needs, which is why the articles are the way they are - and why the scientists themselves are likely cringing too when they read these articles. At least until the checks (hopefully) arrive.
        Supermancho 7mo ago
        I was under the impression that the ejection of these compounds demonstrates that organics (blocks) can escape a gravity well, which implies they can likely re-enter another.
  - adrian_b 7mo ago
    Atmospheric entry is completely relevant because some people have made the illogical claim that meteorites falling on Earth could have contributed with such complex organic substances, like the nucleobases, to the appearance of life on Earth. The icy bodies from the outer Solar System that contain such organic substances are very easily vaporized during entry in the atmosphere of the Earth, so only a negligible fraction, if any, of the organic substances originally present in such a body would reach the surface of the Earth.
    - soco 7mo ago
      So we get organic vapors in the atmosphere right. Shouldn't that matter?
      - adrian_b 7mo ago
        One theory is that the primitive Earth contained much smaller quantities of the volatile chemical H, C, N, O and S, which are the main constituents of water and of organic substances. Then Earth collided with a great number of small bodies formed in the outer Solar System, which were rich in water and organic substances. This has modified the composition of the Earth towards the current composition. (Later Earth has lost a part of its hydrogen; because hydrogen is very light, it is lost continuously from the upper atmosphere, after water is dissociated by ultraviolet light; thus now the Earth has less water than around the appearance of life.) This theory is likely to be true, so meteorites probably have brought a good part of the chemical elements most needed by living beings. However, most of the pre-existing organic substances from meteorites must have decomposed and whatever has been preserved of them could not have had any significant role in the appearance of life here, because any living being would have needed a continuous supply with any molecules that it needed, otherwise it would have died immediately. Such a continuous supply could have been ensured only for molecules that were synthesized continuously in the local environment here, not for molecules arriving sporadically in meteorites and which would have been diluted afterwards over enormous areas, down to negligible concentrations.
    - foxglacier 7mo ago
      Wouldn't a big enough asteroid have an inner part which survives entry? You seem to be saying that it's impossible for any meteorite that might have these chemicals to not be completely vaporized which seems doubtful. Have you got a source?
  - lazide 7mo ago
    The earths poles?
- kmaitreys 7mo ago
  Those smaller rocks are in the outer solar system, where the solar irradiation is lower. But the way they are composed is lots of ices (volatile molecules in solid form) being built on the silicate/graphite refractory core. The ices remain preserved in the environment provided by the outer solar system.
- Sharlin 7mo ago
  It would’ve been specifically asteroids from beyond the "frost line", where it’s cold enough for volatile substances to coalesce and stay solid.
  - jvanderbot 7mo ago
    "volatile substances" is doing a lot of work. This means water and organics. Literal cold-storage seeds of life.
    - vdvebjrc 7mo ago
      [dead]
- general_reveal 7mo ago
  [flagged]
  - blacksmith_tb 7mo ago
    "The simple truth" being Genesis, for which there can be no evidence possible?
  - xandrius 7mo ago
    One thing I do agree with you: answering that an invisible dude did everything we don't get is much simpler indeed. Calling that a truth though.
    - amanaplanacanal 7mo ago
      The invisible dude is only simpler if you don't have to explain how the invisible dude was created.
  - vpribish 7mo ago
    pray tell, where do we learn this simple truth?
    - GetTheFacts 7mo ago
      >pray tell, where do we learn this simple truth? Praying[0] is a good start! That, coupled with large amounts of suspension of disbelief[1] helps too. I suggest drinking (or whatever your preferred brain-fogger might be) heavily. That helps you ignore the details -- because the "devil is in the details" and we mustn't have that, right? [0] Also known as "begging an imaginary sky daddy for help" [1] https://en.wikipedia.org/wiki/Suspension_of_disbelief https://en.wikipedia.org/wiki/Suspension_of_disbelief
      - twodave 7mo ago
        I realize you're just replying in kind to the GP, who wasn't very nice himself. I also think it's not necessary to feed such trolls in a way that insults all the religious folks who do enjoy this site and don't try to push our faith on others.
- bahmboo 7mo ago
  Meteorites are generally cold when they reach the surface of the earth. The heat of reentry is very brief and generally just on the surface. That's my understanding.
  - lazide 7mo ago
    The surfaces are typically melted - the ones that don’t just explode anyway. Icy meteorites never survive re-entry that I’m aware of; and most carbon/chondrite ones don’t either, but they are the most common type that do. They tend to be ‘dry’, however. Re-entry is a very ‘angry’ process.
- DoctorOetker 7mo ago
  Extra terrestrial propagation of life, if real would have evolved to have non-zero survival rates in interstellar radiation regimes and timescales. The fragility of life-as-we-know-it that has undergone serial passage in an environment largely shielded from radiation, is not necessarily representative of putative life-forms carried by little rocks in space. I am neither convinced for nor against the idea that life may have been carried over by interstellar rocks: on the one hand, its a major promiscuity between celestial bodies within star systems, galaxies, etc. on the other hand since we haven't discovered other life forms yet we have no idea on the missing probability densities of life in the bulk of the universe, so the Bayesian catapult can swing either way, we just lack the data for now.

lazide 7mo ago

Huh? Those smaller rocks would be even more irradiated, as they have no atmosphere? They’d also have to contend with re-entry.

BinaryAsteroid 7mo ago
The smaller rocks are composed of those materials in solid state (e.g., ice not water). They are less irradiated as they are further away from the Sun (think the asteroid belt and beyond). Atmospheric entry (if that's what you mean) is irrelevant. What matters here is the transport of materials from a place where they could have formed, to a place where they couldn't.
- naasking 7mo ago
  > Atmospheric entry (if that's what you mean) is irrelevant. I think the OP meant that Earths magnetic field and atmosphere shields any terrestrial matter far more than than a bare asteroid that has no such protections, so it seems implausible at first glance that these things would develop or survive in open space rather than here.
  - Supermancho 7mo ago
    > it seems implausible at first glance that these things would develop or survive in open space rather than here. I don't think "organics developed in the vacuum of space" is implied. Survived? Well we have samples now confirming, if I'm understanding the basis for the discussion (the article).
    - lazide 7mo ago
      We have some organic ‘building block’ compounds confirmed frozen on some asteroids. But what we don’t have is any examples of them surviving re-entry. We also have a massive amount of those same compounds already here on the planet. Causality is… tenuous. But not impossible.
      - beowulfey 7mo ago
        Causality was not the point. The point was to refute the seeding hypothesis, and because they found those molecules, the effort to falsify the hypothesis failed. Now we can move on to the next attempt to refute, which, as you say, might be to study whether molecules can survive conditions of reentry. Experiments do not tell us that something IS a certain way; only the ways it is not.
        lazide 7mo ago
        The ideal situation for an expert is to prove causality! It’s nearly impossible, but it is the holy grail! This experiment was to try to falsify one theory, yes, but as you note that is a very long way from the actual goal - or the level of certainty that the article is trying to imply. These articles are written due to funding needs, which is why the articles are the way they are - and why the scientists themselves are likely cringing too when they read these articles. At least until the checks (hopefully) arrive.
      - Supermancho 7mo ago
        I was under the impression that the ejection of these compounds demonstrates that organics (blocks) can escape a gravity well, which implies they can likely re-enter another.
- adrian_b 7mo ago
  Atmospheric entry is completely relevant because some people have made the illogical claim that meteorites falling on Earth could have contributed with such complex organic substances, like the nucleobases, to the appearance of life on Earth. The icy bodies from the outer Solar System that contain such organic substances are very easily vaporized during entry in the atmosphere of the Earth, so only a negligible fraction, if any, of the organic substances originally present in such a body would reach the surface of the Earth.
  - soco 7mo ago
    So we get organic vapors in the atmosphere right. Shouldn't that matter?
    - adrian_b 7mo ago
      One theory is that the primitive Earth contained much smaller quantities of the volatile chemical H, C, N, O and S, which are the main constituents of water and of organic substances. Then Earth collided with a great number of small bodies formed in the outer Solar System, which were rich in water and organic substances. This has modified the composition of the Earth towards the current composition. (Later Earth has lost a part of its hydrogen; because hydrogen is very light, it is lost continuously from the upper atmosphere, after water is dissociated by ultraviolet light; thus now the Earth has less water than around the appearance of life.) This theory is likely to be true, so meteorites probably have brought a good part of the chemical elements most needed by living beings. However, most of the pre-existing organic substances from meteorites must have decomposed and whatever has been preserved of them could not have had any significant role in the appearance of life here, because any living being would have needed a continuous supply with any molecules that it needed, otherwise it would have died immediately. Such a continuous supply could have been ensured only for molecules that were synthesized continuously in the local environment here, not for molecules arriving sporadically in meteorites and which would have been diluted afterwards over enormous areas, down to negligible concentrations.
  - foxglacier 7mo ago
    Wouldn't a big enough asteroid have an inner part which survives entry? You seem to be saying that it's impossible for any meteorite that might have these chemicals to not be completely vaporized which seems doubtful. Have you got a source?
- lazide 7mo ago
  The earths poles?
kmaitreys 7mo ago
Those smaller rocks are in the outer solar system, where the solar irradiation is lower. But the way they are composed is lots of ices (volatile molecules in solid form) being built on the silicate/graphite refractory core. The ices remain preserved in the environment provided by the outer solar system.
Sharlin 7mo ago
It would’ve been specifically asteroids from beyond the "frost line", where it’s cold enough for volatile substances to coalesce and stay solid.
- jvanderbot 7mo ago
  "volatile substances" is doing a lot of work. This means water and organics. Literal cold-storage seeds of life.
  - vdvebjrc 7mo ago
    [dead]
general_reveal 7mo ago
[flagged]
- blacksmith_tb 7mo ago
  "The simple truth" being Genesis, for which there can be no evidence possible?
- xandrius 7mo ago
  One thing I do agree with you: answering that an invisible dude did everything we don't get is much simpler indeed. Calling that a truth though.
  - amanaplanacanal 7mo ago
    The invisible dude is only simpler if you don't have to explain how the invisible dude was created.
- vpribish 7mo ago
  pray tell, where do we learn this simple truth?
  - GetTheFacts 7mo ago
    >pray tell, where do we learn this simple truth? Praying[0] is a good start! That, coupled with large amounts of suspension of disbelief[1] helps too. I suggest drinking (or whatever your preferred brain-fogger might be) heavily. That helps you ignore the details -- because the "devil is in the details" and we mustn't have that, right? [0] Also known as "begging an imaginary sky daddy for help" [1] https://en.wikipedia.org/wiki/Suspension_of_disbelief https://en.wikipedia.org/wiki/Suspension_of_disbelief
    - twodave 7mo ago
      I realize you're just replying in kind to the GP, who wasn't very nice himself. I also think it's not necessary to feed such trolls in a way that insults all the religious folks who do enjoy this site and don't try to push our faith on others.
bahmboo 7mo ago
Meteorites are generally cold when they reach the surface of the earth. The heat of reentry is very brief and generally just on the surface. That's my understanding.
- lazide 7mo ago
  The surfaces are typically melted - the ones that don’t just explode anyway. Icy meteorites never survive re-entry that I’m aware of; and most carbon/chondrite ones don’t either, but they are the most common type that do. They tend to be ‘dry’, however. Re-entry is a very ‘angry’ process.
DoctorOetker 7mo ago
Extra terrestrial propagation of life, if real would have evolved to have non-zero survival rates in interstellar radiation regimes and timescales. The fragility of life-as-we-know-it that has undergone serial passage in an environment largely shielded from radiation, is not necessarily representative of putative life-forms carried by little rocks in space. I am neither convinced for nor against the idea that life may have been carried over by interstellar rocks: on the one hand, its a major promiscuity between celestial bodies within star systems, galaxies, etc. on the other hand since we haven't discovered other life forms yet we have no idea on the missing probability densities of life in the bulk of the universe, so the Bayesian catapult can swing either way, we just lack the data for now.