6 ms·

Mars lost all of its (surface) water presumably due to solar wind, and thus never had time to evolve complex life. Earth would have faced the same fate were it

Mars lost all of its (surface) water presumably due to solar wind, and thus never had time to evolve complex life. Earth would have faced the same fate were it not for the fact that the Moon collided with us at some distant point in time, surrendering its iron core to ours. Now, our Rare Earth has an unnaturally large active iron core, resulting in an unnaturally efficient magnetic field which is able to protect our waters from being blown away by Sun.

atoav 4y ago
One might be inclined to attribute the amount of good luck to devine intervention, but to this I would say: If the conditions on our planet would not have allowed for higher life, nobody would have been there to ask themselves why the conditions were slightly off.
- biren34 4y ago
  If you haven't heard of it, you've just stated the weak anthropomorphic principle.
  - pimbrah 4y ago
    *anthropic
    - biren34 4y ago
      Huh. Didn't realize I had those two words mixed up. Thanks!
  - atoav 4y ago
    Thanks, I did not know there was a term for this idea.
ramraj07 4y ago
I have very little reason to believe life evolved in Earth or even in Mars for that matter. The more likely scenario is that there’s rocks floating around everywhere that have spores of life throughout the galaxy ready to seed a suitable planet in geologically instantaneous timelines. That will explain the extremely rapid emergence of life on earth initially while it took a few billion years to evolve any further. In which case if Mars had flowing water at some point it likely also harbored at least single cell life. Source: biologist but not specializing in evolution.
- varjag 4y ago
  But you only introduce an unnecessary extra step in the same theory. Life still had to evolve somewhere, just that now it had to embark onto interstellar trip.
  - MattPalmer1086 4y ago
    Not entirely unnecessary. It's a big question as to why life started on Earth as soon as it did, pretty much as soon as it was even possible. That could be because life is very easy to start if conditions are right. In which case it's quite likely to have started on early Mars too, and we should expect to find at least simple life all over the place. The other possibility is that it didn't start on Earth, and was seeded from somewhere else.
    - varjag 4y ago
      Why not add more steps? The aliens¹ brought microbial life on an interstellar ship and seeded it. A lot better chance than riding out for a few million years on a piece of rock! See, it's approximately on the same trailing end of unlikely as panspermia, but I fancy this one more. ¹Let's call them Engineers
    - AareyBaba 4y ago
      The big question is how local regions of low entropy that exhibit metabolism and replication (ie. life) came into existance out of inanimate matter. Where it happened is secondary.
      - MattPalmer1086 4y ago
        Yes, that is the biggest question. Understanding where it happened may give us some clues of course.
  - mach1ne 4y ago
    But instead of having a single planet generating random molecular combinations to roll for proto-DNA, you have billions or more. Life would have to evolve extremely commonly for it to be more probable to evolve by itself on any specific planet than on literally any planet which then encouters an event causing panspermia. But alas, that's an external observer viewpoint. It's important to note that it does not say that life is more probable to have evolved somewhere else than Earth (since we have an effective sample size of 1). It only says that the extra step introduced in the panspermia theory does not have a negative probabilistic impact, on the contrary.
ratg13 4y ago
Seems like a bit of a stretch to say with certainty that Mars never evolved complex life 500+ million years ago.
- mach1ne 4y ago
  Fair point, but even with rovers we have zero indication to the fact, and thus it's a very reasonable estimate.
  - cheschire 4y ago
    Rovers are not the most effective tool for searching for fossils, especially microscopic fossils that can’t be seen from a distance on camera. They’re just the most effective tool we can send at the time we sent them. But a rover is only slightly more effective than just sending a dude with a buggy and a child’s beach kit.
  - ratg13 4y ago
    You are making another assumption that a large meteor didn't destroy everything on the planet surface. Considering we believe this happened to earth, it's not unreasonable to think the same happened to Mars at least once. https://youtu.be/PENT_hnyO-o https://youtu.be/PENT_hnyO-o
Aardwolf 4y ago
Just wondering, what would have stopped the Earth from having enough iron on its own in the first place? If the Moon could have that much iron, the Earth could as well have had it without needing to mix with the Moon, they're made from the same original matter after all.
- TSiege 4y ago
  The OP mispoke. It wasn't the moon that collided with earth, but another planet around mar's size. As a result of the collision the the core of that planet combined with the earth and the crust and parts of the mantle were ejected and coalesced into the moon. https://en.wikipedia.org/wiki/Giant-impact_hypothesis https://en.wikipedia.org/wiki/Giant-impact_hypothesis
  - TheBigSalad 4y ago
    I think the point still stands though, right? The moon is only 1% the mass of the Earth so if we had all that extra crust it wouldn't make our crust to core ratio so off that we couldn't have an atmosphere.
    - temp2022account 4y ago
      Read TSiege's correction again, it wasn't a (bad numbers) 1000T planet being impacted by a 10T object, it was a 500T object (earth) being impacted by a 500T object (now also earth) and ejecting a 10T object (now moon) from the debris. Without the event we'd have a planet even smaller than mars!
      - iso1631 4y ago
        I guess the question is rather than having 2 planets of 500T each form then collide, couldn't a single 1000T planet have formed from the same material?
        InvaderFizz 4y ago
eloff 4y ago
It's not that the water "blew away" in the solar wind, it's that the atmosphere did, taking the water vapor in the atmosphere with it. This is a very gradual process, which would happen on Earth too, if not for the magnetic field. I don't know that the collision with the moon is the secret here or not. I think it's complex.
- sneak 4y ago
  Neither Venus nor Mercury have substantial magnetic fields presently (compared to Earth). I don’t know enough to know if that supports the GP’s conclusion or not, but it may.
  - throwaway5752 4y ago
    These are pretty well researched, observed, and understood subjects. https://en.wikipedia.org/wiki/Atmosphere_of_Venus https://en.wikipedia.org/wiki/Atmosphere_of_Venus explains it quite well, particular https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Induced_magnetosphere https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Induced_ma... which explains how Venus is currently losing its atmosphere in the way described above. And https://en.wikipedia.org/wiki/Atmosphere_of_Mercury https://en.wikipedia.org/wiki/Atmosphere_of_Mercury: "The Mercurian exosphere consists of a variety of species originating either from the Solar wind or from the planetary crust [...] This corresponds to a surface pressure of less than 10^-14 bar (1 nPa)" which is about 1% of what is considered "ultra-high vacuum" (https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure) https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure)) Mercury has no magnetic field, and no meaningful atmosphere like we'd understand it. Venus has a minimal magnetic field, and is covered in hot dense CO2 layer because the solar wind blew away all the hydrogen and continues to blow away the atmosphere. The Earth has a much stronger magnetic field that has protected our oxidized hydrogen, and good evidence points to the giant impact hypothesis.

atoav 4y ago

One might be inclined to attribute the amount of good luck to devine intervention, but to this I would say: If the conditions on our planet would not have allowed for higher life, nobody would have been there to ask themselves why the conditions were slightly off.

biren34 4y ago
If you haven't heard of it, you've just stated the weak anthropomorphic principle.
- pimbrah 4y ago
  *anthropic
  - biren34 4y ago
    Huh. Didn't realize I had those two words mixed up. Thanks!
- atoav 4y ago
  Thanks, I did not know there was a term for this idea.

ramraj07 4y ago

I have very little reason to believe life evolved in Earth or even in Mars for that matter. The more likely scenario is that there’s rocks floating around everywhere that have spores of life throughout the galaxy ready to seed a suitable planet in geologically instantaneous timelines. That will explain the extremely rapid emergence of life on earth initially while it took a few billion years to evolve any further. In which case if Mars had flowing water at some point it likely also harbored at least single cell life. Source: biologist but not specializing in evolution.

varjag 4y ago
But you only introduce an unnecessary extra step in the same theory. Life still had to evolve somewhere, just that now it had to embark onto interstellar trip.
- MattPalmer1086 4y ago
  Not entirely unnecessary. It's a big question as to why life started on Earth as soon as it did, pretty much as soon as it was even possible. That could be because life is very easy to start if conditions are right. In which case it's quite likely to have started on early Mars too, and we should expect to find at least simple life all over the place. The other possibility is that it didn't start on Earth, and was seeded from somewhere else.
  - varjag 4y ago
    Why not add more steps? The aliens¹ brought microbial life on an interstellar ship and seeded it. A lot better chance than riding out for a few million years on a piece of rock! See, it's approximately on the same trailing end of unlikely as panspermia, but I fancy this one more. ¹Let's call them Engineers
  - AareyBaba 4y ago
    The big question is how local regions of low entropy that exhibit metabolism and replication (ie. life) came into existance out of inanimate matter. Where it happened is secondary.
    - MattPalmer1086 4y ago
      Yes, that is the biggest question. Understanding where it happened may give us some clues of course.
- mach1ne 4y ago
  But instead of having a single planet generating random molecular combinations to roll for proto-DNA, you have billions or more. Life would have to evolve extremely commonly for it to be more probable to evolve by itself on any specific planet than on literally any planet which then encouters an event causing panspermia. But alas, that's an external observer viewpoint. It's important to note that it does not say that life is more probable to have evolved somewhere else than Earth (since we have an effective sample size of 1). It only says that the extra step introduced in the panspermia theory does not have a negative probabilistic impact, on the contrary.

ratg13 4y ago

Seems like a bit of a stretch to say with certainty that Mars never evolved complex life 500+ million years ago.

mach1ne 4y ago
Fair point, but even with rovers we have zero indication to the fact, and thus it's a very reasonable estimate.
- cheschire 4y ago
  Rovers are not the most effective tool for searching for fossils, especially microscopic fossils that can’t be seen from a distance on camera. They’re just the most effective tool we can send at the time we sent them. But a rover is only slightly more effective than just sending a dude with a buggy and a child’s beach kit.
- ratg13 4y ago
  You are making another assumption that a large meteor didn't destroy everything on the planet surface. Considering we believe this happened to earth, it's not unreasonable to think the same happened to Mars at least once. https://youtu.be/PENT_hnyO-o https://youtu.be/PENT_hnyO-o

Aardwolf 4y ago

Just wondering, what would have stopped the Earth from having enough iron on its own in the first place? If the Moon could have that much iron, the Earth could as well have had it without needing to mix with the Moon, they're made from the same original matter after all.

TSiege 4y ago
The OP mispoke. It wasn't the moon that collided with earth, but another planet around mar's size. As a result of the collision the the core of that planet combined with the earth and the crust and parts of the mantle were ejected and coalesced into the moon. https://en.wikipedia.org/wiki/Giant-impact_hypothesis https://en.wikipedia.org/wiki/Giant-impact_hypothesis
- TheBigSalad 4y ago
  I think the point still stands though, right? The moon is only 1% the mass of the Earth so if we had all that extra crust it wouldn't make our crust to core ratio so off that we couldn't have an atmosphere.
  - temp2022account 4y ago
    Read TSiege's correction again, it wasn't a (bad numbers) 1000T planet being impacted by a 10T object, it was a 500T object (earth) being impacted by a 500T object (now also earth) and ejecting a 10T object (now moon) from the debris. Without the event we'd have a planet even smaller than mars!
    - iso1631 4y ago
      I guess the question is rather than having 2 planets of 500T each form then collide, couldn't a single 1000T planet have formed from the same material?
      - InvaderFizz 4y ago

eloff 4y ago

It's not that the water "blew away" in the solar wind, it's that the atmosphere did, taking the water vapor in the atmosphere with it. This is a very gradual process, which would happen on Earth too, if not for the magnetic field. I don't know that the collision with the moon is the secret here or not. I think it's complex.

sneak 4y ago
Neither Venus nor Mercury have substantial magnetic fields presently (compared to Earth). I don’t know enough to know if that supports the GP’s conclusion or not, but it may.
- throwaway5752 4y ago
  These are pretty well researched, observed, and understood subjects. https://en.wikipedia.org/wiki/Atmosphere_of_Venus https://en.wikipedia.org/wiki/Atmosphere_of_Venus explains it quite well, particular https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Induced_magnetosphere https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Induced_ma... which explains how Venus is currently losing its atmosphere in the way described above. And https://en.wikipedia.org/wiki/Atmosphere_of_Mercury https://en.wikipedia.org/wiki/Atmosphere_of_Mercury: "The Mercurian exosphere consists of a variety of species originating either from the Solar wind or from the planetary crust [...] This corresponds to a surface pressure of less than 10^-14 bar (1 nPa)" which is about 1% of what is considered "ultra-high vacuum" (https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure) https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure)) Mercury has no magnetic field, and no meaningful atmosphere like we'd understand it. Venus has a minimal magnetic field, and is covered in hot dense CO2 layer because the solar wind blew away all the hydrogen and continues to blow away the atmosphere. The Earth has a much stronger magnetic field that has protected our oxidized hydrogen, and good evidence points to the giant impact hypothesis.