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This could be pretty bad news for finding complex life in space. The stability of Earth's carbon cycle is thought to be (partly) a result of plate tectonics. C

This could be pretty bad news for finding complex life in space. The stability of Earth's carbon cycle is thought to be (partly) a result of plate tectonics. Carbon gets trapped in rocks and volcanoes emit carbon again. Venus doesn't seem to have plate tectonics. One consequence of this is thought to be that volcanoes are much more common on Venus. It's also thought that 300-700 million years ago Venus went through a resurfacing event where basically the surface of the planet was replaced (the floor is lava). If the above is true and plate tectonics is a result of a planetary collision then life like ours should be even more rare than we thought.

Pet_Ant 2y ago
What was the surface of Venus like before that?
- Aerroon 2y ago
  I don't know. I'm unsure whether scientists do either. Chances are that it wasn't really any different than it is now. The resurfacing means that the surface is new - many fewer impact craters.
  - rbanffy 2y ago
    Venus' rotation is quite weird, could it be the result of an impact?
- duluca 2y ago
  That's the fascinating thing about lava/magma's power to simply erase what was there before. Plate tectonics does a similar thing when continents scrape each other clean. For all we know, Earth had an advanced civilization on it way before us and we'd have zero ways of knowing about it.
  - Evidlo 2y ago
    Some bits of landmass have been around for a few billion years. From this we have atmospheric records that rule out a large industrial civilization.
tifik 2y ago
Wouldn't large body collisions be a fairly common occurrence in young planetary systems though? Of course any additional condition makes life rarer, I'm just thinking this one might not make it rarer by as many orders of magnitude as it might look like at first glance.
- jvanderbot 2y ago
  And yet - where's all the plate techtonics in our solar system? Only 1 of four inner rocky planets seems to experience it.
  - jajko 2y ago
    Out of what, 500-1000 billions of planets just in milky way? I dont think folks do realize how big those numbers are. And there is no reason to ignore rest of the universe if we talk about probabilities and statistics
    - dartos 2y ago
      Tbh even if the number of life sustaining planets in the galaxy goes from 400B to 350B, that’s still rarer than we thought.
    - jvanderbot 2y ago
      It's just another fraction to multiply in the drake equation. Start with planets, cut down to rocky ones, only in habitable zone, only rotating a certain way, only with plate techtonics, etc etc. Or using your numbers, 1/4 factor eliminates 750 million possible candidates. That's not a happy thought.
  - eep_social 2y ago
    Yeah but 25% of a few hundred billion (planets in the milky way) is still a fair lot of opportunities. “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.”
    - 2y ago
jemmyw 2y ago
Extra conditions like this mean that the path we took would be rarer but doesn't necessarily make life any more rare. There could be plenty of other pathways to a stable carbon cycle. Or it might not even be a prerequisite, you could imagine a scenario where life gets a foothold then instigates the cycle itself. We just won't know until we've found something. And for us talking now we probably just won't know.
- jvanderbot 2y ago
  Especially because they may all just be indicators of something else. I've heard magnetic fields, moons, and plate techtonics are all important, but that really could just be "the right kind of planetary collision not too long ago"
  - Aerroon 2y ago
    Sure, but then add the evolutionary path on top of that. We had hundreds of millions of years of dinosaurs and no evidence of intelligent life. Then you've got to consider that Earth is basically approaching its twilight years. The planet is 4.5 billion years old, macroscopic multicellular life is 600 million to a billion years old. Humans have been around for 100,000 years. In 500 million to a billion years Earth will become uninhabitable again. Oh and our sun is unusually stable. Throw all of this together with an added "right type of huge planetary collision" and I feel like you're writing a lot more zeros into that probability. Of course it's possible that life could take a different path, but there was a lot of opportunity on Earth and it took a long time to get there.
    - jvanderbot 2y ago
      All that comes after the planet is suitable for emergence, which is the focus of the conversation. We can reinvent the drake equation all day if we want, but yeah, definitely, those are more factors to consider.
- felsokning 2y ago
  > There could be plenty of other pathways to a stable carbon cycle. To be fair, carbon is the only base that we have (first-hand) experience with. There _could_ be other bases.
api 2y ago
That big thing that whacked us and created the Moon may be responsible for our being here. Amazing. The simplest and most likely explanation for the Fermi paradox that does not rely on fanciful future great filters or even more fanciful galactic zoo hypotheses is that complex highly intelligent life capable of space flight is extraordinarily rare in space and time. When we go out there we might end up finding some bacteria-like organisms and simple fossils but nothing close to ourselves. But ultimately we don't know until we go see.
- dehrmann 2y ago
  The sample size is very low, but it's quite the coincidence that the only rocky planet in our solar system with life is the only one with an oversized moon.
  - deleted 2y ago
    [deleted]
- adriand 2y ago
  > complex highly intelligent life capable of space flight is extraordinarily rare in space and time That feels right to me especially given the timescales we are dealing with when we consider things even just in a galactic context. Heck, even the timescales on this planet alone are such that there could be multiple complex intelligent life forms on earth separated by sufficient time that they are never known to one another! Not to mention the fact that there are intelligent life forms on earth right now that we barely understand. For all these reasons It seems to me that we are far more likely to come across an alien artifact than an alien, and we haven’t started looking for these.
  - AlexAndScripts 2y ago
    https://en.m.wikipedia.org/wiki/Silurian_hypothesis https://en.m.wikipedia.org/wiki/Silurian_hypothesis Would we know if they went to space? How long would a geostationary satellite remain? It's both haunting and brilliant to think about the idea of entire other intelligent species and civilisations having lived on this planet without us ever knowing. Fire and iron and cities and empires and "great people", cultures and religions and stories and families... Civilisations and species rising and falling throughout the eons. It feels a little reminiscent of Sagan's "Pale Blue Dot", but on the scale of time, not space. I wonder if they might have considered this too.
deleted 2y ago
[deleted]
mnky9800n 2y ago
It's also possible that a reasonably homogenous atmospheric pressure does not promote sustained plate tectonics over geologic time scales. Since Venus has no oceans this could be why it has no plate tectonics currently.

Pet_Ant 2y ago

What was the surface of Venus like before that?

Aerroon 2y ago
I don't know. I'm unsure whether scientists do either. Chances are that it wasn't really any different than it is now. The resurfacing means that the surface is new - many fewer impact craters.
- rbanffy 2y ago
  Venus' rotation is quite weird, could it be the result of an impact?
duluca 2y ago
That's the fascinating thing about lava/magma's power to simply erase what was there before. Plate tectonics does a similar thing when continents scrape each other clean. For all we know, Earth had an advanced civilization on it way before us and we'd have zero ways of knowing about it.
- Evidlo 2y ago
  Some bits of landmass have been around for a few billion years. From this we have atmospheric records that rule out a large industrial civilization.

tifik 2y ago

Wouldn't large body collisions be a fairly common occurrence in young planetary systems though? Of course any additional condition makes life rarer, I'm just thinking this one might not make it rarer by as many orders of magnitude as it might look like at first glance.

jvanderbot 2y ago
And yet - where's all the plate techtonics in our solar system? Only 1 of four inner rocky planets seems to experience it.
- jajko 2y ago
  Out of what, 500-1000 billions of planets just in milky way? I dont think folks do realize how big those numbers are. And there is no reason to ignore rest of the universe if we talk about probabilities and statistics
  - dartos 2y ago
    Tbh even if the number of life sustaining planets in the galaxy goes from 400B to 350B, that’s still rarer than we thought.
  - jvanderbot 2y ago
    It's just another fraction to multiply in the drake equation. Start with planets, cut down to rocky ones, only in habitable zone, only rotating a certain way, only with plate techtonics, etc etc. Or using your numbers, 1/4 factor eliminates 750 million possible candidates. That's not a happy thought.
- eep_social 2y ago
  Yeah but 25% of a few hundred billion (planets in the milky way) is still a fair lot of opportunities. “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.”
  - 2y ago

jemmyw 2y ago

Extra conditions like this mean that the path we took would be rarer but doesn't necessarily make life any more rare. There could be plenty of other pathways to a stable carbon cycle. Or it might not even be a prerequisite, you could imagine a scenario where life gets a foothold then instigates the cycle itself. We just won't know until we've found something. And for us talking now we probably just won't know.

jvanderbot 2y ago
Especially because they may all just be indicators of something else. I've heard magnetic fields, moons, and plate techtonics are all important, but that really could just be "the right kind of planetary collision not too long ago"
- Aerroon 2y ago
  Sure, but then add the evolutionary path on top of that. We had hundreds of millions of years of dinosaurs and no evidence of intelligent life. Then you've got to consider that Earth is basically approaching its twilight years. The planet is 4.5 billion years old, macroscopic multicellular life is 600 million to a billion years old. Humans have been around for 100,000 years. In 500 million to a billion years Earth will become uninhabitable again. Oh and our sun is unusually stable. Throw all of this together with an added "right type of huge planetary collision" and I feel like you're writing a lot more zeros into that probability. Of course it's possible that life could take a different path, but there was a lot of opportunity on Earth and it took a long time to get there.
  - jvanderbot 2y ago
    All that comes after the planet is suitable for emergence, which is the focus of the conversation. We can reinvent the drake equation all day if we want, but yeah, definitely, those are more factors to consider.
felsokning 2y ago
> There could be plenty of other pathways to a stable carbon cycle. To be fair, carbon is the only base that we have (first-hand) experience with. There _could_ be other bases.

api 2y ago

That big thing that whacked us and created the Moon may be responsible for our being here. Amazing. The simplest and most likely explanation for the Fermi paradox that does not rely on fanciful future great filters or even more fanciful galactic zoo hypotheses is that complex highly intelligent life capable of space flight is extraordinarily rare in space and time. When we go out there we might end up finding some bacteria-like organisms and simple fossils but nothing close to ourselves. But ultimately we don't know until we go see.

dehrmann 2y ago
The sample size is very low, but it's quite the coincidence that the only rocky planet in our solar system with life is the only one with an oversized moon.
- deleted 2y ago
  [deleted]
adriand 2y ago
> complex highly intelligent life capable of space flight is extraordinarily rare in space and time That feels right to me especially given the timescales we are dealing with when we consider things even just in a galactic context. Heck, even the timescales on this planet alone are such that there could be multiple complex intelligent life forms on earth separated by sufficient time that they are never known to one another! Not to mention the fact that there are intelligent life forms on earth right now that we barely understand. For all these reasons It seems to me that we are far more likely to come across an alien artifact than an alien, and we haven’t started looking for these.
- AlexAndScripts 2y ago
  https://en.m.wikipedia.org/wiki/Silurian_hypothesis https://en.m.wikipedia.org/wiki/Silurian_hypothesis Would we know if they went to space? How long would a geostationary satellite remain? It's both haunting and brilliant to think about the idea of entire other intelligent species and civilisations having lived on this planet without us ever knowing. Fire and iron and cities and empires and "great people", cultures and religions and stories and families... Civilisations and species rising and falling throughout the eons. It feels a little reminiscent of Sagan's "Pale Blue Dot", but on the scale of time, not space. I wonder if they might have considered this too.

deleted 2y ago

[deleted]

mnky9800n 2y ago

It's also possible that a reasonably homogenous atmospheric pressure does not promote sustained plate tectonics over geologic time scales. Since Venus has no oceans this could be why it has no plate tectonics currently.