4 ms·

Formation of the moon brought water to Earth

82 points by dnetesn 7y ago

DavidComposing 7y ago
wait what?
- simonh 7y ago
  All the other inner planets and asteroids are dry, but Earth is wet, so it’s always been a bit of a mystery where the water came from.
  - encoderer 7y ago
    Where did the water on Mars come from? Any correlation?
    - simonh 7y ago
      Mars, as far as we can tell, has very little water compared to Earth, even back when it appears to have had liquid water on the surface. It's a bit further out, so we'd expect it to have more water compared to the rest of the inner planets. It seems to be consistent with occasional deliveries of water from collisions with comets. In comparison, Earth has vastly more water.
mirimir 7y ago
So is Theia's core now Mercury?
- dr_orpheus 7y ago
  The theory is that much of Theia was absorbed in to the Earth and the mass that was ejected during the collision became the moon. https://en.wikipedia.org/wiki/Theia_(planet) https://en.wikipedia.org/wiki/Theia_(planet)
RosanaAnaDana 7y ago
I don't know if there are any astrobiologists or chemists, but this brings to mind one of my favorite pet theories regarding abiogenesis, one that I've been thinking of more and more since the new horizons mission. When we did the flyby of Pluto, I was drop jawed when we saw how dynamic the surface was. I sincerely expected a rockier, more oxidized, surface with no clear evidence of a geological cycle. Obviously what we saw was far more complex, and it brought the idea that a geology of volatile ices would be possible on these more marginal bodies (like Pluto). The question I have is regarding what kinds of chemistry are possible on icy bodies like Pluto. If there is a complex geology, this indicates to me that things are going from liquid to solid (nitrogen ice, oxygen ice, etc..), so are some kinds of chemical bonds (specifically, organic ones) can form if a body like Pluto is has a dynamic geology? Is it possible that the organic precursors for life are constantly accumulating on icy bodies like Pluto, and while obviously, live can't form on Pluto, could an impact discharge a massive quantity of precursor chemistry onto a planet more hospitable? Its an interesting aside that pretty much imminently after the earths surface solidified and cooled after the impact even, life began.
- dumbfoundded 7y ago
  Not an expert here at all but asteroids often do carry precursors for life. Asteroids on Earth have been found carrying organic compounds: https://www.smithsonianmag.com/science-nature/the-building-blocks-of-life-may-have-come-from-outer-space-3884354/ https://www.smithsonianmag.com/science-nature/the-building-b...
  - RosanaAnaDana 7y ago
    Sure, but my point here isn't about presence, but quantity. We've known that radiation can cause the creation of bio-molecules and precursor molecules for a very long time. But there almost no way that process can generate a significant enough quantity of these molecules to really seed planets. Largely its about concentration gradients, which is why I personal have found arguments about life forming via early oceans unconvincing. A couple asteroids (or even hundreds) worth of bio-molecules spread out over an ocean, is still basically nothing. You have to have enough material concentrated in a small enough space; you need a thermodynamic process that postpones equilibrium; then you need a gradient to drive the formation of more and more complicated molecules. Like, Pluto type objects are far and away more common then earthlike objects. If there is a process that can accumulate bio-molecules in mass on these types of bodies, that's pretty game changing.
njarboe 7y ago
The scientific article that this summary is based on can be found here[1]. [1]http://dx.doi.org/10.1038/s41550-019-0779-y http://dx.doi.org/10.1038/s41550-019-0779-y
kristianp 7y ago
That doesn't bode well for the idea of habitable planets in other solar systems. If this kind of collision is relatively rare, most rocky exo-planets will have much less water than Earth has. Reminds me of Asimov's storyline in the Foundation series about the rarity of the planet that humans come from (and the reason no complex lifeforms existed anywhere else), although his premise was a large amount of radioactivity on earth, IIRC.
- dumbfoundded 7y ago
  We just don't know enough about life or planet formation to know how this bodes. On its surface, everything that makes the formation of the Earth appear rarer would suggest life, in general, is rarer but honestly we don't know. We don't even know if there's life on Europa even though there would appear to be all the conditions present to make life as it lives at the bottom of our oceans. We don't even know if water is a reasonable prerequisite for life. We don't know if life has to be carbon-based. Sulfur also presents a reasonable alternative. Would we even recognize other life if was right in front of us if it relied on completely different mechanisms? Maybe even our idea of time is too short lived or long lived to even recognize other complex systems as alive. We shouldn't extrapolate too much from a single data point.
  - ianai 7y ago
    I’m glad I’m not the only one thinking that! All of the paradoxes and stuff just strike me as hubris, at best.
    - raducu 7y ago
      But is it just the paradoxes? To me it seems that the early estimations of the numbers of inhabited planets from the Drake equations seem like hubris. Aren't we moving from the "we live in a Star Trek type galaxy, teaming with life" to "well, maybe we are alone in the whole Galaxy but not the Universe" to "Actually, the more we learn about how life on Earth came to be, the more it looks like we are alone in the whole UNIVERSE -- because it seems like every day we find more free terms to the Drake equation". Isn't the whole "we really don't know yet" argument hubris? Isn't it true that you cannot prove the lack of existence of something? Compared to 50 years ago, where do we stand with the question "Are we alone in the universe?" What is 50 years of data telling us, should we be more optimistic or pessimistic? Or is it just saying "we really don't know yet" -- because that's where I believe the real hubris lies -- not accepting the most likely scenario the data we have points to.
vertline3 7y ago
I was just reading that Mars was found to have the remains of an icecap one mile under the surface, so was Mars also hit with a meteor?
tigerlily 7y ago
What would happen if we added (5 or 10%) more water to the Earth today?

82 points by dnetesn 7y ago

DavidComposing 7y ago

wait what?

simonh 7y ago
All the other inner planets and asteroids are dry, but Earth is wet, so it’s always been a bit of a mystery where the water came from.
- encoderer 7y ago
  Where did the water on Mars come from? Any correlation?
  - simonh 7y ago
    Mars, as far as we can tell, has very little water compared to Earth, even back when it appears to have had liquid water on the surface. It's a bit further out, so we'd expect it to have more water compared to the rest of the inner planets. It seems to be consistent with occasional deliveries of water from collisions with comets. In comparison, Earth has vastly more water.

mirimir 7y ago

So is Theia's core now Mercury?

dr_orpheus 7y ago
The theory is that much of Theia was absorbed in to the Earth and the mass that was ejected during the collision became the moon. https://en.wikipedia.org/wiki/Theia_(planet) https://en.wikipedia.org/wiki/Theia_(planet)

RosanaAnaDana 7y ago

I don't know if there are any astrobiologists or chemists, but this brings to mind one of my favorite pet theories regarding abiogenesis, one that I've been thinking of more and more since the new horizons mission. When we did the flyby of Pluto, I was drop jawed when we saw how dynamic the surface was. I sincerely expected a rockier, more oxidized, surface with no clear evidence of a geological cycle. Obviously what we saw was far more complex, and it brought the idea that a geology of volatile ices would be possible on these more marginal bodies (like Pluto). The question I have is regarding what kinds of chemistry are possible on icy bodies like Pluto. If there is a complex geology, this indicates to me that things are going from liquid to solid (nitrogen ice, oxygen ice, etc..), so are some kinds of chemical bonds (specifically, organic ones) can form if a body like Pluto is has a dynamic geology? Is it possible that the organic precursors for life are constantly accumulating on icy bodies like Pluto, and while obviously, live can't form on Pluto, could an impact discharge a massive quantity of precursor chemistry onto a planet more hospitable? Its an interesting aside that pretty much imminently after the earths surface solidified and cooled after the impact even, life began.

dumbfoundded 7y ago
Not an expert here at all but asteroids often do carry precursors for life. Asteroids on Earth have been found carrying organic compounds: https://www.smithsonianmag.com/science-nature/the-building-blocks-of-life-may-have-come-from-outer-space-3884354/ https://www.smithsonianmag.com/science-nature/the-building-b...
- RosanaAnaDana 7y ago
  Sure, but my point here isn't about presence, but quantity. We've known that radiation can cause the creation of bio-molecules and precursor molecules for a very long time. But there almost no way that process can generate a significant enough quantity of these molecules to really seed planets. Largely its about concentration gradients, which is why I personal have found arguments about life forming via early oceans unconvincing. A couple asteroids (or even hundreds) worth of bio-molecules spread out over an ocean, is still basically nothing. You have to have enough material concentrated in a small enough space; you need a thermodynamic process that postpones equilibrium; then you need a gradient to drive the formation of more and more complicated molecules. Like, Pluto type objects are far and away more common then earthlike objects. If there is a process that can accumulate bio-molecules in mass on these types of bodies, that's pretty game changing.

njarboe 7y ago

The scientific article that this summary is based on can be found here[1]. [1]http://dx.doi.org/10.1038/s41550-019-0779-y http://dx.doi.org/10.1038/s41550-019-0779-y

kristianp 7y ago

That doesn't bode well for the idea of habitable planets in other solar systems. If this kind of collision is relatively rare, most rocky exo-planets will have much less water than Earth has. Reminds me of Asimov's storyline in the Foundation series about the rarity of the planet that humans come from (and the reason no complex lifeforms existed anywhere else), although his premise was a large amount of radioactivity on earth, IIRC.

dumbfoundded 7y ago
We just don't know enough about life or planet formation to know how this bodes. On its surface, everything that makes the formation of the Earth appear rarer would suggest life, in general, is rarer but honestly we don't know. We don't even know if there's life on Europa even though there would appear to be all the conditions present to make life as it lives at the bottom of our oceans. We don't even know if water is a reasonable prerequisite for life. We don't know if life has to be carbon-based. Sulfur also presents a reasonable alternative. Would we even recognize other life if was right in front of us if it relied on completely different mechanisms? Maybe even our idea of time is too short lived or long lived to even recognize other complex systems as alive. We shouldn't extrapolate too much from a single data point.
- ianai 7y ago
  I’m glad I’m not the only one thinking that! All of the paradoxes and stuff just strike me as hubris, at best.
  - raducu 7y ago
    But is it just the paradoxes? To me it seems that the early estimations of the numbers of inhabited planets from the Drake equations seem like hubris. Aren't we moving from the "we live in a Star Trek type galaxy, teaming with life" to "well, maybe we are alone in the whole Galaxy but not the Universe" to "Actually, the more we learn about how life on Earth came to be, the more it looks like we are alone in the whole UNIVERSE -- because it seems like every day we find more free terms to the Drake equation". Isn't the whole "we really don't know yet" argument hubris? Isn't it true that you cannot prove the lack of existence of something? Compared to 50 years ago, where do we stand with the question "Are we alone in the universe?" What is 50 years of data telling us, should we be more optimistic or pessimistic? Or is it just saying "we really don't know yet" -- because that's where I believe the real hubris lies -- not accepting the most likely scenario the data we have points to.

vertline3 7y ago

I was just reading that Mars was found to have the remains of an icecap one mile under the surface, so was Mars also hit with a meteor?

tigerlily 7y ago

What would happen if we added (5 or 10%) more water to the Earth today?