3 ms·

I've tried reading the paper, which is obviously less hand wavy than this mess of a blog post but pretty tough going for a layman. I still don't see how they co

I've tried reading the paper, which is obviously less hand wavy than this mess of a blog post but pretty tough going for a layman. I still don't see how they conclude that the water arrived all at once instead of in a bunch of comets... https://www.science.org/doi/10.1126/sciadv.adw1280 https://www.science.org/doi/10.1126/sciadv.adw1280

hammock 1y ago
All at once is what explains the isotopic homogeneity (e.g. in oxygen) between the earth and the moon
- andrewflnr 1y ago
  Meaning not just all the water but all the oxygen came in with Theia?
o11c 1y ago
I also don't see how they disprove the contribution of gravity. Remember that Earth is composed of fifty Titan-sized bodies. Titan, and probably Uranus and Neptune, probably have their methane etc. as a result of outgassing - initially, the volatiles are embedded in the inner rocks, but as they gravitationally differentiate and heat - and are subject to tide-like interactions with other bodies - the volatiles are released. (The real questions are "Why does Ganymede not have an atmosphere?" and "What's up with Venus, really?")
- andrewflnr 1y ago
  I believe the idea is that the water was all cooked out of Earth's protoplanetary disk material before it even formed large chunks. So gravity never got a chance to "contribute" on that front.
  - o11c 1y ago
    Well, that seems to make 2 major assumptions (and several minor ones), both of which are probably false: * that the planetesimals that formed Earth had the same orbital characteristics (notably eccentricity), rather than being averaged out. * that planetesimals formed from dust in largely the same manner as planets form from planetesimals
    - andrewflnr 1y ago
      ...no, I don't think it makes either of those assumptions.
tim333 1y ago
The >Our Solar System formed around 4,568 million years ago. Considering that it only took up to 3 million years to determine the chemical properties of the Earth sounds suspiciously precise. You'd imaging the proto Earth would have formed gradually over millions of years from rocks and dust merging rather than suddenly there 4,568 m years ago and then shortly after crashed into?
- andrewflnr 1y ago
  Well, 3 million is "millions". Anyway, that very quote continues: > "...this is surprisingly fast," says first author Kruttasch. So they don't entirely disagree that it's weird. But why are you replying to me with a quote from the article I already called a mess? Try your hand at the paper if you want real answers. :D Like I said, tough going, but they sure seem to think they have the sigfigs to back it up.
8bitsrule 1y ago
>this mess of a blog post It's that. Just one more in a long line of wild-eyed 'the Earth collided with' theories. > Scientists have shown that Earth’s basic chemistry solidified within just three million years ... They haven't 'shown' anything. They may have evidence to support part of one model ... if they can demonstrate that a Theia probably existed in the first place. Try to read it? Thick going. https://www.science.org/doi/10.1126/sciadv.adw1280 https://www.science.org/doi/10.1126/sciadv.adw1280. Quoting from that: "Today’s element abundances of the BSE and isotope constraints strongly suggest that the bulk Earth comprises ~90% PE, ~10% Theia, and ~0.4% late veneer material... Other models suggest that Earth formed from ~60% PE and ~40% Theia ..." >a later collision with Theia likely delivered the water Etc. If water was so hard to get ... where in the hell did this hypothetical, no evidence 'likely' get the water it 'delivered'?
- andrewflnr 1y ago
  Water wasn't hard to get in the outer solar system. You know, where all the ice balls are? They're not here to "demonstrate" the Theia impact theory, because there's already tons of other work doing that.

hammock 1y ago

All at once is what explains the isotopic homogeneity (e.g. in oxygen) between the earth and the moon

andrewflnr 1y ago
Meaning not just all the water but all the oxygen came in with Theia?

o11c 1y ago

I also don't see how they disprove the contribution of gravity. Remember that Earth is composed of fifty Titan-sized bodies. Titan, and probably Uranus and Neptune, probably have their methane etc. as a result of outgassing - initially, the volatiles are embedded in the inner rocks, but as they gravitationally differentiate and heat - and are subject to tide-like interactions with other bodies - the volatiles are released. (The real questions are "Why does Ganymede not have an atmosphere?" and "What's up with Venus, really?")

andrewflnr 1y ago
I believe the idea is that the water was all cooked out of Earth's protoplanetary disk material before it even formed large chunks. So gravity never got a chance to "contribute" on that front.
- o11c 1y ago
  Well, that seems to make 2 major assumptions (and several minor ones), both of which are probably false: * that the planetesimals that formed Earth had the same orbital characteristics (notably eccentricity), rather than being averaged out. * that planetesimals formed from dust in largely the same manner as planets form from planetesimals
  - andrewflnr 1y ago
    ...no, I don't think it makes either of those assumptions.

tim333 1y ago

The >Our Solar System formed around 4,568 million years ago. Considering that it only took up to 3 million years to determine the chemical properties of the Earth sounds suspiciously precise. You'd imaging the proto Earth would have formed gradually over millions of years from rocks and dust merging rather than suddenly there 4,568 m years ago and then shortly after crashed into?

andrewflnr 1y ago
Well, 3 million is "millions". Anyway, that very quote continues: > "...this is surprisingly fast," says first author Kruttasch. So they don't entirely disagree that it's weird. But why are you replying to me with a quote from the article I already called a mess? Try your hand at the paper if you want real answers. :D Like I said, tough going, but they sure seem to think they have the sigfigs to back it up.

8bitsrule 1y ago

>this mess of a blog post It's that. Just one more in a long line of wild-eyed 'the Earth collided with' theories. > Scientists have shown that Earth’s basic chemistry solidified within just three million years ... They haven't 'shown' anything. They may have evidence to support part of one model ... if they can demonstrate that a Theia probably existed in the first place. Try to read it? Thick going. https://www.science.org/doi/10.1126/sciadv.adw1280 https://www.science.org/doi/10.1126/sciadv.adw1280. Quoting from that: "Today’s element abundances of the BSE and isotope constraints strongly suggest that the bulk Earth comprises ~90% PE, ~10% Theia, and ~0.4% late veneer material... Other models suggest that Earth formed from ~60% PE and ~40% Theia ..." >a later collision with Theia likely delivered the water Etc. If water was so hard to get ... where in the hell did this hypothetical, no evidence 'likely' get the water it 'delivered'?

andrewflnr 1y ago
Water wasn't hard to get in the outer solar system. You know, where all the ice balls are? They're not here to "demonstrate" the Theia impact theory, because there's already tons of other work doing that.