Re: [math-fun] carbon oxygen bogosity
I've long been baffled by the claim that the free oxygen in the atmosphere came from photosynthesis. If the atmosphere started out neutral, then oxygen in the atmosphere must be balanced by reduced matter (biomass, peat, coal, oil, natural gas, etc.). It seems implausible that there's enough combustible stuff that burning it all would consume all the oxygen. Note that carbon in carbonate rocks isn't reduced -- it's already combined with as much oxygen as it can be. Carbonate rocks can explain the disappearance of carbon dioxide from the atmosphere, but not the appearance of free oxygen. The obvious alternative is that over many millions of years solar UV split water vapor into oxygen and hydrogen, and the hydrogen escaped into space. This would drop the sea level, but only by a few meters. Yes, this is happening too slowly today to account for how much free oxygen there is. That's because the upper atmosphere, where there's plenty of solar UV, is very dry, due to the stratospheric cold trap. But the "iceball earth" theory says the ground-level climate oscillated for most of the Proterozoic eon between about -50 C and +50 C. During the warm periods, it seems likely that the upper stratosphere would have been warm and moist. And that's just when the oxygen appeared. Am I really the first to think of this? If I'm right, discovery of a planet with an oxygen atmosphere wouldn't necessarily imply that there is, or ever was, life on that planet. As for Henry Baker's conjecture that massive fires at the end of the Cretaceous consumed much of the world's free oxygen, that would have raised carbon dioxide to lethal levels. It's also not plausible that the fires would burn for "years and years." Why wouldn't everything on the surface that could burn all burn within at most a week? Stuff underground in oxygen-poor caves and crevices might smolder for a long time, as with today's underground coal fires, but wouldn't remove much oxygen or add much CO2. That being said, it does seem likely that there were global fires at the end of the Cretaceous. When the secondary meteors kicked up by the main impactor re-entered all over the world, the whole sky would have lit up as if H-bombs were going off everywhere. But I doubt there was much on the surface to burn except live plants and animals. As Warren D Smith pointed out, any lakes of petroleum couldn't have lasted past the first lightning storm, especially not if oxygen levels were higher than today's.
Keith: You are not the first to think of this non-life-related source of oxygen; Kim Stanley Robinson's recent science fiction book _Aurora_ is built on exactly that water-splitting-hydrogen-escaping mechanism. --Michael On Tue, Jan 19, 2016 at 10:53 PM, Keith F. Lynch <kfl@keithlynch.net> wrote:
I've long been baffled by the claim that the free oxygen in the atmosphere came from photosynthesis. If the atmosphere started out neutral, then oxygen in the atmosphere must be balanced by reduced matter (biomass, peat, coal, oil, natural gas, etc.). It seems implausible that there's enough combustible stuff that burning it all would consume all the oxygen.
Note that carbon in carbonate rocks isn't reduced -- it's already combined with as much oxygen as it can be. Carbonate rocks can explain the disappearance of carbon dioxide from the atmosphere, but not the appearance of free oxygen.
The obvious alternative is that over many millions of years solar UV split water vapor into oxygen and hydrogen, and the hydrogen escaped into space. This would drop the sea level, but only by a few meters.
Yes, this is happening too slowly today to account for how much free oxygen there is. That's because the upper atmosphere, where there's plenty of solar UV, is very dry, due to the stratospheric cold trap. But the "iceball earth" theory says the ground-level climate oscillated for most of the Proterozoic eon between about -50 C and +50 C. During the warm periods, it seems likely that the upper stratosphere would have been warm and moist. And that's just when the oxygen appeared.
Am I really the first to think of this?
If I'm right, discovery of a planet with an oxygen atmosphere wouldn't necessarily imply that there is, or ever was, life on that planet.
As for Henry Baker's conjecture that massive fires at the end of the Cretaceous consumed much of the world's free oxygen, that would have raised carbon dioxide to lethal levels. It's also not plausible that the fires would burn for "years and years." Why wouldn't everything on the surface that could burn all burn within at most a week? Stuff underground in oxygen-poor caves and crevices might smolder for a long time, as with today's underground coal fires, but wouldn't remove much oxygen or add much CO2.
That being said, it does seem likely that there were global fires at the end of the Cretaceous. When the secondary meteors kicked up by the main impactor re-entered all over the world, the whole sky would have lit up as if H-bombs were going off everywhere. But I doubt there was much on the surface to burn except live plants and animals. As Warren D Smith pointed out, any lakes of petroleum couldn't have lasted past the first lightning storm, especially not if oxygen levels were higher than today's.
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At 07:53 PM 1/19/2016, Keith F. Lynch wrote:
I've long been baffled by the claim that the free oxygen in the atmosphere came from photosynthesis. If the atmosphere started out neutral, then oxygen in the atmosphere must be balanced by reduced matter (biomass, peat, coal, oil, natural gas, etc.). It seems implausible that there's enough combustible stuff that burning it all would consume all the oxygen.
Note that carbon in carbonate rocks isn't reduced -- it's already combined with as much oxygen as it can be. Carbonate rocks can explain the disappearance of carbon dioxide from the atmosphere, but not the appearance of free oxygen.
The obvious alternative is that over many millions of years solar UV split water vapor into oxygen and hydrogen, and the hydrogen escaped into space. This would drop the sea level, but only by a few meters.
There's a much bigger problem: Compare the Earth & Venus. Both are approx the same size; both have approx the same total amount of nitrogen in their respective atmospheres. The pressure at the bottom of the Earth's ocean is approx the same as the pressure on the surface of Venus. So, where did all of Earth's CO2 go? Or similarly, where did all of Venus's H2O go? The Earth's atmosphere is waaay too thin, relative to what it *should* be. It's possible that it lost some amount of atmosphere when the Earth's Moon was formed, but probably not enough. There had to be other mechanisms to get rid of more atmosphere.
participants (3)
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Henry Baker -
Keith F. Lynch -
Michael Kleber