Oxygen formation in Earth water

[Fervent Freyja]

I am happiest when I have a rock to crack open with my rock hammer. In the past, in oil exploration, the drilling sample and cores from an exact depth were what was "real". The seismic sections that we relied on to select the spot to drill gave us data that we manipulated to create the profile. The validation of the seismic data came with a real sample from that data. In recent years I've been involved in about a dozen diamond anvil cell experiments. The results are what they are, but I feel a bit uneasy about extrapolating the results from that tiny universe to the interior of planets. The work that the consortium that is the Deep Carbon Observatory has revealed an Earth interior that would have been pure science fiction in the late '60s, when I first got interested in that.

Something that keeps things in perspective is the notion of multiple-working hypotheses. Even though carrying along old ideas is getting cumbersome, I don't reject them outright for the most part. I run with what works until there is a problem. Sometimes looking back at older ideas can provide insight. If I'm not editing a paper, I try to read 4 papers a day out of the 20-50 I download 6 days a week. I mention all this to show how hard it is to synthesize all the information into something coherent and insightful in a platform like this forum.

That sounds like a fun career!

 

[Mark Harder]

Totally agree with that. But they needed water to survive. Hence H2O, then how? o.o
idk if I am wrong here..

No, there are bacteria, called anaerobes, that can live in the absence of O₂. In fact, there are anaerobes, called obligate anaerobes, that cannot live in the presence of oxygen, i.e. it's a poison to them. The story, as related to me by several geology books, is that the Earth's early atmosphere was free of O₂ and all bacteria were anaerobes. When blue-green algae, which are really a species of bacteria, evolved they could take light as an energy source to split water (That takes a lot of energy, BTW) and evolve O₂. Once the oceans saturated with the stuff, it leaked into the atmosphere. It could be called the first mass extinction, since the free living obligate anaerobes in the oceans were killed by the O₂. Another consequence of the oxygenation event was that metal oxides, in particular iron oxides, were formed in the oceans; and being insoluble, precipitated onto the ocean floors. The rocks that formed from these possesses a characteristic texture of alternating red oxide interspersed with layers of ordinary sediments. This is the source of "banded iron formations" that constitute the massive and massively exploited ore deposits in Minnesota and Australia, I believe.

 

[CapnGranite]

Cyanobacteria is a phylum of bacteria. It's a good idea not to use the term "blue-green algae" at all.

 

[Jon Richfield]

Except that I think the evidence is increasing for the water-rich meteorite impacts not being necessary for the primary ocean formation. The volcanic activity suggests that deeper-seated water was brought to the surface by tectonic activity and the volcanism. The later bombardment by water-rich meteorites added to the water volume. I suppose there are two camps regarding the origin of the oceans, water-enstatite grains along with other mineral material, accreting to for the Earth and the group that invokes the bombardment as being the primary source of water. Since around 2011 and up to today, everybody I know and have spoken to favors the first model.

Well, up to a point, count me in as another "everybody".

My reservation is that I do not count bombardment as something that started only after accretion. As I see it, the early accretion lumps were part of the bombardments. However, that still leaves me supporting my original view (pre-1990s at least) that the post-accretion bombardment, including any residual items that still land about our ears today, are trivial tail-enders that couldn't really have played much of a role in enriching the planet with anything special, including organics and volatiles, except for a few rare, siderophilic elements such as iridium. The main difference is that in the last few billion years they might have undergone a loss of volatiles and some partitioning of isotopes etc.

Accordingly the bombardment as usually so described would not have been likely to have had much influence either on the formation of oceans or on the origin of life on Earth.

My $2000000-worth (to accommodate inflation since the Ordovician)

 

[jim meyer]

Bacteria.

My take on this ordeal: Prior to ocean formation the atmosphere had been mainly hydrogen, helium, methane, and ammonia. It is now believed that much of the water and rock had been locked into the crust, at the same time, during formation and that a small contribution was made by water-rich meteorite impacts. A lot of volcanic activity released water vapor into the atmosphere, along with carbon dioxide; which, then formed heavy clouds over the Earth that rained for a long time- eventually, forming the ocean. Water came first, not oxygen.

Bacteria is life-one of three kinds of life. This form of life might have done the job-or it might have been done by chemistry not involving life at all. Or maybe a little of both. The point is CO2 locked up in rocks was in the atmosphere early on and there is a lot of CO2 locked up in rocks.

 

[jim meyer]

I do think you are right. It may be more right to say that water was locked into the crust as material accreted and later impacts may have contributed some.

Still, this explanation doesn't satisfy me. Something is off. Looking at all the advancements we have made (look at what we can describe about the universe) and comparing it to how little we can explain about the formation of the early Earth makes me uncomfortable.

I wonder if anyone has considered buoyancy in these models? It seems to me water will tend to rise to the surface because the crust is much denser and will tend to sink in water. I know water fills holes in the crust but how deep down do conditions exist for holes to develop?

 

[Jon Richfield]

Well let's not nitpick-I agree photosynthesis has added O2 to the atmosphere. My point is free oxygen has always been in the atmosphere at about 10E18kg or so. The fact that much more CO2 was in the early atmosphere(CO2 now in rocks)and dwarfs the other gases. This is not known and I just want you to do a calculation of how much CO2 rocks like calcite, dolomite and other rocks have absorbed from the early atmosphere. Not rocket science in any way.

Not much to ask I suppose, but some of your views are confusingly expressed, to put it diplomatically. Chemically and biologically speaking for example, CO2 is not regarded as free oxygen, and the point is not purely academic, as you will find out if you try inhaling some. I agree that the early Earth's atmosphere would have contained plenty of CO2 until the rocks cooled down to something like 200C. But that is not free O2, and its difference from free O2 would affect all sorts of things from physical atmospheric characteristics to the precipitation of huge quantities of silica from silicates. Photosynthesis of free O2 in large quantities was one of the great pollution events in the (pre)history of the planets where there had never before been more than traces of anything so violently destructive or toxic before. Not merely whole species, but whole ecological complexes were wiped out within a few million years, and probably repeatedly at that during the transition ages.

If that is nit-picking, make the most of it.

Incidentally, while you are at doing your calculations, you might have some fun calculating how much CO2 is dissolved in the ocean right now, compared to how much we have in our atmosphere, and working out how it got there and how long it has been there, and what is important about it.

The natural world is full of surprises.

 

[Jon Richfield]

I wonder if anyone has considered buoyancy in these models? It seems to me water will tend to rise to the surface because the crust is much denser and will tend to sink in water. I know water fills holes in the crust but how deep down do conditions exist for holes to develop?

As it happens, yes, people do consider buoyancy, but in the early planet temperature was far more important. Such water as wasn't firmly bound tended to gasify dramatically, and even today volcanic clouds contain lots of steam apart from their dust. The first oceans probably rained out of volcanic clouds long before they formed any noticeable puddles.

As for holes in the crust, below the top few km they tend to get squoze shut pretty quickly for the simple reason that most rock is plastic under pressure and at temperatures that superheat steam.

Water is generally a very scarce component of our planet and you will find hardly any even in the deep crust, let alone in the mantle. Actually, I did read somewhere of recent evidence that there might be more water in special regions of the mantle I think it was, than in the current oceans, but that still is small beer (if you will excuse the expression) compared to the overall volume and mass of the mantle and crust. Any volcano tapping such a source however, could do a lot of raining, it seems.

 

[Jon Richfield]

Bacteria is life-one of three kinds of life. This form of life might have done the job-or it might have been done by chemistry not involving life at all. Or maybe a little of both. The point is CO2 locked up in rocks was in the atmosphere early on and there is a lot of CO2 locked up in rocks.

Actually that is by no means the point. How many kinds of life bacteria are, is a matter of definition. A lot of folks like to think of them as two kinds, and some prefer more. To argue one way or another one needs to explain first which purposes your classification serves. None of us has done that just here and now, because it does not address the original question.

But photosynthetic bacteria that process CO2 generally dissolve it from the air or use it dissolved in water. In other words, much as plants do. To extract it from rock is not vanishingly rare, but generally is a specialist adaptation to particular ecologies. A bit of a curiosity if you like.

 

[jim meyer]

Not much to ask I suppose, but some of your views are confusingly expressed, to put it diplomatically. Chemically and biologically speaking for example, CO2 is not regarded as free oxygen, and the point is not purely academic, as you will find out if you try inhaling some. I agree that the early Earth's atmosphere would have contained plenty of CO2 until the rocks cooled down to something like 200C. But that is not free O2, and its difference from free O2 would affect all sorts of things from physical atmospheric characteristics to the precipitation of huge quantities of silica from silicates. Photosynthesis of free O2 in large quantities was one of the great pollution events in the (pre)history of the planets where there had never before been more than traces of anything so violently destructive or toxic before. Not merely whole species, but whole ecological complexes were wiped out within a few million years, and probably repeatedly at that during the transition ages.

If that is nit-picking, make the most of it.

Incidentally, while you are at doing your calculations, you might have some fun calculating how much CO2 is dissolved in the ocean right now, compared to how much we have in our atmosphere, and working out how it got there and how long it has been there, and what is important about it.

The natural world is full of surprises.

Well I didn't mean to say CO2 was free oxygen if that is what you mean. The CO2 molecule is mostly oxygen and photosynthesis or inorganic chemistry can free the oxygen therein. There is a lot more CO2 in the ocean than in the atmosphere. Still more than 90% of all the CO2 on our lovely planet is locked in rocks.

 

[CapnGranite]

http://www.astrobio.net/news-exclusive/scientists-detect-evidence-oceans-worth-water-Earth's-mantle/
SCIENTISTS DETECT EVIDENCE OF ‘OCEANS WORTH’ OF WATER IN EARTH’S MANTLE

http://science.sciencemag.org/content/344/6189/1265
This is the original paper, from 2014, but is still locked

 

[Jon Richfield]

http://www.astrobio.net/news-exclusive/scientists-detect-evidence-oceans-worth-water-Earth's-mantle/
SCIENTISTS DETECT EVIDENCE OF ‘OCEANS WORTH’ OF WATER IN EARTH’S MANTLE

http://science.sciencemag.org/content/344/6189/1265
This is the original paper, from 2014, but is still locked

Thanks yes, that was the one, though I can't remember whether I read the original or a popular version. But the abstract is adequate for our need here for the moment.
Mind you, it is an observation that opens intriguing lines of speculation. But they are rather academic. I bet that when we get to the technological stage of development that permits us to dig so deep, we'll find that the water is too dilute and too salty to be worth extracting.
But then again, if we could get down there, just extracting the water would be an energetically profitable operation...
Enormously, explosively profitable...
Hmmm...
And think about the mineral impurities -- if we can find water so deep, maybe we could find iridium so shallow...
$$$$$$$$$$$$$$$$!

 

[jim meyer]

Well I didn't mean to say CO2 was free oxygen if that is what you mean. The CO2 molecule is mostly oxygen and photosynthesis or inorganic chemistry can free the oxygen therein. There is a lot more CO2 in the ocean than in the atmosphere. Still more than 90% of all the CO2 on our lovely planet is locked in rocks.

 

[Fervent Freyja]

No, there are bacteria, called anaerobes, that can live in the absence of O₂. In fact, there are anaerobes, called obligate anaerobes, that cannot live in the presence of oxygen, i.e. it's a poison to them.

Oh, but if you remember, oxygen is poisonous to most lifeforms anyway, especially humans...

From what I recall O₂ levels in the GI tract range from 2-8% and some obligate anaerobes make it a home!

 

[CapnGranite]

I'm not sure that 90% of CO2 per se is "locked in rocks". Large amounts can be locked up in clathrates, but rocks don't typically lock up CO2. This paper shows the complexity of carbonate species in the Earth system:
http://advances.sciencemag.org/content/2/10/e1601278.full
The fate of carbon dioxide in water-rich fluids under extreme conditions

Another interesting paper is:
http://dge.stanford.edu/SCOPE/SCOPE_16/SCOPE_16_1.5.05_Siegenthaler_249-257.pdf
13C/12C Fractionation during CO2 Transfer from Air to Sea

and another:
http://www.columbia.edu/~vjd1/carbon.htm
Carbonate Rocks

1. Carbon dioxide is removed from the atmosphere by dissolving in water and forming carbonic acid

CO2 + H2O -> H2CO3 (carbonic acid)
2. Carbonic acid is used to weather rocks, yielding bicarbonate ions, other ions, and clays

H2CO3 + H2O + silicate minerals -> HCO3- + cations (Ca++, Fe++, Na+, etc.) + clays
3. Calcium carbonate is precipitated from calcium and bicarbonate ions in seawater by marine organisms like coral

Ca++ + 2HCO3- -> CaCO3 + CO2 + H2O
the carbon is now stored on the seafloor in layers of limestone

 

[CapnGranite]

https://deepcarbon.net/feature/study-suggests-earth%E2%80%99s-carbon-originated-planetary-smashup#.WAgu6pMrL-a
The challenge is to explain the origin of the volatile elements like carbon that remain outside the core in the mantle portion of our planet,”

https://deepcarbon.net/content/dco-march-2013-press-release#.WAgvnZMrL-Z
Carbon: Quest Underway to Discover its Quantity, Movements, Origin, and Forms in Deep Earth
A small fraction of Earth's carbon is in its atmosphere, seawater and top crusts. An estimated 90% or more is locked away or in motion deep underground — a hidden dimension of the planet as poorly understood as it is profoundly important to life on the surface.

So, it might be correct to say that 90% of carbon is tied up in various ways in the rocks, but not CO2

 

[Jon Richfield]

I'm not sure that 90% of CO2 per se is "locked in rocks". Large amounts can be locked up in clathrates, but rocks don't typically lock up CO2. This paper shows the complexity of carbonate species in the Earth system:
http://advances.sciencemag.org/content/2/10/e1601278.full
The fate of carbon dioxide in water-rich fluids under extreme conditions

Good material and much thanks for the URLs. I still haven't read much of the material because I am playing hookey as things are, but one comparatively small, but actually highly important, reservoir is CO2 insecurely "locked" into solution in the deep sea. It has accumulated in deep layers under pressure, not all of it from the atmosphere. There is more than enough to kill us all if it were suitably released. I draw everyone's attention to the history of lake Nyos (https://en.wikipedia.org/wiki/Lake_Nyos) and leave readers unfamiliar with the history and mechanisms, to wonder why it has not yet happened.

And furthermore, given that its escape is inevitable, work out when it can no longer be averted.

As for "locking in rocks" in other forms than as carbonates or at an even remoter stretch, as organic compounds or inorganic carbides, I'd be surprised if that were important in any practical way. I cannot think of any sort of rock that can retain molecular CO2 except for bubbles in glassy volcanic rocks or pumice, and that is a pretty insignificant fraction, and one that does not generally escape catastrophically except as volcanic explosions. Lots of fun and amazingly photogenic, but percentage-wise trivial.

Non-gaseous forms of carbon (as opposed to CO2) in the Earth are mostly carbonates and organic compounds in the upper crust, but in the lower crust and mantle, carbides and free carbon would dominate, and though I have no information on them, I would bet a few cases of beer that they dominate the planetary carbon reserves. After all, our surface and shallow supplies are mercifully tiny.