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jlhredshift
2007-Sep-05, 10:05 PM
In a different thread I said:

IIRC it is conjectured that Venus may have had water very early on; within the first billion years or so. However, what I find even more interesting is the amount of carbon and oxygen on Venus. The total mass of the atmosphere of Venus and Earth respectively is 4.8 x 1020 and 5.1 x 1018 kilograms, 96.5% of which is CO2 on Venus. That is a 100 times more massive atmosphere on Venus, and correspondingly the surface pressure is 92 bars versus 1.014 bars respectively. That is a lot of carbon and oxygen by mass, whereas the moon is virtually devoid of carbon and we have a little by comparison. Why did Venus accumulate this disproportinate share?

source (http://burro.astr.cwru.edu/stu/advanced/venus.html)

There are web sites that baldly state that the amounts are equal, but give no references. Now, the proponderance of the Earth's is in the form of calcium carbonate, how can we compare? Are there sources for this calculation. I am personally very interested in knowing the global distribution and sedimentation rates of limestone on Earth. And, if the amount of CO2 are equal then it says something, I would think, about the environment of the initial formation of the two planets.

G O R T
2007-Sep-06, 12:25 PM
And, if the amount of CO2 are equal then it says something, I would think, about the environment of the initial formation of the two planets.

What would that be?

This article http://www.phys.lsu.edu/faculty/cjohnson/climate.html follows my own thinking, though I would have liked him to discuss the loss of hydrogen on Venus a bit. I feel this is important concerning the lack of water.

jlhredshift
2007-Sep-06, 12:39 PM
What would that be?

If the amount of carbon is the same on both planets then the environment of formation was at least similar in one more aspect. Can we prove that?



This article http://www.phys.lsu.edu/faculty/cjohnson/climate.html follows my own thinking, though I would have liked him to discuss the loss of hydrogen on Venus a bit. I feel this is important concerning the lack of water.


This is one of the web sites that baldly states equivalency without references. Otherwise, it is a very good review of the carbon cycle. Just because they say it on the internet does not make it so.

jlhredshift
2007-Sep-07, 03:47 AM
From The Great Paleozoic Crisis by Dr. Douglas H. Erwin

page 202 table 7.2:

Volume of various carbon reservoirs within the global carbon cycle. Numbers are in gigatons of carbon.

Carbonate sediment reservoir 6,000,000
Organic carbon reservoir 1,300,000
Gas hydrates 10,000
Dissolved organics in oceans 1,000
Oil, gas, and coal 5,000
Humus, peat, and detritus 2,000
Land biota 800
Marine biota 3
Atmosphere 700

(From Kvenvolden (1988), Arthur (1982) and other sources.)

This is how it was layed out in the book.

That equals 7,319,503 gigatons.

Now, if someone could help with the amount of carbon on Venus we might be able to say within a factor how close the two planets are.

Ronald Brak
2007-Sep-07, 04:16 AM
Venus has a surace area of about 460,000,000,000 square meters with about 90 tons of mostly CO2 atmosphere per square meter that comes to about 41,400,000,000,000 tons of CO2 or about 15,525,000,000,000 tons of carbon in the atmosphere. (But don't be too shocked if I've make a mistake in my sums somewhere.)

jlhredshift
2007-Sep-07, 04:23 AM
On another thread I had said:


I also do not know what the current global sedimentation rate is. There are specific locations that are known, and extrapolations can be made, but no precise knowledge. Also, CaCO3, calcium carbonate, has only one atom of carbon per molecule. Therefore, limestoneis mostly calcium and oxygen by mass. The seafloor is mostly basalt with a film, geologically speaking, of organic deposits and the continents are igneous basalts covered in SiAl, silicon and aluminum that are oxidized, sand, and a film of organic debris. The continental shelf is the primary production site for limestone and therefore is only a fraction of the Earth's surface. So,best guess, there is nowhere near enough carbon to duplicate the atmosphere of Venus.And I need to add all the sedimentary rocks from all ages on the continents that contain calcium carbonate and gas hydrates.

and I added the gas hydrate part.

In the book Venus II Bougher, Hunten, and Phillips; editors
on page 3
(for Venus)

The carbon content of the CO2 per g of planet is
(2.67 +- 0.30)x10-5 g. This is to be compared with a terrestrial inventory of (1.5 to 4.5) x10-5 g g-1 of carbon, where the lower figure is crustal carbon, mainly carbonate, and the higher figure includes mantle carbon.

Now, I am not certain how to equate or understand(planetary scientist speak) these pieces of information, and we have no way of knowing how much carbon is locked up on the surface of Venus with any certainity; and I am somewhat concerned about the accuracy of the table from Erwin's book published in 1993 (previous post).

.

jlhredshift
2007-Sep-07, 04:25 AM
Venus has a surace area of about 460,000,000,000 square meters with about 90 tons of mostly CO2 atmosphere per square meter that comes to about 41,400,000,000,000 tons of CO2 or about 15,525,000,000,000 tons of carbon in the atmosphere. (But don't be too shocked if I've make a mistake in my sums somewhere.)

Hi Ron'
Do I read that 15.525 gigatons?

My post that follows yours I was writing while you were posting.

jlhredshift
2007-Sep-07, 04:30 AM
Hi Ron'
Do I read that 15.525 gigatons?

My post that follows yours I was writing while you where posting.

Rats; that can't be right!

Help!!!!!

Ronald Brak
2007-Sep-07, 04:46 AM
Rats; that can't be right!

And we'd better make that 900 tons of CO2 per square meter for 155,250,000,000,000 tons of carbon or about 150,000 gigatons. (And just because I found one mistake doesn't mean I haven't made another.)

jlhredshift
2007-Sep-07, 04:51 AM
And we'd better make that 900 tons of CO2 per square meter for 155,250,000,000,000 tons of carbon or about 150,000 gigatons. (And just because I found one mistake doesn't mean I haven't made another.)

That's OK. I have no idea what the qoute from Venus II means. I don't know if we are reinventing the wheel or on uncharted ground. And, how do we take a guess as to how much is on the surface of Venus?

Ronald Brak
2007-Sep-07, 05:14 AM
I think, very broadly speaking, earth and venus have roughly comparable amounts of carbon.

jlhredshift
2007-Sep-07, 05:22 AM
I think, very broadly speaking, earth and venus have roughly comparable amounts of carbon.

A lot of people accept that, but I want more certaintude. If it is a fact, then it could be factored into planetary accreation models for our system.

Or, more simply, why would that be?: Accident or part of the planet formation process.

Ronald Brak
2007-Sep-07, 05:41 AM
Venus and earth presumably formed out of the same disk of dust and gas under similar circumstances. When we compare their densities we see they are similar and it's not unreasonable to suspect they were formed with have similar compositions. (It seems likely the moon was once part of the earth and the average density of the two is even closer to that of venus.)

Density:
Venus 5.204
Earth 5.515

jlhredshift
2007-Sep-07, 06:10 AM
Venus and earth presumably formed out of the same disk of dust and gas under similar circumstances. When we compare their densities we see they are similar and it's not unreasonable to suspect they were formed with have similar compositions. (It seems likely the moon was once part of the earth and the average density of the two is even closer to that of venus.)

Density:
Venus 5.204
Earth 5.515

The Big Splat (http://www.danamackenzie.com/big_splat_animation.htm) For the current consenus theory on the Moon's formation.

You said "it's not unreasonable to suspect", Ahh.. I want more, silly me.
I was just the ADS search engine and had no joy. See you tomorrow, goodnight and thanks.

jlhredshift
2007-Sep-07, 01:12 PM
Venus and earth presumably formed out of the same disk of dust and gas under similar circumstances. When we compare their densities we see they are similar and it's not unreasonable to suspect they were formed with have similar compositions. (It seems likely the moon was once part of the earth and the average density of the two is even closer to that of venus.)

Density:
Venus 5.204
Earth 5.515

In the book Venus Revealed; D. H. Grinspoon (author, trade) on page 149 as a footnote Grinspoon says:


Actually, the CO2 on Venus is almost twice as great as the equivalent amount on Earth and the amount of N2 on Venus is greater by a factor of three or four. These same numbers have been used to support opposing arguements! That they are "pretty close" has been used to argue that Venus and Earth were made from basically the same material, and that they are "significantly different" has been used to argue the opposite.

But, Grinspoon lists no specific reference for this statement.

neilzero
2007-Sep-07, 09:38 PM
Venus could have as much carbonate rock just below the surface as Earth. Free carbon may also be abundent in the crust of Venus. Earth's crust is about half silicon dioxide. Venus is likely simular and likely has many gigatons of other oxides. Most of the water that Venus had has likely been separated by ultraviolet in the outer atmosphere with the hydrogen escaping into space. The crust is likely too hot to have what we class as volitiles, but I think some hydrogen/metal hydrides are possible this hot, but may be rare as most metals are likely attached to oxygen. Venus does have significant amounts of water chemically combined with sulpheric acid vapor. Neil

jlhredshift
2007-Sep-08, 03:20 AM
Venus could have as much carbonate rock just below the surface as Earth. Free carbon may also be abundent in the crust of Venus. Earth's crust is about half silicon dioxide. Venus is likely simular and likely has many gigatons of other oxides. Most of the water that Venus had has likely been separated by ultraviolet in the outer atmosphere with the hydrogen escaping into space. The crust is likely too hot to have what we class as volitiles, but I think some hydrogen/metal hydrides are possible this hot, but may be rare as most metals are likely attached to oxygen. Venus does have significant amounts of water chemically combined with sulpheric acid vapor. Neil

My thought was that at the last volcanic resurfacing all carbonate would have been volatized, if there was any. The surface is a long term high temperature and pressure experiment. Some interesting compounds could be forged.

neilzero
2007-Sep-08, 02:10 PM
Calcium carbonate gives up it's carbon dioxide at about 900 degrees c at one atmosphere, perhaps much hotter at 90 atmosphere, but Venus lava is likely hotter than Earth lava, so likely you are correct; calcium carbonate is likely rare in the crust of Venus, but the resedue, calcium oxide, may be abundent. Calcium oxide boils at 2850 degrees c. Neil

jlhredshift
2007-Sep-11, 02:00 AM
Calcium carbonate gives up it's carbon dioxide at about 900 degrees c at one atmosphere, perhaps much hotter at 90 atmosphere, but Venus lava is likely hotter than Earth lava, so likely you are correct; calcium carbonate is likely rare in the crust of Venus, but the resedue, calcium oxide, may be abundent. Calcium oxide boils at 2850 degrees c. Neil

Just a thought and pure conjecture, but I wonder if at the time of last resurfacing lava buried carbonate and formed marble? Well, I think I am going to have to settle for Grinspoon's statement that Venus has twice as much Carbon as Earth, for now.