Is Venus supposed to have an atmosphere?

[Rolci]

Imagine for a moment that we have no knowledge of a Venusian atmosphere simply due to lack of observation. If anyone were to theorize ANY kind of atmosphere for Venus, how likely do you think the idea would be supported by the scientific community? Consider the questions that would arise and the arguments against it that would need reconciliation:

- Where is it supposed to have come from. The more the total atmospheric mass the harder to find plausible explanations for an origin.

- What would keep it in place? Venus has a smaller mass than Earth, meaning a weaker gravitational field, so if there were an atmosphere of any kind it would have to be thinner than on Earth.

- Even more so as Venus is closer to the Sun, which means that the atmosphere is hotter. Much hotter. In fact, it is 2,5 times hotter than on Earth. In simple terms this means that the molecules making up the atmosphere are hitting each other with some crazy speed, building up some crazy pressure, which would push out a huge percentage of the atmosphere into outer space, and the weak gravitational field wouldn't be enough to counteract this force, leaving a hot but thin atmosphere.

- Being closer to the Sun also means a considerably stronger solar wind than on Earth. This normally would't be much of a problem, except Venus has no magnetosphere, so the atmosphere should be blown away like a ball of hair in front of a hair-dryer. Especially that close to the Sun.

- Let's not forget the effects of centrifugal forces on the surface which tend to throw off any atmosphere into outer space. I'm aware of the low rotational speed of Venus TODAY, but millions and billions of years ago it was much quicker, preventing the formation and build-up of an atmosphere. Wherever the atmosphere is supposed to have come from, it would've had a hard time building up from a thin atmosphere into a thick one as the initial thin atmosphere would be thrown off, blown away etc., all that I mentioned above.

As you can see one would have a hard time supporting the idea that there should be an atmosphere. Yet we are told that not only is there some atmosphere, we are told that, despite being so hot that Zinc would be BOILING on the surface, it is so thick and heavy that the surface pressure is 90 times higher than on the heavier, magnetically shielded Earth, further away from the Sun. Sure thing.

[Peter B]

Are you trying to suggest that Venus doesn't have an atmosphere?

If so, you'll have to argue against evidence which was discovered by astronomers as early as the 18th century - for example:

Schröter found when the planet was a thin crescent, the cusps extended through more than 180°. He correctly surmised this was due to scattering of sunlight in a dense atmosphere. Later, American astronomer Chester Smith Lyman observed a complete ring around the dark side of the planet when it was at inferior conjunction, providing further evidence for an atmosphere.

Likewise, you'd have to explain what's been discovered by American, Soviet and European spacecraft.

[Rlyeh]

You realize the gravity of Venus isn't that much lower than Earth? Venus is has over 90% of Earths gravity.

http://www.universet...avity-on-venus/

Edit: Mars is even less massive and has an atmosphere. The moon of Saturn, Titan, less mass than Mars, also has a dense atmosphere.

Edited February 4, 2014 by Rlyeh

[Davros of Skaro]

Does this answer your question?

[spacecowboy342]

Venus surface temperature being as much higher than earth's as it is is not due to being closer to the sun, but to it's atmosphere and a runaway greenhouse effect. Venus surface temp is higher than Mercury's which is much closer to the sun. We can only speculate about what Venus atmosphere may have been like before the event that caused it's retrograde rotation and may have killed it's magnetic field and entirely resurfaced the planet.

[sepulchrave]

Just too add to what others have said, you do realize that both the US and the Soviets have sent probes into the atmosphere of Venus, and the Soviet Venera program actually managed to land probes on the surface of Venus and send back colour photos before being destroyed by the heat and pressure (after about 2 hours)?

[ChrLzs]

Good grief. 3 words..

Apply..

Scientific..

Method..

[psyche101]

Imagine for a moment that we have no knowledge of a Venusian atmosphere simply due to lack of observation. If anyone were to theorize ANY kind of atmosphere for Venus, how likely do you think the idea would be supported by the scientific community? Consider the questions that would arise and the arguments against it that would need reconciliation:

Telescopes? The biggest and baddest cannot make out a single surface feature. It is probably just my imagination, but when I look at it through my 10" Dob, it looks like one big bad storm all the time.

We can see features on the moon, mars like craters, ice caps, and ridges, remember the Martian Canali that spawned so many rumours. Venus looks solid - dense atmosphere.

- Where is it supposed to have come from. The more the total atmospheric mass the harder to find plausible explanations for an origin.

The atmosphere? Same place as ours. Comets, volcanoes, accretion etc.

Why do you think it would be different for Venus than it was for Earth?

- What would keep it in place? Venus has a smaller mass than Earth, meaning a weaker gravitational field, so if there were an atmosphere of any kind it would have to be thinner than on Earth.

Not much, Venus is pretty close to being the same size as Earth. What keeps the Atmosphere in place? Good question because indeed, Venus does not have a magnetic field. We do not really know why. Maybe lack of convection in the mantle, maybe the slow rotation is to blame.

Some of the atmosphere is lost to space. Even though it has a thick and heavy atmosphere far more dense and compacted than earth, it only has four times as much nitrogen. The atmosphere of Venus is 90 times more dense than that on Earth and it is made of 96.5% of CO₂ and a 3% of nitrogen. The CO₂ on Earth is stored on calcite type rocks, not in the atmosphere, and if we would convert the CO₂ on these rocks into atmospheric CO₂ it would amount to the same amount of CO₂ that there is on Venus' atmosphere.

Further reading:

It is instructive to compare the evolution of the Earth's atmosphere to that of its neighbor planets Venus and <a name="marker=135317" style="color: rgb(0, 0, 0); font-family: Palatino; font-size: 16px; text-align: justify; background-color: rgb(255, 255, 255);">Mars. All three planets presumably formed with similar assemblages of elements but their present-day atmospheric compositions are vastly different ( See Atmospheres of Venus, Earth, and Mars ). Venus has an atmosphere ~100 times thicker than that of Earth and consisting mostly of CO2. Because of the greater proximity of Venus to the Sun, the temperature of the early Venus was too high for the outgassed water to condense and form oceans (see section 7.5 for further discussion). As a result CO2 remained in the atmosphere. Water vapor in Venus's upper atmosphere photolyzed to produce H atoms that escaped the planet's gravitational field, and the O atoms left behind were removed by oxidation of rocks on the surface of the planet. This mechanism is thought to explain the low H2O concentrations in the Venusian atmosphere. On Earth, by contrast, the atmosphere contains only 10-5 of all water in the surface reservoirs (the bulk is in the oceans) so that loss of water to outer space is extremely slow and is compensated by evaporation from the oceans.

LINK

Interesting side fact - because of these harsh conditions on Venus. Co2 is compressed into a supercritical state - something between gas and liquid, as a gas it can permeate all areas, but it can dissolve just like a liquid - the entire surface is covered in this mass.

- Even more so as Venus is closer to the Sun, which means that the atmosphere is hotter. Much hotter. In fact, it is 2,5 times hotter than on Earth. In simple terms this means that the molecules making up the atmosphere are hitting each other with some crazy speed, building up some crazy pressure, which would push out a huge percentage of the atmosphere into outer space, and the weak gravitational field wouldn't be enough to counteract this force, leaving a hot but thin atmosphere.

Not as close as you are making out here.

Venus is 0.72 AU from the Sun, we are obviously 1 AU out. So then the minimum separation between Venus and the Earth is 0.28 AU, or about 40 million kilometres when we reside 149,600,000 km from the Sun.

Not that big a deal. Remember, Venus is considered to be in our Sun's habitable zone.

- Being closer to the Sun also means a considerably stronger solar wind than on Earth. This normally would't be much of a problem, except Venus has no magnetosphere, so the atmosphere should be blown away like a ball of hair in front of a hair-dryer. Especially that close to the Sun.

That is right Venus does not have a magnetic field. We are not sure why, maybe because of the lack of convection in the mantle, maybe because of the slow rotation. But Venus does have an induced magnetosphere formed by the Sun's magnetic field carried by the solar wind.

Like so:

In the upper atmosphere, hydrogen and oxygen are being created by the dissociation of neutral molecules from ultraviolet radiation. And indeed during this process some of those elements are carried away.

- Let's not forget the effects of centrifugal forces on the surface which tend to throw off any atmosphere into outer space. I'm aware of the low rotational speed of Venus TODAY, but millions and billions of years ago it was much quicker, preventing the formation and build-up of an atmosphere. Wherever the atmosphere is supposed to have come from, it would've had a hard time building up from a thin atmosphere into a thick one as the initial thin atmosphere would be thrown off, blown away etc., all that I mentioned above.

Rather than building up, perhaps building down might be a better analogy. Lighter gases are stripped of to an extent, leaving the heavier ones to settle, which is what we see today on Venus. CO₂ is a greenhouse gas, and the atmosphere of Venus is almost totally comprised of CO₂.

As mentioned above, the entire surface of the planet is covered in supercritical CO₂.

As you can see one would have a hard time supporting the idea that there should be an atmosphere. Yet we are told that not only is there some atmosphere, we are told that, despite being so hot that Zinc would be BOILING on the surface, it is so thick and heavy that the surface pressure is 90 times higher than on the heavier, magnetically shielded Earth, further away from the Sun. Sure thing.

Not considering that it is very different to earth and as such is bound to offer different characteristics. Did you know it has a retrograde orbit? Neptune and Venus are the only two planets int he solar system to do so.

You know the Russians have sent like ten probes there now? Soft landings on all, and up to 110 minutes of footage from some missions.

Edited February 5, 2014 by psyche101

[spacecowboy342]

Pluto has a retrograde rotation too. I know it got kicked out of the planet club but it'll always be a planet to me

[psyche101]

Pluto has a retrograde rotation too. I know it got kicked out of the planet club but it'll always be a planet to me

LOL, Poor old Pluto, it's way of the scale! Have a look at the orbits Actually thanks for focusing on that, I see that I said retrograde orbit above, I meant to say rotation.

Also, most moons that are asteroid sized are retrograde too

Edited February 5, 2014 by psyche101

[Rolci]

Thanks for the replies, maybe I should've started with relevant bits of my background like I've been interested in astronomy from a young age and that I've been familiar with all the bits you guys picked up from wikipedia for a couple of decades now, from books of course.

Naturally I was aware of alleged space probes and their alleged reports. I'm not saying they are lies or not, faked or not, all I say is I don't have personal experience, I have not done measurements. If some other person or agency says they have, you can take it on blind faith or choose to reject it, like many are debating moon landings, while others are still insisting that the Earth is flat. Conspiracies do exist and groups of people do have different agendas, many of them global, and they would have the masses believe this or that and I do not feel that I can personally ascertain with 100% accuracy what's true what's lies. So for this reason I'd like to put the space probes aside for a moment.

I was also aware of the composition of the atmosphere and the greenhouse effect and the highest surface temp in the solar system and the retrograde rotation. Also the induced magnetosphere (which in my opinion has negligible effects).

In spite of being aware of all the above I thought it would be fruitful investigating the issue, if not for anything else, then to clear up a few basic things that, not to my surprise, NO ONE here has addressed so far, which is kind of sad. Why? Because the truly ARE the basics, as opposed to all the irrelevant stuff above like retrograde rotation (which let's admit shouldn't affect the formation of an atmosphere) or ChrLzs's non-constructive comment. It's like having kids do brainstorming in a classroom.

I was rather hoping (naively) to discuss things like, what's the theoretical upper limit for the mass of atmosphere a planet of given mass and radius (you want the surface gravity) can hold? Shouldn't there be some kind of formula? We could start from an assumption that the Earth is holding the maximum amount it can, and work from there. I would've loved to hear someone mention that MAYBE Venus is holding normal amount but Earth's is extra-thin because of dissolution of gases in the oceans. Never mind. So let's assume it's holding all it can. What happens if you reduce the mass? Lower gravity, light gases from upper atmosphere escape. What happens if you move it closer to the Sun? Temp rises, volume of atmosphere expands, top layers are pushed further out into space, more mass shed. Also stronger solar wind constantly blows gases of the upper atmospheric perimeter perpendicular to Sun-planet line, even if there is constant supply from volcanoes, so a balanced equilibrium develops. Now strip the magnetosphere. What happens? Drastic loss of the remaining thin atmosphere, possibly a total loss.

So this unprotected small piece of rock manages to support an atmosphere 90 times denser than the protected Earth can. I invite explanations. Or maybe there is a formula out there that I'm not aware of, and Venus's atmosphere is normal and ours is super-thin. The oceans can only dissolve certain gases, and only so much. Furthermore we've had and still have active volcanoes, so is our atmosphere getting thicker? Are surface atmospheric pressures constantly rising worldwide? Not that I have heard. If Venus's 90-bar atmosphere is normal, shouldn't Mars have like a 50-bar atmosphere or something? Yeah, I know, dead planet, slow solar erosion. But where is our 200-bar atmosphere? And if 90 bars is normal for Venus, how much would it be able to hold WITH a magnetic field? 150 bars? With the surface temp being a fourth of what it is (183K = -90 degrees, which we've had n Earth)? 600 bars? http://tinyurl.com/snxmf Check the picture on the right. What do you think that would do to rocks and mountains (large rocks) on the surface? It would literally level the surface. And that's normal? For a small rocky planet? So that's what Mars would have if it were volcanically active? Seriously?

So there are a few questions here still. The least the main question deserves is some basic formula for an upper limit for atmospheric mass that a planet or any large object in space can hold and carry. It should be dependent on the composition as well, if it's mainly heavy gases then a lot of mass can stay close to the surface where gravity is still strong. Let's say we have a planet of a mass of 10²⁵ kg and a radius of 10.000 km. No stars around with solar wind, say it has a distant orbit around a brown dwarf. No planetary magnetic field. Ho much oxygen can it carry with it in a constant, stable fashion, max? I realize if it were an empty universe then even a piece of rock would theoretically be able to hold an infinite mass of gases around it, being the only gravitational centre, so we need some force constantly stripping it, like some kind of a drag from resistance from an ether, or solar wind (which is the same in principle, both based on relative movement). So let's add solar wind to the mix, choose any value. Can we have the formula?

Edited February 6, 2014 by Rolci

[Peter B]

Thanks for the replies, maybe I should've started with relevant bits of my background like I've been interested in astronomy from a young age and that I've been familiar with all the bits you guys picked up from wikipedia for a couple of decades now, from books of course.

Please do not assume that because I quoted Wikipedia I did not know anything about Venus's atmosphere prior to that. The Wikipedia quote matched what I knew (like you, from books) and was a quote you could verify the existence of. Based on what you say below about conspiracies, I wonder what you might say if I tried to quote from a book you didn't have access to?

Naturally I was aware of alleged space probes and their alleged reports. I'm not saying they are lies or not, faked or not, all I say is I don't have personal experience, I have not done measurements. If some other person or agency says they have, you can take it on blind faith or choose to reject it, like many are debating moon landings, while others are still insisting that the Earth is flat. Conspiracies do exist and groups of people do have different agendas, many of them global, and they would have the masses believe this or that and I do not feel that I can personally ascertain with 100% accuracy what's true what's lies. So for this reason I'd like to put the space probes aside for a moment.

Seriously, what sort of conspiracy would involve scientists from multiple nations trying to convince "the masses" that Venus has an atmosphere when it doesn't? Particularly when anyone with a telescope can look at Venus and verify what astronomers have seen for 200+ years?

I was also aware of the composition of the atmosphere and the greenhouse effect and the highest surface temp in the solar system and the retrograde rotation. Also the induced magnetosphere (which in my opinion has negligible effects).

In spite of being aware of all the above I thought it would be fruitful investigating the issue, if not for anything else, then to clear up a few basic things that, not to my surprise, NO ONE here has addressed so far, which is kind of sad. Why? Because the truly ARE the basics, as opposed to all the irrelevant stuff above like retrograde rotation (which let's admit shouldn't affect the formation of an atmosphere) or ChrLzs's non-constructive comment. It's like having kids do brainstorming in a classroom.

I was rather hoping (naively) to discuss things like, what's the theoretical upper limit for the mass of atmosphere a planet of given mass and radius (you want the surface gravity) can hold? Shouldn't there be some kind of formula?

If that was the case, why didn't you raise these questions in your original post? You can hardly blame people for not discussing issues you never raised in the first place.

...

So this unprotected small piece of rock manages to support an atmosphere 90 times denser than the protected Earth can. I invite explanations. Or maybe there is a formula out there that I'm not aware of, and Venus's atmosphere is normal and ours is super-thin.

With the greatest of respect, this might have been a better place to start your inquiries, rather than calling into question a couple of centuries of investigation of Venus.

The oceans can only dissolve certain gases, and only so much. Furthermore we've had and still have active volcanoes, so is our atmosphere getting thicker? Are surface atmospheric pressures constantly rising worldwide? Not that I have heard. If Venus's 90-bar atmosphere is normal, shouldn't Mars have like a 50-bar atmosphere or something? Yeah, I know, dead planet, slow solar erosion. But where is our 200-bar atmosphere?

I'm no geologist, but isn't it the case on Earth that gases are dissolved into water and incorporated into rocks which are eventually subducted into the mantle? In other words, doesn't plate tectonics do the job of maintaining an atmospheric equilibrium on Earth, and the lack of water and plate tectonics on Venus is what means outgassed carbon dioxide stays in the atmosphere? Is there a geologist in the house?

So there are a few questions here still. The least the main question deserves is some basic formula for an upper limit for atmospheric mass that a planet or any large object in space can hold and carry. It should be dependent on the composition as well, if it's mainly heavy gases then a lot of mass can stay close to the surface where gravity is still strong. Let's say we have a planet of a mass of 10²⁵ kg and a radius of 10.000 km. No stars around with solar wind, say it has a distant orbit around a brown dwarf. No planetary magnetic field. Ho much oxygen can it carry with it in a constant, stable fashion, max? I realize if it were an empty universe then even a piece of rock would theoretically be able to hold an infinite mass of gases around it,being the only gravitational centre, so we need some force constantly stripping it, like some kind of a drag from resistance from an ether, or solar wind (which is the same in principle, both based on relative movement). So let's add solar wind to the mix, choose any value. Can we have the formula?

Fair enough question I imagine, and I'm interested to hear the answer too. But as I said above, why did you lead with your "Sure thing" sarcasm in your OP rather than simply ask these questions?

[+Noteverythingisaconspiracy]

Thanks for the replies, maybe I should've started with relevant bits of my background like I've been interested in astronomy from a young age and that I've been familiar with all the bits you guys picked up from wikipedia for a couple of decades now, from books of course.

Naturally I was aware of alleged space probes and their alleged reports. I'm not saying they are lies or not, faked or not, all I say is I don't have personal experience, I have not done measurements. If some other person or agency says they have, you can take it on blind faith or choose to reject it, like many are debating moon landings, while others are still insisting that the Earth is flat. Conspiracies do exist and groups of people do have different agendas, many of them global, and they would have the masses believe this or that and I do not feel that I can personally ascertain with 100% accuracy what's true what's lies. So for this reason I'd like to put the space probes aside for a moment.

What is, in your mind, the reason why anybody would try to fake what we know about Venus ?

So far 3 spaceagencies have launched probes to Venus (NASA, ESA and the Soviet Union), are they all lying?

In short you are saying that you dont believe in anything that you havent seen and measured yourself ?

[Waspie_Dwarf]

In short you are saying that you dont believe in anything that you havent seen and measured yourself ?

I have never met Rolci.

Since I have no personal experience of him I can apply his "logic" and I don't have to accept that he exists.

Since he doesn't exist, this thread doesn't exist.

As I don't accept this thread exists I don't have to get involved.

Of course observation disproves my conjecturer but if Rolci can casually reject observation because he doesn't like it then so can I.

Rather a blessing really given that it has the single daftest opening post I have seen to any thread in this section for a long time.

Edited February 6, 2014 by Waspie_Dwarf

[Merc14]

I never thought a discussion of Venus and some of its oddities, would become a conspracy thread. Bascially, until rolci sends his own spacecraft to Venus and reads its findings in his home built mission control he won't believe anything said by anyone regarding the nature of the planet Venus. What kind of mind works in this way?

Edited February 6, 2014 by Merc14

[Waspie_Dwarf]

What kind of mind works in this way?

When I don't understand something I conclude that my knowledge is incomplete.

It seems that some people, when they don't understand something, conclude that everyone else must be lying. If I were to say what this leads me to conclude it could possibly be construed as a personal attack, so I will lead others to draw their own conclusions.

Observation trumps hypothesis EVERY time. If the hypothesis does not fit the observation then the hypothesis must be either incomplete or wrong.

That Venus has an atmosphere is beyond question. The only logical conclusion is that Rolci's understanding of the problem is incomplete or wrong. If science can not explain the atmosphere of Venus then science's understanding of Venus' atmosphere must be incomplete or wrong.

All the while that Rolci protests the atmosphere of Venus will remain, not caring whether Rolci believes in it or not.

The good thing about science is that it's true whether or not you believe in it.

- Neil deGrasse Tyson

[Rolci]

Funny how everyone focuses (or rather gets caught up) on any implied/suggested conspiracy theories. While I could indeed contribute to such a discussion with serious thoughts, there is a reason why I posted this topic in the astronomy section.

Someone picked up on dissolution of gases into water. The real question is, can the oceans dissolve any more? I think if they could they would've absorbed all they could throughout the billions of years. If they are constantly doing so then why aren't we running out of atmosphere? Is it possible that all the factors that reduce the amount are in exact balance with the ones that increase it (like volcanic activity)? A perfect balance sounds like an unlikely scenario. If the Earth is indeed capable of holding more, then why hasn't it been building up to hundreds of bars throughout the aeons? Or if something counteracts that why hasn't such a force taken over and stripped it all? The only way I can accept a perfectly unchanging amount is by assuming that it's not being eroded and there is no gain, (which there is from still active volcanoes), otherwise I would be looking for a balancing mechanism, the most obvious being the possibility that this is all we can carry, if more is produced the upper layers are pushed out and lost. But if this is all the Earth can have, the question is still, why can the unprotected Venus have more, not just a little more, almost 100 times more? It just sounds absurd.

Still waiting for that formula that everyone must know but they're teasing me for being so uninformed. Is it too much to ask for? It's always seemed the way to go: you observe (e.g. different planets take different amount of time to orbit the Sun), and find out why, the mechanism, look for the formula (Kepler's third law). So, different planets have different amounts of atmosphere and they are exactly what they are and couldn't be any different because... There is a scientific answer, right? But if everyone here is so damn smart and I'm the only dumb one, why hasn't anyone educated me yet? I've asked a simple and legitimate science question in the science forum section. How hard can it be to provide the obvious-to-everyone answer? Do I have to wait until page 20? Yahoo Answers is beginning to seem a more promising prospect.

[ninjadude]

Still waiting for that formula that everyone must know but they're teasing me for being so uninformed. Is it too much to ask for? It's always seemed the way to go: you observe (e.g. different planets take different amount of time to orbit the Sun), and find out why, the mechanism, look for the formula (Kepler's third law). So, different planets have different amounts of atmosphere and they are exactly what they are and couldn't be any different because... There is a scientific answer, right?

Gee this took about 5 min. Atmospheric escape https://en.wikipedia.org/wiki/Atmospheric_escape Pretty much everything you wanted to know.

[ChrLzs]

The real question is, can the oceans dissolve any more?

NO, that isn't 'the real question' at all - you have conflated a whole number of things, many of which are complicated and inter-related, and want to simplify it down to a single easy equation, or a one line sentence?

That is simply ridiculous. It's like asking relativity to be fully explained in one sentence.

It just sounds absurd.

So everything you don't understand sounds absurd? Fair enough (it's a very common logical fallacy..). Me, if I don't understand complex concepts, I go and do a LOT of research. Many things are counter-intuitive or do not comply with normal experience (which is where 'absurdity' comes from). So you need to learn about them. PROPERLY.

Hint - that won't happen at youtube or by random googling.

Still waiting for that formula

Don't hold your breath.

[spacecowboy342]

Alleged space probes?

[Peter B]

Funny how everyone focuses (or rather gets caught up) on any implied/suggested conspiracy theories. While I could indeed contribute to such a discussion with serious thoughts, there is a reason why I posted this topic in the astronomy section.

Why are you surprised that several of us talked about conspiracy theories? You're the one who implied their need in your OP and outright discussed them in your second post.

If there's a reason you posted this topic in the astronomy section, then please tell us. The problem is that you've discussed different issues in each post you've made in this thread. What exactly is it you want to know or discuss or claim?

Someone picked up on dissolution of gases into water. The real question is, can the oceans dissolve any more? I think if they could they would've absorbed all they could throughout the billions of years. If they are constantly doing so then why aren't we running out of atmosphere?

Because the process of the oceans absorbing gas is only one component of a more complex system. Carbon and other elements move around between the oceans, the atmosphere, the Earth itself, and life on Earth. So yes, the oceans absorb gases, those molecules then dissolve into rocks, are subducted into the Earth, spewed back out into the atmosphere through volcanoes, and get breathed or otherwise absorbed by living organisms, which then later wee them out (or whatever). And so on...

As that's the limit of my knowledge, you might be better off asking for a geologist or geochemist or someone like that for more detailed discussion.

Is it possible that all the factors that reduce the amount are in exact balance with the ones that increase it (like volcanic activity)? A perfect balance sounds like an unlikely scenario.

Rather than a perfect balance, consider the system to be in dynamic equilibrium (which humans have lately been upsetting by dumping large amounts of carbon dioxide into the atmosphere).

If the Earth is indeed capable of holding more, then why hasn't it been building up to hundreds of bars throughout the aeons? Or if something counteracts that why hasn't such a force taken over and stripped it all? The only way I can accept a perfectly unchanging amount is by assuming that it's not being eroded and there is no gain, (which there is from still active volcanoes), otherwise I would be looking for a balancing mechanism, the most obvious being the possibility that this is all we can carry, if more is produced the upper layers are pushed out and lost. But if this is all the Earth can have, the question is still, why can the unprotected Venus have more, not just a little more, almost 100 times more? It just sounds absurd.

Well, you seem to have a sense of how complicated it is. Rather than dismissing it as absurd, perhaps it's worth considering that it's complicated enough that you need to study it for an extended period of time to learn about it properly.

Still waiting for that formula that everyone must know but they're teasing me for being so uninformed. Is it too much to ask for? It's always seemed the way to go: you observe (e.g. different planets take different amount of time to orbit the Sun), and find out why, the mechanism, look for the formula (Kepler's third law). So, different planets have different amounts of atmosphere and they are exactly what they are and couldn't be any different because... There is a scientific answer, right? But if everyone here is so damn smart and I'm the only dumb one, why hasn't anyone educated me yet? I've asked a simple and legitimate science question in the science forum section. How hard can it be to provide the obvious-to-everyone answer? Do I have to wait until page 20? Yahoo Answers is beginning to seem a more promising prospect.

If you're unsatisfied with the service here, there are plenty of science forums you could go to. How about Cosmoquest? http://cosmoquest.org/forum/

Edited February 7, 2014 by Peter B

[sepulchrave]

I was rather hoping (naively) to discuss things like, what's the theoretical upper limit for the mass of atmosphere a planet of given mass and radius (you want the surface gravity) can hold? Shouldn't there be some kind of formula?

There is no theoretical upper limit for the mass of an atmosphere of a planet.

Hydrogen and helium are more susceptible to escaping into space than other elements, but the escape of other elements is fairly minimal.

Venus has virtually no water left, because all of the atmospheric hydrogen escaped into space.

Most of Venus' atmosphere is CO₂ which is relatively heavy for a gas and is unlikely to dissociate under single ionization.

---------

Edited to add:

Earth probably would have a much denser atmosphere as well if it did not have a vast amount of lifeforms converting heavy CO_{2[/sup] into lighter O2 and H2O and also sequestering vast quantities of carbon, oxygen, and nitrogen into carbohydrates, proteins, etc.}

Edited February 7, 2014 by sepulchrave