Pandoran atmosphere hypotheses.

[Spock]

The atmosphere of Pandora is made up of: Nitrogen, Oxygen, Carbon dioxide at 18%, Xenon at 5.5%, Methane, and Hydeogen sulfide. Can someone with enough experience put togethor a hypotheses of what would happen, specifically, to the human body when exposed to this atmosphere. Plus the atmosphere is also 20% more dense.

Another thing I want to ask is, if we were exposed to this atmosphere for say.... 15 seconds a day of breathing, would our bodies adapt?

[Prometheus]

Originally Posted by Spock

The atmosphere of Pandora is made up of: Nitrogen, Oxygen, Carbon dioxide at 18%, Xenon at 5.5%, Methane, and Hydrogen sulfide. Can someone with enough experience put together a hypotheses of what would happen, specifically, to the human body when exposed to this atmosphere. Plus the atmosphere is also 20% more dense.

Another thing I want to ask is, if we were exposed to this atmosphere for say.... 15 seconds a day of breathing, would our bodies adapt?

You'd choke to death almost immediately...the high conc of CO2 would hit you like a runaway train let alone the H2S and HCN which is in the atmosphere. Only takes 1 part in 2 billion of H2S to start affecting you (bad smell), any higher than 1 part in 1 billion and it will kill you. HCN is even deadlier.

Actually, 18% CO2 would make the planet that hot, it'd be on its way to ending up like Venus. The surface temp would be close to the boiling point of water. The atmosphere would be like a dense, hot, foggy soup.

No amount of adaptation would allow you to live there.

[Mongo]

Originally Posted by Prometheus

Actually, 18% CO2 would make the planet that hot, it'd be on its way to ending up like Venus. The surface temp would be close to the boiling point of water. The atmosphere would be like a dense, hot, foggy soup.

No amount of adaptation would allow you to live there.

That would depend on the insolation level as well. If Polyphemus (Pandora's gas giant primary) were at the equivalent of Mars's orbit in terms of insolation level (and don't forget that it probably eclipses Alpha Cen A for some part of each of Pandora's orbits about it), then the lower insolation level would presumably counteract the high greenhouse effect due to the CO2 (and CH4).

Indeed, to my knowledge the much lower solar luminosity in the Hadean/Archaean eons (70% of modern levels at 4.4 GA, rising to 80-85% at 2.5 GA) was more than counteracted by the very high CO2 and CH4 levels at the time, resulting in average temps in excess of 50 degrees C.

So if Polyphemus is sufficiently distant from Alpha Cen A, the average surface temps should be quite comparable to Earth's, if somewhat higher.

[Atan]

In the movie the humans where always wearing masks or holding their breath. I couldn't help but wonder, it's not just our breath that takes in oxygen, but our entire body. A lesson hard learned during one of the James Bond movies when a women died after being coated with enough paint that her body couldn't breath.

I would imagine just wearing a mask and having the rest of your body exposed to that environment for prolonged lengths of time would make you extremely sick.

[Pjalok'shi]

Originally Posted by Atan

In the movie the humans where always wearing masks or holding their breath. I couldn't help but wonder, it's not just our breath that takes in oxygen, but our entire body. A lesson hard learned during one of the James Bond movies when a women died after being coated with enough paint that her body couldn't breath.

I would imagine just wearing a mask and having the rest of your body exposed to that environment for prolonged lengths of time would make you extremely sick.

I was thinking this too. The toxic air would get into your blood stream via you skin. Same way if you got into a bad tub full of alcohol. You would get drunk over time. The Mythbusters had an episode about his where they sat in a bath tub full of beer and their blood alcohol level slowly but steady when up and beer is only like 7% alcohol. This process is very slow, but with the concentrations being stated above. I would imagine it wouldn't take very long before you started to get sick from the aspiration through your skin. Maybe JC will come up with a Pandora rule to address this like "Humans are only slowed in the atmosphere for 30 at a time"

[Spock]

Thanks for your replies. These answers are very helpfull.

[Prometheus]

Originally Posted by Mongo

That would depend on the insolation level as well. If Polyphemus (Pandora's gas giant primary) were at the equivalent of Mars's orbit in terms of insolation level (and don't forget that it probably eclipses Alpha Cen A for some part of each of Pandora's orbits about it), then the lower insolation level would presumably counteract the high greenhouse effect due to the CO2 (and CH4).

Indeed, to my knowledge the much lower solar luminosity in the Hadean/Archaean eons (70% of modern levels at 4.4 GA, rising to 80-85% at 2.5 GA) was more than counteracted by the very high CO2 and CH4 levels at the time, resulting in average temps in excess of 50 degrees C.

So if Polyphemus is sufficiently distant from Alpha Cen A, the average surface temps should be quite comparable to Earth's, if somewhat higher.

Yes, but Alpha is 1.57 times more luminous than the Sun. Even at the distance of Mars, it would be receiving nearly as much light as we do from our Sun. Even when it first formed Alpha was brighter than the present Sun...not by much (about 5%), but it was brighter. The best distance from a star such as Alpha for an Earth like planet is around 1.34AU, just short of Mars' orbit about the Sun (1.52AU)

The effect of eclipsing caused by Polyphemus wouldn't counteract any warming effects generated by the CO2 enough to make a large difference. There is just too much CO2 in the atmosphere to counteract....that much CO2 would be the perfect blanket, it would trap L-IR that well. Not only that, Pandora would orbit the giant in fairly short time...probably a few days at the most, so for most of that time it would be out of the shadow of the giant planet. To be effective, it would have to linger in the shadow of the giant for quite some time (a week or more), and to be at the right distance to do that, the gravitational pull of the outer giant planet would probably disturb Pandora's orbit sufficiently enough to fling it out of the system.

In effect, there's too much CO2 in the given atmosphere of Pandora. Now, if JC had've said about 8000-10000ppm (not the 180000ppm quoted), that would be more like it. Even 20000ppm would be reasonable. We certainly couldn't breathe in an atmosphere like that, and it would keep the planet warm...4-10degrees warmer on average than we have at present...think Cambrian Period in Earth's history (CO2 = 7000ppm), the only difference being higher oxygen levels.

[Mongo]

Originally Posted by Prometheus

Pandora would orbit the giant in fairly short time...probably a few days at the most, so for most of that time it would be out of the shadow of the giant planet. To be effective, it would have to linger in the shadow of the giant for quite some time (a week or more), and to be at the right distance to do that, the gravitational pull of the outer giant planet would probably disturb Pandora's orbit sufficiently enough to fling it out of the system.

I have to say that I don't follow you here. The percentage of its orbit that a moon could be in its primary's shadow increases with decreasing distance, with the limit being 50% of its orbit if the moon were skimming just above the primary's atmosphere. (Actually, the situation is more complex if the moon's rotation is tidally locked. The portion of the moon's surface that never sees the moon's primary would get the full stellar insolation, while the portion of the moon's surface that has the moon's primary directly overhead would get considerably lower direct insolation due to being blocked by its primary for some fraction of the time the star is above the local horizon. I imagine that there would be ferocious winds redistributing energy between the sub-primary and anti-primary hemispheres, with their strength depending on how much of the sky the moon's primary fills.)

From what I recall from the movie, Polyphemus takes up about 30 degrees in the sky, and hence (assuming that Alpha's apparent movement takes it directly behind the center of Polyphemus as viewed from Pandora) reduces Pandora's total globally-averaged insolation by 1/12th (plus whatever Polyphemus contributes in IR and reflected visible light).

[Human No More]

Carbon dioxide in that concentration would cause you to pass out very quickly, then eventually die of poisoning from it. The hydrogen sulphide would also cause rapid poisoning.

* 530–1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing;
* 800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure(LC50).
*Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.

So I'd guess the levels of H2S in the atmosphere are somewhere in the lower end of 530-1000

[Spock]

Originally Posted by Human No More

Carbon dioxide in that concentration would cause you to pass out very quickly, then eventually die of poisoning from it. The hydrogen sulphide would also cause rapid poisoning.

So I'd guess the levels of H2S in the atmosphere are somewhere in the lower end of 530-1000

Whoo, lets boogie. I love hearing this this kind of thing.

[Prometheus]

Originally Posted by Mongo

I have to say that I don't follow you here. The percentage of its orbit that a moon could be in its primary's shadow increases with decreasing distance, with the limit being 50% of its orbit if the moon were skimming just above the primary's atmosphere. (Actually, the situation is more complex if the moon's rotation is tidally locked. The portion of the moon's surface that never sees the moon's primary would get the full stellar insolation, while the portion of the moon's surface that has the moon's primary directly overhead would get considerably lower direct insolation due to being blocked by its primary for some fraction of the time the star is above the local horizon. I imagine that there would be ferocious winds redistributing energy between the sub-primary and anti-primary hemispheres, with their strength depending on how much of the sky the moon's primary fills.)

From what I recall from the movie, Polyphemus takes up about 30 degrees in the sky, and hence (assuming that Alpha's apparent movement takes it directly behind the center of Polyphemus as viewed from Pandora) reduces Pandora's total globally-averaged insolation by 1/12th (plus whatever Polyphemus contributes in IR and reflected visible light).

The closer in the moon orbits, the faster its orbit. So, even though it may be totally covered by the shadow of the Polyphemus when it is behind it, it doesn't stay there for too long. It's never in the shadow long enough to really cool it down to any extent...and with 18% CO2, the heat distribution and retention throughout the atmosphere would be very effective. The moon wouldn't lose much heat at all. However, if it was at a distance from Polyphemus where the moon was eclipsed for a considerable period of time, because of its slow orbital motion, it may cool somewhat. Polyphemus covers about 20% of the moon's sky, which would put it at about 3.41 million kilometres. At that distance, it would orbit the planet in about 6 days or so. At it's orbital velocity, it wouldn't stay any longer than 30-36 hours behind the planet before it emerged into bright sunlight. That length of time wouldn't be enough for the moon to cool considerably with such a CO2 rich atmosphere. Not only that, Pandora does rotate but the rotation is not locked to its orbital motion (spin-orbit coupling), so the moon never has any one side facing the planet all of the time.

The moon would never get as close as the top of the planet's atmosphere... that would be well within the Roche Distance of the planet-moon system and Pandora could be pulled to shreds (if it orbited permanently that close). Actually, given Pandora's size, it would most likely plunge into the giant intact and the resulting collision (as it would penetrate right to the core of Polyphemus...given its size) would give the giant planet a lot of grief. It would seriously disrupt the giant.

For Pandora to cool significantly in the shadow of Polyphemus, it would have to linger in that shadow for a week or more. I could work out how far away it would have to be, exactly, but I don't feel like doing it right now However, it would have to be about 20-30 million kilometres from the giant, at least, for it to linger for a week or so in its shadow. That far away from Polyphemus would probably put Pandora in the gravitational influence of Alpha's outer giant planet because of orbital resonances and such. That would make Pandora's orbit unstable and the moon would've either crashed into the giant or got flung out of the system altogether.

[Prometheus]

* 530–1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing;
* 800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure(LC50).
*Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.

That means for most of Earth's history....right up until very recently, we'd be stuffed. We wouldn't be able to survive in its atmosphere because CO2 levels were way too high, especially if given a modern atmospheric composition. Although, the higher O2 levels in the past would've partially compensated for this.


Like I said before...18% CO2 is ridiculously high. JC might not have thought this one through well enough. I'd be happier at 8000-10000ppm, but I'd want no loss of O2 levels either...maybe even an increase, to counter the CO2.

[Mongo]

Actually, I think that information about 1,000 ppm leading to immediate collapse must refer to H2S, not CO2. I know that people can work in greenhouses with CO2 concentrations up to 3,000 ppm (0.3%) for 8 hours at a time with no reported side effects. The U.S. Occupational Safety and Health Administration says that average exposure for healthy adults during an eight-hour work day should not exceed 5,000 ppm (0.5%) -- so I infer that 5,000 ppm is okay as well, for at least that length of time.

I see that further down that Wikipedia article we have this:

Adaptation to increased levels of CO2 occurs in humans. Continuous inhalation of CO2 can be tolerated at three percent inspired concentrations for at least one month and four percent inspired concentrations for over a week.

and this:

At about 8% it causes headache, sweating, dim vision, tremor and loss of consciousness after exposure for between five and ten minutes.

So the effects described in Avatar for an 18% (180,000 ppm) CO2 concentration sound about right to me in terms of more rapid loss of consciousness, especially if there are trace amounts of H2S as well. I think that James Cameron got it right.

[Prometheus]

Originally Posted by Prometheus

That means for most of Earth's history....right up until very recently, we'd be stuffed. We wouldn't be able to survive in its atmosphere because CO2 levels were way too high, especially if given a modern atmospheric composition. Although, the higher O2 levels in the past would've partially compensated for this.


Like I said before...18% CO2 is ridiculously high. JC might not have thought this one through well enough. I'd be happier at 8000-10000ppm, but I'd want no loss of O2 levels either...maybe even an increase, to counter the CO2.

Oops...misread the quote

Those conc's were for H2S

[Prometheus]

What's worse is there is a small amount of HCN in the atmosphere...that'd kill you stone dead almost immediately if the conc was greater than 3500ppm. 300ppm will kill you within 10 minutes. I would hope it's somewhere in the parts per billion level. You'd smell it though...the atmosphere would smell of almonds.