breathable

[Findthepin1]

most people assume that when we eventually terraform mars, it needs a 1-atm atmosphere composed almost exactly like earth's. this is not needed. mars' atmosphere need only be 7 or 8 kilopascals of nearly pure oxygen. some mountains on earth are in what is called the "death zone" where the oxygen levels are lower than required for humans to breathe. the pressure at this altitude is 0.356 bar. but as always on earth, oxygen only makes up one-fifth of that. this gives us 7.12 kpa as the lowest partial pressure of oxygen for human life. water at 7.12 kpa boils at 39.32 degrees celsius or 102 degrees fahrenheit, so humans could theoretically not boil off on the surface, because the average temperature inside a human is 98 or so fahrenheit. but that's cutting it close, so i'd be comfortable with 0.1 atm of mostly oxygen, as we don't need a buffer gas should the pressure be low. this is enough to support water up to 46.11 degrees celsius and about half the total partial pressure of oxygen on earth. what do you think? also, if anyone has any ideas about how to terraform venus and mars, feel free to post them here.

[AngelLestat]

I dont know, maybe you can survive that for shorts amounts of time, but not live there.

There are many factors that matters:

partial pressure = total absolute pressure × volume fraction of gas component

ppO2 = P × FO2

where: ppO2=partial pressure of oxygen, P=total pressure, FO2=volume fraction of oxygen content.

in your example, it will be ppO2 = 0,07 bar x 1 --> ppO2= 0,07 bar as you mention.

But in literature the minimun safe limit of ppO2 is 0,17 bar.

The ppO2 value will force us to breath more fast or less fast, this mean exhaustion, no even hard trained people can survive for more than few hours in the everest top.

But mars gravity is lower, so the exhaustion is less.

So maybe an estimated minimun safe limit (not for full time living, no more than few hours by day, not old guys or childrens) it will be around 0,1 bar in mars.

That is still a lot of atmosphere that you need to release..

Mars atmosphere pressure : 0,006 bar. So you need to rise 20 times the mars pressure and reduce a bit more the amount of co2.

Edited May 1, 2015 by AngelLestat

[Findthepin1]

there is co2 in the ice cap

how do we get it out to thicken the air pressure

[-Velocity-]

I'd just be happy to get by with an oxygen tank and a non-pressurized breathing mask. I think that Mars has enough CO2 locked up in its caps to support this, I could be wrong though.

However, we do know that high levels of CO2 is poisonous over long periods of time, even if it's still just a small percentage of the air you breath in (like 2% or 3%). So if your face mask leaked just a little, you could eventually die from CO2 poisoning. That said- please someone with more knowledge on the subject chime in- I think we'd do fine for short periods of time even at relatively high percentages of CO2. I think it takes some time for dangerous amounts of CO2 to build up in the blood. I think. So even if you were breathing like 5% CO2, you might be good for an hour's stroll outside. I think.

[Technical Ben]

Well, as long as it's only a 5 min visit. All the radiation and that.

There are many orders of magnitude of problems terraforming Mars. It might be mechanically and practically eaiser to move earth to a Martian orbit!

[-Velocity-]

there is co2 in the ice cap

how do we get it out to thicken the air pressure

Maybe we could smash some comets or asteroids into it, though with that approach you might risk causing a long term global winter that ends up freezing more than it unfreezes.

Another approach I think I read about one time was relatively simple. Spread some heat-absorbing material on top of the polar caps. Maybe it could be as simple as just spreading some black carbon material. It will absorb heat and cause the CO2 underneath it to sublimate during the Martian summer (when the Sun will be above the horizon continuously). At some point, run-away global warming is supposed to take over and melt the rest of the CO2. Mars is in the habitable zone after all, so with a thick enough atmosphere it can be Earth-like.

Who knows, maybe the only thing keeping Mars' CO2 frozen now is "inertia"- clearly, in the past, when the Sun was dimmer, Mars settled into an atmosphere-frozen-out state because there simply wasn't enough solar radiation. Maybe now, the Sun is bright enough that Mars' atmosphere is in a sort of "metastable" state, and if we melted all the ice caps, then it would settle down into a permanently unfrozen state, and not slowly revert to its current state (at least, until atmospheric loss impacted it). Maybe all it awaits is the proper trigger and its atmosphere will come back. Maybe we just need Ahnuld to get his ahss to Mahrs.

- - - Updated - - -

Well, as long as it's only a 5 min visit. All the radiation and that.

There are many orders of magnitude of problems terraforming Mars. It might be mechanically and practically eaiser to move earth to a Martian orbit!

The radiation problem becomes mitigated a lot when the atmosphere is thicker. Atmospheres block radiation too. Does it become mitigated enough? I don't remember, maybe we don't know for sure because we don't know for sure how much radiation of this type we can take or are willing to take.

Edited May 1, 2015 by |Velocity|

[Technical Ben]

No AFAIK it does not. Magnetospheres are needed.

[-Velocity-]

No AFAIK it does not. Magnetospheres are needed.

No, actually, there's a big difference between needed and helpful. I know for a fact that magnetospheres are not 100% necessary for radiation shielding. If you have a thick enough atmosphere, it will block cosmic rays just as well as a thinner atmosphere and a magnetic field. I can guarantee you that Venus has much lower levels of cosmic radiation on its surface than Earth, despite having essentially no magnetic field.

Also, you are forgetting that during geomagnetic field reversals, Earth's magnetic field essentially disappears for a time, maybe thousands of years even. Last time it happened was like 100k years ago or something like that; our ancestors didn't even notice it (though maybe they saw aurora popping up in unusual places and thought the gods were angry at them or something). But they certainly had no problems surviving. Who knows, maybe some mutations caused by slightly increased levels of cosmic radiation were critical in the evolution of our species.

So thickening Mars' atmosphere does drastically reduce the amount of radiation due to cosmic rays on the surface, but I don't know if it reduces it to safe levels. (Of course, it does nothing to stop the ultraviolet light- at least on clear days- unless you add an ozone layer.)

Edited May 1, 2015 by |Velocity|

[andrewas]

You say you don't need a buffer gas, but plant life depends on nitrogen fixed from the atmosphere. Nitrogen also absorbs high frequency UV.

[AngelLestat]

plants absorb nitrogen from the ground... not the atmosphere.. (from what I know). "ignore this"

Edit:

Ah you mean that it needs to be fixed from the atmosphere into the ground?

I read wrong sorry..

Edited May 1, 2015 by AngelLestat

[andrewas]

Yeah, most plants get it from the soil, but nitrogen fixing plants are essential for a functioning biosphere. You could sustain agriculture with fertilizers, but if you want to terraform the planet, it should be capable of supporting an unmanaged biosphere, which means a nitrogen cycle similar to the one on Earth.

[Findthepin1]

You say you don't need a buffer gas, but plant life depends on nitrogen fixed from the atmosphere.

that is where we will put the nitrogen. it will probably be freed from the ground and ice like the co2, as a remnant from the old atmosphere in the noachian. i assume the ice caps have been there since, because mars has been cold since then. so the nitrogen needs nitrogen-fixing bacteria and stuff, then it will stay in the ground and not mostly the air. i hope.

[AngelLestat]

? that is not the only way to fix nitrogen... what about nitrates and ammonia.. that is what plants get from the ground.

[K^2]

Pure ox atmo is bad in so many ways that I don't even know where to start, but the fact that metals tend to be flamable in that is probably a good start. You'll also start oxidizing, well, just about anything on the planet that hasn't been thoroughly oxidized already, depleting your atmo. Finally, it's not good for living things either. Plants simply won't make it at all, and it won't be good for humans or animals under long exposure, either. Have you noticed that oxygen is actually an antisceptic under certain conditions? Yeah. It's not really good for you, unless thoroughly diluted.

[AngelLestat]

but it depends on the density K2, is not the same 1 atm pure oxygen atmosphere than 0.1 atm.

For example oxygen is poison for us if is pure at 1 atm, lower than that we dont have problems.

[Xeorm]

The short answer is that yes, it'd be breathable. Technically. It's used in some other cases with little adverse effects in the short term. Long term it's not good, but it'd work. There's plenty of reasons why it'd be a bad idea to try and use it for an atmosphere though, that I'm not terribly interested in repeating. Turning the atmosphere into a fireball would be one of them.

Well, as long as it's only a 5 min visit. All the radiation and that.

There are many orders of magnitude of problems terraforming Mars. It might be mechanically and practically eaiser to move earth to a Martian orbit!

Assuming you made the atmosphere correctly, you'd be able to provide plenty of defense against radiation. Mars' lack of a magnetosphere mainly means that it'd gradually lose atmosphere, but it'd still be healthy. The loss would be measured over thousands of years, so nothing that could't be stopped. Main issue would be pumping all the gas up, which would certainly be expensive. It's doable, but not going to happen.

[K^2]

but it depends on the density K2, is not the same 1 atm pure oxygen atmosphere than 0.1 atm.

For example oxygen is poison for us if is pure at 1 atm, lower than that we dont have problems.

No short term ones. Long term, it is still exposure to a powerful oxidant. It promotes generation of free radicals, that ca wreck havoc on your tissues. Lung cancer, for example, would be a thing to watch out for. We really need buffer gases in what we breathe.

[Bill Phil]

plants absorb nitrogen from the ground... not the atmosphere.. (from what I know). "ignore this"

Edit:

Ah you mean that it needs to be fixed from the atmosphere into the ground?

I read wrong sorry..

The nitrogen cycle is every bit as important as the water cycle, just like the carbon cycle.

[AngelLestat]

No short term ones. Long term, it is still exposure to a powerful oxidant. It promotes generation of free radicals, that ca wreck havoc on your tissues. Lung cancer, for example, would be a thing to watch out for. We really need buffer gases in what we breathe.

Yeah, but I accept the topic hypothesis rising a bit more the pressure estimated in the first post under the condition that it will be few hours by day and only trained people, not kids or old people.

http://forum.kerbalspaceprogram.com/threads/118308-breathable?p=1889096&viewfull=1#post1889096

The short answer is that yes, it'd be breathable. Technically. It's used in some other cases with little adverse effects in the short term. Long term it's not good, but it'd work. There's plenty of reasons why it'd be a bad idea to try and use it for an atmosphere though, that I'm not terribly interested in repeating. Turning the atmosphere into a fireball would be one of them.

Why the atmosphere would turn into a fireball? Yeah any combustion would be more energetic, with higher temperature, the energy density is kinda lower due pressure. But to burn all the atmosphere you need a mix of fuel in the whole atmosphere.

The nitrogen cycle is every bit as important as the water cycle, just like the carbon cycle.

Yeah I mention that in my latest post. Also I have a pond.. The nitrogen cycle is important in that case to keep the water clean.

[Bill Phil]

The problem with terraforming is that we don't really understand every last part of our environment. Before we terraform, enclosed ecosystems are a must, and then maybe we can learn more about Earth and how to keep it the way it is by terraforming a world like Mars?

Not to mention that it's mega engineering project.... Planetary Engineering FTW!

[K^2]

Yeah, but I accept the topic hypothesis rising a bit more the pressure estimated in the first post under the condition that it will be few hours by day and only trained people, not kids or old people.

If you want environment that can only be briefly visited, sure. But what's the point of converting an entire planet to that, then? Just put up an inflatable dome where you need it.

And for long-term teraforming, a CO2 environment is probably a better starting point.

[lajoswinkler]

Well, as long as it's only a 5 min visit. All the radiation and that.

There are many orders of magnitude of problems terraforming Mars. It might be mechanically and practically eaiser to move earth to a Martian orbit!

If a 5 minute limit was needed to be safe from the radiation dose, then the radiation intensity would be enormous, which it absolutely is not. It's Mars, not Io.

[peadar1987]

Anybody fancy a smoke?

[-Velocity-]

No short term ones. Long term, it is still exposure to a powerful oxidant. It promotes generation of free radicals, that ca wreck havoc on your tissues. Lung cancer, for example, would be a thing to watch out for. We really need buffer gases in what we breathe.

How is exposure to oxygen at like 0.2 atm with no buffer gas going to be different- aside from the much lower boiling points of liquids (and faster evaporation, too, right? (or wrong?))- than a partial pressure of 0.8 atm of N2 and a partial pressure of 0.2 atm of O2? The N2 is not chemically active (at least, for us). Does it mess with the way the lungs exchange gases somehow? I thought stuff like diffusion was based more on partial pressures. Sorry, chemistry and thermo is a weak area that I need to improve on (I've actually been seriously considering digging up my chemistry and thermo textbooks).

[AngelLestat]

If you want environment that can only be briefly visited, sure. But what's the point of converting an entire planet to that, then? Just put up an inflatable dome where you need it.

And for long-term teraforming, a CO2 environment is probably a better starting point.

But the gravity of mars is not enoght either, so even if we solve all long term issues with oxygen, we still have the long term issues due gravity.. unless we use genetic engineering.

Increasing the pressure is not efficient either, because mars would lose higher amount of atmosphere by day, more than the amount produced.

Anybody fancy a smoke?

That only happens because all the fuel is at a good mix with its oxidant, something that does not happen just with convection.

0.1 bar oxygen atmosphere.. yeah the cigarrete would last less time with higher combustion temperature, but nothing crazy.