Build Domed Cities on Mars - Air, Oxygen & Nitrogen Solutions

[GTOM]

TL;DR Summary

Nitrogenless air

If we want to build domed cities on Mars ( which i think a much cheaper option than O Neill cylinders) we need lots of local material.
As far as i know oxygen and water arent scarce much of theese materials didnt escape but became peroxides and ice in the regolith.
However are there enough nitrogen for whole cities? Maybe they should have low pressure inside, like at a mountaintop on Earth, but almost pure oxygen composition?

 

[256bits]

For starters, one would need the partial pressure of oxygen similar to that of standard air - that of 21% volume at 1 atm.
So a bit higher up than the pressure on top of mt. Everest.

 

[Rive]

Maybe they should have low pressure inside, like at a mountaintop on Earth, but almost pure oxygen composition?

I would say it would be too risky. Pure oxygen atmosphere is/was barely acceptable for early spacecraft s, but even with very meticulous design (after the first accidents) the risks were still there.
IMHO even to transfer the necessary nitrogen is far cheaper than building a whole city at a level of the interior of a spacecraft . Especially since you need nitrogen anyway if you want any kind of local plants/food production.

Ps.: by the way, Mars atmosphere has 2.x percent nitrogen. Not ideal, but still accessible anywhere on the planet. So nitrogen is not an issue.

 

[PeroK]

Maybe we could try to reduce the $CO_2$ in the Earth's atmosphere first?

 

[Dullard]

I would say it would be too risky. Pure oxygen atmosphere is/was barely acceptable for early spacecraft s, but even with very meticulous design (after the first accidents) the risks were still there.
IMHO even to transfer the necessary nitrogen is far cheaper than building a whole city at a level of the interior of a spacecraft . Especially since you need nitrogen anyway if you want any kind of local plants/food production.

Ps.: by the way, Mars atmosphere has 2.x percent nitrogen. Not ideal, but still accessible anywhere on the planet. So nitrogen is not an issue.

The 'risk' associated with a 'pure' oxygen atmosphere is a function of the pressure. 100% O2 at 1 Bar is dangerous (compared to our normal breathing mixture); 100% O2 at 0.2 Bar isn't (same ppO2).

The spacecraft were dangerous to test on the ground (At 1 BAR+) - not in flight.

 

[glappkaeft]

100% O2 at 0.2 atm is considered to be an "atmosphere of increased burning rate" as defined by the NFPA (maximum percentage of oxygen = 23.45/sqrt(Total Pressure in Atmospheres), NFPA 99B Chapter 3 Definitions; 3.3.3.3), not as bad as 100% at 1 atm but still dangerous. It also causes lung and throat irritation.

 

[Dullard]

100% O2 at 0.2 atm is considered to be an "atmosphere of increased burning rate" as defined by the NFPA (maximum percentage of oxygen = 23.45/sqrt(Total Pressure in Atmospheres), NFPA 99B Chapter 3 Definitions; 3.3.3.3), not as bad as 100% at 1 atm but still dangerous. It also causes lung and throat irritation.

That doesn't sound unreasonable. It's interesting that the post-fire Apollo program (and several subsequent programs) used pure oxygen at 5 PSI (for flight ops).

 

[Janus]

Something to consider is this: Spacesuits generally use a low pressure pure oxygen system. If your habitat was a 1 ATM gas mixture, then every time you wanted to do anything outside in a suit, you would first have to spend a good deal of time breathing pure oxygen first in order to flush out the nitrogen in your system to prevent the "bends". This is what they have to do on the ISS and used to do on the Shuttle.
The alternative would be to design a environmental suit( hard shell?) which used a higher pressure.

 

[glappkaeft]

That doesn't sound unreasonable. It's interesting that the post-fire Apollo program (and several subsequent programs) used pure oxygen at 5 PSI (for flight ops).

They pretty much didn't hava a choice since it wasn't designed for higher pressure. In a capsule you can also make an effort to remove any ignition risks (not that it worked for Apollo 1) but it is not an approach I would like to rely on anywhere people actually live.

 

[cmb]

Have you guys heard of Elon Musk's X prize? Removal of CO2?

https://www.xprize.org/prizes/elonm...l-funded-by-elon-musk-to-fight-climate-change

Combine this with his desire to colonise Mars and perhaps one might reach a conclusion that his X prize is not solely about converting only terrestrial CO2! :unsure:

 

[bob012345]

Better work fast as I understand the top 15 teams will be selected in only 18 months from the start in April this year.

 

[cmb]

If one could pressurise Martian atmosphere into a biosphere, would there be any terrestrial plants able to grow in such low sunlight/high CO2 conditions?

 

[bob012345]

If one could pressurise Martian atmosphere into a biosphere, would there be any terrestrial plants able to grow in such low sunlight/high CO2 conditions?

Here is a discussion of this question by the American Chemical Society.

https://www.acs.org/content/acs/en/...ril-2017/growing-green-on-the-red-planet.html

 

[cmb]

Here is a discussion of this question by the American Chemical Society.

https://www.acs.org/content/acs/en/...ril-2017/growing-green-on-the-red-planet.html

Not sure that answered my question What I was wondering was if there are any plants that can grow on the scant levels of sunlight on Mars, and at 95% CO2?

 

[.Scott]

"Medical Oxygen" as provided to hospitals (in contrast to that provided by portable machines) is more than 99% pure and has very little moisture.
"Aviator Oxygen" is required to be drier than what is required for "Medical Oxygen". The difference is that Medical Oxygen is used in normal environments whereas aviator oxygen is often exposed to more Mars-like conditions where freezing could cause a problem with O2 delivery.

Description of Aviator Oxygen

It also causes lung and throat irritation.

Here is an a paper that describes how to administer medical oxygen and what some of the medical problems can be:
Medical Oxygen Product information

It includes this:

Inhaled Medical Oxygen must be administered using an appropriate pressure reduction device and equipment such as mask or nasal prongs to deliver the required inspired concentration of oxygen, between 21% and 100%, as determined by the prescriber after full clinical assessment. Most delivery systems for adults result in an inspired oxygen concentration of 60% or less. Inhaled oxygen may require humidification when treatment duration is longer than an hour

That paper also includes the O2 medical problems - which become worse and worse as the pressure increases starting at 1000 millibars.
I am not sure whether those problems exists at 210 millibars of pure oxygen. I have not found any papers that say it does. But moisture is important. As a student pilot, and in a short aviation physiology training course (that included work in a hypobaric chamber), I was warned that the lack of moisture in aviation oxygen is something that needs to be considered. So Mars visitors may need to keep water bottles handy - at least until they get their HVAC systems perfected.

 

[bob012345]

Not sure that answered my question What I was wondering was if there are any plants that can grow on the scant levels of sunlight on Mars, and at 95% CO2?

Mars is further from the sun and receives less sunlight but I wouldn't call it 'scant'. And 95% CO2 is in relation to the Martian atmosphere which is about 1% of Earth pressure. So, your question is not clear to me.

Not sure that answered my question What I was wondering was if there are any plants that can grow on the scant levels of sunlight on Mars, and at 95% CO2?

Ok so my answer is as regards sunlight, yes. There are places on Earth with comparable average sunlight I think.

https://www.firsttheseedfoundation.org/resource/tomatosphere/background/sunlight-mars-enough-light-mars-grow-tomatoes/

With regards to the reduced pressure the answer appears to be no. However one can always increase the natural pressure but I am not certain if just doing that to the minimum acceptable CO2 pressure is enough.

https://www.firsttheseedfoundation.org/resource/tomatosphere/background/mars-weather-agriculture-greenhouses/

 

[bob012345]

Better work fast as I understand the top 15 teams will be selected in only 18 months from the start in April this year.

A major NYT article on carbon removal technology;

https://www.nytimes.com/2021/06/23/magazine/interface-carpet-carbon.html

 

[Rive]

What I was wondering was if there are any plants that can grow on the scant levels of sunlight on Mars, and at 95% CO2?

I think the sunlight is not the main issue. But you need oxygen, both for the plants and for the organims living in the soil: also, you need enough pressure to keep the water liquid.

 

[cmb]

I think the sunlight is not the main issue. But you need oxygen, both for the plants and for the organims living in the soil: also, you need enough pressure to keep the water liquid.

OK, if you think sunlight is manageable. I tended to think Mars was like Earth in winter, and stuff grows badly then, or is that because it's also cold?

On the atmospheric part, yes, this was the matter I was wondering. There is trace oxygen in the Martian atmosphere, and I recall my biology lessons that said although plants generate oxygen they also need it. Interesting thought on soil microbes.

So, assuming a 1 atmosphere pressurised transparent dome (where a nuclear/solar powered pressure pump pressurises Martian atmosphere), would there be enough oxygen and nitrogen to maintain life in a bio-dome from day 1, and what plants would one put in there to start off with that they would survive those initial conditions?

 

[Rive]

I tended to think Mars was like Earth in winter, and stuff grows badly then, or is that because it's also cold?

Preparing for winter is already part of the life cycle of (many) plants. It's not just about the temperature, but about the length of the day too.

Regarding Mars, the axial tilt and the length of the day is quite similar to Earth. So if you can maintain the temperature then you can set similar 'summer' and 'winter' periods (of course: with different length).

The sunlight will be of course less than on Earth. Picking plants with shadow tolerance might be a direction, but boosting the natural light is also a solution: just add some solar cells.
Heating will be needed anyway.

assuming a 1 atmosphere pressurised transparent dome (where a nuclear/solar powered pressure pump pressurises Martian atmosphere), would there be enough oxygen and nitrogen to maintain life in a bio-dome

I don't think so. The exact ratio needs many artificial fine-tuning, especially since at the beginning the soil will act as a big (carbon- and other)sink (the life in the soil needs to be built up from scratch).

Also, I think 1 atmosphere is unnecessary. High pressure means high structural demand. Just keeping boiling point above 40-50 degree should be fine.

But this part is already matter of optimization and detailed engineering/experimenting: depending on many things, even on the plants.

 

[mfb]

The atmosphere of Mars has 3% nitrogen and 2% argon. If you extract CO2 from the atmosphere then these two are the dominant remaining gas components, so you can use them in your habitats if you want. You don't need much even if you add it to the atmosphere - just replenish some losses here and there. You need a nitrogen source for plants (and they can't use it as a gas) but that can be done artificially. That nitrogen is not lost, it's in the plants afterwards and can be reused.
A low concentration of gases other than oxygen makes outdoor activities (Marswalks?) much easier as mentioned.

 

[Janus]

You need a nitrogen source for plants (and they can't use it as a gas) but that can be done artificially. T

There are nitrogen fixing plants that, with the help of bacteria, can use nitrogen directly from the air. Farmer use these in rotation with other crops to replenish nitrogen in the soil.
https://en.wikipedia.org/wiki/Category:Nitrogen-fixing_crops