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If you added a dome to a mars base, greenhouses too, and added 1/10th Earth pressure (10 kPa) you would be able to grow lichen which could be a food source and a source of oxygen from the carbon dioxide in the air. In addition you could reduce the need for radiators for cooling the habitats, since it is likely they will have to expel heat similar to the ISS, the higher pressure would increase convection and increase the temperature within the dome. Lastly you would reduce the pressure difference of mars's atmosphere of 0.6 kPa and the dome air pressure of 10 kPa and the habitats pressure of 50 kPa which would reduce structural issues. (Greenhouses might be set inbetween 10 and 50 kPa.)

Edit: I've removed the part about not needing a pressure suit within the domes, which I see know you'll need at least 33 kPa.

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  • $\begingroup$ Your assumptions are wrong, breathing pure oxygen from a mask at a pressure of 0.1 bar is not sufficient for a person at rest or slow walk. The lower partial pressure limit for oxygen is about 0.16 bar. Space suits use 0.2 to 0.3 bars pressure. For a human fully adapted to living in high altitudes for many generations, 0.12 bar may do, see high altitude adaptation $\endgroup$ – Uwe Nov 1 '17 at 16:35
  • $\begingroup$ The oxygen masks can be at whatever pressure is necessary for the human body to function well. I only meant the pressure on their body would be above the Armstrong limit so they wouldn't need pressure suits. $\endgroup$ – Brooks Nelson Nov 1 '17 at 18:20
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    $\begingroup$ Easy breathing for hours requires equal pressure at the mouth and nose and the rest of the body. Body at 0.1 bar and mouth and lungs at 0.2 to 0.3 bar would not work. The acceptable pressure difference is much smaller, about 0.01 bar. $\endgroup$ – Uwe Nov 1 '17 at 18:35
  • $\begingroup$ Breathing from an oxygen mask (at an ambient pressure of 0.2 to 0.3) would be a waste of oxygen. A human at rest breath a volume of 10 liters per minute, but use only about 0.4 l oxygen. The exhaled oxygen contains about 0.4 l carbon dioxide. A closed circuit breathing system with a carbon dioxide scrubber would use only 0.4 l/minute instead of 10 l, a reduction by a factor of about 25. $\endgroup$ – Uwe Nov 3 '17 at 11:04
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Assuming a pure oxygen breathing environment, and using the charts found at this site, we can determine a few things.

  1. Assuming you can get 100% oxygen through a breathing apparatus, and assuming that you want to be in the middle of the safe zone, that would lead to a min pressure of 5 pounds/ square inch, or about 35 kPa.

An outer greenhouse is actually a good idea because it provides a second layer of protection against impacts. If the inner dome was broken somehow, but the outer intact, it would provide a layer of safety.

Bottom line, I think it isn't a bad idea. The downside, of course, is that you have to build a much larger dome to contain the two layers of growth. Having a layer that is perhaps a bit bigger and has some way of automatically collecting any growth might be a good idea, as it adds an extra layer of protection.

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  • $\begingroup$ Why wouldn't the Armstrong limit of 6.25 kPa apply? Putting it at 10 kPa I figured would make well within the limit for a pressure suit. And it gets you to the limit for potential lichen growth, though since it is the limit for lichen it might need to be a little higher too, 15 or 20 kPa. $\endgroup$ – Brooks Nelson Nov 1 '17 at 18:16
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    $\begingroup$ The Armstrong limit is a limit were the lungs would be filled with 100 % water vapour. Gas exchange is impossible with no oxygen in the lungs. Many mountain climbers have died at Mount Everest at 33.7 kPa $\endgroup$ – Uwe Nov 1 '17 at 18:50
  • $\begingroup$ The Armstrong limit is the theoretical limit. Would you live day to day at the theoretical limit of your ability to live? $\endgroup$ – PearsonArtPhoto Nov 1 '17 at 20:05
  • $\begingroup$ Breathing pure oxygen at 10 kPa would result in 6.25 kPa partial pressure of water vapour and only 3.75 kPa partial pressure of oxygen in the lungs. But at a ambient pressure of 30 kPa and breathing of pure oxygen, the partial pressures in the lungs are 6.25 kPa vapour and 23.75 kPa oxygen. $\endgroup$ – Uwe Nov 1 '17 at 20:19
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    $\begingroup$ @PearsonArtPhoto : survival at the Armstrong limit is not a matter of days, it is a matter of seconds to very few minutes. $\endgroup$ – Uwe Nov 1 '17 at 22:29

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