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I've been told I have no Moxie but I still need oxygen to live on Mars. I see that Mars' atmosphere is 0.14% oxygen and my sad moxiless self wants some.

I want to make a low power refrigerator to liquify oxygen from the atmosphere. I have a source of electricity, and I know that at night I can expose things to the sky 1, 2 for a cold source and martial regolith or rock can be used as a heat source relative to the night sky.

Can I build some kind of electric powered refrigerator to liquify oxygen? Based on simple thermodynamics, roughly how many Joules would I need per gram of oxygen liquified? For simplicity lets ignore the problem of high rate of dry ice buildup on my condenser.

uhoh
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    The boiling points of argon, oxygen and nitrogen are very close. Liquify all three and separate them by fractional distillation. Some of the energy used for the other gases may be recovered for precooling the atmosphere at inlet. – Uwe Jan 28 '20 at 21:48
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    https://www.osti.gov/servlets/purl/6574363 – Organic Marble Jan 29 '20 at 02:26
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    @OrganicMarble yikes, that's going to take a while to read, but I've started in on Chapter 5 already. Thanks! – uhoh Jan 29 '20 at 02:36
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    @uhoh Chapter 2 looks like the calculations and data one would need -see Tables 11 & 12. I started to step through it but I had too many questions (what is the inlet pressure and temperature for the machine sitting on Mars?) – Organic Marble Jan 29 '20 at 02:56
  • Not that this makes the question any easier to answer, but note that you don't really need to liquefy the oxygen if your goal is just to continue breathing. You just need to remove the CO and CO2 (much easier than liquefying the other components) and concentrate the O2. Standard oxygen concentrators remove the nitrogen from air by absorbing it into zeolite, apparently carbon can be used as a similar molecular sieve for argon: https://link.springer.com/article/10.1023%2FA%3A1008938930368 – Christopher James Huff Jan 29 '20 at 13:25
  • @ChristopherJamesHuff the Martian atmosphere has 1000 times more CO2 than O2 (see the first two links); I'm not sure zeolite alone can be used to produce a breathable mixture on Mars. – uhoh Jan 30 '20 at 00:27
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    @uhoh: the zeolite/carbon is what you use to deal with the nitrogen/argon after liquefying out the CO2 (which can be done near ambient temperature by pressurizing it to ~30 bars, or lower pressures at temperatures still far above liquid oxygen/argon/nitrogen). Alternatively you could use amine absorbers, but those are probably better used scrubbing CO2 from the stuff you're breathing. – Christopher James Huff Jan 30 '20 at 01:50
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    Of course, it may be easier to just electrolyze a bit of water to add to the O2/N2/Ar mix to bring the O2 concentration up where you want it. This is assuming you don't have other sources of it...O2 is likely to be an industrial waste product. – Christopher James Huff Jan 30 '20 at 01:55

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