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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.

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    $\begingroup$ 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. $\endgroup$
    – Uwe
    Jan 28, 2020 at 21:48
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    $\begingroup$ osti.gov/servlets/purl/6574363 $\endgroup$
    – Organic Marble
    Jan 29, 2020 at 2:26
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    $\begingroup$ @OrganicMarble yikes, that's going to take a while to read, but I've started in on Chapter 5 already. Thanks! $\endgroup$
    – uhoh
    Jan 29, 2020 at 2:36
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    $\begingroup$ @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?) $\endgroup$
    – Organic Marble
    Jan 29, 2020 at 2:56
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    $\begingroup$ @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. $\endgroup$
    – Christopher James Huff
    Jan 30, 2020 at 1:50

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