While the Moon can offer many raw materials for the manufacturing of a wide range of technological components, it lacks abundant sources of carbon (required for steel) and nitrogen (useful for pneumatic applications, including air bearings). Mars' atmosphere is made of 95% carbon dioxide, 3% nitrogen, and 1.6% argon. My question is the following: what would be the most energy-efficient way to transport the carbon and nitrogen parts from Mars to the Moon?

I can think of the following options:

  • Compressing the mixed gases
  • Separating and liquefying the mixed gases
  • Separating the mixed gases, extracting and solidifying C, liquefying N₂

Regarding the third option, direct conversion of CO2 to solid carbon by Ga-based liquid metals is intriguing, but I could not find any confirmation that Gallium can be found on Mars. It can be found on the Moon with a 5ppm concentration, but I am unclear about how easy it is to refine.

Note: This question focuses on raw materials that could be found on Mars, the Moon, and some asteroids. It deliberately avoids using any raw materials from Earth. By doing so, it increases the probability that the solution could be deployed on many different planetary systems.

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    $\begingroup$ You would not liquefy both carbon dioxide and nitrogen anyway. When carbon dioxide is liquid nitrogen is gaseous. When nitrogen is liquid, carbon dioxide is solid. To liquefy the nitrogen, carbon dioxide should be separated before. $\endgroup$
    – Uwe
    Sep 26, 2022 at 14:14
  • $\begingroup$ @Uwe That makes sense. I have updated the original question accordingly. Thank you! $\endgroup$ Sep 26, 2022 at 14:29
  • $\begingroup$ In any event how does the nitrogen in Martian soil enter? Martian soil has been found to contain nitrates. $\endgroup$ Sep 26, 2022 at 15:13
  • $\begingroup$ Gallium is not consumed in the process you mention, and there are many other ways to convert carbon dioxide to carbon. For example, simply growing plants and carbonizing the resulting biomass. And pneumatic machinery can generally use oxygen, which is easy to obtain on the moon, or argon...nitrogen would be far more valuable for its chemical applications. $\endgroup$ Sep 26, 2022 at 17:09
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    $\begingroup$ @ChristopherJamesHuff Agreed. My description of the need for nitrogen is way too restrictive. I was overly concerned about one limited range of applications. Thanks a lot for all the suggestions, this is really helpful. $\endgroup$ Sep 26, 2022 at 18:24

1 Answer 1


A relatively simple device could be built and sent to Mars to produce hydrogen cyanide. Methane, ammonia and oxygen would be extracted from the atmosphere and reacted over a catalyst using the Andrussow process. The device could be solar powered and would fill containers with compressed hydrogen cyanide gas which would have to be picked up and transported. It would be resemble an advanced version of the MOXIE oxygen generator currently operating on Mars. https://en.wikipedia.org/wiki/Andrussow_process

  • $\begingroup$ If you can make ammonia in that kind of quantity, just ship that and some carbon. $\endgroup$ Sep 27, 2022 at 16:04
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    $\begingroup$ Well, I tried to honor the spirit of the question. With the earth a relatively short and consistent distance from the moon, I can’t imagine getting supplies from Mars. $\endgroup$ Sep 27, 2022 at 20:49
  • $\begingroup$ @AnthonyStevens Just to clarify the spirit of the question, I am trying to avoid using any raw materials from Earth. The idea is that if a process can work using only resources from Mars and the Moon, it is likely to work on many other planetary systems. $\endgroup$ Sep 29, 2022 at 11:42

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