Carbon dioxide

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Carbon dioxide[1] (chemical formula: CO2) is a chemical substance that occupies about 96 % of Mars's atmosphere.

Molar Mass of 12(C)+32(O2)=44

Biological significance

The metabolism of human beings, animals and various microbes depends on the oxidation of carbohydrates, resulting in carbon dioxide and water exhalation. Plants use the carbon from carbon dioxide to produce carbohydrates and release the oxygen back to the atmosphere, completing the cycle.

The reaction is: CO2(carbon dioxide) + 2H2O (water) + photons (light energy) → C(n)H2O(m) (carbohydrate) + O2(oxygen)+ H2O (water)[2]


CO2 will be extracted in-situ by atmospheric processing using compression and cooling.

Settlement atmosphere

Colony CO2 treatment.png

Carbon dioxide is required in the settlement atmosphere for plant metabolism. Standard concentration on Earth is increasing, so the value is a moving target. However, a concentration between 300ppm (0,03%) and 1000ppm (0,1%) is considered acceptable[3]. Nuclear submarines have varying carbon monoxide levels that can reach 9000 ppm in normal operations.

The Sabatier process can be used in place of photosynthesis to complete the atmospheric part of the carbon cycle. Synthesis of carbohydrates from methane would be required to complete the carbon metabolic cycle without the use of plants. Or food can be supplied from Earth or Mars for a partial cycle, where Methane from the Sabatier process can be stored for use as a propellant.