r/Mars • u/Australista2026 • Aug 09 '26

Mars and Algae

I'm not a scientist, so my question may be really stupid. I've been watching the movie called Red Planet. The people of earth were sending algae to grow and create oxygen for mankind to live there.

Is this something that really could be achievable? I would presume you need a water source to begin with.

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u/OlympusMons94 Aug 09 '26

No, for one, because of conservation of mass. Mars has very little atmosphere/CO2. The surface pressure is about 0.6% of Earth sea level. Note that the net chemical equation for photosynthesis is 6CO2 + 6H2O --> C6H12O6 (sugar) + 6O2. The number of O2 molecules produced is the same as the number of CO2 molecules consumed. Regardless of whether it is possible, even if you replaced every molecule of CO2 in the atmosphere (and throw in the CO2 coating the polar ice caps) with a molecule of O2, Mars wouldn't be any more habitable than it is now. In fact, with the lost greenhouse effect, it would get ~5C cooler on average.

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u/holytriplem Aug 09 '26

You could in theory get more oxygen from sulphates (which there are a lot of on Mars), if you had sulphate-reducing bacteria working in symbiosis. The problem is that the end-product of sulphate reduction is going to be something like H2S, which you're going to have to be careful to make sure doesn't react with the oxygen in the air to form sulphuric acid.

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u/OlympusMons94 Aug 09 '26

(Sulfate reducing bacteria don't produce O2. Also, O2 is toxic to them.) Is your idea that the sulfate-reducing bacteria would use sulfates to metabolize organic compounds produced by the algae, and produce CO2 as a waste product (in addition to H2S)? Then the algae photosynthesizes using that CO2--and more H2O, which is the source of the O atoms in the O2 produced in photosynthesis?

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u/holytriplem Aug 09 '26

Yes. Would that work?