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Comment by iwwr | Hacker News Reader

If you have a nuclear reactor or extensive solar panels, you may just as well use it to split CO2 into O2 and CO (monoxide gas can also burned as fuel). Plant photosynthesis is rather inefficient if your goal is a breathable atmosphere. If the goal is biomass for food, then just call up Monsanto for a few space-dense crops.

It would probably easier to oversize the powerplant (to generate oxygen, growlights, melt water, treat air and waste) than to try to bring along a whole biological ecosystem. On the first few trips at least...

The advantage with the powerplant approach is that you can live anywhere with rock and ice in the soil (most airless planetoids) or CO2 and water in the atmosphere (Venus, Mars or the gas giants).

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I agree, but I think it's still interesting from the point of view of food. As it takes months to get there, and months to get back, you probably want astronauts to be staying there for at least a few months.

Resupply from Earth is slow and expensive - especially when Mars is at the far end of its orbit. And as far as I know, we can't synthesise food artificially. Even if we could make some simple sugars, that will hardly keep the astronauts healthy. So I think growing plants would start to look quite inviting.

But I think the bigger challenge is getting anyone there in the first place. They'd need life support for months. I suspect you'd have to assemble something about the size of the ISS in Earth orbit, then send it across to Mars, and deploy landers to reach the surface.

If you burn CO as fuel you are producing CO2 back.

Also I'm not sure how useful CO fuel would be if you had electrical power already. Maybe splitting CO2 into CO and O2 only to later recombine could make sense as power storage? Maybe if you are using solar power and regular batteries aren't feasible for some reason, or maybe in a vehicle?

There might be uses for burning CO on Mars, but not as the byproduct of CO2 splitting for breathable oxygen.

It may be useful as fuel for a mars vehicle or for rockets (electric vehicles will take you not very far and it's hard to strap the nuclear reactor to it). CO is easier to store than hydrogen. Of course, if you have a steady supply of ice you can make methane/methanol which is better for that purpose. But to extract ice you will need heavy mining machinery, earth-moving etc...

CO + O2 fuel would make more sense on Venus, where water would be more scarce (water is present in thin clouds of sulphuric acid in about 25% concentration). The surface, however, is another business.

More on Venus (a surprisingly appealing place to go): http://www.space.com/5653-cloud-cities-venus.html

And a story by Geoffrey Landis http://www.asimovs.com/2010_09/exc_story1.shtml

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