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How well could this work? On the plus side (for plants), the Martian atmosphere is about 95% CO2. Even though the total pressure of the atmosphere is much less

How well could this work? On the plus side (for plants), the Martian atmosphere is about 95% CO2. Even though the total pressure of the atmosphere is much less than our own, the partial pressure of CO2 is still about 20 times higher (erring a bit on the generous side). On the other hand, Mars is about 1.5 times as far from the sun, so the intensity of sunlight is less than half, and temperatures are correspondingly colder. Then again, if we're going to support human colonists, we probably need a nuclear power source anyway. So let's assume we rig up bright lighting to grow our plants. There's some uncertainty about the soil, but at least some studies suggest that it could support life. There's probably frozen water there, so we'll use the spare heat from our nuclear reactor to melt some. Humans need approximately 30g of Oxygen per hour, which is roughly 1 mole. A fast-photosynthesising plant can produce 30 umol/m2/s. Running the numbers, you'd need 9 square metres of leaf area photosynthesising at that rate per person - assuming it could carry on 24 hours a day. To supply food, you'd need rather more, because not all of the carbon fixed goes into edible parts. This is actually a lot more feasible than I initially thought. You'd probably want to send robots ahead to construct the base and plant the plants, though. And you still have the problem of life support for the journey, which would be several months.

xyzzy123 14y ago
I'm going to repost this here, because currently it seems like the AFP article is misleading the heck out of everyone. http://english.peopledaily.com.cn/90786/8044143.html http://english.peopledaily.com.cn/90786/8044143.html The experiment was a closed biosphere life support system, 36m^2 involving two subjects for 30 days. The article mentions the moon and mars. As I understand it, this thing would be a sealed capsule that you bring with you. This forms part of the ongoing field of CLESS (controlled ecological life support systems). All the references I've seen point to the Russian Bios-3 project as being the first public example of this. I am also interested to hear more about your ideas regarding the feasibility of martian agriculture :)
- takluyver 14y ago
  I guess you'd fill the capsule with 'locally sourced' air and soil, though, perhaps supplemented with some nutrients brought from earth. A sealed chamber could be pumped up to around earth pressure, making it easier for the astronauts to go in - although with high CO2, they'd still need oxygen tanks. On the other hand, the pressure difference would require a much stronger capsule, so perhaps farmers in spacesuits is the way to go.
  - jcarreiro 14y ago
    > I guess you'd fill the capsule with 'locally sourced' air There is no air on the moon, so this doesn't seem likely.
    - takluyver 14y ago
      OK, I was still focussing on the Martian case. I wonder if that actually makes a base on Mars an easier proposition.
      - mogrim 14y ago
        Although if you've got water (and there is water on the moon) and a nuclear powerplant generating loads of electricity, getting oxygen's not a problem.
        takluyver 14y ago
        It appears that you don't have much carbon, though (see 'Lunar regolith' on Wikipedia). So once you've got your oxygen generator set up, you may have to fly coal up there to burn for CO2. Once you're set up, though, you should be able to keep the carbon in a closed loop between humans, the encapsulated air and the plants.
        omegaworks 14y ago
        Soylent green is people!
jws 14y ago
Mars is about 1.5 times as far from the sun, so the intensity of sunlight is less than half Don't break out the nukes yet… No cloud cover is going to push up the average insolation, plus a thinner atmosphere will absorb less. Dust will bring it back down some amount. Temperature could be handled with insulation. Aerogel might be good here. A thin layer of glass sufficiently hard to survive the blowing dust and then a layer of aerogel to retain heat but still pass most of the light.
- takluyver 14y ago
  I think the light would be sufficient for plants, but I don't think insulation would be enough without a heat source. Now, you could lug loads of chemical fuel all the way from earth, or... Break out the nukes ;-)
  - Dylan16807 14y ago
    Sunlight is a pretty good heat source.
  - rndmcnlly0 14y ago
    "insolation" (think of incoming solar radiation) is distinct from "insulation"
stcredzero 14y ago
> So let's assume we rig up bright lighting to grow our plants. Sorry, but this is missing the point in as big a way as possible if you are using a nuclear plant. Even providing half intensity sunlight for large scale agricultural purposes is not feasible from an economic standpoint. Use the intensity of sunlight that's there. You just have to accept higher acreages and longer growing times. That would still enable civilization.
iwwr 14y ago
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).
- takluyver 14y ago
  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.
- apr 14y ago
  If you burn CO as fuel you are producing CO2 back.
  - jlgreco 14y ago
    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.
  - 14y ago
ChuckMcM 14y ago
Hmm and RTG like the one Curiosity is using could be used to charge batteries at night and then run growlights during the day. Excess heat could be captured to keep the temperature up. There is a the radiation hazard of course. A simpler solution is something like that setups that the aquaponics folks run. [1] Basically if you've got electricity (nuclear power) and water (from the soil/ice) you can build pressurized grow room to make food. It would be interesting for these guys to build such a system underground to get an idea of how much external electricity it needed to function. [1] http://en.wikipedia.org/wiki/Aquaponics http://en.wikipedia.org/wiki/Aquaponics
- danielweber 14y ago
  You probably want an actual nuclear power plant for any planet-side mission. The Russian TOPAZ is a model for what we'd want in the long run. RTGs are becoming extremely rare since the US isn't making any more. :(
cpeterso 14y ago
I wonder what types of plants would be most amenable to growing on Mars. The environment could be simulated in greenhouses (red houses ;) on Earth to cultivate successful plants (genetically-engineered or bred the old fashioned way).
- danielweber 14y ago
  I don't think any earth plant could survive 1% standard pressure. I have read papers on what genes would be interesting to splice here and there to make plants that could survive that, though.

xyzzy123 14y ago

I'm going to repost this here, because currently it seems like the AFP article is misleading the heck out of everyone. http://english.peopledaily.com.cn/90786/8044143.html http://english.peopledaily.com.cn/90786/8044143.html The experiment was a closed biosphere life support system, 36m^2 involving two subjects for 30 days. The article mentions the moon and mars. As I understand it, this thing would be a sealed capsule that you bring with you. This forms part of the ongoing field of CLESS (controlled ecological life support systems). All the references I've seen point to the Russian Bios-3 project as being the first public example of this. I am also interested to hear more about your ideas regarding the feasibility of martian agriculture :)

takluyver 14y ago
I guess you'd fill the capsule with 'locally sourced' air and soil, though, perhaps supplemented with some nutrients brought from earth. A sealed chamber could be pumped up to around earth pressure, making it easier for the astronauts to go in - although with high CO2, they'd still need oxygen tanks. On the other hand, the pressure difference would require a much stronger capsule, so perhaps farmers in spacesuits is the way to go.
- jcarreiro 14y ago
  > I guess you'd fill the capsule with 'locally sourced' air There is no air on the moon, so this doesn't seem likely.
  - takluyver 14y ago
    OK, I was still focussing on the Martian case. I wonder if that actually makes a base on Mars an easier proposition.
    - mogrim 14y ago
      Although if you've got water (and there is water on the moon) and a nuclear powerplant generating loads of electricity, getting oxygen's not a problem.
      - takluyver 14y ago
        It appears that you don't have much carbon, though (see 'Lunar regolith' on Wikipedia). So once you've got your oxygen generator set up, you may have to fly coal up there to burn for CO2. Once you're set up, though, you should be able to keep the carbon in a closed loop between humans, the encapsulated air and the plants.
        omegaworks 14y ago
        Soylent green is people!

jws 14y ago

Mars is about 1.5 times as far from the sun, so the intensity of sunlight is less than half Don't break out the nukes yet… No cloud cover is going to push up the average insolation, plus a thinner atmosphere will absorb less. Dust will bring it back down some amount. Temperature could be handled with insulation. Aerogel might be good here. A thin layer of glass sufficiently hard to survive the blowing dust and then a layer of aerogel to retain heat but still pass most of the light.

takluyver 14y ago
I think the light would be sufficient for plants, but I don't think insulation would be enough without a heat source. Now, you could lug loads of chemical fuel all the way from earth, or... Break out the nukes ;-)
- Dylan16807 14y ago
  Sunlight is a pretty good heat source.
- rndmcnlly0 14y ago
  "insolation" (think of incoming solar radiation) is distinct from "insulation"

stcredzero 14y ago

> So let's assume we rig up bright lighting to grow our plants. Sorry, but this is missing the point in as big a way as possible if you are using a nuclear plant. Even providing half intensity sunlight for large scale agricultural purposes is not feasible from an economic standpoint. Use the intensity of sunlight that's there. You just have to accept higher acreages and longer growing times. That would still enable civilization.

iwwr 14y ago

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).

takluyver 14y ago
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.
apr 14y ago
If you burn CO as fuel you are producing CO2 back.
- jlgreco 14y ago
  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.
- 14y ago

ChuckMcM 14y ago

Hmm and RTG like the one Curiosity is using could be used to charge batteries at night and then run growlights during the day. Excess heat could be captured to keep the temperature up. There is a the radiation hazard of course. A simpler solution is something like that setups that the aquaponics folks run. [1] Basically if you've got electricity (nuclear power) and water (from the soil/ice) you can build pressurized grow room to make food. It would be interesting for these guys to build such a system underground to get an idea of how much external electricity it needed to function. [1] http://en.wikipedia.org/wiki/Aquaponics http://en.wikipedia.org/wiki/Aquaponics

danielweber 14y ago
You probably want an actual nuclear power plant for any planet-side mission. The Russian TOPAZ is a model for what we'd want in the long run. RTGs are becoming extremely rare since the US isn't making any more. :(

cpeterso 14y ago

I wonder what types of plants would be most amenable to growing on Mars. The environment could be simulated in greenhouses (red houses ;) on Earth to cultivate successful plants (genetically-engineered or bred the old fashioned way).

danielweber 14y ago
I don't think any earth plant could survive 1% standard pressure. I have read papers on what genes would be interesting to splice here and there to make plants that could survive that, though.