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peadar1987

Crops on Mars (minor "The Martian" spoilers)

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So in the book, Mark Watney grows potatoes in Martian soil. As far as I know, we don't know if that's possible or not.

Do we know enough about the composition of Martian soil to make up a batch of it here on earth for test purposes? I know it's likely to vary over the surface of the planet, but even if we had an idea for the regions where some of our landers have ended up, it might be possible.

Compared to some of the research we're doing, this seems like a fairly cheap option, with possible spin-off benefits for global food security by better understanding how certain crops perform in suboptimal conditions.

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Well, the perchlorate could be a problem, but maybe that is jsut on the top layers?

plants can grow in volcanic bassalt, of which we know mars has some, its presumably a similar composition... why not?

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How do you get nitrates?

EDIT: Wait, isn't indicating that this thread is a 'The Martian' spoiler in itself a 'The Martian' spoiler?

Edited by Kryten

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The perchlorate makes Martian regolith and dust highly toxic. Other than that, it's just a sterile substrate with no nutrients for plants. You can't just plant seeds and add water. Any sort of Martian agriculture would have to be based on massive importation of fertilizer and some sort of method to purify the regolith and turn it into loam.

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I seriously doubt that any plant could survive in Martian soil, as KerikBalm pointed out, the perchlorates would kill it almost on contact.

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while it can't fully be trusted, the wikipedia page on this does a pretty good job of summarizing a lot of information : https://en.wikipedia.org/wiki/Martian_soil

I actually did some research on "teh internets" on this a while ago, and what I found is basically that martian soil actually is pretty similar to earth soil with two very important differences:

- it's more alkaline. Decaying organic matter usually makes earth soil slightly acidic. Mars obviously doesn't have that, its soil is alkaline.

- It has significant concentrations of perchlorate salts. These are really the biggest challenge. If you can somehow either extract or neutralize the perchlorates, you could conceivably grow stuff on martian soil assuming you have sufficient fertilizer.

Apparently, martian soil does actually contain a lot of the nutrients needed for plantlife to grow. You just need to have a biodome to have a decent atmosphere and somehow get rid of the perchlorates (and some extra light might no be a bad idea). The alkaline soil wil make it hard for plants to grow, but not impossible.

And being a chemical engineer myself, I know that neutralizing alkalines isn't that hard. "somehow getting rid of the perchlorates" however, is much, much, MUCH easier said then done :P

Edited by Cirocco

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The experiments with the simulant soil works fine:

http://www.researchgate.net/publication/265094861_Can_Plants_Grow_on_Mars_and_the_Moon_A_Growth_Experiment_on_Mars_and_Moon_Soil_Simulants

The big question here is, how close this simulant is to the real soil. But this part cannot be answered right now, as we do not know more. So I would say: For best of humanity knowledge, crop should grow on mars.

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The perchlorate can be washed out of the soil with no problem at all.

[Citation needed]

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Nitrates have been found in both wind carried dust samples and scooped sample analysis. I have no idea if the concentrations are high enough to be useful.

The experiments with the simulant soil works fine:

http://www.researchgate.net/publication/265094861_Can_Plants_Grow_on_Mars_and_the_Moon_A_Growth_Experiment_on_Mars_and_Moon_Soil_Simulants

The big question here is, how close this simulant is to the real soil. But this part cannot be answered right now, as we do not know more. So I would say: For best of humanity knowledge, crop should grow on mars.

I thought "Someone must have tried to do this", and using google I also found that study. On the bright side the crops did very well in the Martian simulant. But then on the other hand they didn't include perchlorates. It's not part of their soil composition and the study doesn't address it's omission, which seems kind of odd given that it was published in 2014.

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You forget, Whatney used bacteria and his feces to make the soil more like home's.

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How do you get nitrates?

EDIT: Wait, isn't indicating that this thread is a 'The Martian' spoiler in itself a 'The Martian' spoiler?

Hmm... I wouldn't have thought so. All somebody could get from the title would be that crops were involved somehow. The "spoiler" could have been that Watney tries to grow crops, fails, and starves to death on Sol 98.

(I never thought that we'd be able to just stick plants into Martian regolith and watch them blossom, by the way, I always assumed that some measure of treatment would need to be done)

What's the story with the perchlorates? What are they? How toxic are they? And how widespread are they? Are they something that is likely to be universal across the surface, or could they be a localised mineral deposit?

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Well, the perchlorate could be a problem, but maybe that is jsut on the top layers?

I kinda figured they'd be leaving out some of the more recent undesirable nuances that would make Mars a living Hell to try colonizing (and I mean MORE of a living Hell than we thought it would be even a couple of decades ago).

If any of the silicates get into your lungs, it's all over. Even with a really good airlock, some of it is going to get into your habitat ON your suit, and sooner or later you're going to breathe it. MAYBE if you exercised the same levels of precaution you would when being around an airborne pathogen, it would be okay. But then cleaning a suit becomes a two-person job.

Edited by vger

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I kinda figured they'd be leaving out some of the more recent undesirable nuances that would make Mars a living Hell to try colonizing (and I mean MORE of a living Hell than we thought it would be even a couple of decades ago).

If any of the silicates get into your lungs, it's all over. Even with a really good airlock, some of it is going to get into your habitat ON your suit, and sooner or later you're going to breathe it. MAYBE if you exercised the same levels of precaution you would when being around an airborne pathogen, it would be okay. But then cleaning a suit becomes a two-person job.

Got a cite? You're saying that, to the best of our knowledge, the ordinary rocks of Mars are lethal, immediately, and not just a long term exposure hazard. I am skeptical. On earth, even if you worked in an asbestos plant handling the most dangerous form without protection, it takes more than 10-20 years to develop the lung cancer. For that matter, maybe if we can colonize Mars, we can grow a replacement lung...

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https://en.wikipedia.org/wiki/Perchlorate#Health_effects

Not instadeath, but it's toxic enough to make Mars a very bad place to want to bring up your children. Add the cosmic radiation and the low gravity, and I really can't see why some people still think that it is somewhat desirable to colonize Mars.

Further findings by the Mars Curiosity rover in 2012-2013 support perchlorates as being widespread,[20][21] and even inspired a Science article titled "Pesky Perchlorates All Over Mars".[22] At half-a-percentage of the component of Martian soil ("a fair amount"), Martian perchlorates present a serious challenge to human settlement, [23] and have rendered Kim Stanley Robinson's Mars trilogy somewhat anachronistic. [24]

Edited by Nibb31

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How about hydroponics? There is water ice under the surface, so why not use that? I think that would have to be used anyways until there's enough compostable organic matter (food waste) to produce the "right" kind of soil to grow plants...

------

Even with a really good airlock, some of it is going to get into your habitat ON your suit, and sooner or later you're going to breathe it.

Unless you had some way of completely isolating the interior of the habitat from the exterior, while still allowing for EVAs. Such as Suit-ports. It's a design where there is no crossover at all between the exterior of the suit and the interior of the habitat.

Edited by SargeRho

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https://en.wikipedia.org/wiki/Perchlorate#Health_effects

Not instadeath, but it's toxic enough to make Mars a very bad place to want to bring up your children. Add the cosmic radiation and the low gravity, and I really can't see why some people still think that it is somewhat desirable to colonize Mars.

And...

http://www.nlm.nih.gov/medlineplus/ency/article/000134.htm

Personally I would have to put the risks at a much higher level in the case of Mars. With something like asbestos on Earth, your exposure is typically limited to your time in the vicinity of it. You can go outside, lose the air mask, and you're done with it. On Mars, the particles are constantly drifting around in the air. Especially for someone who is gardening with the soil on a daily basis, you're going to have a very difficult time trying to avoid tracking any dust into the habitat, especially by yourself.

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How about hydroponics? There is water ice under the surface, so why not use that? I think that would have to be used anyways until there's enough compostable organic matter (food waste) to produce the "right" kind of soil to grow plants...

The places where there's ice close to the surface are pretty close to the poles, and winter in the polar regions of Mars is not something you want to be dealing with.

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The places where there's ice close to the surface are pretty close to the poles, and winter in the polar regions of Mars is not something you want to be dealing with.

Curiosity has detected evidence for liquid water, or rather, brine, has it not? It's not very close to the Poles.

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I remember reading a while back about how they tried simulating the soil and growing stuff in it. What things they did get to grow ended up so toxic they couldn't be eaten.

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No, it hasn't. I've no idea what you're talking about.

http://www.jpl.nasa.gov/news/news.php?feature=4549

Curiosity didn't find brine, just measured conditions that would be favorable for brines to form.

The places where there's ice close to the surface are pretty close to the poles, and winter in the polar regions of Mars is not something you want to be dealing with.

For solar power, definitely; but if you have nuclear power, it may not be so bad. Mars is cold, but its air is very thin, which should reduce rates of heat loss.

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The perchlorate makes Martian regolith and dust highly toxic. Other than that, it's just a sterile substrate with no nutrients for plants. You can't just plant seeds and add water. Any sort of Martian agriculture would have to be based on massive importation of fertilizer and some sort of method to purify the regolith and turn it into loam.

you mean like human urine and feces. Hmm I wonder where, we could get that from in space. BTW, plant roots also need oxygen, you cant just plant seeds in compressed martian atm at the right temperature and expect them to live. Spirulina can live withou O2.

- - - Updated - - -

Perchlorates are the anion of salts that are compsed of cations, such as ammonium, lithium, or sodium. ClO4- is a weak oxidant, it can form in relatively sterile oxygenated environments like the atacama desert. They can be reduced immediately by strong reductants and slowly by weak reductants. Perchlorates do not persist in soil. Composting reduces perchlorates, and deep soils undergo microbial anoxic metabolism by oxygen scavenging by perchlorates, nitrates, sulfates, and sugars. Consequently as they appear they are degraded. Thus it is not surprising they are present in martian soils and may indicate a past presence of oxygen and/or electrical discharges.

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IIRC quite a few deserts and evaporating environments have perchlorates in soil on Earth e.g. in New Mexico. I don't think they're a game-changing problem for Mars. Something that needs to be considered and mitigated for safety, certainly, but nothing really crazy.

(From what I find, the toxicity of perchlorates is not that high. Potassium perchlorate at least was used as a drug to treat thyroid issues, and apparently still is in some countries. It is still toxic, of course, but as usual 'the dose makes the poison'.)

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