Colonising Mars and a meme I found

[Mitchz95]

9 hours ago, ChrisSpace said:

Fourth, even if this scenario happened, every attempt failed and the world ended, the surviving population after the Impact Winter would still be far higher than the population of a colonised moon or Mars.

The way I see it, it's not about preserving humans as a species, but human civilization.

Yeah, a post-apocalyptic Earth will still be more habitable than Mars, but that doesn't do a lot of good if you have hordes of Mad Max-style reavers killing and plundering at will. It'd take decades or centuries for things to settle down enough to rebuild in a meaningful way, and any "doomsday backups" (whatever that means in this context) on the surface would be ripe for plundering in the meantime. Whereas if we have self-sufficient space colonies, civilization still exists and rebuilding Earth will be easier to organize and execute.

[kerbiloid]

That's the reason to maintain a planetary defense system to deflect or destroy any meteorite.
And to build huge city-sized vaults with thick walls and a lot of supplies.

P.S.
Though I'm sure Mars and several other places should be a backup storehouse of equipment and materials to restore the Earth industry.
And there should be orbital settlements populated with engineers and technicians. Not large, just ~50000 per Mars. Not permanent dwellers, but working there on contract.

Edited October 2, 2018 by kerbiloid

[Cassel]

1 hour ago, KSK said:

A ‘meat for meat’s sake’ system where you’re producing one nutrient source purely to feed it to a second nutrient source is, in my view, too wasteful of space and resources to be a good option. Especially as I doubt it’s even going to produce anything that much resembles actual animal meat. I could maybe see the psychological benefit (if not the nutritional benefit) to creating actual grillable meat on-site, but if all you’re producing is bizarro protein paste, then I just don’t see the point in not going with vegetable proteins in the first place.

If women are to have children on Mars, then meat will be needed during pregnancy and breastfeeding or children will start dying.
Vegetarianism is not a good idea, and it is certainly not proven idea, so it can not be said that it is healthy.

Animals eat other plants than humans or can eat other parts of plants.
Regardless of what will be grown on Mars, it will be necessary to collect part of the harvest as an emergency stock. Animals could feed on the oldest food when the exchange would take place, so that people would have as much fresh products as possible at all times.

I'm not an expert, but farmers on Earth sometimes change crops so that the same plants do not grow all over the same piece of land. On Mars, the same principle will apply.

 

1 hour ago, KSK said:

Unicellular foodstuffs, whether they be Quorn-alikes

No way, no one normal eats meat substitutes.

 

1 hour ago, KSK said:

Hydroponically grown soy beans are processed into soymeal. The waste husks are ground up and used as a substrate for growing mushrooms. Whatever’s left after that is mixed with the waste foliage from bean production and composted down to be mixed with regolith and biowaste from the colonists. Conveniently, the perchlorates in that regolith are a pretty good source of chlorine for sterilising the biowaste. 

Soy is the last thing you would like to eat in an environment with an elevated level of radiation. There are too many suspicions of carcinogenicity to risk life and eat this plant all the time. In addition, brain atrophy, phytic acid, modifications carried out by Monsanto, if it is to be the main source of food, you can already sign me out of a trip to Mars.

 

My questions were to show whether such a base on Mars would be possible at all. It turns out that no one tried to calculate the basics and determine how large base would be needed to feed people on a planet where there is no life.

[KSK]

58 minutes ago, kerbiloid said:

Any raw material would require a lot of processing. Just some of them for the growing, others - for the processing.
But chemistry is easier and more computable than biology, so the more pure chemistry - the less headache with biology. And less people required to feed others.

Starting to think I’m being trolled here. I’m also curious as to how much experience you have with synthetic chemistry, if you’re seriously proposing to use it to feed a colony. 

1 hour ago, kerbiloid said:

And unlike the farm you can sterilize the ill vat with gamma, wash it with chemicals, and get new portion of food much sooner than if you burn a field or massacre a farm.

Because clearly treating ailing plants with chemicals isn’t a thing. Likewise sterilising growth medium. Also, depending on exactly what is afflicting your plants, there’s a decent chance of still getting a useful crop before cleaning up your field/hydroponic bed and starting again. Not so much for an infected vat.

1 hour ago, kerbiloid said:

You don't need a year until a pig gets grown, or two for a calf.

Hang on a minute. Pretty sure I already said something relevant here...Ah yes - here we go:

“A ‘meat for meat’s sake’ system where you’re producing one nutrient source purely to feed it to a second nutrient source is, in my view, too wasteful of space and resources to be a good option.”

Please do tell me how raising pigs or cows fits into that viewpoint.

[kerbiloid]

34 minutes ago, KSK said:

I’m also curious as to how much experience you have with synthetic chemistry, if you’re seriously proposing to use it to feed a colony. 

None. But I have enough experience to see that there is/was a lot of artificial food substitutes made of hydrocarbons but still noone can make a self-sufficient long-term biosphere.

I don't say that's easy. I say that's easier than a Martian farming, unless you have a Martian farming experience.

41 minutes ago, KSK said:

Because clearly treating ailing plants with chemicals isn’t a thing.

One should wash the pot when it gets dirty.

41 minutes ago, KSK said:

Likewise sterilising growth medium.

Which medium? Vat is a metal or ceramics. Wash the pot, then fill is with pure ingredients and make the soup again.
Take a not contaminated cell if the previous ones (burnt with gamma and washed out) occasionally got contaminated.

But if instead of a vat you have greenhouses, soil, kitchen gardens, you can't just reset this all.
You will have all the joy of pathologic microbes, insects, fungi and other things, living where you are trying to grow the food.
In an Earth village you can allow this. But unlikely in a closed colony.

47 minutes ago, KSK said:

Also, depending on exactly what is afflicting your plants, there’s a decent chance of still getting a useful crop before cleaning up your field/hydroponic bed and starting again.

Instead of waiting months for unknown amount of maybe-healthy crops you can restart the process from scratch and do not wait when your stems will show first leaves.

49 minutes ago, KSK said:

Please do tell me how raising pigs or cows fits into that viewpoint.

I??? I'm saying there is no room for pigs and cows at least in extraterrestrial colonies. (I believe and on Earth, but that's another story.)

[KSK]

18 minutes ago, Cassel said:

If women are to have children on Mars, then meat will be needed during pregnancy and breastfeeding or children will start dying.
Vegetarianism is not a good idea, and it is certainly not proven idea, so it can not be said that it is healthy.

Disagree. A balanced diet is important and animal products make it easier to obtain certain nutrients but in most cases it’s also possible to get them from plant sources. Source. A notable and important exception is vitamin B12 which would either need to be produced on-site by bacterial fermentation (as it is on Earth), or shipped out to Mars in the form of vitamin pills. I think the latter is more likely and either would be a lot more practical than raising livestock on Mars.

29 minutes ago, Cassel said:

No way, no one normal eats meat substitutes.

Enough people do to make it a viable business sector which creates a decent selection of products to choose from. Personally I wouldn’t like to dismiss all those people as abnormal but your mileage may vary.

33 minutes ago, Cassel said:

Soy is the last thing you would like to eat in an environment with an elevated level of radiation. There are too many suspicions of carcinogenicity to risk life and eat this plant all the time. In addition, brain atrophy, phytic acid, modifications carried out by Monsanto, if it is to be the main source of food, you can already sign me out of a trip to Mars.

Given the real and actual risks of that high radiation environment, I’d be okay taking my chances with a suspicion of carcinogenicity in soy. I’d regard that as an acceptable risk from the benefits of eating a complete protein source (as in, contains all essential amino acids). Admittedly I’d also want to consume other plant proteins for balance and variety.

45 minutes ago, Cassel said:

My questions were to show whether such a base on Mars would be possible at all. It turns out that no one tried to calculate the basics and determine how large base would be needed to feed people on a planet where there is no life.

To be honest, I’m surprised by that given the various Mars studies that have been published over the years. But regardless of that, I already agreed that your questions were good ones. And my own ‘best way forward’ answer might turn out to be utterly unrealistic once somebody does run the numbers, or has already been shown to be unrealistic.

But I do find the automatic assumption that a Mars colony would need meat to be a curious one, and not one that I’ve seen good arguments for. 

[kerbiloid]

1 hour ago, Cassel said:

Vegetarianism is not a good idea

That's why a unicellular chickenpig would be not just a plant cell.

1 hour ago, Cassel said:

No way, no one normal eats meat substitutes.

Several billions do if treat soy like this.

1 hour ago, Cassel said:

My questions were to show whether such a base on Mars would be possible at all. It turns out that no one tried to calculate the basics and determine how large base would be needed to feed people on a planet where there is no life.

Each level of the natural food pyramid weights ~10 times more than the previous one.

70 kg of human eats 50:50 meat and plants.
So (70/2) * 10 + (70/2)*10*10 ~ 4 t of plants per human would present in ecosystem. And ~400 kg of herbivorous.

Of course, you should have either food for several years, or several times greater farm and herd in case your chickens mass die or your crops fall.
 

Edited October 2, 2018 by kerbiloid

[Cassel]

37 minutes ago, KSK said:

Disagree. A balanced diet is important and animal products make it easier to obtain certain nutrients but in most cases it’s also possible to get them from plant sources. Source. A notable and important exception is vitamin B12 which would either need to be produced on-site by bacterial fermentation (as it is on Earth), or shipped out to Mars in the form of vitamin pills. I think the latter is more likely and either would be a lot more practical than raising livestock on Mars.

Then it is impossible replace meat with a diet consisting only of plants, so why do you write that you disagree?

https://www.ncbi.nlm.nih.gov/pubmed/27137830
https://en.wikipedia.org/wiki/Docosahexaenoic_acid

 

Quote

Enough people do to make it a viable business sector which creates a decent selection of products to choose from. Personally I wouldn’t like to dismiss all those people as abnormal but your mileage may vary.

There will always be some ignorant, uneducated or poor people who have no choice.

 

Quote

Given the real and actual risks of that high radiation environment, I’d be okay taking my chances with a suspicion of carcinogenicity in soy. I’d regard that as an acceptable risk from the benefits of eating a complete protein source (as in, contains all essential amino acids). Admittedly I’d also want to consume other plant proteins for balance and variety.
 

Ok, that is, the environment with an elevated level of radiation, and to this add a diet that can be (which does not mean that I am 100% sure that it is) dangerous. "It's very reasonable."  :-)

 

Quote

To be honest, I’m surprised by that given the various Mars studies that have been published over the years. But regardless of that, I already agreed that your questions were good ones. And my own ‘best way forward’ answer might turn out to be utterly unrealistic once somebody does run the numbers, or has already been shown to be unrealistic.

This only confirms that a trip to another planet is fun for NASA fans, not a serious project.
 

Quote

But I do find the automatic assumption that a Mars colony would need meat to be a curious one, and not one that I’ve seen good arguments for. 

If vitamin B12 can not be replaced by plant ingredients, giving up meat is a stupid idea everywhere, even on Earth.

Edited October 2, 2018 by Cassel

[KSK]

21 minutes ago, kerbiloid said:

None. But I have enough experience to see that there is/was a lot of artificial food substitutes made of hydrocarbons.

I’m sorry but I’m really going to need some sources for that. If I’m being pedantic and assuming that you’re talking about literal hydrocarbons (as in compounds that only contain hydrogen and carbon) then I can’t think of a single food, artificial or otherwise, that can be made solely from those. If I’m being less of a pedant, then lipids are mostly hydrocarbon but you’re not going to get very far feeding your colonists nothing but lipids. 

Carbohydrates and proteins certainly aren’t hydrocarbons.  Synthesising some amino acids from simple precursors is certainly possible (see the classic Miller experiment for example) but I suspect synthesising all the necessary amino acids isn’t so straightforward. Carbohydrate chemistry is generally a pain.

55 minutes ago, kerbiloid said:

But if instead of a vat you have greenhouses, soil, kitchen gardens, you can't just reset this all.

Sure you can. If you’re using hydroponics you do exactly what you’ve proposed - sterilise your vessels, replace your liquid medium and restart. And just like you wouldn’t trust your food production to a single vat, you wouldn’t trust it to a single hydroponic bed either. 

Likewise if you’re using soil, then you’re more likely to be looking at using separate containers (essentially large plant pots) of soil. If you get an infestation, empty and sterilise the pot, steam clean the soil and replant. 

I’m not proposing to have actual fields on Mars  - that would be stupid for all the reasons you mention. Multiple greenhouses (for redundancy and damage limitation if you do happen to get an insect problem), growing plants in pots or multiple raised beds (for more redundancy). 

I think we both agree that there’s no room for actual livestock in an extraterrestrial colony. Sorry for any confusion there - I think we may have been talking past each other.

[Green Baron]

To keep you all entertained, i just learned what a spoonerism is (Thompson & Thomson).

Which reminded of a former professor who lectured about hydrocarbons in diet until someone in the auditory could not bear it anymore "Mr. xyz, do you mean carbohydrates ?".

He did.

Edited October 2, 2018 by Green Baron

[kerbiloid]

14 minutes ago, KSK said:

If I’m being less of a pedant, then lipids are mostly hydrocarbon but you’re not going to get very far feeding your colonists nothing but lipids. 

Have you even read my post about he chickenpig cells? Please, do not assign to me your own inventions (the second time).

If you haven't heard about synthetic margarine and caviar made of oil, that's your problem, not Martians'.

P.S.
I'm still trying to save those poor things from the healthy food lovers.

Edited October 2, 2018 by kerbiloid

[KSK]

39 minutes ago, Cassel said:

Then it is impossible replace meat with a diet consisting only of plants, so why do you write that you disagree?

I disagreed with your statement that:

“If women are to have children on Mars, then meat will be needed during pregnancy and breastfeeding or children will start dying.Vegetarianism is not a good idea, and it is certainly not proven idea, so it can not be said that it is healthy.“

As I said, meat is not needed for a balanced diet although it makes it easier to obtain. In the interests of an honest discussion, I pointed out the obvious exception that would prevent an entirely plant based diet from being viable. However B12 can be and is produced by bacterial fermentation, hence no meat is required for adequate B12 consumption.

From the article you linked:

“The American Dietetic Association's position is that appropriately planned vegan, lacto-vegetarian and lacto-ovo-vegetarian diets ensure a normal course of pregnancy and lactation. However, in practice the balancing of such a diet can pose certain difficulties, especially for individuals without the necessary experience or knowledge about nutrition. Nutrients to which particular attention needs to be paid to ensure their sufficient supply include: protein (essential amino acids), Omega-3 essential fatty acids, iron and calcium as well as vitamins D and B(12). The proper adherence to recommendations can be attained with a varied diet containing suitable plant products compensating for the nutritional value of the eliminated animal products. Supplementation with vitamin D and vitamin B(12) is also necessary. Research shows that infants born to vegetarian mothers are born at term and have normal birth weight. There is an increased risk of hypospadias in boys. The main difference in the composition of vegetarian mothers' milk compared to non-vegetarians' is lower content of docosahexaenoic acid and higher content of Linoleic and α-Linolenic acid.“

I think that summary actually supports my position rather well.

48 minutes ago, Cassel said:

If vitamin B12 can not be replaced by plant ingredients, giving up meat is a stupid idea everywhere, even on Earth.

Again, I disagree, for the reasons stated above. B12 can’t be replaced by plant ingredients but a perfectly viable alternative exists for people that choose not to eat meat or may find it impractical to eat meat. If a viable alternative exists then giving up meat is far from a stupid idea.

[Cassel]

5 minutes ago, KSK said:

I disagreed with your statement that:

“If women are to have children on Mars, then meat will be needed during pregnancy and breastfeeding or children will start dying.Vegetarianism is not a good idea, and it is certainly not proven idea, so it can not be said that it is healthy.“

As I said, meat is not needed for a balanced diet although it makes it easier to obtain. In the interests of an honest discussion, I pointed out the obvious exception that would prevent an entirely plant based diet from being viable. However B12 can be and is produced by bacterial fermentation, hence no meat is required for adequate B12 consumption.

What does it mean that a diet based only on plants is harmful.

5 minutes ago, KSK said:

From the article you linked:

I think that summary actually supports my position rather well.

Again, I disagree, for the reasons stated above. B12 can’t be replaced by plant ingredients but a perfectly viable alternative exists for people that choose not to eat meat or may find it impractical to eat meat. If a viable alternative exists then giving up meat is far from a stupid idea.

It is a pity that you missed what is important:

"Pregnant and breastfeeding women who eat vegetarian are a source of much controversy. This is the result of concern that eliminating some or all animal produce may lead to nutritional deficiencies and thus adversely affect the mother's and child's health. The American Dietetic Association's position is that appropriately planned vegan, lacto-vegetarian and lacto-ovo-vegetarian diets ensure a normal course of pregnancy and lactation. However, in practice the balancing of such a diet can pose certain difficulties, especially for individuals without the necessary experience or knowledge about nutrition. Nutrients to which particular attention needs to be paid to ensure their sufficient supply include: protein (essential amino acids), Omega-3 essential fatty acids, iron and calcium as well as vitamins D and B(12). The proper adherence to recommendations can be attained with a varied diet containing suitable plant products compensating for the nutritional value of the eliminated animal products. Supplementation with vitamin D and vitamin B(12) is also necessary. Research shows that infants born to vegetarian mothers are born at term and have normal birth weight. There is an increased risk of hypospadias in boys. The main difference in the composition of vegetarian mothers' milk compared to non-vegetarians' is lower content of docosahexaenoic acid and higher content of Linoleic and α-Linolenic acid."

If you have to take supplements all the time, it means that your diet is not healthy, it really is that simple.

[KSK]

14 minutes ago, kerbiloid said:

Have you even read my post about he chickenpig cells? Please, do not assign to me your own inventions (the second time).

If you haven't heard about synthetic margarine and caviar made of oil, that's your problem, not Martians'.

P.S.
I'm still trying to save those poor things from the healthy food lovers.

I fail to see what on Earth (or Mars for that matter) your chicken pig cells have to do with synthesising food from hydrocarbons. Caviar made from oil I was not aware of and I’d be happy to read any article on the subject you care to link to.

Margarine I’m well aware of. It’s made by hydrogenating unsaturated plant oils, thereby reducing their saturation (that is number of carbon-carbon double bonds they contain), thereby raising their melting point sufficiently that they become solid at room temperature. However, plant oils in this context are not hydrocarbons. Typically they will be esters of glycerol and long chain fatty acids (mainly di and tri esters) although they may also contain free fatty acids.

 

[lajoswinkler]

It's not a meme. It's an image with letters on it. Nothing famous about it.

And yes, I agree, we should practice on Antarctica. Even though we have research bases there, they are not self sustainable. Not even regarding food, let alone oxygen.

[magnemoe]

1 hour ago, KSK said:

I fail to see what on Earth (or Mars for that matter) your chicken pig cells have to do with synthesising food from hydrocarbons. Caviar made from oil I was not aware of and I’d be happy to read any article on the subject you care to link to.

Margarine I’m well aware of. It’s made by hydrogenating unsaturated plant oils, thereby reducing their saturation (that is number of carbon-carbon double bonds they contain), thereby raising their melting point sufficiently that they become solid at room temperature. However, plant oils in this context are not hydrocarbons. Typically they will be esters of glycerol and long chain fatty acids (mainly di and tri esters) although they may also contain free fatty acids.

 

Same here, food is an trivial problem, making an closed ecosystem will pretty much give you that anyway.
The real problem is technology, you need to be able to make anything you need from scratch, this includes space suits, solar panels with the control electronic an the dome and its ecosystem. And obviously all the machines you need to make the previous stuff. Adding advanced way to make food just increase the list of stuff you have to be able to make from bottom up. 

[KSK]

1 hour ago, Cassel said:

It is a pity that you missed what is important:

On the contrary. I took care to point out that eating meat makes it easier to obtain a balanced diet and that a vegetarian diet requires certain supplements.

As for a vegetarian diet being healthy, well in the most literal sense of ‘can you eat only plant matter and survive’, then no it’s not because it’s missing some essential nutrients.

However, beyond that very literal sense ‘health’ is a difficult thing to define. Take the traditional Inuit diet for example. It’s very high in meat and fat but, because a lot of that meat is consumed raw, can provide the required nutrients. However, at least according to that article, it’s also associated with higher than average mortality due to stroke. Does that make it a healthy diet? I don’t know the answer to that question.

However, with some dietary care (which I think we can assume in the context of a Martian colony) and addition of a small number of supplements, it is possible to make a plant based diet healthy in your literal sense of ‘providing all required nutrients.’ My point is that this plant+supplement diet would be far easier (edit - and more efficient) to maintain on Mars than having to deal with the additional complications of off-world meat production. 

Edited October 2, 2018 by KSK

[ChrisSpace]

7 hours ago, Mitchz95 said:

It'd take decades or centuries for things to settle down enough to rebuild in a meaningful way, and any "doomsday backups" (whatever that means in this context) on the surface would be ripe for plundering in the meantime.

Ripe for plundering? On the contrary, I expect the most high-tech survivor communities to be among the most well-armed.

[DerekL1963]

4 hours ago, magnemoe said:

The real problem is technology, you need to be able to make anything you need from scratch, this includes space suits, solar panels with the control electronic an the dome and its ecosystem. And obviously all the machines you need to make the previous stuff. Adding advanced way to make food just increase the list of stuff you have to be able to make from bottom up. 

Quoted for emphasis.   Arguing (mostly in a circle and past each other) over providing food is missing the point - true, complete, self sufficiency is hard.  And there's a lot more to it than food.

[Cassel]

8 hours ago, magnemoe said:

Same here, food is an trivial problem, making an closed ecosystem will pretty much give you that anyway.

Really? Then why there is no answer to my questions?

[YNM]

13 hours ago, Cassel said:

farmers on Earth sometimes change crops so that the same plants do not grow all over the same piece of land. On Mars, the same principle will apply. 

Hydroponic.

 

And yeah, the point is, the benefits that a system used on Mars brings will bring the exact same benefits (and a little more) if used on Earth.

So saying that "oh we can do A there" then "well you can do A here too" is almost always true apart from those that's obligate to the conditions on Mars.

 

I like to think that one day we'll be free from the bounds of Earth, but everytime I think of the means then it became apparent the only reason we can even do them is because we were relying on Earth itself.

Keep thinking and trying folks, we suceeded replacing horses with iron horses anyway.

Edited October 3, 2018 by YNM

[Cassel]

 

Quote

However, with some dietary care (which I think we can assume in the context of a Martian colony) and addition of a small number of supplements, it is possible to make a plant based diet healthy in your literal sense of ‘providing all required nutrients.’ My point is that this plant+supplement diet would be far easier (edit - and more efficient) to maintain on Mars than having to deal with the additional complications of off-world meat production. 

Yes, the efficiency of certain solutions will be better, but if this efficiency harms health, maybe it is better not to use such solutions?

1 hour ago, YNM said:

Hydroponic.

Great, so I have few questions for you :-)

What is the efficiency of such farms on Earth?
What will be the performance on Mars, where less sunlight reaches?
How much m^2 do you need to feed 100 people?
How many people of these 100 would have to work as farmers?
Where will you get the minerals and the essentials for plants?
How many tons of minerals do you need to keep a farm that can feed 100 people?

Edited October 3, 2018 by Cassel

[KSK]

34 minutes ago, Cassel said:

You missed the most important point, which shows that a vegetarian woman even when taking supplements will have a child with problems. Any disturbance in the development of the brain structure is a big problem.

You’re absolutely correct I did miss that - because it’s not shown in the article summary and I don’t have access to the full article.

Your article summary states that vegetarian mothers  have lower levels of DHA in their milk. True. The article summary also specifically states that essential fatty acids are a nutrient to which particular attention has to be paid to ensure sufficient supply. Lower DHA levels in milk is only a problem if that can’t be compensated for - which is not at all apparent from the article summary.

Looking into this in a little more detail it turns out that there are algal sources of DHA. Interestingly it appears that these sources were discovered by a NASA research program into life support systems using plants, for long duration spaceflight.

Since there is a plant based source of DHA available, then the ‘problem’ of adequate DHA for the children of vegetarian mothers is simply a non issue. Breastfeeding mothers can ensure that their diet contains sufficient algal oil. If breastfeeding is not an option for whatever reason, then the same oil can be added to formula milk.

Anyhow. I’m done here. I’m trying to present my arguments politely and logically and not having that same courtesy extended back to me is getting tiring. Before I say something that gets this thread locked, I think it’s best if I bow out here. Thank you for the discussion.

[Green Baron]

2 hours ago, Cassel said:

You missed the most important point, which shows that a vegetarian woman even when taking supplements will have a child with problems. Any disturbance in the development of the brain structure is a big problem.

But that is not what the text you linked says and afaik it is not what medicine men and women tell their customers. The text says that even vegan women can give birth to normally developing children, if they do some nutritional planning.

Millions of vegetarian women have quite normally developing children. My little sister has three of them. I don't know any vegans, though. And i am no expert in this.

Some more info i found:

https://www.nal.usda.gov/afsic/hydroponics

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What is the efficiency of such farms on Earth?

I suppose you mean energy efficiency ?

I found this, but i cannot comment more since i am not an expert:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4483736/

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What will be the performance on Mars, where less sunlight reaches?

That implies the use of solar arrays. You need ~double the area than on earth. And somebody with broom every now and then ;-) It will have little outcome near the poles, same as on earth.

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How much m^2 do you need to feed 100 people?

No idea. Maybe you can find an answer in the link above.

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How many people of these 100 would have to work as farmers?

See the eden-iss experiment. Probably not many (1 or 2) if technology does not fail. Else 0.

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Where will you get the minerals and the essentials for plants?

On mars ? Not initially. Much must be imported at first. There will certainly be a degree of self sustenance and recycling of vital elements in such greenhouse, the eden-iss experiment is due to end in 2020. We will hopefully have some nice publications afterwards, or at least a report.

Quote

How many tons of minerals do you need to keep a farm that can feed 100 people?

Idk. But it is not only the initial load, elements are used up and must be replaced. Or, if possible, taken from the consumers once they have dealt with them ;-) But a true closed cycle will not exist, some must constantly be replaced.

 

People are not that far yet to be able to answer all these questions in detail, i am sorry ...

Edited October 3, 2018 by Green Baron

[YNM]

6 hours ago, Cassel said:

What is the efficiency of such farms on Earth?
What will be the performance on Mars, where less sunlight reaches?

We'll be using artificial lighting.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4483736/

Quote

Assuming a conversion efficiency of 14% and an average daily solar radiation value of 6.5 kWh per square meter per year [29] the ratio of greenhouse to solar panel area that would be required to offset the full energy demand of the hydroponic system is approximately 1:3.0, with an understanding that the 24-h production cycle along with seasonal and day-to-day changes in solar radiation would require the system to be connected to the electrical grid.

I'll say that it takes about 1:16 (idealized day-night division of 12.3 earth hrs each) of hydroponic space (one layer of crop) vs. solar panels on Mars.

6 hours ago, Cassel said:

How much m^2 do you need to feed 100 people?
How many people of these 100 would have to work as farmers?

Usually one serving of rice is about 150 grams. 3 of them a day is 450 grams.

http://hortsci.ashspublications.org/content/28/5/531.3.short

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High yields and harvest indices in greenhouse studies indicated that japonica rice cultivar Ai-nan-tsao should be considered for inclusion in NASA's Controlled Ecological Life-Support Systems program. Ai-nantsao achieved a yield rate of 12.87 g m-2 d-1 when grown in continuously recirculating hydroponic systems under 12-h photoperiods in a growth chamber.

So it takes about 3500 sq m (0.35 ha) of hydroponics, which translates to 56,000 sq m (5.6 ha) of PV, for a combined area of ~6 ha. I'll be generous and give a penalty of 30% reduction, making for ~8.5 ha of PV+greenhouse.

6 hours ago, Cassel said:

How many people of these 100 would have to work as farmers?

Full automation is possible, but we'll say that every person can handle 0.33 ha of PV or crop, so we need 24 person. (though I'm not sure what 22 of those people will be doing to the PV...)

6 hours ago, Cassel said:

Where will you get the minerals and the essentials for plants?

Still downloading the paper (had failed 2 times and yes I have an extra shutty internet connection), will edit when done or please look for it yourself. I'm refering to this paper as this is the one I quoted for yield results, so if it's a different paper it will have a different configuration and so different yield results.

EDIT : Crap, they only have the abstracts.

Edited October 3, 2018 by YNM