Yes the soil is fine except for lack of nitrates - and almost no nitrogen in the atmosphere. Since Mars probably had lots of nitrogen in the past, like Earth, it's possible that there are deposits of nitrates maybe a few meters below the surface if you know where to look. Possibly if you dig into the ancient ocean beds in the northern hemisphere you might find nitrates for instance. All that nitrogen must have gone somewhere, unless it started off with no nitrogen from get go which seems unlikely. But there is almost nothing now on the surface or in the atmosphere. Just 1.9%. Atmosphere of Mars - compare with 78% for Earth. And our atmosphere is 100 times more dense than Mars so it is actually at a level of 0.019% of normal Earth atmospheric pressure, or 0.024% of the amount of available nitrogen you have on the Earth. Whether anything can fix nitrogen at those concentrations I don't know. Could we find nitrogen fixing native Mars life?
Lack of water need not be much of a problem in a greenhouse. But out in the open it is totally impossible because the water would freeze at night and the atmosphere is so low in pressure that any water would boil or be close to boiling in the daytime. You'd lose it all right away.
Similarly out in the open it is so cold that CO2 freezes out of the atmosphere at night even in equatorial regions it sometimes gets cold enough for CO2 to freeze out as dry ice.
You also have damaging levels of UV radiation which few plants can withstand.
There are some lichens, very hardy plants like that, from permafrost layers on the Earth, which can survive conditions like that. They could even take up moisture from the atmosphere - which is 100% humidity at night. Those could grow on the surface of Mars right away. And they don't need oxygen and they work fine with the Mars atmosphere and are protected from UV light. So some lichens and some green algae could survive on Mars even as it is now, possibly. These are experiments that are underway so nobody yet can really say for sure, just that they seem to do okay so far.
But it is a huge challenge for ordinary plants.
So - almost certainly has to be a greenhouse.
As Alan Marble says, there is no oxygen and ordinary plants need oxygen. But that might not be hard to find, as green algae generate oxygen and are easy to grow. Maybe all you need is a few trays of several square meters each of green algae. Those were enough to create an oxygen atmosphere enough for a human to breath in Russian ground experiments (sadly never flown in space), and that's quite a challenge.
The greenhouse would have to be heated for the plants to survive the night time low temperatures. In this proposed experiment they would use LEDs to heat the greenhouse.
Colonising Mars: Nasa Plans a Greenhouse for the Red Planet
Then also, you have the problem of the low pressure Mars atmosphere. The greenhouses would need to be pressurized - can't just put up an ordinary polytunnel or greenhouse.
The plants could be at a lower pressure, but this can cause problems. This article looks at a tenth of Earth pressure, which they think is doable, but that would still be a lot more than the Mars pressure and has problems as the plants react to the low pressure as if they were experiencing drought conditions. Greenhouses for Mars
Even at a tenth of Earth normal pressure, that's one ton per square meter of outwards pressure on the greenhouse. So they would need to be robustly built. Many artist impressions of Mars greenhouses are far too flimsy looking for this. Try the thought experiment of resting a ton on every square meter of the greenhouse and see if it would withstand that.
Most likely a greenhouse would be spherical or at least hemispherical in appearance, with part of it buried below the surface, and made of some very strong and rather thick clear plastic material. Maybe in two layers so you can replace it more easily when it ages or if it gets damaged - replace outer layer first then inner layer.
Heated of course. With ponds of algae to produce oxygen.
For water then probably use aeroponics at least to start with. Because water would be in short supply and plants don't need to be standing in water, but can take up water from their roots directly from the humidity of the air.
However - all this I see as rather far future. Because at present we want to study Mars in its uncontaminated state, without introducing Earth life to it, to find out if there is native life there already - or what happens to a planet like Mars without life if it doesn't have life. Last thing we want right now is to discover life that we brought to Mars ourselves.
You could actually grow plants on Mars however without contaminating it with Earth life, so long as you use sterile seeds and sterile hydroponics using chemicals to feed the plants with no microbes in them.
If you could find a low cost way to export to orbit, that could even be used to supply food to space colonies. Though I'm not sure myself that Mars provides enough benefit for that to be worthwhile.
The atmosphere is largely CO2 which is a waste product for colonies anyway - main problem of a space habitat is how to deal with excess CO2. And the soil - it is okay - but you can also grow plants on the lunar regolith, which is excellent for plants also. So there is probably suitable soil widespread in the solar system.
If Mars does have extensive deposits of nitrates, those could be a plus. Nitrogen is only present on the Moon in trace quantities. It is present in comets however in the form of frozen ammonia gas, also in some meteorites Meteorite with abundant nitrogen for life on Earth?
And for instance there is speculation that Ceres might be high in nitrogen content Opening Up Asteroids to Space Settlement?
If so then those would be an easier source of nitrogen for space settlements, because the Mars nitrogen would be deep in a gravity well.
So - anyway I'm not sure if greenhouses on Mars will be useful in the future, except for humans on Mars and as you'll see in my other posts then I don't think we will see humans on the surface in the near future for planetary protection reasons at least until we understand Mars a lot better than we do now. But in principle, if we find nitrates on Mars especially, and in a heated greenhouse, it could be good for plants.
And it is possible that lichens, and specially resistant types of green algae, could survive on Mars right away as is. There may be native life plants there already in very low concentrations. Either lichens on occasional rocks - maybe not green so hard to spot - or there could be native life in the more favourable habitats such as the warm seasonal flows, which you get even in the equatorial regions - where probably salty liquid water may flow in very thin mms thick films occasionally. Or may exist as droplets on salt / ice interfaces almost anywhere on Mars, and various other possibilities.
So there may be plant life there already in small quantities, very hardy plant life.
Another use of greenhouses on Mars would be for terraforming - or else - maybe "mars forming". But I think paraterraforming better.
If we found out that there is life on Mars that is present in low concentrations, one idea is to try to "roll back" the clock to an earlier Mars with a denser atmosphere. Covering areas of Mars with greenhouses would be a practical way to do that right away. That could perhaps be feasible with future technology though hugely expensive right now.
I could imagine a space mission that builds a small greenhouse on the Mars surface as a way to attempt to roll back to conditions of an earlier era and see what happens when you do that over a small part of Mars. Or to simulate the times when Mars gets briefly more habitable as the atmosphere gets thicker depending on its axial inclination similarly.
Once we thoroughly understand Mars, there is also the idea of paraterraforming the planet as a place for humans to live. Terraforming is far too long a process I think, multi-millennial, no way are we ready for that. We find it hard to commit to a single space project for a few decades, never mind commit all future generations for several millennia to this project. We just are not yet at that stage as a civilization I think, also don't know enough about how planets work and life works to do this except as ideas only - though roll forward a few thousand years and we may be able to do such things.
But paraterraforming is feasible, covering with greenhouses.
But - the problem with that is - that it would introduce Earth life to Mars in a way that is irreversible. So that is a major decision to make and I'm not at all sure we will know enough to do that responsibly in the near future.
It is far more responsible, in many ways easier, and also in many ways safer for humans, to build settlements in free space, on the Moon or in orbit. And Mars really doesn't have great advantages for settlement. The CO2 after all is usually a waste gas to get rid of in human habitats. Have just as good soil from asteroids, meteorites or the Moon. Atmospheric pressure at 1% is not enough to make it significantly easier to build there. And in free space you can use tethers or centrifuges or similar to simulate artificial gravity at whatever level you like and have a controlled climate with everything just as you need for humans, simulate any region on the Earth in your habitat. It is naturally insulated by the vacuum of space, main problem is to keep it cool. (except in the case of the Moon - but even there the "peaks of eternal light" at the poles are in sunlight pretty much year round).
And if you make a mistake, say some problem micro-organism wrecks havoc on your habitat and you can't do anything about it - then at the worst, you can then evacuate your atmosphere, sterilize the soil, and start again. Hard to do the same on Mars. And can do our first baby steps in looking into ideas that may later be used to transform planets if that is what we do eventually.
BTW if you are really keen on Mars - well though the surface I think not a great place for this, Deimos may well be. Might be that the first "martian" greenhouses for humans are built on Deimos using material from Deimos - especially if it turns out that it is rich in water ice, as some think is possible. Maybe Deimos will end up covered in greenhouses in some future? The ice is a natural source of fuel as well for rocket propulsion - and also - it is a valuable commodity which could sustain an economy there, exporting ice to LEO - it's not as crazy as it seems as the water can be used as propellant for the export there.
I could imagine a future with a small settlement - probably in a free habitat for artificial gravity rather than on Deimos itself - or else - maybe on Deimos if small scale spinning centrifuges are enough to keep humans healthy, with scientists studying Mars and others growing crops in greenhouses using materials from Deimos. If Deimos had nitrogen also that would be a major plus for this idea. As it may be a captured carbonacious chrondite then that seems not impossible. Deimos (moon)
And, this all assumes Deimos does have water ice, and even more so if it had nitrogen - it could become the water source for the inner solar system - and also since you are exporting from it anyway and have abundant fuel- it could supply food also to human space missions throughout the entire inner solar system :).
Lack of water need not be much of a problem in a greenhouse. But out in the open it is totally impossible because the water would freeze at night and the atmosphere is so low in pressure that any water would boil or be close to boiling in the daytime. You'd lose it all right away.
Similarly out in the open it is so cold that CO2 freezes out of the atmosphere at night even in equatorial regions it sometimes gets cold enough for CO2 to freeze out as dry ice.
You also have damaging levels of UV radiation which few plants can withstand.
There are some lichens, very hardy plants like that, from permafrost layers on the Earth, which can survive conditions like that. They could even take up moisture from the atmosphere - which is 100% humidity at night. Those could grow on the surface of Mars right away. And they don't need oxygen and they work fine with the Mars atmosphere and are protected from UV light. So some lichens and some green algae could survive on Mars even as it is now, possibly. These are experiments that are underway so nobody yet can really say for sure, just that they seem to do okay so far.
But it is a huge challenge for ordinary plants.
So - almost certainly has to be a greenhouse.
As Alan Marble says, there is no oxygen and ordinary plants need oxygen. But that might not be hard to find, as green algae generate oxygen and are easy to grow. Maybe all you need is a few trays of several square meters each of green algae. Those were enough to create an oxygen atmosphere enough for a human to breath in Russian ground experiments (sadly never flown in space), and that's quite a challenge.
The greenhouse would have to be heated for the plants to survive the night time low temperatures. In this proposed experiment they would use LEDs to heat the greenhouse.
Colonising Mars: Nasa Plans a Greenhouse for the Red Planet
Then also, you have the problem of the low pressure Mars atmosphere. The greenhouses would need to be pressurized - can't just put up an ordinary polytunnel or greenhouse.
The plants could be at a lower pressure, but this can cause problems. This article looks at a tenth of Earth pressure, which they think is doable, but that would still be a lot more than the Mars pressure and has problems as the plants react to the low pressure as if they were experiencing drought conditions. Greenhouses for Mars
Even at a tenth of Earth normal pressure, that's one ton per square meter of outwards pressure on the greenhouse. So they would need to be robustly built. Many artist impressions of Mars greenhouses are far too flimsy looking for this. Try the thought experiment of resting a ton on every square meter of the greenhouse and see if it would withstand that.
Most likely a greenhouse would be spherical or at least hemispherical in appearance, with part of it buried below the surface, and made of some very strong and rather thick clear plastic material. Maybe in two layers so you can replace it more easily when it ages or if it gets damaged - replace outer layer first then inner layer.
Heated of course. With ponds of algae to produce oxygen.
For water then probably use aeroponics at least to start with. Because water would be in short supply and plants don't need to be standing in water, but can take up water from their roots directly from the humidity of the air.
However - all this I see as rather far future. Because at present we want to study Mars in its uncontaminated state, without introducing Earth life to it, to find out if there is native life there already - or what happens to a planet like Mars without life if it doesn't have life. Last thing we want right now is to discover life that we brought to Mars ourselves.
You could actually grow plants on Mars however without contaminating it with Earth life, so long as you use sterile seeds and sterile hydroponics using chemicals to feed the plants with no microbes in them.
If you could find a low cost way to export to orbit, that could even be used to supply food to space colonies. Though I'm not sure myself that Mars provides enough benefit for that to be worthwhile.
The atmosphere is largely CO2 which is a waste product for colonies anyway - main problem of a space habitat is how to deal with excess CO2. And the soil - it is okay - but you can also grow plants on the lunar regolith, which is excellent for plants also. So there is probably suitable soil widespread in the solar system.
If Mars does have extensive deposits of nitrates, those could be a plus. Nitrogen is only present on the Moon in trace quantities. It is present in comets however in the form of frozen ammonia gas, also in some meteorites Meteorite with abundant nitrogen for life on Earth?
And for instance there is speculation that Ceres might be high in nitrogen content Opening Up Asteroids to Space Settlement?
If so then those would be an easier source of nitrogen for space settlements, because the Mars nitrogen would be deep in a gravity well.
So - anyway I'm not sure if greenhouses on Mars will be useful in the future, except for humans on Mars and as you'll see in my other posts then I don't think we will see humans on the surface in the near future for planetary protection reasons at least until we understand Mars a lot better than we do now. But in principle, if we find nitrates on Mars especially, and in a heated greenhouse, it could be good for plants.
And it is possible that lichens, and specially resistant types of green algae, could survive on Mars right away as is. There may be native life plants there already in very low concentrations. Either lichens on occasional rocks - maybe not green so hard to spot - or there could be native life in the more favourable habitats such as the warm seasonal flows, which you get even in the equatorial regions - where probably salty liquid water may flow in very thin mms thick films occasionally. Or may exist as droplets on salt / ice interfaces almost anywhere on Mars, and various other possibilities.
So there may be plant life there already in small quantities, very hardy plant life.
Another use of greenhouses on Mars would be for terraforming - or else - maybe "mars forming". But I think paraterraforming better.
If we found out that there is life on Mars that is present in low concentrations, one idea is to try to "roll back" the clock to an earlier Mars with a denser atmosphere. Covering areas of Mars with greenhouses would be a practical way to do that right away. That could perhaps be feasible with future technology though hugely expensive right now.
I could imagine a space mission that builds a small greenhouse on the Mars surface as a way to attempt to roll back to conditions of an earlier era and see what happens when you do that over a small part of Mars. Or to simulate the times when Mars gets briefly more habitable as the atmosphere gets thicker depending on its axial inclination similarly.
Once we thoroughly understand Mars, there is also the idea of paraterraforming the planet as a place for humans to live. Terraforming is far too long a process I think, multi-millennial, no way are we ready for that. We find it hard to commit to a single space project for a few decades, never mind commit all future generations for several millennia to this project. We just are not yet at that stage as a civilization I think, also don't know enough about how planets work and life works to do this except as ideas only - though roll forward a few thousand years and we may be able to do such things.
But paraterraforming is feasible, covering with greenhouses.
But - the problem with that is - that it would introduce Earth life to Mars in a way that is irreversible. So that is a major decision to make and I'm not at all sure we will know enough to do that responsibly in the near future.
It is far more responsible, in many ways easier, and also in many ways safer for humans, to build settlements in free space, on the Moon or in orbit. And Mars really doesn't have great advantages for settlement. The CO2 after all is usually a waste gas to get rid of in human habitats. Have just as good soil from asteroids, meteorites or the Moon. Atmospheric pressure at 1% is not enough to make it significantly easier to build there. And in free space you can use tethers or centrifuges or similar to simulate artificial gravity at whatever level you like and have a controlled climate with everything just as you need for humans, simulate any region on the Earth in your habitat. It is naturally insulated by the vacuum of space, main problem is to keep it cool. (except in the case of the Moon - but even there the "peaks of eternal light" at the poles are in sunlight pretty much year round).
And if you make a mistake, say some problem micro-organism wrecks havoc on your habitat and you can't do anything about it - then at the worst, you can then evacuate your atmosphere, sterilize the soil, and start again. Hard to do the same on Mars. And can do our first baby steps in looking into ideas that may later be used to transform planets if that is what we do eventually.
BTW if you are really keen on Mars - well though the surface I think not a great place for this, Deimos may well be. Might be that the first "martian" greenhouses for humans are built on Deimos using material from Deimos - especially if it turns out that it is rich in water ice, as some think is possible. Maybe Deimos will end up covered in greenhouses in some future? The ice is a natural source of fuel as well for rocket propulsion - and also - it is a valuable commodity which could sustain an economy there, exporting ice to LEO - it's not as crazy as it seems as the water can be used as propellant for the export there.
I could imagine a future with a small settlement - probably in a free habitat for artificial gravity rather than on Deimos itself - or else - maybe on Deimos if small scale spinning centrifuges are enough to keep humans healthy, with scientists studying Mars and others growing crops in greenhouses using materials from Deimos. If Deimos had nitrogen also that would be a major plus for this idea. As it may be a captured carbonacious chrondite then that seems not impossible. Deimos (moon)
And, this all assumes Deimos does have water ice, and even more so if it had nitrogen - it could become the water source for the inner solar system - and also since you are exporting from it anyway and have abundant fuel- it could supply food also to human space missions throughout the entire inner solar system :).
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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