Turning Mars regolith into soil - or How can I grow potatoes on Mars

kodiakbear · 2004-12-05 21:52:41

OK, so you are on Mars and want to grow food in a greenhouse of some kind. At some point you are going to want to not grow it all hydroponically. Based on what we know of Mars mineralogy (or think we know), what would we have to add to (or extract from) the regolith of Mars to use it as soil for growing plants? What one can use to grow plants for non-food uses would be less worrisome than what we must have if we are to use the soil for food production. So any would-be gardeners out there ready to turn a dusty red thumb into a green one?

Regards from the Rock.

SpaceNut · 2004-12-05 22:40:03

As gross as this may sound you have 6 plus months of human waste that can be used to fertilize the first fields that are planted and even if this crop is not eaten. The crop can become the compost for the next one that others will find more palatable since it will be grown more naturally(non human fertilizer).

GraemeSkinner · 2004-12-06 05:50:44

As gross as this may sound you have 6 plus months of human waste that can be used to furtilize the first fields that are planted and even if this crop is not eaten. The crop can become the compost for the next one that others will find more palitable since it will be grown more naturally(non human fertilizer).

I don't think it sounds gross at all, we have a septic tank that simply breaks the waste down to a sludge that eventually works its way back into the soil, which is our veg plot. We have had this year a nice crop of potatoes, and beans - no chemicals are needed.

Graeme

Dook · 2004-12-06 09:43:48

Human waste is a very poor fertilizer.

The first thing you would have to do is remove the oxidizer in the regolith. We don't seem to know exactly what it is, they have found evidence of salt. Also I think there are some other things (metals?) in the soil that you would want to remove.

I figure we put up a dome, pressurize it, run the top layer of regolith through a machine that mixes water in then removes the salt water. I don't know what you use to remove the other contaminants but then I would mix in fertilizer brought from the earth and spread it all out.

After you get some plants to grow you could have a compost pile.

RobS · 2004-12-06 11:49:27

We know regolith is poor in nitrogen and phosphorus; they'll have to be added. The regolith has various salts that will have to be washed out; it sounds like magnesium sulfates are particularly common. And some areas will have problems with trace elements in the regolith like selenum and arsenic, just as some areas of earth do. In my novels I assume regolith requires these steps to be onverted into soil:

1. Sieving to select only the right particle sizes. You don't want gravel (too coarse) or too much clay.

2. Washing to remove peroxides, superoxides, and salts.

3. Addition of phosphorus and nitrogen, and maybe other things. Warming of the proto-soil and stabilization of the growing conditions (which may take time, especially from contact with the cold Martian ground under the greenhouse).

4. Initial crop of genetically modified species to remove undesirable trace elements. These crops have not yet been developed and in some cases may be needed. There are species that selectively remove trace elements from soil and they can be bred to do this for you. The alternative is to use regoliths lacking undesirable trace elements. Maybe that's easy, but we won't know until we get there.

5. Addition of composed plant, animal, and human waste. First planting of a "green manure" crop to be plowed into the ground to give it organic content and to give worms and microorganisms time to get established before regular farming begins. Soils can be healthy or unhealthy in terms of the microrganisms and the ecosystems in them. Such ecosystems take some time to get established and become healthy.

6. Regular planting of productive species, with continued addition of composted wastes and fertilizer and monitoring of microorganisms in the soil and general soil health.

-- RobS

kodiakbear · 2004-12-06 12:59:56

Thanks for all the serious replies guys

If one is to use the options that take the longest in RobS post how long before the soil in your green house is ready for a planting of food crops?

Do you think grown food on mars should come from hydroponical greenhouses only with the soil greenhouse only a science program on the first mission?

RobS do you think genetically modified species to remove undesirable trace elements will be needed or could one just plant the a crop or two of say potatoes let them take up all the trace elements that potatoes take up and dispose of those crops then plant only potatoes in that soil.

Once again thanks for the serious replies

John H

BWhite · 2004-12-06 13:30:12

http://www.css.cornell.edu/faculty/lehm … .htm]Terra preta is a remarkably resilient soil filled with a complex suite of micro-organisms. It also "colonizes" poorer soils rather like sourdough bread starter mix provided its not overwhelmed with inorganics.

I propose taking a few hundred kg of this stuff, add a red worm colony, and "feed it" plant waste (plover) and additional plants grown expressly for composting (kudzu is a fun favorite of mine!), select minerals harvested from incinerated human waste and select minerals harvested from the Martian regolith.

= = =

A few years ago we had a HUGE "hydroponics" versus "soil" argument here at NewMars. IIRC, most people were content to end up answering "Both" - - start with hydroponics (actually MREs for the first mission) and move towards soil as permanent settlement gets going.

Edited By BWhite on 1102361466

GCNRevenger · 2004-12-06 14:07:14

I wonder if there is a practical and faster way to avoid the need to bring worms and let them improve the soil quality...

I'd also like to see what the limits of hydroponic growing could accomplish with GMO plants and careful water/organic recycling.

Regular shipments of Ammonia to Mars sounds like an inevitibility.

Dook · 2004-12-06 15:53:59

http://www.lpi.usra.edu/lpi/HEDS-UP/RedMars2.pdf#search=mars%20regolith%20composition]http://www.lpi.usra.edu/lpi/HEDS-UP/RedMars2.pdf#search=mars%20regolith%20composition]http://www.lpi.usra.edu/lpi/HEDS-UP/RedMars2.pdf#search='mars%20regolith%20composition'

Grypd · 2004-12-06 18:06:33

We could break down Martian rock into small stones and then use it as a feedbed with nutrients supplied by hydroponics. The feedbed is slightly sloped so that it allows gravity to get the nutrient solution moving.

This will allow the maximum amount of food supplied with less loss to seepage etc of planting straight into ground. Also generally hydroponics will allow easier inspection and planting for the scientists. Also will stop possible poisoning if kept well of the surface from regolith being brought into the greenhouse on boots etc. This is important as it is possible that the regolith may hold chemicals that could act like long term poisons to the people and any buildup in the body has to be avoided. Other protection and incidentally cold protection is to have the plants inside tunnels of clear plastic inside the greenhouse. We can pump atmosphere inside the tunnels to make a highly charged co2 atmosphere and a slight overpressure so helping to keep fines out.

Josh Cryer · 2004-12-06 21:56:45

A few years ago we had a HUGE "hydroponics" versus "soil" argument here at NewMars.

Heheh, I think it was more "everyone against Josh" but yeah. I've always been a huge proponant of hydroponics, it just seems simpiler, and a lot more risk-advertent. I'm not against soil in the long term, but I reckon hydroponics will simply be more efficient, and we may not really adopt soils (except for things like terraformation). Many flowers you buy in a store are grown hydroponically, same goes with a lot of fruit and veggies, too. A tightly controlled environment allows you to seriously grow your plants well. You have control over the chemical balance of soils, of course, but I think it's lessened by the fact that those chemicals have to be mixed in effectively; best time to do that is at the end of a crop season, which means you have to put up with a bad yeild 'cause that's all you can do.

If the first missions do have greenhouses, and are intended to supply food, we defintely want hydroponics, it's the only thing guaranteed to work in any environment with enough light.

RobS · 2004-12-06 22:09:01

How long before the regolith becomes useful soil: I suppose the timescale could be anywhere from days to months. If there are no poisonous trace elements, you have to sieve the regolith, wash it, warm it, and add fertilizer; that could be quick.

Could you just use, say, potatoes to remove trace elements; I have no idea which crops favor which elements.

Hydroponics instead: Why not. I favor soil long term. It is not clear to me when growing food becomes practical. I doubt it is in Mars Direct type missions where a crew of four stays at one place for 2 years and the next four-person crew lands somewhere else. Agriculture will take a fair amount of time (even with robots, if they are practical) and a lot of water.

Terra preta: Great idea, maybe it'll be just what Mars needs.

-- RobS

GraemeSkinner · 2004-12-07 00:54:13

Human waste is a very poor fertilizer.

Thats why its been used for thousands of years then? It may not be as efficient as pumping the ground full of chemicals but who really wants to do that?

After you get some plants to grow you could have a compost pile.

Taking the thread to an even worse level sorry , I have to agree first of all with getting a compost pile going. But one of the things that is advocated by gardening experts to help get a good quality compost is urine.

Graeme

Grypd · 2004-12-07 05:03:04

With Mars we have access to a lot of carbon it is though nitrates that we have a shortage off and human waste tends to be mostly carbon based. So we will need to find Nitrates to add to the mixtures to allow the plants to grow well. Anyone for a trip to the gas giants?

Little history lesson one of the most important materials man had on earth was the Bird droppings of the seabirds and bats. Quano was so important before the modern chemical industry that wars where fought over it.

So we will need to find Nitrates if we want to occupy Mars on mass.

GraemeSkinner · 2004-12-07 05:10:30

Again urine is a good source of nitrate, thats why its recommended by many organic gardeners. Though I suspect the majority of urine will be recycled for drinking water.

from wikipedia

Urine contains large amounts of urea, an excellent source of nitrogen for plants. As such it is a useful accelerator for compost.

Graeme

SpaceNut · 2004-12-07 06:17:08

On the not of toxic minerals, there has been research into methods to remove them via plant growth.
Purdue study finds antioxidant protects metal-eating plants
There was also another article about other toxins and of gold extractions as well that I can recall.

RobS · 2004-12-07 08:49:09

That's a great article, SpaceNut; thanks for finding it. Phytomining sounds promising as well.

No need to go to the Gas Giants to obtain nitrogen. Mars has plenty. The atmosphere is more than 2% nitrogen. If one were to take Martian air and compress it to liquify and separate off the CO2, the remaining gas would be about 60% nitrogen. Most of the rest is argon which is unreactive, so you could run the remnant gas through a Sabatier and make ammonia out of the nitrogen.

There may be nitrate deposits in the ground as well.

-- RobS

Grypd · 2004-12-07 09:01:09

Plants that eat metal or store it in their leaves or stems are common. But if we use this method it still relies on no seepage of dangerous metals and chemicals from outside. You see the problem is that as stated most plants do actually store metals, it is when we eat them that we begin to store these dangerous compounds too. We have to find a way without needing the whole of mars terraformed to be able to plant and grow food plants for people. If as it seems likely that Martian soil contains chemicals which would slowly poison us ie arsenic then we must reduce our plants exposure to these chemicals. And Hydroponics is one of the easiest ways others include digging ditches lining them with triple barriers of materials to stop all chemical seepage then putting treated and fertilised soil back in. But this is for the future as any mission can easily just use hydroponics then we let the future decide which method gives the best yield for the lowest cost basis.

BWhite · 2004-12-07 15:22:02

I wonder if there is a practical and faster way to avoid the need to bring worms and let them improve the soil quality...
I'd also like to see what the limits of hydroponic growing could accomplish with GMO plants and careful water/organic recycling.

I have no problem looking for a "better" solution than worms.

That said, we cannot allow plant waste and plover to be squandered. Lots of energy will be expended converting inorganic Mars H2O and CO2 in Terran organic CHONs - - wastefulness cannot be tolerated even if humans cannot eat the stuff, making compost is a 2nd best solution.

Regular shipments of Ammonia to Mars sounds like an inevitibility.

There is great potential for an ad campaign with the MiracleGro company. Send the stuff freeze-dried and ready to feed to the plants. Just add Mars water, after distillation to remove all those nasty heavy metals.

(Settlers will need massive anounts of power, and that means nuclear reactors, lots of nuclear reactors - - -as an aside using supercritical CO2 as your working fluid means smaller turbine blades and therefore less mass shipped from Earth.)

Austin Stanley · 2004-12-07 16:12:58

I wouldn't dismiss the problem of nitrogen so casualy. Sure you can liquidate some of it from the air, but at only 2% concentration in Mar's thin atmosphere this is going to take alot of energy and some realitivly bulky/heavy equipment to get a decent output. On earth it idealy takes about 760kJ/kg to cool, compress, and liquify nitrogen, but given the inefficency of cooling and compression equipment the actualy energy requirments are likely twice as great. On mars the atmosphere is colder, which helps but the atmosphere is so much thinner that the energy requirments are likely signifigantly greater.

Luckily the seperation of CO2, Water, Argon, and O2 is not a very energy intensive process. The water, CO2 and Argon will all liquify before the nitrogen, and are easily removed, while the Oxygen will still be a gas (although since you got it this far it makes sence to finish condenssing it as well). Aditionaly argon is about 2.5 times as water soluble then Nitrogen so a good amount of it will be removed with the water. Additionaly you could probably use all the waste heat you got from the cooling to power your Haber process. You would need to find additional water to make the ammonia with however, as you won't liquidate enough out of the atmosphere.

It's all pretty difficult though. I wonder if you couldn't just mine some nitrogen rich soil, although I'm not sure where you would find such. Some of the salt in the soil likely contains cyanide (-CN) which could be a potential source.

GCNRevenger · 2004-12-07 17:51:44

Unless some Martian soil source of Nitrogen is discoverd, I don't think that the tiny amount in the nearly non-exsistant atmosphere will be enough to do more then break even for losses from leaks and airlock cycling.

For bulk planet farming, Nitrogen in the form of Ammonia is the easiest form to bottle and ship from Earth, and the extra Hydrogen could be used to offset some of the need for water to make rocket/rover fuel with.

Why can't you reuse waste plant material as plant food for hydroponics? I'm pretty sure that it could be processed (chopped, boiled, biodegraded) into a useful product. Dirt does not have a monopoly on reuse, and there is no need to worry about sufficently cleaning the dirt prior to use.

RobS · 2004-12-07 18:03:53

Grypd, I don't think rare metals are that serious of a problem. I don't think basalt, for example, has significant quantities of them. Most soils on Earth don't have them. There may be soils on Mars that have them, though. We'll have to wait and see. If a greenhouse needs ten tonnes of sieved regolith, you'd want to choose it carefully. Once you've cleaned it of rare elements, I don't think any can "leak" in.

As for nitrogen, the Mars Direct ERV needs to use about forty or fifty tonnes of atmospheric CO2 for making methane and oxygen, and processing it would provide you with a half tonne of nitrogen. Plants are only a few percent nitrogen, so that half tonne would go a long way. Maybe it'd be easiest to import nitrogen to Mars for the first misison with a greenhouse, but a half century later Mars might be exporting nitrogen to the moon! In terms of delta-v, it's half as "far" away as the surface of the Earth.

Yes, I agree, GCNR, once nitrogen is obtained, it'll be recycled as much as is reasonably possible.

-- RobS

BWhite · 2004-12-07 18:10:29

Moving a frozen ammonia ball into low Mars orbit would be very valuable to any early Mars settlement.

= = =

Maybe it'd be easiest to import nitrogen to Mars for the first misison with a greenhouse, but a half century later Mars might be exporting nitrogen to the moon! In terms of delta-v, it's half as "far" away as the surface of the Earth.

Methane would be valuable export from Mars to the Moon as well, especially if the lunar poles contain far less frozen water in use-able form than is hoped for.

Edited By BWhite on 1102464742

GCNRevenger · 2004-12-07 21:05:23

Ammonia is more easily liquified, but it will boil off, it is a slightly cryogenic liquid. Carry it in tanks to Mars from Earth.

I seriously doubt that shipping carbon, nitrogen, or hydrogen from Mars will be profitable versus sending it from Earth with an RLV. In fact, sending everything from Earth that isn't available on-planet will be cheaper for a very long time.

Jenny Islander · 2004-12-12 02:58:01

I favor dirt and worms, as soon as it becomes feasible to have them, over hydroponics for the first generations of Martian settlement because of the moving parts issue. If you can bring the microbes and worms from Earth along with the minimum of chemical fertilizer, then treat some regolith as described further up this thread, you have dirt. Dirt+organic waste+attention=more dirt. A hydroponics setup, however, has parts that wear out, and until the Martians can make replacements on Mars from raw materials, those parts will have to come from Earth. On the other hand, a hydroponics setup can produce lots more food in much less space, and don't some versions double as water purifiers . . . ? I think a permanent base should start with a double hydroponics/dirt setup, then go to all dirt as parts wear out, then back to hydroponics when Martians are doing their own manufacturing.

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Re: Turning Mars regolith into soil - or How can I grow potatoes on Mars

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Re: Turning Mars regolith into soil - or How can I grow potatoes on Mars

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Re: Turning Mars regolith into soil - or How can I grow potatoes on Mars

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