By IonMars June 15, 2014

“O beautiful for spacious skies,
For amber waves of grain,
For purple mountain majesties
Above the fruited plain!”


The opening stanza from the popular patriotic poem by Katherine Lee Bates (1) evokes the beauty of deep blue skies above open wheat fields against a backdrop of purple-misted mountains.  Sometime in the future an equally inspired poet will rhapsodize the grey-white skies over a magnificently desolate plain against the background of the red regolith mountains of Mars.  Such are the contrasts between the atmospheres of the two planets that one displays farmland as open fields whereas the other will exhibit plant-bearing lands as confined between the interior walls and ceiling of a Mars greenhouse.  Exposure to open skies will be curtailed because only the living spaces protected by 2-1/2 meters of rock and soil will ensure the continued living of colonists from Earth.  

Gale Crater ViewThe term “greenhouse “ may also evoke some images that will apply to Mars in a very different way.  It is true that plants will be grown in the Mars equivalent of a “house” and because plants will grow inside they will be “green”.  For the early pioneers, however, greenhouses will not be built of large panes of glass or Plexiglas because the farmers who work to produce the colony’s food will want and need the same protection from galactic cosmic rays (GCR) and micrometeorites as colonists in other trades.  They will learn to grow crops in houses built with a protective laver of regolith overhead like everyone else.  A standard greenhouse will require the same protective structure as the Mars house described in the article “Pioneer House Building,” so a house built from stone blocks utilizing a scaffold will be adapted for growing crops.  The floor space will be about 80 square meters, which will be the beginning of food production for the Mars village.  It may or may not be sufficient for a small group, depending on its degree of productivity and the number of people.  In any case the addition of more farmland will be desirable as soon as it is feasible.  This means building more greenhouses.  

The greenhouse will be more than a means of food production.  The plant growing and food producing system will be linked to a biological waste treatment process.  The objective of the two-phase mini-ecosystem will be to recycle nutrients to the extent feasible within the colony.



On Earth, the biosphere encompasses the entire surface of the planet.  In such a biosphere it is easy to practice “waste” disposal and think in terms of “throwing away” excess food and flushing body wastes “down the toilet.”  But take a moment to think where these by-products of daily living actually go.  The food waste is picked up at your doorstep and taken to a landfill where it is buried. Microorganisms in the soil break down the nutrients into simpler chemicals, such as amino acids, that are taken up by other organisms.  A complicated chemical factory is orchestrated by several thousands of species of organisms.  Over the course of decades, it is CO2 and H2O that are added to the biosphere.  

Earth BiosphereLikewise, sewage from humans is flushed into a community plumbing system that carries it to a community treatment plant.  Here, another horde of hungry microorganisms attacks this food and rapidly reduce it to simpler chemicals.  Within 24 hours the water-soluble portion is disinfected and discharged into the watery biosphere.  Another menagerie of mini-creatures further treats the solid portion.  After a month or two the reduced material is discharged as soil conditioner and the water portion is discharged into the same water environment.  Humans will eventually dip into this biosphere for O2, H2O, and carbon.  But what’s the hurry?  The biosphere is so vast that human activity comprises but a tiny portion of the mass of atmosphere and soil.  

Compare this to Mars, where the “biosphere” will comprise a few acres of land with a small amount of air and water defined by a limited number of protected enclosures.   Yes, all living requirements can be derived from the Martian air and mined minerals using equipment and materials imported from Earth.  But at what a cost!  Currently estimated at $60,000 USD per kg, imports from Earth will take on the value of jewelry on Earth.  So once we produce a usable soil and a livable biosphere, do we want to throw them away and replace them whenever needed?  No, we want to reuse and recycle fiercely, as if our lives depend on it, because it does.


Food Production

In building the Mars greenhouse the first consideration will be food production.  Certain basic materials will be required for growing crops indoors regardless of whether Earth or Mars will be the address for he greenhouse. (2) The following is a rundown of the minimum requirements:  

1) Water.  One criterion for a good location for a colony is a site with a major source of water.  Farming will require more H2O than any personal water usage.   As described in “Pioneer Ice Mining,” fresh water will be delivered to the village through water pipelines as in an Earth community.  Within the village, pipes will deliver water to the greenhouse through a standard plumbing system to allow water to be conveniently available to every plant.  

Earth Greenhouse2) Soil base (substrate).  In keeping with the principal of ISRU, regolith will be employed as a substrate.  A large portion of the regolith is composed of silicon dioxide particles (glass), which are similar in composition to sand on Earth, but much finer particles.  So far, testing of Martian “soil” and analyses of simulated Martian regolith has found no intrinsic barrier to this usage. (3,4) Certain elements are lacking, however, and must supplement the regolith to create a growth medium.  

3) Soil conditioner.  One principal component of Earth soil that is lacking in regolith is carbon.  This element is a normal component of living things and Earth soil swarms with living creatures, mostly microscopic.  The principal methods for supplying carbon to the greenhouse air will be the adsorption of CO2 from the Martian atmosphere (See “Dr. Sabatier’s Appurtenances”) and by means of well-maintained compost.  

In the Mars village there will be no obvious waste.  Some of the items that will not be wasted are leftover foods, dirt from washing clothes, and dirt from washing humans.  The leftover foods will be delivered to a compost facility in the greenhouse.  Water-borne dirt (food for the microflora) will be collected in the wastewater pipes and delivered to the wastewater treatment facility.  Some of this will become an input to the compost facility.   

A mixture of regolith, compost soil conditioner, and microflora will build up the greenhouse soil.  The microflora will be imported from Earth in the skin and internal organs of colonists who will serve as safe havens for these second-class stowaways on the Mars Colonial Transporter.  They will hitch a ride inside the intestinal tracts of innocent colonists until they are injected into the Martian wastewater stream and then unto the soil.  Other bacteria will travel to Mars in sample containers taken from active Earth soils.  This original soil will serve to inoculate additional soil as the living farmland expands.   As farmland expands, the non-food portions of plants will also be collected for composting. 

Bag of Fertilizer4) Nutrients.  Some elements that are frequently lacking in Earth soil as well as Martian regolith are nitrogen and phosphorous.  Initially, these nutrients will be imported as fertilizer, but in later stages of Mars development these will be mined from the air (nitrogen) and from mineral deposits (phosphorous).  Once introduced into the greenhouses of Mars they will be recycled through the human ecosystem of colonists.  Feces from humans are rich in these nutrients and will not be wasted.   The wastewater system described in “Pioneering House Building” will carry such nutrients to a small treatment facility consisting of an aerobic digester.  Inside the digester an army of microbiological servants will dutifully decompose the incoming waste into nutrients for plants.  The solid components of this oxidation process will be added to the compost while the water-soluble nitrogen and phosphorous will be added to the plants directly by watering.  Other needed trace elements may be imported and applied directly to plants (4).

5) Air supply.  On Earth, greenhouses are supplied by outside sir that may be supplied by ventilation from outside air or may be delivered through ducts.  On Mars, air will always be supplied through an HVAC ductwork system.  Special requirements of the makeup air will necessitate a special HVAC unit adapted for Mars to be located in or near to the greenhouse.  For example, a greenhouse can become depleted in CO2 because plants constantly consume it for building the proteins of the growing plant.  A lowered CO2 level doesn’t affect humans but will immediately affect the health of plants.  The atmosphere of Earth normally contains about 400 ppm of CO2 but photosynthesis will cease below 200 ppm (5).  On the other hand, enriching the atmosphere above normal Earth levels will stimulate rapid plant growth.  CO2 levels between 800 ppm and 1500 ppm are optimal, but levels above 2000 ppm become toxic to plants.  Human beings, on the other hand, have a higher tolerance for elevated CO2 levels (6).   No adverse effect is known up to 5 percent, but 5,000-ppm time-weighted average is the Recommended Exposure Level (REL) published by the National Institute of Occupational Safety and Health (NIOSH) for carbon dioxide (7).  

Dry Ice BlockCO2 depletion will be a constant problem when growing plants in an enclosed environment.  Consequently, a method of CO2 enrichment will be employed as a component of the HVAC unit for the greenhouse.  Of the five methods employed on Earth for this purpose, the obvious choice is the introduction of dry ice (solid phase CO2). (5) Carbon dioxide will be scrubbed from the Martian air as a part of the Sabatier process for the colony (See the article “Dr. Sabatier’s Appurtenances”.).  An intermediate step in this process will be the collection and storage of CO2 in a standard Mars stone tank.  In addition to its strategic value, a CO2 storage tank will supply dry ice to the greenhouse as an added benefit.  Where CO2 and H20 are found together in solid form in the cryosphere, CO2 can be collected as a side product of (water) ice mining.  

6) Temperature Control.  The temperature of greenhouse air must be closely regulated to maintain good growing conditions for the particular plants to be raised. (8) In general the desired temperature ranges will vary according to whether warm season or cool season plants will be grown.  Vegetables such as beets, broccoli, cabbage, cauliflower, carrots, chard, kohlrabi, leaf lettuce, green onions, peas, radishes, spinach, and turnips are all cool weather plants.  They will usually flourish when their environment is maintained at daytime temperatures of 55 to 70 degrees F and nighttime temperatures of 45 to 55 degrees F.  Warm season vegetables include beans, cucumbers, eggplant, muskmelons, peppers, zucchini, and tomatoes.  These plants will grow like a teenager in daytime temperatures of 60 to 85 degrees F and nighttime temperatures of 55 to 65 degrees F.  

For most greenhouses the light energy used to stimulate photosynthesis will also generate heat.  In an early Mars colony, artificial lighting will be the major source that could cause overheating.  At the same time, makeup air that is CO2-enriched will be cooled by exposure to dry ice as well as cooled by the HVAC equipment.  Another source of cooling will be the stone floors and walls of the greenhouse itself.  Left alone, the temperature of these surfaces would gradually slide to the temperature of the landmass/cryosphere below the greenhouse.  This tendency will require monitoring to determine if the floor temperatures could adversely affect the temperature of the crop-growing soil of the greenhouse.  Soil temperature will be particular important for seed germination.  If necessary, heating wires may be installed under the plant nursery beds.  To monitor temperature, selected sections of the greenhouse and the incoming air ducts will require thermometers.  

Botrytis Blight7) Humidity.  Not all plants will flourish in tropical humidity.   When warm humid air experiences a drop in temperature below the dew point, water condenses on surfaces.  This creates an environment where plant pathogens can proliferate, such as the mold botrytis or powdery mildew (9).  To combat excessive humidity, greenhouse horticulturists will aim to keep the environment moderately dry.  Humidity counter-measures will include removing standing water, using floor drains, and applying only enough water for plant health.  An important method of humidity control is ventilation.  On Earth, opening side panels or rolling up the sheet plastic can easily ventilate a greenhouse.  Cross ventilation will allow outside air to sweep away excess humidity (2).  On Mars, the forced air ductwork will provide all the “fresh” air that is feasible.  A dehumidifier will be needed as a part of the HVAC equipment in addition to CO2 enrichment, heating, and cooling.  

Radiant Effciencies for Standard Illumination
8)  Lighting.  An overhead layer of stone and regolith will protect early colonists working in the greenhouse.  Consequently, direct lighting by Mars sunlight will not be feasible and will not be attempted.  Sunlight will generate a portion of the village electricity by means of photoelectric panels, initially imported from Earth.  Electricity will then provide the means of lighting up the greenhouse.  While Earth greenhouses use various sources of artificial lighting to supplement the free lighting provided by the sun, only a few use it to completely replace sunlight as will be carried out on Mars (12).   

Greenhouse LightingThe table above shows the efficiencies of various sources of artificial lighting used in horticulture.  Note that the incandescent bulbs that lit up homes for more than a century are the least efficient and the least durable on the list.  High-pressure sodium (HPS) lamps are the most efficient and are very long lasting.  However, other factors will prevent them from becoming the sole light source for a Martian greenhouse. 

A lighting system to replace the sun must provide not only the quantity but also the type of light that plants need.  Human eyes are capable of perceiving light in a narrow band of electromagnetic wavelengths from 390 to 780 nm (10); plants utilize light for photosynthesis in a similar range of wavelengths from 400 to 700 nm (11).  The various types of light-producing devices used in greenhouses provide light within the desired range of wavelengths but unfortunately, none provide the kind of white light that covers the entire range.  HPS lamps, while the most efficient, emit light in a relatively narrow red-yellow band (500-650 nm) and little in the blue range (400 - 450 nm).  They will need to be supplemented by incandescent, metal halide, fluorescent or mercury vapor lamps that that provide more blue light.  

Other factors that determine the effectiveness of a greenhouse lighting scheme are the design of luminaires (includes lamps, reflectors, ballast, and housing), the placement of luminaires within the greenhouse and the planned cycles of lighting duration.  Bursts of lighting may be employed as part of an illumination program.  Different species will require different lighting regimes.  Different stages of growth, such as germination, will also require enhanced illumination conditions (12).  

The horticultural habitat within a greenhouse is sufficiently complex that engineers and horticulturists on Earth must lay out a detailed plan for each greenhouse before the equipment and colonists are shipped to Mars.


Waste Treatment

A waste treatment plan for a Mars colony will begin long before the pioneers step off the landing craft and will continue long after the colony grows and pioneers become settlers.  It needs to be a long term plan because the type of waste treatment adopted early will condition the types of waste treatment that are most feasible at a later stage.

Fist, consider the handling of human waste while traveling through space toward Mars.  The type of wastewater recycling described here for a Mars village will require substantial structures and equipment that may not be feasible to carry along with the colonists en route to the red planet.  In fact, it may be necessary to dump into space a great deal of wastewater to lighten the craft to be landed.  A large load would require more fuel for landing and every kilogram of the load is expensive.  

On the other hand, if we plan to recycle wastewater and if we plan to use composting on Mars, then the wastewater on the spacecraft approaching Mars will be seen as a resource rather than trash.  It is the organic component of this human material that is valuable because of its rarity on Mars.  At the same time the best site for a village should include a large source of water; if water is readily available, then the water portion of the wastewater from the spacecraft will be seen as more expendable and replaceable.  Therefore, to lighten the load for landing, we should remove the water portion by desiccation that will remove the greatest portion of the mass.  This drying-out will be accomplished by exposing the wastewater to outer space.  The remaining material will contain complex organic chemicals, bacteria (especially spore-forming bacteria), and nutritional nitrates and phosphates.  These could be a large portion of the initial fertilizer for the greenhouse rather than importing additional chemical fertilizer.

Waste Storage Area Once on the surface, the colonists will continue to save their wastewater rather than “discarding” it.  The organic waste will not be treated immediately because the water treatment facility will not be constructed immediately.  They will simply designate a location on the surface to store it and the natural conditions on the ground will freeze it almost immediately.  This is not a process of polluting the biosphere because there is no biosphere until the Mars houses are constructed.  It is a matter of delayed waste treatment until such time that the greenhouse treatment facilities are ready to receive waste.  

When we plan the construction of the greenhouse food production and waste-recycling module, what type of waste treatment facility should we provide?  One type that would be least desirable is a traditional anaerobic digester.  This is a well known and frequently used process for treating sludge, consisting of partially treated solids.  This sludge arises from the initial (primary) treatment of wastewater.  It is pumped into a large, tightly sealed tank and allowed to remain for 30 days or more. Anaerobic bacteria, microorganisms that thrive in the absence of oxygen, feed upon the sludge vigorously.  The by-products of anaerobic digestion are methane (desirable for fuel) and hydrogen sulfide (highly undesirable).  The human nose is extremely sensitive to H2S as it responds to the chemical in a concentration as low as 0.02 ppm (13) and can easily induce revulsion towards the “rotten eggs” smell.  A level of 100 ppm is considered immediately dangerous to life and health. (14) Life in an airtight underground dwelling will be difficult, but the introduction of H2S into the air, even if accidental, would be insufferable.  

A desirable waste treatment system for Mars will be completely aerobic in nature and will produce musty, but tolerable odors.  This type of treatment is carried out in a tank similar to a septic tank that is maintained in an aerobic state by constantly pumping air through the tank as shown in the diagram below (15).  An air compressor mounted on the top of the tank pushes air through a tube into the main chamber where aerobic bacteria break down human waste solids into CO2 and H2O over a 24-hour period.  In the second chamber some of the partially treated settled solids are returned to the  water stream of the first tank for further treatment.  The treated water containing some dissolved and suspended solids are sent (by gravity flow) to the next step of treatment.  This small treatment system is designed for a single household and would be appropriate for a single Mars house of four to eight people. 

Aerobic TankA household aerobic tank is sized the same as a septic tank in most state jurisdictions.  For a three-bedroom house two persons per bedroom are assumed, but a safety allowance for unusual flow situations means that a 1000 US gallon (3785 l) minimum size tank is specified (16).  The diagram shows an Earth aerobic tank but some design changes will be required to adapt it to a Mars greenhouse.  Assuming the tank is located within the greenhouse it will be desirable that the top surface of the tank lid is even with the floor of the greenhouse to maximize the usable walking space.  This means that the tank will be at a different elevation from the house; in effect, the greenhouse will be built over the tank.  Stone block construction will be employed to build an aerobic treatment vault, similar to construction of the greenhouse itself.  

An example of an aerobic treatment vault adapted to a Mars greenhouse is shown in the sketch below.  It is a square cube with interior dimensions of 185 cm (62 inches) on each side with an arched ceiling over the top.  The 62-inch nominal water depth is greater than a standard Earth tank of similar volume, which is 43 inches deep.  The extra depth is acceptable because lower gravity will allow solids to stay suspended for a longer time.  A cube shape will minimize the distance from the inlet aeration tube to the nearest wall, thereby causing better aeration throughout the tank.   A cube-shaped tank with an arched ceiling will allow the construction techniques for building the Mars house to be employed here on a smaller scale.  A second scaffold structure will be imported from Earth that is scaled down for this purpose.  

Because this tank will be filled with water rather than air-breathing people, a different method can be employed to seal cracks between the blocks.  As each row of side-wall blocks are laid down, only a minimum of sintering will be required to hold the tank together until water can be pumped into it.  The ceiling, however, will need to be well treated by methalox torch as in house construction.  When construction of the tank is finished, the tank will be completely filled with water up to the keystone.  Water will flow through the wall cracks into the regolith, which is assumed to be at nearly the same temperature as the surrounding subsurface.  As the water flows toward the low temperature zone it will begin to freeze.  As it solidifies, it will seal up the cracks either by creating ice partways into the cracks or by curtailing the water flow by a frozen sphere of ice around the cracks.  Within the subsurface of Mars, H2O will only remain water as long as it is continuously heated. Greenhouse Aerobic Tank

The greenhouse aerobic tank has many of the same features as the Earth aerobic tank in the previous figure.  Air is pumped into the tank near the bottom and near the partition wall (not shown in the end view).  In the Mars adaptation, however, the air is heated before it is pumped into the tank.  This is to ensure that the water in the tank is maintained in liquid form and does not ice up.  An ideal temperature for bacterial activity will between 60 and 120 degrees F.  A thermometer may be lowered into the tank to monitor the temperature.  Note that one of the keystones, the last block set into the top of the tank in each row, is not sealed by sintering, but is left loose to use as an access port.  It will be located inside the housing for the air pump and heater to allow access to the air injection tube.  To work safely, the floor tiles and other blocks around the keystone will need to be airtight. The presence of a non-airtight access port means that the air inside the greenhouse will be shared with the air above the waterline in the aerobic tank.  The combined volumes must be airtight.  

Another way in which the greenhouse tank differs from the Earth tank is the method of flow out of the vault.  In the Earth tank the water flows by gravity to the next treatment step, which is usually a drain-field.  Alternatively, it may flow into a secondary tank where it is then pumped through a water line and sprayed onto agricultural land.  In the Mars version the treated water is pumped into the composting operation. Note that a float valve is used to detect when the water is at a high level and triggers the pump.  When the float drops to a low level the pump turns off.  

Properly Composted SoilThe greenhouse composting operation will adopt the Berkley method (17) of hot composting whereby materials containing organic carbon and nitrogen and decomposed at 45 to 55 degrees C (130 to 160 degrees F).  The heat is supplied strictly by the intense biochemical action of thermophilic bacteria; extended heating at this level is a cooking process that destroys unwanted seeds that may be present in the compost.  It also acts to kill pathogens by an action similar to pasteurization.  If the process is well managed, the waste material is converted into a desirable soil for plants in 14 to 18 days. (17,18)  

C:N RatiosComposting can be carried out in a bin or a revolving barrel as an anaerobic process, but the Berkeley method requires that the composting be conducted within in a mulch pile (stack) upon an open surface to maintain aerobic conditions.  Other requirements (18) are as follows:

  1.  Temperature must be maintained between 55 and 65 degree C.  Use a mulch pile thermometer to monitor temperature in the center of the pile.
  2. The carbon: nitrogen ratio must be maintained at 25:1 to 30:1.  The high-carbon materials are sawdust, cardboard, dried leaves, straw, or other woody, brown materials; in other words, they are materials not easily found on Mars.  Materials that are high in nitrogen are typically moist, green organic materials, such as grass, fruit and vegetable scraps, and animal manure.  If you substitute “human” for “animal” then high nitrogen materials will be common in the biosphere of Mars.
  3.  The compost pile is approximately 1.5 m high. 
  4.  Material is high in carbon must be broken up or mulched.
  5.  The pile must be turned inside out to mix the material thoroughly and to maintain even bacterial action throughout.  

The 18-day procedure is:

Day 1: Build the mulch pile

Days 1 through 4: Let the pile heat up with no turning

Days 5 through 18: Turn the pile every other day

The process of “turning” is not a casual act but must be performed with skill. A shovel or pitchfork is used to separate the outside (cooler) layer and place it into a second stack.  Then the interior (hot portion) of the first stack is placed around the outside of the second stack.  

Before turning the stack, the temperature of the interior will be checked.  If is below 55 degrees C then the stack is probably low in nitrogen and one of the items in the adjacent list called “High Nitrogen” should be added to the new stack.   This will be easy to remedy, as the treated wastewater from the aerobic tank will be very high in nitrogen.  This can be added to the pile as a liquid.  However, Sludge Driving Bedsif the temperature is above 65 degrees C then items from the high carbon list need to be added to the stack.  This will present a problem to a newly established village because the only high carbon materials on Mars will be the stocks and leaves from plants that are grown in the greenhouse and none will exist at that time.  

As a short-term measure it will be necessary to adopt an alternate procedure to a compost stack.  Pump the treated waste into the bare floors of the future growing beds of the greenhouse.  These should be a series of bins with low stone block walls.  A thin wet film of water with suspended solids should form over a wide area inside the bins.  Some of the bins will be designated for the growing of swamp grass and the other bins will become sludge drying beds.  Sludge drying beds are employed in some Earth waste treatment facilities.  Keep the greenhouse as low in humidity as possible with a warm temperature to allow the sludge to dry as quickly as possible; then when it mostly dried, scrape it into buckets and carry it to the outdoors waste collection area, to be treated more completely at a later time.  

The purpose of growing swamp grass will be to produce high carbon straw as quickly as possible.  Swamp grass is a generic term that includes many plants that may be grown as ornamentals. (19) In this case we are looking for plants that grow rapidly in swamp-like conditions akin to the flooded growing bins in a Mars greenhouse.  Some of the prospective grasses are (20):  

Andropogon glomeratus (Bushy Beard) is a moisture-loving plant usually found growing in low-lying marshes of the eastern coastal plain of the US. It grows above 3 feet in upright clumps that display silvery feather-like seed panicles.

Tall Swamp Grass Carrel stricta (Tussock Sedge) is fine textured sedge that rises above the water line of a pond or swamp. Tussock sedge arches out of its dense tussock, giving it the appearance of fountain grass.  It thrives in full sun and stands 1-3tall. It is a true ornamental for a water garden.

Ceratophyllum demersum (Hornwort) is a US native submergent plant with little or no roots anchoring it to the bottom. Instead it forms dense mats that float suspended in the water.  Hornwort is an evergreen with stiff branching stems and whorled leaves.  A portion of the plant can be introduced into another body of water as a starter (or into another bin of the Martian greenhouse).

Cinna arundinacea  (Wood Reedgrass) grows well in fertile moist soil with light shade. Most growth occurs during the summer when it reaches 3-5 feet tall. It lives as scattered individual plants or in small colonies. Native habitats include wooded floodplains and swamps.  

This brief list us only a sampling of the possible species that might thrive in the Martian greenhouse in a shallow basin of nutrient water.  At this time none have been tested under Martian conditions.  A colonization plan should include importing a variety of seeds that may fulfill the need for rapidly growing plants that can produce straw.  Note that trees and bushes were excluded from the list because they are presumed to grow more slowly in shallow water or not at all.

Once the swamp grass has grown sufficiently, leaves and branches should be cut and set aside to dry.  A small compost stack may be started with this straw as the high-carbon component.  As this stack is developed into compost it can be used to grow more fibrous materials and perhaps a few experimental vegetables.  Within a year a backlog of high carbon materials should be available which will represent the real beginning of the greenhouse operation.


On Mars, farmland will consist entirely of the crop-growing space of a greenhouse. The greenhouse will employ principles of horticulture as practiced on Earth and also processes adapted to Mars. These processes will address water supply soil base, soil conditioner, nutrients, air supply, temperature control, humidity control, and lighting, The greenhouse will not only produce crops, but will also provide waste treatment.  This will entail an aerobic tank built of stone like a Mars house and a compost facility using the Berkley Method. 




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  19.  “Types of swamp grasses,” Retrieved 6-7-2014.
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