In the upcoming billions of years, it will be obligatory for the humans to migrate to other planets because of expected nuclear wars, and furthermore the sun will become too hot for Earth to carry on life. In this context, Mars is ideal with an environment appropriate for human colonization and potential for modification into a stable ecosystem in the far future.
As a result of human colonization on Mars, it is obvious that these colonies can not be totally dependent on Earth for life support especially with relations to the food perspectives. The concept of greenhouse used on Earth to provide a confined space maintained at desirable environmental conditions for plant growth, can be extended to applications on the surface of Mars also. Furthermore, the psychological benefits associated with the sensory value of fresh food and of cultivating plants make greenhouses important components of manned missions to Mars.
Adopted from: http://www.radarstat.space.gc.ca
The greenhouse designed for the Mars must be structurally sound and be able to sustain desired interior climate in the presence of exterior climates with very low pressures and temperatures. The overall greenhouse system should be designed in a way that the interaction of plants with greenhouse system such as ventilation and overall water cycle may work properly and furthermore physiological requirements for the plant growth such as light, temperature, internal pressure and humidity may be maintained in the desired limits. Short window of operation to conduct maintenance and service, extreme environment for plant growth, limited electrical power production and heat generation, and low-bandwidth communication for remote monitoring and control are the challenges to overcome while making the greenhouses on the Mars. Leafy vegetables are the first potential crops being experimented to grow in the Martian greenhouses with hydroponic or aeroponic systems. Thus to find the solution of many challenges in this regard, I did a case study research project last year with my Turkish colleague Deniz Sanal under the kind supervision of Dr. Jeremy Harbinson while studying at Wageningen University, The Netherlands. The prime objective of this research was to assess the possibilities of making Greenhouse on the Mars by analysing the various concerned factors through physical, technological and eco-physiological approach. The purpose of publishing this case study research here on this blog is to feed the curious and hungry minds anxious to make their moves towards Mars.
Factors which affect the preparation and success of Greenhouse on the Mars are Day length, Internal pressure, Water, Light, Temperature, and Greenhouse structural design. So each factors is discussed here separately to get the facts more clear.
Day Length
Axial tilt and rotation period of Mars are similar to those of Earth and it experiences the seasons of spring, summer, autumn and winter much like Earth and its day is of about the same length. The average length of a Martian solar day (Sol) is 24 hours and 37 minutes which is only about 2.7% longer than Earth’s. Martian year is tracked by the use of ‘seasonal longitude’ abbreviated as Ls, the position of Mars in its orbit around the sun. The time length for Mars to complete one orbit around the sun is its sidereal year, and is about 686.98 Earth solar days or 668.5991 sols. It is equal to 1.8809 Earth year or 1 year, 320 days and 18.2 hours. Due to eccentricity of Mars orbit, the seasons are not of equal length, with northern hemisphere spring the longest season (Ls = 0-90), lasting 194 Martian sols, and northern hemisphere autumn (Ls = 180-270), the shortest, lasting only 142 Martian sols.
Hence the day length variation is of utmost importance while selecting the appropriate greenhouse structural design, crops and location for the installation of these greenhouses. Besides these considerations, it will significantly affect the crop physiological aspects because light, temperature and even internal pressure will be changing with the day length or seasonal variation. Furthermore seeding, pollination, harvesting, energy conservation in the summer for the winter harsh conditions, maintenance and overhaul operations can be well planned according to the day length and seasonal variation on the Mars as it is currently being done in the Arthur Clarke Mars Greenhouse located on the Canadian Arctic Devon Island.
Internal pressure
The plant consideration that has the largest impact on structural design is the internal pressure of the greenhouse. The total minimum internal pressure is the sum of the partial pressures of carbon dioxide, water vapor and oxygen inside the greenhouse. The overall atmospheric pressure of Mars is very low as compared to that of Earth. The partial pressure of carbon dioxide in Earth’s atmosphere is 0.035 kPa. The partial pressure of carbon dioxide in the Martian atmosphere is about 0.57 kPa. The partial pressure of water vapor in Earth’s atmosphere indicated as the vapor pressure varies with temperature and relative humidity. At comfortable room conditions of 25°C and 50% relative humidity, the vapor pressure for Earth’s atmosphere is 1.6 kPa. However total surface pressure of Mars is 0.6 kPa which is too low.
Experments conducted on Arabidopsis thaliana under different low pressure coditions just like Mars show that Plant net photosynthesis (Pnet) will relatively be unaffected if CO2 concentrations are kept elevated on the Mars surface. Plant growth modules must be operated around 10 kPa without undue inhibition of photosynthese and surface pressure of at least 10 kPa (100 mbar) is required for the normal growth of deployed plant species. Plants are able to survive even less than 10 kPa and their Pnet and Enet (net evapotranspiration) continues to increase with the decrease in pressure except wheat however these effects might be short termed. Thus carbon fixation and plant growth rate might be enhanced at low pressure. Further, while looking at different physical and metabolic processes concerned with plant biology and physiology, we come to know that diffusion of CO2 and O2 gases also increases with the decrease in internal pressure across plant leaves resulting in increased CO2 assimilation. Changes in boundary layer effects might lead to changes in leaf conductance at low pressures, and may enhance Pnet by reducing the resistance to the diffusion of gases at the leaf surface. Low pressure also affects the photorespiration significantly and Pnet in C3 plants can also be enhanced highly at low pressure.
Besides this the possibilities to create internal pressure also vary with the greenhouse structural design. The Mars atmosphere contains 0.1% ( 0.0006 kPa ) N2 and 0.07 % CO. If we assume that this ratio is constant and the total atmospheric pressure increases to 100 kPa, then the concentration of O2 will be 0.1 kPa. This O2 amount is close to the levels needed for plants but the CO level will be 0.07 kPa which is seven times the limit for the humans, plants and microorganisms can survive. The amount of atmospheric N2 must be enough as well to provide the biological nitrogen fixation. The experiments show that bacteria can fix N2 at levels of 0.5 kPa but the current pressure of N2 on Mars is about 0.02 kPa. Theoretical considerations and observations suggest that Mars must have had much larger quantities of N2 , CO2 and H2O. Thus the internal pressure of greenhouse can be balanced to desirable amounts. However it still needs a lot of brainstorming to find out the exact figures for the Martian greenhouses.
Water
Presence of water on Mars has been confirmed by the recent observations of NASA’s Mars Exploration Rovers and ESA’s Mars Express. Water is truly vital for plant growth. To review basic plant physiology; a tiny amount of water is used in photosynthesis to make sugar. The rest is used to carry the sugar through the plant to where it is needed. Scientists have long studied the possibility of water on Mars, analyzing evidence that suggests liquid water existed on the Mars in the past. Recent evidence of gullies formed, raises the possibility of liquid water on or near the surface of Mars but still there is no real evidence about the existence of water. However there is a direct evidence that early in Martian history, liquid water was stable and present at the surface. The large flood features on Mars indicate that the total stock of water was considerable.
In the light of the information about the water existence on Mars, one good idea be the formation of liquid water artificially for plant growth under laboratory conditions. As it’s known the molecular formula of water is H2O. The needed oxygen for this basic formula can be obtained via decomposition of the carbon dioxide molecules into carbon and oxygen, and hydrogen can be obtained by the Martian atmosphere or the oxidation of hydrocarbons like CH4 which has been already detected in the surface atmosphere of Mars.
After getting the liquid water, water management in the greenhouse is an important aspect for the successful crop growth. Most of the water used by an irrigated crop is drawn through the roots and transpires through the leaves. Only small amount (more or less 0.1%) of the water taken up by plants will actually be used to produce plant tissue. Evapotranspiration is an important part of the water cycle. Stomates are fully open when plants receive enough water through the soil and when both transpiration and photosynthesis are occurring at maximum rates. If soil water becomes limiting, stomates begin to close causing a decrease in transpiration and photosynthesis. The control of humidity is essential as well. In the greenhouse, warm air holds the moisture in the vapor form. At night as the air cools to the dew point, condensation occurs and water droplets are formed on cooler surfaces such as the leaves and greenhouse surfaces. A balance must be kept in the water cycle in the greenhouse by the help of heating and ventilation keeping the photosynthesis and evapotranspiration at economical levels. Water must be recycled through different techniques to overcome the water scarcity for the plant growth in the Martian greenhouse. The Penman-Monteith equation is helpful in this regard, which is:
Light
The sunshine is not bright enough on Mars to let usual Earth plants to prosper, still it provides a valuable part of light energy for plants. However additional energy will be obligatory for the sake of lighting, heating, monitoring and other necessary greenhouse operations. For this purpose solar collectors are the first option. A solar collector consists of four major parts: the light concentrating and filtering device, light transport device, and the casing or the structure of the system. Of these four major parts, the light concentrating and filtering device is the most important. The function of this device is to take light efficiently from the sun and concentrate the visible spectrum onto the ends of fiber optic cables while filtering out the harmful ultraviolet and infrared wavelengths. The tracking system can be either single-axis for daily solar tracking or dual axis for both daily and seasonal solar tracking. When this system is used as the primary light source for the crop production module, it is necessary to maximize the collection of light. Therefore a dual-axis (figure shown below) tracking system is the superior choice. The function of the casing of the solar collector is to protect the collector from the harsh Martian environment, including extremely cold temperatures, magnetic dust, and harmful radiation. Material selection for the casing is based on expected performance in such extreme environmental conditions. The solar collectors with fiber optic system are the best option for the underground greenhouse structures on the Mars surface. Beside this, transparent material allowing maximum sunlight to pass should be used in the construction of greenhouse. The spectral properties of the material should be optimized to match the absorption characteristics of chlorophyll, maximizing the energy gain. A set of mirrors might be a good option to bring more sunlight into the greenhouse than the base area of the greenhouse receives directly from the sun. Three times the amount of Martian sunlight should be adequate to serve terrestrial plants.
Plant photosynthesis does not respond to the entire spectrum of light. Values of Photosynthetically Active Radiation (PAR) levels are needed for Mars. Ambient light levels on Mars are high enough to sustain plant growth. However, because of the extremely low temperatures and pressures, any plant production must be conducted inside an enclosure. Even the best clear wall material for an enclosure will reduce light levels. The ideal wall material would allow transmittance into the structure of the wavelengths above 400 nm at angles of incidence from zero to 90° and zero transmittance out of the structure for all thermal wavelengths beyond 3000 nm. Glass is transparent to visible wavelengths of light and opaque to infrared wavelength and is an ideal wall material for greenhouses. Unfortunately, many plastic films such as the common greenhouse films of polyethylene are transparent to infrared radiation. The radiation characteristics of wall materials must be carefully selected to optimize transmission of Photosynthetically Active Radiation and block as much radiation in the infrared range as possible. To get the maximum transmittance level with keeping heat loss at tolerable levels would be one of the important challenges in the formation of greenhouse on Mars. The interactions between low density atmosphere, internal pressure, wind speed and convection and conduction processes are of high importance in this respect and need to be analysed properly before making any practical decision. Beside this, an underground greenhouse (Figure shown below) would be easier to insulate and hold warmth inside on the expense of more efforts for lighting since then no direct sunlight will be available for use. The ambient light with artificial lighting might be necessary to use for the satisfactory plant growth. LEDs (Light emitting Diodes) are the best option for providing the plants favourite blue and red radiations helping a lot in their photosynthesis process. The extra power required for artificial lighting can also be generated by the heat produced by the LEDs.
Adopted from: http://www.marspedia.org/
Temperature
Temperatures will rise and fall in very rapid synchronicity with the sun because, unlike on Earth, the thin atmosphere and lack of water do very little to buffer temperature fluctuations. The dominant environmental parameter in a Martian greenhouse will be temperature. The average surface temperature on Mars is approximately -63°C with an average diurnal range of around -103°C to 5°C. The diurnal temperature range observed by the Viking 1 Lander (the first of two spacecrafts sent to Mars) was -89° C to -32°C. Temperatures may rise above freezing during the summer at the equator. Daytime temperatures in the summer at the equator may be suitable for plant growth, but nighttime temperatures are far below the temperature range where plants can survive. Thus any plant growth on Mars must take place in the heated environments.
Significant quantities of solar energy are available on the Martian surface, but as on Earth, the solar energy on Mars is not always available when required and is never available at night. If supplemental lighting is used in greenhouse, cooling may be necessary because electrical lights produce very large quantities of waste heat. Furthermore a heating system will be necessary at night. There may be times during daylight hours that enough solar energy is available to maintain desired temperatures. The inside temperature of greenhouse should be optimal (10-30oC) for the plant growth. Hence the temperature should be regulated at least between this temperature ranges.
The control of relative humidity due to temperature variations is essential as well. In the greenhouse the warm air holds the moisture in the vapor form. At night as the air cools to the dew point, condensation occurs and water droplets are formed on cooler surfaces such as the leaves and glazing. This moisture causes the germination of fungal pathogen spores. Dripping water from condensation on the greenhouse covering also wets plant surfaces and spreads plant pathogens from plant to plant by splashing soil. To keep the plant canopy dry with a controlled humidity level suppresses the diseases. Thus a ventilation and heating system will also be required to control the temperature variations and keep the water balance inside the greenhouse.
Greenhouse structural design
The type of greenhouse structure that might be used for plant production on Mars vary from small automatically deployed structures with a small number of plants for research purposes to larger structures that would be used to grow plants to feed human colonies on the Mars. Structure requirements will vary accordingly to different size and purpose of the greenhouse; however function of the greenhouse will be same to produce the plants successfully. To determine loads is the first step in the greenhouse structural design. Dead loads will be considerably less than Earth because of less Martian gravity (0.38 of the Earth gravity). The density of Mars atmosphere is 0.01 that of Earth, so the wind loads are expected to be small on the deployable Martian greenhouse. However in the major storm conditions, the fast air velocity combined with lower Martian gravity can create a risk of uplifting or overturning of light greenhouse structures. The wind loads on the structure can be calculated from the following relation.
q = (1/2ρV2)Cd
where
q = pressure on the vertical falt plate, Pa
ρ = air density, kg/m3
V = air velocity, m/s
Cd = drag coefficient
Inflatable greenhouse structures with curved geometry are focus of different studies for Lunar and martian use. Inflatable structures are a type of tensile structure which includes tents and other structures fabricated using membranes as structural elements. Membranes only carry tensile loads in the plane of the shell or fabric and can not carry compressive or bending loads. The main load on this Martian greenhouse will be imposed by the internal pressure while gravity and wind loads will be smaller. The greenhouse wall must be thin, transparent and light weight with good strength against different stresses. Furthermore design must provide itself to being stored in a folded configuration and then automatically deployed into its functional configuration. The wall material must also be capable of being folded and be able to be automatically unfolded into the functional configuration. The curved shape of the Martian greenhouse seems more effective because its lower surface area to volume ratios which might be beneficial when considering the heat loss through the wall surfaces but it might also be of disadvantage when considering the light collection.
The underground structures seem more effective, safe and durable with multiple advantages of shielding the plants and colonists against harmful radiations, supporting the structures, moderating the environmental variations present on Mars surface and providing the shirt- sleeve environment with an atmosphere of 101.3 kPa to the colonists in which they can work normally without their space suits. This type of greenhouse might be installed at a depth of 4 m below the Martian surface. It must provide the enough floor space for irrigation, heating, electrical and other greenhouse related systems. Some structures of been shown below get a clear idea of the discussion.
Adopted from: http://www.marsonearth.org
Adopted from: http://www.science.ksc.nasa.gov
Adopted from: http://www.marsonearth.org
Adopted from: http://www.grcimagenet.grc.nasa.gov
Conclusions
To conclude the story, it is possible to make the greenhouse on Mars. Reductions in atmospheric pressure, light, temperature, water and day length and seasonal variations are the challenges to face in this regard. Maintenance of minimum internal pressure 10 kpa for good plant production, use of solar collectors and hybrid solar wind system for enegry collection and generation, control on evapotranspiration rate useful for greenhouse design and management related decisions, and use of underground structures due to their multiple advantages are the certain remedies of these challenges in the way of making greenhouse on Mars. Further, leafy vegetables, aeroponics, and control on dust and wind problems are the other important considerations.
In the end, I'm confident to claim that this research will open the doors for Plant Physiologists to join astronauts while exploring Mars. But It's still the idea, centuries are needed to see something practical on Mars.............!
Note: It was not possible for me to make the Greenhouse on Mars completely myself. So all above data including text and pictures, was compiled from different sources. I need your feedback to know the strength of my effort, so please comment freely and generously.
Adopted from: http://www.radarstat.space.gc.ca
The greenhouse designed for the Mars must be structurally sound and be able to sustain desired interior climate in the presence of exterior climates with very low pressures and temperatures. The overall greenhouse system should be designed in a way that the interaction of plants with greenhouse system such as ventilation and overall water cycle may work properly and furthermore physiological requirements for the plant growth such as light, temperature, internal pressure and humidity may be maintained in the desired limits. Short window of operation to conduct maintenance and service, extreme environment for plant growth, limited electrical power production and heat generation, and low-bandwidth communication for remote monitoring and control are the challenges to overcome while making the greenhouses on the Mars. Leafy vegetables are the first potential crops being experimented to grow in the Martian greenhouses with hydroponic or aeroponic systems. Thus to find the solution of many challenges in this regard, I did a case study research project last year with my Turkish colleague Deniz Sanal under the kind supervision of Dr. Jeremy Harbinson while studying at Wageningen University, The Netherlands. The prime objective of this research was to assess the possibilities of making Greenhouse on the Mars by analysing the various concerned factors through physical, technological and eco-physiological approach. The purpose of publishing this case study research here on this blog is to feed the curious and hungry minds anxious to make their moves towards Mars.
Factors which affect the preparation and success of Greenhouse on the Mars are Day length, Internal pressure, Water, Light, Temperature, and Greenhouse structural design. So each factors is discussed here separately to get the facts more clear.
Day Length
Axial tilt and rotation period of Mars are similar to those of Earth and it experiences the seasons of spring, summer, autumn and winter much like Earth and its day is of about the same length. The average length of a Martian solar day (Sol) is 24 hours and 37 minutes which is only about 2.7% longer than Earth’s. Martian year is tracked by the use of ‘seasonal longitude’ abbreviated as Ls, the position of Mars in its orbit around the sun. The time length for Mars to complete one orbit around the sun is its sidereal year, and is about 686.98 Earth solar days or 668.5991 sols. It is equal to 1.8809 Earth year or 1 year, 320 days and 18.2 hours. Due to eccentricity of Mars orbit, the seasons are not of equal length, with northern hemisphere spring the longest season (Ls = 0-90), lasting 194 Martian sols, and northern hemisphere autumn (Ls = 180-270), the shortest, lasting only 142 Martian sols.
Hence the day length variation is of utmost importance while selecting the appropriate greenhouse structural design, crops and location for the installation of these greenhouses. Besides these considerations, it will significantly affect the crop physiological aspects because light, temperature and even internal pressure will be changing with the day length or seasonal variation. Furthermore seeding, pollination, harvesting, energy conservation in the summer for the winter harsh conditions, maintenance and overhaul operations can be well planned according to the day length and seasonal variation on the Mars as it is currently being done in the Arthur Clarke Mars Greenhouse located on the Canadian Arctic Devon Island.
Internal pressure
The plant consideration that has the largest impact on structural design is the internal pressure of the greenhouse. The total minimum internal pressure is the sum of the partial pressures of carbon dioxide, water vapor and oxygen inside the greenhouse. The overall atmospheric pressure of Mars is very low as compared to that of Earth. The partial pressure of carbon dioxide in Earth’s atmosphere is 0.035 kPa. The partial pressure of carbon dioxide in the Martian atmosphere is about 0.57 kPa. The partial pressure of water vapor in Earth’s atmosphere indicated as the vapor pressure varies with temperature and relative humidity. At comfortable room conditions of 25°C and 50% relative humidity, the vapor pressure for Earth’s atmosphere is 1.6 kPa. However total surface pressure of Mars is 0.6 kPa which is too low.
Experments conducted on Arabidopsis thaliana under different low pressure coditions just like Mars show that Plant net photosynthesis (Pnet) will relatively be unaffected if CO2 concentrations are kept elevated on the Mars surface. Plant growth modules must be operated around 10 kPa without undue inhibition of photosynthese and surface pressure of at least 10 kPa (100 mbar) is required for the normal growth of deployed plant species. Plants are able to survive even less than 10 kPa and their Pnet and Enet (net evapotranspiration) continues to increase with the decrease in pressure except wheat however these effects might be short termed. Thus carbon fixation and plant growth rate might be enhanced at low pressure. Further, while looking at different physical and metabolic processes concerned with plant biology and physiology, we come to know that diffusion of CO2 and O2 gases also increases with the decrease in internal pressure across plant leaves resulting in increased CO2 assimilation. Changes in boundary layer effects might lead to changes in leaf conductance at low pressures, and may enhance Pnet by reducing the resistance to the diffusion of gases at the leaf surface. Low pressure also affects the photorespiration significantly and Pnet in C3 plants can also be enhanced highly at low pressure.
Besides this the possibilities to create internal pressure also vary with the greenhouse structural design. The Mars atmosphere contains 0.1% ( 0.0006 kPa ) N2 and 0.07 % CO. If we assume that this ratio is constant and the total atmospheric pressure increases to 100 kPa, then the concentration of O2 will be 0.1 kPa. This O2 amount is close to the levels needed for plants but the CO level will be 0.07 kPa which is seven times the limit for the humans, plants and microorganisms can survive. The amount of atmospheric N2 must be enough as well to provide the biological nitrogen fixation. The experiments show that bacteria can fix N2 at levels of 0.5 kPa but the current pressure of N2 on Mars is about 0.02 kPa. Theoretical considerations and observations suggest that Mars must have had much larger quantities of N2 , CO2 and H2O. Thus the internal pressure of greenhouse can be balanced to desirable amounts. However it still needs a lot of brainstorming to find out the exact figures for the Martian greenhouses.
Water
Presence of water on Mars has been confirmed by the recent observations of NASA’s Mars Exploration Rovers and ESA’s Mars Express. Water is truly vital for plant growth. To review basic plant physiology; a tiny amount of water is used in photosynthesis to make sugar. The rest is used to carry the sugar through the plant to where it is needed. Scientists have long studied the possibility of water on Mars, analyzing evidence that suggests liquid water existed on the Mars in the past. Recent evidence of gullies formed, raises the possibility of liquid water on or near the surface of Mars but still there is no real evidence about the existence of water. However there is a direct evidence that early in Martian history, liquid water was stable and present at the surface. The large flood features on Mars indicate that the total stock of water was considerable.
In the light of the information about the water existence on Mars, one good idea be the formation of liquid water artificially for plant growth under laboratory conditions. As it’s known the molecular formula of water is H2O. The needed oxygen for this basic formula can be obtained via decomposition of the carbon dioxide molecules into carbon and oxygen, and hydrogen can be obtained by the Martian atmosphere or the oxidation of hydrocarbons like CH4 which has been already detected in the surface atmosphere of Mars.
After getting the liquid water, water management in the greenhouse is an important aspect for the successful crop growth. Most of the water used by an irrigated crop is drawn through the roots and transpires through the leaves. Only small amount (more or less 0.1%) of the water taken up by plants will actually be used to produce plant tissue. Evapotranspiration is an important part of the water cycle. Stomates are fully open when plants receive enough water through the soil and when both transpiration and photosynthesis are occurring at maximum rates. If soil water becomes limiting, stomates begin to close causing a decrease in transpiration and photosynthesis. The control of humidity is essential as well. In the greenhouse, warm air holds the moisture in the vapor form. At night as the air cools to the dew point, condensation occurs and water droplets are formed on cooler surfaces such as the leaves and greenhouse surfaces. A balance must be kept in the water cycle in the greenhouse by the help of heating and ventilation keeping the photosynthesis and evapotranspiration at economical levels. Water must be recycled through different techniques to overcome the water scarcity for the plant growth in the Martian greenhouse. The Penman-Monteith equation is helpful in this regard, which is:
Light
The sunshine is not bright enough on Mars to let usual Earth plants to prosper, still it provides a valuable part of light energy for plants. However additional energy will be obligatory for the sake of lighting, heating, monitoring and other necessary greenhouse operations. For this purpose solar collectors are the first option. A solar collector consists of four major parts: the light concentrating and filtering device, light transport device, and the casing or the structure of the system. Of these four major parts, the light concentrating and filtering device is the most important. The function of this device is to take light efficiently from the sun and concentrate the visible spectrum onto the ends of fiber optic cables while filtering out the harmful ultraviolet and infrared wavelengths. The tracking system can be either single-axis for daily solar tracking or dual axis for both daily and seasonal solar tracking. When this system is used as the primary light source for the crop production module, it is necessary to maximize the collection of light. Therefore a dual-axis (figure shown below) tracking system is the superior choice. The function of the casing of the solar collector is to protect the collector from the harsh Martian environment, including extremely cold temperatures, magnetic dust, and harmful radiation. Material selection for the casing is based on expected performance in such extreme environmental conditions. The solar collectors with fiber optic system are the best option for the underground greenhouse structures on the Mars surface. Beside this, transparent material allowing maximum sunlight to pass should be used in the construction of greenhouse. The spectral properties of the material should be optimized to match the absorption characteristics of chlorophyll, maximizing the energy gain. A set of mirrors might be a good option to bring more sunlight into the greenhouse than the base area of the greenhouse receives directly from the sun. Three times the amount of Martian sunlight should be adequate to serve terrestrial plants.
Plant photosynthesis does not respond to the entire spectrum of light. Values of Photosynthetically Active Radiation (PAR) levels are needed for Mars. Ambient light levels on Mars are high enough to sustain plant growth. However, because of the extremely low temperatures and pressures, any plant production must be conducted inside an enclosure. Even the best clear wall material for an enclosure will reduce light levels. The ideal wall material would allow transmittance into the structure of the wavelengths above 400 nm at angles of incidence from zero to 90° and zero transmittance out of the structure for all thermal wavelengths beyond 3000 nm. Glass is transparent to visible wavelengths of light and opaque to infrared wavelength and is an ideal wall material for greenhouses. Unfortunately, many plastic films such as the common greenhouse films of polyethylene are transparent to infrared radiation. The radiation characteristics of wall materials must be carefully selected to optimize transmission of Photosynthetically Active Radiation and block as much radiation in the infrared range as possible. To get the maximum transmittance level with keeping heat loss at tolerable levels would be one of the important challenges in the formation of greenhouse on Mars. The interactions between low density atmosphere, internal pressure, wind speed and convection and conduction processes are of high importance in this respect and need to be analysed properly before making any practical decision. Beside this, an underground greenhouse (Figure shown below) would be easier to insulate and hold warmth inside on the expense of more efforts for lighting since then no direct sunlight will be available for use. The ambient light with artificial lighting might be necessary to use for the satisfactory plant growth. LEDs (Light emitting Diodes) are the best option for providing the plants favourite blue and red radiations helping a lot in their photosynthesis process. The extra power required for artificial lighting can also be generated by the heat produced by the LEDs.
Adopted from: http://www.marspedia.org/
Temperature
Temperatures will rise and fall in very rapid synchronicity with the sun because, unlike on Earth, the thin atmosphere and lack of water do very little to buffer temperature fluctuations. The dominant environmental parameter in a Martian greenhouse will be temperature. The average surface temperature on Mars is approximately -63°C with an average diurnal range of around -103°C to 5°C. The diurnal temperature range observed by the Viking 1 Lander (the first of two spacecrafts sent to Mars) was -89° C to -32°C. Temperatures may rise above freezing during the summer at the equator. Daytime temperatures in the summer at the equator may be suitable for plant growth, but nighttime temperatures are far below the temperature range where plants can survive. Thus any plant growth on Mars must take place in the heated environments.
Significant quantities of solar energy are available on the Martian surface, but as on Earth, the solar energy on Mars is not always available when required and is never available at night. If supplemental lighting is used in greenhouse, cooling may be necessary because electrical lights produce very large quantities of waste heat. Furthermore a heating system will be necessary at night. There may be times during daylight hours that enough solar energy is available to maintain desired temperatures. The inside temperature of greenhouse should be optimal (10-30oC) for the plant growth. Hence the temperature should be regulated at least between this temperature ranges.
The control of relative humidity due to temperature variations is essential as well. In the greenhouse the warm air holds the moisture in the vapor form. At night as the air cools to the dew point, condensation occurs and water droplets are formed on cooler surfaces such as the leaves and glazing. This moisture causes the germination of fungal pathogen spores. Dripping water from condensation on the greenhouse covering also wets plant surfaces and spreads plant pathogens from plant to plant by splashing soil. To keep the plant canopy dry with a controlled humidity level suppresses the diseases. Thus a ventilation and heating system will also be required to control the temperature variations and keep the water balance inside the greenhouse.
Greenhouse structural design
The type of greenhouse structure that might be used for plant production on Mars vary from small automatically deployed structures with a small number of plants for research purposes to larger structures that would be used to grow plants to feed human colonies on the Mars. Structure requirements will vary accordingly to different size and purpose of the greenhouse; however function of the greenhouse will be same to produce the plants successfully. To determine loads is the first step in the greenhouse structural design. Dead loads will be considerably less than Earth because of less Martian gravity (0.38 of the Earth gravity). The density of Mars atmosphere is 0.01 that of Earth, so the wind loads are expected to be small on the deployable Martian greenhouse. However in the major storm conditions, the fast air velocity combined with lower Martian gravity can create a risk of uplifting or overturning of light greenhouse structures. The wind loads on the structure can be calculated from the following relation.
q = (1/2ρV2)Cd
where
q = pressure on the vertical falt plate, Pa
ρ = air density, kg/m3
V = air velocity, m/s
Cd = drag coefficient
Inflatable greenhouse structures with curved geometry are focus of different studies for Lunar and martian use. Inflatable structures are a type of tensile structure which includes tents and other structures fabricated using membranes as structural elements. Membranes only carry tensile loads in the plane of the shell or fabric and can not carry compressive or bending loads. The main load on this Martian greenhouse will be imposed by the internal pressure while gravity and wind loads will be smaller. The greenhouse wall must be thin, transparent and light weight with good strength against different stresses. Furthermore design must provide itself to being stored in a folded configuration and then automatically deployed into its functional configuration. The wall material must also be capable of being folded and be able to be automatically unfolded into the functional configuration. The curved shape of the Martian greenhouse seems more effective because its lower surface area to volume ratios which might be beneficial when considering the heat loss through the wall surfaces but it might also be of disadvantage when considering the light collection.
The underground structures seem more effective, safe and durable with multiple advantages of shielding the plants and colonists against harmful radiations, supporting the structures, moderating the environmental variations present on Mars surface and providing the shirt- sleeve environment with an atmosphere of 101.3 kPa to the colonists in which they can work normally without their space suits. This type of greenhouse might be installed at a depth of 4 m below the Martian surface. It must provide the enough floor space for irrigation, heating, electrical and other greenhouse related systems. Some structures of been shown below get a clear idea of the discussion.
Adopted from: http://www.marsonearth.org
Adopted from: http://www.science.ksc.nasa.gov
Adopted from: http://www.marsonearth.org
Adopted from: http://www.grcimagenet.grc.nasa.gov
Conclusions
To conclude the story, it is possible to make the greenhouse on Mars. Reductions in atmospheric pressure, light, temperature, water and day length and seasonal variations are the challenges to face in this regard. Maintenance of minimum internal pressure 10 kpa for good plant production, use of solar collectors and hybrid solar wind system for enegry collection and generation, control on evapotranspiration rate useful for greenhouse design and management related decisions, and use of underground structures due to their multiple advantages are the certain remedies of these challenges in the way of making greenhouse on Mars. Further, leafy vegetables, aeroponics, and control on dust and wind problems are the other important considerations.
In the end, I'm confident to claim that this research will open the doors for Plant Physiologists to join astronauts while exploring Mars. But It's still the idea, centuries are needed to see something practical on Mars.............!
Note: It was not possible for me to make the Greenhouse on Mars completely myself. So all above data including text and pictures, was compiled from different sources. I need your feedback to know the strength of my effort, so please comment freely and generously.
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1254141984091#c8660629847824308752'> September 28, 2009 at 5:46 AM
very nice post
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1254323422747#c876858752821874843'> September 30, 2009 at 8:10 AM
thanx...........!
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1255010834054#c5650590134363876921'> October 8, 2009 at 7:07 AM
nice work Saif. It's interesting blog. Well, count me in when you decide to visit Mars. ;)
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1255022699373#c1709766414725881340'> October 8, 2009 at 10:24 AM
Thanx buddy. Sure I will :)
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1255059250326#c3153640078677735550'> October 8, 2009 at 8:34 PM
Mr Saif Great work, me too wana to visit your Green House on mars.
Bas kiraya Mars Ka ap da dana.......hahahaha
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1255527953878#c1099916756699713453'> October 14, 2009 at 6:45 AM
it's cool man..
very inspired...
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1255578640130#c8043588580335624918'> October 14, 2009 at 8:50 PM
Thanx.............!
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1255660802170#c7784244509954099281'> October 15, 2009 at 7:40 PM
really interesting...though I'll have to read it more fully again. My husband has purchased some property on mars (with real earth dollars). I wish I were kidding, but I'm not. I have the papers to prove it. Perhaps when we get there, you can camp on our property and build the greenhouse.
Very interesting post Saif - looks like you and your colleagues did a lot of thinking and made a lot of calculations regarding the liklihood of this. Very cool.
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1255672082154#c8476913859421012132'> October 15, 2009 at 10:48 PM
Wendy, it's really nice to hear your husband has purchased some property on Mars. Very very glad to meet you, a property holder on Mars. How much I'm happy I can't tell. Now at least I can manage some place over there to start my work practically, thanks for the offer. In the end, thank you very very much for visiting my blog, passing your comments so nicely and giving me the chance to know you more closely. Nice day :)
http://hortist.blogspot.com/2009/09/greenhouse-on-mars.html?showComment=1256179165625#c5231916271670506841'> October 21, 2009 at 7:39 PM
You have done such a research as to say that one can even grow a plant in the most remote & difficult climatic atmosphere.
As even to say - if you can plant it in Mars, whats stopping you from planting here. (This is sort of as I understand that those who say gardening is difficult, think about planting in Mars & that is possible)
I would think that having greenhouse in Moon is more realistic than in Mars as the distance and the journey to travel will be more difficult compared to going to the nearest "planet" - moon.
Or that if we can produce a mega spaceship that can sustain a population for life - that would be great.
Just my thoughts - watching too many si-fi movies where they have hydroponics in their greenhouse spaceship & all.