Table of Contents
Walkinshaw, C.H. and S.G. Galliano. 1990. New crops for space bases. p.
532-535. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber
Press, Portland, OR.
New Crops for Space Bases
C.H. Walkinshaw and S.G. Galliano
- BIOLOGICAL STUDIES
- PROBLEMS IN SPACE HORTICULTURE
- Choice of Crop
- Soil Packing
- Reduced Geomagnetic Field
- Space Greenhouses
- THE FUTURE
- Table 1
- Fig. 1
Since the Apollo flights of the early seventies, interest in growing plants in
space has increased because of the emphasis on long missions. During the past
18 years, the results of Apollo investigations and of horticultural research,
have strengthened the possibility of eventually growing crops inside space
bases. This presents two overall challenges: growing plants for food in an
international space base and adapting terrestrial plants to unique conditions
in space bases for the development of an independent food supply
This paper examines previous research in space-plant studies, particularly the
Apollo botanical studies and other selected experiments in simulated space
environments. Variables that might regulate plant growth in lunar and Mars
bases are outlined. We conclude that establishing crops in space bases is
feasible as an international effort.
Biological studies from Apollo 11 and 12 indicated that lunar material could
provide mineral nutrients for germinating seeds, liverworts, and plant tissue
cultures (Walkinshaw et al. 1970). The variation in composition of Apollo 11
through 15 lunar materials used in botanical studies was described by Johnson
et al. (1972). Seeds germinated in Apollo 14 lunar material accumulated large
quantities of iron, titanium, and other minerals (Walkinshaw and Johnson 1971).
Gamma spectrometry and autoradiography revealed that lettuce seedlings exposed
to neutron-activated Apollo 11 and 14 lunar fines absorbed scandium, cobalt,
manganese, and a variety of elements that included rare earth elements (Baur et
Apollo 16 investigations showed that cabbage seedlings grown in contact with
lunar material accumulated high concentrations of aluminum. To prevent this,
excess aluminum could be removed by leaching lunar soil with slightly acidic
hygienic waste water from lunar base activities as simulated by others (Johnson
et al. 1972, Stumm and Furrer 1987).
Apollo lunar samples successfully stimulated growth of small, germ-free plants
such as Bryophyllum, Lycopodium, and liverworts. Lunar samples
similarly stimulated germination and growth of the sensitive fern Onoclea
sensibilis L. All stages of the fern, the germinating spore, gametophyte,
and the sporophyte exhibited increased greening and growth in response to
Apollo 11, 12, and 14 lunar materials.
Light microscope examinations of callus cultures sprinkled with lunar fines
demonstrated normal cell morphology for carrot, Haplopappus, longleaf
pine, maize, soybean, spurge, and sugar pine. Lunar particles were observed
adjacent to densely staining and actively dividing tissue culture cells.
Biochemical analyses verified the accelerated development of chloroplasts in
tobacco tissue cultures treated with Apollo 11, 12, 14 and 15 lunar samples.
When compared with untreated issues, treated cultures contained 21 to 35% more
total pigment of chlorophyll. A variety of other plants and tissue cultures as
described by Walkinshaw et al. (1970) underwent increased greening in response
to lunar material. An increase in chlorophyll was demonstrated for tobacco
(Weete and Walkinshaw 1972).
The main component of the Apollo 11, 12, and 14 samples, lunar mare basalt
stimulated growth according to the ability of plants to absorb elements from
the basalt and incorporate them. Because of the reduced state of lunar basalt,
it appears to be a good source of certain essential elements for crop plants.
Growing plants in space bases presents unique problems. Because of the absence
of wind and insects, crops whose flowers require assistance for pollination
will have development problems. Therefore, short-season, bisexual
self-pollinated plants such as broccoli and garden peas which have a low rate
of outcrossing, would be ideal candidates for a totally automatic space
greenhouse. Plants such as cucumber and squash, which require special
pollination, would need mechanical assistance or a modified sonic or vibration
system. Tomatoes also may need pollinating assistance.
Refinement of cultivation of Brassicas in small areas by P.H. Williams at the
University of Wisconsin makes it an ideal plant system to be considered in an
initial space base (Williams and Hill 1986). These species could produce
useful building materials and edible plant parts. Because seeds mature rapidly
and do not exhibit dormancy, seed sowing to flower production would require
only 14 days. Many of the plants in this genus are small, are a component of
our terrestrial diet and complete many cycles per year. Female fertility is
high, and nuclei are receptive to introduced genes that may be useful in space
Some studies of terrestrial and lunar basalts suggest that the fine lunar
particles are so small they would compact into a clay-like mass when watered,
and minimize root aeration. To reduce packing, the fine particles could be
mixed with particles the size of sand grains. Composting lunar fines with
waste products from the base also could reduce packing.
We have subjected plants at 34 kPa (256 mm Hg) pressure to a sudden change to
101 kPa (760 mm Hg). Pressure changes neither hindered seed production nor
caused the plants to wilt (Walkinshaw 1986). Throughout the experiment reduced
pressure and the gaseous environment had little effect on seed germination,
growth, or plant morphology.
In chambers at the National Aeronautics Space Administration facilities in
Houston, we tested crop plants for their ability to germinate and grow in low
atmospheric pressure and altered gas composition. These tests revealed that
edible plants tolerate low levels of oxygen and carbon dioxide, and deletion of
nitrogen during germination and growth (Table 1). Substituting helium for
nitrogen did not affect seed germination or growth and at low pressures (11 to
13 kPa, 80 to 100 mm Hg), oxygen and water vapor were sufficient for
germination of certain crop plants.
The protein content of soybeans grown under 33, 67, and 101 kPa pressures did
not differ in the total micrograms of protein (221, 198, and 224, respectively)
Another environmental extreme tolerated by edible plants was reduced
geomagnetic field. Tests in a Mu-metal room with geomagnetic forces reduced
from the terrestrial value of 55,000 to 75-140 gammas showed germination,
seedling growth, and tissue cultures to be unaffected. Chlorophyll a, b, and
carotenoids of 2-, 3-, and 4-week-old lettuce seedlings were not different in
the low and normal terrestrial magnetic field. Held for 20 or 30 days in the
reduced magnetic field, lettuce tissue cultures exhibited a 40% decrease in
overall respiration. The low geomagnetic field did not affect root and stem
lengths of germinating Brussels sprouts, cabbage, lettuce, and radish; nor did
the altered environment affect soybean respiration or their fresh and dry
If plants are unable to withstand aspects of a space environment that cannot be
readily changed, we must house them economically to keep them from extremes of
temperature and to provide moisture. Usually, artists depict a lunar or Mars
greenhouse as a rigid dome of metal and plastic. This design does not
recognize the serious problems associated with proton and high-Z-particles
(energetic particles with atomic numbers from 8 to 26) that penetrate several
meters of soil. Neither does the design compensate for the safety problem of
lunar or Mars extremes in surface temperatures.
Locating greenhouses in caverns created and fined with bags of lunar fines
could perhaps minimize environmental effects (Fig. 1). These plastic bags that
contain surface materials would screen high-Z-particles and protons. Thickness
of this shield should be several meters to absorb these damaging high energy
particles. Storing fresh or waste water on top and at the entry of the
greenhouse should help absorb particles and shield plants from any
On the moon and Mars, direct lighting would necessitate major cooling which
translates into a need for energy. Direct lighting would also subject plants
to high-Z-particles and protons that can kill both dividing and resting
For a Mars or lunar base, we suggest using mirrors to reflect sunlight into the
greenhouse. The reflected sunlight could be supplemented with strobe lighting
(Cathey and Campbell 1977). Strobe lighting would reduce energy required for
cooling and may result in increased crop yields. Nuclear, chemical or thermal
generators could provide energy for the strobes. In a lunar base, a
geostationary solar reflector would reduce the problem of the 14-day/night
It is not feasible for the United States alone to build extraterrestrial
greenhouses. Since 1975, the USSR has included on-board plants in its space
missions. Their ground chamber simulations of 1-year duration have paralleled
the flight experiments. In their spaceships, the Soviets have grown cabbage,
lettuce, oats, peas, radish, wheat, and onions (Milov and Rusakova 1980). An
oazis (growing bed) has been flown on every flight since 1975. Soviet
literature on space research is rich in details of aerospace horticulture
(Gazenko 1983, Mashinskiy and Nechitaylo 1983).
Because of the Soviet Union's extensive experience as principal investigators
in space plant research, the Soviets qualify as leaders of any cooperative
venture to colonize the Moon or Mars. A cooperative effort between the USSR
and the United States seems to be the logical and most beneficial way to face
the advantages and challenges offered by growing plants for food on the moon or
The likely progression of space bases will be lunar, Mars, and then to other
moons in the solar system. These developments should be initiated before 2030.
The driving force for the establishment of a lunar base should be the testing
of components for a Mars space base. Plant systems would be on the list of the
vital space base components to be tested.
- Baur, P.S., R.S. Clark, C.H. Walkinshaw, and V.E. Scholes. 1974. Uptake and
translocation of elements from Apollo 11 lunar material by lettuce seedlings.
- Cathey, H.M. and L.E. Campbell. 1977. Light frequency and color aid plant
growth regulation. Amer. Nurseryman 145:16-114.
- Gazenko, O.G. 1983. Space biology and medicine: yesterday and today Zemlia i
- Johnson, P.H., C.H. Walkinshaw, J.R. Martin, W.B. Nance, A.D. Bennett, and E.P.
Carranza. 1972. Elemental analysis of Apollo 15 surface fines used in
biological studies in the Lunar Receiving Laboratory. BioScience 22:96-99.
- Mashinskiy, A., and G. Nechitaylo. 1983. Birth of space agriculture. Tek
- Milov, M. and G. Rusakova. 1980. Greenhouses in space-higher plants in closed
ecological systems. Aviatsia Ei Cosmonautika 3:36-37.
- Stumm, W., and G. Furrer. 1987. The dissolution of oxides and aluminum
silicates, examples of surface coordination-controlled kinetics, p. 197-219.
In: W. Stumm (ed.). Aquatic surface chemistry. Wiley, New York.
- Walkinshaw, C.H. 1986. Space greenhouses could operate efficiently at low
pressures if fungi are controlled. Phytopathology 76:1141.
- Walkinshaw, C.H., and P.H. Johnson. 1971. Analysis of vegetable seedlings grown
in contact with Apollo 14 lunar surface fines. HortScience 6:532-535.
- Walkinshaw, C.H., H.C. Sweet, S. Venketeswaran, and W.H. Home. 1970. Results of
Apollo 11 and 12 quarantine studies on plants. BioScience 20:1297-1302.
- Weete, J.D., and C.H. Walkinshaw. 1972. Apollo 12 lunar material: effects on
plant pigments. Canad. J. Bot. 50:101-104.
- Williams, P.H., and C.B. Hill. 1986. Rapid-cycling populations of
Brassica. Science 232:1385-1389.
Table 1. Effect of pressure on germination and growth of crop plants
after seven days in air or air containing 10% carbon dioxide (+) with 12-hour
z105, 105+, and 760 mm Hg, respectively.
|Crop ||Pressurez (kPa) ||Germination (%) ||Stem length (cm)|
|Bean ||14 ||75 ||8|
| ||14+ ||71 ||19|
| ||101 ||83 ||10|
|Cotton ||14 ||90 ||7|
| ||14+ ||100 ||8|
| ||101 ||100 ||9|
|Lettuce ||14 ||100 ||2|
| ||14+ ||100 ||4|
| ||101 ||100 ||3|
|Maize ||14 ||100 ||15|
| ||14+ ||100 ||31|
| ||101 ||100 ||30|
|Sorghum ||14 ||71 ||10|
| ||14+ ||80 ||16|
| ||101 ||69 ||13|
|Wheat ||14 ||90 ||13|
| ||14+ ||100 ||23|
| ||101 ||100 ||18|
Fig. 1. Lunar greenhouse recessed in a cavern and lined with surface
materials to reduce temperature fluctuations and lethal radiation.
Last update September 5, 1997