In 2019, a plant began to grow for the first time on the Moon. For a few hours, an outbreak arose from a cottonseed sent by China in a miniature biosphere next to other vegetable seeds and fruit fly eggs in the Chang'e 4 probe. The ephemeral life of the plant will not offer much information on plant development in the conditions of lunar gravity, but it is one more step to make possible the next stage of space exploration after the withdrawal of the International Space Station (ISS). A future colony on the Moon, which China already poses for the 2030s, will need its own food.
Since in 1982 the Russian cosmonauts managed to grow a plant of Arabidopsis thaliana, a type of grass, aboard the space station Salyut 7, technologies to grow vegetables in space have continued to progress. In the summer of 2015, American astronauts first ate lettuce grown on board the ISS for the first time. Russian cosmonauts have been consuming part of their harvest since 2003.
To take the next step, several research groups around the world are carrying out projects to recreate the Martian or Moon terrain and to define and solve the problems that the astronaut farmers will encounter. Wieger Wamelink, a researcher at the University of Wageningen (Netherlands), is one of these researchers. "On the one hand, hydroponics could be done in underground infrastructure. I think we could do that if we had the necessary resources and it would not be too difficult, "explains Wamelink. However, this system, which would not need a soil and would provide the plants with their nutrients dissolved in water, requires a greater amount of energy and would not allow the cultivation of staple foods such as potatoes. Both techniques should be combined. "The potatoes give much better performance than, for example, rice, are very important," says Wamelink.
The cultivation in the lunar soil requires an adaptation. For now, in simulated moon soils "we have achieved a crop equivalent to 50% of what we get on land," he says. "I think one of the problems is the amount of aluminum in the soil of the Moon, which is toxic to plants," he adds. One of the ways to improve this problem would be to add organic matter that could be obtained from the feces of the astronauts and from the remains of the plants that were not eaten.
Another difficulty to grow vegetables on the Moon is that their soil is very rough. On Earth, water or wind wear the particles and make them more rounded, but on the Moon there are no such phenomena and being sharper cause leakage in the roots of plants, which grow worse. In addition, both on the Moon and on Mars, future settlers will miss nitrogen in the soil. "On Mars or the Moon, the soil has almost all the nutrients plants need, but it has hardly any nitrogen," says Wamelink. On Earth, this element comes from organic matter that on the Moon should be incorporated, among other things, recycling the feces and urine of astronauts, which, especially at the beginning, would be the main source of nitrogen. "Once we had nitrogen in the system, it would be to recycle it," he says.
Along with the astronauts, in the colonization trips should also travel other animals that collaborate in the crop. In addition to the bacteria to produce nitrogen usable by the plants, it would be necessary a quantity of earthworms of different species to begin to process the organic matter and create with it a fertile soil. "We would also need insects, bumblebees, to fertilize the plants," says Wamelink. "Bees can do it, but in greenhouses we have seen that they do homework and die. The bumblebees survive and reproduce and also, for a half-year trip like the one on Mars, we can keep them in a state of hibernation and then awaken them, "he concludes.
Before arriving astronauts, Bernard Foing, director of the Working Group for Lunar Exploration of the European Space Agency in Noordwijk (Netherlands), considers that other robotic experiments will be necessary to apply the lessons learned in the laboratories of the Earth on the ground. . "China, India and Israel are some of the countries that have planned missions to the Moon in the near future and could incorporate experiments that go beyond those that Chang'e 4 has tried," says Foing.
One of the problems of the Chinese probe is that the arrival of the lunar night, which lasts more than twelve Earth days and lowers the temperature of -150 degrees, ended with all living beings in the experiment. "At the pole, there are places where in summer there is light all the time and in winter 80% of the time," says Foing. "There you could do experiments that followed organisms within a minibiosphere for several generations," he continues. "So we could learn which plants develop best on the Moon," he says.
One of the fundamental elements for growing food on the moon is water, which can be found in significant quantities, particularly in some regions. Ice would be a resource that can also make a lunar colony sustainable, not just to water the plants. "It would have a lot of value to make rocket fuel and could serve to supply a fuel distribution station in Earth orbit that would be useful for prolonging the period of operation of satellites. This would have a lot of economic value and could help make a base sustainable, "he says.
Waiting for new probes to reach the moon, at this time, the satellite EuCROPIS, which was launched into space at the end of last year, is testing the effects of growing tomatoes under the conditions of gravity of the moon using human urine as fertilizer. This type of experiments will be increasingly frequent if, as it seems, the space powers begin to seriously consider installing a permanent base on our satellite.