Travelling in space and to the moon and Mars; it may be science fiction for some, but for plant physiologist Tom Dueck, professor Leo Marcelis and Sander van Delden from Horticulture and Plant Physiology, and ecologist Wieger Wamelink, all from Wageningen UR, it is actual science. They are working in various projects focused on growing plants in other places than on earth.
Several weeks ago astronauts at the International Space Station (ISS) enjoyed their first ever space salad. Nonetheless, a lot of research is still required to enable a healthy diet on the way to Mars and on the planet itself. Tom Dueck: “We have selected the plant varieties that we would like to grow in a spaceship and are now ready to take the next step: testing cultivation systems in a mobile test laboratory near the Neumayer III station on Antarctica.”
Leo Marcelis and Sander van Delden started with the setup of a cultivation system for fundamental plant research on the ISS. The system enables plants to be grown either without gravity or with the gravitational conditions found on the moon, Mars and on earth. “It’s a huge challenge,” according to Marcelis: “First we had to test a lot of aspects on earth before anything could be sent to the ISS.” The hardest thing may be that it has to be a closed system as not a drop of water from the cultivation system can be allowed to enter the space station. Recycling water and nutrients is a major goal for the scientists.
The research will probably also result in insights that can be applied on earth. For example, the Wageningen scientists are looking for efficient and reliable ways to provide the plant with the correct ratio of water and nutrients in extreme conditions. Part of this search is selecting the right substrate in which the roots can grow. This is not easy as materials can behave very differently in space than on earth. “Maybe we can do without substrate, for instance by growing on water mist,” says Leo Marcelis. “If we succeed we can hopefully provide the residents of the ISS with fresh food permanently and develop an approach in which growing food becomes a permanent part of the advanced recycling system required in space.”
Growing plants on Mars
Wieger Wamelink has been working on cultivating plants on soil composed by NASA that resembles the actual soil on Mars and the moon as closely as possible. The first experiment has had encouraging results, mainly on the ‘Martian soil’. Various edible plant varieties such as garden cress and wild radish, germinated and grew. Some varieties even blossomed and set seeds on the Martian soil, but most of the germinated seeds failed to survive on the ‘moon soil’, possibly due to the high pH levels and dehydration sensitivity of the soil and the toxicity of the aluminium in the soil.
New research in which organic material was blended in with the soil as green fertiliser has much better results. On both soils it became possible to produce edible leaves, tubers, seeds and fruit from rye, radish, peas, garden cress, spinach and cherry tomatoes. Wamelink: “The space tomatoes were a great surprise, but it was even more important that we saw seed formation which would allow us to plant and breed the next generation of plants.”
The most important finding is that a greenhouse on Mars would require other living organisms besides plants, such as worms and bacteria for the breakdown of organic material and nitrogen fixation in the air. This would mean bringing an entire ecosystem because, as far as we know, there is no life on Mars. Wamelink also assumes that we would build a greenhouse underground with an atmosphere that bears a greater resemblance to the one on earth. “On Mars there are high levels of galactic cosmic ray radiation and almost no air.”
Growing crops in a spaceship
Should our astronauts be performing research on board the ISS for longer periods, or if they would later make a longer trip to Mars, fresh food will be required. The main things heard from the ISS are “a crispy salad, a fresh tomato or a sweet strawberry.” This is what they would like, but can we deliver? Dueck has made a selection of crops that can be grown in a closed system, are in line with the limited space available on board the ISS, and meet the requirements for the wellbeing of the astronauts. “Due to the lack of gravity, people have less sense of taste in space. For this reason some crops should be spicy, some should have a good bite and others should have a delicious flavour.”
Optimising space conditions
Dueck will now be determining the right cultivation systems and conditions with his colleagues, including issues such as the optimal temperature, moisture and CO2 conditions for cultivation and which colours of light would work best. Another aspect that will be looked into is how long it will take from the time of sowing before an astronaut can harvest and consume the first leaves, fruit, tubers or seeds, and when and how often the sowing should take place to provide a relatively continuous food supply.
The system will be built in the coming year. To properly test it for use on the ISS or on the way to Mars, a mobile test laboratory will be constructed and installed near the Neumayer III station on Antarctica where a small group of scientists will be living and working for a period of one year.