Several groups including NASA, Elon Musk and Mars-One hope to take people to Mars in the next ten to fifteen years. Returning to the Moon may happen in the next five years. If we get there it will be to stay for extended periods. People will also have to eat there and what is more logical than to grow your own food locally? In 2013 and 2015 we conducted two experiments to investigate whether it was possible to cultivate peas, radishes and tomatoes on Mars and moon soil simulant supplied by NASA. The 2015 experiment provided the first radishes, peas, tomatoes and rye, but 
it is also safe to eat them?

Why?

The Mars and lunar soils contain several heavy metals that are toxic to humans such as lead, cadmium and arsenic. Plants are not too bothered by these and just carry on growing. We don’t know if the harvested fruits contain heavy metals and we don’t know if it is safe to eat them – which is what we aim to address in this project. If the project is successful, and shows that it is indeed safe to eat the plants and fruits, it brings the journey and the establishment of a long term human presence on Mars and a more or less permanent base on the moon one step closer.

 How?
The experiment will be carried out according to a procedure developed in 2015, with some improvements. It will use experimental trays, with one crop per tray, containing respectively peas, tomatoes and radishes and two other crops. The experiment will be replicated five times and the soils (Mars and lunar simulants and terrestrial control) will be enriched with organic material in order to improve the structure and nutrient supply. For Mars the nutrient will consist of the parts of the plants that would not be eaten and human faeces. Fruits and edible parts will be harvested and analysed for heavy metals at the Wageningen UR institute Rikilt.

Spin-off for the Earth
Whilst the survey is conducted for Mars and lunar soil simulant, it will also provide an insight into the uptake of heavy metals by plants in general and is therefore applicable to the situation on earth. In this context we can think about the potential use of plants to clean up metal contaminated soils or even the collection of rare metals by using plants.

This project is part of a larger effort to conduct more research into the cultivation of crops on Mars and the moon. However, in the long term, this could also result in the development of closed systems which may also be applied in earth conditions such as in deserts where similar problems apply. This research can contribute to growing crops, for example in containers, in places where it is currently not possible or in places where there has been a disaster and food is urgently required to be grown. It also investigates how the agricultural ecosystem could function on Mars and the moon. This also provides important insights about farming systems on Earth and the interaction between crop, soil, soil and pollinators, which are all necessary for a successful crop and not only on the moon or Mars. In 2016 the experiment will be extended with Sahara sand to investigate possible plant growth on it.

Previous research
In 2013 the first study was conducted with fourteen different plant species in Mars and lunar soil simulant and terrestrial river sand. The plant species were wild plant species, shamrocks and a number of agricultural crops, including rye and tomato. In total, 840 jars were filled with sand with five seeds per pot. It soon turned out that the plants grew well in the simulant Martian soil, but on the lunar soil many plants died soon after germination. This was mainly due to a lack of moisture and the toxic effect of aluminium. In the second experiment, we used large containers (instead of jars) and grass to provide ‘green’ manure. As a result the plants grew well on both the simulant Mars and lunar soils and rucola, cress, radish, pea, rye and tomato could all be harvested. The big question now is can we safely eat these plants?