Vegetable garden on Mars does better when it is a bit messy

Do you (also) dream of a life on Mars? Then prepare yourself well to work hard; food from the earth will not come. Your future vegetable garden will therefore become essential. Recent research now shows that it can be a bit messy.

To be clear: you are not supposed to randomly put plants in the ground. Instead, it is much more about finding the right balance, where cooperation between different plants will be central. This is evident from a new study published in the journal PLoS ONE. For this research, the scientists grew tomatoes, peas and carrots in different types of soil. This shows that – with the right combination of different factors – plants can do a lot better if they are a little mixed up. Scientist Wieger Wamelink contributed to the research. He tells “We were surprised to see how well the tomatoes did in the end. At the same time we noticed that the roots were lagging behind. This is probably because the peas and tomatoes grew very large – thus taking the light away from the roots. For subsequent experiments, we want to look for a more balanced species composition.”

As stated earlier; Setting up a vegetable garden on Mars is a lot more difficult than you might think. That starts with the soil itself. For example, the research shows that even sand would be more suitable for growing crops than regolith from Mars. Wamelink explains: “Mars regolith is very nutrient poor; nitrogen in the form of nitrate or ammonium is almost completely absent. This is the reason to use bacteria. However, they do need phosphate, which is unfortunately only available to a limited extent.” For the research, the scientists tested three different soil types: sand, a simulant that imitates Martian regolith and normal potting soil. They then enriched these different soil types with the bacteria Rhizobium leguminosarum. This bacterium therefore had the important task of giving the plants a helping hand. They did this by entering into a symbiotic relationship with the pea. Wamelink says: “The peas were chosen because they live together with the rhizobium bacteria. The bacteria extract nitrogen from the air, which is then converted into ammonium. This process often leaks ammonium, which the other plants can benefit from.”

The other vegetables chosen also had a good reason for being present. Wamelink continues: “Tomatoes and peas like to grow together, so the peas can hitch a ride with the tomatoes, as it were. The roots were mainly chosen because they grow underground. In theory, they should be able to benefit additionally from the leaking ammonium.” Although the experiment was so beautifully conceived, it certainly had its difficulties: “The tomatoes formed large, sturdy plants,” Wamelink sighs. “That wasn’t the intention, but it happened anyway. This took so much light away from the other species that they began to compete.”

In addition, it turned out that the bacteria did not always have an easy time: it was possible in Mars regolith R. leguminosarum hardly expressed, while it did so well in sand that all plants benefited from it. Wamelink thinks he knows why this is the case: “The moment of adding the bacteria is very important, as is the moisture balance. I therefore think that both factors could have been better. For example, adding (the bacteria, ed.) during a previous study with green beans worked well – also in combination with Mars regolith.”

The results of the research are significant, because they show that setting up a vegetable garden on Mars is really not that easy. Nevertheless, during this research the scientists also discovered that the combination of tomatoes and peas seems to work very well. Wamelink says: “In the future we want to continue our research, continuing to test which varieties fit well together. We therefore look at other crops – and potatoes in particular. This vegetable grows quickly, requires little space and has a large yield. This is ideal for space.”

Unfortunately, there is one last, important threat to the future vegetable garden on Mars: perchlorate – a salt that is common in the Martian soil. Wamelink says: “Perchlorate is a really serious problem. Not only for plants, but also for people and equipment.” However, the scientist also hopes to have found a solution for perchlorate: “An experiment is now underway (to combat perchlorate, ed.), and I have already done a kind of pilot experiment myself. The idea here was that, because salt-loving plants can tolerate salts well, they can hopefully also filter perchlorate from the soil. In any case, this is already possible with samphire, and to a lesser extent even with quinoa.”

What will the future vegetable garden on Mars ultimately look like? Wamelink concludes: “On Mars you definitely need a greenhouse. Absolutely not allowed outside; it is too cold there, there is no liquid water, the air pressure is much too low and the cosmic radiation is too intense. In the greenhouse itself you want to make as much use as possible of what Mars has to offer. These are the regolith, water and building blocks. In the greenhouse you will encounter many different forms of cultivation: open ground cultivation, algae cultivation, worm cultivation and also hydroponics. In addition, there must of course be pollinators and mealworms to serve as a protein source. We can now grow more than 25 different types of vegetables in this way on the simulant that simulates Martian regolith. My personal opinion is that it could be possible to send the first mission in the early 2030s. Then you would also descend to Mars. It is quite possible that we first go there and back alone without descending. Just like what happened with the moon at the time.”

So some patience is still appropriate. But if you ever end up working in such a future Mars greenhouse; it’s okay if you’re a little messy.