In The Martian, the 2015 science fiction film directed by Ridley Scott, Mark Watney, the astronaut played by Matt Damon, grows potatoes in Martian soil by using the ‘bio-waste’ of him and the rest of the crew who fled when a dust storm struck.
That’s one way of transforming the nutrient-poor, so-called ‘regolith’ of the Red Planet into something in which crops may thrive.
However, it’s probably not an ideal solution. So how do we make soils viable for agriculture if we want to colonise other worlds?
Not only is the soil on Mars (and also the Moon should we ever want to colonise that too) lacking essential nutrients such as nitrogen, phosphorous and potassium, it is also very alkaline and has high concentrations of toxic elements and compounds such as aluminium, manganese and perchlorates.
One solution might be to transport organic matter into space but this is very expensive – in 2019, the cost of delivering cargo to the International Space Station (ISS) was estimated to be US$20,000 a kilogram.
So now researchers are focusing more on how best to make the substandard regoliths suitable for plants to grow in – “optimising in situ resource utilisation”(ISRU), as the terminology goes.
A team of scientists from universities in Brazil and the United States believe they may have found an answer, and it’s fungi, according to a paper published in Frontiers in Astronomy and Space Sciences.
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They point to what are called “arbuscular mycorrhizal fungi”, which in laymen’s terms are fungi that form mutually beneficial, or symbiotic, relationships with plant roots.
The fungi grow inside the root cells and send out fine threads, or hyphae, into the surrounding soil, enabling the plant to obtain more critical nutrients such as phosphorous. The fungi gains by being supplied with sugars the plant makes through photosynthesis.
As the paper says, “In effect, they act as microscopic extensions of the root system, helping plants reach and absorb nutrients more efficiently.”
In terms of removing toxic compounds, the researchers point to ‘extremophile’ bacteria that can tolerate perchlorate-rich desert soils of the northern Tibetan Plateau, suggesting they could play a role in ameliorating them. Fungi in the Penicillium genus can be used to convert perchlorates into chlorides and oxygen.
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Still, much more work is needed. For example, the researchers stress that future studies will need to “test how well these fungi perform with actual lunar and Martian regolith rather than simulations or other substitute materials”, which of course is problematic, because there is limited lunar soil available – and nothing from Mars.
And they will need to be put into controlled environments where they must tolerate stresses such as cosmic radiation and extreme temperatures to see how they respond to these conditions.
Only then will we know if the humble fungus can play a role in enabling humans to conquer new worlds.
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