Coming soon: a market garden on Mars

Don’t grow spinach on Mars. That’s one of the key messages arising from a generally encouraging set of experiments designed to test how well food crops will grow on the Red Planet.

The prospect of establishing a permanent human settlement on Mars might in recent years have shifted from the fanciful to the possible, but uncertainties around ensuring sustainability continue to keep it from becoming probable.

One of the key challenges for any settlers will be producing enough food to become self-sufficient, and the most likely way of doing that – in the absence of easy-to-use molecular gastronomic vending machines – will be growing plants.

How well anything will take root and produce fruit in the iron-rich dirt of Mars, however, has until now been an open question.

In an effort to answer it, researchers at NASA recently used their best geochemical data to produce a simulant of Martian soil – and one of the moon’s, to boot.

Using these artificial soils – known as regoliths in the jargon – researchers led by Wieger Wamelink of Wageningen University in the Netherlands decided to plant plenty of seeds, water them, then sit back and wait for something to happen.

They chose 10 popular food species: garden cress, rocket, tomato, radish, rye, quinoa, spinach, chives, pea and leek. The soils were augmented with organic matter in the form of chopped up pieces of the same plant varieties – working on the not unreasonable assumption that pioneering Martian or lunar market gardeners would be smart enough to dig the unused parts of past crops back into the soil to fertilise the next.

Seeds from each species were planted at random in 10 trays each for the Mars and moon regoliths, and set next to another 10, this time full of Earth soil, which acted as controls.

Surprisingly, the results were good. Most of the moon-soil plants grew quite weakly, but the Martian ones shot up with only slightly less vigour than the Earth controls. {%recommended 7597%}

The exception was spinach, which, Wamelink and colleagues report in the journal Open Agriculture, “started to flower after only a few small leaves were formed” and thus produced nothing of substance.

Some of the other results, however, would have looked lovely in any terrestrial allotment.

“We were able to harvest radishes and radish seeds, cress and cress seeds, rye seeds, rocket, tomatoes and peas on Mars and Moon soil simulants and Earth organic soil,” the researchers write.

The chives and leeks, in contrast, grew rather feebly in the Mars and lunar mixtures, while quinoa grew “well and formed flowers, but did not form any seeds”.

(This possibly means that any future Mars or moon settlements, regardless of what other attractions they might be able to boast, will be quinoa-free, which many will see as a very good reason to go there.)

The researchers report that their experiments produced the first ever fruits grown in NASA’s simulated soils, and credit the success to the quantities of organic matter added to the growing media beforehand.

They urge further research in this area to determine the optimum ratio of rotting old plant to Martian or lunar regolith, noting that the need for large amounts of organic material will make the task of establishing fertile soil much harder.

Science fiction fans may remember the travails of Mark Watney, the lead character in Andy Weir’s novel The Martian, who, when marooned alone on the planet, tried to grow potatoes.

Given appropriate conditions, the work of Wamelink and colleagues suggests that the task might not be so difficult after all – providing that the initial cargo manifest for the journey to the planet includes a big box of compost.

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