Alfalfa May Be the Key to Unlocking Gardens on Mars

If humanity decides one day to expand its reach into the solar system with a colony on Mars, using Martian soil and water to grow food will be one of its top priorities. And while science fiction films like “The Martian,” starring Matt Damon as a stranded scientist, might have you believe that potatoes are the key to unlocking this future, a new study says it’s actually alfalfa that should steal the limelight. 

"The low nutrient content of Martian soil and high salinity of water render them unfit for direct use for propagating food crops on Mars," write the researchers in their published paper in the journal PLOS ONE. "It is therefore essential to develop strategies to enhance nutrient content in Mars soil and to desalinate briny water for long-term missions."

Martian soil is very similar to iron-rich, basalt-type, volcanic soils on Earth, minus organic matter and with only a small percentage of air and water (2% vs. Earth’s 50%). To discover what might grow best in such conditions, researchers used an approximation of Martian soil with finely ground basaltic rocks. Seeds of turnips, lettuces, radishes, and alfalfa—all plants that do not require much maintenance or water to grow—were then planted. 

In addition to germinating the young seedlings under grow lights, the research team watered them with their own version of artificial Martian water. While Mars appears a dusty wasteland today, much of it was once covered in ocean. According to some estimates, as much as 30%-99% of it may still be locked away frozen in ice at the poles or deep in underground salty reservoirs. 

To reduce the salt content of any water harvested on Mars, the research team first introduced a marine bacteria, Synechococcus, well-known for its ability to desalinate high salinity water. The briny output was then filtered multiple times through a bed of basalt-type volcanic rocks to produce the fresh water needed for the plants to grow. 

Growing a Martian Garden

In the first stage of the experiment, alfalfa was the only plant able to grow nearly as healthy as the control group planted in garden soil. By contrast, turnips plants were stunted and less healthy than their control group counterpart. Once the researchers ground up the alfalfa crop and applied it to the Martian soil, the incorporated nutrients and organic matter allowed other plants to flourish. 

“Growth of turnip plants increased to 190% in alfalfa treated simulant soil,” the researchers write. “Turnips plants produced healthy bulbs in alfalfa-treated simulant soil. Biomass of radish bulbs (311%) and lettuce leaves (79%) was significantly improved as compared to that when grown in untreated simulant soil.”

For those involved in farming here on Earth, hearing the news that alfalfa might be good for improving the soil of Mars likely isn’t surprising. The plant is a commonly grown cover crop renowned for its high nitrogen content and minerals such as phosphorus, potassium, calcium, sulfur, magnesium, boron, iron, and zinc. It’s not a reach to one day imagine Martian farmers either deep underground or in specially designed habitats sowing fields of alfalfa to lay the foundation for future corn, wheat, or other life-sustaining crops.

As for the research team, they disclose that there is still much to do before such visions can one day become a reality. For one, their artificial Mars soil isn’t an exact match for the real thing. Unlike volcanic rock on Earth, Martian soil contains a high amount of toxic perchlorate salts. Adding perchlorates to the simulant soil and then reducing or eliminating it, either by beneficial bacteria or filtration, may be the subject of future experiments. Nonetheless, they conclude that alfalfa offers a promising addition to our interplanetary exploration ambitions.

“This study signifies that for long-term purposes,” they write, “it is possible to treat in situ soil and water resources for farming on Mars to sustain human missions and permanent settlements.”