How Will Farming on Mars Work?

In the popular science fiction film The Martian, astronaut Mark Watney (Matt Damon) is stranded on Mars and survives by planting and farming potatoes in the planet’s soil. 

When humans of the future go to Mars, they may be able to grow crops in the soil, just like Watney did in the film. However, new lab experiments seem to show that growing food on the red planet will be much more difficult than putting seeds in the ground and watering them. 

Researchers studying the possibility of harvesting crops on Mars planted lettuce and a type of weed in three different kinds of “Mars dirt”. Two of the soils were made of organic substances that looked similar to the surface on Mars, and the other was made using volcanic rock, salt, and clay that had actually been observed on Mars by NASA’s Curiosity rover. 

While the lettuce and the weeds survived and grew in the two natural soils, they couldn’t grow in the third soil. 

Planetary scientist Kevin Cannon, who wasn’t even involved in the study explains, “It’s not surprising at all that as you get [dirt] that’s more and more accurate, closer to Mars, that it gets harder and harder for plants to grow in it”. 

The soil found on Earth is full of organic matter that helps plants grow, while the soil on Mars is just ground up rock. The study reaffirms that, “if you want to grow plants on Mars using soil, you’re going to have to put in a lot of work to transform that material into something that plants can grow in,” Cannon says. 

In the experiment, lettuce grew in the two types of soil made of natural substances, as long as the soil was fertilized.

Even when the researchers grew the lettuce and weeds in “normal” Earth soil and then transferred them to the third, “mars-like” soil, the plants died within a week.

Biochemist Andrew Palmer, who was on the research team that explored the plants growing in Mars-like soil, suspected that the plants’ inability to grow was due to the soil’s high pH level. The first two, natural soils had pH levels around 7, while the third soil had a pH of 9.5. 

After their initial testing, Palmer’s research team came across another issue: calcium perchlorate, a toxic salt that makes up 2% of Mars’ surface, wasn’t in the team’s original soil recipes. When the team added it to their soils, neither the lettuce or the weeds grew at all. 

Edward Guinan, an astrobiologist at Villanova University, also not involved in the study, says “The perchlorate is a major issue. There are bacteria on Earth that use perchlorates as a food”. The bacteria eat the toxic salt, and give off oxygen. If the bacteria were taken to Mars, Guinan thinks that they not only would remove the toxic salts, but might even supply oxygen for astronauts to breathe. 

What’s more, the exact treatment required to make Martian dirt farmable may vary, depending on where astronauts make their homestead. “It probably depends where you land, what the geology and chemistry of the soil is going to be,” Guinan says.

To explore how that variety might affect future agricultural practices, geochemist Laura Fackrell of the University of Georgia in Athens and colleagues mixed up five new types of faux Mars dirt. The recipes for these fake Martian materials, also reported in the Jan. 15 Icarus, are based on observations of Mars’ surface from the Curiosity, Spirit and Opportunity rovers, as well as NASA’s Mars Global Surveyor spacecraft and Mars Reconnaissance Orbiter.

Each new artificial Mars dirt represents a mix of materials that could be found or made on the Red Planet. One is designed to represent the average composition across Mars, similar to the synthetic material created by Cannon’s team. The other four varieties have slightly different makeups, such as dirt that is particularly rich in carbonates or sulfates. This collection “expands the palette of what we have available” as test-beds for agricultural experiments, Fackrell says.

She’s now using her stock to run preliminary plant growth experiments. So far, a legume called moth bean, which has similar nutritional content to a soybean but is more drought resistant, has grown the best. “But they’re not necessarily super healthy,” Fackrell says. Future experiments could explore what nutrient cocktails help plants survive in the various fake Martian terrains. But this much is clear, Fackrell says: “It’s not quite as easy as it looks in The Martian.”

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