January 10, 2022
It may not be as easy as the movies make it out to be.
Future Mars astronauts could someday grow crops in dirt to avoid solely relying on resupply missions, and to grow a greater amount and variety of food than with hydroponics alone. But new lab experiments suggest that growing food on the Mars will be a lot more complicated than simply planting crops with poop.
Researchers have planted lettuce and the weed Arabidopsis thaliana in three kinds of simulated Mars dirt to test this concept. Two of the dirt types tested were made from materials mined in Hawaii or the Mojave Desert that look like dirt on Mars. To mimic the makeup of the Martian surface even more closely, the third was made from scratch using volcanic rock, clays, salts and other chemical ingredients that NASA’s Curiosity rover has seen on Mars.
While both lettuce and A. thaliana survived in the Marslike natural soils, neither could grow in the synthetic dirt, researchers report in the upcoming Jan. 15 Icarus.
"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,” says planetary scientist Kevin Cannon of the Colorado School of Mines in Golden, Colo., who helped make the synthetic Mars dirt but wasn’t involved in the new study.
Soil on Earth is full of microbes and other organic matter that helps plants grow, but Mars dirt is basically crushed rock. The new result “tells you 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.
Seeds of both species germinated and grew in dirt mined from Hawaii or the Mojave Desert, as long as the plants were fertilized with a cocktail of nitrogen, potassium, calcium and other nutrients. No seeds of either species could germinate in the synthetic dirt, so “we would grow up plants under hydroponic-like conditions, and then we would transfer them” to the artificial dirt, Palmer says. But even when given fertilizer, those seedlings died within a week of transplanting.
What’s more, the exact treatment required to make Martian dirt farmable may vary, depending on where astronauts make their homestead. 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. 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.
So far, a legume called moth bean, which has similar nutritional content to a soybean but is more drought resistant, has grown the best. 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.”
A. Eichler et al. Challenging the agricultural viability of martian regolith simulants. Icarus. Vol. 354, January 15, 2021. doi: 10.1016/j.icarus.2020.114022.
L.E. Fackrell et al. Development of martian regolith and bedrock simulants: Potential and limitations of martian regolith as an in-situ resource. Icarus. Vol. 354, January 15, 2021. doi: 10.1016/j.icarus.2020.114055.