It’ll take a lot of work in order to grow rice on Mars. First, and most importantly, we need a mission to successfully get to Mars and set up camp, something NASA is hoping to do in the late 2030s or early 2040s. The distance to Mars from Earth is about 300 million miles (or roughly 500 days aboard a shuttle), so once those astronauts land, they’ll need to cultivate their own food. There’s no ordering a pizza for those guys.
Germinating seeds and growing food on the red planet is difficult, particularly when it comes to Martian soil. The soil on Mars contains a high level of perchlorate salts, which are toxic for plants.
To simulate Martian perchlorate levels, a team of researchers from the University of Arkansas gathered soil from the Mojave Desert, where the desert earth is similar to that on Mars. The area was developed by NASA and its Jet Propulsion Laboratory in 2007 as the Mojave Mars simulant (MMS). Researchers mainly use the area for soil sampling, but they’ve also test-driven rovers and practiced using sampling equipment in icy conditions.
The research team grew three varieties of rice, including one strain of wild rice and two strains with gene-edited lines. The goal was to produce rice better suited to drought, salty conditions and a lack of natural sugars. All three rice strains were grown in three mediums: soil from the MMS, a regular potting soil mixture and a combination of the two. The plants were able to grow in the all-MMS soil, but they didn’t thrive. Instead, the combined potting mixture provided the best results. Researchers found that a 75-percent MMS soil to 25-percent potting soil mixture created improved plants. They also discovered that plants could still take root with one gram of perchlorate per kilogram of soil, but three grams per kg was the upper limit—past that, nothing would grow.
The team presented its findings at the 54th Lunar and Planetary Science Conference last month. Its next steps will be to experiment with other Martian soil simulants and other rice varieties that tolerate high salt concentrations. The team will also work to determine how much perchlorate can leach into the plant from the soil.
It’s not just potential Martian settlers that could benefit from this experiment. There are several regions on this planet that are covered with high-salinity soil, such as parts of the Australian desert.
But perchlorate salts is just one issue facing would-be Martian farmers. Martian soil is lighter and looser than soils on Earth, meaning they would drain water faster than our soil. It’s also missing many nutrients on which we rely to grow crops, such as nitrogen. Plus, Mars has about a third of Earth’s gravity, which could be disorienting for plants that rely on gravity to root into the ground.
However, we may be closer than we think to providing astronauts with a semi-varied diet. In recent studies, wheat, mustard and tomatoes have all performed well in simulated conditions. Those on the mission to Mars may not be able to order a pizza, but they might just be able to make one themselves.