Rice on Red Planet? Gene-edited variety could be grown on barren Mars

“We picked rice as it can persistently grow in a wide array of environments, but we are aware that its growth and ability to produce grains can be impacted by stress. We used these characteristics of rice as leverage to potentially grow an agricultural crop in Martian regolith simulant,” Abhilash Ramachandran, a post-doctoral fellow at the Arkansas Center for Space and Planetary Sciences, told Interesting Engineering (IE) via email. 

The Martian environment and soil conditions

Before we get into the specifics of growing rice on Mars, let's take a look at the big picture of the red planet's current conditions. 

Mars has become one of our solar system's most explored interplanetary destinations. This interest is due to its proximity and to the fact that billions of years ago, Mars may have had liquid oceans and a thick atmosphere and thus could have boasted a more hospitable environment — possibly even supporting microbial life. However, as time passed, the planet was transformed into the barren world we know today. The process by which Mars lost its atmosphere is still being studied. According to some studies, the loss of magnetic fields caused this drastic change, transforming Mars from a wetter and warmer world into a cold and dry planet. 

Today Mars has a thin, carbon dioxide-rich atmosphere (about 95 percent CO2 and just 1 percent oxygen), making plant and human survival impossible. The temperatures are also bone-chilling, to put it mildly with temperatures as low as -225 degrees Fahrenheit (-153 degrees Celsius).

Because the planet is farther away from our star than the Earth, less sunlight falls on its surface. With the lack of magnetic fields, it is also vulnerable to lethal cosmic radiation. 

Another barrier is the presence of toxic chemicals on the surface. Back in 2008, NASA’s Phoenix Mars lander spotted the widespread presence of the chemical perchlorate in soil, which can be harmful to growing plants. Additionally, Mars gets the name "red planet" from the abundance of iron minerals in its soil, which also pose a significant challenge to using the Martian soil for agriculture. 

Although there is evidence of some nutrients in the Martian soil, the quantity required to grow plants is generally considered insufficient, and the nutrients present may be concentrated in a few locations. However, when Phoenix performed its first wet-chemical analysis, it did detect evidence of mineral nutrients important to plants, such as magnesium, sodium, potassium, and chloride.

Overall, this paints a bleak picture of growing sufficient plants on Mars to support a colony. That said, even the most difficult situation appears to change when viewed through different lenses, and science and technology fuel a new vision for Mars' future. 

The gene-edited rice experiment 

With the current Martian soil conditions in mind, the team set out to learn how rice crops could withstand the stresses of growing in Martian soil. In their study, the researchers used two gene-edited lines with genetic mutations that better enable them to respond to stress, such as drought, sugar starvation, or salinity.  

A series of experiments were carried out to investigate the viability of growing rice plants inside a growth chamber using various ratios of the Martian simulant and the potting mix. Meanwhile, the Mojave Mars Simulant, or MMS (created by NASA and the Jet Propulsion Laboratory), simulates Martian regolith using basaltic dirt from the Mojave Desert.

The three rice varieties (one wild-type and two gene-edited) were grown in simulated Martian soil developed by scientists from NASA and the Jet Propulsion Laboratory and made from basaltic soil mined from the Mojave Desert. This simulated soil is called Mojave Mars Simulant (MMS). 

These three varieties of rice were grown in the MMS, in a regular potting mix, and in a mixture of the two. The plants were watered with "demineralized water" once or twice a day. 

While plants were able to grow in the MMS alone, these were not as developed as those grown in the potting soil and the mixture of MMS and potting soil. Replacing just a quarter of the Martian simulant with potting soil resulted in improved development.

The researchers also tested the ability of the gene-edited plants to grow in the presence of toxic perchlorate. Higher levels of perchlorate (3 grams per kilogram of soil), as expected, inhibited plant growth, whereas the gene-edited varieties showed some root growth when the toxic levels were reduced to 1 gram per kilogram. 

However, the level of magnesium chloride content in the soil was found to be detrimental to rice germination. To resolve this, the researchers suggested editing the SnRK1A gene to trigger mechanisms that could improve the plant's response to the magnesium chloride in the Martian soil.

“Our study shows mutation of genes responsible for the stress we found in rice plant grown in Martian regolith simulant could be an approach towards developing a line that can perform better in this environment,” said Ramachandran.

The challenges ahead

After this preliminary work, the team plans to test gene-edited rice on a newer Martian soil simulant known as the Mars Global Simulant. Experiments with strains that have increased stress tolerance for high salt concentrations are also in the pipeline. They will also look at what degree perchlorate may be leeching into the plants from the soil.

Ultimately, they would like to test the rice strains in a Mars simulation chamber that mimics the planet's temperature and atmosphere to see how gene-edited varieties perform.

As for thriving plantations on Mars, the team told IE: “Essential nutrients required for a plant have been detected on Mars. However, the availability of these nutrients in the right amount required is questionable, and we need to find a solution to address the problem. So, particular sites on Mars have to be studied for soil composition, and the necessary fertilizers can be added for successful plantation.” 

Aside from that, cultivating rice on alien land is not likely to be a straightforward process. And, we will need to learn a lot more about how to grow crops on Mars. As it will not be feasible to transport all of the necessary agricultural infrastructure and materials from Earth, some resources may have to be created from scratch. Even the hazardous chemicals present in the soil may need to be removed in novel ways to felicitate better plant growth.

Not to forget, with limited liquid water, frigid temperatures, less sunlight, radiation, and even dust storms — crops cannot be grown without the protection of greenhouses.

Scientists have been working on creating a controlled greenhouse environment to help Mars explorers overcome these challenges. Almost similar to the one created in the film The Martian, in which biologist Mark Watney becomes stranded on Mars. In order to survive, Watney creates a greenhouse to grow potatoes and uses metabolic waste as fertilizer for growth.

The International Space Station (ISS) has also been conducting experiments to understand the role of gravity and other space conditions in plant growth. While Earth-based analog missions in places such as Hawaii have been conducting plant experiments simulating Martian conditions. In 2022, the Chinese Academy of Sciences announced that rice seeds had been grown and harvested on the Chinese Tiangong space station. All of these experiments will eventually bring us closer to the end goal. 

If everything goes as planned, future first humans will have options other than packaged food, and it will be simple to cook rice as well on Mars. “Rice can become a source of carbohydrates and other nutrients (with biofortification) for humans who will be sent out for missions to Mars,” Peter James Gann, a doctoral student in cell and molecular biology and first author of the study, told IE. 

The team also mentions that this work also has the potential to improve rice varieties for use on Earth. 

The research, entitled, "Rice can grow and survive in Martian Regolith with challenges that could be overcome through control of stress-related genes,” was presented at the 54th Lunar and Planetary Science Conference 2023. The study can be accessed here.