We Grew Martian Tomatoes

This experiment was primarily the work of crewmembers Cecile Renaud and Julien Villa-Massone. As Commander of our two-week MDRS Crew 261 mission, I assisted with planning and procurement for this and our other crew experiments.

MDRS Crew 261, also known as the Transatlantic Mars Crew, was a two-week analog astronaut mission at the Mars Desert Research Station in Utah. Our international crew included Executive Officer Aline Decadi, Roboticist Erin Kennedy, Health and Safety Officer Audrey Derobertmasure, Biologist Cecile Renaud, Engineer Julien Villa-Massone, and Journalist/Artist in Residence Kris Davidson. Together we conducted 16 experiments spanning cardiovascular monitoring, pharmacology, plant biology, power systems, astronomy, robotics, and virtual reality—all aimed at advancing research and technology for long-term human presence on Mars.

During MDRS Crew 261, we conducted an experiment to grow tomato seedlings in Mars regolith simulant using compost amendments and spirulina as a biostimulant. This research explored sustainable agricultural techniques that could support future human settlements on Mars.

Why Growing Food on Mars Matters

Any permanent human presence on Mars will require the ability to grow food locally. The logistics of shipping food from Earth are simply not sustainable for a long-term colony—each kilogram sent to Mars costs tens of thousands of dollars and takes months to arrive. Future Martian settlers will need to produce their own calories, vitamins, and nutrients from the resources available on the planet.

This is where Mars regolith comes in. The rusty red soil that covers the Martian surface contains many of the mineral elements plants need to grow. However, it lacks the organic matter, beneficial microbes, and proper structure that make Earth soil fertile. The challenge is transforming this barren substrate into something that can sustain plant life.

Proving the Skeptics Wrong

Before our mission, Cecile and I heard the same refrain from nearly everyone we talked to: this is impossible. Previous crews at MDRS had attempted to grow plants in Mars regolith simulant and had consistently failed. The conventional wisdom was that it couldn’t be done without extensive soil processing or hydroponics—that attempting to grow anything directly in regolith was a waste of time.

We refused to accept that. Cecile brought her expertise as a biologist, and together with Julien’s engineering skills, we developed an approach that combined compost amendments with spirulina biostimulation. We believed that the right biological inputs could transform the regolith into a viable growing medium.

When our tomato seedlings pushed through the red soil and began to thrive, we took immense joy and delight in proving those skeptics wrong. For me personally, this success was especially meaningful. Back in 6th grade, I had argued with a teacher about the feasibility of growing plants on Mars. He insisted it was impossible—that Martian soil was too hostile, the conditions too harsh. I maintained that with the right approach, it could be done. Decades later, watching those green leaves emerge from Mars regolith simulant, I finally had my proof.

The PhotoBioReactor

A key component of our experiment was a custom PhotoBioReactor (PBR) rig. Cecile and Julien designed the system with input from Algacraft, who manufactured the parts. Cecile and Julien then assembled the PBR specifically for our mission, and Cecile procured the spirulina culture prior to our departure. The PBR allowed us to cultivate spirulina in a controlled environment, providing a renewable source of nutrients for our plant experiments.

We kept the spirulina colony alive in the PhotoBioReactor not only during the mission but for one full year afterwards at the MDRS Science Dome. This demonstrated the long-term viability of algae cultivation systems in analog Mars environments.

Spirulina Measurement and Harvest

After the mission, I measured the spirulina content using a drying and weighing process. This allowed us to quantify the biomass production and assess the efficiency of our PBR system over time.

With the spirulina colony thriving, we were able to tap it for plant biostimulation use cases. Spirulina contains nutrients, amino acids, and growth-promoting compounds that can enhance plant growth and resilience, making it an ideal supplement for growing crops in nutrient-poor substrates like Mars regolith.

Growing Tomatoes in Regolith

Mars regolith presents significant challenges for plant growth: it lacks organic matter, has poor water retention, and contains perchlorates and other compounds that can be toxic to plants. By combining the regolith simulant with compost and spirulina-based biostimulants, we aimed to create a more hospitable growing medium.

I processed the compost myself from vegetable scraps and other food waste from my kitchen using a Lomi countertop composter. This device rapidly breaks down organic matter into nutrient-rich soil amendment, simulating the kind of closed-loop waste processing that would be essential on a Mars base. Every bit of organic material on Mars will be precious—nothing can be wasted. The Lomi allowed us to demonstrate this principle by transforming kitchen scraps into a key ingredient for our regolith amendment.

Our tomato seedlings showed promising results in this amended regolith mixture, demonstrating that with the right biological inputs, Mars soil could potentially support food production for future colonists.

GreenHab Operations

The crew spent considerable time working in the MDRS GreenHab, tending to our experiments and documenting plant growth. The GreenHab serves as an analog for the pressurized greenhouse facilities that would be essential components of any Mars base.

Now Published in Nature

Cecile has continued this research, and I’m thrilled to share that her work on spirulina biostimulation has now been published in Nature. The study reveals fascinating insights into why our approach worked—and how it can be optimized further.

The research found that spirulina grown under nitrogen-starved conditions produces sugar-rich compounds that are particularly effective as biostimulants. When these extracts were applied to tomato plants, they increased flower production by nearly 50% and boosted fruit yields. Perhaps most surprisingly, the leftover culture water from growing spirulina—essentially the “waste water” that would normally be discarded—turned out to be more valuable than the spirulina biomass itself for stimulating plant growth.

The study also discovered that spirulina extracts positively alter the bacterial communities around plant roots, cultivating beneficial microbes that help with nitrogen uptake and stress tolerance. Even spraying spirulina extract on leaves changed the root microbiome, suggesting plants communicate these signals throughout their entire system. This research, partly funded by ESA’s MELiSSA program for closed-loop life support in space, validates what we observed at MDRS and points toward practical applications for both sustainable agriculture on Earth and future food production on Mars.

Looking Forward

This research contributes to our understanding of closed-loop life support systems for Mars missions. By cultivating spirulina as both a food source and agricultural input, we can create more sustainable and resilient food production systems that minimize the need for resupply from Earth.

The success of keeping our spirulina colony alive for over a year post-mission suggests that such biological systems could be robust enough for long-duration Mars missions, where reliability and longevity are critical.

I hope to take these learnings and the spirit of discovery we had—while proving the skeptics wrong—into my work at the Mars Technology Institute.

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Photos courtesy of Crew 261 (Kris Davidson, Cecile Renaud, Julien Villa-Massone) & The Mars Society.