When the first living visitor from Earth lands on Mars we might well expect it to be a man or a woman, but if students from the University of Southampton Spaceflight Society have their way, it could be one small step for a lettuce. That may seem more than a bit mad, but its part of an experiment to see if crops can grow in the Martian environment as a prelude to colonization.

If Mars is ever going to be colonized, the pioneers are going to have to learn to live off the land. Shipping food, water, air, spare parts, and the other necessities of life would be insanely expensive, and a completely self-contained habitat, even if feasible, misses the point of colonization and might as well be built in the Gobi Desert or Antarctica. A truly success colony will need, for example, to use the Martian air and the Martian sunlight to grow crops.

Developed by a team of under and postgraduate students as part of an international competition sponsored by the Mars One group, the Southampton #LettuceOnMars experiment consists of a small greenhouse that will be able to grow lettuces using the atmosphere and sunlight on Mars. The goal is to demonstrate that it is feasible to grow crops on Mars with an open-ended technology that uses Martian resources rather than the closed systems used in gardening experiments on the International Space Station or relying on materials sent from Earth.

The #LettuceOnMars team

The greenhouse consists of an aircraft-grade aluminum case with a polycarbonate dome, which is curved to prevent to accumulation of dust in the event of a storm, blocks the hard UV radiation from the Sun, and acts as a bioshield to separate the growing area from the outside world. In addition, the experiment also includes pumps for pressurizing the extremely thin Martian atmosphere; filters to keep out dust; a heater; supplies of water, nutrients, and pH balancing chemicals; and a bank of UV lamps.

The latter is particularly important because the sunlight on Mars is only half as bright as it is on Earth. On the best days, it only reaches the level of an overcast winter's day, so LEDs designed to shed a narrow spectrum of light to promote growth will be used as a supplement.

So why choose the common lettuce? According to the Southampton team, it is because lettuce is often used in growing experiments, has already flown in space several times, is edible, grows quickly from hardy seed, and is compact.

Block diagram of the Martian lettuce experiment

At the beginning of the mission, the experiment, if selected, will be inactive and the lettuce seeds frozen into a state of dormancy for the seven-month voyage to the Red Planet on the Mars One unmanned lander in 2018. The landing area has yet to be determined, but Mars One says it will be in a band covering the ancient Martian seabeds that now form the northern plains of Mars between 40⁰ and 50⁰ latitude. This is regarded as an area for a future colony because the air pressure is slightly higher than in the uplands.

On the surface, the greenhouse will be heated to 21⁰ to 24⁰ C (70⁰ to 75⁰ F), then pressurized using the Martian atmosphere combined with nutrient-laced water vapor and oxygen generated by electrolysis. Once the seeds have germinated, the twilight-like Martian sunlight will be supplemented by the LEDs as cameras and sensors track the growth of the lettuces over a four week period. After the experiment is complete, the heating unit will be turned up to high to kill the lettuces and destroy and living organisms that might be in the greenhouse to avoid contaminating the Martian environment.

"To live on other planets we need to grow food there. No-one has ever actually done this and we intend to be the first," says project leader Suzanna Lucarotti. "This plan is both technically feasible and incredibly ambitious in its scope, for we will be bringing the first complex life to another planet. Growing plants on other planets is something that needs to be done, and will lead to a wealth of research and industrial opportunities that our plan aims to bring to the University of Southampton. We have tackled diverse sets of engineering challenges, including aeroponic systems, bio filters, low power gas pressurization systems and failsafe planetary protection systems and then integrated them all into one payload on a tight mass, power and cost budget."

The #LettuceOnMars project is one of ten university team finalists vying for a spot on the Mars One's unmanned lander, which is scheduled to touch down in 2018. According to the team, the Southampton experiment has passed the technical review and is now awaiting the results of a popular online vote, which ended on December 31.

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