Across the world, Elon Musk’s grand plans to colonize Mars have been both embraced with enthusiasm and derided with frank skepticism. As a life-long fan of science and science fiction, I’ve had one foot in each camp. In recent years, however, I’ve leaned ever closer to the skeptical point of view thanks to a rekindled interest in nutrition, and a growing doubt that Mars civilization planners have adequately considered the subject. Granted, humans living on Mars can probably survive on rations shipped from Earth for the first few years but, in order for permanent Mars habitation to work in the long run, food will have to be grown on Mars. Without a complete diet of nutritious food, Mars inhabitants cannot survive long term.
To be healthy, humans need specific amounts of vitamins, minerals, and micronutrients in addition to macronutrients like protein, fiber, and starch. To take one example, selenium is a micronutrient vital to long term health. We only need a tiny bit of it – an average of 55 micrograms/day for adults. Among the body’s various needs, our thyroid gland requires selenium to function properly. A number of things can go wrong in human physiology when the thyroid doesn’t get enough selenium: even moreso when the human in question isn’t yet fully grown. Selenium can be found in meat, seafood, cereals, grains, dairy, nuts, fruits, and vegetables. However, ultimately selenium originates in the soil. Plants pull the micronutrient out of the soil, animals eat the plants, and humans eat the plants and animals. Whether or not the food we choose to consume is animal-centric or completely vegan, if the soil the food is grown in doesn’t contain selenium (such as some parts of Asia) then the local population suffers disease. As far as anyone knows at this time, there isn’t any selenium in martian soil. Sure, there might be, but even if it were found in one region of Mars, we still wouldn’t know how widely distributed it might be. This martian uncertainty holds true for most nutrients we tend to take for granted on Earth.
On a more positive note, scientists have just recently developed a head of lettuce that produces a “bone-stimulating” hormone to benefit human space travellers. This is important news, as astronauts lose bone mass during long stays in space, an unhealthy side-effect of weightlessness. The new strain of lettuce is designed to prevent bone loss, a technology that will be crucial on the long flights to Mars. Given enough time, science can solve any problem humans might encounter as inhabitants of Mars, but will it be soon enough? We can bet that future Mars settlers will encounter problems for which there are currently no solutions. I expect Musk will be landing Starship-loads of optimistic colonists on Mars long before all the necessary solutions are found to fundamental physiological problems in human spaceflight.