When astronauts travel to Mars, they may need to stay on the planet for as long as a year- and-a-half before the planets align properly for their trip home. Carrying the food needed for this long stay would be difficult and expensive. That’s why researchers hope that Mars travelers can grow their own food by farming on Mars.
This wouldn’t be easy. The Martian air is thinner than at the top of Mount Everest, and Martian nights are colder than Antarctic winter. So, Martian farmers would need to grow their crops in a pressurized, heated greenhouse.
Then there’s the problem of Martian soil. Strictly speaking, Mars doesn’t have soil. Its surface is covered with powered rock called regolith. This regolith lacks the organic components that soil scientists consider an essential part of Earthly soil. In the science fiction movie The Martian, astronaut Mark Watney solved this problem by simply adding poop to Martian regolith.
In 2020 a team of American scientists published results indicating that reality will be a bit more complicated. To experiment with Martian agriculture, the researchers use simulated regolith prepared based on chemical analyses returned by Mars rovers. They found that when they simply added nutrients to the regolith, such as Watney’s poop provided in the movie, nothing grew.They had to treat the regolith with acids, to neutralize other chemicals present. They also noted that Martian regolith contains toxic perchlorates. Since certain bacteria eat perchlorates, the researchers proposed that regolith could be treated with these bacteria. As a bonus, this treatment would produce oxygen. More work is needed to fine-tune the recipe for Martian agriculture.