Scientists Weigh in on Whether Mark Watney's Martian Farming Would Really Work

Thursday, 29 October 2015 - 3:57PM
Space
Mars
Thursday, 29 October 2015 - 3:57PM
Scientists Weigh in on Whether Mark Watney's Martian Farming Would Really Work
In the highly popular and acclaimed new movie The Martian, based on the novel by Andy Weir, protagonist Mark Watney is forced to grow food in lifeless Martian soil when he's stranded on the Red Planet by himself for several years. He sets up a makeshift farm for himself, using his knowledge as a botanist to create a "soil recipe" that would support potato plants.

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"The theories behind what Andy Weir wrote in his book are sound," Jim Bell, a planetary scientist at Arizona State University, told Phys.org. "A good soil for growing crops will have structure to hold the plant up, and provide the nutrients needed for growth. This is where Watney was headed in his 'soil recipe.' Of course, he had to use only the resources with him on the planet."
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Since the Martian soil was missing biological ingredients such as nutrients and beneficial bacteria, he used the only biological material available to him: his own feces. We regularly use animal manure as fertilizer, so the reasoning is logical; however, human feces have human pathogens that may make you sick upon eating the resultant crops. Luckily, he was using his own feces (as well as the crew's freeze-dried feces, which wouldn't contain any live bacteria), so he would only contract the pathogens that were already in his body.

Opening quote
"You can get away with it in a desperate survival situation, where you are a single person using your own manure to grow crops that only you eat," Weir told Modern Farmer.
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As a result, the process Watney uses is relatively realistic, although there is, of course, some speculative science at work:

Opening quote
"In theory, Watney's waste would provide nutrients for growing plants. In reality, the Mars 'soil mixture' he made doesn't have the complex food web of microbes that we have on Earth," said soil microbiologist Mary Stromberger of Colorado State University. "So, there might be some issues with the recycling of nutrients between soil and plants and atmosphere. And, we don't know if the fecal bacteria could thrive on Mars, even in a controlled environment....On the other hand, he had to use what was there, and this is a sci-fi movie!"
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These statements are part of a larger conversation about soil and Martian habitability. On November 18, at the Soil Science Society of America's annual symposium, Bell will speak at a lecture called "Soils of Mars: Keys to Understanding the Habitability of the Red Planet," which will discuss the role of Martian soil (and possibly the role of feces) in the potential survivability of Mars.

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"The soil science community has defined soils to exist only on planet Earth, because the presence of life is critical" said symposium leader Harold van Es of Cornell University. "We need to start thinking about soils on other planets."
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