The soil and water of Mars are normally too harsh for crops, but research led by a then-high school sophomore finds that alfalfa plants and photosynthetic bacteria might help make Martian soil and water fit enough to support farming.
Feeding crews on Mars will be a major challenge for any long-term human mission there, given the high costs of launching anything from Earth to the Red Planet. Scientists have long sought ways to raise crops on Mars, but its soil is poor in the organic nutrients most plants need to grow, and its water is extremely salty.
In the new study, researchers investigated ways to make the most of Martian soil and water. Past volcanism on the Red Planet means that Martian soil is mostly crumbled volcanic rock, so the scientists experimented with volcanic rocks bought from hardware and fireplace stores.
Leading this research was Pooja Kasiviswanathan, who started the project when she was a sophomore at Ames High in Iowa. "Growing up, I always used to wonder if there is a potential for life in extraterrestrial environments, which lead to my strong passion in astrobiology," Kasiviswanathan told Space.com.
The researchers discovered that alfalfa, which is commonly harvested as hay for cattle, grew well in this nutrient-poor soil. Moreover, when the scientists ground up these alfalfa plants, the resulting powder could serve as fertilizer to help turnips, radishes and lettuces grow in the otherwise barren Mars-like soil.
"I find it most surprising that we were able to grow alfalfa just on simulated Martian regolith with no nutrient amendments," study co-author Elizabeth Swanner, a biogeochemist at Iowa State University in Ames, told Space.com. "This holds promise because alfalfa can then be used to fertilize the regolith and grow food plants that normally would not grow in this material."
The struggle to grow crops on Mars is one of the main challenges faced by the hero of the Golden Globe- and Hugo Award-winning 2015 film "The Martian," which helped inspire the research. "This movie made me more curious as to how we may be able to develop strategies to grow plants in Martian conditions to benefit future human missions to Mars," said Kasiviswanathan, now a junior at Iowa State University in Ames.
The scientists also found that a photosynthetic marine bacterium strain known as Synechococcus sp. PCC 7002, which is often employed in seawater biodesalination plants on Earth, was effective in removing salt from briny water much like that of Mars. The researchers could even enhance this desalination by filtering water exposed to the bacteria through the kind of volcanic rocks found on the Red Planet.
"I hope that our findings can support research for NASA's Mars mission for the near future," Kasiviswanathan said.
However, although food crops did grow in the enriched soil, the result still didn't match terrestrial produce, as the turnips, radishes and lettuce the scientists grew were not very nutritious. "These foods certainly provide essential vitamins and minerals to humans, although they may not provide much calorie density," Swanner said. "I think this study demonstrates that biofertilization is possible with alfalfa, and other plant-based food growth should be investigated in the future."
In addition, although the soil and water mimicked Mars, the air was less of a match. The researchers did try performing these experiments in a Mars-like carbon-dioxide-rich atmosphere, but it proved very difficult to grow plants in an airtight environment. "This was a challenge for us with a limited budget, but is also certainly a next step for the research," Swanner said.
The scientists detailed their findings Wednesday (Aug. 17) in the journal PLOS ONE.