As space agencies and private companies around the world gear up to send human missions to Mars within decades, many questions remain about how to make these missions successful. Unlike rovers or probes, human astronauts are needy – and it will cost an astronomical amount to send all the food, water and oxygen they require from Earth.
But could we instead create these essentials on Mars, using local resources?
Now, a team led by astrobiologist Cyprien Verseux from the University of Bremen, Germany, has shown that Anabaena cyanobacteria can be grown at low pressure, using water and the carbon and nitrogen from gases in the Martian atmosphere.
“Under these conditions, cyanobacteria kept their ability to grow in water containing only Mars-like dust and could still be used for feeding other microbes,” says Verseux. “This could help make long-term missions to Mars sustainable.”
The study is published in the journal Frontiers in Microbiology.
All species of cyanobacteria (also known as blue-green algae) produce oxygen through photosynthesis, and some can also fix atmospheric nitrogen into nutrients: two useful properties to create biological life-support systems. But the Martian atmosphere has less than 1% of Earth’s atmospheric pressure, which is too low for cyanobacteria’s metabolism.
Fully recreating an Earth-like atmosphere on Mars would be expensive, so instead the research team found a middle ground.
They developed a bioreactor containing an artificial Mars-like atmosphere at low pressure, as well as water mined from ice, and nutrients from Mars-like “regolith”, the dust covering Earth-like planets and moons. Martian regolith has been shown to be rich in nutrients such as phosphorus, sulphur, and calcium.
Anabaena sp. PCC 7938 was first grown for 10 days at a pressure about 10 times lower than Earth’s, in a gaseous mix of 96% nitrogen and 4% carbon dioxide. Then, the researchers added their replica Martian regolith (called “Mars Global Simulant”), developed by the University of Central Florida.
The cyanobacteria grew well under all conditions – and even better, it was also able to help grow other microbes.
The team used ground-up dried Anabaena as a substrate for growing E. coli bacteria, a less hardy type of bacteria that can produce food products and medicine in Martian environments. Anabaena provided enough sugars, amino acids and other nutrients to feed and grow E. coli, which suggests that it could be used as the basis for Martian life-support systems – potentially producing food, drugs, biomaterials and useful chemicals.
But the authors caution that further studies are necessary before this system is ready to blast off to outer space.
“Our bioreactor, Atmos, is not the cultivation system we would use on Mars: it is meant to test, on Earth, the conditions we would provide there,” explains Verseux. “But our results will help guide the design of a Martian cultivation system.”
The team say they need to finetune the combinations of pressure, carbon dioxide and nitrogen for optimal bacterial growth. They also want to test other kinds of cyanobacteria – including potential future species genetically engineered for space missions.
With further research, Martian settlers might become strikingly similar to pioneers of earlier generations – able to live off the land.