Raphael Thys
Illustration of a photobioreactor as part of a biological life support system for a Mars habitat. Credit: Joris Wegner/ZARM/Universität Bremen
Scientists, futurists, and fans of science fiction alike have all dreamed that someday, humans would set foot on Mars. With the dozens of robotic orbiters, landers, rovers, and aerial vehicles we have sent there since the turn of the century (and the crewed missions that will follow in the next decade), the prospect that humans might settle on the Red Planet is once again a popular idea. Granted, the challenges of getting people there are monumental, to say nothing of the challenges (and hazards) associated with living there.
No matter how many people are willing to make a one-way trip and commit to living on Mars, establishing an outpost of humanity there will require some serious innovation and creative thinking! According to a new study by an international research team led by the Center of Applied Space Technology and Microgravity (ZARM), cyanobacteria might be able to withstand the difficult conditions and even thrive in Martian soil. This research suggests that astronauts could create biomass on Mars that would create a biological cycle.
The study that describes their findings recently appeared in the journal Applied and Environmental Microbiology. The research was led by Cyprien Verseux, the head of the ZARM Laboratory of Applied Space Microbiology at the University of Bremen, Germany. He was joined by fellow ZARM scientists Tiago Ramalho and Guillaume Chopin; Nicolas Tromas of the Laboratoire des Sciences du Numérique de Nantes (LS2N) and the University of Montreal; and Olga M. Pérez-Carrascal of UC Berkeley’s Department of Integrative Biology.
As they note in their study, future missions to Mars will need to be able to rely on in-situ resource utilization (ISRU) to ensure that they are self-sufficient as possible. Astronauts traveling to Mars will be orders of magnitude farther away from Earth than any previous mission in history. And since it takes six to nine months to send a spacecraft there, and only when Earth and Mars are closest in their orbits to each other (aka. “Opposition,” which happens every 26 months), sending resupply missions will be entirely impractical.
While ISRU presents several applications for securing building materials (Martian regolith) and providing astronauts with water (harvesting local ice), local resources could also be used to create biological systems. Microorganisms could be used to produce food, oxygen, biomaterials, pharmaceuticals, chemicals, and even for mining metals from surface rock and processing waste. For many years, scientists at ZARM have been investigating cyanobacteria for potential ISRU applications on Mars.
In particular, cyanobacteria’s photosynthetic abilities, nitrogen-fixing activities, and lithotrophic features (using minerals for biological processes) could be used to provide for the everyday needs of astronauts. In terms of resources, Mars’ atmosphere is 95% CO2 and 3% nitrogen by volume, while its regolith is rich in iron and other useful minerals. From these, certain species of cyanobacteria could produce oxygen gas and biomass that could serve various purposes – including food production.
“When humans go to Mars, we will need to provide them with large amounts of consumables: food, water, oxygen, and sometimes medication. And if our presence there is to be sustainable, all that cannot come from Earth, the costs and risks would be too high,” said Dr. Verseux in a ZARM press release. For the sake of their study, Verseux and his colleagues studied various cyanobacterium strains and determined one (Anabaena sp. PCC 7938) to be a highly promising candidate.
Cultivation of duckweed using Anabaena sp. PCC 7938 in comparison to high-purity water (ddH2O) and a standard nutrient solution (Hoagland). Credit: Guillaume Chopin/ZARM/Universität Bremen
Finding the right candidate strain has been a stumbling block for researchers, as the phylum Cyanobacteria includes thousands of species. But with this one strain as the shared model, bioregenerative life-support systems may finally have the cyanobacteria they need. As Dr. Verseux explained, the process of identifying this bacteria was long and intensive:
“We first preselected a few cyanobacterium strains based on knowledge already available. We then looked for insights into these strains’ genomic DNA, and finally compared them through a series of experiments in the laboratory. In short, we had two sets of criteria: The first pertained to the cyanobacteria’s abilities to feed on resources available on Mars. The second dealt with their abilities to support the growth of other organisms, such as edible plants and other bacteria, which would be highly valuable but could not use Martian resources as directly”.
To meet the second criterion, the team used the cyanobacteria as a single feedstock to cultivate duckweed (aka. “water lentils”), a nutrient-rich species of edible flowering aquatic plants that grow in freshwater ponds and slow-moving streams. “This plant grows extremely fast and is completely edible, which makes it a prime candidate for agriculture on Mars,” said Dr. Ramalho. “As a fun fact, we actually isolated our duckweed from a stream in the landscape park of Bremen.”
The science team hopes these findings will boost research into bioreactors, bioregenerative life-support systems, and other methods that rely on Earth-based biological systems to ensure sustainable living in space. This same technology could have immense applications here at home, where global populations continue to grow while climate change is disrupting the very ecological systems we rely on to feed and provide for ourselves. Whether it is solutions for living off-world or here at home, the name of the game is sustainability!
Artist’s impression of a Mars habitat in conjunction with other surface elements on Mars. Credit: NASA
In the meantime, Dr. Verseux indicated that more work and testing need to be done before any cyanobacteria-powered bioreactors are sent to Mars:
“Our work, and that of colleagues in this field, has brought promising proofs-of-concept. It seems that cyanobacteria could indeed be fed from Martian resources and then be used to feed other bioprocesses of interest. But knowing that this system could work at all is not enough. We need to improve it, assess whether it could be efficient enough to be worth integrating into missions to Mars and, if so, develop practical solutions – including hardware and processes.”
Dr. Verseux and his colleagues also need to conduct additional research to better understand the biological mechanisms that make the selected strain of Anabaena sp. PCC 7938 such a valuable candidate. They are joined by countless scientists, universities, and institutes worldwide engaged in similar research, specifically for applications that will advance space exploration in the near future. The ZARM team also hopes that its model strain will make it easier to compare results and build upon each other’s work.
“Things are just starting, and the amount of research work left could be daunting,” added Dr. Verseux. “Fortunately, it is taking the direction of a highly collaborative effort: The number of teams contributing to cyanobacterium-based life-support systems is increasing rapidly.”
Further Reading: University of Bremen, Applied and Environmental Microbiology