A Low-Pressure, N2/CO2 Atmosphere Is Suitable for Cyanobacterium-Based Life-Support Systems on Mars

Abstract

The leading space agencies aim for crewed missions to Mars in the coming decades. Among the associated challenges is the need to provide astronauts with life-support consumables and, for a Mars exploration program to be sustainable, most of those consumables should be generated on site. Research is being done to achieve this using cyanobacteria: fed from Mars's regolith and atmosphere, they would serve as a basis for biological life-support systems that rely on local materials. Efficiency will largely depend on cyanobacteria's behavior under artificial atmospheres: a compromise is needed between conditions that would be desirable from a purely engineering and logistical standpoint (by being close to conditions found on the Martian surface) and conditions that optimize cyanobacterial productivity. To help identify this compromise, we developed a low-pressure photobioreactor, dubbed Atmos, that can provide tightly regulated atmospheric conditions to nine cultivation chambers. We used it to study the effects of a 96% N2, 4% CO2 gas mixture at a total pressure of 100 hPa on Anabaena sp. PCC 7938. We showed that those atmospheric conditions (referred to as MDA-1) can support the vigorous autotrophic, diazotrophic growth of cyanobacteria. We found that MDA-1 did not prevent Anabaena sp. from using an analog of Martian regolith (MGS-1) as a nutrient source. Finally, we demonstrated that cyanobacterial biomass grown under MDA-1 could be used for feeding secondary consumers (here, the heterotrophic bacterium E. coli W). Taken as a whole, our results suggest that a mixture of gases extracted from the Martian atmosphere, brought to approximately one tenth of Earth's pressure at sea level, would be suitable for photobioreactor modules of cyanobacterium-based life-support systems. This finding could greatly enhance the viability of such systems on Mars.

Towards a Biomanufactory on Mars

“…support systems (Gòdia et al, 2002;Wheeler, 2017) and a Martian atmosphere has been shown to support such biological systems (Verseux et al, 2021). While plant-based food has been the main staple considered for extended missions (Drake et al, 2010;Anderson et al, 2018;Cannon and Britt, 2019), the advent of cultured and 3D printed meat-like products from animal, plant and fungal cells may ultimately provide a scalable and efficient alternative to cropping systems (Cain, 2005;Pandurangan and Kim, 2015;Hindupur et al, 2019).…”

Choice of Microbial System for In-Situ Resource Utilization on Mars

“…Both approaches have trade-offs in terms of equivalent system mass (Bugbee et al, 2020), and either further complicates the already complex design of photobioreactors (Johnson et al, 2018). If footprint and productivity constraints are relaxed (considering semi-open cultivation-systems like domed and pressurized ponds instead of photobioreactors), however, it is a straight forward way to generate initial biomass, which can serve as foundation for further biology (Billi et al, 2021;Verseux et al, 2021). Light-independent, lithoautotrophy can fix carbon by relying on chemically provided reducing power.…”

“…For production of biomass, the diazotrophic and spore-forming cyanobacterium species Anabaena, which is tolerant to Mars-like growth-conditions (Verseux et al, 2021), holds great promise. Synechocystis sp.…”

Biologically-Based and Physiochemical Life Support and In Situ Resource Utilization for Exploration of the Solar System—Reviewing the Current State and Defining Future Development Needs

“…Verseux et al performed an investigation into the ability of Anabaena sp. to grow on a simulated regolith as well as in a controlled atmosphere of 96% N 2 and 4% CO 2 [ 26 ]. Their findings showed “vigorous growth” with the simulated conditions with an atmospheric pressure of only 100 hPa.…”

“…Further, they also analyzed the biomass resulting from the Anabaena sp. growth and deemed it was a viable substrate for other BLSS modules to be employed due to its use by strains of E. coli [ 26 ]. The growth of E. coli using the Anabaena sp.…”