On the cost-efficiency of cyanobacterium-based, biological ISRU on Mars

To be sustainable, a settlement on Mars should be as independent of Earth as possible in terms of material resources. This independence may be reached with the help of biological systems: those could perform a wide range of functions with a low impact on the surroundings. However, biological systems would best rely on resources available on Mars – as recycling alone would mean that the amounts of available resources decrease over time – and most organisms cannot utilize raw Martian resources directly.

A solution has been proposed which lies in using diazotrophic, rock-weathering cyanobacteria. Their physiology is such that they could, it seems, be fed with materials available on site: water mined from the ground or atmosphere; carbon and nitrogen sourced from the atmosphere; and the local regolith, from which it has been argued that they could extract the other necessary nutrients. The cultured cyanobacteria could then produce various consumables directly, such as dioxygen and dietary supplements but also support the growth of secondary producers (plants or microorganisms) which could, in turn, generate a wide range of critical consumables.

Various proofs-of-concept have been reported in the literature and evidence accumulates that some cyanobacteria could, indeed, be fed from Martian resources and provide feedstock for other organisms of biotechnological interest. But whether a system works at all is not sufficient to decide whether it should be integrated into mission plans: its cost-efficiency must be determined and compared to potential alternatives.

Among the factors that will determine this cost-efficiency is the fitness of cyanobacteria under (i) hypobaria (low pressures), and as a result low partial pressures of dinitrogen; and (ii) a dependence on regolith for all nutrients not provided as gases, which would also lead to high concentrations of highly oxidizing compounds (chiefly, perchlorates) in the extracellular medium. Another key element is the design of specific cultivation hardware.

In this presentation, we will present the wet-lab and in-silico work performed at the ZARM’s Laboratory of Applied Space Microbiology to study those factors and thereby assess, and improve, the efficiency of cyanobacterium-based, biological ISRU on Mars.