Challenge Background

Future planetary habitats on Mars will require a high degree of self-sufficiency. This requires a concerted effort to both effectively recycle supplies brought from Earth and use local resources such as CO2, water and regolith to manufacture mission-relevant products. Human life support and habitation systems will treat wastewater to make drinking water, recover oxygen from CO2, convert solid wastes to useable products, grow food, and specially design equipment and packaging to allow reuse in alternate forms. In addition, In-situ Resource Utilization (ISRU) techniques will use available local materials to generate substantial quantities of products to supply life support needs, propellants and building materials, and support other In-SpaceManufacturing (ISM) activities.

Many of these required mission products such as food, nutrients, medicines, plastics, fuels, and adhesives are organic, and are comprised mostly of carbon, hydrogen, oxygen and nitrogen molecules. These molecules are readily available within the Martian atmosphere (CO2, N2) and surface water (H2O), and could be used as the feedstock to produce an array of desired products. While some products will be most efficiently made using physicochemical methods or photosynthetic organisms such as plants and algae, many products may best be produced using heterotrophic (organic substrate utilizing) microbial production systems. Terrestrially, commercial heterotrophic bioreactor systems utilize fast growing microbes combined with high concentrations of readily metabolized organic substrates, such as sugars, to enable very rapid rates of bio-product generation.

The type of organic substrate used strongly affects the efficiency of the microbial system. For example, while an organism may be able to use simple organic compounds such as formate (1-carbon) and acetate (2-carbon), these “low-energy” substrates will typically result in poor growth. In order to maximize the rate of growth and reduce system size and mass, organic substrates that are rich in energy and carbon, such as sugars, are needed. Sugars such as D-Glucose, a six-carbon sugar that is used by a wide variety of model heterotrophic microbes, is typically the preferred organic substrate for commercial terrestrial microbial production systems and experimentation. There are a wide range of other compounds, such as less complex sugars and glycerol that could also support relatively rapid rates of growth.

To effectively employ microbial bio-manufacturing platforms on planetary bodies such as Mars, it is vital that the carbon substrates be made on-site using local materials. However, generating complex compounds like glucose on Mars presents an array of challenges. While sugar-based substrates are inexpensively made in bulk on Earth from plant biomass, this approach is currently not feasible in space. Alternatively, current physicochemical processes such as photo/electrochemical and thermal catalytic systems are able to make smaller organic compounds such as methane, formate, acetate and some alcohols from CO2; however, these systems have not been developed to make more complex organic molecules, such as sugars, primarily because of difficult technical challenges combined with the low cost of obtaining sugars from alternate methods on Earth. Novel research and development is required to create the physicochemical systems required to directly make more complex molecules from CO2 in space environments. It is hoped that advancements in the generation of suitable microbial substrates will spur interest in making complex organic compounds from CO2 that could also serve as feedstock molecules in traditional terrestrial chemical synthesis and manufacturing operations.

The CO2 Conversion Challenge is devoted to fostering the development of CO2 conversion systems that can effectively produce singular or multiple molecular compounds identified as desired microbial manufacturing ingredients and/or that provide a significant advancement of physicochemical CO2 conversion for the production of useful molecules.