Evaluation of Candidate Crop Plant Lactuca Sativa in Biologically Enhanced Martian Regolith

Abstract

Under a recent NASA EPSCoR grant, the Department of Space Studies at the University of North Dakota, in collaboration with SyNRGE LLC developed a project to demonstrate the feasibility of biologically processing Martian regolith and inedible biomass through vermicomposting to reduce waste volume, enhance quality of regolith and recycle and replenish nutrients. Eisenia fetida (Red Worms) were fed inedible biomass, consisting of spent growing media, inedible biomass (root balls, leaves, and stems) shredded paper, and other compostable materials, that are produced during simulated planetary missions in the Inflatable Lunar/Mars Habitat (ILMH) analog facility at the University of North Dakota. In situ Martian regolith was simulated by adding Martian Global Simulant (MGS-1) into the E. fetida feedstock where it was consumed and assimilated by the worms. The biocompatibility of bioprocessed Martian simulant on growth of L. sativa were then evaluated using a seedling bioassay system. Lettuce seeds planted on MGS-1 alone germinated but failed to grow. Seeds planted in processed biomass contained from 10 to 25% vermicomposted MGS-1 germinated and grew with no discernable nutritional deficiencies. Fresh weight of the lettuce grown on vermicultured regolith ranged from 70 to 76% of a commercial potting mix containing controlled release fertilizer. These results suggest that vermicomposting of inedible biomass with E. fetida in Martian regolith is a viable technology for use in a closed ecological life support system (CELSS). Eisenia fetida can be maintained in dormant condition, consume a wide range of organic material, and require limited volume to be effective. The optimal environmental setpoints are like that of the crop growth requirements and establishing a self-replenishing population eliminates resupply cost. Although these results are very promising, several factors were identified that need to be understood before vermiculture can be recommended as technique for in situ processing of regolith.