Lunar and Martian Regolith Simulants Desorb and Weather after Exposure to Bioregenerative Life Support System Effluent

The extraction of plant essential nutrients from extraterrestrial regolith will be necessary to ensure the sustainability of lunar and martian agriculture. An essential instrument of these outposts will be bioregenerative life support systems (BLiSS) that attempt to fully recycle nutrients from organic wastes. While BLiSS may not be fully efficient and lead to a reduction in the quantity of some elements, it is necessary to explore if regolith can be used to fortify the composition of BLiSS effluent. Lunar (JSC-1A) and martian simulants (MGS-1) were reacted with a high-fidelity BLiSS effluent from NASA's Kennedy Space Center (KSC) in a 24 h batch experiment and compared to reactions with an inorganic nutrient solution and water. Net sorption and dissolution of elements were determined by quantification of reacting solutions using inductively coupled plasma-optical emission spectroscopy (ICP-OES), with P demonstrating Langmuir and Zn and K demonstrating Freundlich sorption isotherms. The lunar simulant desorbed sizeable quantities of S, followed by Ca and Mg, while the martian simulant desorbed S, followed by Mg, Ca, and Na. Elemental bonding of C, N, P, and Ca was observed on the simulant solid phase with X-ray photoelectron spectroscopy (XPS) after reaction with BLiSS solution. Minerals after experimentation were observed using scanning electron microscope-electron dispersive spectroscopy (SEM-EDS), revealing pitting in JSC-1A and covering of nanoparticles in MGS-1. There were marked differences between the reactions of the inorganic nutrient solution compared to BLiSS effluent, indicating the necessity to study high-fidelity solutions over single-element model systems. Overall, lunar and martian regoliths contain highly soluble components that may fortify BLiSS effluents with valuable metals and plant essential nutrients.