Marangoni effect and its potential utilization in supporting lunar habitats and other extraterrestrial endeavors

Abstract

Tears of wine is a phenomenon frequently observed as a ring of wine formed near the top of the glass generates droplets that fall back into the wine. This phenomenon can be explained by the Marangoni effect driven by the surface tension created via gradient on concentration and temperature along the interface between two phases. Besides being observed while drinking wine, the Marangoni effect is crucial for welding metals, manufacturing integrated circuits, and growing crystals. This paper aims to establish that the Marangoni effect has the potential to be also crucial supporting lunar habitats and other extraterrestrial endeavors, as vacuum and reduced gravity are expected to augment the Marangoni effect on extraterrestrial molten soil leading to sustainable extraterrestrial in-situ resources utilization (ISRU). The authors conducted a Marangoni effect assessment on molten lunar regolith via JSC-1A lunar regolith simulant under vacuum yielding a spontaneous upwards migration of a uniform molten thin-film front as well as at bulk scale that climbed the crucible wall covering the entire wall’s surface and reaching the crucible’s top end. This unique formation and self-migration of a thin-film front could enable key ISRU processes such as, thin-film coating, crystal growth, and feedstock generation for additive 3D printing. Further assessment on higher-temperature vacuum-driven decomposition of the uniform thin-film front as it climbed the crucible’s wall revealed a significant decomposition of various simulant’s metal-oxide components into their respective oxygen and metal elements strengthening the feasibility of extraterrestrial generation and fractional separation of oxygen and metals/alloys with none or minimal need for terrestrial precursors. These two-coupled phenomena, spontaneous material transportation at both thin-film and bulk scales via Marangoni effect and vacuum-driven decomposition open novel pathways in extraterrestrial mining and manufacturing. Future extraterrestrial mining will require an operational approach completely different from the terrestrial one that heavily relies on not only mechanical excavation and transportation but also on a stand-alone refinery process to extract the mineral components. In this paper, the authors propose an extraterrestrial all-in-one mining process in which the Marangoni effect would allow non-mechanical transportation of the extraterrestrial mineral to feed an also in-situ pyrolysis-based refinery unit.