Sintering of Mars Clay Mineral Simulants: Implications for Developing ISRU Technology on Mars

Clay minerals in craters and escarpments on Mars. Credit: NASA/JPL-Caltech/JHUAPL.

Developing an autonomous habitation using local resources is critical for future human expeditions to Mars. Fortunately, the constituents required to supply consumables essential for life have been identified on the martian surface over years of orbital and rover missions. Clay minerals on Mars are of interest for their potential utility. On Earth, applications of clays have evolved from food production, ceramics, and construction to advanced manufacturing, such as biomedical nanocomposites and photocatalysts. Compared to common Earth clays, the dominant clay minerals on Mars have greater iron concentrations, less porous molecular structure, and more variable reactivities. Therefore, In-Situ Resource Utilization (ISRU) technologies must test the suitability of martian clays for Earth-like applications since compositional and structural differences can affect nutrient cycling, water retention, plasticity, and overall reactivity. Only recently, ISRU-based research has started augmenting martian simulants (mostly crushed basalt) to include components such as clays that affect regolith properties.

David Karl from the University of Berlin and team sintered unfired regolith mixtures (green bodies) prepared from one of the few publicly available clay-rich martian simulants, MGS-1C. The stabilized regolith was shaped into utensils and bricks using a potterโ€™s wheel, molds, dry pressing, and 3D printing. The high clay content at about 40% by weight of the simulant MGS-1C acted as a nanosized binder and produced high-strength green bodies. Further treatment with a proprietary binder at less than 5% by weight produced water-resistant green bodies that withstood a pressure of 30.8 megapascals (MPa). Sintering these green bodies under martian conditions (1000ยฐC, vacuum, and 925 Pa CO2) increased the strength (about 58 MPa) close to regular concrete. This study showed that clay minerals enhance the mechanical and rheological properties of regolith-based construction materials. It demonstrates the effects of including Mars-relevant clays in simulants used for ISRU research and encourages upgrading experimental materials based on current martian surface exploration. READ MORE