Coupled mineralogical and nano-mechanical characterization of calcium sulfate veins in Martian analog rocks: Implications for Mars sample return drilling strategies

Mars sample collection is often hindered by the mechanical fragility of calcium sulfate-filled fractures, which are prone to fragmentation under drilling-induced stress. This study presents a coupled mineralogical and nano-mechanical investigation of such fracture systems in terrestrial Martian analog rocks, aiming to inform Mars Sample Return (MSR) drilling strategies. X-ray diffraction (XRD), scanning electron microscopy in backscattered mode (SEM-BSE), and energy-dispersive spectroscopy (EDS) reveal that gypsum is the dominant fracture-filling phase, exhibiting spatial continuity but considerable heterogeneity at vein–matrix interfaces. The host matrix consists primarily of quartz, albite, and dolomite, creating stark mineralogical contrasts that control fracture evolution and mechanical response. Nano-indentation testing was conducted across gypsum, matrix, and interfacial regions, revealing significant differences in mechanical properties. Gypsum zones show pronounced plasticity and low elastic modulus (E ≈ 10–20 GPa), while matrix minerals such as quartz exhibit higher stiffness (E > 100 GPa) and hardness. Critically, vein–matrix interfaces display intermediate properties and increased indentation depths, indicating weak interfacial bonding and stress localization. These mechanically vulnerable zones are likely to fracture or delaminate during coring operations. By integrating mineralogical heterogeneity with mechanical behavior, this study identifies key failure mechanisms in sulfate-rich terrains and formulates drilling and coring recommendations tailored to mitigate damage. The findings provide essential guidance for tool design, load control strategies, and sample targeting, ultimately improving the reliability of core recovery and scientific return in future Mars exploration missions.