Fig. 2: Basalt identification and mineralogical composition in CE5 and CE6 bulk soils.

a Scanning electron (SE) microscopy image of a representative subophitic-textured basalt particle selected from the CE5 sample. This particle was also located within the bulk soil CT scan region and was used for intensity-density calibration in CT radiography (Supplementary Fig. 2). Labels indicate mineral abbreviations. b Four types of identified basalt textures. The two larger particles on the left exhibit well-preserved poikilitic and subophitic textures, which dominate the basalts composition^24,30 and are reliably classified in this study. The two smaller particles on the right display partially striped textures and are classified as basalt fragments. All basaltic particles included in this study have equivalent diameters >25 μm; particles smaller than this threshold, if assigned as basalt by machine learning, are considered potentially misclassified due to unresolved internal textures and are manually reassigned to the “unknown” group. Labels denote density-based mineral phases distinguished in CT radiographs, as defined in Supplementary Fig. 2. c CT radiograph of the bulk soil scan, showing basalts accurately identified using a machine learning algorithm (blue). d Ternary plot showing the composition of basalts in the bulk soil, classified into Hp, Mp, and Lp. Pentagons represent the average volumetric proportions of three phases in basalt from the CE5 (red) and CE6 (blue) bulk soil samples, respectively. Red and blue shaded regions represent the 95% probability density contour of the data from CE5 (n = 2250) and CE6 (n = 4287) basalts, respectively. Apollo data and individual large basalts from the CE5 and CE6 samples are also plotted for comparison^30,54,110. e Average TiO₂ and Al₂O₃ compositions of basalts in bulk soil, inferred from the mineral phase proportions shown in (d) are based on the relationships established in Supplementary Fig. 5d, e. Pentagons and data in the background are defined in (d). Data from previous lunar missions are included for comparison^30,54,110.