Fig. 2

Zingg diagrams of lunar regolith particles showing typical particle shape distributions. A L1613-3 from Mare Fecunditatis (127–200 µm, mature or submature, and N = 389). B L24130.3–2 from Mare Crisium (74–95 µm, immature, and N = 1108). C 60,501 from Descartes Highland (75–105 µm, mature, and N = 104). D L2001-4 from Apollonius Highlands (200–450 µm, mature or sub mature, and N = 77). × and + denote particles in the second peak of the particle size histogram (I < 70 µm). L, I, and S are the longest, intermediate, and shortest lengths of three-axial lengths of a particle, respectively. The dotted lines show the 2D silver ratio