Fig. 6

Schematic illustration of Ryugu’s surface formation process. The flow along the surface is driven by F_φ as an along-slope flow. As a result, segregation occurs and creates a vertically decreasing distribution of particles in size along the depth. Finer particles may acquire large random velocities to escape from the asteroid. The fragments with a power-law size distribution will then be produced by impacts. Thus, a 2-layered structure will be formed; an outermost surface layer consisting of the fragments with a power-law size distribution and a subsurface layer having a large number of particles with sizes within a specific range