Spin period change with ejecta mass. Panel (a) shows the case when the average initial ejecta speed is the lowest to escape from Dimorphos’s gravity, ∼0.08 m s⁻¹. Panel (b) displays the case when it is the highest to stay inside the Didymos−Dimorphos system, ∼0.12 m s⁻¹. The lines with different colors are the spin period changes due to Didymos’s dimension. The color styles are identical to those in Figure 2. The blue line shows the nominal case when a₀ = 413 m, b₀ = 395.5 m, and c₀ = 298 m. The yellow line illustrates the case when a₀ = 393 m, b₀ = 375.5 m, and c₀ = 318 m. The green line shows the case when a₀ = 433 m, b₀ = 415.5 m, and c₀ = 318 m. Finally, the red line illustrates the case when a₀ = 413 m, b₀ = 395.5 m, and c₀ = 278 m.