Examination of the asymptotic velocity distribution of the unbound tail. The left-hand panel highlights the spatial distribution of the velocity within unbound material, overlaid with contours of the density at ρ_planet = 10⁻⁶, 10⁻⁴, and 10⁻² g cm⁻³. The velocity histograms in the right panel are compared to the analytic estimate of $v_{\mathrm{\infty }}\sim \sqrt{2\mathrm{\Delta }E}$, shown with a vertical dashed line. A comparison between all of the unbound debris and that originating in the outer 10% of the original planetary radius shows that the outermost layers form the fastest-moving ejecta. The interface between composition and kinematics is important in chemically differentiated planets because it determines which layers are expelled with a certain velocity.