Chaotic structure of phase space as a function of period ratio and ﹩e/{e}_{\mathrm{cross}}﹩ for a test-particle subject to an exterior circular perturber with mass ﹩\mu ^{\prime} ={10}^{-5}﹩. The color scale indicates the Lyapunov time of chaotic trajectories computed for a grid numerical integrations (see text for initial conditions). Integrations that led to a close encounter (within one Hill radius) were stopped early and are marked in bright yellow. Initial conditions determined to have ﹩{t}_{\mathrm{Ly}}\gt 1300P^{\prime} ﹩ are assumed regular and marked as gray. The blue separatrices and our red overlap criteria are repeated from Figure 1.