Examples of initial conditions for Nix. Top row: time variations in Nix’s semi-major axis (left) and eccentricity (right) for two different initial values of a_C. The initial conditions are a_C∕R_P = 3 and a_C ∕R_P = 7, e_C = 0.001, Ω_C ∕n_C = 2, A = 10, and Δt_P = 600 s. For a_C ∕R_P = 3, the eccentricity of Nix is excited to a mean value close to 0.16. Bottom row: time evolution of the mean-motion ratio (left) and two angles for Nix (right), namely, the secular angle, Δϖ, and the 4/1 MMR critical angle ϕ_4∕1 = 4λ − λ_C − 3ϖ_C. The mean value of n_C∕n is slightly smaller than 4 for a_C∕R_P = 7, whereas ϕ_4∕1 and Δϖ librate around 180° and 0°, respectively, for a_C∕R_P = 3.