A DYNAMIC HISTORY OF THE INNER NEPTUNIAN SATELLITES

We examine a scenario involving the capture origin of Triton and infer the probable dynamical history of the Neptune satellite system. Triton's highly elongated postcapture orbit forced chaotic perturbations of the eccentricities of the original inner satellites of Neptune. The resulting large eccentricities quickly led to mutual collisions and self-destruction of the inner satellites, leaving a disk of debris. Thus, Neptune's inner satellite system reformed on equatorial orbits after Triton's orbital circularization. It is unlikely that these reformed satellites survived the flux of cometary impactors. Hence, today's satellites are probably the remnants of parent satellites destroyed even more recently than Triton's capture. The remaining puzzle is the inclination of 1989N6, at 4.7°. This is probably due to a temporary inclination resonance capture. 1989N6 has passed through ≤35 inclination resonances in its history. The probability of avoiding all of these is ∼24%; we suggest that 1989N6 was temporarily caught in one. The 1989N6-1989N3 12 : 10 resonance has a 2 : 1 secondary resonance that would eject 1989N6 from the primary resonance at an inclination of roughly 4.7°, matching the observations. We have established the following limits for the Q value of Neptune: 12,000 < QN < 330,000. The upper limit is found by requiring the resonant configuration to have occurred during the satellites' lifetimes, and the lower limit is found by requiring 1989N1 to not tidally evolve through corotation. © 1992.