Tidal evolution in the Neptune-Triton system

Triton, which is currently spiralling toward Neptune due to tides raised on both bodies, possesses an obliquity which may lie close to either a zero-deg 'state 1' or a 100-deg 'state 2' which correspond to the two stable Cassini extrema of its rotational Hamiltonian. The Kaula (1966) tidal formalism is presently used to model the past and future evolution of the system in both states. For nominal parameters in state 1, Triton will reach Neptune's Roche limit in about 3.6 Gyr with a decrease in orbital inclination to 145 deg from the current 159 deg; in the case of state 2, Triton's inclination will increase to 180 deg in 10-100 million years and then transition to state 1, subsequently reaching the Neptune Roche limit in about 1.4 Gyr.