Firing all thrusters...
Hi All
Jacob the puzzle is exactly the reverse - if Phoebe is a captured KBO how did it get braked into an orbit? One of the crater digging impacts seems a likely suspect. Orbital captures without tidal dissapation, a braking medium or a third body interaction are physically impossible otherwise.
Perhaps Phoebe was once a binary? But the number of outer satellite dynamical families seems to indicate a lot of collisions leading to capture, so that's my preferred option.
Adam