In the reference frame comoving with the planet the probe leaves with exactly as much energy as it arrived (modulo aerobraking and such). In the reference frame

In the reference frame comoving with the planet the probe leaves with exactly as much energy as it arrived (modulo aerobraking and such). In the reference frame of the solar system's center of mass, the planet will have transferred an imperceptible fraction of its orbital energy to or from the probe.