 Thus, on the time scale of hundreds of millions of years Pluto's orbital phase becomes impossible to determine, even if Pluto's orbit appears to be perfectly stable on 10 MYR time scales (Ito and Tanikawa 2002, MNRAS).Jupiter's moon Io has an orbital period of 1.769 days, nearly half that of the next satellite Europa (3.551 days).They are in a 2