Ganymede (moon) every orbit of Ganymede, Europa orbits twice and Io orbits four times. Conjunctions (alignment on the same side of Jupiter) between Io and Europa occur when Io is at periapsis and Europa at apoapsis. Conjunctions between Europa and Ganymede occur when Europa is at periapsis. The longitudes of the Io–Europa and Europa–Ganymede conjunctions change with the same rate, making triple conjunctions impossible. Such a complicated resonance is called the Laplace resonance. The current Laplace resonance is unable to pump the orbital eccentricity of Ganymede to a higher value. The value of about 0.0013 is probably a remnant from a previous
Stability of the Solar System that keeps the far side of the Moon away from the Earth. Mercury is in a 3:2 spin–orbit resonance. The planets' orbits are chaotic over longer timescales, such that the whole Solar System possesses a Lyapunov time in the range of 2–230 million years. In all cases this means that the position of a planet along its orbit ultimately becomes impossible to predict with any certainty (so, for example, the timing of winter and summer become uncertain), but in some cases the orbits themselves may change dramatically. Such chaos manifests most strongly as changes in eccentricity, with some planets' orbits