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== Orbital and rotational characteristics ==
== Orbital and rotational characteristics ==
[[Image:Galilean moon Laplace resonance animation.gif|thumb|150 px|left|Orbital resonance of Io, Europa, and Ganymede]]Ganymede is seventh in order of all of Jupiter's moons, and orbits Jupiter at a semi-major axis of 1,070,400 km. Its orbit is very slightly eccentric and slightly inclined to Jupiter's equator. Although Ganymede is in tidal lock (thus keeping the same face toward Jupiter as it revolves), its axis does tend to tilt very slightly from the true perpendicular from time to time on account of gravitational perturbations.<ref name=Icarus/>
[[Image:Galilean moon Laplace resonance animation.gif|thumb|150 px|left|Orbital resonance of Io, Europa, and Ganymede]]Ganymede is seventh in order of all of Jupiter's moons, and orbits Jupiter at a semi-major axis of 1,070,400 km. Its orbit is very slightly eccentric and slightly inclined to Jupiter's equator. Although Ganymede is in [[tidal lock]] (thus keeping the same face toward Jupiter as it revolves), its axis does tend to tilt very slightly from the true perpendicular from time to time on account of gravitational perturbations.<ref name=Icarus/>
The most striking feature of Ganymede's orbit is its three-part [[orbital resonance]] or Laplace resonance with the two inner moons Io and Europa. These three satellites complete their orbits around Jupiter in the ratio 1:2:4. They also conjoin with one another at their apsides, in a mutually self-correcting manner that allows the resonance to persist. (Most such resonances are unstable and end with one or all bodies changing their orbits.)
The most striking feature of Ganymede's orbit is its three-part [[orbital resonance]] or Laplace resonance with the two inner moons Io and Europa. These three satellites complete their orbits around Jupiter in the ratio 1:2:4. They also conjoin with one another at their apsides, in a mutually self-correcting manner that allows the resonance to persist. (Most such resonances are unstable and end with one or all bodies changing their orbits.)