Changes

Io maintains a three-part [[orbital resonance]] or Laplace resonance with Europa and Ganymede. 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.)

Io maintains a three-part [[orbital resonance]] or Laplace resonance with Europa and Ganymede. 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 origin of the resonance itself is controversial. Peale and Lee, in 2002, presented a model suggesting that this resonance is primordial and thus was part of the Jovian system since its formation.<ref name=Peale>Peale, S. J., and Lee, Man Hoi. "[http://adsabs.harvard.edu/abs/2002Sci...298..593P A Primordial Origin of the Laplace Relation Among the Galilean Satellites]." ''Science'', 298(5593):593-597, October 2002. Accessed February 18, 2008.</ref> Their model, however, derives from the [[nebular hypothesis]] of the formation of the solar system and thus depends on [[uniformitarianism|uniformitarian]] assumptions. Showman and Malhotra suggest a model by which the resonance developed after the solar system had formed.<ref name=Showman/>

The origin of the resonance itself is controversial. Peale and Lee, in 2002, presented a model suggesting that this resonance is primordial and thus was part of the Jovian system since its formation.<ref name=Peale>Peale, S. J., and Lee, Man Hoi. "[http://adsabs.harvard.edu/abs/2002Sci...298..593P A Primordial Origin of the Laplace Relation Among the Galilean Satellites]." ''Science'', 298(5593):593-597, October 2002. Accessed February 18, 2008.</ref> Their model, however, derives from the [[nebular hypothesis]] of the formation of the solar system and thus depends on [[uniformitarianism|uniformitarian]] assumptions. Showman and Malhotra suggest a model by which the resonance developed after the solar system had formed.<ref name=Showman>Showman, Adam P., and Malhotra, Renu. "[http://www.lpl.arizona.edu/~showman/publications/showman-malhotra-1997.pdf Tidal Evolution into the Laplace Resonance and the Resurfacing of Ganymede]." ''Icarus'', 127:93-111, 1997. Accessed February 18, 2008.</ref>

This orbital resonance, together with tidal stresses imposed by Jupiter itself, is widely held to be the most likely cause of Io's volcanism (see below).

This orbital resonance, together with tidal stresses imposed by Jupiter itself, is widely held to be the most likely cause of Io's volcanism (see below).