Changes

According to the most currently popular models of this resonance, [[Ganymede]]'s orbit should not be as eccentric as it now is. Others have suggested that an [[asteroid]]al or [[comet]]ary impact has produced this eccentricity, but Showman and Malhotra, in 1997, showed that such an impact cannot account for the observed eccentricity.<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>

According to the most currently popular models of this resonance, [[Ganymede]]'s orbit should not be as eccentric as it now is. Others have suggested that an [[asteroid]]al or [[comet]]ary impact has produced this eccentricity, but Showman and Malhotra, in 1997, showed that such an impact cannot account for the observed eccentricity.<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>

The resonance ''is'' held responsible for the relatively pronounced eccentricity of the innermost satellite, Io--and also for the tremendous tidal reshaping that Io undergoes during its less-than-two-day month. Most scientist hold that the latter phenomenon heats Io and causes its remarkable volcanism.

The resonance ''is'' held responsible for the relatively pronounced eccentricity of the innermost satellite, Io—and also for the tremendous tidal reshaping that Io undergoes during its less-than-two-day month. Most scientist hold that the latter phenomenon heats Io and causes its remarkable volcanism.

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/>

[[Image:Io galileo 19951217 sc 0-002-005.jpg|100px|right]]: ''Main article: [[Io]]''

[[Image:Io galileo 19951217 sc 0-002-005.jpg|100px|right]]: ''Main article: [[Io]]''

'''Io''' is the innermost, the most dense, and in many other ways the most remarkable of the Galilean moons. Since the [[Voyager 1]] and [[Voyager 2]] flybys in 1979 and 1980, Io has been known to be [[volcano|volcanically]] active--the most active body in all the solar system. [[Tidal heating]] is the most popular theory to explain this activity, but even that cannot account completely for the total amount of heat that flows out from Io at all times.

'''Io''' is the innermost, the most dense, and in many other ways the most remarkable of the Galilean moons. Since the [[Voyager 1]] and [[Voyager 2]] flybys in 1979 and 1980, Io has been known to be [[volcano|volcanically]] active—the most active body in all the solar system. [[Tidal heating]] is the most popular theory to explain this activity, but even that cannot account completely for the total amount of heat that flows out from Io at all times.

== Europa ==

== Europa ==

'''Europa''', the second innermost, is also the smallest of the Galileans. It has very few craters, and thus by [[uniformitarianism|uniformitarian]] criteria it is considered "young." The brittle ice sheet that overlays it has fueled speculation as to whether a much thicker ice sheet, or a liquid-water ocean, lies deep to it. This in turn has fueled speculation, both in the scientific community and in [[science fiction]], as to whether Europa harbors life.

'''Europa''', the second innermost, is also the smallest of the Galileans. It has very few craters, and thus by [[uniformitarianism|uniformitarian]] criteria it is considered "young." The brittle ice sheet that overlays it has fueled speculation as to whether a much thicker ice sheet, or a liquid-water ocean, lies deep to it. This in turn has fueled speculation, both in the scientific community and in [[science fiction]], as to whether Europa harbors life.

The [[Galileo project|Galileo]] spacecraft developed evidence in favor of the proposition that Europa has a sub-crust saltwater ocean under a very thin rock-and-ice layer. In order to prevent the spacecraft from crashing into Europa, rupturing the crust, and contaminating Europa's oceans with earthly [[microbe]]s, Galileo's mission controllers steered Galileo into a crash dive into Jupiter in September of 2003.<ref name=rense/><ref name=Macey/> However, the exploration of Europa with a submersible probe, to be delivered by an ice-penetrating missile, is under active consideration.

The [[Galileo project|Galileo]] spacecraft developed evidence in favor of the proposition that Europa has a sub-crust saltwater ocean under a very thin rock-and-ice layer. In order to prevent the spacecraft from crashing into Europa, rupturing the crust, and contaminating Europa's oceans with earthly [[microbe]]s, Galileo's mission controllers steered Galileo into a crash dive into Jupiter in September 2003.<ref name=rense/><ref name=Macey/> However, the exploration of Europa with a submersible probe, to be delivered by an ice-penetrating missile, is under active consideration.

== Ganymede ==

== Ganymede ==

[[Image:Ganymede2 galileo big.jpg|100px|right]]: ''Main article: [[Ganymede]]''

[[Image:Ganymede2 galileo big.jpg|100px|right]]: ''Main article: [[Ganymede]]''

'''Ganymede''' is the largest moon not only of Jupiter but in all the solar system--larger than [[Mercury]] so that in theory it could be a true [[planet]] if it orbited the [[Sun]]. In sharp contrast to Io and Europa, Ganymede is very heavily cratered and is therefore considered "old." Ganymede has its own independent magnetic field, and a quite strong one. Like Europa, it has a saltwater ocean, but under a much thicker crust than that of Europa.

'''Ganymede''' is the largest moon not only of Jupiter but in all the solar system—larger than [[Mercury]] so that in theory it could be a true [[planet]] if it orbited the [[Sun]]. In sharp contrast to Io and Europa, Ganymede is very heavily cratered and is therefore considered "old." Ganymede has its own independent magnetic field, and a quite strong one. Like Europa, it has a saltwater ocean, but under a much thicker crust than that of Europa.

== Callisto ==

== Callisto ==

{{Solarsystem}}

{{Solarsystem}}

[[category:moons]]

[[Category:Moons]]