Changes

== Orbital characteristics ==

== Orbital characteristics ==

Saturn's orbit is about 3.4 times as eccentric as Earth's orbit. Saturn keeps an average orbital distance of 1,433,530,000 km from the sun, a distance close to that predicted by the [[Titius-Bode Law]].<ref name=saturnfact/> Saturn's orbit is slightly inclined to the ecliptic, with the result that the [[Earth]] passes from one side to the other of Saturn's ring plane every so often.<ref name=Arnett/> Saturn's sidereal period is about 29.4 [[Earth]] years. Its ''synodic'' period is 378.09 days.

Saturn's orbit is about 3.4 times as eccentric as Earth's orbit. Saturn keeps an average orbital distance of 1,433,530,000&nbsp;km from the sun, a distance close to that predicted by the [[Titius-Bode Law]].<ref name=saturnfact/> Saturn's orbit is slightly inclined to the ecliptic, with the result that the [[Earth]] passes from one side to the other of Saturn's ring plane every so often.<ref name=Arnett/> Saturn's sidereal period is about 29.4 [[Earth]] years. Its ''synodic'' period is 378.09 days.

== Physical characteristics ==

== Physical characteristics ==

Saturn's volumetric mean radius is 58,232 km. Remarkably, Saturn is less dense than [[water]]. Its chief constituent is molecular [[hydrogen]], followed by [[helium]], [[methane]], [[ammonia]], [[hydrogen deuteride]], and [[ethane]]. Aerosols of ammonia ice, water ice, and [[ammonia hydrosulfide]] complete Saturn's composition.

Saturn's volumetric mean radius is 58,232&nbsp;km. Remarkably, Saturn is less dense than [[water]]. Its chief constituent is molecular [[hydrogen]], followed by [[helium]], [[methane]], [[ammonia]], [[hydrogen deuteride]], and [[ethane]]. Aerosols of ammonia ice, water ice, and [[ammonia hydrosulfide]] complete Saturn's composition.

Saturn has high winds, which blow easterly at 500 m/s at the equator.<ref name=Hamilton>Hamilton, Calvin J. "[http://www.solarviews.com/eng/saturn.htm Entry for Saturn]." ''Views of the Solar System'', 1997-2005. Accessed May 19, 2008.</ref>

Saturn has high winds, which blow easterly at 500&nbsp;m/s at the equator.<ref name=Hamilton>Hamilton, Calvin J. "[http://www.solarviews.com/eng/saturn.htm Entry for Saturn]." ''Views of the Solar System'', 1997-2005. Accessed May 19, 2008.</ref>

== Magnetosphere ==

== Magnetosphere ==

Saturn’s ring system is the brightest in all the solar system, with an albedo varying from 0.2 to 0.6, often brighter than the planet itself.<ref name=Arnett/>

Saturn’s ring system is the brightest in all the solar system, with an albedo varying from 0.2 to 0.6, often brighter than the planet itself.<ref name=Arnett/>

The rings have radii varying from 60,268 km to 483,000 km. Saturn's rings divide into seven portions, designated D, C, B, A, F, G, and E from inner to outer. A wide gap called the Cassini Division separates the B and A rings, and the A rings themselves have two gaps, called the Encke and Keeler gaps.<ref name=saturnringfact>Williams, David R. "[http://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html Saturnian Rings Fact Sheet]." [[National Aeronautics and Space Administration|NASA]], September 18, 2006. Accessed May 19, 2008.</ref>

The rings have radii varying from 60,268&nbsp;km to 483,000&nbsp;km. Saturn's rings divide into seven portions, designated D, C, B, A, F, G, and E from inner to outer. A wide gap called the Cassini Division separates the B and A rings, and the A rings themselves have two gaps, called the Encke and Keeler gaps.<ref name=saturnringfact>Williams, David R. "[http://nssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html Saturnian Rings Fact Sheet]." [[National Aeronautics and Space Administration|NASA]], September 18, 2006. Accessed May 19, 2008.</ref>

The two Voyager spacecraft sent back cinematic images that showed that the rings were spoked, and that the spokes persist, especially in the B ring system.<ref name=Arnett/><ref name=Hamilton/> Current theories suggest that the spokes result from magnetic interaction, because the rings all lie well within Saturn's magnetosphere. Furthermore, the F ring appears to be braided, a phenomenon that remains unexplained today.<ref name=Arnett/>

The two Voyager spacecraft sent back cinematic images that showed that the rings were spoked, and that the spokes persist, especially in the B ring system.<ref name=Arnett/><ref name=Hamilton/> Current theories suggest that the spokes result from magnetic interaction, because the rings all lie well within Saturn's magnetosphere. Furthermore, the F ring appears to be braided, a phenomenon that remains unexplained today.<ref name=Arnett/>

Many of the innermost moons of Saturn orbit close to the rings, especially the F and E rings, and serve to regularize their structure, a phenomenon called "shepherding."<ref name=Hamilton/>

Many of the innermost moons of Saturn orbit close to the rings, especially the F and E rings, and serve to regularize their structure, a phenomenon called "shepherding."<ref name=Hamilton/>

As of October 8, 2009, scientists have discovered another massive ring system that could not previously be seen<ref>http://www.timesonline.co.uk/tol/news/science/space/article6864286.ece</ref>.

As of October 8, 2009, scientists have discovered another massive ring system that could not previously be seen.<ref>http://www.timesonline.co.uk/tol/news/science/space/article6864286.ece</ref>

== Problems for uniformitarian theories ==

== Problems for uniformitarian theories ==

The origin of Saturn's rings remains a mystery<ref name=Arnett/><ref name=Hamilton/>, and a troublesome one. The rings are not stable and hence could not have persisted for the whole of the assumed [[deep time]] age of the solar system.<ref name=Arnett/> [[Uniformitarianism|Uniformitarians]] admit that Saturn's rings could not be older than about 100 million years.<ref name=Arnett/> They therefore propose that Saturn's rings formed from the disintegration of one or more moons, perhaps following a collision with a [[comet]].<ref name=Arnett/><ref name=Hamilton/> However, Wing-Huan Ip at the Max Planck Institute calculated that a comet-moon collision would not be sufficiently likely to occur in less time than 30 billion years. This is more than twice the age of the universe calculated from the [[Hubble Constant]].<ref name=Harris>Harris, David M. "[http://www.answersingenesis.org/creation/v12/i4/saturn.asp How Old are Saturn's Rings]?" ''Creation'', 12(4):40–41. September 1990. Accessed May 18, 2008.</ref>

The origin of Saturn's rings remains a mystery,<ref name=Arnett/><ref name=Hamilton/> and a troublesome one. The rings are not stable and hence could not have persisted for the whole of the assumed [[deep time]] age of the solar system.<ref name=Arnett/> [[Uniformitarianism|Uniformitarians]] admit that Saturn's rings could not be older than about 100 million years.<ref name=Arnett/> They therefore propose that Saturn's rings formed from the disintegration of one or more moons, perhaps following a collision with a [[comet]].<ref name=Arnett/><ref name=Hamilton/> However, Wing-Huan Ip at the Max Planck Institute calculated that a comet-moon collision would not be sufficiently likely to occur in less time than 30 billion years. This is more than twice the age of the universe calculated from the [[Hubble Constant]].<ref name=Harris>Harris, David M. "[http://www.answersingenesis.org/creation/v12/i4/saturn.asp How Old are Saturn's Rings]?" ''Creation'', 12(4):40–41. September 1990. Accessed May 18, 2008.</ref>

== Observation and Exploration ==

== Observation and Exploration ==