Saturn, the only planet of the Solar System that is less dense than water

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.

 

What is Saturn?

It is a gas giant with an average radius about nine times that of Earth. Although it has only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive. This planet is named after the Roman god of agriculture; its astronomical symbol (♄) represents the god’s sickle.

Saturn’s interior is probably composed of a core of iron–nickel and rock (silicon and oxygen compounds). This core is surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium, and finally outside the Frenkel line a gaseous outer layer. Saturn has a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn’s planetary magnetic field, which is weaker than Earth’s, but has a magnetic moment 580 times that of Earth due to Saturn’s larger size. Saturn’s magnetic field strength is around one-twentieth of Jupiter’s. The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h (500 m/s), higher than on Jupiter, but not as high as those on Neptune.

It has a prominent ring system that consists of nine continuous main rings and three discontinuous arcs and that is composed mostly of ice particles with a smaller amount of rocky debris and dust. 62 moons are known to orbit Saturn, of which fifty-three are officially named. This does not include the hundreds of moonlets comprising the rings. Titan, Saturn’s largest moon, and the second-largest in the Solar System, is larger than the planet Mercury, although less massive, and is the only moon in the Solar System to have a substantial atmosphere.

Atmosphere

The outer atmosphere of Saturn contains 96.3% molecular hydrogen and 3.25% helium by volume. The proportion of helium is significantly deficient compared to the abundance of this element in the Sun. The quantity of elements heavier than helium (metallicity) is not known precisely, but the proportions are assumed to match the primordial abundances from the formation of the Solar System. The total mass of these heavier elements is estimated to be 19–31 times the mass of the Earth, with a significant fraction located in Saturn’s core region.

Image: NASA / JPL / SSI
Text: Wikipedia contributors. “Saturn.” Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 1 Aug. 2017. Web. 8 Aug. 2017.

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