SATURN

       Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter.
       Saturn is a gas giant with an average radius about nine times that of Earth. While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive.

       Saturn's interior is probably composed of a core of iron, nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer. The planet exhibits 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 magnetic field but has a magnetic moment 580 times that of the Earth due to Saturn's larger body radius. Saturn's magnetic field strength is around one-twentieth the strength 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), faster than on Jupiter, but not as fast as those on Neptune.

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

Saturn is classified as a gas giant because the exterior is predominantly composed of gas and it lacks a definite surface, although it may have a solid core. The rotation of the planet causes it to take the shape of an oblate spheroid. Jupiter, Uranus, and Neptune, the other gas giants in the Solar System, are also oblate but to a lesser extent. Saturn is the only planet of the Solar System that is less dense than water—about 30% less.  Jupiter has 318 times the Earth's mass, while Saturn is 95 times the mass of the Earth, Together, Jupiter and Saturn hold 92% of the total planetary mass in the Solar System.

Saturn is termed a gas giant, but it is not entirely gaseous. The planet primarily consists of hydrogen, which becomes a non-ideal liquid when the density is above 0.01 g/cm3. This density is reached at a radius containing 99.9% of Saturn's mass. The temperature, pressure and density inside the planet all rise steadily toward the core, which, in the deeper layers of the planet, cause hydrogen to transition into a metal.

       Standard planetary models suggest that the interior of Saturn is similar to that of Jupiter, having a small rocky core surrounded by hydrogen and helium with trace amounts of various volatiles. This core is similar in composition to the Earth, but more dense. Examination of the gravitational moment of the planet, in combination with physical models of the interior, allowed French astronomers Didier Saumon and Tristan Guillot to place constraints on the mass of the planet's core. In 2004, they estimated that the core must be 9–22 times the mass of the Earth, which corresponds to a diameter of about 25,000 km. This is surrounded by a thicker liquid metallic hydrogen layer, followed by a liquid layer of helium-saturated molecular hydrogen that gradually transitions into gas with increasing altitude. The outermost layer spans 1,000 km and consists of a gaseous atmosphere.

      Saturn has a hot interior, reaching 11,700 °C at the core, and the planet radiates 2.5 times more energy into space than it receives from the Sun.

      The outer atmosphere of Saturn contains 96.3% molecular hydrogen and 3.25% helium. The proportion of helium is significantly deficient compared to the abundance of this element in the Sun. 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.

      Trace amounts of ammonia, acetylene, ethane, propane, phosphine and methane have been detected in Saturn's atmosphere. The upper clouds are composed of ammonia crystals, while the lower level clouds appear to consist of either ammonium hydrosulfide or water. Ultraviolet radiation from the Sun causes methane photolysis in the upper atmosphere, leading to a series of hydrocarbon chemical reactions with the resulting products being carried downward by eddies and diffusion. This photochemical cycle is modulated by Saturn's annual seasonal cycle.

      Saturn is probably best known for the system of planetary rings that makes it visually unique.  The rings extend from 6,630 km to 120,700 km above Saturn's equator, average approximately 20 meters in thickness and are composed of 93% water ice with traces of tholin impurities and 7% amorphous carbon. The particles that make up the rings range in size from specks of dust up to 10 m. While the other gas giants also have ring systems, Saturn's is the largest and most visible. Some ice in the central rings comes from the moon Enceladus's ice volcanoes.