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Jupiter is a gas giant planet and the largest in the Solar System, with a mass about 2 1/2 times the combined mass of all the other planets in the Solar System. Only the outer layers of its atmosphere have been studied; below the whirling cacophony of mainly ammonia clouds it is thought to be largely molecular hydrogen surrounding a metallic hydrogen core. As a gas giant, Jupiter has no solid surface. It is believed that the immense pressure results in the atmosphere gradually condensing into a liquid, and eventually, a solid core. Because of its great mass, Jupiter is host to a small ring system and an extensive system of moons. Jupiter possesses its own magnetic field which results in aurorae near the poles. Jupiter's massive gravitational pull also results in tidal action on several of its moons, causing geothermal activity on its four largest moons, Io, Callisto, Ganymede, and Europa.
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium; it may also have a rocky core of heavier elements. Because of its rapid rotation, Jupiter's shape is that of an oblate spheroid (it possesses a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope.
As a gas giant, Jupiter has no climate in the traditional sense. Conditions in the studied part of Jupiter--its upper atmosphere--are highly inhospitable. Jupiter's inner heat far exceeds the heat it receives from the sun and radiates out from the center of the planet, clashing violently with the icy cold of space and causing immense, violent, and long-lived cyclones--the Great Red Spot, the largest, is larger than Earth and has been observed since Galileo--and also results in bands of wind that race endlessly around the planet.
Ganymede - the seventh and largest moon of Jupiter, as well as the largest moon in the Solar System. It was terraformed in the twenty-first century by heating its original thick layer of ice to reveal a great seawater ocean underneath. With very little natural landforms, Ganymede is primarily used in the commercial fishing industry to harvest such animals as the Ganymede Rock Lobster and the endangered Ganymede Sea Rat.