Fifth planet from the Sun, and the largest planet in the solar system. Named after the ruler of the gods in Roman mythology, Jupiter has 1,400 times the volume of Earth, but is only 318 times as massive. The mean density of Jupiter is therefore about one quarter that of Earth, indicating that the giant planet must consist of gas rather than the metals and rocks of which Earth and the other inner planets are composed.
Orbiting the Sun at a mean distance 5.2 times as great as that of Earth, Jupiter makes a complete revolution in 11.9 years. It takes only 9.9 hours to rotate once on its axis. This rapid rotation causes an equatorial bulge that is apparent in telescopic views of the planet. The rotation is not uniform. The banded appearance of Jupiter is due to the presence of strong atmospheric currents, reflecting the different rotation periods at different latitudes. These bands are made more apparent by the pastel colours of the clouds. These colours are also apparent in the famous brownish-red oval called the Great Red Spot. The colours come from traces of compounds formed by ultraviolet light, lightning discharges, and heat. Some of these compounds may be similar to the organic molecules that formed on ancient Earth as a prelude to the origin of life
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