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〕 1.480 Moons) | surface_area = | volume = (0.066 Earths) (3.3 Moons) | mass = (0.0225 Earths)〔 (1.829 Moons) | density = 〔 | surface_grav = () (0.85 Moons) | escape_velocity = (1.11 Moons) | rotation = Synchronous | axial_tilt = Zero | albedo = 0.22 | magnitude = 8.2〔 to 9.0 | single_temperature = | atmosphere = yes | surface_pressure = () | atmosphere_composition = Variable〔〔 Stratosphere: 98.4% nitrogen (N2), 1.4% methane (CH4), 0.2% hydrogen (H2); Lower troposphere: 95.0% N2, 4.9% CH4 }} Titan (or Saturn VI) is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere, and the only object other than Earth where clear evidence of stable bodies of surface liquid has been found.〔 Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan's diameter is 50% larger than Earth's natural satellite, the Moon, and it is 80% more massive. It is the second-largest moon in the Solar System, after Jupiter's moon Ganymede, and is larger by volume than the smallest planet, Mercury, although only 40% as massive. Discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan was the first known moon of Saturn, and the fifth known satellite of another planet. Titan is primarily composed of water ice and rocky material. Much as with Venus before the Space Age, the dense opaque atmosphere prevented understanding of Titan's surface until new information accumulated when the ''Cassini–Huygens'' mission arrived in 2004, including the discovery of liquid hydrocarbon lakes in Titan's polar regions. The geologically young surface is generally smooth, with few impact craters, although mountains and several possible cryovolcanoes have been found.〔(【引用サイトリンク】publisher=NASA )〕 The atmosphere of Titan is largely nitrogen; minor components lead to the formation of methane–ethane clouds and nitrogen-rich organic smog. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas (probably of liquid methane–ethane), and deltas, and is dominated by seasonal weather patterns as on Earth. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan's methane cycle is analogous to Earth's water cycle, although at a much lower temperature. ==History== Titan was discovered on March 25, 1655 by the Dutch astronomer Christiaan Huygens. Huygens was inspired by Galileo's discovery of Jupiter's four largest moons in 1610 and his improvements in telescope technology. Christiaan, with the help of his brother Constantijn Huygens, Jr., began building telescopes around 1650 and discovered the first observed moon orbiting Saturn with one of the telescopes they built. He named it simply ''Saturni Luna'' (or ''Luna Saturni'', Latin for "Saturn's moon"), publishing in the 1655 tract ''De Saturni Luna Observatio Nova'' (''A New Observation of Saturn's Moon''). After Giovanni Domenico Cassini published his discoveries of four more moons of Saturn between 1673 and 1686, astronomers fell into the habit of referring to these and Titan as Saturn I through V (with Titan then in fourth position). Other early epithets for Titan include "Saturn's ordinary satellite". Titan is officially numbered Saturn VI because after the 1789 discoveries the numbering scheme was frozen to avoid causing any more confusion (Titan having borne the numbers II and IV as well as VI). Numerous small moons have been discovered closer to Saturn since then. The name ''Titan'', and the names of all seven satellites of Saturn then known, came from John Herschel (son of William Herschel, discoverer of Mimas and Enceladus) in his 1847 publication ''Results of Astronomical Observations Made at the Cape of Good Hope''. He suggested the names of the mythological Titans (), brothers and sisters of Cronus, the Greek Saturn. In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Titan (moon)」の詳細全文を読む スポンサード リンク
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