| 单词 | mimas | |||||
| 释义 | MimasenUKMi·masM0306550 (mī′măs, mē′-)Mimas(ˈmaɪməs; -mæs)MimasenUKMimas(mī`măs), in astronomy, one of the named moons, or natural satellites, of SaturnSaturn,in astronomy, 6th planet from the sun. Astronomical and Physical Characteristics of Saturn Saturn's orbit lies between those of Jupiter and Uranus; its mean distance from the sun is c.886 million mi (1. ..... Click the link for more information. . Also known as Saturn I (or S1), Mimas is 244 mi (392 km) in diameter, orbits Saturn at a mean distance of 115,275 mi (185,520 km), and has equal orbital and rotational periods of 0.942 earth days. Mimas was discovered by the English astronomer Sir William HerschelHerschel , family of distinguished English astronomers. Sir William Herschel Sir William Herschel, 1738–1822, born Friedrich Wilhelm Herschel, was a great pioneer in astronomy. ..... Click the link for more information. in 1789. Its low density (1.17) indicates that it is composed mostly of water ice with only a small amount of rocky material. The surface is saturated with impact craters. The largest by far—called Herschel—has a diameter of more than 80 mi (130 km), almost a third the diameter of the entire satellite; the walls of this crater are about 3 mi (5 km) high, parts of the floor are about 6 mi (10 km) deep, and the central peak towers almost 4 mi (6 km) above the floor of the crater. Fractures can be seen on the opposite side of Mimas that may have resulted from the same impact. Mimas forms a satellite pair with TethysTethys , in astronomy, one of the named moons, or natural satellites, of Saturn. Also known as Saturn III (or S3), Tethys is 659 mi (1060 km) in diameter, orbits Saturn at a mean distance of 183,093 mi (294,660 km), and has equal orbital and rotational periods of 1. ..... Click the link for more information. ; that is, the two moons interact gravitationally. Mimas(mÿ -mas) A satellite of Saturn, discovered in 1789 by William Herschel. It has a diameter of only 390 km and a density of 1.17 g cm–3. The most striking feature is the crater Herschel, 130 km in diameter and nearly centered on the leading hemisphere. The walls rise on average to a height of 5 km above the floor. In the center of the crater is an enormous peak 20 × 30 km at its base and rising to 6 km. The diameter of the crater is a third of Mimas itself, and is probably close to the maximum size of impact crater that a body can sustain without being broken up. All other craters on the surface are small, being less than 50 km in diameter. There are valleys too on the surface, which is scored by grooves. The surface of the satellite is icy and there is every reason to suppose that the ice makes up much of the entire body, which now bears the scars of past bombardments. See also Table 2, backmatter.Mimas[′mē·mäs]MIMAS
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