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An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters range from small, simple, bowl-shaped depressions to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.
Iapetus is the third-largest natural satellite of Saturn, eleventh-largest in the Solar System, and the largest body in the Solar System known not to be in hydrostatic equilibrium. Discoveries by the Cassini mission in 2007 revealed several unusual features, such as a massive equatorial ridge running three-quarters of the way around the moon.
Hyperion, also known as Saturn VII (7), is a moon of Saturn discovered by William Cranch Bond, his son George Phillips Bond and William Lassell in 1848. It is distinguished by its irregular shape, its chaotic rotation, and its unexplained sponge-like appearance. It was the first non-round moon to be discovered.
Phoebe is an irregular satellite of Saturn with a mean diameter of 213 km (132 mi). It was discovered by William Henry Pickering on March 18, 1899 from photographic plates that had been taken starting on 16 August 1898 at the Boyden Station of the Carmen Alto Observatory near Arequipa, Peru, by DeLisle Stewart. It was the first satellite to be discovered photographically.
The moons of Saturn are numerous and diverse, ranging from tiny moonlets only tens of meters across to enormous Titan, which is larger than the planet Mercury. Saturn has 82 moons with confirmed orbits that are not embedded in its rings – of which only 13 have diameters greater than 50 kilometers – as well as dense rings that contain millions of embedded moonlets and innumerable smaller ring particles. Seven Saturnian moons are large enough to have collapsed into a relaxed, ellipsoidal shape, though only one or two of those, Titan and possibly Rhea, are currently in hydrostatic equilibrium. Particularly notable among Saturn's moons are Titan, the second-largest moon in the Solar System, with a nitrogen-rich Earth-like atmosphere and a landscape featuring dry river networks and hydrocarbon lakes, Enceladus, which emits jets of gas and dust from its south-polar region, and Iapetus, with its contrasting black and white hemispheres.
Cassini Regio is the enigmatic dark area that covers the leading half of Saturn's moon Iapetus. It is named after Giovanni Cassini, the discoverer of Iapetus; 'Regio' is a term used in planetary geology for a large area that is strongly differentiated in colour or albedo from its surroundings. The brighter half of Iapetus is composed of the Roncevaux Terra and the Saragossa Terra.
Roncevaux Terra is the name given to the northern part of the highly reflective side of Saturn's moon Iapetus. The southern half of this side is named Saragossa Terra. The other half of Iapetus, named Cassini Regio, is extremely dark. It is believed that Roncevaux Terra's colour is the underlying colour of Iapetus, while Cassini Regio was formed either by a substance that has covered up the brighter ice of the rest of the moon, or by a residue left from the sublimation of Roncevaux-type water ice. For more details, see the main article on Iapetus.
Several of Saturn's natural satellites have figured prominently in works of science fiction.
Tempe Terra is a heavily cratered highland region in the northern hemisphere of the planet Mars. Located at the northeastern edge of the Tharsis volcanic province, Tempe Terra is notable for its high degree of crustal fracturing and deformation. The region also contains many small shield volcanoes, lava flows, and other volcanic structures.
Turgis is the largest known crater on Saturn's moon Iapetus. It is 580 km in diameter, 40% of the moon's diameter and one of the larger craters in the Solar System. It is named after a Saracen baron, Turgis of Turtelose (Tortosa).
Columbus Crater is a crater in the Terra Sirenum of Mars, located at 29.8° south latitude and 166.1° west longitude. It is 119 km in diameter and was named after Christopher Columbus, Italian explorer (1451–1506). The discovery of sulfates and clay minerals in sediments within Columbus Crater are strong evidence that a lake once existed in the crater. Research with an orbiting near-infrared spectrometer, which reveals the types of minerals present based on the wavelengths of light they absorb, found evidence of layers of both clay and sulfates in Columbus crater. This is exactly what would appear if a large lake had slowly evaporated. Moreover, because some layers contained gypsum, a sulfate which forms in relatively fresh water, life could have formed in the crater.
The Terra Australis Orogen (TAO) was the oceanic southern margin of Gondwana which stretched from South America to Eastern Australia and encompassed South Africa, West Antarctica, New Zealand and Victoria Land in East Antarctica.
Engelier is a 310-mile (500-kilometers) large crater on Saturn's moon Iapetus in Saragossa Terra. It partially obscures the slightly smaller crater Gerin.
Gerin is 445 km wide impact crater on Saturn's moon Iapetus, located on Saragossa Terra. It is partially obscured by the larger crater, Engelier, whose formation has destroyed about half of Gerin. Gerin is located at 45.6°S 233°W
Abisme /æˈbiːm/ is located in Cassini Regio at 37.9°N 267.1°E. Craters Climborin, Clarin, Dapamort, Johun and Valdebron can be found inside Abisme. It was imaged for the first time by the Cassini spacecraft in 2004.
References
- ↑ "Planetary Names: terra, terrae: Saragossa Terra on Iapetus". United States Geological Survey. August 5, 2008. Retrieved August 7, 2015.
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