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Haystack Vallis
Haystack Catena (Haystack Vallis until March 2013) is a catena at 4.7° N, 46.2° W on Mercury. It superficially resembles a graben but is a chain of overlapping secondary craters. It was named after Haystack Observatory
Haystack Observatory is a multidisciplinary radio science center, ionospheric observatory, and astronomical microwave observatory owned by Massachusetts Institute of Technology (MIT). It is located in Westford, Massachusetts (US), approximate ... .
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Haystack Observatory
Haystack Observatory is a multidisciplinary radio science center, ionospheric observatory, and astronomical microwave observatory owned by Massachusetts Institute of Technology (MIT). It is located in Westford, Massachusetts (US), approximately northwest of Boston. Haystack was initially built by MIT's Lincoln Laboratory for the United States Air Force and was known as Haystack Microwave Research Facility. Construction began in 1960, and the antenna began operating in 1964. In 1970 the facility was transferred to MIT, which then formed the Northeast Radio Observatory Corporation (NEROC) with a number of other universities to operate the site as the Haystack Observatory. , a total of nine institutions participated in NEROC. The Haystack Observatory site is also the location of the Millstone Hill Geospace Facility, an atmospheric sciences research center. Lincoln Laboratory continues to use the site, which it calls the Lincoln Space Surveillance Complex (LSSC). The George R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crater Chain
A crater chain is a line of craters along the surface of an astronomical body. The descriptor term for crater chains is catena , plural catenae (Latin for "chain"), as specified by the International Astronomical Union's rules on planetary nomenclature. Many examples of such chains are thought to have been formed by the impact of a body that was broken up by tidal forces into a string of smaller objects following roughly the same orbit. An example of such a tidally disrupted body that was observed prior to its impact on Jupiter is Comet Shoemaker-Levy 9. During the Voyager observations of the Jupiter system, planetary scientists identified 13 crater chains on Callisto and three on Ganymede (except those formed by secondary craters). Later some of these chains turned out to be secondary or tectonic features, but some other chains were discovered. As of 1996, 8 primary chains on Callisto and 3 on Ganymede were confirmed. Other cases, such as many of those on Mars, represent cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury (planet)
Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman god ' ( Mercury), god of commerce, messenger of the gods, and mediator between gods and mortals, corresponding to the Greek god Hermes (). Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, and its apparent distance from the Sun as viewed from Earth never exceeds 28°. This proximity to the Sun means the planet can only be seen near the western horizon after sunset or the eastern horizon before sunrise, usually in twilight. At this time, it may appear as a bright star-like object, but is more difficult to observe than Venus. From Earth, the planet telescopically displays the complete range of phases, similar to Venus and the Moon, which recurs over its synodic period of approximately 116 days. The synodic proximity of Mercury to Earth makes Mercury ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graben
In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic context by Eduard Suess in 1883. The plural form is either ''graben'' or ''grabens''. Formation A graben is a valley with a distinct escarpment on each side caused by the displacement of a block of land downward. Graben often occur side by side with horsts. Horst and graben structures indicate tensional forces and crustal stretching. Graben are produced from parallel normal faults, where the displacement of the hanging wall is downward, while that of the footwall is upward. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between graben; the bounding faults of a horst typically dip away from the center line of the horst. Single or multiple graben can produce a rift valley. Ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Crater
Secondary craters are impact craters formed by the ejecta that was thrown out of a larger crater. They sometimes form radial crater chains. In addition, secondary craters are often seen as clusters or rays surrounding primary craters. The study of secondary craters exploded around the mid-twentieth century when researchers studying surface craters to predict the age of planetary bodies realized that secondary craters contaminated the crater statistics of a body's crater count. Formation When a velocity-driven extraterrestrial object impacts a relatively stationary body, an impact crater forms. Initial crater(s) to form from the collision are known as primary craters or impact craters. Material expelled from primary craters may form secondary craters (secondaries) under a few conditions: # Primary craters must already be present. # The gravitational acceleration of the extraterrestrial body must be great enough to drive the ejected material back toward the surface. # The velocity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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