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Mariner 2008 Automobile pdf manual download. ![]() Mercury (planet) - Wikipedia. Mercury Mercury in enhanced color, imaged by MESSENGER (2. Designations. Pronunciation ( listen)Adjectives. Mercurian. Its orbital period around the Sun of 8. Solar System. It is named after the Roman deity. Mercury, the messenger to the gods. Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, so it can only be seen visually in the morning or the evening sky, and never exceeds 2. Also, like Venus and the Moon, the planet displays the complete range of phases as it moves around its orbit relative to Earth. Seen from Earth, this cycle of phases reoccurs approximately every 1. Although Mercury can appear as a bright star- like object when viewed from Earth, its proximity to the Sun often makes it more difficult to see than Venus. Mercury is tidally or gravitationally locked with the Sun in a 3: 2 resonance. As seen relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun. An observer on Mercury would therefore see only one day every two years. Mercury's axis has the smallest tilt of any of the Solar System's planets (about 1. Mercury's surface appears heavily cratered and is similar in appearance to the Moon's, indicating that it has been geologically inactive for billions of years. Having almost no atmosphere to retain heat, it has surface temperatures that vary diurnally more than on any other planet in the Solar System, ranging from 1. K (. The polar regions are constantly below 1. K (. The planet has no known natural satellites. Two spacecraft have visited Mercury: Mariner 1. MESSENGER, launched in 2. Mercury over 4,0. April 3. 0, 2. 01. It is the smallest planet in the Solar System, with an equatorialradius of 2,4. Mercury consists of approximately 7. Although Earth's high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller and its inner regions are not as compressed. Therefore, for it to have such a high density, its core must be large and rich in iron. Research published in 2. Mercury has a molten core. It is thought that these were formed as Mercury's core and mantle cooled and contracted at a time when the crust had already solidified. The most widely accepted theory is that Mercury originally had a metal–silicate ratio similar to common chondrite meteorites, thought to be typical of the Solar System's rocky matter, and a mass approximately 2. It would initially have had twice its present mass, but as the protosun contracted, temperatures near Mercury could have been between 2,5. K and possibly even as high as 1. K. The findings would seem to favor the third hypothesis; however, further analysis of the data is needed. Because knowledge of Mercury's geology had been based only on the 1. Mariner 1. 0 flyby and terrestrial observations, it is the least understood of the terrestrial planets. For example, an unusual crater with radiating troughs has been discovered that scientists called . Mercury has dorsa (also called . Names coming from people are limited to the deceased. Craters are named for artists, musicians, painters, and authors who have made outstanding or fundamental contributions to their field. Ridges, or dorsa, are named for scientists who have contributed to the study of Mercury. Depressions or fossae are named for works of architecture. Montes are named for the word . Plains or planitiae are named for Mercury in various languages. Escarpments or rup. Valleys or valles are named for radio telescope facilities. Mercury's surface is more heterogeneous than either Mars's or the Moon's, both of which contain significant stretches of similar geology, such as maria and plateaus. They appear in all states of degradation, from relatively fresh rayed craters to highly degraded crater remnants. Mercurian craters differ subtly from lunar craters in that the area blanketed by their ejecta is much smaller, a consequence of Mercury's stronger surface gravity. At the antipode of the Caloris Basin is a large region of unusual, hilly terrain known as the . One hypothesis for its origin is that shock waves generated during the Caloris impact traveled around Mercury, converging at the basin's antipode (1. The resulting high stresses fractured the surface. A notable basin is the 4. Tolstoj Basin that has an ejecta blanket extending up to 5. Beethoven Basin has a similar- sized ejecta blanket and a 6. These inter- crater plains appear to have obliterated many earlier craters, and show a general paucity of smaller craters below about 3. Notably, they fill a wide ring surrounding the Caloris Basin. Unlike lunar maria, the smooth plains of Mercury have the same albedo as the older inter- crater plains. Despite a lack of unequivocally volcanic characteristics, the localisation and rounded, lobate shape of these plains strongly support volcanic origins. It is not clear whether they are volcanic lavas induced by the impact, or a large sheet of impact melt. As Mercury's interior cooled, it contracted and its surface began to deform, creating wrinkle ridges and lobate scarps associated with thrust faults. The scarps can reach lengths of 1. It is thus a . It never rises above 1. K at the poles. The subsolar point reaches about 7. K during perihelion (0. The floors of deep craters at the poles are never exposed to direct sunlight, and temperatures there remain below 1. K; far lower than the global average. Hydrogen atoms and helium atoms probably come from the solar wind, diffusing into Mercury's magnetosphere before later escaping back into space. Radioactive decay of elements within Mercury's crust is another source of helium, as well as sodium and potassium. MESSENGER found high proportions of calcium, helium, hydroxide, magnesium, oxygen, potassium, silicon and sodium. Water vapor is present, released by a combination of processes such as: comets striking its surface, sputtering creating water out of hydrogen from the solar wind and oxygen from rock, and sublimation from reservoirs of water ice in the permanently shadowed polar craters. The detection of high amounts of water- related ions like O+, OH. This would indicate an interaction between the magnetosphere and the planet's surface. MESSENGER's principal investigator Sean Solomon is quoted in The New York Times estimating the volume of the ice to be large enough to . According to measurements taken by Mariner 1. Earth's. The magnetic- field strength at Mercury's equator is about 3. T. Particularly strong tidal effects caused by the planet's high orbital eccentricity would serve to keep the core in the liquid state necessary for this dynamo effect. The planet's magnetosphere, though small enough to fit within Earth. This contributes to the space weathering of the planet's surface. Bursts of energetic particles in the planet's magnetotail indicate a dynamic quality to the planet's magnetosphere. The spacecraft encountered magnetic . These twisted magnetic flux tubes, technically known as flux transfer events, form open windows in the planet's magnetic shield through which the solar wind may enter and directly impact Mercury's surface via magnetic reconnection. The MESSENGER observations showed the reconnection rate is ten times higher at Mercury, but its proximity to the Sun only accounts for about a third of the reconnection rate observed by MESSENGER. Dates refer to 2. Animation of Mercury's and Earth's revolution around the Sun. Mercury has the most eccentric orbit of all the planets; its eccentricity is 0. Sun ranging from 4. It takes 8. 7. 9. Earth days to complete an orbit. The diagram on the right illustrates the effects of the eccentricity, showing Mercury's orbit overlaid with a circular orbit having the same semi- major axis. Mercury's higher velocity when it is near perihelion is clear from the greater distance it covers in each 5- day interval. In the diagram the varying distance of Mercury to the Sun is represented by the size of the planet, which is inversely proportional to Mercury's distance from the Sun. This varying distance to the Sun leads to Mercury's surface being flexed by tidal bulges raised by the Sun that are about 1. Moon's on Earth. As a result, transits of Mercury across the face of the Sun can only occur when the planet is crossing the plane of the ecliptic at the time it lies between Earth and the Sun. This occurs about every seven years on average. This means that to an observer at Mercury's poles, the center of the Sun never rises more than 2. This is because approximately four Earth days before perihelion, Mercury's angular orbital velocity equals its angular rotational velocity so that the Sun's apparent motion ceases; closer to perihelion, Mercury's angular orbital velocity then exceeds the angular rotational velocity. Thus, to a hypothetical observer on Mercury, the Sun appears to move in a retrograde direction. Four Earth days after perihelion, the Sun's normal apparent motion resumes. In the other alternate Mercurian years, the same thing happens at the other of these two points. The amplitude of the retrograde motion is small, so the overall effect is that, for two or three weeks, the Sun is almost stationary overhead, and is at its most brilliant because Mercury is at perihelion, its closest to the Sun. This prolonged exposure to the Sun at its brightest makes these two points the hottest places on Mercury. Conversely, there are two other points on the equator, 9. Sun passes overhead only when the planet is at aphelion in alternate years, when the apparent motion of the Sun in Mercury's sky is relatively rapid. These points, which are the ones on the equator where the apparent retrograde motion of the Sun happens when it is crossing the horizon as described in the preceding paragraph, receive much less solar heat than the first ones described above. Mercury attains inferior conjunction (nearest approach to Earth) every 1. Earth days on average. Mercury can come as near as 8. Earth, and that is slowly declining: The next approach to within 8.
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