Diameter: 12,100 km. It is about 1040km smaller in diameter than Earth
 Temperature: Ranges from 900F+/- 50F (about 500°C +/- 32°C) at the surface
 Distance from Earth: At its closest, Venus is 41,840,000 km away
 Atmosphere: Carbon dioxide (95%), nitrogen, sulfuric acid, and traces of other elements
 Surface: A rocky, dusty, waterless expanse of mountains, canyons, and plains, with a 200-mile river of hardened lava
 Rotation of its axis: 243 Earth days (1 Venusian Day)
 Rotation around the Sun: 225 Earth days
 Magnetic Field: week

Missions to Venus:
USSR - Sputnik 7               -        February 4, 1961               -        Impact (attempted)
USSR - Venera 1                -          February 12, 1961           -        Flyby (contact lost)
USA   - Mariner 1               -          July 22, 1962                   -        Flyby (launch failure)
USSR - Sputnik 19              -          August 25, 1962              -        Flyby (attempted)
USA   - Mariner 2                -          August 27, 1962             -        Flyby
USSR - Sputnik 20              -          September 1, 1962          -        Flyby (attempted)
USSR - Sputnik 21              -          September 12, 1962        -       Flyby (attempted)
USSR - Cosmos 21             -          November 11, 1963        -        Attempted Venera test flight?
USSR - Venera 1964A        -        February 19, 1964            -        Flyby (launch failure)
USSR - Venera 1964B        -         March 1, 1964                 -        Flyby (launch failure)
USSR - Cosmos 27             -          March 27, 1964              -        Flyby (attempted)
USSR - Zond 1                    -          April 2, 1964                  -        Flyby (contact lost)
USSR - Venera 2                 -          November 12, 1965       -        Flyby (contact lost)
USSR - Venera 3                 -          November 16, 1965       -        Lander (contact lost)
USSR - Cosmos 96              -          November 23, 1965       -        Lander (attempted?)
USSR - Venera 1965A         -          November 23, 1965       -        Flyby (launch failure)
USSR - Venera 4                  -          June 12, 1967                -         Probe
USA   - Mariner 5                 -          June 14, 1967                -         Flyby
USSR - Cosmos 167             -          June 17, 1967               -         Probe (attempted)
USSR - Venera 5                   -          January 5, 1969            -         Probe
USSR - Venera 6                   -          January 10, 1969           -         Probe
USSR - Venera 7                   -          August 17, 1970           -         Lander
USSR - Cosmos 359             -          August 22, 1970           -         Probe (attempted)
USSR - Venera 8                  -          March 27, 1972            -         Probe
USSR - Cosmos 482            -          March 31, 1972            -         Probe (attempted)
USA   - Mariner 10              -         November 4, 1973          -         Flyby Mercury flyby
USSR - Venera 9                 -         June 8, 1975                   -         Orbiter and lander
USSR - Venera 10               -          June 14, 1975                -         Orbiter and lander
USA   - Pioneer Venus 1      -          May 20, 1978                -          Orbiter
USA   - Pioneer Venus 2      -          August 8, 1978              -          Probes
USSR - Venera 11               -          September 9, 1978         -         Flyby bus and lander
USSR - Venera 12               -          September 14, 1978       -        Flyby bus and lander
USSR - Venera 13               -         October 30, 1981            -          Flyby bus and lander
USSR - Venera 14               -          November 4, 1981          -         Flyby bus and lander
USSR - Venera 15               -          June 2, 1983                   -          Orbiter
USSR - Venera 16               -          June 7, 1983                   -          Orbiter
USSR - Vega 1                    -          December 15, 1984       -          Lander and balloon Comet Halley flyby
USSR - Vega 2                    -          December 21, 1984       -        Lander and balloon Comet Halley flyby
USA   - Magellan                 -          May 4, 1989                  -          Orbiter
USA   - Galileo                    -          October 18, 1989          -          Flyby Jupiter orbiter/probe
USA   - Cassini                    -          October 15, 1997          -          Flyby Saturn orbiter
USA   - MESSENGER        -          August 3, 2004               -          Flyby (x2) Mercury orbiter
ESA    - Venus Express         -         November 9, 2005         -          Orbiter
JPN    - Akatsuki                 -          December 7, 2010       - Orbiter (attempted) Possible reattempt in 2016
JPN   -  BepiColombo         -          July 2014                     -   Flyby (x2, Planned) Planned Mercury orbiter

Venus in history:

Because Venus is the brightest object in the sky, this planet is known since prehistoric times and as such has gained an entrenched position in human culture. In Sumerian times Venus was named Inanna (Babylonian Ishtar) the goddess of love.

In Ancient Egypt was believed that Venus is two separate bodies named the morning star (Tioumoutiri) and the evening star (Ouaiti). Likewise, believing Venus to be two bodies, the Ancient Greeks called the the morning star Phosphorus, the "Bringer of Light" or Eosphoros the "Bringer of Dawn" and the evening star by the name of Hesperos "star of the evening". By Hellenistic times, the ancient Greeks realized the two were the same planet and named it after the goddess of love, Aphrodite. In latin Hesperos would be translated as Vesper and Phosphoros as Lucifer ("Light Bearer"), a poetic term later used to refer to the fallen angel cast out of heaven.
Romans as other civilizations have named the planet Venus after their goddess of love (Venus). In Persian mythology, the planet correspods to the goddess Anahita. In Some parts of Pahlavi literature whit Aredvi Sura and Anahita two separate entities, the first one is a personification of the mythical river and the latter as a goddess of fertility.

Venus was important to the Maya civilization, who developed a religious calendar based in part upon its motions, and held the motions of Venus to determine the propitious time for important events. The named it Noh Ek', in translation "the Great Star" and Xux Ek' "the Wasp Star". The Maya were aware of the planet's synodic period (a synodic day is the period of time it takes for a planet to rotate once in relation to the body it is orbiting) and could commute it to within a hundredth part of a day.

Venus is also important in many Australian aboriginal cultures, such as that of the Yolngu people in Northern Australia. The Yolngu gather after sunset to await the rising of Venus, which they call Barnumbirr. As she approaches, in the early hours before dawn, she draws behind her a rope of light attached to the Earth, and along this rope, with the aid of a richly decorated "Morning Star Pole", the people are able to communicate with their dead loved ones, showing that they still love and remember them. Barnumbirr is also an important creator-spirit in the Dreaming, and "sang" much of the country into life.

Venus plays a prominent role in Pawnee mythology. The Pawnee, a North American native tribe, until as late as 1838, practiced a morning star ritual in which a girl was sacrificed to the morning star.

Shukra is the Sanskrit name for Venus

In western astrology, derived from its historical connotation with goddesses of femininity and love, Venus is held to influence desire and sexual fertility. In Indian Vedic astrology, Venus is known as Shukra, meaning "clear, pure" or "brightness, clearness" in Sanskrit. One of the nine Navagraha, it is held to affect wealth, pleasure and reproduction; it was the son of Bhrgu, preceptor of the Daityas, and guru of the Asuras. Modern Chinese, Korean, Japanese and Vietnamese (citation needed) cultures refer to the planet literally as the “metal star” (金星), based on the Five elements.

Physical characteristics:

Venus is one of the four rocky planets in our solar system whit a size and mass very similar to the Earth and often described as Earth's "sister" or "twin". Venus has a diameter only 650 km less than the Earth's and its mass is 81.5% of the Earth's. But condition of Venusian surface differ radically from those on Earth, due to its dens carbon dioxide atmosphere (atmosphere of Venus contains 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen).

Internal structure:

Without seismic data or knowledge of its moment of inertia, there is little direct information about the internal structure and geochemistry of Venus. The similarity in size and density between Venus and Earth suggests that they share a similar internal structure: a core, mantle, and crust. Like that of Earth, the Venusian core is at least partially liquid because the two planets have been cooling at about the same rate. The slightly smaller size of Venus suggests that pressures are significantly lower in its deep interior than Earth. The principal difference between the two planets is the lack of plate tectonics on Venus, likely due to the dry surface and mantle. This results in reduced heat loss from the planet, preventing it from cooling and providing a likely explanation for its lack of an internally generated magnetic field.

Surface geography and geology:

About 80% of the Venusian surface is covered by smooth volcanic plains, consisting of 70% plains with wrinkle ridges and 10% smooth plains. Two highland "continents" make up the rest of its surface area, one lying in the planet's northern hemisphere and the other just south of the equator.
The northern continent is called Ishtar Terra, after Ishtar, the Babylonian goddess of love, and is about the size of Australia. Maxwell Montes, the highest mountain on Venus, lies on Ishtar Terra whit his peak at 11 km above the Venusian average surface elevation.
The southern continent is called Aphrodite Terra, after the Greek goddess of love, and is the larger of the two highland regions at roughly the size of South America. A network of fractures and faults covers much of this area.

Mountains as well as the impact craters and valleys commonly found on rocky planets, Venus has a number of unique surface features. Among these are flat-topped volcanic features called farra, which look somewhat like pancakes and range in size from 20–50 km across, and 100–1,000 m high; radial, star-like fracture systems called Novae, features with both radial and concentric fractures resembling spider webs, known as Arachnoids; and Coronae, circular rings of fractures sometimes surrounded by a depression. These features are volcanic in origin.

The longitudes of physical features on Venus are expressed relative to its prime meridian. The original prime meridian passed through the radar-bright spot at the center of the oval feature Eve, located south of Alpha Regio. After the Venera missions were completed, the prime meridian was redefined to pass through the central peak in the crater Ariadne.

Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it possesses some 167 large volcanoes that are over 100 km across. The only volcanic complex of this size on Earth is the Big Island of Hawaii. This is not because Venus is more volcanically active than Earth, but because its crust is older. Earth's oceanic crust is continually recycled by subduction at the boundaries of tectonic plates and has an average age of about 100 million years, while the Venusian surface is estimated to be 300–600 million years old.

Several lines of evidence point to ongoing volcanic activity on Venus. During the Soviet Venera program, the Venera 11 and Venera 12 probes detected a constant stream of lightning and Venera 12 recorded a powerful clap of thunder soon after it landed. The European Space Agency's Venus Express recorded abundant lightning in the high atmosphere. While rainfall drives thunderstorms on Earth, there is no rainfall on the surface of Venus (though it does rain sulfuric acid in the upper atmosphere that evaporates around 25 km above the surface). One possibility is that ash from a volcanic eruption was generating the lightning. Another piece of evidence comes from measurements of sulfur dioxide concentrations in the atmosphere, which were found to drop by a factor of 10 between 1978 and 1986. This may imply that the levels had earlier been boosted by a large volcanic eruption.

There are almost a thousand impact craters on Venus evenly distributed across its surface. On other cratered bodies, such as the Earth and the Moon, craters show a range of states of degradation. On the Moon, degradation is caused by subsequent impacts, while on Earth, it is caused by wind and rain erosion. On Venus, about 85% of craters are in pristine condition. The number of craters, together with their well-preserved condition, indicates that the planet underwent a global resurfacing event about 300–600 million years ago, followed by a decay in volcanism. Earth's crust is in continuous motion, but it is thought that Venus cannot sustain such a process. Without plate tectonics to dissipate heat from its mantle, Venus instead undergoes a cyclical process in which mantle temperatures rise until they reach a critical level that weakens the crust. Then, over a period of about 100 million years, subduction occurs on an enormous scale, completely recycling the crust.

Magnetic field and core:

In 1967, Venera-4 found that the Venusian magnetic field is much weaker than that of Earth. This magnetic field is induced by an interaction between the ionosphere and the solar wind, rather than by an internal dynamo in the core like the one inside the Earth. Venus' small induced magnetosphere provides negligible protection to the atmosphere against cosmic radiation. This radiation may result in cloud-to-cloud lightning discharges.

The lack of an intrinsic magnetic field at Venus was surprising given that it is similar to Earth in size, and was expected also to contain a dynamo at its core. A dynamo requires three things: a conducting liquid, rotation, and convection. The core is thought to be electrically conductive and, while its rotation is often thought to be too slow, simulations show that it is adequate to produce a dynamo. This implies that the dynamo is missing because of a lack of convection in the Venusian core. On Earth, convection occurs in the liquid outer layer of the core because the bottom of the liquid layer is much hotter than the top. On Venus, a global resurfacing event may have shut down plate tectonics and led to a reduced heat flux through the crust. This caused the mantle temperature to increase, thereby reducing the heat flux out of the core. As a result, there is not an internal geodynamo that can drive a magnetic field. Instead the heat energy from the core is being used to reheat the crust.

One possibility is that Venus has no solid inner core or its core is not currently cooling, so that the entire liquid part of the core is at approximately the same temperature. Another possibility is that its core has already completely solidified. The state of the core is highly dependent on the concentration of sulfur, which is unknown at present.b

| la 5:03 PM

1 comentarii:

Burlacita said...

Multumesc pentru sfat, :) drept rasplata iti voi pune un lik pe blog la parteneri :) astept un comm la o postare cu ce nume sa te adaug.
O seara placuta!

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