General information about Venus

The second largest planet from the Sun solar system. One of the terrestrial planets, by their nature similar to Earth, but smaller. Like Earth, it is surrounded by a dense atmosphere. Venus comes closer to Earth of any other planet and is the brightest celestial object (not counting the Sun and the Moon). Light of Venus is so bright that if in heaven there is no sun, no moon, it makes the objects cast shadows. However, when looking through a telescope, Venus is disappointing, and it is not surprising that until recent years it was considered "the planet of secrets." The ancient Greeks gave the planet the name of his best of the goddess Aphrodite, as the Romans then pereinachili by - his own and named the planet Venus, which, in general, the same thing. However, this does not happen immediately. At one time it was thought that the sky is just two of the world. Rather, then a star, one - dazzlingly bright, was seen in the morning, the other is the same - in the evening. They even called in different ways, yet the Chaldean astronomers, after long observation and more much thought did not come to the conclusion that the star is still one that makes it a great honor as a specialist.

Located closer to the Sun than our planet, Venus receives from it in two and a half times more light and heat than Earth. Nevertheless, the shadow of Venus dominates the frost more than 20 degrees below zero, as here do not get sunlight for a very long time.
Surface of Venus is always covered by dense cloud layers, because of which the visible light surface detail almost not visible, although the photos in the ultraviolet show banded structure, including the characteristic Y-shaped piece.

Studying Venus spacecraft

In 1930, Venus appeared on some of the information. It was found that its atmosphere is composed mainly of carbon dioxide, which can act as a sort of veil, holding the sun's heat. Were popular two pictures of the planet. One painted surface of Venus is almost completely covered with water, which could develop primitive forms of life - as it was on Earth billions of years ago. Another represents Venus as a hot, dry and dusty desert.

The first direct measurements of composition and other characteristics of the Venusian atmosphere were made by the Soviet spacecraft Venera-4 "(1967), and the first measurements of temperature and pressure at the surface of the planet - Venus -7" (1970). Then for several years in a? Her country had implemented a series of launches of spacecraft (Venera-8-14 "," Vega-1, 2), with which it continued to study the characteristics of the atmosphere, in the seven landing sites measured the chemical composition surface material, four - received television panorama nearest? their neighborhoods landing. U.S. scientists conducted three sensing of the atmosphere of Venus with flying spacecraft (Mariner 2, 1962, Mariner 5, 1967, Mariner 10, 1973), and then sent to Venus two spacecraft Pioneer Venus' (1978), which bore the brunt of four landing a probe for studying the atmosphere and the satellite with a radar to measure the heights and the determination of radio-physical properties of the surface.

? The image of Venus in false color, constructed on the basis of radar data from AMC's "Magellan" between 1990 and 1993. To fill in the missing parts of the image was used less detailed information from the AMC "Pioneer" and a series of "Venus". This view opens from the point of 180 ° east longitude above the equator. Vivid pictures of the more responsible? Erohovatym surface area of the planet; dark - smooth, or perhaps covered in dust.

In 1962 the Mariner 2 space? Ate vicinity of Venus and gave information which confirmed that its surface is very hot. It was also established that the rotation period of Venus around the axis - long, about 243 Earth days - the pain? E than the period of revolution around the Sun (224.7 days), so that on Venus' day "is longer, and calendar Sauveur? Enno unusual.

Mariner 10 approached Venus in February 1974 and returned the first images of the upper layer of clouds. This unit only once about? Ate about Venus - its primary purpose was the inner planets - Mercury. However, the images were of high quality and showed a striped structure of clouds. They also confirmed that the period of rotation of the upper layer of clouds just right? B 4 days, so that the structure of the Venusian atmosphere is not like Earth's.

? The image of Venus in the ultraviolet range, obtained on Feb. 7, 1974 AMC Mariner 10 at a distance of 720000 km. ? The image is built on a mosaic of frames processed by the computer and then wipe away? Graded. In the ultraviolet rays are allocated zone of clouds, although the visible light image structure almost indistinguishable because of the opacity of the atmosphere.

The next important? Ar was taken in October 1975 when two Soviet system - "Venera 9 and Venera-10", done? Or controlled landing on the planet's surface and transmitted back images. The images were relayed orbital compartment stations remain? Imisya on circumplanetary orbit at an altitude of about 1500 km. It was a triumph of Soviet scientists, even though that "Venera 9 and Venera 10 were transferring all right? Then no more than an hour until it stopped once and for all act, for If? Room temperatures and pressure. It was found that the surface of Venus was littered with smooth rock debris, the composition similar to terrestrial basalts, many of which were about 1 m in diameter. The surface was good? Of illuminated, as a cloudy summer afternoon, so that even the floodlights were not required equipment. It was found also that the atmosphere does not have excessively high refractive properties, as expected, and all the details of landscape? AFTA were clear.

As you know, to fly the first Venera-4, 5,6,7 'was primarily a study of the atmosphere, its composition, structure properties. Since the first soft landing of Venera-8 "has opened the possibility of studying the surface and crust of the planet. While the key issue has risen to determine the chemical composition of Venusian rocks. Getting the first images of the surface of Venus on the Venera-9, 10 and determination of the content in the Venusian rock of natural radioactive elements in the Venera-8, 9,10, "greatly stimulated the re? Enie this problem. To her re? Eniyu also approached and technical capabilities of the Venusian landers and experience in creating sophisticated scientific equipment, capable to analyze the composition of the Venusian rocks in the harsh conditions that exist on the planet.

As a result of experiments conducted on the lander was first determined the chemical composition of Venusian rocks at the landing site. Planting areas were chosen in a smooth plain, and on a raised undulating plain, ie, in the geological and morphological provinces, which represents about 4 / 5 the entire surface of Venus. The rest of the surface of Venus is mainly represented by high mountain massifs? Mtar and Aphrodite.

The next serious? Ar in the study of Venus was made in 1983-1984, when the Soviet spacecraft Venera 15 and Venera 16 radar survey conducted 1 / 4 of the planet's surface (30 gr.s.?. To the North Pole) . We measured the height of the surface, and most importantly - using side-scan images of the surface obtained with a resolution? Eniem 1-2 km. ? Is the image analysis outlined the main features of the geology of the planet. It was found that in the area filming the most? Hiroko extended plains of several types, composed of layers of volcanic lava. The morphology of lava flows, combined with the results of determining the chemical composition at the landing spacecraft series "Venus" - "Vega" suggests that it is - basalt lava? Hiroko developed on Earth, Moon, and, obviously, on Mercury and Mars. Within these plains there are specific ring vulkanotektonicheskie structures hundreds of kilometers in diameter, having received? S called "crowns". Among the Plains are "islands" and "continents" rugged terrain, is not typical of other planets. Structural drawing of such a surface, defined by the intersection of numerous faults, like the form tiled roof, and because the terrain of this type is called "tessera," which in Greek means "tile". It was found that the formation of tesserae before? Estvovalo formed? Outpourings of lava plain, but to understand the relation of age? Eniyah between different types of plains failed - not enough resolution? Eniya images.

Obtained from the Magellan radar mosaic of the plains area Navka? Irina 400 km, which is designated landing area lander Soviet Venera-8.

In the area of the filming of "Venus-15, -16," was discovered about 150 impact craters with a diameter of 8 to 140 km. Knowing, though very roughly, the frequency of collisions with Venus, asteroids and comets, the number of craters per unit area of surface was also very roughly estimate the average age of the geological formations in the area of shooting. It was designated 0,5-1 billion years.

Besides data analysis, "Venus-15, 16, led to the conclusion that within the zone shoot no signs of" plate tectonics "- typical for the Earth's global organization of geologic activity, characterized by separation of the upper rigid shell - the lithosphere - a few large horizontally moving relative to each other plates. The main driving force of volcanic tectonic processes on Venus, based on analysis of data "Venus-15, 16, seemed vertical, ascending and descending, the motion of matter bowels of the planet due to thermal inhomogeneities - the so-called" hot spots "Hot spots are also important in geology of the Earth but their role is still secondary. They usually appear on a background of moving tectonic plates, such as a chain of volcanoes within a single plate. Ha Venus 'hot spots' are clearly the cause of formation of those referred to you? E rims and some other entities.

Results of the survey, "Venus-15, 16, led to the discovery of key elements of the geology of Venus. For the first time in this area to replace guesswork with? Law firm knowledge. It was found that endogenous geological processes - basaltic volcanism and fault tectonics - dominate the exogenous processes. Do not reveal any traces of liquid water on the planet. This fact and some features of the distribution of impact craters by size showed that conditions similar to today, have been on Venus during the entire interval traced into the geological history of the planet.

In the 4 May 1989 from the spaceport at Cape Canaveral in Florida started the American Space Shuttle Atlantis. When he had you? Ate satellite to orbit the Earth, the astronauts with a mechanical arm extracted from the cargo bay spacecraft Magellan, and released him in it alone. Increasing the rate of autonomous propulsion system, Magellan went to Venus to make a global survey of its surface using radar. In August 1990, flying to Venus, Magellan has slowed down, was captured by its gravitational field and became her companion since August 10, 1990. Start page survey of the planet by radar. Radar "Magellan" worked simultaneously in three modes. Joint processing of data in all modes, allows to measure in the radio reflectivity of the surface and it? Erohovatost.

In addition, high-precision determination of the Doppler frequency shift of one of the transmitters allow the spacecraft to measure small? S acceleration associated with the strengthening or weakening of the attraction of "Magellan" to the world at places where there is an excess or deficit of mass.

As a result of these measurements obtained gravity anomaly map of the analysis which, together with the study of an elevation map and images of the surface gives the opportunity to judge the deep structure of certain geological structures.

In addition to standard programs Magellan was able to get information in non-standard modes. For example, radar imagery of the surface under different viewing angles let you create a stereo pair, and thus to measure the altitude to a higher detail than that? Tatny altimeter.
Motion features

Venus moves around the Sun in its orbit that is located between the orbits of Mercury and Earth, with a sidereal period equal to 224.7 Earth days. The orbit of Venus is nearly circular - it has the smallest eccentricity among the planets of the solar system. The orbit is inclined to the ecliptic plane at an angle of 3 ° 23'39''.

Venus - the only planet in the solar system, proper rotation which is opposite to its rotation around the Sun. Period of proper rotation of close to 243 Earth days, which corresponds to the angular velocity of 2.99 × 10-7 rad / sec (from Earth 7.292 × 10-5 rad / sec). ? Is due to "reverse" direction of rotation of Venus, the duration of solar day on it 116.8 times the pain? E than on Earth, so that one Venusian year, sunrise and sunset on Venus is only twice.

The distance from Venus to Earth varies from 38 million miles to 258 million km. The slope of the equator of Venus to the plane of its orbit does not exceed? AET 3 °, because of what the seasonal changes in it are negligible.

For a terrestrial observer the angular distance of Venus from the sun does not exceed? AET 48 °, so that it is only visible for some time after sunset (evening star), or shortly before sunrise (morning star). Venus - the brightest (the Sun and the Moon), the world's shining sky. At maximum light, it reaches -4.8 magnitude. Another consequence of the location of Venus in Earth's orbit is the same as that of the moon change phases, opened in 1610g G. Galilei. During the most? His approach, when Venus is particularly bright, even in small? Th telescope can see that the planet has a kind of sickle. In addition one can observe a rare phenomenon - a transit of Venus across the solar disk. Event is relatively rare, occurring about twice a century - or rather the frequency 121,5-8-105,5-8 years. The previous passage was 6 December 1882, and the following will now be June 8, 2004 and June 6, 2012.

Period of the planet's rotation and the coordinates of its North Pole, the resulting joint processing of airborne radar and Doppler measurements of the Magellan and Venera-15, -16 "for 20 reference points on the surface of Venus, were as follows: The period of rotation T = 243.0183 Earth days . Right ascension = 272.57. Dec. = 67.14.

The atmosphere of the planet

Venus is sometimes called one of the most mysterious planets in the solar system: a dense cloud cover envelops its surface. The atmosphere on Venus was opened by MV Lomonosov. Watching the 6 June 1761 transit of Venus across the solar disk, he noticed that at the beginning of the passage, when Venus is only a small? Th part in? La on the solar disk, there was "thin as hair shine, wrapping? Its portion of the disk of the planet has not yet entered ? her on the solar disk. Similarly, when the descent of Venus from the disk, "appeared on the edge of the Sun Doodle, which is so distinctly uchinyalsya, the closer you come to the degeneration of Venus." These observations served as evidence of the existence of the atmosphere of Venus.

The mass of the atmosphere of Venus is about 100 times greater? AET mass of the Earth's atmosphere. Dominant share of the atmosphere is carbon dioxide (CO2 ~ 97%), nitrogen (N2) - about 3% water vapor (H2O) - 0,05%, oxygen - a few thousandths of a percent. In very small amounts of impurities are also SO2, H2S, CO, HCl, HF. The surface temperature of Venus (at the mean radius of the planet) - about 750 K (470 ° C, while the maximum recorded 530 ° C), and its daily fluctuations are negligible. Pressure - about 107 Pa, or 100 atm, the gas density by almost two orders of magnitude? E than the Earth's atmosphere. The establishment of these facts was a disappointment to many researchers believe? Them that this so similar to a? Y world conditions similar to those that have been on Earth the Carboniferous period, and consequently, there is a similar fauna. The first definition of temperature, it seemed, could justify such hopes, but the clarification (in particular, with re-entry vehicles) have shown that due to the greenhouse effect near the surface of Venus ruled out any existence of liquid water.

The clouds of Venus are composed primarily of 75-80-percent sulfuric acid. Droplets of sulfuric acid arose? Them under the action of sunlight in the atmosphere of carbon dioxide, as well as in the clouds there is water vapor and sulfur compounds. The water vapor concentration increases with altitude, peaking at an altitude of 50 km, where she is a hundred times you? E than a solid surface, ie the share of steam at this height is close to one percent. The temperature and pressure at first falls with increasing altitude. Minimum temperature (150-170 K) is defined at an altitude of 100-120 km, and as far? Its recovery temperature increases, reaching at an altitude of 12 thousand km of 600-800 K. It is established that the light isotope of argon on Venus is two orders of pain ? e than on Earth. The upper cloud layers of Venus reflects 76% of incident sunlight.

The wind is very weak at the surface of the planet (not exceeding 1 m / s) at a height svy? E 50 km increased to 150 m / sec. Observations with the automatic space stations found in the atmosphere of a thunderstorm.

The shape and size. Surface relief

Until used for studies of Venus only optical telescopes able to measure it? Then the upper limit of the radius of the dense cloud cover that covers the surface of Venus. The emergence of radiointerferentsionnyh methods allowed (because the clouds are transparent to electromagnetic waves, radio spectrum) to an investigation of its solid surface. An even more accurate data were obtained, when Venus was within the reach of spacecraft (Soviet, series "Venus", and the U.S., the series "Mariner" and "Pioneer Venus"). The most accurate value of the mean radius of the solid surface, found to date by radiovysotometricheskih and trajectory measurements is 6051,5 ± 0,1 km. The radius of the cloud-top - about 6,120 km.

The figure of the planet is close to spherical. More precisely, it can be represented by triaxial ellipsoid whose oblateness two orders of magnitude smaller? E, than the Earth. In the equatorial plane of the axis of the ellipsoid are equal to 6052,02 ± 0,1 km and 6050,99 ± 0,14 km polar axis is equal to 6051, 54 ± 0,1 km.

The center of mass of the planet shifted with respect? Eniyu to its geometric center at 430 ± 120 km. The volume of the solid part of Venus is 0.859 of the Earth.

Perspective view of the Venusian volcanic mountains Siv false-color derived from the radar images from Magellan. The volcano is 300 km in diameter and 2 km in height.

Form part of the surface of Venus in the false-color derived from the radar images from Magellan. In the foreground is visible Mountain Sapa? height of 1.5 km and 400 km across. In the background is on the horizon you can see Mount Maat.

? Spolzuya spacecraft was able to analyze the chemical composition of some surface rocks and pass several panoramic images of rocky desert landscape? Aftov. The first radar maps drawn by one of the orbiting spacecraft, showed that pain? First part of the surface of Venus is busy about? Irnymi plains (85% flat) over which the lift? Ayutsya three areas - the pain? S plateau a few kilometers. One of them is a huge volcanic plateau (archipelago? Tar - the land? Tar), comparable in size to Australia - in the northern half? Arias and the land of Aphrodite near the equator. You? E all (12 km you? E average surface) rising mountains Maxwell. Difference in height along the equator, about 5 km. Bottom? Th point on the surface at a depth of 2.5 km from the average.

On the surface of Venus, discovered the craters, faults and other features leaked? Of her intense tectonic processes. Clearly visible traces of the bombing of a shock. The surface is covered with rocks and slabs of various sizes, surface rocks are similar in composition to terrestrial sedimentary rocks.

In 1990 U.S. space probe Magellan launched a program of mapping the surface with sophisticated radar techniques and the degree of detail, far exceeding? Ayuschey made at that time level. The land was transferred set of images showing how the formation of shock structures and the presence of a relatively recent pro? Scrap of volcanic activity. By the standards of the Solar System surface of Venus is rather young: the oldest craters seem to have appeared about 800 million years ago. However, evidence of modern volcanic activity were detected. ? Is the powerful atmosphere and high temperature impact craters on Venus on the form are quite different from craters on other planets and moons. Small? S meteorites tend to burn up in Venus' atmosphere, so its surface is no small craters. As for shock impacts the pain? Of meteorites, the emissions? Ennoe substance upon impact is not spread by pain? Th area, and in molten form to form spread over around? Ihsya craters. It was discovered many different parts of volcanic origin: lava flows, small? S dome of 2-3 km in diameter, the pain? S volcanic cones that are across hundreds of kilometers, "crowns" and arachnoid structures - the so-called "arachnoiditis". Crowns of Venus - round or oval volcanic formations, surrounded by ridges, grooves and radial lines.

Form part of the surface of Venus in the false-color derived from the radar images from Magellan. It shows a very high shield volcano on Venus Maat (the height of 8 km).

Obtained from the Magellan radar mosaic, giving the image of volcanic structures, known as the "web". Such formations are still found only on Venus. Dimensions visible on the image structures ranging from 50 to 230 km.

They differ from any of the items found on other planets or moons, and perhaps represent a collapsed? S volcanic dome. Arachnoiditis, get it? S own "spider" name from the outside? His resemblance to the spiders, reminiscent of the crowns, but have less? S size. According to one theory, arachnoiditis before? Estvovali crown. Bright lines extending from the center for many miles, possibly correspond to the faults of the surface, appeared? Them struggled when magma from the bowels of the planet.

Shooting Magellan showed that in its main features the geological structure of Venus does not differ from that in the area filming "Venus, 15, 16." Ha planet predominate, occupying about 85% of the area, volcanic, obviously, basalt plains, and among them are the most common species with a smooth (in weight? Tabe images) surface, complicated network of narrow, winding pologosklonnyh ridges. These ridges are known as the volcanic plains of the moon and Mars and the warping of the surface structures are in compression. In addition to the plains with sinuous ridges are observed, occupying a relatively small? "S Square, and the surface areas of the plains, thickly covered with cracks (the structure of extension), or crumpled in the extended zone? Iroki ridges (the structure of compression), or virtually no violation? Ennoy any, discernible in the images, the tectonic deformations. Snapshot Magellan revealed that the smooth plains with undisturbed? Ennoy surface of younger plains with meandering ridges, while the other two mentioned species of the plains - the ancient.

"Continents" and "islands" Tesser among plains occupy a total of about 8% of the planet's surface. Tesserae ancient of all these varieties of plains material are in contact with tessera goes inside tessernyh blocks in depressions in the landscape. Impression that the tesserae form a foundation for much of the plains, and perhaps, under all the plains.

? Is a snapshot analysis of Magellan that in the tectonic history of the violation? Eny to form? Their observed appearance Tesser, you can select an earlier stage of compressive deformation and follow? S followed by stage stretching.

? plains and tesserae are cut extended (thousands of kilometers), it is difficult constructed troughs formed by swarms of tectonic faults. The topography and morphology are similar to the so-called rift zones of the Earth and, apparently, have the same nature.

Ha surface of the plains of the planet in some places, recorded in the photographs, "Magellan" discovered mysterious "bed" in length from hundreds to several thousand kilometers? Irina from 2-3 to 10-15 km. They have the typical symptoms of valleys cut by the passage of some liquid - meandrovidnye gyrus, the divergence and convergence of individual "flow" and, in rare cases - something like a delta. At the beginning of the longest channel, called the valley Baltis, stretching some 7000 km with a very seasoned (2-3 miles)? Irina volcano located about 100 km diameter. Morphology of it - a very ordinary, typical of basalt volcanoes. By the way, the northern part of the valley Baltis was found still in images of Venus-15, -16. Ho gap? Enie images was not high enough to discern the details of this education, and it was mapped as the longest crack of unknown origin.

It was a mystery how fluid penetrate these channels. The easiest way would be to assume that they - the result of thermal erosion of the current flow of basaltic lava. Ho calculations show that the path length of 7000 km of basaltic lava flow is not enough supply heat to flow without interruption and podplavlyat basaltic material is plain, cutting into her bed. This is likely, for example, strongly overheated komatiitic lava, or even more exotic fluids such as molten carbonate or molten sulfur. Hebol? S (hundreds of meters long lava channels are known in some terrestrial basaltic volcanoes. Education up to several tens of kilometers in length, apparently related channels on Venus, is on the Moon.? X considered as a result of thermal erosion of basaltic lava plains of the lunar maria. But lava beds of the Earth and the Moon is still significantly less? e beds of Venus, so the mystery remains unsolved recent origin? ennoy.

Obtained from the Magellan radar image of the eastern tip of Alpha. Dome-shaped hills of volcanic origin, have a diameter of about 25 km, reaching a height of 750 m.