Венера номер от солнца

Какая по счету Венера от Солнца?

Венера – самый яркий объект на небосводе после Солнца и Луны. Какое место она занимает в Солнечной системе?

Венера – вторая планета от Солнца. Она находится между Меркурием (1-ой планетой) и Землей (3-ей планетой). Венерианская орбита – это эллипс, очень близкий к окружности. Расстояние между планетой и Солнцем изменяется от 107,4 до 108,8 млн км.

Венеру часто называют «сестрой Земли». Дело в том, что две эти планеты обладают рядом схожих черт. Если радиус Земли составляет 6371 км, то у Венеры его величина составляет 6051 км. Масса Венеры составляет 81% от земной массы, а объем – 85%. Близки друг к другу и значения ускорения свободного падения 8,87 м/с2 на Венере и 9,78 м/с2 на Земле. Все другие планеты Солнечной системы либо в разы больше, либо в разы меньше Земли по массе и объему.

Хотя Венера и располагается дальше Меркурия от Солнца, именно ей принадлежит статус самой горячей планеты в Солнечной системе. Температура на ее поверхности может подниматься до +477° С, причем ночью она уменьшается незначительно. Такой экстремальный климат связан с тем, что Венера обладает очень плотной атмосферой, давление которой в 100 раз превышает давление у поверхности Земли. Аналогичное давление испытывают корпуса подводных лодок на глубине 900 м.

При этом большая часть атмосферы Венеры (96,5%) – это углекислый газ. Он создает сильнейший парниковый эффект, который и разогревает планету. Если бы венерианская атмосфера была аналогична земной, то температура у поверхности не превышала бы 80° С, то есть на ней могла бы быть жидкая вода и даже жизнь.

Атмосфера также способствует перераспределению тепла, поэтому температура на Венере почти не зависит от времени суток. Кстати, день и ночь меняются на планете очень медленно. На полный оборот вокруг своей оси Венера тратит 243 земных дня. На оборот вокруг звезды она тратит только 224,6 дня. Таким образом, венерианский год оказывается короче венерианских суток!

Список использованных источников

• https://cosmosplanet.ru/solnechnayasistema/venera/kakaya-po-schyotu-venera-ot-solntsa.html
• https://spacegid.com/planetyi-nashey-s-vami-solnechnoy-sistemyi.html
• https://ru.wikipedia.org/wiki/Венера

Пришелец Инопланетянович

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Venus

Near-global view of Venus in natural colour, taken by the MESSENGER space probe
Designations
Pronunciation	(listen)
Named after	Venus
Adjectives	Venusian ,[1] rarely Cytherean [2] or Venerean / Venerian [3]
Orbital characteristics[5][7]
Epoch J2000
Aphelion	0.728213 AU 108,939,000 km
Perihelion	0.718440 AU 107,477,000 km
Semi-major axis	0.723332 AU 108,208,000 km
Eccentricity	0.006772[4]
Orbital period (sidereal)	224.701 d[5] 0.615198 yr 1.92 Venus solar day
Orbital period (synodic)	583.92 days[5]
Average orbital speed	35.02 km/s
Mean anomaly	50.115°
Inclination	3.39458° to ecliptic 3.86° to Sun’s equator 2.15° to invariable plane[6]
Longitude of ascending node	76.680°[4]
Argument of perihelion	54.884°
Satellites	None
Physical characteristics
Mean radius	6,051.8±1.0 km[8] 0.9499 Earths
Flattening	0[8]
Surface area	4.6023×108 km2 0.902 Earths
Volume	9.2843×1011 km3 0.857 Earths
Mass	4.8675×1024 kg[9] 0.815 Earths
Mean density	5.243 g/cm3
Surface gravity	8.87 m/s2 0.904 g
Escape velocity	10.36 km/s (6.44 mi/s)[10]
Synodic rotation period	−116.75 d (retrograde)[11] 1 Venus solar day
Sidereal rotation period	−243.0226 d (retrograde)[12]
Equatorial rotation velocity	6.52 km/h (1.81 m/s)
Axial tilt	2.64° (for retrograde rotation) 177.36° (to orbit)[5][note 1]
North pole right ascension	18h 11m 2s 272.76°[13]
North pole declination	67.16°
Albedo	0.689 (geometric)[14] 0.76 (Bond)[15]
Temperature	232 K (−41 °C) (blackbody temperature)[16]
Surface temp. min mean max Kelvin 737 K[5] Celsius 464 °C Fahrenheit 867 °F
Surface absorbed dose rate	2.1×10−6 μGy/h[18]
Surface equivalent dose rate	2.2×10−6 μSv/h 0.092–22 μSv/h at the habitable zone[18]
Apparent magnitude	−4.92 to −2.98[17]
Angular diameter	9.7″–66.0″[5]
Atmosphere[5]
Surface pressure	93 bar (9.3 MPa) 92 atm
Composition by volume	96.5% carbon dioxide 3.5% nitrogen 0.015% sulfur dioxide 0.0070% argon 0.0020% water vapour 0.0017% carbon monoxide 0.0012% helium 0.0007% neon Trace carbonyl sulfide Trace hydrogen chloride Trace hydrogen fluoride
^ Defining the rotation as retrograde, as done by NASA space missions and the USGS, puts Ishtar Terra in the northern hemisphere and makes the axial tilt 2.64°. Following the right-hand rule for prograde rotation puts Ishtar Terra in the southern hemisphere and makes the axial tilt 177.36°.

Venus is the second planet from the Sun. It is sometimes called Earth’s «sister» or «twin» planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth’s sky never far from the Sun, either as morning star or evening star. Aside from the Sun and Moon, Venus is the brightest natural object in Earth’s sky, capable of casting visible shadows on Earth at dark conditions and being visible to the naked eye in broad daylight.^[19][20]

Venus is the second largest terrestrial object of the Solar System. It has a surface gravity slightly lower than on Earth and has a very weak induced magnetosphere. The atmosphere of Venus consists mainly of carbon dioxide, and, at the planet’s surface, is the densest and hottest of the atmospheres of the four terrestrial planets. With an atmospheric pressure at the planet’s surface of about 92 times the sea level pressure of Earth and a mean temperature of 737 K (464 °C; 867 °F), the carbon dioxide gas at Venus’s surface is in the supercritical phase of matter. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, making it the planet with the highest albedo in the Solar System. It may have had water oceans in the past,^[21][22] but after these evaporated the temperature rose under a runaway greenhouse effect.^[23] The possibility of life on Venus has long been a topic of speculation but convincing evidence has yet to be found.

Like Mercury, Venus does not have any moons.^[24] Solar days on Venus, with a length of 117 Earth days,^[25] are just about half as long as its solar year, orbiting the Sun every 224.7 Earth days.^[26] This Venusian daylength is a product of it rotating against its orbital motion, halving its full sidereal rotation period of 243 Earth days, the longest of all the Solar System planets. Venus and Uranus are the only planets with such a retrograde rotation, making the Sun move in their skies from their western horizon to their eastern. The orbit of Venus around the Sun is the closest to Earth’s orbit, bringing them closer than any other pair of planets. This occurs during inferior conjunction with a synodic period of 1.6 years. However, Mercury is more frequently the closest to each.

The orbits of Venus and Earth result in the lowest gravitational potential difference and lowest delta-v needed to transfer between them than to any other planet. This has made Venus a prime target for early interplanetary exploration. It was the first planet beyond Earth that spacecraft were sent to, starting with Venera 1 in 1961, and the first planet to be reached, impacted and in 1970 successfully landed on by Venera 7. As one of the brightest objects in the sky, Venus has been a major fixture in human culture for as long as records have existed. It has been made sacred to gods of many cultures, gaining its mainly used name from the Roman goddess of love and beauty which it is associated with. Furthermore it has been a prime inspiration for writers, poets and scholars. Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BCE.^[27] Plans for better exploration with rovers or atmospheric missions, potentially crewed, at levels with almost Earth-like conditions have been proposed.

Physical characteristics

Venus is one of the four terrestrial planets in the Solar System, meaning that it is a rocky body like Earth. It is similar to Earth in size and mass and is often described as Earth’s «sister» or «twin».^[28] The diameter of Venus is 12,103.6 km (7,520.8 mi)—only 638.4 km (396.7 mi) less than Earth’s—and its mass is 81.5% of Earth’s. Conditions on the Venusian surface differ radically from those on Earth because its dense atmosphere is 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen.^[29] The surface pressure is 9.3 megapascals (93 bars), and the average surface temperature is 737 K (464 °C; 867 °F), above the critical points of both major constituents and making the surface atmosphere a supercritical fluid.

Atmosphere and climate

Venus has an extremely dense atmosphere composed of 96.5% carbon dioxide, 3.5% nitrogen—both exist as supercritical fluids at the planet’s surface—and traces of other gases including sulfur dioxide.^[30] The mass of its atmosphere is 92 times that of Earth’s, whereas the pressure at its surface is about 93 times that at Earth’s—a pressure equivalent to that at a depth of nearly 1 km (5⁄8 mi) under Earth’s oceans. The density at the surface is 65 kg/m³ (4.1 lb/cu ft), 6.5% that of water or 50 times as dense as Earth’s atmosphere at 293 K (20 °C; 68 °F) at sea level. The CO₂-rich atmosphere generates the strongest greenhouse effect in the Solar System, creating surface temperatures of at least 735 K (462 °C; 864 °F).^[26][31] This makes the Venusian surface hotter than Mercury’s, which has a minimum surface temperature of 53 K (−220 °C; −364 °F) and maximum surface temperature of 700 K (427 °C; 801 °F),^[32][33] even though Venus is nearly twice Mercury’s distance from the Sun and thus receives only 25% of Mercury’s solar irradiance. Because of its runaway greenhouse effect, Venus has been identified by scientists such as Carl Sagan as a warning and research object linked to climate change on Earth.^[34]

Venus Temperature^[35]

Type	Surface Temperature
Maximum	900 °F (482 °C)
Normal	847 °F (453 °C)
Minimum	820 °F (438 °C)

Venus’s atmosphere is extremely rich in primordial noble gases compared to that of Earth.^[36] This enrichment indicates an early divergence from Earth in evolution. An unusually large comet impact^[37] or accretion of a more massive primary atmosphere from solar nebula^[38] have been proposed to explain the enrichment. However, the atmosphere is also depleted of radiogenic argon, a proxy to mantle degassing, suggesting an early shutdown of major magmatism.^[39][40]

Studies^[which?] have suggested that billions of years ago, Venus’s atmosphere could have been much more like the one surrounding the early Earth, and that there may have been substantial quantities of liquid water on the surface. After a period of 600 million to several billion years,^[41] solar forcing from rising luminosity of the Sun caused the evaporation of the original water. A runaway greenhouse effect was created once a critical level of greenhouse gases (including water) was added to its atmosphere.^[42] Although the surface conditions on Venus are no longer hospitable to any Earth-like life that may have formed before this event, there is speculation on the possibility that life exists in the upper cloud layers of Venus, 50 km (30 mi) up from the surface, where the temperature ranges between 303 and 353 K (30 and 80 °C; 86 and 176 °F) but the environment is acidic.^[43][44][45] The putative detection of an absorption line of phosphine in Venus’s atmosphere, with no known pathway for abiotic production, led to speculation in September 2020 that there could be extant life currently present in the atmosphere.^[46][47] Later research attributed the spectroscopic signal that was interpreted as phosphine to sulfur dioxide,^[48] or found that in fact there was no absorption line.^[49][50]

Thermal inertia and the transfer of heat by winds in the lower atmosphere mean that the temperature of Venus’s surface does not vary significantly between the planet’s two hemispheres, those facing and not facing the Sun, despite Venus’s extremely slow rotation. Winds at the surface are slow, moving at a few kilometres per hour, but because of the high density of the atmosphere at the surface, they exert a significant amount of force against obstructions, and transport dust and small stones across the surface. This alone would make it difficult for a human to walk through, even without the heat, pressure, and lack of oxygen.^[51]

Above the dense CO₂ layer are thick clouds, consisting mainly of sulfuric acid, which is formed by sulfur dioxide and water through a chemical reaction resulting in sulfuric acid hydrate. Additionally, the clouds consist of approximately 1% ferric chloride.^[52][53] Other possible constituents of the cloud particles are ferric sulfate, aluminium chloride and phosphoric anhydride. Clouds at different levels have different compositions and particle size distributions.^[52] These clouds reflect and scatter about 90% of the sunlight that falls on them back into space, and prevent visual observation of Venus’s surface. The permanent cloud cover means that although Venus is closer than Earth to the Sun, it receives less sunlight on the ground. Strong 300 km/h (185 mph) winds at the cloud tops go around Venus about every four to five Earth days.^[54] Winds on Venus move at up to 60 times the speed of its rotation, whereas Earth’s fastest winds are only 10–20% rotation speed.^[55]

The surface of Venus is effectively isothermal; it retains a constant temperature not only between the two hemispheres but between the equator and the poles.^[5][56] Venus’s minute axial tilt—less than 3°, compared to 23° on Earth—also minimises seasonal temperature variation.^[57] Altitude is one of the few factors that affect Venusian temperature. The highest point on Venus, Maxwell Montes, is therefore the coolest point on Venus, with a temperature of about 655 K (380 °C; 715 °F) and an atmospheric pressure of about 4.5 MPa (45 bar).^[58][59] In 1995, the Magellan spacecraft imaged a highly reflective substance at the tops of the highest mountain peaks that bore a strong resemblance to terrestrial snow. This substance likely formed from a similar process to snow, albeit at a far higher temperature. Too volatile to condense on the surface, it rose in gaseous form to higher elevations, where it is cooler and could precipitate. The identity of this substance is not known with certainty, but speculation has ranged from elemental tellurium to lead sulfide (galena).^[60]

Although Venus has no seasons as such, in 2019, astronomers identified a cyclical variation in sunlight absorption by the atmosphere, possibly caused by opaque, absorbing particles suspended in the upper clouds. The variation causes observed changes in the speed of Venus’s zonal winds and appears to rise and fall in time with the Sun’s 11-year sunspot cycle.^[61]

The existence of lightning in the atmosphere of Venus has been controversial^[62] since the first suspected bursts were detected by the Soviet Venera probes.^[63][64][65] In 2006–07, Venus Express clearly detected whistler mode waves, the signatures of lightning. Their intermittent appearance indicates a pattern associated with weather activity. According to these measurements, the lightning rate is at least half of that on Earth,^[66] however other instruments have not detected lightning at all.^[62] The origin of any lightning remains unclear, but could originate from the clouds or volcanoes.

In 2007, Venus Express discovered that a huge double atmospheric vortex exists at the south pole.^[67][68] Venus Express also discovered, in 2011, that an ozone layer exists high in the atmosphere of Venus.^[69] On 29 January 2013, ESA scientists reported that the ionosphere of Venus streams outwards in a manner similar to «the ion tail seen streaming from a comet under similar conditions.»^[70][71]

In December 2015, and to a lesser extent in April and May 2016, researchers working on Japan’s Akatsuki mission observed bow shapes in the atmosphere of Venus. This was considered direct evidence of the existence of perhaps the largest stationary gravity waves in the solar system.^[72][73][74]

Geography

The Venusian surface was a subject of speculation until some of its secrets were revealed by planetary science in the 20th century. Venera landers in 1975 and 1982 returned images of a surface covered in sediment and relatively angular rocks.^[77] The surface was mapped in detail by Magellan in 1990–91. The ground shows evidence of extensive volcanism, and the sulfur in the atmosphere may indicate that there have been recent eruptions.^[78][79]

About 80% of the Venusian surface is covered by smooth, volcanic plains, consisting of 70% plains with wrinkle ridges and 10% smooth or lobate plains.^[80] 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. Its peak is 11 km (7 mi) above the Venusian average surface elevation.^[81] 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.^[82]

The absence of evidence of lava flow accompanying any of the visible calderas remains an enigma. The planet has few impact craters, demonstrating that the surface is relatively young, at 300–600 million years old.^[83][84] Venus has some unique surface features in addition to the impact craters, mountains, and valleys commonly found on rocky planets. Among these are flat-topped volcanic features called «farra», which look somewhat like pancakes and range in size from 20 to 50 km (12 to 31 mi) across, and from 100 to 1,000 m (330 to 3,280 ft) 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.^[85]

Most Venusian surface features are named after historical and mythological women.^[86] Exceptions are Maxwell Montes, named after James Clerk Maxwell, and highland regions Alpha Regio, Beta Regio, and Ovda Regio. The last three features were named before the current system was adopted by the International Astronomical Union, the body which oversees planetary nomenclature.^[87]

The longitude of physical features on Venus are expressed relative to its prime meridian. The original prime meridian passed through the radar-bright spot at the centre of the oval feature Eve, located south of Alpha Regio.^[88] After the Venera missions were completed, the prime meridian was redefined to pass through the central peak in the crater Ariadne on Sedna Planitia.^[89][90]

The stratigraphically oldest tessera terrains have consistently lower thermal emissivity than the surrounding basaltic plains measured by Venus Express and Magellan, indicating a different, possibly a more felsic, mineral assemblage.^[21][91] The mechanism to generate a large amount of felsic crust usually requires the presence of water ocean and plate tectonics, implying that habitable condition had existed on early Venus. However, the nature of tessera terrains is far from certain.^[92]

Volcanism

Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it has 167 large volcanoes that are over 100 km (60 mi) across. The only volcanic complex of this size on Earth is the Big Island of Hawaii.^[85]: 154 This is not because Venus is more volcanically active than Earth, but because its crust is older and is not subject to the same erosion process. Earth’s oceanic crust is continually recycled by subduction at the boundaries of tectonic plates, and has an average age of about a hundred million years,^[93] whereas the Venusian surface is estimated to be 300–600 million years old.^[83][85]

Several lines of evidence point to ongoing volcanic activity on Venus. Sulfur dioxide concentrations in the atmosphere dropped by a factor of 10 between 1978 and 1986, jumped in 2006, and again declined 10-fold.^[94] This may mean that levels had been boosted several times by large volcanic eruptions.^[95][96] It has also been suggested that Venusian lightning (discussed below) could originate from volcanic activity (i.e. volcanic lightning). In January 2020, astronomers reported evidence that suggests that Venus is currently volcanically active, specifically the detection of olivine, a volcanic product that would weather quickly on the planet’s surface.^[97][98]

In 2008 and 2009, the first direct evidence for ongoing volcanism was observed by Venus Express, in the form of four transient localized infrared hot spots within the rift zone Ganis Chasma,^{[99][n 1]} near the shield volcano Maat Mons. Three of the spots were observed in more than one successive orbit. These spots are thought to represent lava freshly released by volcanic eruptions.^[100][101] The actual temperatures are not known, because the size of the hot spots could not be measured, but are likely to have been in the 800–1,100 K (527–827 °C; 980–1,520 °F) range, relative to a normal temperature of 740 K (467 °C; 872 °F).^[102]

Craters

Almost a thousand impact craters on Venus are evenly distributed across its surface. On other cratered bodies, such as Earth and the Moon, craters show a range of states of degradation. On the Moon, degradation is caused by subsequent impacts, whereas on Earth it is caused by wind and rain erosion. On Venus, about 85% of the craters are in pristine condition. The number of craters, together with their well-preserved condition, indicates the planet underwent a global resurfacing event 300–600 million years ago,^[83][84] followed by a decay in volcanism.^[103] Whereas Earth’s crust is in continuous motion, Venus is thought to be unable to 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.^[85]

Venusian craters range from 3 to 280 km (2 to 174 mi) in diameter. No craters are smaller than 3 km, because of the effects of the dense atmosphere on incoming objects. Objects with less than a certain kinetic energy are slowed so much by the atmosphere that they do not create an impact crater.^[104] Incoming projectiles less than 50 m (160 ft) in diameter will fragment and burn up in the atmosphere before reaching the ground.^[105]

Internal structure

Without seismic data or knowledge of its moment of inertia, little direct information is available about the internal structure and geochemistry of Venus.^[106] The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust. Like that of Earth, the Venusian core is most likely at least partially liquid because the two planets have been cooling at about the same rate,^[107] although a completely solid core cannot be ruled out.^[108] The slightly smaller size of Venus means pressures are 24% lower in its deep interior than Earth’s.^[109] The predicted values for the moment of inertia based on planetary models suggest a core radius of 2,900–3,450 km.^[108] This is in line with the first observation-based estimate of 3,500 km.^[110]

The principal difference between the two planets is the lack of evidence for plate tectonics on Venus, possibly because its crust is too strong to subduct without water to make it less viscous. 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.^[111]
Instead, Venus may lose its internal heat in periodic major resurfacing events.^[83]

Magnetic field and core

In 1967, Venera 4 found Venus’s magnetic field to be much weaker than that of Earth. This magnetic field is induced by an interaction between the ionosphere and the solar wind,^[112][113] rather than by an internal dynamo as in the Earth’s core. Venus’s small induced magnetosphere provides negligible protection to the atmosphere against cosmic radiation.

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, although its rotation is often thought to be too slow, simulations show it is adequate to produce a dynamo.^[114][115] This implies that the dynamo is missing because of a lack of convection in Venus’s core. On Earth, convection occurs in the liquid outer layer of the core because the bottom of the liquid layer is much higher in temperature 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 insulating effect would cause the mantle temperature to increase, thereby reducing the heat flux out of the core. As a result, no internal geodynamo is available to drive a magnetic field. Instead, the heat from the core is reheating the crust.^[116]

One possibility is that Venus has no solid inner core,^[117] or that its core is not 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.^[116]

The weak magnetosphere around Venus means that the solar wind is interacting directly with its outer atmosphere. Here, ions of hydrogen and oxygen are being created by the dissociation of water molecules from ultraviolet radiation. The solar wind then supplies energy that gives some of these ions sufficient velocity to escape Venus’s gravity field. This erosion process results in a steady loss of low-mass hydrogen, helium, and oxygen ions, whereas higher-mass molecules, such as carbon dioxide, are more likely to be retained. Atmospheric erosion by the solar wind could have led to the loss of most of Venus’s water during the first billion years after it formed.^[118] However, the planet may have retained a dynamo for its first 2–3 billion years, so the water loss may have occurred more recently.^[119] The erosion has increased the ratio of higher-mass deuterium to lower-mass hydrogen in the atmosphere 100 times compared to the rest of the solar system.^[120]

Orbit and rotation

Venus orbits the Sun at an average distance of about 0.72 AU (108 million km; 67 million mi), and completes an orbit every 224.7 days. Although all planetary orbits are elliptical, Venus’s orbit is currently the closest to circular, with an eccentricity of less than 0.01.^[5] Simulations of the early solar system orbital dynamics have shown that the eccentricity of the Venus orbit may have been substantially larger in the past, reaching values as high as 0.31 and possibly impacting the early climate evolution.^[121] The current near-circular orbit of Venus means that when Venus lies between Earth and the Sun in inferior conjunction, it makes the closest approach to Earth of any planet at an average distance of 41 million km (25 million mi).^{[5][n 2][122]}
The planet reaches at a orbital resonance of 8 Earth orbits to 13 Venus orbits,^[123] inferior conjunctions at a synodic period of 584 days, on average.^[5] Because of the decreasing eccentricity of Earth’s orbit, the minimum distances will become greater over tens of thousands of years. From the year 1 to 5383, there are 526 approaches less than 40 million km (25 million mi); then, there are none for about 60,158 years.^[124] While Venus approaches Earth the closest, Mercury approaches Earth more often the closest of all planets.^[125] That said, Venus and Earth still have the lowest gravitational potential difference between them than to any other planet, needing the lowest delta-v to transfer between them, than to any other planet from them.^[126][127]

All the planets in the Solar System orbit the Sun in an anticlockwise direction as viewed from above Earth’s north pole. Most planets also rotate on their axes in an anticlockwise direction, but Venus rotates clockwise in retrograde rotation once every 243 Earth days—the slowest rotation of any planet. Because its rotation is so slow, Venus is very close to spherical.^[128] A Venusian sidereal day thus lasts longer than a Venusian year (243 versus 224.7 Earth days). Venus’s equator rotates at 6.52 km/h (4.05 mph), whereas Earth’s rotates at 1,674.4 km/h (1,040.4 mph).^[132][133] Venus’s rotation period measured with Magellan spacecraft data over a 500-day period is smaller than the rotation period measured during the 16-year period between the Magellan spacecraft and Venus Express visits, with a difference of about 6.5 minutes.^[134] Because of the retrograde rotation, the length of a solar day on Venus is significantly shorter than the sidereal day, at 116.75 Earth days (making the Venusian solar day shorter than Mercury’s 176 Earth days — the 116-day figure is extremely close to the average number of days it takes Mercury to slip underneath the Earth in its orbit).^[11] One Venusian year is about 1.92 Venusian solar days.^[135] To an observer on the surface of Venus, the Sun would rise in the west and set in the east,^[135] although Venus’s opaque clouds prevent observing the Sun from the planet’s surface.^[136]

Venus may have formed from the solar nebula with a different rotation period and obliquity, reaching its current state because of chaotic spin changes caused by planetary perturbations and tidal effects on its dense atmosphere, a change that would have occurred over the course of billions of years. The rotation period of Venus may represent an equilibrium state between tidal locking to the Sun’s gravitation, which tends to slow rotation, and an atmospheric tide created by solar heating of the thick Venusian atmosphere.^[137][138]
The 584-day average interval between successive close approaches to Earth is almost exactly equal to 5 Venusian solar days (5.001444 to be precise),^[139] but the hypothesis of a spin-orbit resonance with Earth has been discounted.^[140]

Venus has no natural satellites.^[141] It has several trojan asteroids: the quasi-satellite 2002 VE68^[142][143] and two other temporary trojans, 2001 CK₃₂ and 2012 XE133.^[144] In the 17th century, Giovanni Cassini reported a moon orbiting Venus, which was named Neith and numerous sightings were reported over the following 200 years, but most were determined to be stars in the vicinity. Alex Alemi’s and David Stevenson’s 2006 study of models of the early Solar System at the California Institute of Technology shows Venus likely had at least one moon created by a huge impact event billions of years ago.^[145] About 10 million years later, according to the study, another impact reversed the planet’s spin direction and caused the Venusian moon gradually to spiral inward until it collided with Venus.^[146] If later impacts created moons, these were removed in the same way. An alternative explanation for the lack of satellites is the effect of strong solar tides, which can destabilize large satellites orbiting the inner terrestrial planets.^[141]

Observability

To the naked eye, Venus appears as a white point of light brighter than any other planet or star (apart from the Sun).^[147] The planet’s mean apparent magnitude is −4.14 with a standard deviation of 0.31.^[17] The brightest magnitude occurs during crescent phase about one month before or after inferior conjunction. Venus fades to about magnitude −3 when it is backlit by the Sun.^[148] The planet is bright enough to be seen in broad daylight,^[149] but is more easily visible when the Sun is low on the horizon or setting. As an inferior planet, it always lies within about 47° of the Sun.^[150]

Venus «overtakes» Earth every 584 days as it orbits the Sun.^[5] As it does so, it changes from the «Evening Star», visible after sunset, to the «Morning Star», visible before sunrise. Although Mercury, the other inferior planet, reaches a maximum elongation of only 28° and is often difficult to discern in twilight, Venus is hard to miss when it is at its brightest. Its greater maximum elongation means it is visible in dark skies long after sunset. As the brightest point-like object in the sky, Venus is a commonly misreported «unidentified flying object».^[151]

Phases

As it orbits the Sun, Venus displays phases like those of the Moon in a telescopic view. The planet appears as a small and «full» disc when it is on the opposite side of the Sun (at superior conjunction). Venus shows a larger disc and «quarter phase» at its maximum elongations from the Sun, and appears its brightest in the night sky. The planet presents a much larger thin «crescent» in telescopic views as it passes along the near side between Earth and the Sun. Venus displays its largest size and «new phase» when it is between Earth and the Sun (at inferior conjunction). Its atmosphere is visible through telescopes by the halo of sunlight refracted around it.^[150] The phases are clearly visible in a 4″ telescope.

Daylight apparitions

Naked-eye observations of Venus during daylight hours exist in several anecdotes and records. Astronomer Edmund Halley calculated its maximum naked eye brightness in 1716, when many Londoners were alarmed by its appearance in the daytime. French emperor Napoleon Bonaparte once witnessed a daytime apparition of the planet while at a reception in Luxembourg.^[152] Another historical daytime observation of the planet took place during the inauguration of the American president Abraham Lincoln in Washington, D.C., on 4 March 1865.^[153] Although naked eye visibility of Venus’s phases is disputed, records exist of observations of its crescent.^[154]

Transits

The Venusian orbit is slightly inclined relative to Earth’s orbit; thus, when the planet passes between Earth and the Sun, it usually does not cross the face of the Sun. Transits of Venus occur when the planet’s inferior conjunction coincides with its presence in the plane of Earth’s orbit. Transits of Venus occur in cycles of 243 years with the current pattern of transits being pairs of transits separated by eight years, at intervals of about 105.5 years or 121.5 years—a pattern first discovered in 1639 by the English astronomer Jeremiah Horrocks.^[155]

The latest pair was June 8, 2004 and June 5–6, 2012. The transit could be watched live from many online outlets or observed locally with the right equipment and conditions.^[156]

The preceding pair of transits occurred in December 1874 and December 1882; the following pair will occur in December 2117 and December 2125.^[157] The 1874 transit is the subject of the oldest film known, the 1874 Passage de Venus. Historically, transits of Venus were important, because they allowed astronomers to determine the size of the astronomical unit, and hence the size of the Solar System as shown by Horrocks in 1639.^[158] Captain Cook’s exploration of the east coast of Australia came after he had sailed to Tahiti in 1768 to observe a transit of Venus.^[159][160]

Pentagram of Venus

The pentagram of Venus is the path that Venus makes as observed from Earth. Successive inferior conjunctions of Venus repeat with a orbital resonance of 13:8 (Earth orbits eight times for every 13 orbits of Venus), shifting 144° upon sequential inferior conjunctions. The 13:8 ratio is approximate. 8/13 is approximately 0.61538 while Venus orbits the Sun in 0.61519 years.^[161] The pentagram of Venus is sometimes also referred to as the petals of Venus due to the path’s visual similarity to a flower.^[162]

Ashen light

A long-standing mystery of Venus observations is the so-called ashen light—an apparent weak illumination of its dark side, seen when the planet is in the crescent phase. The first claimed observation of ashen light was made in 1643, but the existence of the illumination has never been reliably confirmed. Observers have speculated it may result from electrical activity in the Venusian atmosphere, but it could be illusory, resulting from the physiological effect of observing a bright, crescent-shaped object.^[163][64] The ashen light has often been sighted when Venus is in the evening sky, when the evening terminator of the planet is towards to Earth.

Observation and exploration

Early observation

Because the movements of Venus appear to be discontinuous (it disappears due to its proximity to the sun, for many days at a time, and then reappears on the other horizon), some cultures did not recognize Venus as a single entity;^[164] instead, they assumed it to be two separate stars on each horizon: the morning and evening star.^[164] Nonetheless, a cylinder seal from the Jemdet Nasr period and the Venus tablet of Ammisaduqa from the First Babylonian dynasty indicate that the ancient Sumerians already knew that the morning and evening stars were the same celestial object.^{[165][164][166]} In the Old Babylonian period, the planet Venus was known as Ninsi’anna, and later as Dilbat.^[167] The name «Ninsi’anna» translates to «divine lady, illumination of heaven», which refers to Venus as the brightest visible «star». Earlier spellings of the name were written with the cuneiform sign si4 (= SU, meaning «to be red»), and the original meaning may have been «divine lady of the redness of heaven», in reference to the colour of the morning and evening sky.^[168]

The Chinese historically referred to the morning Venus as «the Great White» (Tàibái 太白) or «the Opener (Starter) of Brightness» (Qǐmíng 啟明), and the evening Venus as «the Excellent West One» (Chánggēng 長庚).^[169]

The ancient Greeks also initially believed Venus to be two separate stars: Phosphorus, the morning star, and Hesperus, the evening star. Pliny the Elder credited the realization that they were a single object to Pythagoras in the sixth century BC,^[170] while Diogenes Laërtius argued that Parmenides was probably responsible for this discovery.^[171] Though they recognized Venus as a single object, the ancient Romans continued to designate the morning aspect of Venus as Lucifer, literally «Light-Bringer», and the evening aspect as Vesper,^[172] both of which are literal translations of their traditional Greek names.

In the second century, in his astronomical treatise Almagest, Ptolemy theorized that both Mercury and Venus are located between the Sun and the Earth. The 11th-century Persian astronomer Avicenna claimed to have observed the transit of Venus,^[173] which later astronomers took as confirmation of Ptolemy’s theory.^[174] In the 12th century, the Andalusian astronomer Ibn Bajjah observed «two planets as black spots on the face of the Sun»; these were thought to be the transits of Venus and Mercury by 13th-century Maragha astronomer Qotb al-Din Shirazi, though this cannot be true as there were no Venus transits in Ibn Bajjah’s lifetime.^{[175][n 3]}

When the Italian physicist Galileo Galilei first observed the planet in the early 17th century, he found it showed phases like the Moon, varying from crescent to gibbous to full and vice versa. When Venus is furthest from the Sun in the sky, it shows a half-lit phase, and when it is closest to the Sun in the sky, it shows as a crescent or full phase. This could be possible only if Venus orbited the Sun, and this was among the first observations to clearly contradict the Ptolemaic geocentric model that the Solar System was concentric and centred on Earth.^[178][179]

The 1639 transit of Venus was accurately predicted by Jeremiah Horrocks and observed by him and his friend, William Crabtree, at each of their respective homes, on 4 December 1639 (24 November under the Julian calendar in use at that time).^[180]

The atmosphere of Venus was discovered in 1761 by Russian polymath Mikhail Lomonosov.^[181][182] Venus’s atmosphere was observed in 1790 by German astronomer Johann Schröter. Schröter found when the planet was a thin crescent, the cusps extended through more than 180°. He correctly surmised this was due to scattering of sunlight in a dense atmosphere. Later, American astronomer Chester Smith Lyman observed a complete ring around the dark side of the planet when it was at inferior conjunction, providing further evidence for an atmosphere.^[183] The atmosphere complicated efforts to determine a rotation period for the planet, and observers such as Italian-born astronomer Giovanni Cassini and Schröter incorrectly estimated periods of about 24 h from the motions of markings on the planet’s apparent surface.^[184]

Ground-based research

Little more was discovered about Venus until the 20th century. Its almost featureless disc gave no hint what its surface might be like, and it was only with the development of spectroscopic, radar and ultraviolet observations that more of its secrets were revealed. The first ultraviolet observations were carried out in the 1920s, when Frank E. Ross found that ultraviolet photographs revealed considerable detail that was absent in visible and infrared radiation. He suggested this was due to a dense, yellow lower atmosphere with high cirrus clouds above it.^[185]

Spectroscopic observations in the 1900s gave the first clues about the Venusian rotation. Vesto Slipher tried to measure the Doppler shift of light from Venus, but found he could not detect any rotation. He surmised the planet must have a much longer rotation period than had previously been thought.^[186] Later work in the 1950s showed the rotation was retrograde. Radar observations of Venus were first carried out in the 1960s, and provided the first measurements of the rotation period, which were close to the modern value.^[187]

Radar observations in the 1970s revealed details of the Venusian surface for the first time. Pulses of radio waves were beamed at the planet using the 300 m (1,000 ft) radio telescope at Arecibo Observatory, and the echoes revealed two highly reflective regions, designated the Alpha and Beta regions. The observations also revealed a bright region attributed to mountains, which was called Maxwell Montes.^[188] These three features are now the only ones on Venus that do not have female names.^[87]

Exploration

The first robotic space probe mission to Venus and any planet was Venera 1 of the Soviet Venera program launched in 1961, though it lost contact en route.^[189]

The first successful mission to Venus (as well as the world’s first successful interplanetary mission) was the Mariner 2 mission by the United States, passing on 14 December 1962 at 34,833 km (21,644 mi) above the surface of Venus and gathering data on the planet’s atmosphere.^[190][191]

On 18 October 1967, the Soviet Venera 4 successfully entered as the first to probe the atmosphere and deployed science experiments. Venera 4 showed the surface temperature was hotter than Mariner 2 had calculated, at almost 500 °C (932 °F), determined that the atmosphere was 95% carbon dioxide (CO
₂), and discovered that Venus’s atmosphere was considerably denser than Venera 4‘s designers had anticipated.^[192] The joint Venera 4–Mariner 5 data were analysed by a combined Soviet–American science team in a series of colloquia over the following year,^[193] in an early example of space cooperation.^[194]

On 15 December 1970, Venera 7 became the first spacecraft to soft land on another planet and the first to transmit data from there back to Earth.^[195]

In 1974, Mariner 10 swung by Venus to bend its path toward Mercury and took ultraviolet photographs of the clouds, revealing the extraordinarily high wind speeds in the Venusian atmosphere. This was the first interplanetary gravity assist ever used, a technique which would be used by later probes, most notably Voyager 1 and 2.

In 1975, the Soviet Venera 9 and 10 landers transmitted the first images from the surface of Venus, which were in black and white. In 1982 the first colour images of the surface were obtained with the Soviet Venera 13 and 14 landers.

NASA obtained additional data in 1978 with the Pioneer Venus project that consisted of two separate missions:^[196] Pioneer Venus Orbiter and Pioneer Venus Multiprobe.^[197] The successful Soviet Venera program came to a close in October 1983, when Venera 15 and 16 were placed in orbit to conduct detailed mapping of 25% of Venus’s terrain (from the north pole to 30°N latitude)^[198]

Several other missions explored Venus in the 1980s and 1990s, including Vega 1 (1985), Vega 2 (1985), Galileo (1990), Magellan (1994), Cassini–Huygens (1998), and MESSENGER (2006). All except Magellan were gravity assists. Then, Venus Express by the European Space Agency (ESA) entered orbit around Venus in April 2006. Equipped with seven scientific instruments, Venus Express provided unprecedented long-term observation of Venus’s atmosphere. ESA concluded the Venus Express mission in December 2014.^[199]

As of 2020, Japan’s Akatsuki is in a highly eccentric orbit around Venus since 7 December 2015, and there are several probing proposals under study by Roscosmos, NASA, ISRO, ESA, and the private sector (e.g. by Rocketlab).

In culture

Venus is a primary feature of the night sky, and so has been of remarkable importance in mythology, astrology and fiction throughout history and in different cultures.

In Sumerian religion, Inanna was associated with the planet Venus.^[202][203] Several hymns praise Inanna in her role as the goddess of the planet Venus.^{[164][203][202]} Theology professor Jeffrey Cooley has argued that, in many myths, Inanna’s movements may correspond with the movements of the planet Venus in the sky.^[164] The discontinuous movements of Venus relate to both mythology as well as Inanna’s dual nature.^[164] In Inanna’s Descent to the Underworld, unlike any other deity, Inanna is able to descend into the netherworld and return to the heavens. The planet Venus appears to make a similar descent, setting in the West and then rising again in the East.^[164] An introductory hymn describes Inanna leaving the heavens and heading for Kur, what could be presumed to be, the mountains, replicating the rising and setting of Inanna to the West.^[164] In Inanna and Shukaletuda and Inanna’s Descent into the Underworld appear to parallel the motion of the planet Venus.^[164] In Inanna and Shukaletuda, Shukaletuda is described as scanning the heavens in search of Inanna, possibly searching the eastern and western horizons.^[204] In the same myth, while searching for her attacker, Inanna herself makes several movements that correspond with the movements of Venus in the sky.^[164]

Classical poets such as Homer, Sappho, Ovid and Virgil spoke of the star and its light.^[205] Poets such as William Blake, Robert Frost, Letitia Elizabeth Landon, Alfred Lord Tennyson and William Wordsworth wrote odes to it.^[206]

In Chinese the planet is called Jīn-xīng (金星), the golden planet of the metal element. In India Shukra Graha («the planet Shukra») is named after the powerful saint Shukra. Shukra which is used in Indian Vedic astrology^[207] means «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.^[208] The word Shukra is also associated with semen, or generation. Venus is known as Kejora in Indonesian and Malaysian Malay. Modern Chinese, Japanese, Korean and Vietnamese cultures refer to the planet literally as the «metal star» (金星), based on the Five elements.^{[209][210][211][212]}

The Maya considered Venus to be the most important celestial body after the Sun and Moon. They called it Chac ek,^[213] or Noh Ek‘, «the Great Star».^[214] The cycles of Venus were important to their calendar and were described in some of their books such as Maya Codex of Mexico and Dresden Codex.

The Ancient Egyptians and Greeks believed Venus to be two separate bodies, a morning star and an evening star. The Egyptians knew the morning star as Tioumoutiri and the evening star as Ouaiti.^[215] The Greeks used the names Phōsphoros (Φωσϕόρος), meaning «light-bringer» (whence the element phosphorus; alternately Ēōsphoros (Ἠωσϕόρος), meaning «dawn-bringer»), for the morning star, and Hesperos (Ἕσπερος), meaning «Western one», for the evening star.^[216] Though by the Roman era they were recognized as one celestial object, known as «the star of Venus», the traditional two Greek names continued to be used, though usually translated to Latin as Lūcifer and Vesper.^[216][217]

Modern fiction

With the invention of the telescope, the idea that Venus was a physical world and possible destination began to take form.

The impenetrable Venusian cloud cover gave science fiction writers free rein to speculate on conditions at its surface; all the more so when early observations showed that not only was it similar in size to Earth, it possessed a substantial atmosphere. Closer to the Sun than Earth, the planet was frequently depicted as warmer, but still habitable by humans.^[218] The genre reached its peak between the 1930s and 1950s, at a time when science had revealed some aspects of Venus, but not yet the harsh reality of its surface conditions. Findings from the first missions to Venus showed the reality to be quite different and brought this particular genre to an end.^[219] As scientific knowledge of Venus advanced, science fiction authors tried to keep pace, particularly by conjecturing human attempts to terraform Venus.^[220]

Symbol

The astronomical symbol for Venus is the same as that used in biology for the female sex: a circle with a small cross beneath.^[221][222] The Venus symbol also represents femininity, and in Western alchemy stood for the metal copper.^[221][222] Polished copper has been used for mirrors from antiquity, and the symbol for Venus has sometimes been understood to stand for the mirror of the goddess although that is unlikely to be its true origin.^[221][222] In the Greek Papyrus Oxyrhynchus 235, the symbols for Venus and Mercury didn’t have the cross-bar on the bottom stroke.^[223]

Venus has also been identified as the star in a range of star and crescent depictions and symbols.

Habitability

Speculation on the possibility of life on Venus’s surface decreased significantly after the early 1960s when it became clear that the conditions are extreme compared to those on Earth. Venus’s extreme temperature and atmospheric pressure make water-based life as currently known unlikely.

Some scientists have speculated that thermoacidophilic extremophile microorganisms might exist in the cooler, acidic upper layers of the Venusian atmosphere).^{[224][225][226]} Such speculations go back to 1967, when Carl Sagan and Harold J. Morowitz suggested in a Nature article that tiny objects detected in Venus’s clouds might be organisms similar to Earth’s bacteria (which are of approximately the same size):

While the surface conditions of Venus make the hypothesis of life there implausible, the clouds of Venus are a different story altogether. As was pointed out some years ago, water, carbon dioxide and sunlight—the prerequisites for photosynthesis—are plentiful in the vicinity of the clouds.^[227]

In August 2019, astronomers led by Yeon Joo Lee reported that long-term pattern of absorbance and albedo changes in the atmosphere of the planet Venus caused by «unknown absorbers», which may be chemicals or even large colonies of microorganisms high up in the atmosphere of the planet, affect the climate.^[61] Their light absorbance is almost identical to that of micro-organisms in Earth’s clouds. Similar conclusions have been reached by other studies.^[228]

In September 2020, a team of astronomers led by Jane Greaves from Cardiff University announced the likely detection of phosphine, a gas not known to be produced by any known chemical processes on the Venusian surface or atmosphere, in the upper levels of the planet’s clouds.^{[229][230][231][232][233]} One proposed source for this phosphine is living organisms.^[234] The phosphine was detected at heights of at least 30 miles above the surface, and primarily at mid-latitudes with none detected at the poles. The discovery prompted NASA administrator Jim Bridenstine to publicly call for a new focus on the study of Venus, describing the phosphine find as «the most significant development yet in building the case for life off Earth».^[235][236]

Subsequent analysis of the data-processing used to identify phosphine in the atmosphere of Venus has raised concerns that the detection-line may be an artefact. The use of a 12th-order polynomial fit may have amplified noise and generated a false reading (see Runge’s phenomenon). Observations of the atmosphere of Venus at other parts of the electromagnetic spectrum in which a phosphine absorption line would be expected did not detect phosphine.^[237] By late October 2020, re-analysis of data with a proper subtraction of background did not show a statistically significant detection of phosphine.^{[238][239][240]}

Planetary protection

The Committee on Space Research is a scientific organization established by the International Council for Science. Among their responsibilities is the development of recommendations for avoiding interplanetary contamination. For this purpose, space missions are categorized into five groups. Due to the harsh surface environment of Venus, Venus has been under the planetary protection category two.^[241] This indicates that there is only a remote chance that spacecraft-borne contamination could compromise investigations.

Human presence

Venus is the place of the very first interplanetary human presence, mediated through robotic missions, with the first successful landings on another planet and extraterrestrial body other than the Moon. Venus was at the beginning of the space age frequently visited by space probes until the 1990s. Currently in orbit is Akatsuki, and the Parker Solar Probe routinely uses Venus for gravity assist maneuvers.^[242]

The only nation that has sent lander probes to the surface of Venus has been the Soviet Union,^[a] which has been used by Russian officials to call Venus a «Russian planet».^[243][244]

Habitation

While the surface conditions of Venus are very inhospitable, the atmospheric pressure and temperature 50 km above the surface are similar to those at Earth’s surface. With this in mind, Soviet engineer Sergey Zhitomirskiy (Сергей Житомирский, 1929–2004) in 1971^[245][246] and more contemporarily NASA aerospace engineer Geoffrey A. Landis in 2003^[247] suggested the use of aerostats for crewed exploration and possibly for permanent «floating cities» in the Venusian atmosphere, an alternative to the popular idea of living on planetary surfaces such as Mars.^[248][249] Among the many engineering challenges for any human presence in the atmosphere of Venus are the corrosive amounts of sulfuric acid in the atmosphere.^[247]

NASA’s High Altitude Venus Operational Concept is a mission concept that proposed a crewed aerostat design.

See also

• Geodynamics of Venus
• Outline of Venus
• Venus zone
• Stats of planets in the Solar System

Notes

References

External links

• Venus profile at NASA’s Solar System Exploration site
• Missions to Venus and Image catalog at the National Space Science Data Center
• Soviet Exploration of Venus and Image catalog at Mentallandscape.com
• Image catalog from the Venera missions
• Venus page at The Nine Planets
• Transits of Venus at NASA.gov
• Geody Venus, a search engine for surface features
• Interactive 3D gravity simulation of the pentagram that the orbit of Venus traces when Earth is held fixed at the centre of the coordinate system

Cartographic resources

• Map-a-Planet: Venus by the U.S. Geological Survey
• Gazetteer of Planetary Nomenclature: Venus by the International Astronomical Union
• Venus crater database by the Lunar and Planetary Institute
• Map of Venus by Eötvös Loránd University
• Google Venus 3D, interactive map of the planet

Venus

Near-global view of Venus in natural colour, taken by the MESSENGER space probe
Designations
Pronunciation	(listen)
Named after	Venus
Adjectives	Venusian ,[1] rarely Cytherean [2] or Venerean / Venerian [3]
Orbital characteristics[5][7]
Epoch J2000
Aphelion	0.728213 AU 108,939,000 km
Perihelion	0.718440 AU 107,477,000 km
Semi-major axis	0.723332 AU 108,208,000 km
Eccentricity	0.006772[4]
Orbital period (sidereal)	224.701 d[5] 0.615198 yr 1.92 Venus solar day
Orbital period (synodic)	583.92 days[5]
Average orbital speed	35.02 km/s
Mean anomaly	50.115°
Inclination	3.39458° to ecliptic 3.86° to Sun’s equator 2.15° to invariable plane[6]
Longitude of ascending node	76.680°[4]
Argument of perihelion	54.884°
Satellites	None
Physical characteristics
Mean radius	6,051.8±1.0 km[8] 0.9499 Earths
Flattening	0[8]
Surface area	4.6023×108 km2 0.902 Earths
Volume	9.2843×1011 km3 0.857 Earths
Mass	4.8675×1024 kg[9] 0.815 Earths
Mean density	5.243 g/cm3
Surface gravity	8.87 m/s2 0.904 g
Escape velocity	10.36 km/s (6.44 mi/s)[10]
Synodic rotation period	−116.75 d (retrograde)[11] 1 Venus solar day
Sidereal rotation period	−243.0226 d (retrograde)[12]
Equatorial rotation velocity	6.52 km/h (1.81 m/s)
Axial tilt	2.64° (for retrograde rotation) 177.36° (to orbit)[5][note 1]
North pole right ascension	18h 11m 2s 272.76°[13]
North pole declination	67.16°
Albedo	0.689 (geometric)[14] 0.76 (Bond)[15]
Temperature	232 K (−41 °C) (blackbody temperature)[16]
Surface temp. min mean max Kelvin 737 K[5] Celsius 464 °C Fahrenheit 867 °F
Surface absorbed dose rate	2.1×10−6 μGy/h[18]
Surface equivalent dose rate	2.2×10−6 μSv/h 0.092–22 μSv/h at the habitable zone[18]
Apparent magnitude	−4.92 to −2.98[17]
Angular diameter	9.7″–66.0″[5]
Atmosphere[5]
Surface pressure	93 bar (9.3 MPa) 92 atm
Composition by volume	96.5% carbon dioxide 3.5% nitrogen 0.015% sulfur dioxide 0.0070% argon 0.0020% water vapour 0.0017% carbon monoxide 0.0012% helium 0.0007% neon Trace carbonyl sulfide Trace hydrogen chloride Trace hydrogen fluoride
^ Defining the rotation as retrograde, as done by NASA space missions and the USGS, puts Ishtar Terra in the northern hemisphere and makes the axial tilt 2.64°. Following the right-hand rule for prograde rotation puts Ishtar Terra in the southern hemisphere and makes the axial tilt 177.36°.

Venus is the second planet from the Sun. It is sometimes called Earth’s «sister» or «twin» planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth’s sky never far from the Sun, either as morning star or evening star. Aside from the Sun and Moon, Venus is the brightest natural object in Earth’s sky, capable of casting visible shadows on Earth at dark conditions and being visible to the naked eye in broad daylight.^[19][20]

Venus is the second largest terrestrial object of the Solar System. It has a surface gravity slightly lower than on Earth and has a very weak induced magnetosphere. The atmosphere of Venus consists mainly of carbon dioxide, and, at the planet’s surface, is the densest and hottest of the atmospheres of the four terrestrial planets. With an atmospheric pressure at the planet’s surface of about 92 times the sea level pressure of Earth and a mean temperature of 737 K (464 °C; 867 °F), the carbon dioxide gas at Venus’s surface is in the supercritical phase of matter. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, making it the planet with the highest albedo in the Solar System. It may have had water oceans in the past,^[21][22] but after these evaporated the temperature rose under a runaway greenhouse effect.^[23] The possibility of life on Venus has long been a topic of speculation but convincing evidence has yet to be found.

Like Mercury, Venus does not have any moons.^[24] Solar days on Venus, with a length of 117 Earth days,^[25] are just about half as long as its solar year, orbiting the Sun every 224.7 Earth days.^[26] This Venusian daylength is a product of it rotating against its orbital motion, halving its full sidereal rotation period of 243 Earth days, the longest of all the Solar System planets. Venus and Uranus are the only planets with such a retrograde rotation, making the Sun move in their skies from their western horizon to their eastern. The orbit of Venus around the Sun is the closest to Earth’s orbit, bringing them closer than any other pair of planets. This occurs during inferior conjunction with a synodic period of 1.6 years. However, Mercury is more frequently the closest to each.

The orbits of Venus and Earth result in the lowest gravitational potential difference and lowest delta-v needed to transfer between them than to any other planet. This has made Venus a prime target for early interplanetary exploration. It was the first planet beyond Earth that spacecraft were sent to, starting with Venera 1 in 1961, and the first planet to be reached, impacted and in 1970 successfully landed on by Venera 7. As one of the brightest objects in the sky, Venus has been a major fixture in human culture for as long as records have existed. It has been made sacred to gods of many cultures, gaining its mainly used name from the Roman goddess of love and beauty which it is associated with. Furthermore it has been a prime inspiration for writers, poets and scholars. Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BCE.^[27] Plans for better exploration with rovers or atmospheric missions, potentially crewed, at levels with almost Earth-like conditions have been proposed.

Physical characteristics

Venus is one of the four terrestrial planets in the Solar System, meaning that it is a rocky body like Earth. It is similar to Earth in size and mass and is often described as Earth’s «sister» or «twin».^[28] The diameter of Venus is 12,103.6 km (7,520.8 mi)—only 638.4 km (396.7 mi) less than Earth’s—and its mass is 81.5% of Earth’s. Conditions on the Venusian surface differ radically from those on Earth because its dense atmosphere is 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen.^[29] The surface pressure is 9.3 megapascals (93 bars), and the average surface temperature is 737 K (464 °C; 867 °F), above the critical points of both major constituents and making the surface atmosphere a supercritical fluid.

Atmosphere and climate

Venus has an extremely dense atmosphere composed of 96.5% carbon dioxide, 3.5% nitrogen—both exist as supercritical fluids at the planet’s surface—and traces of other gases including sulfur dioxide.^[30] The mass of its atmosphere is 92 times that of Earth’s, whereas the pressure at its surface is about 93 times that at Earth’s—a pressure equivalent to that at a depth of nearly 1 km (5⁄8 mi) under Earth’s oceans. The density at the surface is 65 kg/m³ (4.1 lb/cu ft), 6.5% that of water or 50 times as dense as Earth’s atmosphere at 293 K (20 °C; 68 °F) at sea level. The CO₂-rich atmosphere generates the strongest greenhouse effect in the Solar System, creating surface temperatures of at least 735 K (462 °C; 864 °F).^[26][31] This makes the Venusian surface hotter than Mercury’s, which has a minimum surface temperature of 53 K (−220 °C; −364 °F) and maximum surface temperature of 700 K (427 °C; 801 °F),^[32][33] even though Venus is nearly twice Mercury’s distance from the Sun and thus receives only 25% of Mercury’s solar irradiance. Because of its runaway greenhouse effect, Venus has been identified by scientists such as Carl Sagan as a warning and research object linked to climate change on Earth.^[34]

Venus Temperature^[35]

Type	Surface Temperature
Maximum	900 °F (482 °C)
Normal	847 °F (453 °C)
Minimum	820 °F (438 °C)

Venus’s atmosphere is extremely rich in primordial noble gases compared to that of Earth.^[36] This enrichment indicates an early divergence from Earth in evolution. An unusually large comet impact^[37] or accretion of a more massive primary atmosphere from solar nebula^[38] have been proposed to explain the enrichment. However, the atmosphere is also depleted of radiogenic argon, a proxy to mantle degassing, suggesting an early shutdown of major magmatism.^[39][40]

Studies^[which?] have suggested that billions of years ago, Venus’s atmosphere could have been much more like the one surrounding the early Earth, and that there may have been substantial quantities of liquid water on the surface. After a period of 600 million to several billion years,^[41] solar forcing from rising luminosity of the Sun caused the evaporation of the original water. A runaway greenhouse effect was created once a critical level of greenhouse gases (including water) was added to its atmosphere.^[42] Although the surface conditions on Venus are no longer hospitable to any Earth-like life that may have formed before this event, there is speculation on the possibility that life exists in the upper cloud layers of Venus, 50 km (30 mi) up from the surface, where the temperature ranges between 303 and 353 K (30 and 80 °C; 86 and 176 °F) but the environment is acidic.^[43][44][45] The putative detection of an absorption line of phosphine in Venus’s atmosphere, with no known pathway for abiotic production, led to speculation in September 2020 that there could be extant life currently present in the atmosphere.^[46][47] Later research attributed the spectroscopic signal that was interpreted as phosphine to sulfur dioxide,^[48] or found that in fact there was no absorption line.^[49][50]

Thermal inertia and the transfer of heat by winds in the lower atmosphere mean that the temperature of Venus’s surface does not vary significantly between the planet’s two hemispheres, those facing and not facing the Sun, despite Venus’s extremely slow rotation. Winds at the surface are slow, moving at a few kilometres per hour, but because of the high density of the atmosphere at the surface, they exert a significant amount of force against obstructions, and transport dust and small stones across the surface. This alone would make it difficult for a human to walk through, even without the heat, pressure, and lack of oxygen.^[51]

Above the dense CO₂ layer are thick clouds, consisting mainly of sulfuric acid, which is formed by sulfur dioxide and water through a chemical reaction resulting in sulfuric acid hydrate. Additionally, the clouds consist of approximately 1% ferric chloride.^[52][53] Other possible constituents of the cloud particles are ferric sulfate, aluminium chloride and phosphoric anhydride. Clouds at different levels have different compositions and particle size distributions.^[52] These clouds reflect and scatter about 90% of the sunlight that falls on them back into space, and prevent visual observation of Venus’s surface. The permanent cloud cover means that although Venus is closer than Earth to the Sun, it receives less sunlight on the ground. Strong 300 km/h (185 mph) winds at the cloud tops go around Venus about every four to five Earth days.^[54] Winds on Venus move at up to 60 times the speed of its rotation, whereas Earth’s fastest winds are only 10–20% rotation speed.^[55]

The surface of Venus is effectively isothermal; it retains a constant temperature not only between the two hemispheres but between the equator and the poles.^[5][56] Venus’s minute axial tilt—less than 3°, compared to 23° on Earth—also minimises seasonal temperature variation.^[57] Altitude is one of the few factors that affect Venusian temperature. The highest point on Venus, Maxwell Montes, is therefore the coolest point on Venus, with a temperature of about 655 K (380 °C; 715 °F) and an atmospheric pressure of about 4.5 MPa (45 bar).^[58][59] In 1995, the Magellan spacecraft imaged a highly reflective substance at the tops of the highest mountain peaks that bore a strong resemblance to terrestrial snow. This substance likely formed from a similar process to snow, albeit at a far higher temperature. Too volatile to condense on the surface, it rose in gaseous form to higher elevations, where it is cooler and could precipitate. The identity of this substance is not known with certainty, but speculation has ranged from elemental tellurium to lead sulfide (galena).^[60]

Although Venus has no seasons as such, in 2019, astronomers identified a cyclical variation in sunlight absorption by the atmosphere, possibly caused by opaque, absorbing particles suspended in the upper clouds. The variation causes observed changes in the speed of Venus’s zonal winds and appears to rise and fall in time with the Sun’s 11-year sunspot cycle.^[61]

The existence of lightning in the atmosphere of Venus has been controversial^[62] since the first suspected bursts were detected by the Soviet Venera probes.^[63][64][65] In 2006–07, Venus Express clearly detected whistler mode waves, the signatures of lightning. Their intermittent appearance indicates a pattern associated with weather activity. According to these measurements, the lightning rate is at least half of that on Earth,^[66] however other instruments have not detected lightning at all.^[62] The origin of any lightning remains unclear, but could originate from the clouds or volcanoes.

In 2007, Venus Express discovered that a huge double atmospheric vortex exists at the south pole.^[67][68] Venus Express also discovered, in 2011, that an ozone layer exists high in the atmosphere of Venus.^[69] On 29 January 2013, ESA scientists reported that the ionosphere of Venus streams outwards in a manner similar to «the ion tail seen streaming from a comet under similar conditions.»^[70][71]

In December 2015, and to a lesser extent in April and May 2016, researchers working on Japan’s Akatsuki mission observed bow shapes in the atmosphere of Venus. This was considered direct evidence of the existence of perhaps the largest stationary gravity waves in the solar system.^[72][73][74]

Geography

The Venusian surface was a subject of speculation until some of its secrets were revealed by planetary science in the 20th century. Venera landers in 1975 and 1982 returned images of a surface covered in sediment and relatively angular rocks.^[77] The surface was mapped in detail by Magellan in 1990–91. The ground shows evidence of extensive volcanism, and the sulfur in the atmosphere may indicate that there have been recent eruptions.^[78][79]

About 80% of the Venusian surface is covered by smooth, volcanic plains, consisting of 70% plains with wrinkle ridges and 10% smooth or lobate plains.^[80] 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. Its peak is 11 km (7 mi) above the Venusian average surface elevation.^[81] 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.^[82]

The absence of evidence of lava flow accompanying any of the visible calderas remains an enigma. The planet has few impact craters, demonstrating that the surface is relatively young, at 300–600 million years old.^[83][84] Venus has some unique surface features in addition to the impact craters, mountains, and valleys commonly found on rocky planets. Among these are flat-topped volcanic features called «farra», which look somewhat like pancakes and range in size from 20 to 50 km (12 to 31 mi) across, and from 100 to 1,000 m (330 to 3,280 ft) 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.^[85]

Most Venusian surface features are named after historical and mythological women.^[86] Exceptions are Maxwell Montes, named after James Clerk Maxwell, and highland regions Alpha Regio, Beta Regio, and Ovda Regio. The last three features were named before the current system was adopted by the International Astronomical Union, the body which oversees planetary nomenclature.^[87]

The longitude of physical features on Venus are expressed relative to its prime meridian. The original prime meridian passed through the radar-bright spot at the centre of the oval feature Eve, located south of Alpha Regio.^[88] After the Venera missions were completed, the prime meridian was redefined to pass through the central peak in the crater Ariadne on Sedna Planitia.^[89][90]

The stratigraphically oldest tessera terrains have consistently lower thermal emissivity than the surrounding basaltic plains measured by Venus Express and Magellan, indicating a different, possibly a more felsic, mineral assemblage.^[21][91] The mechanism to generate a large amount of felsic crust usually requires the presence of water ocean and plate tectonics, implying that habitable condition had existed on early Venus. However, the nature of tessera terrains is far from certain.^[92]

Volcanism

Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it has 167 large volcanoes that are over 100 km (60 mi) across. The only volcanic complex of this size on Earth is the Big Island of Hawaii.^[85]: 154 This is not because Venus is more volcanically active than Earth, but because its crust is older and is not subject to the same erosion process. Earth’s oceanic crust is continually recycled by subduction at the boundaries of tectonic plates, and has an average age of about a hundred million years,^[93] whereas the Venusian surface is estimated to be 300–600 million years old.^[83][85]

Several lines of evidence point to ongoing volcanic activity on Venus. Sulfur dioxide concentrations in the atmosphere dropped by a factor of 10 between 1978 and 1986, jumped in 2006, and again declined 10-fold.^[94] This may mean that levels had been boosted several times by large volcanic eruptions.^[95][96] It has also been suggested that Venusian lightning (discussed below) could originate from volcanic activity (i.e. volcanic lightning). In January 2020, astronomers reported evidence that suggests that Venus is currently volcanically active, specifically the detection of olivine, a volcanic product that would weather quickly on the planet’s surface.^[97][98]

In 2008 and 2009, the first direct evidence for ongoing volcanism was observed by Venus Express, in the form of four transient localized infrared hot spots within the rift zone Ganis Chasma,^{[99][n 1]} near the shield volcano Maat Mons. Three of the spots were observed in more than one successive orbit. These spots are thought to represent lava freshly released by volcanic eruptions.^[100][101] The actual temperatures are not known, because the size of the hot spots could not be measured, but are likely to have been in the 800–1,100 K (527–827 °C; 980–1,520 °F) range, relative to a normal temperature of 740 K (467 °C; 872 °F).^[102]

Craters

Almost a thousand impact craters on Venus are evenly distributed across its surface. On other cratered bodies, such as Earth and the Moon, craters show a range of states of degradation. On the Moon, degradation is caused by subsequent impacts, whereas on Earth it is caused by wind and rain erosion. On Venus, about 85% of the craters are in pristine condition. The number of craters, together with their well-preserved condition, indicates the planet underwent a global resurfacing event 300–600 million years ago,^[83][84] followed by a decay in volcanism.^[103] Whereas Earth’s crust is in continuous motion, Venus is thought to be unable to 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.^[85]

Venusian craters range from 3 to 280 km (2 to 174 mi) in diameter. No craters are smaller than 3 km, because of the effects of the dense atmosphere on incoming objects. Objects with less than a certain kinetic energy are slowed so much by the atmosphere that they do not create an impact crater.^[104] Incoming projectiles less than 50 m (160 ft) in diameter will fragment and burn up in the atmosphere before reaching the ground.^[105]

Internal structure

Without seismic data or knowledge of its moment of inertia, little direct information is available about the internal structure and geochemistry of Venus.^[106] The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust. Like that of Earth, the Venusian core is most likely at least partially liquid because the two planets have been cooling at about the same rate,^[107] although a completely solid core cannot be ruled out.^[108] The slightly smaller size of Venus means pressures are 24% lower in its deep interior than Earth’s.^[109] The predicted values for the moment of inertia based on planetary models suggest a core radius of 2,900–3,450 km.^[108] This is in line with the first observation-based estimate of 3,500 km.^[110]

The principal difference between the two planets is the lack of evidence for plate tectonics on Venus, possibly because its crust is too strong to subduct without water to make it less viscous. 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.^[111]
Instead, Venus may lose its internal heat in periodic major resurfacing events.^[83]

Magnetic field and core

In 1967, Venera 4 found Venus’s magnetic field to be much weaker than that of Earth. This magnetic field is induced by an interaction between the ionosphere and the solar wind,^[112][113] rather than by an internal dynamo as in the Earth’s core. Venus’s small induced magnetosphere provides negligible protection to the atmosphere against cosmic radiation.

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, although its rotation is often thought to be too slow, simulations show it is adequate to produce a dynamo.^[114][115] This implies that the dynamo is missing because of a lack of convection in Venus’s core. On Earth, convection occurs in the liquid outer layer of the core because the bottom of the liquid layer is much higher in temperature 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 insulating effect would cause the mantle temperature to increase, thereby reducing the heat flux out of the core. As a result, no internal geodynamo is available to drive a magnetic field. Instead, the heat from the core is reheating the crust.^[116]

One possibility is that Venus has no solid inner core,^[117] or that its core is not 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.^[116]

The weak magnetosphere around Venus means that the solar wind is interacting directly with its outer atmosphere. Here, ions of hydrogen and oxygen are being created by the dissociation of water molecules from ultraviolet radiation. The solar wind then supplies energy that gives some of these ions sufficient velocity to escape Venus’s gravity field. This erosion process results in a steady loss of low-mass hydrogen, helium, and oxygen ions, whereas higher-mass molecules, such as carbon dioxide, are more likely to be retained. Atmospheric erosion by the solar wind could have led to the loss of most of Venus’s water during the first billion years after it formed.^[118] However, the planet may have retained a dynamo for its first 2–3 billion years, so the water loss may have occurred more recently.^[119] The erosion has increased the ratio of higher-mass deuterium to lower-mass hydrogen in the atmosphere 100 times compared to the rest of the solar system.^[120]

Orbit and rotation

Venus orbits the Sun at an average distance of about 0.72 AU (108 million km; 67 million mi), and completes an orbit every 224.7 days. Although all planetary orbits are elliptical, Venus’s orbit is currently the closest to circular, with an eccentricity of less than 0.01.^[5] Simulations of the early solar system orbital dynamics have shown that the eccentricity of the Venus orbit may have been substantially larger in the past, reaching values as high as 0.31 and possibly impacting the early climate evolution.^[121] The current near-circular orbit of Venus means that when Venus lies between Earth and the Sun in inferior conjunction, it makes the closest approach to Earth of any planet at an average distance of 41 million km (25 million mi).^{[5][n 2][122]}
The planet reaches at a orbital resonance of 8 Earth orbits to 13 Venus orbits,^[123] inferior conjunctions at a synodic period of 584 days, on average.^[5] Because of the decreasing eccentricity of Earth’s orbit, the minimum distances will become greater over tens of thousands of years. From the year 1 to 5383, there are 526 approaches less than 40 million km (25 million mi); then, there are none for about 60,158 years.^[124] While Venus approaches Earth the closest, Mercury approaches Earth more often the closest of all planets.^[125] That said, Venus and Earth still have the lowest gravitational potential difference between them than to any other planet, needing the lowest delta-v to transfer between them, than to any other planet from them.^[126][127]

All the planets in the Solar System orbit the Sun in an anticlockwise direction as viewed from above Earth’s north pole. Most planets also rotate on their axes in an anticlockwise direction, but Venus rotates clockwise in retrograde rotation once every 243 Earth days—the slowest rotation of any planet. Because its rotation is so slow, Venus is very close to spherical.^[128] A Venusian sidereal day thus lasts longer than a Venusian year (243 versus 224.7 Earth days). Venus’s equator rotates at 6.52 km/h (4.05 mph), whereas Earth’s rotates at 1,674.4 km/h (1,040.4 mph).^[132][133] Venus’s rotation period measured with Magellan spacecraft data over a 500-day period is smaller than the rotation period measured during the 16-year period between the Magellan spacecraft and Venus Express visits, with a difference of about 6.5 minutes.^[134] Because of the retrograde rotation, the length of a solar day on Venus is significantly shorter than the sidereal day, at 116.75 Earth days (making the Venusian solar day shorter than Mercury’s 176 Earth days — the 116-day figure is extremely close to the average number of days it takes Mercury to slip underneath the Earth in its orbit).^[11] One Venusian year is about 1.92 Venusian solar days.^[135] To an observer on the surface of Venus, the Sun would rise in the west and set in the east,^[135] although Venus’s opaque clouds prevent observing the Sun from the planet’s surface.^[136]

Venus may have formed from the solar nebula with a different rotation period and obliquity, reaching its current state because of chaotic spin changes caused by planetary perturbations and tidal effects on its dense atmosphere, a change that would have occurred over the course of billions of years. The rotation period of Venus may represent an equilibrium state between tidal locking to the Sun’s gravitation, which tends to slow rotation, and an atmospheric tide created by solar heating of the thick Venusian atmosphere.^[137][138]
The 584-day average interval between successive close approaches to Earth is almost exactly equal to 5 Venusian solar days (5.001444 to be precise),^[139] but the hypothesis of a spin-orbit resonance with Earth has been discounted.^[140]

Venus has no natural satellites.^[141] It has several trojan asteroids: the quasi-satellite 2002 VE68^[142][143] and two other temporary trojans, 2001 CK₃₂ and 2012 XE133.^[144] In the 17th century, Giovanni Cassini reported a moon orbiting Venus, which was named Neith and numerous sightings were reported over the following 200 years, but most were determined to be stars in the vicinity. Alex Alemi’s and David Stevenson’s 2006 study of models of the early Solar System at the California Institute of Technology shows Venus likely had at least one moon created by a huge impact event billions of years ago.^[145] About 10 million years later, according to the study, another impact reversed the planet’s spin direction and caused the Venusian moon gradually to spiral inward until it collided with Venus.^[146] If later impacts created moons, these were removed in the same way. An alternative explanation for the lack of satellites is the effect of strong solar tides, which can destabilize large satellites orbiting the inner terrestrial planets.^[141]

Observability

To the naked eye, Venus appears as a white point of light brighter than any other planet or star (apart from the Sun).^[147] The planet’s mean apparent magnitude is −4.14 with a standard deviation of 0.31.^[17] The brightest magnitude occurs during crescent phase about one month before or after inferior conjunction. Venus fades to about magnitude −3 when it is backlit by the Sun.^[148] The planet is bright enough to be seen in broad daylight,^[149] but is more easily visible when the Sun is low on the horizon or setting. As an inferior planet, it always lies within about 47° of the Sun.^[150]

Venus «overtakes» Earth every 584 days as it orbits the Sun.^[5] As it does so, it changes from the «Evening Star», visible after sunset, to the «Morning Star», visible before sunrise. Although Mercury, the other inferior planet, reaches a maximum elongation of only 28° and is often difficult to discern in twilight, Venus is hard to miss when it is at its brightest. Its greater maximum elongation means it is visible in dark skies long after sunset. As the brightest point-like object in the sky, Venus is a commonly misreported «unidentified flying object».^[151]

Phases

As it orbits the Sun, Venus displays phases like those of the Moon in a telescopic view. The planet appears as a small and «full» disc when it is on the opposite side of the Sun (at superior conjunction). Venus shows a larger disc and «quarter phase» at its maximum elongations from the Sun, and appears its brightest in the night sky. The planet presents a much larger thin «crescent» in telescopic views as it passes along the near side between Earth and the Sun. Venus displays its largest size and «new phase» when it is between Earth and the Sun (at inferior conjunction). Its atmosphere is visible through telescopes by the halo of sunlight refracted around it.^[150] The phases are clearly visible in a 4″ telescope.

Daylight apparitions

Naked-eye observations of Venus during daylight hours exist in several anecdotes and records. Astronomer Edmund Halley calculated its maximum naked eye brightness in 1716, when many Londoners were alarmed by its appearance in the daytime. French emperor Napoleon Bonaparte once witnessed a daytime apparition of the planet while at a reception in Luxembourg.^[152] Another historical daytime observation of the planet took place during the inauguration of the American president Abraham Lincoln in Washington, D.C., on 4 March 1865.^[153] Although naked eye visibility of Venus’s phases is disputed, records exist of observations of its crescent.^[154]

Transits

The Venusian orbit is slightly inclined relative to Earth’s orbit; thus, when the planet passes between Earth and the Sun, it usually does not cross the face of the Sun. Transits of Venus occur when the planet’s inferior conjunction coincides with its presence in the plane of Earth’s orbit. Transits of Venus occur in cycles of 243 years with the current pattern of transits being pairs of transits separated by eight years, at intervals of about 105.5 years or 121.5 years—a pattern first discovered in 1639 by the English astronomer Jeremiah Horrocks.^[155]

The latest pair was June 8, 2004 and June 5–6, 2012. The transit could be watched live from many online outlets or observed locally with the right equipment and conditions.^[156]

The preceding pair of transits occurred in December 1874 and December 1882; the following pair will occur in December 2117 and December 2125.^[157] The 1874 transit is the subject of the oldest film known, the 1874 Passage de Venus. Historically, transits of Venus were important, because they allowed astronomers to determine the size of the astronomical unit, and hence the size of the Solar System as shown by Horrocks in 1639.^[158] Captain Cook’s exploration of the east coast of Australia came after he had sailed to Tahiti in 1768 to observe a transit of Venus.^[159][160]

Pentagram of Venus

The pentagram of Venus is the path that Venus makes as observed from Earth. Successive inferior conjunctions of Venus repeat with a orbital resonance of 13:8 (Earth orbits eight times for every 13 orbits of Venus), shifting 144° upon sequential inferior conjunctions. The 13:8 ratio is approximate. 8/13 is approximately 0.61538 while Venus orbits the Sun in 0.61519 years.^[161] The pentagram of Venus is sometimes also referred to as the petals of Venus due to the path’s visual similarity to a flower.^[162]

Ashen light

A long-standing mystery of Venus observations is the so-called ashen light—an apparent weak illumination of its dark side, seen when the planet is in the crescent phase. The first claimed observation of ashen light was made in 1643, but the existence of the illumination has never been reliably confirmed. Observers have speculated it may result from electrical activity in the Venusian atmosphere, but it could be illusory, resulting from the physiological effect of observing a bright, crescent-shaped object.^[163][64] The ashen light has often been sighted when Venus is in the evening sky, when the evening terminator of the planet is towards to Earth.

Observation and exploration

Early observation

Because the movements of Venus appear to be discontinuous (it disappears due to its proximity to the sun, for many days at a time, and then reappears on the other horizon), some cultures did not recognize Venus as a single entity;^[164] instead, they assumed it to be two separate stars on each horizon: the morning and evening star.^[164] Nonetheless, a cylinder seal from the Jemdet Nasr period and the Venus tablet of Ammisaduqa from the First Babylonian dynasty indicate that the ancient Sumerians already knew that the morning and evening stars were the same celestial object.^{[165][164][166]} In the Old Babylonian period, the planet Venus was known as Ninsi’anna, and later as Dilbat.^[167] The name «Ninsi’anna» translates to «divine lady, illumination of heaven», which refers to Venus as the brightest visible «star». Earlier spellings of the name were written with the cuneiform sign si4 (= SU, meaning «to be red»), and the original meaning may have been «divine lady of the redness of heaven», in reference to the colour of the morning and evening sky.^[168]

The Chinese historically referred to the morning Venus as «the Great White» (Tàibái 太白) or «the Opener (Starter) of Brightness» (Qǐmíng 啟明), and the evening Venus as «the Excellent West One» (Chánggēng 長庚).^[169]

The ancient Greeks also initially believed Venus to be two separate stars: Phosphorus, the morning star, and Hesperus, the evening star. Pliny the Elder credited the realization that they were a single object to Pythagoras in the sixth century BC,^[170] while Diogenes Laërtius argued that Parmenides was probably responsible for this discovery.^[171] Though they recognized Venus as a single object, the ancient Romans continued to designate the morning aspect of Venus as Lucifer, literally «Light-Bringer», and the evening aspect as Vesper,^[172] both of which are literal translations of their traditional Greek names.

In the second century, in his astronomical treatise Almagest, Ptolemy theorized that both Mercury and Venus are located between the Sun and the Earth. The 11th-century Persian astronomer Avicenna claimed to have observed the transit of Venus,^[173] which later astronomers took as confirmation of Ptolemy’s theory.^[174] In the 12th century, the Andalusian astronomer Ibn Bajjah observed «two planets as black spots on the face of the Sun»; these were thought to be the transits of Venus and Mercury by 13th-century Maragha astronomer Qotb al-Din Shirazi, though this cannot be true as there were no Venus transits in Ibn Bajjah’s lifetime.^{[175][n 3]}

When the Italian physicist Galileo Galilei first observed the planet in the early 17th century, he found it showed phases like the Moon, varying from crescent to gibbous to full and vice versa. When Venus is furthest from the Sun in the sky, it shows a half-lit phase, and when it is closest to the Sun in the sky, it shows as a crescent or full phase. This could be possible only if Venus orbited the Sun, and this was among the first observations to clearly contradict the Ptolemaic geocentric model that the Solar System was concentric and centred on Earth.^[178][179]

The 1639 transit of Venus was accurately predicted by Jeremiah Horrocks and observed by him and his friend, William Crabtree, at each of their respective homes, on 4 December 1639 (24 November under the Julian calendar in use at that time).^[180]

The atmosphere of Venus was discovered in 1761 by Russian polymath Mikhail Lomonosov.^[181][182] Venus’s atmosphere was observed in 1790 by German astronomer Johann Schröter. Schröter found when the planet was a thin crescent, the cusps extended through more than 180°. He correctly surmised this was due to scattering of sunlight in a dense atmosphere. Later, American astronomer Chester Smith Lyman observed a complete ring around the dark side of the planet when it was at inferior conjunction, providing further evidence for an atmosphere.^[183] The atmosphere complicated efforts to determine a rotation period for the planet, and observers such as Italian-born astronomer Giovanni Cassini and Schröter incorrectly estimated periods of about 24 h from the motions of markings on the planet’s apparent surface.^[184]

Ground-based research

Little more was discovered about Venus until the 20th century. Its almost featureless disc gave no hint what its surface might be like, and it was only with the development of spectroscopic, radar and ultraviolet observations that more of its secrets were revealed. The first ultraviolet observations were carried out in the 1920s, when Frank E. Ross found that ultraviolet photographs revealed considerable detail that was absent in visible and infrared radiation. He suggested this was due to a dense, yellow lower atmosphere with high cirrus clouds above it.^[185]

Spectroscopic observations in the 1900s gave the first clues about the Venusian rotation. Vesto Slipher tried to measure the Doppler shift of light from Venus, but found he could not detect any rotation. He surmised the planet must have a much longer rotation period than had previously been thought.^[186] Later work in the 1950s showed the rotation was retrograde. Radar observations of Venus were first carried out in the 1960s, and provided the first measurements of the rotation period, which were close to the modern value.^[187]

Radar observations in the 1970s revealed details of the Venusian surface for the first time. Pulses of radio waves were beamed at the planet using the 300 m (1,000 ft) radio telescope at Arecibo Observatory, and the echoes revealed two highly reflective regions, designated the Alpha and Beta regions. The observations also revealed a bright region attributed to mountains, which was called Maxwell Montes.^[188] These three features are now the only ones on Venus that do not have female names.^[87]

Exploration

The first robotic space probe mission to Venus and any planet was Venera 1 of the Soviet Venera program launched in 1961, though it lost contact en route.^[189]

The first successful mission to Venus (as well as the world’s first successful interplanetary mission) was the Mariner 2 mission by the United States, passing on 14 December 1962 at 34,833 km (21,644 mi) above the surface of Venus and gathering data on the planet’s atmosphere.^[190][191]

On 18 October 1967, the Soviet Venera 4 successfully entered as the first to probe the atmosphere and deployed science experiments. Venera 4 showed the surface temperature was hotter than Mariner 2 had calculated, at almost 500 °C (932 °F), determined that the atmosphere was 95% carbon dioxide (CO
₂), and discovered that Venus’s atmosphere was considerably denser than Venera 4‘s designers had anticipated.^[192] The joint Venera 4–Mariner 5 data were analysed by a combined Soviet–American science team in a series of colloquia over the following year,^[193] in an early example of space cooperation.^[194]

On 15 December 1970, Venera 7 became the first spacecraft to soft land on another planet and the first to transmit data from there back to Earth.^[195]

In 1974, Mariner 10 swung by Venus to bend its path toward Mercury and took ultraviolet photographs of the clouds, revealing the extraordinarily high wind speeds in the Venusian atmosphere. This was the first interplanetary gravity assist ever used, a technique which would be used by later probes, most notably Voyager 1 and 2.

In 1975, the Soviet Venera 9 and 10 landers transmitted the first images from the surface of Venus, which were in black and white. In 1982 the first colour images of the surface were obtained with the Soviet Venera 13 and 14 landers.

NASA obtained additional data in 1978 with the Pioneer Venus project that consisted of two separate missions:^[196] Pioneer Venus Orbiter and Pioneer Venus Multiprobe.^[197] The successful Soviet Venera program came to a close in October 1983, when Venera 15 and 16 were placed in orbit to conduct detailed mapping of 25% of Venus’s terrain (from the north pole to 30°N latitude)^[198]

Several other missions explored Venus in the 1980s and 1990s, including Vega 1 (1985), Vega 2 (1985), Galileo (1990), Magellan (1994), Cassini–Huygens (1998), and MESSENGER (2006). All except Magellan were gravity assists. Then, Venus Express by the European Space Agency (ESA) entered orbit around Venus in April 2006. Equipped with seven scientific instruments, Venus Express provided unprecedented long-term observation of Venus’s atmosphere. ESA concluded the Venus Express mission in December 2014.^[199]

As of 2020, Japan’s Akatsuki is in a highly eccentric orbit around Venus since 7 December 2015, and there are several probing proposals under study by Roscosmos, NASA, ISRO, ESA, and the private sector (e.g. by Rocketlab).

In culture

Venus is a primary feature of the night sky, and so has been of remarkable importance in mythology, astrology and fiction throughout history and in different cultures.

In Sumerian religion, Inanna was associated with the planet Venus.^[202][203] Several hymns praise Inanna in her role as the goddess of the planet Venus.^{[164][203][202]} Theology professor Jeffrey Cooley has argued that, in many myths, Inanna’s movements may correspond with the movements of the planet Venus in the sky.^[164] The discontinuous movements of Venus relate to both mythology as well as Inanna’s dual nature.^[164] In Inanna’s Descent to the Underworld, unlike any other deity, Inanna is able to descend into the netherworld and return to the heavens. The planet Venus appears to make a similar descent, setting in the West and then rising again in the East.^[164] An introductory hymn describes Inanna leaving the heavens and heading for Kur, what could be presumed to be, the mountains, replicating the rising and setting of Inanna to the West.^[164] In Inanna and Shukaletuda and Inanna’s Descent into the Underworld appear to parallel the motion of the planet Venus.^[164] In Inanna and Shukaletuda, Shukaletuda is described as scanning the heavens in search of Inanna, possibly searching the eastern and western horizons.^[204] In the same myth, while searching for her attacker, Inanna herself makes several movements that correspond with the movements of Venus in the sky.^[164]

Classical poets such as Homer, Sappho, Ovid and Virgil spoke of the star and its light.^[205] Poets such as William Blake, Robert Frost, Letitia Elizabeth Landon, Alfred Lord Tennyson and William Wordsworth wrote odes to it.^[206]

In Chinese the planet is called Jīn-xīng (金星), the golden planet of the metal element. In India Shukra Graha («the planet Shukra») is named after the powerful saint Shukra. Shukra which is used in Indian Vedic astrology^[207] means «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.^[208] The word Shukra is also associated with semen, or generation. Venus is known as Kejora in Indonesian and Malaysian Malay. Modern Chinese, Japanese, Korean and Vietnamese cultures refer to the planet literally as the «metal star» (金星), based on the Five elements.^{[209][210][211][212]}

The Maya considered Venus to be the most important celestial body after the Sun and Moon. They called it Chac ek,^[213] or Noh Ek‘, «the Great Star».^[214] The cycles of Venus were important to their calendar and were described in some of their books such as Maya Codex of Mexico and Dresden Codex.

The Ancient Egyptians and Greeks believed Venus to be two separate bodies, a morning star and an evening star. The Egyptians knew the morning star as Tioumoutiri and the evening star as Ouaiti.^[215] The Greeks used the names Phōsphoros (Φωσϕόρος), meaning «light-bringer» (whence the element phosphorus; alternately Ēōsphoros (Ἠωσϕόρος), meaning «dawn-bringer»), for the morning star, and Hesperos (Ἕσπερος), meaning «Western one», for the evening star.^[216] Though by the Roman era they were recognized as one celestial object, known as «the star of Venus», the traditional two Greek names continued to be used, though usually translated to Latin as Lūcifer and Vesper.^[216][217]

Modern fiction

With the invention of the telescope, the idea that Venus was a physical world and possible destination began to take form.

The impenetrable Venusian cloud cover gave science fiction writers free rein to speculate on conditions at its surface; all the more so when early observations showed that not only was it similar in size to Earth, it possessed a substantial atmosphere. Closer to the Sun than Earth, the planet was frequently depicted as warmer, but still habitable by humans.^[218] The genre reached its peak between the 1930s and 1950s, at a time when science had revealed some aspects of Venus, but not yet the harsh reality of its surface conditions. Findings from the first missions to Venus showed the reality to be quite different and brought this particular genre to an end.^[219] As scientific knowledge of Venus advanced, science fiction authors tried to keep pace, particularly by conjecturing human attempts to terraform Venus.^[220]

Symbol

The astronomical symbol for Venus is the same as that used in biology for the female sex: a circle with a small cross beneath.^[221][222] The Venus symbol also represents femininity, and in Western alchemy stood for the metal copper.^[221][222] Polished copper has been used for mirrors from antiquity, and the symbol for Venus has sometimes been understood to stand for the mirror of the goddess although that is unlikely to be its true origin.^[221][222] In the Greek Papyrus Oxyrhynchus 235, the symbols for Venus and Mercury didn’t have the cross-bar on the bottom stroke.^[223]

Venus has also been identified as the star in a range of star and crescent depictions and symbols.

Habitability

Speculation on the possibility of life on Venus’s surface decreased significantly after the early 1960s when it became clear that the conditions are extreme compared to those on Earth. Venus’s extreme temperature and atmospheric pressure make water-based life as currently known unlikely.

Some scientists have speculated that thermoacidophilic extremophile microorganisms might exist in the cooler, acidic upper layers of the Venusian atmosphere).^{[224][225][226]} Such speculations go back to 1967, when Carl Sagan and Harold J. Morowitz suggested in a Nature article that tiny objects detected in Venus’s clouds might be organisms similar to Earth’s bacteria (which are of approximately the same size):

While the surface conditions of Venus make the hypothesis of life there implausible, the clouds of Venus are a different story altogether. As was pointed out some years ago, water, carbon dioxide and sunlight—the prerequisites for photosynthesis—are plentiful in the vicinity of the clouds.^[227]

In August 2019, astronomers led by Yeon Joo Lee reported that long-term pattern of absorbance and albedo changes in the atmosphere of the planet Venus caused by «unknown absorbers», which may be chemicals or even large colonies of microorganisms high up in the atmosphere of the planet, affect the climate.^[61] Their light absorbance is almost identical to that of micro-organisms in Earth’s clouds. Similar conclusions have been reached by other studies.^[228]

In September 2020, a team of astronomers led by Jane Greaves from Cardiff University announced the likely detection of phosphine, a gas not known to be produced by any known chemical processes on the Venusian surface or atmosphere, in the upper levels of the planet’s clouds.^{[229][230][231][232][233]} One proposed source for this phosphine is living organisms.^[234] The phosphine was detected at heights of at least 30 miles above the surface, and primarily at mid-latitudes with none detected at the poles. The discovery prompted NASA administrator Jim Bridenstine to publicly call for a new focus on the study of Venus, describing the phosphine find as «the most significant development yet in building the case for life off Earth».^[235][236]

Subsequent analysis of the data-processing used to identify phosphine in the atmosphere of Venus has raised concerns that the detection-line may be an artefact. The use of a 12th-order polynomial fit may have amplified noise and generated a false reading (see Runge’s phenomenon). Observations of the atmosphere of Venus at other parts of the electromagnetic spectrum in which a phosphine absorption line would be expected did not detect phosphine.^[237] By late October 2020, re-analysis of data with a proper subtraction of background did not show a statistically significant detection of phosphine.^{[238][239][240]}

Planetary protection

The Committee on Space Research is a scientific organization established by the International Council for Science. Among their responsibilities is the development of recommendations for avoiding interplanetary contamination. For this purpose, space missions are categorized into five groups. Due to the harsh surface environment of Venus, Venus has been under the planetary protection category two.^[241] This indicates that there is only a remote chance that spacecraft-borne contamination could compromise investigations.

Human presence

Venus is the place of the very first interplanetary human presence, mediated through robotic missions, with the first successful landings on another planet and extraterrestrial body other than the Moon. Venus was at the beginning of the space age frequently visited by space probes until the 1990s. Currently in orbit is Akatsuki, and the Parker Solar Probe routinely uses Venus for gravity assist maneuvers.^[242]

The only nation that has sent lander probes to the surface of Venus has been the Soviet Union,^[a] which has been used by Russian officials to call Venus a «Russian planet».^[243][244]

Habitation

While the surface conditions of Venus are very inhospitable, the atmospheric pressure and temperature 50 km above the surface are similar to those at Earth’s surface. With this in mind, Soviet engineer Sergey Zhitomirskiy (Сергей Житомирский, 1929–2004) in 1971^[245][246] and more contemporarily NASA aerospace engineer Geoffrey A. Landis in 2003^[247] suggested the use of aerostats for crewed exploration and possibly for permanent «floating cities» in the Venusian atmosphere, an alternative to the popular idea of living on planetary surfaces such as Mars.^[248][249] Among the many engineering challenges for any human presence in the atmosphere of Venus are the corrosive amounts of sulfuric acid in the atmosphere.^[247]

NASA’s High Altitude Venus Operational Concept is a mission concept that proposed a crewed aerostat design.

See also

• Geodynamics of Venus
• Outline of Venus
• Venus zone
• Stats of planets in the Solar System

Notes

References

External links

• Venus profile at NASA’s Solar System Exploration site
• Missions to Venus and Image catalog at the National Space Science Data Center
• Soviet Exploration of Venus and Image catalog at Mentallandscape.com
• Image catalog from the Venera missions
• Venus page at The Nine Planets
• Transits of Venus at NASA.gov
• Geody Venus, a search engine for surface features
• Interactive 3D gravity simulation of the pentagram that the orbit of Venus traces when Earth is held fixed at the centre of the coordinate system

Cartographic resources

• Map-a-Planet: Venus by the U.S. Geological Survey
• Gazetteer of Planetary Nomenclature: Venus by the International Astronomical Union
• Venus crater database by the Lunar and Planetary Institute
• Map of Venus by Eötvös Loránd University
• Google Venus 3D, interactive map of the planet

Венера является второй планетой от Солнца и относится к земной группе. Находясь от Земли на относительно небольшой дистанции, она отлично заметна невооруженным взглядом. Люди наблюдают за планетой еще с начала второго тысячелетия, и за это время успели отлично ее изучить. А с появлением возможности бороздить просторы космоса они смогли получить еще больше интересных сведений.

Общие сведения о планете

Венера расположена от Солнца на расстоянии примерно в 108 млн. км, из-за чего является одной из самых горячих планет в системе. Благодаря плотной атмосфере тяжело наблюдать ее поверхность, и для этого люди вынуждены посылать космические аппараты, которые высаживаются на нее.

Интересный факт: из-за того, что поверхность Венеры покрыта серными облаками, ее поверхность нельзя рассмотреть в телескоп. Для изучения рельефа, в XX веке люди использовали радиоволны, отправляя их в сторону планеты.

Еще в средние века люди поняли, что яркая звезда на небе является планетой, отражающей солнечные лучи. Это позволило отследить ее путь по небу. Своими размерами и структурой Венера похожа на Землю, но из-за разного расстояния до звезды обе обладают разными условиями.

Орбита и радиус

По сравнению с другими планетами Солнечной системы Венера не является большой. Ее радиус составляет примерно 6052 км, что не идет ни в какое сравнение с тем же параметром у газовых гигантов.

Планета обладает орбитой, представляющей собой практически идеальный круг. Во время вращения вокруг звезды расстояние до нее меняется в диапазоне от 107,5 до 108,9 млн км. Год на Венере длится 224,65 суток – именно за этот срок она делает полный оборот по орбите. Вокруг своей оси она вращается очень медленно: один день равен 247 земным. Таким образом, планета возвращается в ту же точку пространства относительно Солнца быстрее, чем делает полный оборот вокруг оси.

Физические характеристики планеты – размер, масса и другие

Венера стала одной из первых планет, которую начали изучать люди. Из-за этого сейчас у человечества имеются довольно точные значения многих параметров и характеристик планеты:

• масса равна 4,89 *10’24 кг;
• площадь поверхности составляет 460 млн кв.км;
• объем – 928 млрд куб.км;
• ускорение свободного падения 8,88 м/с2;
• плотность состава равна 5,2 г/с3;
• средняя температура на планете – 463 градуса Цельсия;
• давление на поверхности в 92 раза превышает земное;
• наклон оси составляет 177,36 градусов.

Большинство свойств Венеры сохраняется за счет больших скоплений металлов и горных пород. Они придают планете целостность и плотность структуры. Также существует теория, что ядро небесного тела представляет собой горячий металл, разогретый до жидкого состояния.

Возраст Венеры

Как и большинство объектов Солнечной системы, Венера начала формироваться примерно 4,6 млрд лет назад. Для определения возраста ученые использовали радиоуглеродное датирование. Такой методикой проверяется срок жизни большинства космических объектов, в том числе и планет. И практически всегда исследование выдает одну и ту же цифру. Это свидетельствует о том, что все объекты системы имеют примерно одинаковый возраст.

Когда появилось Солнце, вокруг него вращалось большое количество космической пыли. Частички постоянно сталкивались друг с другом, сбиваясь в единые объекты. Этот процесс продолжался до тех пор, пока не сформировались планеты, имеющие точную орбиту. Можно считать, что Венера когда-то появилась и материалов, находящихся в близости от Солнца.

Также ученые полагают, что несколько сотен миллионов лет назад поверхность планеты была не такой горячей, как сейчас, и на ней могли существовать водные океаны. Об этом говорят особенности ландшафта с большими оврагами. В некоторых местах Венеры до сих пор имеются активные вулканы. По оценкам, нынешний ее вид сформировался примерно 400 млн лет назад. Именно тогда поверхность превратилась в бескрайние каменные территории. Какой была планета в первые 4 млрд. лет своего существования – остается загадкой.

Атмосфера

Венера обладает самой плотной атмосферой среди планет Солнечной системы. На нижних слоях всегда имеется крупное скопление белых облаков. Из-за этого люди долгое время не могли узнать, как выглядит ее поверхность.

Большую часть атмосферы составляет двуокись углерода (96%). Остальной объем приходится на азот (3%) и серу (1%). Таким составом обуславливается высокая температура поверхности. Двуокись углерода вызывает сильный парниковый эффект, из-за чего температура на высоте до 2-3 км превышает 460 градусов Цельсия.

Интересный факт: лишь на высоте в 200 км температура в атмосфере Венеры приближается к земной и равна 46 градусам Цельсия.

Масса атмосферы в 93 раза превышает земную, из-за чего на поверхности давление также выше в 90 раз и составляет 92 бара. Нередко на Венере появляются мощные ветра, которые перемещаются в пространстве со скоростью 85 км/c. Они могут облететь всю планету за 5 дней, а иногда генерируют молнии.

Состав и поверхность Венеры

Поверхность гораздо плотнее, чем у Земли, и не имеет внутренних магнитных полей. На планете расположено много вулканов, 170 из которых считаются крупными и могут до сих пор функционировать.

Примерно миллиард лет назад почти вся поверхность Венеры была покрыта лавой, которая постоянно извергалась наружу, были регулярные землятресения. Но в один момент вулканы сильно снизили свою активность, и ученые до сих пор ищут причину этого события. Сейчас на поверхности планеты до сих пор могут происходить извержения, но в небольших количествах – на это указывает периодическое изменение количества диоксида серы.

Немалую часть поверхности составляют кратеры, размеры которых от нескольких километров могут доходить до нескольких сотен.

Строение Венеры

Ученым довольно трудно изучать строение планеты, поскольку из-за высоких температур космические аппараты быстро выходят из строя. Используя сейсмометры, они смогли получить некоторые данные о структуре Венеры.

Считается, что толщина поверхности составляет примерно 50 км, и основным веществом в ней является кремний. Далее начинается мантия, которая уходит вглубь примерно на 3000 км. До сих пор неизвестно, из чего она состоит, поскольку нет возможности сделать какой-либо анализ. В центре Венеры находится ядро из железа и никеля. Исследователи до сих пор гадают, является ли оно жидким или твердым.

Существенно в исследование строения планеты помогает тот факт, что она относится к земной группе, поскольку все ее представители обладают схожими свойствами.

Ядро Венеры

Ядро планеты расположено на глубине примерно в 3500 км. Ученым довольно трудно исследовать его, т.к. любой космический аппарат, приземлившийся на поверхность, быстро выходит из строя из-за высоких температур. И если на Земле люди спокойно используют сейсмометры, то с этим на второй планете от Солнца большие проблемы.

Поскольку Венера похожа по своей структуре на Землю, можно предположить, что внутри нее расположено такое же ядро. Однако до сих пор ученые не могут решить, находится оно в жидком или твердом состоянии. У планеты не прослеживается магнитное поле, а оно появляется при конвекции жидкого ядра. Однако оно все-таки может существовать у Венеры, просто из-за плотной поверхности оно не может вырваться наружу и стать заметным для измерительных приборов.

Также состояние ядра Венеры могло измениться с течением времени. Уже установлено, что миллионы лет назад что-то произошло на планете, из-за чего ее структура серьезно изменилась. Возможно, раньше ядро было жидким, но постепенно затвердело.

Погода и климат на Венере

Считается, что раньше на планете был климат, сильно отличающийся текущего. Из-за этого на Венере было много воды, а в атмосфере преобладал кислород. Однако из-за необъяснимых причин магнитосфера перестала работать, что обнулило защитный слой планеты. Солнечный ветер начал разъедать атмосферу, отправляя водород и воду в открытый космос.

Интересный факт: многие космические аппараты, отправляемые на Венеру, ломаются еще на этапе входа в атмосферу. Рекордсменом по работе на поверхности планеты является зонд, проработавший 127 минут.

Сейчас средняя температура поверхности составляет 460 градусов Цельсия. По ней регулярно гуляют ветра, разгоняющиеся до высоких скоростей. В прошлых веках астрономы полагали, что на Венере климат похож на земной. Они думали, что плотная облачная завеса появилась из-за водных испарений, поскольку на планете много воды. Но в 60-х, когда в небо устремились космические аппараты, стало известно, что облачная завеса имеет серную основу, более того, из нее регулярно идут кислотные дожди, которые испаряются, не долетая до поверхности.

Температура на Венере

Как уже говорилось выше, средняя температура на Венере равна 460 градусам Цельсия. Причем если на Земле этот параметр варьируется в большом диапазоне, то на второй планете от Солнца находится примерно на одном значении, вне зависимости от выбранной точки.

Из-за малого наклона оси, всего в 3 градуса, отсутствует смена сезонов. Серные испарения и высокая плотность атмосферы не дают теплу уходить в открытый космос, из-за чего оно распределяется по поверхности и сохраняет высокую температуру.

Ветра на Венере

Практически все ветра Венеры движутся с запада на восток. Они утягивают за собой плотный слой облаков, также заставляя их перемещаться в пространстве. Из-за этого наблюдать за следованием ветров не составляет труда.

Интересный факт: максимальная скорость ветра, зафиксированная на Венере, равна 700 км/ч. Такой ураган облетает планету меньше, чем за половину земных суток.

Средняя скорость ветров на планете составляет 350 км/ч. Причем чем выше они располагаются в атмосфере, тем быстрее двигаются. Если спуститься прямо на поверхность, то на ней воздушные потоки будут двигаться не быстрее 5-10 км/ч.

Вода на Венере

Поскольку температура на Венере составляет несколько сотен градусов, нетрудно догадаться, что в жидком состоянии вода на ее поверхности в принципе существовать не может. Исследования атмосферы планеты доказали, что в ней все-таки содержится водяной пар, но его доля составляет лишь 0,002% от общего количества веществ.

Такое открытие намекает на то, что миллиарды лет назад на Венере могла быть вода, а климат являлся более холодным. Но из-за регулярных столкновений с метеоритами и исчезновения магнитосферы климат стал в несколько раз горячее. Из-за этого все имеющиеся моря и океаны довольно быстро испарились. И если тепло задерживается на поверхности, то молекулы водяного пара вполне могли покинуть пределы атмосферы и отправиться в открытый космос. Стоит отметить, что если когда-нибудь на Земле тоже исчезнет магнитосфера, то климат планеты станет намного теплее, и практически вся поверхность превратится в пустыню.

Спутники

У Венеры нет спутников. Есть мнение, что на ранних этапах жизни планета обладала таковыми, но их могло поглотить Солнце, поскольку обладает большей силой притяжения. Еще одной причиной исчезновения небесных тел могли послужить регулярные атаки метеоритов.

Несмотря на то, что Венера сейчас не может похвастаться наличием близлежащих тел, она не одинока. У планеты есть один квазиспутник – это астероид VE68, открытый в 2002-ом году. Вот уже 7000 лет он сопровождает планету, следуя по похожей орбите, однако по подсчетам, через пять веков он сместится от нее на достаточное расстояние, чтобы потерять статус квазиспутника.

Земля и Венера

Обе планеты имеют много общего, из-за чего их часто называют сестрами. Венера лишь немного уступает Земле по размерам: ее диаметр составляет 95% от земного. Другие параметры также немногим ниже, чем у третьей планеты: ускорение свободного падения (90%), масса (81,5%), объем (85,7%), площадь поверхности (90%). Структура небесных тел также совпадает: в центре находится металлическое ядро, окутанное мантией и корой.

Но кроме сходства у Земли и Венеры немало отличий. У последней отсутствует конвекция ядра, магнитосфера не функционирует, из-за чего температура на поверхности гораздо выше. Атмосферное давление на второй планете в 93 раза больше, что также сказывается на климате. Не менее важным отличием является полное отсутствие воды, в то время как на Земле жидкости предостаточно.

Облака и парниковый эффект на Венере

Облака находятся на расстоянии от 48 до 65 км. Они представляют собой плотную оболочку из серной кислоты и углекислого газа, через которую практически не проходят солнечные лучи. Предполагается, что изначально их не было над планетой, но неизвестные обстоятельства привели к образованию.

Интересный факт: освещенность на Венере достигает лишь 3000 люкс. Для сравнения, в солнечный день на улице может быть 25000 люкс.

Углекислый газ и плотные облака не дают выходить теплу в атмосферу, из-за чего поверхность сильно нагревается, появляется парниковый эффект. Он способствует поддержанию температуры.

K какому типу планет принадлежит Венера?

Венера относится к земной группе, в которую входят планеты первой четверки. Также там присутствуют Меркурий, Земля и Марс. Плотность Венеры равна 5,204 г/м3, что является довольно высоким показателем и лишь на 0,3 г/м3 уступает земному.

Принадлежность Венеры к земной группе существенно упростило процесс ее исследования. Из-за агрессивной среды и высоких температур посадка космических спутников на поверхность практически невозможна. А поскольку планеты земной группы обладают схожими свойствами, исследователи в XX веке смогли выстроить многие гипотезы относительно состава, структуры и характеристик, основываясь на аналогичных данных, полученных во время изучения Земли и Марса. Спустя десятилетия они были подтверждены на практике, когда людьми начали изготавливаться аппараты, способные работать некоторое время на поверхности Венеры.

История открытия

Древние люди наблюдали за Венерой невооруженным взглядом. Поскольку в определенные периоды расстояние между планетой и Землей составляет лишь несколько десятков миллионов километров, она четко виднеется на небе в виде белого пятна. Однако в то время не существовало технологий, позволяющих детально разглядеть загадочный объект. И люди наблюдали на небе утром и вечером лишь белое пятно, которое принималось за две разные звезды.

В 1581 году до н.э. вавилонские астрономы пришли к выводу, что данные звезды являются одним объектом, более того, это планета. Тогда и было составлено ее первое описание.

Интересный факт: несмотря на открытие вавилонских астрономов, до VI века до н.э. существовало мнение, что Венера не является планетой.

В 1032 году ученый Авиценн доказал, что Венера находится к солнцу ближе, чем Земля. Для этого он проследил ее путь по орбите в пределах видимости. Спустя примерно 600 лет Галилей установил фазы планеты и описал их. В 1761 году вклад в понимание устройства Венеры внес Михаил Ломоносов, обнаруживший на ней атмосферу. В 20-х годах прошлого века люди впервые исследовали небесное тело с помощью ультрафиолетовых лучей. К 60-ым годам у астрономов уже было четкое представление о свойствах планеты, которые расширились благодаря высадке космических аппаратов на ее поверхность.

Кто открыл Венеру?

Нельзя точно сказать, кому принадлежит открытие планеты. Еще астрономы древности наблюдали за планетой, но считали ее яркой звездой из-за сильного отражения солнечных лучей. Когда Коперник составил модель системы, стало понятно, что данное “светило” перемещается в небе как планета, значит, таковой и является.

В 1610 году Галилей, используя изобретенный им телескоп. рассмотрел Венеру и первым сделал заключение, что ее поверхность скрыта от глаза густыми облаками.

Исследования Венеры

С развитием космических технологий во второй половине XX века люди начали активно изучать планеты Солнечной системы. В 60-е годы СССР направил на Венеру несколько космических аппаратов, которые должны были изучить ее особенности. Однако ни один из спутников не смог достигнуть своей цели.

В то же время американцы отправили космический аппарат Маринер-2. Он подошел к поверхности планеты на расстояние 34,8 тыс. км. С этой дистанции спутник сумел измерить примерную температуру поверхности. Тогда ученые впервые установили, что Венера является самой горячей планетой в Солнечной системе. Это подтвердило факт отсутствия жизни.

В 1966 году аппарат Венера-3 сумел высадиться на поверхности, но сразу же пришел в негодность. Следующий прототип, прибывший на планету через год, сломался во время посадки, но успел передать точные данные о температуре и давлении. Через три года Венера-7 разбилась при посадке, но на протяжении 23-х минут передавала информацию с поверхности.

С тех пор человечество оставило попытки высадиться на планету. Сейчас космические аппараты отправляются к Венере лишь с целью наблюдения на безопасном расстоянии. Например, устройство Магеллан с 89-го по 93-й годы находилось на орбите и изучило внешний вид планеты на 98%.

Сейчас ученые до сих пор разрабатывают масштабные программы по отправке зондов ко второй планете от Солнца, и они помогают получать все больше сведений.

Почему Венера так называется?

Еще в древности Вавилоняне отождествляли планету с любовью и романтическими чувствами. Из-за этого они называли ее Иштар, в честь богини женственности. Позже ее имя римские астрономы заменили на Венеру, поскольку именно так они называли свою богиню любви. С тех пор именно такое название закрепилось за второй планетой от Солнца. Древние греки называли ее Афродитой, в честь своей богини любви.

Древние Египтяне также наблюдали за планетой, но принимали ее за две разные звезды, появляющиеся дважды в день. Из-за этого они называли их Утренней и Вечерней.

Интересное видео о Венере

Согласно официальной позиции Международного астрономического союза (МАС), организации присваивающей имена астрономическим объектам, планет всего 8.

Текущее положение среди планет Солнечной системы

Плутон был исключен из разряда планет в 2006 году. т.к. в поясе Койпера находятся объекты которые больше/либо равны по размерам с Плутоном. Поэтому, даже если его принимать его за полноценное небесное тело, то тогда необходимо к этой категории присоединить Эриду, у которой с Плутоном почти одинаковый размер.

Планеты Солнечной системы по порядку

По определению MAC, есть 8 известных планет: Меркурий, Венера, Земля, Марс, Юпитер, Сатурн, Уран и Нептун.

Все планеты делят на две категории в зависимости от их физических характеристик: земной группы и газовые гиганты.

Планеты земного типа

Меркурий

Самая маленькая планета Солнечной системы имеет радиус всего 2440 км. Период обращения вокруг Солнца, для простоты понимания приравненный к земному году, составляет 88 дней, при этом оборот вокруг собственной оси Меркурий успевает совершить всего полтора раза. Таким образом, его сутки длятся приблизительно 59 земных дней. Долгое время считалось, что эта планета все время повёрнута к Солнцу одной и той же стороной, поскольку периоды его видимости с Земли повторялись с периодичностью, примерно равной четырем Меркурианским суткам.  Это заблуждение было развеяно с появлением возможности применять радиолокационные исследования и вести постоянные наблюдения с помощью космических станций. Орбита Меркурия – одна из самых нестабильных, меняется не только скорость перемещения и его удалённость от Солнца, но и само положение. Любой интересующийся может наблюдать этот эффект.

Близость к Солнцу стала причиной того, что Меркурий подвержен самым большим перепадам температуры среди планет нашей системы. Средняя дневная температура составляет около 350 градусов по Цельсию, а ночная -170 °C. В атмосфере выявлены натрий, кислород, гелий, калий, водород и аргон. Существует теория, что он был ранее спутником Венеры, но пока это остается недоказанным. Собственные спутники у него отсутствуют.

Венера

Вторая от Солнца планета, атмосфера которой почти полностью состоит из углекислого газа. Её часто называют Утренней звездой и Вечерней звездой, потому что она первой из звёзд становится видна после заката, так же как и перед рассветом продолжает быть видимой и тогда, когда все остальные звёзды скрылись из поля зрения. Процент диоксида углерода составляет в атмосфере 96%, азота в ней сравнительно немного – почти 4% и в совсем незначительном количестве присутствует водяной пар и кислород.

Подобная атмосфера создает эффект парника, температура на поверхности из-за этого даже выше, чем у Меркурия и достигает 475 °C. Считается самой неторопливой, венерианские сутки длятся 243 земных дня, что почти равно году на Венере – 225 земных дней. Многие называют её сестрой Земли из-за массы и радиуса, значения которых очень близки к земным показателям. Радиус Венеры составляет 6052 км (0,85% земного). Спутников, как и у Меркурия, нет.

Земля

Третья планета от Солнца и единственная в нашей системе, где на поверхности есть жидкая вода, без которой не смогла бы развиться жизнь на планете. По крайней мере, жизнь в том виде, в котором мы её знаем. Радиус Земли равен 6371 км и, в отличие от остальных небесных тел нашей системы, более 70% её поверхности покрыто водой. Остальное пространство занимают материки. Ещё одной особенностью Земли являются тектонические плиты, скрытые под мантией планеты. При этом они способны перемещаться, хоть и с очень малой скоростью, что со временем вызывает изменение ландшафта. Скорость перемещения планеты по ней – 29-30 км/сек.

Один оборот вокруг своей оси занимает почти 24 часа, причем полное прохождение по орбите длится 365 суток, что намного больше в сравнении с ближайшими планетами-соседями. Земные сутки и год также приняты как эталон, но сделано это лишь для удобства восприятия временных отрезков на остальных планетах. У Земли имеется один естественный спутник – Луна.

Марс

Четвёртая планета от Солнца, известная своей разрежённой атмосферой. Начиная с 1960 года, Марс активно исследуется учеными нескольких стран, включая СССР и США. Не все программы исследования были успешными, но найденная на некоторых участках вода позволяет предположить, что примитивная жизнь на Марсе существует, или существовала в прошлом.

Яркость этой планеты позволяет видеть его с Земли без всяких приборов. Причем раз в 15-17 лет, во время Противостояния, он становится самым ярким объектом на небе, затмевая собой даже Юпитер и Венеру.

Радиус почти вдвое меньше земного и составляет 3390 км, зато год значительно дольше – 687 суток. Спутников у него 2 — Фобос и Деймос.

Наглядная модель Солнечной системы

Внимание! Анимация работает только в браузерах поддерживающих стандарт -webkit (Google Chrome, Opera или Safari).

Планеты — гиганты

Существуют четыре газовых гиганта, располагающихся за орбитой Марса: Юпитер, Сатурн, Уран, Нептун. Они находятся во внешней Солнечной системе. Отличаются своей массивностью и газовым составом.

Юпитер

Пятая по счёту от Солнца и крупнейшая планета нашей системы. Радиус её – 69912 км, она в 19 раз больше Земли и всего в 10 раз меньше Солнца. Год на Юпитере не самый долгий в солнечной системе, длится 4333 земных суток (неполных 12 лет). Его же собственные сутки имеют продолжительность около 10 земных часов. Точный состав поверхности планеты пока определить не удалось, однако известно, что криптон, аргон и ксенон имеются на Юпитере в гораздо больших количествах, чем на Солнце.

Существует мнение, что один из четырёх газовых гигантов на самом деле – несостоявшаяся звезда. В пользу этой теории говорит и самое большое количество спутников, которых у Юпитера много – целых 67. Чтобы представить себе их поведение на орбите планеты, нужна достаточно точная и чёткая модель солнечной системы. Самые крупные из них – Каллисто, Ганимед, Ио и Европа. При этом Ганимед является крупнейшим спутником планет во всей солнечной системе, радиус его составляет 2634 км, что на 8% превышает размер Меркурия, самой маленькой планеты нашей системы. Ио отличается тем, что является одним из трёх имеющих атмосферу спутников.

Сатурн

Вторая по размерам планета и шестая по счёту в Солнечной системе. В сравнении с остальными планетами, наиболее схожа с Солнцем составом химических элементов. Радиус поверхности равен 57350 км, год составляет 10 759 суток (почти 30 земных лет). Сутки здесь длятся немногим дольше, чем на Юпитере – 10,5 земных часов. Количеством спутников он ненамного отстал от своего соседа – 62 против 67. Самым крупным спутником Сатурна является Титан, так же, как и Ио, отличающийся наличием атмосферы. Немного меньше него по размеру, но от этого не менее известные – Энцелад, Рея, Диона, Тефия, Япет и Мимас. Именно эти спутники являются объектами для наиболее частого наблюдения, и потому можно сказать, что они наиболее изучены в сравнении с остальными.

Долгое время кольца на Сатурне считались уникальным явлением, присущим только ему. Лишь недавно было установлено, что кольца имеются у всех газовых гигантов, но у остальных они не настолько явно видны. Их происхождение до сих пор не установлено, хотя существует несколько гипотез о том, как они появились. Кроме того, совсем недавно было обнаружено, что неким подобием колец обладает и Рея, один из спутников шестой планеты.

Уран

Седьмая по счету и третья по размеру планета, радиус которой составляет 25267 км. Справедливо считается самой холодной планетой среди остальных, температура достигает -224 градусов по Цельсию. Продолжительность года — 30 685 суток в земном исчислении (почти 84 года), сутки же ненамного меньше земных – 17 с небольшим часов. Из-за сильной наклонности оси планеты, иногда создается впечатление, будто она не вращается, как остальные небесные тела нашей системы, а катится, подобно шару. Это может наблюдать любой, кого интересует астрономия, геометрическая модель солнечной системы наглядно продемонстрирует этот эффект.

Спутников у него гораздо меньше, чем у соседнего Сатурна, всего 27. Наиболее известны Титания, Ариэль, Оберон, Умбриэль и Миранда. Они не настолько крупны, как спутники.

Примечательно, что ведя наблюдения за Ураном в свой телескоп, астроном Уильям Гершель сначала не понял, что он наблюдает за планетой, будучи уверен, что он видит комету.

Нептун

Размером восьмая планета солнечной системы очень близка к своему ближайшему соседу, Урану. Радиус Нептуна равняется 24547 км. Год на планете равняется 60 190 суток (приблизительно 164 земных года). В атмосфере зафиксированы самые сильные ветра в нашей системе, скорость которых достигает 260 м/с.

По сравнению с остальными планетами-гигантами спутников у него совсем мало – всего 14. Самые известные из них – Тритон, третий в солнечной системе спутник, имеющий атмосферу, Протей и Нереида.

Примечательно, что это – единственная из планет, которая была открыта не благодаря наблюдениям, а с помощью математических расчётов.

Планеты Солнечной системы
Карликовые планеты	Плутон· Церера· Хаумеа· Макемаке· Эрида
Планеты Земной группы	Меркурий· Венера· Земля· Марс
Газовые гиганты	Юпитер· Сатурн· Уран· Нептун

Венера – вторая планета от Солнца. Она – одно из наиболее изученных небесных объектов. Но поскольку нога человека ещё не ступала на Венеру, у учёных есть ещё много вопросов к планете. Что носит имя римской богини.

Общие сведения о планете

Возраст Венеры

По оценкам учёных, планета Венера сформировалась примерно в то же время, что и Земля – 4,6 млрд лет назад из газопылевого облака.

Спутники

Во все время учёные предполагали наличие у Венеры спутников. Некоторые даже утверждали, что наблюдали их. Но сегодня можно с уверенностью сказать, что полноценных спутников как земная Луна у планеты нет.

Астрономические характеристики

Венера в точности похожа на Землю по своим характеристикам. Часто её называют «сестрой» нашей планеты, поскольку небесные тела имеют схожие размер и массу. Радиус Венеры также идентичен земному. Есть предположения, что раньше климат небесного тела был мягким, похожим на земной. Так как несколько миллиардов лет назад светимость Солнца была на 30% ниже. А сама планета находилась в более холодной области, чем сейчас. Это говорит о том, что характеристика Венеры ещё больше похожа на заселённую «сестру».

Размер, Масса, орбита

Физические характеристика планеты Венера

Если сравнить Венеру с Землёй, можно увидеть, что характеристики планет довольно схожи. Масса Венеры составляет 4,87⋅10 24 кг, это 81,5% от земной. Диаметр Венеры – 12 103,6 км (тут разрыв с Землей всего 638,4 км). Период вращения Венеры вокруг звезды – 243 земных суток. Вращение Венеры происходит быстрее, чем вращение Земли. Орбита расположена ближе к Солнцу, чем земная.

Средний диаметр	12 103,6 км
Площадь поверхности	4,60⋅10*8 км² 0,902 земных
Масса	4,8675⋅10*24 кг 0,815 земных
Объём	9,38⋅10*11 км³ 0,857 земных
Средняя плотность	5,24 г/см³
Ускорение свободного падения на экваторе	8,87 м/с² 0,904 g
Первая космическая скорость	7,328 км/с
Вторая космическая скорость	10,363 км/с
Экваториальная скорость вращения	6,52 км/ч
Период вращения	243,023 дней
Наклон оси	177,36°
Прямое восхождение	18 ч 11 мин 2 с
северного полюса	272,76°
Склонение северного полюса	67,16°
Альбедо	0,67 (геометрическое), 0,77 (Бонда)
Видимая звёздная величина	−4,6
Угловой диаметр	9,7″–66,0″

Поверхность Венеры

Поверхность Венеры долгое время была недоступной для прямого наблюдения. Причина – густые серные облака, которые покрывают планету.

Но в XX веке с помощью методов радиолокации получилось составить картину поверхности. Она представляла собой каменистую пустошь, 90% которой – это базальт. Проще говоря – застывшая лава.

Из-за облаков серы можно подумать, что цвет планеты – жёлто-белый, хотя на деле он коричневый. Венера это планета, которую неопытный обыватель и вовсе может принять за газовую.

Некоторые впадины на поверхности дают учёным основания предполагать, что раньше на планете были океаны. Но пока других весомых доказательств этой теории нет.

Удивительно и то, что на поверхности очень мало ударных кратеров. Но у исследователей есть этому объяснение. По той причине, что атмосфера планеты очень плотная. Мелкие космические тела при падении попросту не достигают поверхности, разрываясь в облаках серы.

День и ночь

Год на Венере длится 243 для. Такой период вращения Венеры вокруг Солнца. Венера в нашем представлении имеет интересный цикл смены дня и ночи. Одни сутки тут длятся 116 дней и 18 часов, а длительность дневного и ночного времени –58 дней и 9 часов. Всё это связано с тем, как вращается Венера вокруг Солнца.

Состав и поверхность

Строение Венеры

По своему строению объект схож со своей «сестрой» Землёй. В её недрах выделяют три уровня: кора, мантия и ядро.

• Кора представляет собой 20-километровое твёрдое соединение силикатных пород.
• Мантия – жидкая и горячая, её состав в данный момент не установлен. Есть большая вероятность, что он схож с земным, и в нём преобладают кислород, магний и кремний.
• Ядро состоит их железа и никеля.

Погода и климат на Венере

Венера – самый горячий объект в Солнечной системе. И это несмотря на то, что она находится лишь на втором месте по дальности от Солнца. Ближе всего к звезде расположен Меркурий, но даже на его поверхности градусы не понимаются так высоко.

Такое состояние планеты связано с постоянным парниковым эффектом. Из-за которого атмосфера и поверхность Венеры разогреваются до 462 °C. Также на это повлияла и скорость вращения.

Атмосфера и температура

Давление на поверхности Венеры – 93 бар. Эти цифры колоссальны: такое давление способно сплющить земной автомобиль по толщины фольги. Интересен и тот факт, что вес 80-киллограмового человека на Венере уменьшится до 72,5.

Атмосфера на 96,5% из углекислого газ, 3,5% азота. Остальная часть – сера, аргон, водяной пар. Именно углекислый газ создаёт парниковый эффект, при котором небесное тело разогревается до 462 °C

Атмосферу принято делить на: мезосферу, стратосферу и тропосферу. Также имеется мезопауза – зона, в которой происходит резкий перепад температура. Звучит удивительно, но здесь температура некоторых участков может быть даже отрицательной.

Ученые заметили, что ежегодно планета теряет водород и кислород, атомы которых улетучиваются в космос. Это даёт предполагать, что на планете возможно существование воды в жидком виде, по крайней мере, в верхних слоях атмосферы.

Температура на поверхности	737 К (464 °C)
Атмосферное давление	9,3 МПа (93 бар)
углекислый газ (CO2)	~96,5 %
азот (N2)	~3,5 %
диоксид серы (SO2)	0,018 %
аргон (Ar)	0,007 %
водяной пар (H2O)	0,003 %
угарный газ (CO)	0,0017 %
гелий (He)	0,0012 %
неон (Ne)	0,0007 %

Облака Венеры

Облака – непроглядная газовая оболочка, которая находится на высоте 60-70 км. Учёными был довольно точно определён состав этих облаков: двуокись серы и примеси серной кислоты.

Считается, что в прошлом на здесь происходили крупные вулканические процессы. Благодаря чему атмосфера обогатилась серой.

Есть свидетельства, что периодически Венеру поливают кислотные дожди. При этом идут они только в верхних слоях атмосферы, так как капли не успевают коснуться поверхности и испаряются.

Интересные факты

Открытие планеты

О Венере людям было известно издревле, поскольку её можно было наблюдать невооружённым глазом после заката и перед восходом. Люди обращали внимание на то, как вращается Венера вокруг Солнца. Именно поэтому «утренняя» и «вечерняя» звезда имела значимое место в культуре и мифологии различных стран. Как и многие планеты, что названы в честь бога, объект назван в честь римской богини.

Несмотря на то, что многие учёные древности пытались изучить небесную механику планеты. Первооткрывателем планеты принято считать Галилео Галилея, который в XVII смог наблюдать планету в телескоп. Именно с этого времени началось научное изучение планеты.

Исследование Венеры

В 1761 году Михаил Ломоносов наблюдал атмосферу планеты, сделав вывод о наличии на небесном теле плотных облаков, закрывающих поверхность планеты от взора. До XX века Венера в понимании исследователей была сложным объектом для изучения. Так как поверхность была скрыта под облаками.

В 1961 году СССР запустил первую миссию «Венера-1», но она не была успешной.

Год спустя американский «Mariner-2» смог установить температуру планеты, а также подтвердить отсутствие у планеты магнитного поля.

В 1971 и 1972 годах советские корабли достигли поверхности планеты, однако они не выдержали нагрузок плотной атмосферы и вышли из строя, так и не взяв пробы грунта.

Были еще попытки. И в 1975 году ещё два советских аппарата совершили мягкую посадку и сделали несколько чёрно-белых фотографий с поверхности. В 1981 году была получена первая звукозапись с планеты.

Сегодня научный интерес к изучению Венеры не угасает: многие страны запускают спутники к «сестре» Земли и планирует космические миссии. Интересует, в первую очередь, возможность возникновения и поддержания жизни.

Терраформирование Венеры

«Сестра» Земли – первый кандидат на терраформирование в будущем. Расстояние от земли до Венеры меньше, чем до Марса. Она имеет комфортное расстояние от Солнца. Имеет схожие астрономические характеристики и находится в обитаемой зоне. Солнечные лучи не смогут разогреть планету настолько, чтобы на ней не могла присутствовать жизнь, при условии, что получится преобразить планету под стать земным условиям.

К теоретическим способам терраформирования Венеры относятся:

• Создание солнечных экранов, которые дадут возможность снизить температуру на поверхности;
• Бомбардировка небесного тела с помощью комет и астероидов;
• Доставка на планету микроорганизмов, способных своей деятельностью изменить состав атмосферы.

К менее реальным с технической точки зрения способам относится изменение орбиты, что увеличит удалённость от звезды.

Проблемами для терраформирования являются: высокая плотность и, как следствие, высокая температура планеты. На Венеру придётся доставлять воду, так как там её практически нет. У планеты нет магнитосферы, чтобы защищать поверхность от солнечной радиации. Также, планета совершает довольно медленный оборот вокруг своей оси.

Космические экспедиции

К сожалению, человек, при нынешних условиях, не сможет высадиться на плоскости Венеры. Это такая планета Солнечной системы, которая уж точно не будет дружелюбна к человеку.

Остаётся возлагать надежду на космические аппараты. Так в 2029 году Роскосмос планирует изучить планету с помощью специальной станции, которая проработает около месяца. Также в ближайшее десятилетие планируется запуск «Венера-Глоб», чтобы изучить атмосферу и рельеф Венеры.

Венера-1	12 февраля 1961	Первый пролёт мимо Венеры. Из-за потери связи научная программа не выполнена
Маринер-2	27 августа 1962	Пролёт. Сбор научной информации
Зонд-1	2 апреля 1964	Пролёт. Сбор научной информации
Венера-2	12 ноября 1965	Пролёт. Сбор научной информации
Венера-3	16 ноября 1965	Достижение Венеры. Сбор научной информации
Венера-4	12 июня 1967	Атмосферные исследования и попытка достижения поверхности (аппарат раздавлен давлением, о котором до этих пор ничего не было известно)
Маринер-5	14 июня 1967	Пролёт с целью исследований атмосферы
Венера-5	5 января 1969	Спуск в атмосфере, определение её химического состава
Венера-6	10 января 1969	Спуск в атмосфере, определение её химического состава
Венера-7	17 августа 1970	Первая мягкая посадка на поверхность планеты. Сбор научной информации
Венера-8	27 марта 1972	Мягкая посадка. Пробы грунта.
Венера-9	8 июня 1975	Мягкая посадка модуля и искусственный спутник Венеры. Первые чёрно-белые фотографии поверхности.
Венера-10	14 июня 1975	Мягкая посадка модуля и искусственный спутник Венеры. Чёрно-белые фотографии поверхности.
Пионер-Венера-1	20 мая 1978	Искусственный спутник, радиолокация поверхности
Пионер-Венера-2	8 августа 1978	Вхождение в атмосферу, научные исследования
Венера-11	9 сентября 1978	Мягкая посадка модуля, пролёт аппарата
Венера-12	14 сентября 1978	Мягкая посадка модуля, пролёт аппарата
Венера-13	30 октября 1981	Мягкая посадка модуля. Первая запись звука на поверхности и первая передача цветного панорамного изображения
Венера-14	4 ноября 1981	Мягкая посадка модуля. Передача цветного панорамного изображения
Венера-15	2 июня 1983	Искусственный спутник Венеры, радиолокация
Венера-16	7 июня 1983	Искусственный спутник Венеры, радиолокация
Магеллан	4 мая 1989	Искусственный спутник Венеры, подробная радиолокация
Венера-экспресс	9 ноября 2005	Искусственный спутник Венеры, радиолокация южного полюса
Акацуки	21 мая 2010	Исследование атмосферы. Попытка выхода на орбиту Венеры в 2010 году закончилась неудачей. После повторной попытки 7 декабря 2015 года аппарат смог удачно выйти на заданную орбиту

Так же может заинтересовать

Солнечная система

Меркурий

Земля

Марс

Юпитер

Сатурн

Уран

Нептун

Черная дыра