Venus

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Venus The Venusian symbol, a circle with a small equal-armed cross beneath it
Venus in approximately true colour, a nearly uniform pale cream, although the image has been processed to bring out details.[1] The planet's disc is about three-quarters illuminated. Almost no variation or detail can be seen in the clouds.
Venus processed from two filters. The surface is obscured by a thick blanket of clouds.
Designations
PronunciationListeni/ˈvnəs/
AdjectiveVenusian or (rarely) Cytherean, Venerean
Orbital characteristics[2][4]
Epoch J2000
Aphelion
  • 108,939,000 km
  • 0.728 213 AU
Perihelion
  • 107,477,000 km
  • 0.718 440 AU
Semi-major axis
  • 108,208,000 km
  • 0.723 327 AU
Eccentricity0.0067
Orbital period
Synodic period583.92 days[2]
Average orbital speed35.02 km/s
Mean anomaly50.115°
Inclination
Longitude of ascending node76.678°
Argument of perihelion55.186°
SatellitesNone
Physical characteristics
Mean radius
  • 6,051.8 ± 1.0 km[5]
  • 0.949 9 Earths
Flattening0[5]
Surface area
  • 4.60×108 km2
  • 0.902 Earths
Volume
  • 9.28×1011 km3
  • 0.866 Earths
Mass
  • 4.8676×1024 kg
  • 0.815 Earths
Mean density5.243 g/cm3
Equatorial surface gravity
Escape velocity10.36 km/s
Sidereal rotation period−243.018 5 day (Retrograde)
Equatorial rotation velocity6.52 km/h (1.81 m/s)
Axial tilt177.36°[2]
North pole right ascension
  • 18 h 11 min 2 s
  • 272.76°[6]
North pole declination67.16°
Albedo
Surface temp.minmeanmax
Kelvin737 K[2]
Celsius462 °C
Apparent magnitude
  • brightest −4.9[8][9] (crescent)
  • −3.8[10] (full)
Angular diameter9.7"–66.0"[2]
Atmosphere
Surface pressure92 bar (9.2 MPa)
Composition
 
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Venus The Venusian symbol, a circle with a small equal-armed cross beneath it
Venus in approximately true colour, a nearly uniform pale cream, although the image has been processed to bring out details.[1] The planet's disc is about three-quarters illuminated. Almost no variation or detail can be seen in the clouds.
Venus processed from two filters. The surface is obscured by a thick blanket of clouds.
Designations
PronunciationListeni/ˈvnəs/
AdjectiveVenusian or (rarely) Cytherean, Venerean
Orbital characteristics[2][4]
Epoch J2000
Aphelion
  • 108,939,000 km
  • 0.728 213 AU
Perihelion
  • 107,477,000 km
  • 0.718 440 AU
Semi-major axis
  • 108,208,000 km
  • 0.723 327 AU
Eccentricity0.0067
Orbital period
Synodic period583.92 days[2]
Average orbital speed35.02 km/s
Mean anomaly50.115°
Inclination
Longitude of ascending node76.678°
Argument of perihelion55.186°
SatellitesNone
Physical characteristics
Mean radius
  • 6,051.8 ± 1.0 km[5]
  • 0.949 9 Earths
Flattening0[5]
Surface area
  • 4.60×108 km2
  • 0.902 Earths
Volume
  • 9.28×1011 km3
  • 0.866 Earths
Mass
  • 4.8676×1024 kg
  • 0.815 Earths
Mean density5.243 g/cm3
Equatorial surface gravity
Escape velocity10.36 km/s
Sidereal rotation period−243.018 5 day (Retrograde)
Equatorial rotation velocity6.52 km/h (1.81 m/s)
Axial tilt177.36°[2]
North pole right ascension
  • 18 h 11 min 2 s
  • 272.76°[6]
North pole declination67.16°
Albedo
Surface temp.minmeanmax
Kelvin737 K[2]
Celsius462 °C
Apparent magnitude
  • brightest −4.9[8][9] (crescent)
  • −3.8[10] (full)
Angular diameter9.7"–66.0"[2]
Atmosphere
Surface pressure92 bar (9.2 MPa)
Composition

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.[11] It has no natural satellite. It is named after the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows.[12] Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it has been referred to by ancient cultures as the Morning Star or Evening Star.

Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, gravity, and bulk composition (Venus is both the closest planet to Earth and the planet closest in size to Earth). However, it has also been shown to be very different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth's. With a mean surface temperature of 735 K (462 °C; 863 °F), Venus is by far the hottest planet in the Solar System. It has no carbon cycle to lock carbon back into rocks and surface features, nor does it seem to have any organic life to absorb it in biomass. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. Venus may have possessed oceans in the past,[13][14] but these would have vaporized as the temperature rose due to a runaway greenhouse effect.[15] The water has most probably photodissociated, and, because of the lack of a planetary magnetic field, the free hydrogen has been swept into interplanetary space by the solar wind.[16] Venus's surface is a dry desertscape interspersed with slab-like rocks and periodically refreshed by volcanism.

Physical characteristics

Venus is one of the four terrestrial planets in the Solar System, meaning that, like the Earth, it is a rocky body. In size and mass, it is similar to the Earth, and is often described as Earth's "sister" or "twin".[17] The diameter of Venus is 12,092 km (only 650 km less than the Earth's) and its mass is 81.5% of the Earth's. Conditions on the Venusian surface differ radically from those on Earth, owing to its dense carbon dioxide atmosphere. The mass of the atmosphere of Venus is 96.5% carbon dioxide, with most of the remaining 3.5% being nitrogen.[18]

Geography

The Venusian surface was a subject of speculation until some of its secrets were revealed by planetary science in the 20th century. It was finally mapped in detail by Project Magellan in 1990–91. The ground shows evidence of extensive volcanism, and the sulfur in the atmosphere may indicate there have been some recent eruptions.[19][20]

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.[21] 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 above the Venusian average surface elevation. The southern continent is called Aphrodite Terra, after the Greek goddess of love, and is the larger of the two highland regions at roughly the size of South America. A network of fractures and faults covers much of this area.[22]

The absence of evidence of lava flow accompanying any of the visible caldera remains an enigma. The planet has few impact craters, demonstrating the surface is relatively young, approximately 300–600 million years old.[23][24] In addition to the impact craters, mountains, and valleys commonly found on rocky planets, Venus has some unique surface features. Among these are flat-topped volcanic features called "farra", which look somewhat like pancakes and range in size from 20 to 50 km across, and from 100 to 1,000 m high; radial, star-like fracture systems called "novae"; features with both radial and concentric fractures resembling spider webs, known as "arachnoids"; and "coronae", circular rings of fractures sometimes surrounded by a depression. These features are volcanic in origin.[25]

Most Venusian surface features are named after historical and mythological women.[26] Exceptions are Maxwell Montes, named after James Clerk Maxwell, and highland regions Alpha Regio, Beta Regio and Ovda Regio. The former three features were named before the current system was adopted by the International Astronomical Union, the body that oversees planetary nomenclature.[27]

The longitudes of physical features on Venus are expressed relative to its prime meridian. The original prime meridian passed through the radar-bright spot at the center of the oval feature Eve, located south of Alpha Regio.[28] After the Venera missions were completed, the prime meridian was redefined to pass through the central peak in the crater Ariadne.[29][30]

Size comparison of Mercury, Venus, Earth and the Moon, Mars, and Ceres on the far right. This may not be exactly to scale, because the visual disc of Venus with its atmosphere makes it look bigger than its solid-body diameter.


Surface geology

Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it possesses 167 large volcanoes that are over 100 km across. The only volcanic complex of this size on Earth is the Big Island of Hawaii.[25] This is not because Venus is more volcanically active than Earth, but because its crust is older. Earth's oceanic crust is continually recycled by subduction at the boundaries of tectonic plates, and has an average age of about 100 million years,[31] while the Venusian surface is estimated to be 300–600 million years old.[23][25]

Several lines of evidence point to ongoing volcanic activity on Venus. During the Soviet Venera program, the Venera 11 and Venera 12 probes detected a constant stream of lightning, and Venera 12 recorded a powerful clap of thunder soon after it landed. The European Space Agency's Venus Express recorded abundant lightning in the high atmosphere.[32] While rainfall drives thunderstorms on Earth, there is no rainfall on the surface of Venus (though sulfuric acid rain falls in the upper atmosphere, then evaporates around 25 km above the surface). One possibility is that ash from a volcanic eruption was generating the lightning. Another piece of evidence comes from measurements of sulfur dioxide concentrations in the atmosphere, which dropped by a factor of 10 between 1978 and 1986. This may imply the levels had earlier been boosted by a large volcanic eruption.[33] Almost a thousand impact craters on Venus are evenly distributed across its surface. On other cratered bodies, such as the Earth and the Moon, craters show a range of states of degradation. On the Moon, degradation is caused by subsequent impacts, while on Earth, it is caused by wind and rain erosion. On Venus, about 85% of the craters are in pristine condition. The number of craters, together with their well-preserved condition, indicates the planet underwent a global resurfacing event about 300–600 million years ago,[23][24] followed by a decay in volcanism.[34] 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.[25]

Venusian craters range from 3 km to 280 km 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 down so much by the atmosphere that they do not create an impact crater.[35] Incoming projectiles less than 50 metres in diameter will fragment and burn up in the atmosphere before reaching the ground.[36]

Cloud structure in the Venusian atmosphere in 1979, revealed by ultraviolet observations by Pioneer Venus Orbiter
Cloud structure in the Venusian atmosphere in 1979, revealed by ultraviolet observations by Pioneer Venus Orbiter
A false colour image of Venus: ribbons of lighter colour stretch haphazardly across the surface. Plainer areas of more even colouration lie between.
Global radar view of the surface from Magellan radar imaging between 1990 and 1994
Impact craters on the surface of Venus (image reconstructed from radar data)
Impact craters on the surface of Venus (image reconstructed from radar data)

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.[37] 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 at least partially liquid because the two planets have been cooling at about the same rate.[38] The slightly smaller size of Venus suggests pressures are significantly lower in its deep interior than Earth. 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.[39] Instead, Venus may lose its internal heat in periodic major resurfacing events.[23]

Atmosphere and climate

Venus has an extremely dense atmosphere, which consists mainly of carbon dioxide and a small amount of nitrogen. The atmospheric mass is 93 times that of Earth's atmosphere, while the pressure at the planet's surface is about 92 times that at Earth's surface—a pressure equivalent to that at a depth of nearly 1 kilometre under Earth's oceans. The density at the surface is 65 kg/m³, 6.5% that of water. The CO2-rich atmosphere, along with thick clouds of sulfur dioxide, generates the strongest greenhouse effect in the Solar System, creating surface temperatures of at least 462 °C (864 °F).[11][40] This makes the Venusian surface hotter than Mercury's, which has a minimum surface temperature of −220 °C (−364.0 °F) and maximum surface temperature of 420 °C (788 °F),[41] even though Venus is nearly twice Mercury's distance from the Sun and thus receives only 25% of Mercury's solar irradiance. The surface of Venus is often described as hellish.[42] This temperature is higher than temperatures used to achieve sterilization.

Studies have suggested that billions of years ago, the Venusian atmosphere was much more like Earth's than it is now, and that there may have been substantial quantities of liquid water on the surface, but, after a period of 600 million to several billion years,[43] a runaway greenhouse effect was caused by the evaporation of that original water, which generated a critical level of greenhouse gases in its atmosphere.[44] Although the surface conditions on the planet are no longer hospitable to any Earthlike life that may have formed prior to this event, the possibility that a habitable niche still exists in the lower and middle cloud layers of Venus cannot yet be excluded.[45][46][47]

Thermal inertia and the transfer of heat by winds in the lower atmosphere mean that the temperature of the Venusian surface does not vary significantly between the night and day sides, despite the planet'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 Venusian 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 if the heat, pressure and lack of oxygen were not a problem.[48]

Above the dense CO2 layer are thick clouds consisting mainly of sulfur dioxide and sulfuric acid droplets.[49][50] These clouds reflect and scatter about 90% of the sunlight that falls on them back into space, and prevent visual observation of the Venusian surface. The permanent cloud cover means that although Venus is closer than Earth to the Sun, the Venusian surface is not as well lit. Strong 300 km/h (190 mph) winds at the cloud tops circle the planet about every four to five earth days.[51] Venusian winds move at up to 60 times the speed of the planet's rotation, while Earth's fastest winds are only 10–20% rotation speed.[52]

The surface of Venus is effectively isothermal; it retains a constant temperature not only between day and night but between the equator and the poles.[2][53] The planet's minute axial tilt—less than 3°, compared to 23° on Earth—also minimizes seasonal temperature variation.[54] The only appreciable variation in temperature occurs with altitude. In 1995, the Magellan probe imaged a highly reflective substance at the tops of the highest mountain peaks that bore a strong resemblance to terrestrial snow. This substance arguably formed from a similar process to snow, albeit at a far higher temperature. Too volatile to condense on the surface, it rose in gas form to cooler higher elevations, where it then fell as precipitation. The identity of this substance is not known with certainty, but speculation has ranged from elemental tellurium to lead sulfide (galena).[55]

The clouds of Venus are capable of producing lightning much like the clouds on Earth.[56] The existence of lightning had been controversial since the first suspected bursts were detected by the Soviet Venera probes. In 2006–07 Venus Express clearly detected whistler mode waves, the signatures of lightning. Their intermittent appearance indicates a pattern associated with weather activity. The lightning rate is at least half of that on Earth.[56] In 2007 the Venus Express probe discovered that a huge double atmospheric vortex exists at the south pole of the planet.[57][58]

Another discovery made by the Venus Express probe in 2011 is that an ozone layer exists high in the atmosphere of Venus.[59]

On January 29, 2013, ESA scientists reported that the ionosphere of the planet Venus streams outwards in a manner similar to "the ion tail seen streaming from a comet under similar conditions."[60][61]

Atmospheric composition

Synthetic stick absorption spectrum of a simple gas mixture corresponding to the Earth's atmosphere
Synthetic stick absorption spectrum of a simple gas mixture corresponding to the Earth's atmosphere
Venusian atmosphere composition based on HITRAN data[62] created using Hitran on the Web system.[63]
Venusian atmosphere composition based on HITRAN data[62] created using Hitran on the Web system.[63]
Green colour – water vapour, red – carbon dioxide, WN – wavenumber (other colours have different meanings, lower wavelengths on the right, higher on the left).

















Magnetic field and core

In 1967, Venera 4 found the Venusian 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,[64][65] rather than by an internal dynamo in the core like the one inside the Earth. Venus's small induced magnetosphere provides negligible protection to the atmosphere against cosmic radiation. This radiation may result in cloud-to-cloud lightning discharges.[66]

The lack of an intrinsic magnetic field at Venus was surprising given it is similar to Earth in size, and was expected also to contain a dynamo at its core. A dynamo requires three things: a conducting liquid, rotation, and convection. The core is thought to be electrically conductive and, while its rotation is often thought to be too slow, simulations show it is adequate to produce a dynamo.[67][68] This implies the dynamo is missing because of a lack of convection in the Venusian core. On Earth, convection occurs in the liquid outer layer of the core because the bottom of the liquid layer is much hotter than the top. On Venus, a global resurfacing event may have shut down plate tectonics and led to a reduced heat flux through the crust. This caused the mantle temperature to increase, thereby reducing the heat flux out of the core. As a result, no internal geodynamo is available to drive a magnetic field. Instead, the heat energy from the core is being used to reheat the crust.[69]

One possibility is Venus has no solid inner core,[70] or its core is not currently cooling, so the entire liquid part of the core is at approximately the same temperature. Another possibility is its core has already completely solidified. The state of the core is highly dependent on the concentration of sulfur, which is unknown at present.[69]

The weak magnetosphere around Venus means the solar wind is interacting directly with the outer atmosphere of the planet. Here, ions of hydrogen and oxygen are being created by the dissociation of neutral molecules from ultraviolet radiation. The solar wind then supplies energy that gives some of these ions sufficient velocity to escape the planet's gravity field. This erosion process results in a steady loss of low-mass hydrogen, helium, and oxygen ions, while higher-mass molecules, such as carbon dioxide, are more likely to be retained. Atmospheric erosion by the solar wind probably led to the loss of most of the planet's water during the first billion years after it formed. The erosion has increased the ratio of higher-mass deuterium to lower-mass hydrogen in the upper atmosphere by 150 times compared to the ratio in the lower atmosphere.[71]

Orbit and rotation

Venus orbits the Sun at an average distance of about 108 million kilometres (about 0.7 AU) and completes an orbit every 224.65 days. Venus is the second planet from the Sun and it revolves round the Sun approximately 1.6 times (yellow trail) in Earth's 365 days (blue trail)

Venus orbits the Sun at an average distance of about 0.72 AU (108,000,000 km; 67,000,000 mi), and completes an orbit every 224.65 days. Although all planetary orbits are elliptical, Venus's orbit is the closest to circular, with an eccentricity of less than 0.01.[2] When Venus lies between the Earth and the Sun, a position known as inferior conjunction, it makes the closest approach to Earth of any planet at an average distance of 41 million km.[2] The planet reaches inferior conjunction every 584 days, on average.[2] Owing to 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; then there are none for about 60,158 years.[72] During periods of greater eccentricity, Venus can come as close as 38.2 million km.[2]

All the planets of the Solar System orbit the Sun in an anti-clockwise direction as viewed from above the Sun's north pole. Most planets also rotate on their axis in an anti-clockwise direction, but Venus rotates clockwise (called "retrograde" rotation) once every 243 Earth days—the slowest rotation period of any planet. A Venusian sidereal day thus lasts longer than a Venusian year (243 versus 224.7 Earth days). The equator of the Venusian surface rotates at 6.5 km/h (4.0 mph), while on Earth rotation speed at the equator is about 1,670 km/h (1,040 mph).[73] Venus's rotation has slowed down by 6.5 min per Venusian sidereal day since the Magellan spacecraft visited it 16 years ago.[74] 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); one Venusian year is about 1.92 Venusian (solar) days long.[75] To an observer on the surface of Venus, the Sun would rise in the west and set in the east.[75]

Venus may have formed from the solar nebula with a different rotation period and obliquity, reaching to 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.[76][77] The 584-day average interval between successive close approaches to the Earth is almost exactly equal to 5 Venusian solar days,[78] but the hypothesis of a spin–orbit resonance with Earth has been discounted.[79]

Venus has no natural satellites,[80] though the asteroid 2002 VE68 presently maintains a quasi-orbital relationship with it.[81][82] Besides this quasi-satellite, it has two other temporary co-orbitals, 2001 CK32 and 2012 XE133.[83] 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.[84] 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 and merged with Venus.[85] If later impacts created moons, these were absorbed 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.[80]

Observation

A photograph of the night sky taken from the seashore. A glimmer of sunlight is on the horizon. There are many stars visible. Venus is at the center, much brighter than any of the stars, and its light can be seen reflected in the ocean.
Venus is always brighter than the brightest stars outside our solar system, as can be seen here over the Pacific Ocean
Phases of Venus and evolution of its apparent diameter

Venus is always brighter than any star (apart from the Sun). The greatest luminosity, apparent magnitude −4.9,[9] occurs during crescent phase when it is near the Earth. Venus fades to about magnitude −3 when it is backlit by the Sun.[8] The planet is bright enough to be seen in a mid-day clear sky,[86] and the planet can be easy to see when the Sun is low on the horizon. As an inferior planet, it always lies within about 47° of the Sun.[10]

Venus "overtakes" the Earth every 584 days as it orbits the Sun.[2] As it does so, it changes from the "Evening Star", visible after sunset, to the "Morning Star", visible before sunrise. While 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". U.S. President Jimmy Carter reported having seen a UFO in 1969, which later analysis suggested was probably the planet. Countless other people have mistaken Venus for something more exotic.[87]

As it moves around its orbit, Venus displays phases like those of the Moon in a telescopic view. The planet presents a small "full" image when it is on the opposite side of the Sun. It shows a larger "quarter phase" when it is at its maximum elongations from the Sun, and is at its brightest in the night sky, and presents a much larger "thin crescent" in telescopic views as it comes around to the near side between the Earth and the Sun. Venus is at its largest and presents its "new phase" when it is between the Earth and the Sun. Its atmosphere can be seen in a telescope by the halo of light refracted around the planet.[10]

Transits of Venus

The Venusian orbit is slightly inclined relative to the Earth's orbit; thus, when the planet passes between the 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 the 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 English astronomer Jeremiah Horrocks.[88]

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.[89]

The preceding pair of transits occurred in December 1874 and December 1882; the following pair will occur in December 2117 and December 2125.[90] 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.[91] 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.[92][93]

Ashen light

A long-standing mystery of Venus observations is the so-called ashen light—an apparent weak illumination of the dark side of the planet, 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 may be illusory, resulting from the physiological effect of observing a bright, crescent-shaped object.[94]

Studies

Early studies

The "black drop effect" as recorded during the 1769 transit

Venus was known to ancient civilizations both as the "morning star" and as the "evening star", names that reflect the early understanding that these were two separate objects. The Venus tablet of Ammisaduqa, dated 1581 BCE, shows the Babylonians understood the two were a single object, referred to in the tablet as the "bright queen of the sky", and could support this view with detailed observations.[95] The Greeks thought of the two as separate stars, Phosphorus and Hesperus, until the time of Pythagoras in the sixth century BC.[96] The Romans designated the morning aspect of Venus as Lucifer, literally "Light-Bringer", and the evening aspect as Vesper, both literal translations of the respective Greek names.

The transit of Venus was first observed in 1032 by the Persian astronomer Avicenna, who concluded Venus is closer to the Earth than the Sun,[97] and established Venus was, at least sometimes, below the Sun.[98] In the 12th century, the Andalusian astronomer Ibn Bajjah observed "two planets as black spots on the face of the Sun", which were later identified as the transits of Venus and Mercury by the Maragha astronomer Qotb al-Din Shirazi in the 13th century.[99] The transit of Venus was also observed by Jeremiah Horrocks on 4 December 1639 (24 November under the Julian calendar in use at that time), along with his friend, William Crabtree, at each of their respective homes.[100]

Galileo's discovery that Venus showed phases (while remaining near the Sun in our sky) proved that it orbits the Sun and not the Earth

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 centered on the Earth.[101]

The atmosphere of Venus was discovered in 1761 by Russian polymath Mikhail Lomonosov.[102][103] 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.[104] 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.[105]

Ground-based research

Modern telescopic view of Venus from Earth's surface

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 UV observations were carried out in the 1920s, when Frank E. Ross found that UV photographs revealed considerable detail that was absent in visible and infrared radiation. He suggested this was due to a very dense, yellow lower atmosphere with high cirrus clouds above it.[106]

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.[107] 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.[108]

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 (980 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.[109] These three features are now the only ones on Venus that do not have female names.[110]

Exploration

Early efforts

Mariner 2, launched in 1962

The first robotic space probe mission to Venus, and the first to any planet, began on 12 February 1961, with the launch of the Venera 1 probe. The first craft of the otherwise highly successful Soviet Venera program, Venera 1 was launched on a direct impact trajectory, but contact was lost seven days into the mission, when the probe was about 2 million km from Earth. It was estimated to have passed within 100,000 km of Venus in mid-May.[111]

The United States exploration of Venus also started badly with the loss of the Mariner 1 probe on launch. The subsequent Mariner 2 mission, after a 109-day transfer orbit on 14 December 1962, became the world's first successful interplanetary mission, passing 34,833 km above the surface of Venus. Its microwave and infrared radiometers revealed that while the Venusian cloud tops were cool, the surface was extremely hot—at least 425 °C, confirming previous Earth-based measurements[112] and finally ending any hopes that the planet might harbour ground-based life. Mariner 2 also obtained improved estimates of its mass and of the astronomical unit, but was unable to detect either a magnetic field or radiation belts.[113]

Atmospheric entry

Pioneer Venus Multiprobe

The Soviet Venera 3 probe crash-landed on Venus on 1 March 1966. It was the first man-made object to enter the atmosphere and strike the surface of another planet. Its communication system failed before it was able to return any planetary data.[114] On 18 October 1967, Venera 4 successfully entered the atmosphere and deployed science experiments. Venera 4 showed the surface temperature was even hotter than Mariner 2 had measured, at almost 500 °C, and the atmosphere was 90 to 95% carbon dioxide. The Venusian atmosphere was considerably denser than Venera 4's designers had anticipated, and its slower than intended parachute descent meant its batteries ran down before the probe reached the surface. After returning descent data for 93 minutes, Venera 4's last pressure reading was 18 bar at an altitude of 24.96 km.[114]

One day later on 19 October 1967, Mariner 5 conducted a fly-by at a distance of less than 4000 km above the cloud tops. Mariner 5 was originally built as backup for the Mars-bound Mariner 4; when that mission was successful, the probe was refitted for a Venus mission. A suite of instruments more sensitive than those on Mariner 2, in particular its radio occultation experiment, returned data on the composition, pressure and density of the Venusian atmosphere.[115] The joint Venera 4 – Mariner 5 data was analysed by a combined Soviet-American science team in a series of colloquia over the following year,[116] in an early example of space cooperation.[117]

Armed with the lessons and data learned from Venera 4, the Soviet Union launched the twin probes Venera 5 and Venera 6 five days apart in January 1969; they encountered Venus a day apart on 16 and 17 May. The probes were strengthened to improve their crush depth to 25 bar and were equipped with smaller parachutes to achieve a faster descent. Since then-current atmospheric models of Venus suggested a surface pressure of between 75 and 100 bar, neither was expected to survive to the surface. After returning atmospheric data for a little over 50 minutes, they were both crushed at altitudes of approximately 20 km before going on to strike the surface on the night side of Venus.[114]

Surface and atmospheric science

A stubby barrel-shaped spacecraft in orbit above Venus. A small dish antenna is at the centre of one of its end faces
The Pioneer Venus orbiter
Pioneer Venus topography data displayed in Winkel Tripel projection

Venera 7 represented an effort to return data from the planet's surface, and was constructed with a reinforced descent module capable of withstanding a pressure of 180 bar. The module was precooled before entry and equipped with a specially reefed parachute for a rapid 35-minute descent. While entering the atmosphere on 15 December 1970, the parachute is believed to have partially torn, and the probe struck the surface with a hard, yet not fatal, impact. Probably tilted onto its side, it returned a weak signal, supplying temperature data for 23 minutes, the first telemetry received from the surface of another planet.[114]

The Venera program continued with Venera 8 sending data from the surface for 50 minutes, after entering the atmosphere on 22 July 1972. Venera 9, which entered the atmosphere of Venus on 22 October 1975, and Venera 10, which entered the atmosphere three days later, sent the first images of the Venusian landscape. The two landing sites presented very different terrains in the immediate vicinities of the landers: Venera 9 had landed on a 20-degree slope scattered with boulders around 30–40 cm across; Venera 10 showed basalt-like rock slabs interspersed with weathered material.[118]

In the meantime, the United States had sent the Mariner 10 probe on a gravitational slingshot trajectory past Venus on its way to Mercury. On 5 February 1974, Mariner 10 passed within 5790 km of Venus, returning over 4000 photographs as it did so. The images, the best then achieved, showed the planet to be almost featureless in visible light, but ultraviolet light revealed details in the clouds that had never been seen in Earth-bound observations.[119]

Venera 15/16 topography data displayed in Winkel Tripel projection

The American Pioneer Venus project consisted of two separate missions.[120] The Pioneer Venus Orbiter was inserted into an elliptical orbit around Venus on 4 December 1978, and remained there for over 13 years, studying the atmosphere and mapping the surface with radar. The Pioneer Venus Multiprobe released a total of four probes, which entered the atmosphere on 9 December 1978, returning data on its composition, winds and heat fluxes.[121]

Venera 13 landing site
Position of Venera landing sites returning images form the surface

Four more Venera lander missions took place over the next four years, with Venera 11 and Venera 12 detecting Venusian electrical storms;[122] and Venera 13 and Venera 14, landing on 1 and 5 March 1982, returning the first colour photographs of the surface. All four missions deployed parachutes for braking in the upper atmosphere, then released them at altitudes of 50 km, the dense lower atmosphere providing enough friction to allow for unaided soft landings. Both Venera 13 and 14 analysed soil samples with an on-board X-ray fluorescence spectrometer, and attempted to measure the compressibility of the soil with an impact probe.[122] Venera 14 struck its own ejected camera lens cap and its probe failed to contact the soil.[122] The Venera program came to a close in October 1983, when Venera 15 and Venera 16 were placed in orbit to conduct mapping of the Venusian terrain with synthetic aperture radar.[123]

In 1985, the Soviet Union took advantage of the opportunity to combine missions to Venus and Comet Halley, which passed through the inner Solar System that year. En route to Halley, on 11 and 15 June 1985, the two spacecraft of the Vega program each dropped a Venera-style probe (of which Vega 1's partially failed) and released a balloon-supported aerobot into the upper atmosphere. The balloons achieved an equilibrium altitude of around 53 km, where pressure and temperature are comparable to those at Earth's surface. They remained operational for around 46 hours, and discovered the Venusian atmosphere was more turbulent than previously believed, and subject to high winds and powerful convection cells.[124][125]

Radar mapping

Magellan radar topographical map of Venus (false colour)

Early Earth-based radar provided a basic idea of the surface. The Pioneer Venus and the Veneras provided improved resolution.

The United States' Magellan probe was launched on 4 May 1989, with a mission to map the surface of Venus with radar.[27] The high-resolution images it obtained during its 4½ years of operation far surpassed all prior maps and were comparable to visible-light photographs of other planets. Magellan imaged over 98% of the Venusian surface by radar,[126] and mapped 95% of its gravity field. In 1994, at the end of its mission, Magellan was sent to its destruction into the atmosphere of Venus to quantify its density.[127] Venus was observed by the Galileo and Cassini spacecraft during fly-bys on their respective missions to the outer planets, but Magellan was the last dedicated mission to Venus for over a decade.[128][129]

Current and future missions

NASA's MESSENGER mission to Mercury performed two fly-bys of Venus in October 2006 and June 2007, to slow its trajectory for an eventual orbital insertion of Mercury in March 2011. MESSENGER collected scientific data on both those fly-bys.[130]

The Venus Express probe was designed and built by the European Space Agency. Launched on 9 November 2005 by a Russian Soyuz-Fregat rocket procured through Starsem, it successfully assumed a polar orbit around Venus on 11 April 2006.[131] The probe is undertaking a detailed study of the Venusian atmosphere and clouds, including mapping of the planet's plasma environment and surface characteristics, particularly temperatures. One of the first results from Venus Express is the discovery that a huge double atmospheric vortex exists at the south pole of the planet.[131]

Artist's impression of a Stirling cooled Venus Rover devised by NASA.[132]

The Japan Aerospace Exploration Agency (JAXA) devised a Venus orbiter, Akatsuki (formerly "Planet-C"), which was launched on 20 May 2010, but the craft failed to enter orbit in December 2010. Hopes remain that the probe can successfully hibernate and make another insertion attempt in six years. Planned investigations included surface imaging with an infrared camera and experiments designed to confirm the presence of lightning, as well as the determination of the existence of current surface volcanism.[133]

The European Space Agency (ESA) hopes to launch a mission to Mercury in 2014, called BepiColombo, which will perform two fly-bys of Venus before it reaches Mercury orbit in 2020.[134]

Under its New Frontiers Program, NASA has proposed a lander mission called the Venus In-Situ Explorer to land on Venus to study surface conditions and investigate the elemental and mineralogical features of the regolith. The probe would be equipped with a core sampler to drill into the surface and study pristine rock samples not weathered by the harsh surface conditions. A Venus atmospheric and surface probe mission, "Surface and Atmosphere Geochemical Explorer" (SAGE), was selected by NASA as a candidate mission study in the 2009 New Frontiers selection,[135] but the mission was not selected for flight.

The Venera-D (Russian: Венера-Д) probe is a proposed Russian space probe to Venus, to be launched around 2016, to make remote-sensing observations around the planet and deploying a lander, based on the Venera design, capable of surviving for a long duration on the surface. Other proposed Venus exploration concepts include rovers, balloons, and aeroplanes.[136]

Manned fly-by concept

A manned Venus fly-by mission, using Apollo program hardware, was proposed in the late 1960s.[137] The mission was planned to launch in late October or early November 1973, and would have used a Saturn V to send three men to fly past Venus in a flight lasting approximately one year. The spacecraft would have passed approximately 5,000 km (3,100 mi) from the surface of Venus about four months later.[137]

Spacecraft timeline

This is a list of attempted and successful spacecraft that have left Earth to explore Venus more closely.[138] Venus has also been imaged by the Hubble Space Telescope in Earth orbit, and distant telescopic observations are another source of information about Venus.

Timeline by NASA Goddard Space Flight Center (up to 2011)[138]
ResponsibleMissionLaunchElements and resultNotes
USSR Soviet UnionSputnik 74 February 1961Impact (attempted)
USSR Soviet UnionVenera 112 February 1961Fly-by (contact lost)
USA United StatesMariner 122 July 1962Fly-by (launch failure)
USSR Soviet UnionSputnik 1925 August 1962Fly-by (attempted)
USA United StatesMariner 227 August 1962Fly-by
USSR Soviet UnionSputnik 201 September 1962Fly-by (attempted)
USSR Soviet UnionSputnik 2112 September 1962Fly-by (attempted)
USSR Soviet UnionCosmos 2111 November 1963Attempted Venera test flight?
USSR Soviet UnionVenera 1964A19 February 1964Fly-by (launch failure)
USSR Soviet UnionVenera 1964B1 March 1964Fly-by (launch failure)
USSR Soviet UnionCosmos 2727 March 1964Fly-by (attempted)
USSR Soviet UnionZond 12 April 1964Fly-by (contact lost)
USSR Soviet UnionVenera 212 November 1965Fly-by (contact lost)
USSR Soviet UnionVenera 316 November 1965Lander (contact lost)
USSR Soviet UnionCosmos 9623 November 1965Lander (attempted?)
USSR Soviet UnionVenera 1965A23 November 1965Fly-by (launch failure)
USSR Soviet UnionVenera 412 June 1967Probe
USA United StatesMariner 514 June 1967Fly-by
USSR Soviet UnionCosmos 16717 June 1967Probe (attempted)
USSR Soviet UnionVenera 55 January 1969Probe
USSR Soviet UnionVenera 610 January 1969Probe
USSR Soviet UnionVenera 717 August 1970Lander
USSR Soviet UnionCosmos 35922 August 1970Probe (attempted)
USSR Soviet UnionVenera 827 March 1972Probe
USSR Soviet UnionCosmos 48231 March 1972Probe (attempted)
USA United StatesMariner 104 November 1973Fly-byMercury fly-by
USSR Soviet UnionVenera 98 June 1975Orbiter and lander
USSR Soviet UnionVenera 1014 June 1975Orbiter and lander
USA United StatesPioneer Venus 120 May 1978Orbiter
USA United StatesPioneer Venus 28 August 1978Probes
USSR Soviet UnionVenera 119 September 1978Fly-by bus and lander
USSR Soviet UnionVenera 1214 September 1978Fly-by bus and lander
USSR Soviet UnionVenera 1330 October 1981Fly-by bus and lander
USSR Soviet UnionVenera 144 November 1981Fly-by bus and lander
USSR Soviet UnionVenera 152 June 1983Orbiter
USSR Soviet UnionVenera 167 June 1983Orbiter
USSR Soviet UnionVega 115 December 1984Lander and balloonComet Halley fly-by
USSR Soviet UnionVega 221 December 1984Lander and balloonComet Halley fly-by
USA United StatesMagellan4 May 1989Orbiter
USA United StatesGalileo18 October 1989Fly-byJupiter orbiter/probe
USA United StatesCassini15 October 1997Fly-bySaturn orbiter
USA United StatesMESSENGER3 August 2004Flyby (x2)Mercury orbiter
ESA EuropeVenus Express9 November 2005Orbiter
JPN JapanAkatsuki7 December 2010Orbiter (attempted)Possible reattempt in 2016
ESA Europe
JPN Japan
BepiColomboJuly 2014Fly-by (x2, planned)Planned Mercury orbiter

In culture

Clementine star tracker image of the Moon obscuring the Sun, with Venus on top

The adjective Venusian is commonly used for items related to Venus, though the Latin adjective is the rarely used Venerean; the archaic Cytherean is still occasionally encountered. Venus is the only planet in the Solar System that is named after a female figure.[a] (Three dwarf planets – Ceres, Eris and Haumea – along with many of the first discovered asteroids[139] and some moons (such as the Galilean moons) also have feminine names. Earth and its moon also have feminine names in many languages—Gaia/Terra, Selene/Luna—but the female mythological figures who personified them were named after them, not the other way around.)[140]

Venus 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.[141] The Venus symbol also represents femininity, and in Western alchemy stood for the metal copper.[141] 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.[141]

Anthropology and Venus

The Pre-Columbian Mayan Dresden Codex, which calculates Venus appearances

As one of the brightest objects in the sky, Venus has been known since prehistoric times and as such has gained an entrenched position in human culture. It is described in Babylonian cuneiformic texts such as the Venus tablet of Ammisaduqa, which relates observations that possibly date from 1600 BCE.[142] The Babylonians named the planet Ishtar (Sumerian Inanna), the personification of womanhood, and goddess of love.[143] She had a dual role as a goddess of war, thereby representing a deity that presided over birth and death.[144]

The Ancient Egyptians believed Venus to be two separate bodies and knew the morning star as Tioumoutiri and the evening star as Ouaiti.[145] Likewise, believing Venus to be two bodies, the Ancient Greeks called the morning star Φωσφόρος, Phosphoros (Latinized Phosphorus), the "Bringer of Light" or Ἐωσφόρος, Eosphoros (Latinized Eosphorus), the "Bringer of Dawn". The evening star they called Hesperos (Latinized Hesperus) (Ἓσπερος, the "star of the evening"). By Hellenistic times, the ancient Greeks realized the two were the same planet,[146][147] which they named after their goddess of love, Aphrodite (Αφροδίτη) (Phoenician Astarte),[148] a planetary name that is retained in modern Greek.[149] Hesperos would be translated into Latin as Vesper and Phosphoros as Lucifer ("Light Bearer"), a poetic term later used to refer to the fallen angel cast out of heaven.[b] The Romans, who derived much of their religious pantheon from the Greek tradition, named the planet Venus after their goddess of love.[150] Pliny the Elder (Natural History, ii,37) identified the planet Venus with Isis.[151]

Shukra is the Sanskrit name for Venus

In Iranian mythology, especially in Persian mythology, the planet usually corresponds to the goddess Anahita. In some parts of Pahlavi literature the deities Aredvi Sura and Anahita are regarded as separate entities, the first one as a personification of the mythical river and the latter as a goddess of fertility, which is associated with the planet Venus. As the goddess Aredvi Sura Anahita—and simply called Anahita as well—both deities are unified in other descriptions, e. g. in the Greater Bundahishn, and are represented by the planet. In the Avestan text Mehr Yasht (Yasht 10) there is a possible early link to Mithra. The Persian name of the planet today is "Nahid", which derives from Anahita and later in history from the Pahlavi language Anahid.[152][153][154][155] The planet Venus was important to the Maya civilization, who developed a religious calendar based in part upon its motions, and held the motions of Venus to determine the propitious time for events such as war. They named it Noh Ek', the Great Star, and Xux Ek', the Wasp Star. The Maya were aware of the planet's synodic period, and could compute it to within a hundredth part of a day.[156]

The Maasai people named the planet Kileken, and have an oral tradition about it called The Orphan Boy.[157]

Venus is important in many Australian aboriginal cultures, such as that of the Yolngu people in Northern Australia. The Yolngu gather after sunset to await the rising of Venus, which they call Barnumbirr. As she approaches, in the early hours before dawn, she draws behind her a rope of light attached to the Earth, and along this rope, with the aid of a richly decorated "Morning Star Pole", the people are able to communicate with their dead loved ones, showing that they still love and remember them. Barnumbirr is also an important creator-spirit in the Dreaming, and "sang" much of the country into life.[158]

Venus plays a prominent role in Pawnee mythology. The Pawnee, a North American native tribe, until as late as 1838, practised a morning star ritual in which a girl was sacrificed to the morning star.[159]

In western astrology, derived from its historical connotation with goddesses of femininity and love, Venus is held to influence desire and sexual fertility.[160] In Indian Vedic astrology, Venus is known as Shukra,[161] meaning "clear, pure" or "brightness, clearness" in Sanskrit. One of the nine Navagraha, it is held to affect wealth, pleasure and reproduction; it was the son of Bhrgu, preceptor of the Daityas, and guru of the Asuras.[162] Modern Chinese, Japanese and Korean cultures refer to the planet literally as the "metal star" (金星), based on the Five elements.[163]

In the metaphysical system of Theosophy, it is believed that on the etheric plane of Venus there is a civilization that existed hundreds of millions of years before Earth's[164] and it is also believed that the governing deity of Earth, Sanat Kumara, is from Venus.[165]

In literature

Artist's conception of a terraformed Venus

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.[166] 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.[167] As scientific knowledge of Venus advanced, so science fiction authors tried to keep pace, particularly by conjecturing human attempts to terraform Venus.[168]

Perhaps the strangest appearance of Venus in popular culture is as the harbinger of destruction in Immanuel Velikovsky's Worlds in Collision (1950). In this intensely controversial book, Velikovsky argued that many seemingly unbelievable stories in the Old Testament are true recollections of times when Venus, which Velikovsky claimed had somehow been ejected from Jupiter as a comet, nearly collided with the Earth. He contended that Venus caused most of the strange events of the Exodus story. He cites legends in many other cultures (such as Greek, Mexican, Chinese and Indian) indicating that the effects of the near-collision were global. The scientific community rejected his wildly unorthodox book, but it became a bestseller.[169]

Colonization

Owing to its extremely hostile conditions, a surface colony on Venus is out of the question with current technology. The atmospheric pressure and temperature approximately fifty kilometres above the surface are similar to those at the Earth's surface and Earth air (nitrogen and oxygen) would be a lifting gas in the Venusian atmosphere of mostly carbon dioxide. This has led to proposals for "floating cities" in the Venusian atmosphere.[170] Aerostats (lighter-than-air balloons) could be used for initial exploration and ultimately for permanent settlements.[170] Among the many engineering challenges are the dangerous amounts of sulfuric acid at these heights.[170]

Views

Venus in 630 nm light
Ultraviolet view of Venus by the Hubble telescope, in false colour
X-ray image of Venus by Chandra (AXAF)

See also

Notes

  1. ^ Goddesses such as Gaia and Terra were named after the Earth, and not vice versa.
  2. ^ Jerome translated Septuagint heosphoros and Hebrew helel as lucifer, in Isaiah 14:12.

References

  1. ^ Lakdawalla, Emily (21 September 2009), Venus Looks More Boring than You Think It Does, Planetary Society Blog (retrieved 4 December 2011)
  2. ^ a b c d e f g h i j k Williams, David R. (15 April 2005). "Venus Fact Sheet". NASA. Retrieved 2007-10-12. 
  3. ^ "The MeanPlane (Invariable plane) of the Solar System passing through the barycenter". 3 April 2009. Retrieved 2009-04-10.  (produced with Solex 10 written by Aldo Vitagliano; see also Invariable plane)
  4. ^ Yeomans, Donald K. "HORIZONS Web-Interface for Venus (Major Body=2)". JPL Horizons On-Line Ephemeris System. —Select "Ephemeris Type: Orbital Elements", "Time Span: 2000-01-01 12:00 to 2000-01-02". ("Target Body: Venus" and "Center: Sun" should be defaulted to.) Results are instantaneous osculating values at the precise J2000 epoch.
  5. ^ a b Seidelmann, P. Kenneth; Archinal, B. A.; A'hearn, M. F. et al. (2007). "Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006". Celestial Mechanics and Dynamical Astronomy 98 (3): 155–180. Bibcode:2007CeMDA..98..155S. doi:10.1007/s10569-007-9072-y.  edit
  6. ^ "Report on the IAU/IAG Working Group on cartographic coordinates and rotational elements of the planets and satellites". International Astronomical Union. 2000. Retrieved 2007-04-12. 
  7. ^ a b Mallama, A.; Wang, D.; Howard, R.A. (2006). "Venus phase function and forward scattering from H2SO4". Icarus 182 (1): 10–22. Bibcode:2006Icar..182...10M. doi:10.1016/j.icarus.2005.12.014. 
  8. ^ a b Mallama, A. (2011). "Planetary magnitudes". Sky and Telescope 121 (1): 51–56. 
  9. ^ a b "HORIZONS Web-Interface for Venus (Major Body=299)". JPL Horizons On-Line Ephemeris System. 2006-Feb-27 (GEOPHYSICAL DATA). Retrieved 2010-11-28.  (Using JPL Horizons you can see that on 2013-Dec-08 Venus will have an apmag of −4.89)
  10. ^ a b c Espenak, Fred (1996). "Venus: Twelve year planetary ephemeris, 1995–2006". NASA Reference Publication 1349. NASA/Goddard Space Flight Center. Retrieved 2006-06-20. 
  11. ^ a b "Venus: Facts & Figures". NASA. Retrieved 2007-04-12. 
  12. ^ Lawrence, Pete (2005). "The Shadow of Venus". Retrieved 13 June 2012. 
  13. ^ Hashimoto, G. L.; Roos-Serote, M.; Sugita, S.; Gilmore, M. S.; Kamp, L. W.; Carlson, R. W.; Baines, K. H. (2008). "Felsic highland crust on Venus suggested by Galileo Near-Infrared Mapping Spectrometer data". Journal of Geophysical Research, Planets 113: E00B24. Bibcode:2008JGRE..11300B24H. doi:10.1029/2008JE003134. 
  14. ^ David Shiga Did Venus's ancient oceans incubate life?, New Scientist, 10 October 2007
  15. ^ B.M. Jakosky, "Atmospheres of the Terrestrial Planets", in Beatty, Petersen and Chaikin (eds,), The New Solar System, 4th edition 1999, Sky Publishing Company (Boston) and Cambridge University Press (Cambridge), pp. 175–200
  16. ^ "Caught in the wind from the Sun". ESA (Venus Express). 28 November 2007. Retrieved 2008-07-12. 
  17. ^ Lopes, Rosaly M. C.; Gregg, Tracy K. P. (2004). Volcanic worlds: exploring the Solar System's volcanoes. Springer. p. 61. ISBN 3-540-00431-9. 
  18. ^ "Atmosphere of Venus". The Encyclopedia of Astrobiology, Astronomy, and Spaceflght. Retrieved 2007-04-29. 
  19. ^ Esposito, Larry W. (9 March 1984). "Sulfur Dioxide: Episodic Injection Shows Evidence for Active Venus Volcanism". Science 223 (4640): 1072–1074. Bibcode:1984Sci...223.1072E. doi:10.1126/science.223.4640.1072. PMID 17830154. Retrieved 2009-04-29. 
  20. ^ Bullock, Mark A.; Grinspoon, David H. (March 2001). "The Recent Evolution of Climate on Venus". Icarus 150 (1): 19–37. Bibcode:2001Icar..150...19B. doi:10.1006/icar.2000.6570. 
  21. ^ Basilevsky, Alexander T.; Head, James W., III (1995). "Global stratigraphy of Venus: Analysis of a random sample of thirty-six test areas". Earth, Moon, and Planets 66 (3): 285–336. Bibcode:1995EM&P...66..285B. doi:10.1007/BF00579467. 
  22. ^ Kaufmann, W. J. (1994). Universe. New York: W. H. Freeman. p. 204. ISBN 0-7167-2379-4. 
  23. ^ a b c d Nimmo, F.; McKenzie, D. (1998). "Volcanism and Tectonics on Venus". Annual Review of Earth and Planetary Sciences 26 (1): 23–53. Bibcode:1998AREPS..26...23N. doi:10.1146/annurev.earth.26.1.23. 
  24. ^ a b Strom, R. G.; Schaber, G. G.; Dawsow, D. D. (1994). "The global resurfacing of Venus". Journal of Geophysical Research 99 (E5): 10899–10926. Bibcode:1994JGR....9910899S. doi:10.1029/94JE00388. 
  25. ^ a b c d Frankel, Charles (1996). Volcanoes of the Solar System. Cambridge University Press. ISBN 0-521-47770-0. 
  26. ^ Batson, R.M.; Russell J. F. (18–22 March 1991). "Naming the Newly Found Landforms on Venus" (PDF). Procedings of the Lunar and Planetary Science Conference XXII. Houston, Texas. p. 65. Retrieved 2009-07-12. 
  27. ^ a b Young, C., ed. (August 1990). The Magellan Venus Explorer's Guide (JPL Publication 90-24 ed.). California: Jet Propulsion Laboratory. 
  28. ^ Davies, M. E.; Abalakin, V. K.; Bursa, M.; Lieske, J. H.; Morando, B.; Morrison, D.; Seidelmann, P. K.; Sinclair, A. T. et al. (1994). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites". Celestial Mechanics and Dynamical Astronomy 63 (2): 127. Bibcode:1996CeMDA..63..127D. doi:10.1007/BF00693410. 
  29. ^ "USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE)". Retrieved 22 October 2009. 
  30. ^ "The Magellan Venus Explorer's Guide". Retrieved 22 October 2009. 
  31. ^ Karttunen, Hannu; Kroger, P.; Oja, H.; Poutanen, M.; Donner, K. J. (2007). Fundamental Astronomy. Springer. p. 162. ISBN 3-540-34143-9. 
  32. ^ "Venus also zapped by lightning". CNN. 29 November 2007. Archived from the original on 30 November 2007. Retrieved 2007-11-29. 
  33. ^ Glaze, L. S. (1999). "Transport of SO2 by explosive volcanism on Venus". Journal of Geophysical Research 104 (E8): 18899–18906. Bibcode:1999JGR...10418899G. doi:10.1029/1998JE000619. Retrieved 2009-01-16. 
  34. ^ Romeo, I.; Turcotte, D. L. (2009). "The frequency-area distribution of volcanic units on Venus: Implications for planetary resurfacing". Icarus 203 (1): 13. Bibcode:2009Icar..203...13R. doi:10.1016/j.icarus.2009.03.036. 
  35. ^ Herrick, R. R.; Phillips, R. J. (1993). "Effects of the Venusian atmosphere on incoming meteoroids and the impact crater population". Icarus 112 (1): 253–281. Bibcode:1994Icar..112..253H. doi:10.1006/icar.1994.1180. 
  36. ^ David Morrison (2003). The Planetary System. Benjamin Cummings. ISBN 0-8053-8734-X. 
  37. ^ Goettel, K. A.; Shields, J. A.; Decker, D. A. (16–20 March 1981). "Density constraints on the composition of Venus". Proceedings of the Lunar and Planetary Science Conference. Houston, TX: Pergamon Press. pp. 1507–1516. Retrieved 2009-07-12. 
  38. ^ Faure, Gunter; Mensing, Teresa M. (2007). Introduction to planetary science: the geological perspective. Springer eBook collection. Springer. p. 201. ISBN 1-4020-5233-2. 
  39. ^ Nimmo, F. (2002). "Crustal analysis of Venus from Magellan satellite observations at Atalanta Planitia, Beta Regio, and Thetis Regio". Geology 30 (11): 987–990. Bibcode:2002Geo....30..987N. doi:10.1130/0091-7613(2002)030<0987:WDVLAM>2.0.CO;2. ISSN 0091-7613. 
  40. ^ "Venus". Case Western Reserve University. 13 September 2006. Retrieved 2011-12-21. 
  41. ^ Lewis, John S. (2004). Physics and Chemistry of the Solar System (2nd ed.). Academic Press. p. 463. ISBN 0-12-446744-X. 
  42. ^ Henry Bortman (2004). "Was Venus Alive? 'The Signs are Probably There'". space.com. Retrieved 2010-07-31. 
  43. ^ Grinspoon, David H.; Bullock, M. A. (October 2007). "Searching for Evidence of Past Oceans on Venus". Bulletin of the American Astronomical Society 39: 540. Bibcode:2007DPS....39.6109G 
  44. ^ Kasting, J. F. (1988). "Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus". Icarus 74 (3): 472–494. Bibcode:1988Icar...74..472K. doi:10.1016/0019-1035(88)90116-9. PMID 11538226. 
  45. ^ Venusian Cloud Colonies :: Astrobiology Magazine
  46. ^ Geoffrey A. Landis Astrobiology: The Case for Venus
  47. ^ Cockell, C. S. (December 1999). "Life on Venus". Planetary and Space Science 47 (12): 1487–1501. Bibcode:1999P&SS...47.1487C. doi:10.1016/S0032-0633(99)00036-7. 
  48. ^ Moshkin, B. E.; Ekonomov, A. P.; Golovin Iu. M. (1979). "Dust on the surface of Venus". Kosmicheskie Issledovaniia (Cosmic Research) 17: 280–285. Bibcode:1979CoRe...17..232M. 
  49. ^ Krasnopolsky, V. A.; Parshev, V. A. (1981). "Chemical composition of the atmosphere of Venus". Nature 292 (5824): 610–613. Bibcode:1981Natur.292..610K. doi:10.1038/292610a0. 
  50. ^ Krasnopolsky, Vladimir A. (2006). "Chemical composition of Venus atmosphere and clouds: Some unsolved problems". Planetary and Space Science 54 (13–14): 1352–1359. Bibcode:2006P&SS...54.1352K. doi:10.1016/j.pss.2006.04.019. 
  51. ^ W. B., Rossow; A. D., del Genio; T., Eichler (1990). "Cloud-tracked winds from Pioneer Venus OCPP images" (PDF). Journal of the Atmospheric Sciences 47 (17): 2053–2084. Bibcode:1990JAtS...47.2053R. doi:10.1175/1520-0469(1990)047<2053:CTWFVO>2.0.CO;2. ISSN 1520-0469. 
  52. ^ Normile, Dennis (7 May 2010). "Mission to probe Venus's curious winds and test solar sail for propulsion". Science 328 (5979): 677. Bibcode:2010Sci...328..677N. doi:10.1126/science.328.5979.677-a. PMID 20448159. 
  53. ^ Lorenz, Ralph D.; Lunine, Jonathan I.; Withers, Paul G.; McKay, Christopher P. (2001). "Titan, Mars and Earth: Entropy Production by Latitudinal Heat Transport" (PDF). Ames Research Center, University of Arizona Lunar and Planetary Laboratory. Retrieved 2007-08-21. 
  54. ^ "Interplanetary Seasons". NASA. Retrieved 2007-08-21. 
  55. ^ Otten, Carolyn Jones (2004). ""Heavy metal" snow on Venus is lead sulfide". Washington University in St Louis. Retrieved 2007-08-21. 
  56. ^ a b Russell, S. T.; Zhang, T. L.; Delva, M.; Magnes, W.; Strangeway, R. J.; Wei, H. Y. (2007). "Lightning on Venus inferred from whistler-mode waves in the ionosphere". Nature 450 (7170): 661–662. Bibcode:2007Natur.450..661R. doi:10.1038/nature05930. PMID 18046401. 
  57. ^ Hand, Eric (November 2007). "European mission reports from Venus". Nature (450): 633–660. doi:10.1038/news.2007.297. 
  58. ^ Staff (28 November 2007). "Venus offers Earth climate clues". BBC News. Retrieved 2007-11-29. 
  59. ^ "ESA finds that Venus has an ozone layer too". ESA. 6 October 2011. Retrieved 2011-12-25. 
  60. ^ Staff (January 29, 2013). "When A Planet Behaves Like A Comet". ESA. Retrieved January 31, 2013. 
  61. ^ Kramer, Miriam (January 30, 2013). "Venus Can Have 'Comet-Like' Atmosphere". Space.com. Retrieved January 31, 2013. 
  62. ^ a b "The HITRAN Database". Atomic and Molecular Physics Division, Harvard-Smithsonian Center for Astrophysics. Retrieved 8 August 2012. "HITRAN is a compilation of spectroscopic parameters that a variety of computer codes use to predict and simulate the transmission and emission of light in the atmosphere." 
  63. ^ a b "Hitran on the Web Information System". Harvard-Smithsonian Center for Astrophysics (CFA), Cambridge, MA, USA; V.E. Zuev Insitute of Atmosperic Optics (IAO), Tomsk, Russia. Retrieved 11 August 2012. 
  64. ^ Dolginov, Nature of the Magnetic Field in the Neighborhood of Venus, COsmic Research, 1969
  65. ^ Kivelson G. M., Russell, C. T. (1995). Introduction to Space Physics. Cambridge University Press. ISBN 0-521-45714-9. 
  66. ^ Upadhyay, H. O.; Singh, R. N. (April 1995). "Cosmic ray Ionization of Lower Venus Atmosphere". Advances in Space Research 15 (4): 99–108. Bibcode:1995AdSpR..15...99U. doi:10.1016/0273-1177(94)00070-H. 
  67. ^ Luhmann J. G., Russell C. T. (1997). "Venus: Magnetic Field and Magnetosphere". In J. H. Shirley and R. W. Fainbridge. Encyclopedia of Planetary Sciences (Chapman and Hall, New York). ISBN 978-1-4020-4520-2. Retrieved 2009-06-28. 
  68. ^ Stevenson, D. J. (15 March 2003). "Planetary magnetic fields". Earth and Planetary Science Letters 208 (1–2): 1–11. Bibcode:2003E&PSL.208....1S. doi:10.1016/S0012-821X(02)01126-3. 
  69. ^ a b Nimmo, Francis (November 2002). "Why does Venus lack a magnetic field?" (PDF). Geology 30 (11): 987–990. Bibcode:2002Geo....30..987N. doi:10.1130/0091-7613(2002)030<0987:WDVLAM>2.0.CO;2. ISSN 0091-7613. Retrieved 2009-06-28. 
  70. ^ Konopliv, A. S.; Yoder, C. F. (1996). "Venusian k2 tidal Love number from Magellan and PVO tracking data". Geophysical Research Letters 23 (14): 1857–1860. Bibcode:1996GeoRL..23.1857K. doi:10.1029/96GL01589. Retrieved 2009-07-12. 
  71. ^ Svedhem, Håkan; Titov, Dmitry V.; Taylor, Fredric W.; Witasse, Olivier (November 2007). "Venus as a more Earth-like planet". Nature 450 (7170): 629–632. Bibcode:2007Natur.450..629S. doi:10.1038/nature06432. PMID 18046393. 
  72. ^ "Venus Close Approaches to Earth as predicted by Solex 11". Retrieved 2009-03-19.  (numbers generated by Solex)
  73. ^ Bakich, Michael E. (2000). The Cambridge planetary handbook. Cambridge University Press. p. 50. ISBN 0-521-63280-3. 
  74. ^ "Could Venus be shifting gear?". European Space Agency. 10 February 2012. Retrieved 19 August 2012. 
  75. ^ a b "Space Topics: Compare the Planets: Mercury, Venus, Earth, The Moon, and Mars". Planetary Society. Retrieved 2007-04-12. 
  76. ^ Correia, Alexandre C. M.; Laskar, Jacques; de Surgy, Olivier Néron (May 2003). "Long-term evolution of the spin of Venus I. theory" (PDF). Icarus 163 (1): 1–23. Bibcode:2003Icar..163....1C. doi:10.1016/S0019-1035(03)00042-3. 
  77. ^ Correia, A. C. M.; Laskar, J. (2003). "Long-term evolution of the spin of Venus: II. numerical simulations" (PDF). Icarus 163 (1): 24–45. Bibcode:2003Icar..163...24C. doi:10.1016/S0019-1035(03)00043-5. 
  78. ^ Gold, T.; Soter, S. (1969). "Atmospheric tides and the resonant rotation of Venus". Icarus 11 (3): 356–366. Bibcode:1969Icar...11..356G. doi:10.1016/0019-1035(69)90068-2. 
  79. ^ Shapiro, I. I.; Campbell, D. B.; de Campli, W. M. (June 1979). "Nonresonance rotation of Venus". Astrophysical Journal, Part 2 – Letters to the Editor 230: L123–L126. Bibcode:1979ApJ...230L.123S. doi:10.1086/182975 
  80. ^ a b Sheppard, Scott S.; Trujillo, Chadwick A. (July 2009). "A survey for satellites of Venus". Icarus 202 (1): 12–16. arXiv:0906.2781. Bibcode:2009Icar..202...12S. doi:10.1016/j.icarus.2009.02.008. 
  81. ^ Mikkola, S.; Brasser, R.; Wiegert, P.; Innanen, K. (July 2004). "Asteroid 2002 VE68, a quasi-satellite of Venus". Monthly Notices of the Royal Astronomical Society 351 (3): L63. Bibcode:2004MNRAS.351L..63M. doi:10.1111/j.1365-2966.2004.07994.x. 
  82. ^ de la Fuente Marcos, C.; de la Fuente Marcos, R. (November 2012). "On the dynamical evolution of 2002 VE68". Monthly Notices of the Royal Astronomical Society 427 (1): 728. arXiv:1208.4444. Bibcode:2012MNRAS.427..728D. doi:10.1111/j.1365-2966.2012.21936.x. 
  83. ^ de la Fuente Marcos, C.; de la Fuente Marcos, R. "Asteroid 2012 XE133, a transient companion to Venus". Monthly Notices of the Royal Astronomical Society 432 (2): 886–893. arXiv:1303.3705. Bibcode:2013MNRAS.432..886D. doi:10.1093/mnras/stt454. 
  84. ^ Musser, George (10 October 2006). "Double Impact May Explain Why Venus Has No Moon". Scientific American. Retrieved 2011-12-05. 
  85. ^ Tytell, David (10 October 2006). "Why Doesn't Venus Have a Moon?". SkyandTelescope.com. Retrieved 2007-08-03. 
  86. ^ Tony Flanders (25 February 2011). "See Venus in Broad Daylight!". Sky & Telescope. 
  87. ^ Krystek, Lee. "Natural Identified Flying Objects". The Unngatural Museum. Retrieved 2006-06-20. 
  88. ^ Anon. "Transit of Venus". History. University of Central Lancashire. Retrieved 14 May 2012. 
  89. ^ A. Boyle – Venus transit: A last-minute guide – MSNBC
  90. ^ Espenak, Fred (2004). "Transits of Venus, Six Millennium Catalog: 2000 BCE to 4000 CE". Transits of the Sun. NASA. Retrieved 2009-05-14. 
  91. ^ Kollerstrom, Nicholas (1998). "Horrocks and the Dawn of British Astronomy". University College London. Retrieved 11 May 2012. 
  92. ^ Hornsby, T. (1771). "The quantity of the Sun's parallax, as deduced from the observations of the transit of Venus on June 3, 1769". Philosophical Transactions of the Royal Society 61 (0): 574–579. doi:10.1098/rstl.1771.0054. 
  93. ^ Woolley, Richard (1969). "Captain Cook and the Transit of Venus of 1769". Notes and Records of the Royal Society of London 24 (1): 19–32. doi:10.1098/rsnr.1969.0004. ISSN 0035-9149. JSTOR 530738. 
  94. ^ Baum, R. M. (2000). "The enigmatic ashen light of Venus: an overview". Journal of the British Astronomical Association 110: 325. Bibcode:2000JBAA..110..325B. 
  95. ^ Waerden, Bartel (1974). Science awakening II: the birth of astronomy. Springer. p. 56. ISBN 90-01-93103-0. Retrieved 2011-01-10. 
  96. ^ Pliny the Elder (1991). Natural History II:36–37. translated by John F. Healy. Harmondsworth, Middlesex, UK: Penguin. pp. 15–16. 
  97. ^ Goldstein, Bernard R. (March 1972). "Theory and Observation in Medieval Astronomy". Isis (University of Chicago Press) 63 (1): 39–47 [44]. doi:10.1086/350839. 
  98. ^ Sally P. Ragep (2007). "Ibn Sīnā: Abū ʿAlī al‐Ḥusayn ibn ʿAbdallāh ibn Sīnā". In Thomas Hockey. The Biographical Encyclopedia of Astronomers. Springer Science+Business Media. pp. 570–572. 
  99. ^ S. M. Razaullah Ansari (2002). History of oriental astronomy: proceedings of the joint discussion-17 at the 23rd General Assembly of the International Astronomical Union, organised by the Commission 41 (History of Astronomy), held in Kyoto, August 25–26, 1997. Springer. p. 137. ISBN 1-4020-0657-8. 
  100. ^ Kollerstrom, Nicholas (2004). "William Crabtree's Venus transit observation". Proceedings IAU Colloquium No. 196, 2004. International Astronomical Union. Retrieved 10 May 2012. 
  101. ^ Anonymous. "Galileo: the Telescope & the Laws of Dynamics". Astronomy 161; The Solar System. Department Physics & Astronomy, University of Tennessee. Retrieved 2006-06-20. 
  102. ^ Marov, Mikhail Ya. (2004). "Mikhail Lomonosov and the discovery of the atmosphere of Venus during the 1761 transit". In D.W. Kurtz. Proceedings of IAU Colloquium No. 196 (Preston, U.K.: Cambridge University Press): 209–219. doi:10.1017/S1743921305001390. 
  103. ^ "Mikhail Vasilyevich Lomonosov". Britannica online encyclopedia. Encyclopædia Britannica, Inc. Retrieved 2009-07-12. 
  104. ^ Russell, H. N. (1899). "The Atmosphere of Venus". Astrophysical Journal 9: 284–299. Bibcode:1899ApJ.....9..284R. doi:10.1086/140593. 
  105. ^ Hussey, T. (1832). "On the Rotation of Venus". Monthly Notices of the Royal Astronomical Society 2: 78–126. Bibcode:1832MNRAS...2...78H. 
  106. ^ Ross, F. E. (1928). "Photographs of Venus". Astrophysical Journal. 68–92: 57. Bibcode:1928ApJ....68...57R. doi:10.1086/143130. 
  107. ^ Slipher, V. M. (1903). "A Spectrographic Investigation of the Rotation Velocity of Venus". Astronomische Nachrichten 163 (3–4): 35. Bibcode:1903AN....163...35S. doi:10.1002/asna.19031630303. 
  108. ^ Goldstein, R. M.; Carpenter, R. L. (1963). "Rotation of Venus: Period Estimated from Radar Measurements". Science 139 (3558): 910–911. Bibcode:1963Sci...139..910G. doi:10.1126/science.139.3558.910. PMID 17743054. 
  109. ^ Campbell, D. B.; Dyce, R. B.; Pettengill G. H. (1976). "New radar image of Venus". Science 193 (4258): 1123–1124. Bibcode:1976Sci...193.1123C. doi:10.1126/science.193.4258.1123. PMID 17792750. 
  110. ^ Carolynn Young (August 1990). "Chapter 8, What's in a Name?". The Magellan Venus Explorer's Guide. NASA/JPL. Retrieved 2009-07-21. 
  111. ^ Mitchell, Don (2003). "Inventing The Interplanetary Probe". The Soviet Exploration of Venus. Retrieved 2007-12-27. 
  112. ^ Mayer, McCullough, and Sloanaker; McCullough; Sloanaker (January 1958). "Observations of Venus at 3.15-cm Wave Length". Astrophysical Journal (The Astrophysical Journal) 127: 1. Bibcode:1958ApJ...127....1M. doi:10.1086/146433. 
  113. ^ Jet Propulsion Laboratory (1962). Mariner-Venus 1962 Final Project Report (PDF). SP-59. NASA. 
  114. ^ a b c d Mitchell, Don (2003). "Plumbing the Atmosphere of Venus". The Soviet Exploration of Venus. Retrieved 2007-12-27. 
  115. ^ Eshleman, V.; Fjeldbo, G.; Eshleman (1969). "The atmosphere of Venus as studied with the Mariner 5 dual radio-frequency occultation experiment" (PDF). Radio Science. SU-SEL-69-003 (NASA) 4 (10): 879. Bibcode:1969RaSc....4..879F. doi:10.1029/RS004i010p00879. 
  116. ^ "Report on the Activities of the COSPAR Working Group VII". Preliminary Report, COSPAR Twelfth Plenary Meeting and Tenth International Space Science Symposium. Prague, Czechoslovakia: National Academy of Sciences. 11–24 May 1969. p. 94. 
  117. ^ Sagdeev, Roald; Eisenhower, Susan (28 May 2008). "United States-Soviet Space Cooperation during the Cold War". Retrieved 2009-07-19. 
  118. ^ Mitchell, Don (2003). "First Pictures of the Surface of Venus". The Soviet Exploration of Venus. Retrieved 2007-12-27. 
  119. ^ Dunne, J.; Burgess, E. (1978). The Voyage of Mariner 10 (PDF). SP-424. NASA. Retrieved 2009-07-12. 
  120. ^ Colin, L.; Hall, C. (1977). "The Pioneer Venus Program". Space Science Reviews 20 (3): 283–306. Bibcode:1977SSRv...20..283C. doi:10.1007/BF02186467. 
  121. ^ Williams, David R. (6 January 2005). "Pioneer Venus Project Information". NASA Goddard Space Flight Center. Retrieved 2009-07-19. 
  122. ^ a b c Mitchell, Don (2003). "Drilling into the Surface of Venus". The Soviet Exploration of Venus. Retrieved 2007-12-27. 
  123. ^ Greeley, Ronald; Batson, Raymond M. (2007). Planetary Mapping. Cambridge University Press. p. 47. ISBN 978-0-521-03373-2. Retrieved 2009-07-19. 
  124. ^ Linkin, V.; Blamont, J.; Preston, R. (1985). "The Vega Venus Balloon experiment". Bulletin of the American Astronomical Society 17: 722. Bibcode:1985BAAS...17..722L. 
  125. ^ Sagdeev, R. Z.; Linkin, V. M.; Blamont, J. E.; Preston, R. A. (1986). "The VEGA Venus Balloon Experiment". Science 231 (4744): 1407–1408. Bibcode:1986Sci...231.1407S. doi:10.1126/science.231.4744.1407. JSTOR 1696342. PMID 17748079. 
  126. ^ Lyons, Daniel T.; Saunders, R. Stephen; Griffith, Douglas G. (May–June 1995). "The Magellan Venus mapping mission: Aerobraking operations". Acta Astronautica 35 (9–11): 669–676. doi:10.1016/0094-5765(95)00032-U. 
  127. ^ "Magellan begins termination activities". JPL Universe. 9 September 1994. Retrieved 2009-07-30. 
  128. ^ Van Pelt, Michel (2006). Space invaders: how robotic spacecraft explore the Solar System. Springer. pp. 186–189. ISBN 0-387-33232-4. 
  129. ^ Davis, Andrew M.; Holland, Heinrich D.; Turekian, Karl K. (2005). Meteorites, comets, and planets. Elsevier. p. 489. ISBN 0-08-044720-1. 
  130. ^ "Timeline". MESSENGER. Retrieved 9 February 2008. 
  131. ^ a b "Venus Express". ESA Portal. European Space Agency. Retrieved 9 February 2008. 
  132. ^ G. A. Landis, "Robotic Exploration of the Surface and Atmosphere of Venus", paper IAC-04-Q.2.A.08, Acta Astronautica, Vol. 59, 7, 517–580 (October 2006). See animation
  133. ^ "Venus Climate Orbiter "PLANET-C"". JAXA. Retrieved 9 February 2008. 
  134. ^ "BepiColombo". ESA Spacecraft Operations. Retrieved 9 February 2008. 
  135. ^ "New Frontiers missions 2009". NASA. Retrieved 2011-12-09. 
  136. ^ "Atmospheric Flight on Venus". NASA Glenn Research Center Technical Reports. Retrieved 18 September 2008. 
  137. ^ a b Feldman, M. S.; Ferrara, L. A.; Havenstein, P. L.; Volonte, J. E.; Whipple, P. H. (1967). Manned Venus Flyby, February 1, 1967 (PDF). Bellcomm, Inc. 
  138. ^ a b Chronology of Venus Exploration (NASA)
  139. ^ Nicholson, Seth B. (1961). "The Trojan Asteroids". Astronomical Society of the Pacific Leaflets 8: 239. Bibcode:1961ASPL....8..239N. 
  140. ^ Cessna, Abby. "Mythology of the Planets". Universe Today. Fraser Cain. Retrieved 19 September 2011. 
  141. ^ a b c Stearn, William (May 1968). "The Origin of the Male and Female Symbols of Biology". Taxon 11 (4): 109–113. doi:10.2307/1217734. JSTOR 1217734. 
  142. ^ Sachs, A. (1974). "Babylonian Observational Astronomy". Philosophical Transactions of the Royal Society of London 276 (1257): 43–50. Bibcode:1974RSPTA.276...43S. doi:10.1098/rsta.1974.0008. 
  143. ^ Meador, Betty De Shong (2000). Inanna, Lady of Largest Heart: Poems of the Sumerian High Priestess Enheduanna. University of Texas Press. p. 15. ISBN 0-292-75242-3. 
  144. ^ Littleton, C. Scott (2005). Gods, Goddesses, and Mythology 6. Marshall Cavendish. p. 760. ISBN 0761475656. 
  145. ^ Cattermole, Peter John; Moore, Patrick (1997). Atlas of Venus. Cambridge University Press. p. 9. ISBN 0-521-49652-7. 
  146. ^ Fox, William Sherwood (1916). The Mythology of All Races: Greek and Roman. Marshall Jones Company. p. 247. ISBN 0-8154-0073-X. Retrieved 2009-05-16. 
  147. ^ Greene, Ellen (1996). Reading Sappho: contemporary approaches. University of California Press. p. 54. ISBN 0-520-20601-0. 
  148. ^ Greene, Ellen (1999). Reading Sappho: contemporary approaches. University of California Press. p. 54. ISBN 0-520-20601-0. 
  149. ^ "Greek Names of the Planets". Retrieved 2012-07-14. "Aphrodite is the Greek name of the planet Venus, which is named after Aphrodite, the goddess of Love."  See also the Greek article about the planet.
  150. ^ Guillemin, Amédée; Lockyer, Norman; Proctor, Richard Anthony (1878). The heavens: an illustrated handbook of popular astronomy. London: Richard Bentley & Son. p. 67. Retrieved 2009-05-16. 
  151. ^ Rees, Roger (2002). Layers of loyalty in Latin panegyric, AD 289–307. Oxford University Press. p. 112. ISBN 0-19-924918-0. 
  152. ^ Boyce, Mary. "ANĀHĪD". Encyclopaedia Iranica. Center for Iranian Studies, Columbia University. Archived from the original on 1 May 2008. Retrieved 2010-02-20. 
  153. ^ Schmidt, Hanns-Peter. "MITHRA". Encyclopaedia Iranica. Center for Iranian Studies, Columbia University. Archived from the original on 12 July 2008. Retrieved 2010-02-20. 
  154. ^ MacKenzie, D. N. (2005). A concise Pahlavi Dictionary. London & New York: Routledge Curzon. ISBN 0-19-713559-5. 
  155. ^ Mo'in, M. (1992). A Persian Dictionary. Six Volumes 5–6. Tehran: Amir Kabir Publications. ISBN 1-56859-031-8. 
  156. ^ Sharer, Robert J.; Traxler, Loa P. (2005). The Ancient Maya. Stanford University Press. ISBN 0-8047-4817-9. 
  157. ^ Verhaag, G. (2000). "Letters to the Editor: Cross-cultural astronomy". Journal of the British Astronomical Association 110 (1): 49. Bibcode:2000JBAA..110...49V. 
  158. ^ Norris, Ray P. (2004). "Searching for the Astronomy of Aboriginal Australians" (PDF). Conference Proceedings. Australia Telescope National Facility. pp. 1–4. Retrieved 2009-05-16. 
  159. ^ Weltfish, Gene (1965 / reprint 1977). The Lost Universe: Pawnee Life and Culture (Chapter 10: The Captive Girl Sacrifice). University of Nebraska Press. p. 117. ISBN 978-0-8032-5871-6. 
  160. ^ Bailey, Michael David (2007). Magic and Superstition in Europe: a Concise History from Antiquity to the Present. Rowman & Littlefield. pp. 93–94. ISBN 0-7425-3387-5. 
  161. ^ Bhalla, Prem P. (2006). Hindu Rites, Rituals, Customs and Traditions: A to Z on the Hindu Way of Life. Pustak Mahal. p. 29. ISBN 81-223-0902-X. 
  162. ^ Behari, Bepin; Frawley, David (2003). Myths & Symbols of Vedic Astrology (2 ed.). Lotus Press. pp. 65–74. ISBN 0-940985-51-9. 
  163. ^ China: De Groot, Jan Jakob Maria (1912). "Religion in China: universism. a key to the study of Taoism and Confucianism". American lectures on the history of religions 10 (G. P. Putnam's Sons). p. 300. Retrieved 2010-01-08. 
    Japan: Crump, Thomas (1992). "The Japanese numbers game: the use and understanding of numbers in modern Japan". Nissan Institute/Routledge Japanese studies series (Routledge). pp. 39–40. ISBN 0415056098. 
    Korea: Hulbert, Homer Bezaleel (1909). The passing of Korea. Doubleday, Page & company. p. 426. Retrieved 2010-01-08. 
  164. ^ Powell, Arthor E. (1930). The Solar System. London: The Theosophical Publishing House. p. 33. ISBN 0-7873-1153-7. 
  165. ^ Leadbeater, C.W. The Masters and the Path Adyar, Madras, India: 1925—Theosophical Publishing House (in this book, Sanat Kumara is referred to as Lord of the World.) See in index under "Lord of the World".
  166. ^ Miller, Ron (2003). Venus. Twenty-First Century Books. p. 12. ISBN 0-7613-2359-7. 
  167. ^ Dick, Steven (2001). Life on Other Worlds: The 20th-Century Extraterrestrial Life Debate. Cambridge University Press. p. 43. ISBN 0-521-79912-0. 
  168. ^ Seed, David (2005). A Companion to Science Fiction. Blackwell Publishing. pp. 134–135. ISBN 1-4051-1218-2. 
  169. ^ Ellenberger, C. Leroy (Winter 1984). "Worlds in Collision in Macmillan's Catalogues". Kronos 9 (2). Retrieved 2009-05-16.  The 20 weeks at the top stated by Juergens in The Velikovsky Affair is incorrect.
  170. ^ a b c Landis, Geoffrey A. (2003). "Colonization of Venus". AIP Conference Proceedings 654 (1). pp. 1193–1198. doi:10.1063/1.1541418. 

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