Venus is the second planet from the Sun, orbiting it every 224.7 Earth
days. It has the longest rotation period (243 days) of any planet
Solar System and rotates in the opposite direction to most
other planets (meaning the
Sun would rise in the west and set in the
east). It does not have any natural satellites. It is named after
the Roman goddess of love and beauty. It is the second-brightest
natural object in the night sky after the Moon, reaching an apparent
magnitude of −4.6 – bright enough to cast shadows at night and,
rarely, visible to the naked eye in broad daylight. Orbiting
within Earth's orbit,
Venus is an inferior planet and never appears to
venture far from the Sun; its maximum angular distance from the Sun
(elongation) is 47.8°.
Venus is a terrestrial planet and is sometimes called Earth's "sister
planet" because of their similar size, mass, proximity to the Sun, and
bulk composition. It is radically 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, or roughly
the pressure found 900 m (3,000 ft) underwater on Earth.
Venus is by far the hottest planet in the Solar System, with a mean
surface temperature of 735 K (462 °C; 863 °F), even
though Mercury is closer to the Sun.
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. It may have had
water oceans in the past, but these would have vaporized as
the temperature rose due to a runaway greenhouse effect. The water
has probably photodissociated, and the free hydrogen has been swept
into interplanetary space by the solar wind because of the lack of a
planetary magnetic field. Venus's surface is a dry desertscape
interspersed with slab-like rocks and is periodically resurfaced by
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, and has been a prime
inspiration for writers and poets as the morning star and evening
Venus was the first planet to have its motions plotted across
the sky, as early as the second millennium BC.
As the closest planet to Earth,
Venus has been a prime target for
early interplanetary exploration. It was the first planet beyond Earth
visited by a spacecraft (
Mariner 2 in 1962), and the first to be
successfully landed on (by
Venera 7 in 1970). Venus's thick clouds
render observation of its surface impossible in visible light, and the
first detailed maps did not emerge until the arrival of the Magellan
orbiter in 1991. Plans have been proposed for rovers or more complex
missions, but they are hindered by Venus's hostile surface conditions.
1 Physical characteristics
1.2 Surface geology
1.3 Internal structure
Atmosphere and climate
Magnetic field and core
2 Orbit and rotation
3.3 Pentagram of Venus
3.4 Daylight apparitions
3.5 Ashen light
4.1 Early studies
4.2 Ground-based research
5 In culture
7 See also
10 External links
10.1 Cartographic resources
Size comparison with Earth
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
size and mass, and is often described as Earth's "sister" or
"twin". 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%
Main article: Mapping of Venus
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. 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 some recent eruptions.
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. 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. 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
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, approximately
300–600 million years old.
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.
Most Venusian surface features are named after historical and
mythological women. Exceptions are Maxwell Montes, named after
James Clerk Maxwell, and highland regions Alpha Regio, Beta Regio, and
Ovda Regio. The latter three features were named before the current
system was adopted by the International Astronomical Union, the body
which oversees planetary nomenclature.
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 centre of the oval feature Eve, located south
of Alpha Regio. After the
Venera missions were completed, the
prime meridian was redefined to pass through the central peak in the
Geology of Venus
Geology of Venus and Volcanology of Venus
False-colour image of
Maat Mons with a vertical exaggeration of 22.5
Much of the Venusian surface appears to have been shaped by volcanic
Venus has several times as many volcanoes as Earth, and it
has 167 large volcanoes that are over 100 km (62 mi) across.
The only volcanic complex of this size on
Earth is the Big Island of
Hawaii.:154 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, whereas
the Venusian surface is estimated to be 300–600 million years
Several lines of evidence point to ongoing volcanic activity on Venus.
During the Soviet
Venera program, the
Venera 9 orbiter obtained
spectroscopic evidence of lightning on Venus, and the
descent probe obtained additional evidence of lightning and
thunder. The European Space Agency's
Venus Express in 2007
detected whistler waves further confirming the occurrence of lightning
on Venus. 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, jumped in 2006, and
again declined 10-fold. This may mean that levels had been boosted
several times by large volcanic eruptions.
In 2008 and 2009, the first direct evidence for ongoing volcanism was
Venus Express, in the form of four transient localized
infrared hot spots within the rift zone Ganis Chasma,[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. 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).
Impact craters on the surface of
Venus (false-colour image
reconstructed from radar data)
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 about 300–600 million years ago, followed
by a decay in volcanism. Whereas Earth's crust is in continuous
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.
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 down so much by the
atmosphere that they do not create an impact crater. Incoming
projectiles less than 50 m (160 ft) in diameter will
fragment and burn up in the atmosphere before reaching the ground.
The internal structure of
Venus – the crust (outer layer), the
mantle (middle layer) and the core (yellow inner layer)
Without seismic data or knowledge of its moment of inertia, little
direct information is available about the internal structure and
geochemistry of Venus. The similarity in size and density between
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. The slightly smaller size of
pressures are 24% lower in its deep interior than Earth's. 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. Instead,
Venus may lose its internal heat in
periodic major resurfacing events.
Atmosphere and climate
Cloud structure in the Venusian atmosphere in 1979, revealed by
observations in the ultraviolet band by Pioneer
Global radar view of
Venus (without the clouds) from Magellan between
1990 and 1994
Atmosphere of Venus
Venus has an extremely dense atmosphere composed of 96.5% carbon
dioxide, 3.5% nitrogen, and traces of other gases, most notably sulfur
dioxide. The mass of its atmosphere is 93 times that of Earth's,
whereas the pressure at its surface is about 92 times that at
Earth's—a pressure equivalent to that at a depth of nearly 1
kilometre (0.62 mi) under Earth's oceans. The density at the
surface is 65 kg/m3, 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 CO
2-rich atmosphere generates the strongest greenhouse effect in the
Solar System, creating surface temperatures of at least 735 K
(462 °C; 864 °F). This makes Venus's surface
hotter than Mercury's, which has a minimum surface temperature of
53 K (−220 °C; −364 °F) and maximum surface
temperature of 693 K (420 °C; 788 °F), even
Venus is nearly twice Mercury's distance from the
Sun and thus
receives only 25% of Mercury's solar irradiance. This temperature is
higher than that used for sterilization. The surface of
Venus is often
said to resemble traditional accounts of Hell.
Studies have suggested that billions of years ago Venus's 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, a runaway
greenhouse effect was caused by the evaporation of that original
water, which generated a critical level of greenhouse gases in its
atmosphere. Although the surface conditions on
Venus are no longer
hospitable to any Earthlike 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 (31 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
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 night and day sides, 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 if the heat, pressure, and lack of oxygen were not a
Above the dense CO
2 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 atmosphere
consists of approximately 1% ferric chloride. 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. 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
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. 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.
The surface of
Venus is effectively isothermal; it retains a constant
temperature not only between day and night sides but between the
equator and the poles. Venus's minute axial tilt—less than
3°, compared to 23° on Earth—also minimises seasonal temperature
variation. The only appreciable variation in temperature occurs
with altitude. 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). 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).
The clouds of
Venus may be capable of producing lightning. The
existence of lightning in the atmosphere of
Venus has been
controversial since the first suspected bursts were detected by the
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.
According to these measurements, the lightning rate is at least half
of that on Earth. In 2007,
Venus Express discovered that a huge
double atmospheric vortex exists at the south pole.
Venus Express also discovered, in 2011, that an ozone layer exists
high in the atmosphere of Venus. 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
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
Absorption spectrum of a simple gas mixture corresponding to Earth's
The composition of the atmosphere of
Venus based on
HITRAN on the Web system.
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
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, rather than by an
internal dynamo as in the Earth's core. Venus's small induced
magnetosphere provides negligible protection to the atmosphere against
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. 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 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
from the core is being used to reheat the crust.
One possibility is that
Venus has no solid inner core, 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
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 neutral 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 probably led to the loss of most of Venus'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 atmosphere 100 times compared to the rest of the solar system.
Orbit and rotation
Main article: Orbit of Venus
Venus orbits the
Sun at an average distance of about
108 million kilometres (about 0.7 AU) and completes an
orbit every 224.7 days.
Venus is the second planet from the Sun
and orbits 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 million km; 67 million mi), and completes an
orbit every 224.7 days. Although all planetary orbits are
elliptical, Venus's orbit is the closest to circular, with an
eccentricity of less than 0.01. When
Venus lies between
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). The planet reaches inferior conjunction
every 584 days, on average. 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; then
there are none for about 60,158 years.
All the planets in the
Solar System orbit the
Sun in a
counterclockwise direction as viewed from above Earth's north pole.
Most planets also rotate on their axes in an anti-clockwise direction,
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. A
Venusian sidereal day thus lasts longer than a Venusian year (243
Earth days). Venus's equator rotates at 6.52 km/h
(4.05 mph), whereas Earth's rotates at 1,669.8 km/h
(1,037.6 mph). Venus's rotation has slowed down in the
16 years between the Magellan spacecraft and
visits; each Venusian sidereal day has increased by 6.5 minutes
in that time span. 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. To an observer on
the surface of Venus, the
Sun would rise in the west and set in the
east, although Venus's opaque clouds prevent observing the Sun
from the planet's surface.
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
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.
The 584-day average interval between successive close approaches to
Earth is almost exactly equal to 5 Venusian solar days, but
the hypothesis of a spin–orbit resonance with
Earth has been
Venus has no natural satellites. It has several trojan asteroids:
the quasi-satellite 2002 VE68 and two other temporary
trojans, 2001 CK32 and 2012 XE133. In the 17th century,
Giovanni Cassini reported a moon orbiting Venus, which was named Neith
and numerous sightings were reported over the following
7009631152000000000♠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
Venus likely had at least one moon created by a huge
impact event billions of years ago. 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. 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.
Venus is always brighter than all other planets or stars as seen from
Earth. The second brightest object on the image is Jupiter.
To the naked eye,
Venus appears as a white point of light brighter
than any other planet or star (apart from the Sun). Its brightest
apparent magnitude, −4.9, occurs during crescent phase, only 36
days before or after inferior conjunction.
Venus was brightest on
30 April 2017, then grew dimmer for nearly a year.
Venus fades to
about magnitude −3 when it is backlit by the Sun. The planet is
bright enough to be seen in a clear midday sky and 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.
Earth every 584 days as it orbits the Sun. 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
Main article: Phases of Venus
The phases of
Venus and evolution of its apparent diameter
As it orbits the Sun,
Venus displays phases like those of the
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.
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.
Transit of Venus
Transit of Venus and Transit of Venus, 2012
2004 transit of Venus
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
Transits of Venus occur when the
planet's inferior conjunction coincides with its presence in the plane
of Earth's orbit.
Transits of Venus
Transits of Venus occur in cycles of
7009766849680000000♠243 years with the current pattern of
transits being pairs of transits separated by eight years, at
intervals of about 7009332932680000000♠105.5 years or
7009383424840000000♠121.5 years—a pattern first discovered in
1639 by the English astronomer Jeremiah Horrocks.
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.
The preceding pair of transits occurred in December 1874 and December
1882; the following pair will occur in December 2117 and December
2125. The oldest film known is the 1874 Passage de Venus, showing
Venus transit of the sun. 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. 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.
Pentagram of Venus
The pentagram of Venus.
Earth is positioned at the centre of the
diagram, and the curve represents the direction and distance of Venus
as a function of time.
The pentagram of
Venus is the path that
Venus makes as observed from
Earth. Successive inferior conjunctions of
Venus repeat very near a
13:8 orbital resonance (
Earth orbits 8 times for every 13 orbits of
Venus), shifting 144° upon sequential inferior conjunctions. The
resonance 13:8 ratio is approximate. 8/13 is approximately 0.615385
Venus orbits the
Sun in 0.615187 years.
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. 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. Although naked eye
visibility of Venus's phases is disputed, records exist of
observations of its crescent.
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.
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 assumption
that these were two separate objects. The ancient Sumerians, who
Venus as a single object, believed that it was their
goddess Inanna. Inanna's movements in several of her
Inanna and Shukaletuda and Inanna's Descent into the
Underworld appear to parallel the motion of the planet Venus. The
Venus tablet of Ammisaduqa, believed to have been compiled around the
mid-seventeenth century 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
The ancient Greeks thought that
Venus was two separate stars:
Phosphorus and Hesperus.
Pliny the Elder
Pliny the Elder credited the realization that
they were a single object to
Pythagoras in the sixth century BCE,
Diogenes Laertius argued that
Parmenides was probably
responsible. The ancient Chinese referred to the morning
"the Great White" (Tai-bai 太白) or "the Opener (Starter) of
Brightness" (Qi-ming 啟明), and the evening
Venus as "the Excellent
West One" (Chang-geng 長庚). The Romans designated the morning
Venus as Lucifer, literally "Light-Bringer", and the evening
aspect as Vesper, both literal translations of the respective Greek
In the second century, in his astronomical treatise Almagest, Ptolemy
theorized that both Mercury and
Venus are located between the
the Earth. The 11th century Persian astronomer
Avicenna claimed to
have observed the transit of Venus, which later astronomers took
as confirmation of Ptolemy's theory. In the 12th century, the
Ibn Bajjah observed "two planets as black spots
on the face of the Sun", which were later identified as the transits
Venus and Mercury by the Maragha astronomer
Qotb al-Din Shirazi
Qotb al-Din Shirazi in
the 13th century.[n 2]
Galileo's discovery that
Venus showed phases (although remaining near
Sun in Earth's sky) proved that it orbits the
Sun and not 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
centred on Earth.
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).
The atmosphere of
Venus was discovered in 1761 by Russian polymath
Mikhail Lomonosov. 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
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. The atmosphere complicated efforts to determine a
rotation period for the planet, and observers such as Italian-born
Giovanni Cassini and Schröter incorrectly estimated
periods of about 7004864000000000000♠24 h from the motions of
markings on the planet's apparent surface.
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 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.
Spectroscopic observations in the 1900s gave the first clues about the
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. 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.
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. These three features are now the only ones on
do not have female names.
Main article: Observations and explorations of Venus
Artist's impression of Mariner 2, launched in 1962, a skeletal,
bottle-shaped spacecraft with a large radio dish on top
The first robotic space probe mission to Venus, and the first to any
planet, began with the Soviet
Venera program in 1961. The United
States' exploration of
Venus had its first success with the Mariner 2
mission on 14 December 1962, becoming the world's first successful
interplanetary mission, passing 34,833 km (21,644 mi) above
the surface of Venus, and gathering data on the planet's
180-degree panorama of Venus's surface from the Soviet Venera 9
lander, 1975. Black-and-white image of barren, black, slate-like rocks
against a flat sky. The ground and the probe are the focus. Several
lines are missing due to a simultaneous transmission of the scientific
On 18 October 1967, the Soviet
Venera 4 successfully entered the
atmosphere and deployed science experiments.
Venera 4 showed the
surface temperature was hotter than
Mariner 2 had calculated, at
almost 500 °C, determined that the atmosphere is 95% carbon
2), and discovered that Venus's atmosphere was considerably denser
Venera 4's designers had anticipated. The joint Venera
Mariner 5 data were analysed by a combined Soviet–American
science team in a series of colloquia over the following year, in
an early example of space cooperation.
Mariner 10 swung by
Venus on its way to Mercury and took
ultraviolet photographs of the clouds, revealing the extraordinarily
high wind speeds in the Venusian atmosphere.
Global view of
Venus in ultraviolet light done by Mariner 10.
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
Venera 13 and 14 landers.
NASA obtained additional data in 1978 with the Pioneer
that consisted of two separate missions: Pioneer
Venus Multiprobe. 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)
Venus flybys took place in the 1980s and 1990s that
increased the understanding of Venus, including
Vega 1 (1985), Vega 2
Galileo (1990), Magellan (1994),
Cassini–Huygens (1998), and
MESSENGER (2006). Then,
Venus Express by the European Space Agency
(ESA) entered orbit around
Venus in April 2006. Equipped with seven
Venus Express provided unprecedented long-term
observation of Venus's atmosphere.
ESA concluded that mission in
As of 2016, Japan's Akatsuki is in a highly elliptical orbit around
Venus since 7 December 2015, and there are several probing proposals
under study by Roscosmos, NASA, and India's ISRO.
NASA announced that it was planning a rover, the Automaton
Rover for Extreme Environments, designed to survive for an extended
time in Venus's environmental conditions. It would be controlled by a
mechanical computer and driven by wind power.
Venus in fiction
Venus in fiction and Observations and explorations of Venus
§ Historical observations and impact
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. Classical poets such as Homer,
Virgil spoke of the star and its light. Romantic
poets such as William Blake, Robert Frost,
Alfred Lord Tennyson
Alfred Lord Tennyson and
William Wordsworth wrote odes to it. 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
Earth, the planet was frequently depicted as warmer, but still
habitable by humans. 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. As scientific
Venus advanced, so science fiction authors tried to keep
pace, particularly by conjecturing human attempts to terraform
The astronomical symbol for
Venus is the same as that used in biology
for the female sex: a circle with a small cross beneath. The
Venus symbol also represents femininity, and in Western alchemy stood
for the metal copper. 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.
Life on Venus
See also: Colonization of Venus
The speculation of the existence of life on
significantly since the early 1960s, when spacecraft began studying
Venus and it became clear that the conditions on
Venus are extreme
compared to those on Earth.
The fact that
Venus is located closer to the
Sun than Earth, raising
temperatures on the surface to nearly 735 K (462 °C;
863 °F), the atmospheric pressure is ninety times that of Earth,
and the extreme impact of the greenhouse effect, make water-based life
as we know it unlikely. A few scientists have speculated that
thermoacidophilic extremophile microorganisms might exist in the
lower-temperature, acidic upper layers of the Venusian
atmosphere. The atmospheric pressure and temperature
fifty kilometres above the surface are similar to those at Earth's
surface. This has led to proposals to use aerostats (lighter-than-air
balloons) for initial exploration and ultimately for permanent
"floating cities" in the Venusian atmosphere. Among the many
engineering challenges are the dangerous amounts of sulfuric acid at
Solar System portal
Book: Solar System
Aspects of Venus
Geodynamics of Venus
Outline of Venus
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The Solar System
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Solar System objects
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Spacecraft missions to Venus
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List of artificial objects on Venus
List of missions
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