The atmosphere of Venus is the layer of gases surrounding Venus. It is composed primarily of carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K (467 °C, 872 °F), and the pressure is 93 bar (9.3 MPa), roughly the pressure found 900 m (3,000 ft) underwater on Earth. The Venusian atmosphere supports opaque clouds made of sulfuric acid, making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging. Aside from carbon dioxide, the other main component is nitrogen. Other chemical compounds are present only in trace amounts.
Aside from the very surface layers, the atmosphere is in a state of vigorous circulation. The upper layer of troposphere exhibits a phenomenon of super-rotation, in which the atmosphere circles the planet in just four Earth days, much faster than the planet's sidereal day of 243 days. The winds supporting super-rotation blow at a speed of 100 m/s (≈360 km/h or 220 mph) or more. Winds move at up to 60 times the speed of the planet's rotation, while Earth's fastest winds are only 10% to 20% rotation speed. On the other hand, the wind speed becomes increasingly slower as the elevation from the surface decreases, with the breeze barely reaching the speed of 10 km/h (2.8 m/s) on the surface. Near the poles are anticyclonic structures called polar vortices. Each vortex is double-eyed and shows a characteristic S-shaped pattern of clouds. Above there is an intermediate layer of mesosphere which separates the troposphere from the thermosphere. The thermosphere is also characterized by strong circulation, but very different in its nature - the gases heated and partially ionized by sunlight in the sunlit hemisphere migrate to the dark hemisphere where they recombine and downwell.
Unlike Earth, Venus lacks a magnetic field. Its ionosphere separates the atmosphere from outer space and the solar wind. This ionised layer excludes the solar magnetic field, giving Venus a distinct magnetic environment. This is considered Venus's induced magnetosphere. Lighter gases, including water vapour, are continuously blown away by the solar wind through the induced magnetotail. It is speculated that the atmosphere of Venus up to around 4 billion years ago was more like that of the Earth with liquid water on the surface. A runaway greenhouse effect may have been caused by the evaporation of the surface water and subsequent rise of the levels of other greenhouse gases.
Despite the harsh conditions on the surface, the atmospheric pressure and temperature at about 50 km to 65 km above the surface of the planet is nearly the same as that of the Earth, making its upper atmosphere the most Earth-like area in the Solar System, even more so than the surface of Mars. Due to the similarity in pressure and temperature and the fact that breathable air (21% oxygen, 78% nitrogen) is a lifting gas on Venus in the same way that helium is a lifting gas on Earth, the upper atmosphere has been proposed as a location for both exploration and colonization.
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."
|Atmosphere of Venus|
Cloud structure in Venus's atmosphere in 1979,
revealed by ultraviolet observations from Pioneer Venus Orbiter
|Height||250 km (160 mi)|
|Average surface pressure||93 bar or 9.3 MPa|
|Mass||4.8 × 1020 kg|
|Carbon dioxide||96.5 %|
|Sulfur dioxide||150 ppm|
|Water vapor||20 ppm|
|Carbon monoxide||17 ppm|
|Hydrogen chloride||0.1–0.6 ppm|
|Hydrogen fluoride||0.001–0.005 ppm|
Mikhail Lomonosov was the first person to hypothesize the existence of an atmosphere on Venus based on his observation of the transit of Venus of 1761 in a small observatory near his house in Saint Petersburg, Russia.
The atmosphere of Venus is composed of 96.5% carbon dioxide, 3.5% nitrogen, and traces of other gases, most notably sulfur dioxide. The amount of nitrogen in the atmosphere is relatively small compared to the amount of carbon dioxide, but because the atmosphere is so much thicker than that on Earth, its total nitrogen content is roughly four times higher than Earth's, even though on Earth nitrogen makes up about 78% of the atmosphere.
The atmosphere contains a range of compounds in small quantities, including some based on hydrogen, such as hydrogen chloride (HCl) and hydrogen fluoride (HF). There is carbon monoxide, water vapour and atomic oxygen as well. Hydrogen is in relatively short supply in the Venusian atmosphere. A large amount of the planet's hydrogen is theorised to have been lost to space, with the remainder being mostly bound up in sulfuric acid (H2SO4) and hydrogen sulfide (H2S). The loss of significant amounts of hydrogen is proven by a very high D–H ratio measured in the Venusian atmosphere. The ratio is about 0.015–0.025, which is 100–150 times higher than the terrestrial value of 1.6×10−4. According to some measurements, in the upper atmosphere of Venus D/H ratio is 1.5 higher than in the bulk atmosphere.
The atmosphere is divided into a number of sections depending on altitude. The densest part of the atmosphere, the troposphere, begins at the surface and extends upwards to 65 km. At the furnace-like surface the winds are slow, but at the top of the troposphere the temperature and pressure reaches Earth-like levels and clouds pick up speed to 100 m/s (360 km/h).
The atmospheric pressure at the surface of Venus is about 92 times that of the Earth, similar to the pressure found 900 m (3,000 ft) below the surface of the ocean. The atmosphere has a mass of 4.8×1020 kg, about 93 times the mass of the Earth's total atmosphere. The density of the air at the surface is 67 kg/m3, which is 6.5% that of liquid water on Earth. The pressure found on Venus's surface is high enough that the carbon dioxide is technically no longer a gas, but a supercritical fluid. This supercritical carbon dioxide forms a kind of sea that covers the entire surface of Venus. This sea of supercritical carbon dioxide transfers heat very efficiently, buffering the temperature changes between night and day (which last 56 terrestrial days).
The large amount of CO2 in the atmosphere together with water vapour and sulfur dioxide create a strong greenhouse effect, trapping solar energy and raising the surface temperature to around 740 K (467 °C), hotter than any other planet in the Solar System, even that of Mercury despite being located farther out from the Sun and receiving only 25% of the solar energy (per unit area) Mercury does. The average temperature on the surface is above the melting points of lead (600 K, 327 °C), tin (505 K, 232 °C), and zinc (693 K, 420 °C). The thick troposphere also makes the difference in temperature between the day and night side small, even though the slow retrograde rotation of the planet causes a single solar day to last 116.5 Earth days. The surface of Venus spends 58.3 days in darkness before the sun rises again behind the clouds.
The troposphere on Venus contains 99% of the atmosphere by mass. Ninety percent of the atmosphere of Venus is within 28 km of the surface; by comparison, 90% of the atmosphere of Earth is within 10 km of the surface. At a height of 50 km the atmospheric pressure is approximately equal to that at the surface of Earth. On the night side of Venus clouds can still be found at 80 km above the surface.
The altitude of the troposphere most similar to Earth is near the tropopause—the boundary between troposphere and mesosphere. It is located slightly above 50 km. According to measurements by the Magellan and Venus Express probes, the altitude from 52.5 to 54 km has a temperature between 293 K (20 °C) and 310 K (37 °C), and the altitude at 49.5 km above the surface is where the pressure becomes the same as Earth at sea level. As manned ships sent to Venus would be able to compensate for differences in temperature to a certain extent, anywhere from about 50 to 54 km or so above the surface would be the easiest altitude in which to base an exploration or colony, where the temperature would be in the crucial "liquid water" range of 273 K (0 °C) to 323 K (50 °C) and the air pressure the same as habitable regions of Earth. As CO2 is heavier than air, the colony's air (nitrogen and oxygen) could keep the structure floating at that altitude like a dirigible.
The circulation in Venus's troposphere follows the so-called cyclostrophic flow. Its windspeeds are roughly determined by the balance of the pressure gradient and centrifugal forces in almost purely zonal flow. In contrast, the circulation in the Earth's atmosphere is governed by the geostrophic balance. Venus's windspeeds can be directly measured only in the upper troposphere (tropopause), between 60–70 km, altitude, which corresponds to the upper cloud deck. The cloud motion is usually observed in the ultraviolet part of the spectrum, where the contrast between clouds is the highest. The linear wind speeds at this level are about 100 ± 10 m/s at lower than 50° latitude. They are retrograde in the sense that they blow in the direction of the retrograde rotation of the planet. The winds quickly decrease towards the higher latitudes, eventually reaching zero at the poles. Such strong cloud-top winds cause a phenomenon known as the super-rotation of the atmosphere. In other words, these high-speed winds circle the whole planet faster than the planet itself rotates. The super-rotation on Venus is differential, which means that the equatorial troposphere super-rotates more slowly than the troposphere at the midlatitudes. The winds also have a strong vertical gradient. They decline deep in the troposphere with the rate of 3 m/s per km. The winds near the surface of Venus are much slower than that on Earth. They actually move at only a few kilometres per hour (generally less than 2 m/s and with an average of 0.3 to 1.0 m/s), but due to the high density of the atmosphere at the surface, this is still enough to transport dust and small stones across the surface, much like a slow-moving current of water.
All winds on Venus are ultimately driven by convection. Hot air rises in the equatorial zone, where solar heating is concentrated, and flows to the poles. Such an almost-planetwide overturning of the troposphere is called Hadley circulation. However, the meridional air motions are much slower than zonal winds. The poleward limit of the planet wide Hadley cell on Venus is near ±60° latitudes. Here air starts to descend and returns to the equator below the clouds. This interpretation is supported by the distribution of the carbon monoxide, which is also concentrated in the vicinity of ±60° latitudes. Poleward of the Hadley cell a different pattern of circulation is observed. In the latitude range 60°–70° cold polar collars exist. They are characterised by temperatures about 30–40 K lower than in the upper troposphere at nearby latitudes. The lower temperature is probably caused by the upwelling of the air in them and by the resulting adiabatic cooling. Such an interpretation is supported by the denser and higher clouds in the collars. The clouds lie at 70–72 km altitude in the collars—about 5 km higher than at the poles and low latitudes. A connection may exist between the cold collars and high speed midlatitude jets in which winds blow as fast as 140 m/s. Such jets are a natural consequence of the Hadley–type circulation and should exist on Venus between 55–60° latitude.
Odd structures known as polar vortices lie within the cold polar collars. They are giant hurricane-like storms four times larger than their terrestrial analogs. Each vortex has two "eyes"—the centres of rotation, which are connected by distinct S-shaped cloud structures. Such double eyed structures are also called polar dipoles. Vortices rotate with the period of about 3 days in the direction of general super-rotation of the atmosphere. The linear wind speeds are 35–50 m/s near their outer edges and zero at the poles. The temperature at the cloud-tops in the each polar vortex is much higher than in the nearby polar collars reaching 250 K (−23 °C). The conventional interpretation of the polar vortices is that they are anticyclones with downwelling in the centre and upwelling in the cold polar collars. This type of circulation resembles a winter polar anticyclonic vortex on Earth, especially the one found over Antarctica. The observations in the various infrared atmospheric windows indicate that the anticyclonic circulation observed near the poles penetrates as deep as to 50 km altitude, i.e. to the base of the clouds. The polar upper troposphere and mesosphere are extremely dynamic; large bright clouds may appear and disappear over the space of a few hours. One such event was observed by Venus Express between 9 and 13 January 2007, when the south polar region became brighter by 30%. This event was probably caused by an injection of sulfur dioxide into the mesosphere, which then condensed forming a bright haze. The two eyes in the vortices have yet to be explained.
The first vortex on Venus was discovered at the north pole by the Pioneer Venus mission in 1978. A discovery of the second large 'double-eyed' vortex at the south pole of Venus was made in the summer of 2006 by Venus Express, which came with no surprise.
Images from the Akatsuki orbiter revealed something similar to jet stream winds in the low and middle cloud region, which extends from 45 to 60 kilometers in altitude. The wind speed maximized near the equator. In September 2017 JAXA scientists named this phenomenon 'Venusian equatorial jet'.
The mesosphere of Venus extends from 65 km to 120 km in height, and the thermosphere begins at approximately 120 km, eventually reaching the upper limit of the atmosphere (exosphere) at about 220 to 350 km. The exosphere is the altitude at which the atmosphere becomes collisionless.
The mesosphere of Venus can be divided into two layers: the lower one between 62–73 km and the upper one between 73–95 km. In the first layer the temperature is nearly constant at 230 K (−43 °C). This layer coincides with the upper cloud deck. In the second layer temperature starts to decrease again reaching about 165 K (−108 °C) at the altitude of 95 km, where mesopause begins. It is the coldest part of the Venusian dayside atmosphere. In the dayside mesopause, which serves as a boundary between the mesophere and thermosphere and is located between 95–120 km, temperature increases to a constant—about 300–400 K (27–127 °C)—value prevalent in the thermosphere. In contrast, the nightside Venusian thermosphere is the coldest place on Venus with temperature as low as 100 K (−173 °C). It is even called a cryosphere.
The circulation patterns in the upper mesosphere and thermosphere of Venus are completely different from those in the lower atmosphere. At altitudes 90–150 km the Venusian air moves from the dayside to nightside of the planet, with upwelling over sunlit hemisphere and downwelling over dark hemisphere. The downwelling over the nightside causes adiabatic heating of the air, which forms a warm layer in the nightside mesosphere at the altitudes 90–120 km. The temperature of this layer—230 K (−43 °C) is far higher than the typical temperature found in the nightside thermosphere—100 K (−173 °C). The air circulated from the dayside also carries oxygen atoms, which after recombination form excited molecules of oxygen in the long-lived singlet state (1Δg), which then relax and emit infrared radiation at the wavelength 1.27 μm. This radiation from the altitude range 90–100 km is often observed from the ground and spacecraft. The nightside upper mesosphere and thermosphere of Venus is also the source of non-local thermodynamic equilibrium emissions of CO2 and nitric oxide molecules, which are responsible for the low temperature of the nightside thermosphere.
The Venus Express probe has shown through stellar occultation that the atmospheric haze extends much further up on the night side than the day side. On the day side the cloud deck has a thickness of 20 km and extends up to about 65 km, whereas on the night side the cloud deck in the form of a thick haze reaches up to 90 km in altitude—well into mesosphere, continuing even further to 105 km as a more transparent haze. In 2011, the spacecraft discovered that Venus has a thin ozone layer at an altitude of 100 km.
Venus has an extended ionosphere located at altitudes 120–300 km. The ionosphere almost coincides with the thermosphere. The high levels of the ionization are maintained only over the dayside of the planet. Over the nightside the concentration of the electrons is almost zero. The ionosphere of Venus consists of three layers: v1 between 120 and 130 km, v2 between 140 and 160 km and v3 between 200 and 250 km. There may be an additional layer near 180 km. The maximum electron volume density (number of electrons in a unit of volume) 3×1011 m−3 is reached in the v2 layer near the subsolar point. The upper boundary of the ionosphere—ionopause is located at altitudes 220–375 km and separates the plasma of the planetary origin from that of the induced magnetosphere. The main ionic species in the v1 and v2 layers is O2+ ion, whereas the v3 layer consists of O+ ions. The ionospheric plasma is observed to be in motion; solar photoionization on the dayside, and ion recombination on the nightside, are the processes mainly responsible for accelerating the plasma to the observed velocities. The plasma flow appears to be sufficient to maintain the nightside ionosphere at or near the observed median level of ion densities.
Venus is known not to have a magnetic field. The reason for its absence is not at all clear, but it may be related to a reduced intensity of convection in the Venusian mantle. Venus only has an induced magnetosphere formed by the Sun's magnetic field carried by the solar wind. This process can be understood as the field lines wrapping around an obstacle—Venus in this case. The induced magnetosphere of Venus has a bow shock, magnetosheath, magnetopause and magnetotail with the current sheet.
At the subsolar point the bow shock stands 1900 km (0.3 Rv, where Rv is the radius of Venus) above the surface of Venus. This distance was measured in 2007 near the solar activity minimum. Near the solar activity maximum it can be several times further from the planet. The magnetopause is located at the altitude of 300 km. The upper boundary of the ionosphere (ionopause) is near 250 km. Between the magnetopause and ionopause there exists a magnetic barrier—a local enhancement of the magnetic field, which prevents solar plasma from penetrating deeper into the Venusian atmosphere, at least near solar activity minimum. The magnetic field in the barrier reaches up to 40 nT. The magnetotail continues up to ten radii from the planet. It is the most active part of the Venusian magnetosphere. There are reconnection events and particle acceleration in the tail. The energies of electrons and ions in the magnetotail are around 100 eV and 1000 eV respectively.
Due to the lack of the intrinsic magnetic field on Venus, the solar wind penetrates relatively deep into the planetary exosphere and causes substantial atmosphere loss. The loss happens mainly via the magnetotail. Currently the main ion types being lost are O+, H+ and He+. The ratio of hydrogen to oxygen losses is around 2 (i.e. almost stoichiometric) indicating the ongoing loss of water.
Venusian clouds are thick and are composed mainly (75-96%) of sulfuric acid droplets. These clouds obscure the surface of Venus from optical imaging, and reflect about 75% of the sunlight that falls on them. The geometric albedo, a common measure of reflectivity, is the highest of any planet in the Solar System. This high reflectivity potentially enables any probe exploring the cloud tops sufficient solar energy such that solar cells can be fitted anywhere on the craft. The density of the clouds is highly variable with the densest layer at about 48.5 km, reaching 0.1 g/m3 similar to the lower range of cumulonimbus storm clouds on Earth.
The cloud cover is such that typical surface light levels are similar to a partly cloudy day on Earth, around 5000–10000 lux. The equivalent visibility is about three kilometers, but this will likely vary with the wind conditions. Little to no solar energy could conceivably be collected by solar panels on a surface probe. In fact, due to the thick, highly reflective cloud cover, the total solar energy received by the surface of the planet is less than that of the Earth.
Sulfuric acid is produced in the upper atmosphere by the Sun's photochemical action on carbon dioxide, sulfur dioxide, and water vapour. Ultraviolet photons of wavelengths less than 169 nm can photodissociate carbon dioxide into carbon monoxide and atomic oxygen. Atomic oxygen is highly reactive; when it reacts with sulfur dioxide, a trace component of the Venusian atmosphere, the result is sulfur trioxide, which can combine with water vapour, another trace component of Venus's atmosphere, to yield sulfuric acid.
Surface level humidity is less than 0.1%. Venus's sulfuric acid rain never reaches the ground, but is evaporated by the heat before reaching the surface in a phenomenon known as virga. It is theorized that early volcanic activity released sulfur into the atmosphere and the high temperatures prevented it from being trapped into solid compounds on the surface as it was on the Earth.
In 2009 a prominent bright spot in the atmosphere was noted by an amateur astronomer and photographed by Venus Express. Its cause is currently unknown, with surface volcanism advanced as a possible explanation.
The clouds of Venus may be capable of producing lightning, and the Soviet Venera 9 and 10 orbiters obtained optical and electromagnetic evidence of lightning. The European Space Agency's Venus Express in 2007 detected whistler waves which were attributed to lightning. Their intermittent appearance indicates a pattern associated with weather activity. According to the whistler observations, the lightning rate is at least half of that on Earth.
The mechanism generating lightning on Venus remains unknown. Whilst the sulfuric acid cloud droplets can become charged, the atmosphere may be too electrically conductive for the charge to be sustained, preventing lightning. The debate on Venus lightning is ongoing, with volcanic lightning and sprites also under discussion.
Due to the harsh conditions on the surface, little of the planet has been explored; in addition to the fact that life as currently understood may not necessarily be the same in other parts of the universe, the extent of the tenacity of life on Earth itself has not yet been shown. Creatures known as extremophiles exist on Earth, preferring extreme habitats. Thermophiles and hyperthermophiles thrive at temperatures reaching above the boiling point of water, acidophiles thrive at a pH level of 3 or below, polyextremophiles can survive a varied number of extreme conditions, and many other types of extremophiles exist on Earth.
The surface temperature of Venus (over 450 °C) is far beyond the extremophile range, which extends only tens of degrees beyond 100 °C. However, the lower temperature of the cloud tops means that life could plausibly exist. It has been proposed that life on Venus could exist there, the same way that bacteria have been found living and reproducing in clouds on Earth. Any such bacteria living in the cloud tops, however, would have to be hyper-acidiphilic, due to the concentrated sulfuric acid environment. Microbes in the thick, cloudy atmosphere could be protected from solar radiation by the sulfur compounds in the air. The solar wind may provide a mechanism for the transfer of such microbiota from Venus to Earth.
The Venusian atmosphere has been found to be sufficiently out of equilibrium as to require further investigation. Analysis of data from the Venera, Pioneer, and Magellan missions has found the chemicals hydrogen sulfide (H2S) and sulfur dioxide (SO2) together in the upper atmosphere, as well as carbonyl sulfide (OCS). The first two gases react with each other, implying that something must produce them. Carbonyl sulfide is difficult to produce inorganically, but it is present in the Venusian atmosphere. However, the planet's volcanism could explain the presence of carbonyl sulfide. In addition, one of the early Venera probes detected large amounts of toxic chlorine just below the Venusian cloud deck.
It has been proposed that microbes at this level could be soaking up ultraviolet light from the Sun as a source of energy, which could be a possible explanation for dark patches seen on UV images of the planet. Large, non-spherical cloud particles have also been detected in the cloud decks. In 2012, the abundance and vertical distribution of these unknown ultraviolet absorbers in the Venusian atmosphere have been investigated from analysis of Venus Monitoring Camera images, but their composition is still unknown. In 2016, disulfur dioxide was identified as a possible candidate for causing the so far unknown UV absorption of the Venusian atmosphere.
Through studies of the present cloud structure and geology of the surface, combined with the fact that the luminosity of the Sun has increased by 25% since around 3.8 billion years ago, it is thought that the early environment of Venus was more like that of Earth with liquid water on the surface. At some point in the evolution of Venus, a runaway greenhouse effect occurred, leading to the current greenhouse-dominated atmosphere. The timing of this transition from Earthlike to Venuslike is not known, but is estimated to have occurred around 4 billion years ago. The runaway greenhouse effect may have been caused by the evaporation of the surface water and the rise of the levels of greenhouse gases that followed. Venus's atmosphere has therefore received a great deal of attention from those studying climate change on Earth.
There are no geologic forms on the planet to suggest the presence of water over the past billion years. However, there is no reason to suppose that Venus was an exception to the processes that formed Earth and gave it its water during its early history, possibly from the original rocks that formed the planet or later on from comets. The common view among research scientists is that water would have existed for about 600 million years on the surface before evaporating, though some such as David Grinspoon believe that up to 2 billion years could also be plausible.
The early Earth during the Hadean eon is believed by most scientists to have had a Venus-like atmosphere, with roughly 100 bar of CO2 and a surface temperature of 230 °C, and possibly even sulfuric acid clouds, until about 4.0 billion years ago, by which time plate tectonics were in full force and together with the early water oceans, removed the CO2 and sulfur from the atmosphere. Early Venus would thus most likely have had water oceans like the Earth, but any plate tectonics would have ended when Venus lost its oceans. Its surface is estimated to be about 500 million years old, so it would not be expected to show evidence of plate tectonics.
In 1761, Russian polymath Mikhail Lomonosov observed an arc of light surrounding the part of Venus off the Sun's disc at the beginning of the egress phase of the transit and concluded that Venus has an atmosphere. In 1940, Rupert Wildt calculated that the amount of CO2 in the Venusian atmosphere would raise surface temperature above the boiling point for water. This was confirmed when Mariner 2 made radiometer measurements of the temperature in 1962. In 1967, Venera 4 confirmed that the atmosphere consisted primarily of carbon dioxide.
The upper atmosphere of Venus can be measured from Earth when the planet crosses the sun in a rare event known as a solar transit. The last solar transit of Venus occurred in 2012. Using quantitative astronomical spectroscopy, scientists were able to analyse sunlight that passed through the planet's atmosphere to reveal chemicals within it. As the technique to analyse light to discover information about a planet's atmosphere only first showed results in 2001, this was the first opportunity to gain conclusive results in this way on the atmosphere of Venus since observation of solar transits began. This solar transit was a rare opportunity considering the lack of information on the atmosphere between 65 and 85 km. The solar transit in 2004 enabled astronomers to gather a large amount of data useful not only in determining the composition of the upper atmosphere of Venus, but also in refining techniques used in searching for extrasolar planets. The atmosphere of mostly CO2, absorbs near-infrared radiation, making it easy to observe. During the 2004 transit, the absorption in the atmosphere as a function of wavelength revealed the properties of the gases at that altitude. The Doppler shift of the gases also enabled wind patterns to be measured.
A solar transit of Venus is an extremely rare event, and the last solar transit of the planet before 2004 was in 1882. The most recent solar transit was in 2012; the next one will not occur until 2117.
The JAXA probe Akatsuki (Venus Climate Orbiter), launched in May 2010, is studying the planet for a period of two years, including the structure and activity of the atmosphere, but it failed to enter Venus orbit in December 2010. A second attempt to achieve orbit succeeded 7 December 2015. Designed specifically to study the planet's climate, Akatsuki is the first meteorology satellite to orbit Venus (the first for a planet other than Earth). One of its five cameras known as the "IR2" will be able to probe the atmosphere of the planet underneath its thick clouds, in addition to its movement and distribution of trace components. With a highly eccentric orbit (periapsis altitude of 400 km and apoapsis of 310,000 km), it will be able to take close-up photographs of the planet, and should also confirm the presence of both active volcanoes as well as lightning.
The Venus In-Situ Explorer, proposed by NASA's New Frontiers program is a proposed probe which would aid in understanding the processes on the planet that led to climate change, as well as paving the way towards a later sample return mission.
A craft called the Venus Mobile Explorer has been proposed by the Venus Exploration Analysis Group (VEXAG) to study the composition and isotopic measurements of the surface and the atmosphere, for about 90 days. The mission has not been selected for launch.
After missions discovered the reality of the harsh nature of the planet's surface, attention shifted towards other targets such as Mars. There have been a number of proposed missions afterwards however, and many of these involve the little-known upper atmosphere. The Soviet Vega program in 1985 dropped two balloons into the atmosphere, but these were battery-powered and lasted for only about two Earth days each before running out of power. Since then, there has been no exploration of the upper atmosphere. In 2002, the NASA contractor Global Aerospace proposed a balloon that would be capable of staying in the upper atmosphere for hundreds of Earth days as opposed to two.
A solar flyer has also been proposed by Geoffrey A. Landis in place of a balloon, and the idea has been featured from time to time since the early 2000s. Venus has a high albedo, and reflects most of the sunlight that shines on it making the surface quite dark, the upper atmosphere at 60 km has an upward solar intensity of 90%, meaning that solar panels on both the top and the bottom of a craft could be used with nearly equal efficiency. In addition to this, the slightly lower gravity, high air pressure and slow rotation allowing for perpetual solar power make this part of the planet ideal for exploration. The proposed flyer would operate best at an altitude where sunlight, air pressure, and wind speed would enable it to remain in the air perpetually, with slight dips down to lower altitudes for a few hours at a time before returning to higher altitudes. As sulfuric acid in the clouds at this height is not a threat for a properly shielded craft, this so-called "solar flyer" would be able to measure the area in between 45 km and 60 km indefinitely, for however long it takes for mechanical error or unforeseen problems to cause it to fail. Landis also proposed that rovers similar to Spirit and Opportunity could possibly explore the surface, with the difference being that Venus surface rovers would be "dumb" rovers controlled by radio signals from computers located in the flyer above, only requiring parts such as motors and transistors to withstand the surface conditions, but not weaker parts involved in microelectronics that could not be made resistant to the heat, pressure and acidic conditions.
Russian space plan for 2006–2015 involves a launch of Venera-D (Venus-D) probe around 2024. The main scientific goals of the Venera-D mission are investigation of the structure and chemical composition of the atmosphere and investigation of the upper atmosphere, ionosphere, electrical activity, magnetosphere and escape rate. It has been proposed to fly together with Venera-D an inflatable aircraft designed by Northrop Grumman, called Venus Atmospheric Maneuverable Platform (VAMP).
The High Altitude Venus Operational Concept (HAVOC) is a NASA concept for a manned exploration of Venus. Rather than traditional landings, it would send crews into the upper atmosphere, using dirigibles. Other proposals from the late 2010s include VERITAS, Venus Origins Explorer, VISAGE, and VICI. In June 2018, NASA also awarded a contract to Black Swift Technologies for a concept study of a Venus glider that would exploit wind shear for lift and speed.
Media related to Atmosphere of Venus at Wikimedia Commons2012 transit of Venus
The 2012 transit of Venus, when the planet Venus appeared as a small, dark spot passing across the face of the Sun, began at 22:09 UTC on 5 June 2012, and finished at 04:49 UTC on 6 June. Depending on the position of the observer, the exact times varied by up to ±7 minutes. Transits of Venus are among the rarest of predictable celestial phenomena and occur in pairs. Consecutive transits per pair are spaced 8 years apart, and consecutive pairs occur more than a century apart: The previous transit of Venus took place on 8 June 2004 (preceded by transits on 9 December 1874 and 6 December 1882); the next pair of transits will occur on 10–11 December 2117 and in December 2125.Adivar (crater)
Adivar is an impact crater on Venus, named in honor of Turkish writer and pilot Halide Edip Adıvar. The crater is located just north of the western Aphrodite highland (9 degrees north latitude, 76 degrees east longitude). Surrounding the crater rim is ejected material which appears bright in the radar image due to the presence of rough fractured rock. A much broader area has also been affected by the impact, particularly to the west of the crater. Radar-bright materials, including a jet-like streak just west of the crater, extend for over 500 kilometers (310 mi) across the surrounding plains. A darker streak, in a horseshoe or paraboloidal shape, surrounds the bright area. Radar-dark (i.e., smooth) paraboloidal streaks were observed around craters in earlier Magellan images, but this is a rare bright crater streak. These unusual streaks, seen only on Venus, are believed to result from the interaction of crater materials (the meteoroid, ejecta, or both) and high-speed winds in the upper atmosphere. The precise mechanism that produces the streaks is poorly understood, but it is clear that the dense atmosphere of Venus plays an important role in the distribution of the ejected material.Akatsuki (spacecraft)
Akatsuki (あかつき, 暁, "Dawn"), also known as the Venus Climate Orbiter (VCO) and Planet-C, is a Japanese (JAXA) space probe tasked to study the atmosphere of Venus. It was launched aboard an H-IIA 202 rocket on 20 May 2010, and failed to enter orbit around Venus on 6 December 2010. After the craft orbited the Sun for five years, engineers successfully placed it into an alternative elliptical Venusian orbit on 7 December 2015 by firing its attitude control thrusters for 20 minutes.By using five different cameras working at several wavelengths, Akatsuki is studying the stratification of the atmosphere, atmospheric dynamics, and cloud physics. Astronomers working on the mission reported detecting a possible gravity wave that occurred on Venus in December 2015.Gliese 1132 b
Gliese 1132 b (often shortened to GJ 1132 b) is an exoplanet orbiting a red dwarf star (Gliese 1132) 39 light years (12 parsecs) from Earth, in the constellation Vela. The planet is considered uninhabitable but cool enough to possess an atmosphere. Gliese 1132 b was discovered by the MEarth-South array in Chile.It has been called "one of the most important planets ever discovered beyond the Solar System": Due to its relative proximity to Earth, telescopes should be able to determine the composition of its atmosphere, the speed of its winds and the color of its sunsets. This is due in part to the small diameter of its parent star (21% that of the Sun), which increases the effect on the star's light of its transits. The planet's diameter is approximately 20% larger than that of the Earth and its mass is estimated at 1.6 times that of Earth, implying that it has an Earth-like rocky composition. Gliese 1132 b orbits its star every 1.6 days at a distance of 1.4 million miles.The planet receives 19 times more stellar radiation than Earth. The temperature of the top of its atmosphere is estimated at 500 °F (260 °C; 533 K). The planet is estimated to be hotter than Venus, as higher temperatures may prevail near the surface. (cf. Atmosphere of Venus, Colonization of Venus) It is possible that one side of the planet is cooler, because it is presumed to be tidally locked due to its proximity to its star; however, under most circumstances where an atmosphere is thick, it would be able to transfer heat to the far side.
In April 2017, a hydrogen-dominated atmosphere was claimed to have been detected around Gliese 1132 b. However, subsequent, more precise work ruled out the previous claim.John D. Strong
John Donovan Strong was a professor of Physics and Astronomy from 1967 to 1975 and served as the head of the laboratory of astrophysics and physical meteorology. Strong, one of the world’s foremost optical scientists, was known for being the first to detect water vapor in the atmosphere of Venus and for developing a number of innovations in optical devices, ranging from improved telescope mirrors to anti-reflective coatings for optical elements and diffraction gratings. Born in Lawrence, Kansas in 1905, Strong received degrees from the University of Kansas (BA 1926) and the University of Michigan (M.S., 1928, Ph.D., 1930). After twelve years at Caltech and wartime research at Harvard on infrared systems, Strong became professor and director of the Astrophysics and Physical Meteorology Laboratories at Johns Hopkins University in 1946, where, among many other projects, he conducted research on balloon astronomy for the Office of Naval Research (ONR). Strong published hundreds of papers throughout his career and was author of Procedures in Experimental Physics, a standard physics textbook for many years. Strong served as president of the American Optical Association in 1959 and patented numerous inventions for optics in spectroscopy as well as golf (see US Patent no. 3720467). Strong died in 1992.Life on Venus
The speculation of life currently existing on Venus decreased 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.
Venus's location closer to the Sun than Earth and the extreme greenhouse effect raising temperatures on the surface to nearly 735 K (462 °C), and the atmospheric pressure 90 times that of Earth, make water-based life as we know it unlikely on the surface of the planet. However, a few scientists have speculated that thermoacidophilic extremophile microorganisms might exist in the lower-temperature, acidic upper layers of the Venusian atmosphere.Observations and explorations of Venus
Observations of the planet Venus include those in antiquity, telescopic observations, and from visiting spacecraft. Spacecraft have performed various flybys, orbits, and landings on Venus, including balloon probes that floated in the atmosphere of Venus. Study of the planet is aided by its relatively close proximity to the Earth, compared to other planets, but the surface of Venus is obscured by an atmosphere opaque to visible light.Pioneer Venus Multiprobe
The Pioneer Venus Multiprobe, also known as Pioneer Venus 2 or Pioneer 13 was a spacecraft launched in 1978 to explore Venus as part of NASA's Pioneer program. This part of the mission included a spacecraft Bus which was launched from Earth carrying one large and three smaller probes, which after separating penetrated the Venusian atmosphere at a different location, returning data as they descended into the planet's thick atmosphere. The entry occurred on December 9, 1978.Pioneer Venus Orbiter
The Pioneer Venus Orbiter, also known as Pioneer Venus 1 or Pioneer 12, was a mission to Venus conducted by the United States as part of the Pioneer Venus project. Launched in May 1978 atop an Atlas-Centaur rocket, the spacecraft was inserted into an elliptical orbit around Venus on December 4, 1978. It returned data on Venus until October 1992.Research balloon
Research balloons are balloons that are used for scientific research. They are usually unmanned, filled with a lighter-than-air gas like helium, and fly at high altitudes.
Meteorology, atmospheric research, astronomy, and military research may be conducted from a research balloon.
Weather balloons are a type of research balloon. Research balloons usually study a single aspect of science, such as air pollution, air temperature, or wind currents, although sometimes several experiments or equipment are flown together.
Other than weather balloons, few research balloons are launched every year. This is driven by the large cost of the balloon, the instrument, which is usually custom made, and the cost of the launch. Because of the altitude reached by most research balloons, the air is too thin and too cold for humans to survive, therefore most research balloons are unmanned and operated remotely. There have been some balloons equipped with pressurized cabins, beginning with professor Auguste Piccard in the 1930s.
Research balloons are not only used on earth. With the help of a research balloon, the upper atmosphere of Venus was examined by the Vega program.Runaway greenhouse effect
A runaway greenhouse effect is a state in which a net positive feedback between surface temperature and atmospheric opacity increases the strength of the greenhouse effect on a planet until its oceans boil away.An example of this is believed to have happened in the early history of Venus. On the Earth the IPCC states that "a 'runaway greenhouse effect'—analogous to [that of] Venus—appears to have virtually no chance of being induced by anthropogenic activities."Other large-scale climate changes are sometimes loosely called a "runaway greenhouse effect" although it is not an appropriate description. For example, it has been hypothesized that large releases of greenhouse gases may have occurred concurrently with the Permian–Triassic extinction event or Paleocene–Eocene Thermal Maximum. Other terms, such as "abrupt climate change", or tipping points could be used when describing such scenarios, as well as the term hothouse state.A hypothetical runaway greenhouse effect on the earth should not be confused with a greenhouse earth, which has happened in several well-known periods. During 80% of the latest 500 million years, the earth is believed to have been in a greenhouse state due to the greenhouse effect, when there were no continental glaciers on the planet, the levels of carbon dioxide and other greenhouse gases (such as water vapor and methane) were high, and sea surface temperatures (SSTs) ranged from 28 °C (82.4 °F) in the tropics to 0 °C (32 °F) in the polar regions.Rupert Wildt
Rupert Wildt (; June 25, 1905 – January 9, 1976) was a German-American astronomer.He was born in Munich, Germany, and grew up in that country during World War I and its aftermath. In 1927 he was awarded a Ph.D. from the University of Berlin. He joined the University of Göttingen, specializing in the properties of atmospheres.
In 1932 he studied the spectra of Jupiter, and other outer planets, and identified certain absorption bands as belonging to the hydrogen-rich compounds of methane and ammonia. The composition appeared consistent with a composition similar to the sun and other stars.
Assuming that the atmosphere was composed of these gases, during the 1940s and 1950s he constructed a model of the structure of these planets. He believed the core of the planets is solid and composed of a mixture of rock and metal, covered by a thick outer shell of ice, overlaid by a dense atmosphere. His model is still widely accepted.
In 1934 he emigrated to the United States, and became a research assistant at Princeton University from 1937 until 1942. He then became an assistant professor at the University of Virginia until 1947, before joining the faculty of the Yale University.
In 1937 he proposed that the atmosphere of Venus was composed of a mist of formaldehyde. His observations of the atmosphere did not find any water at the time, but later balloon-based measurements did show water in the atmosphere and so his proposal was abandoned. In 1940, however, he also hypothesized that the carbon dioxide in the Venusian atmosphere trapped heat, a phenomenon later called the greenhouse effect.
In 1939 he demonstrated that the major source of optical opacity in the Sun's atmosphere is the H− ion, and thus the main source of visible light for the Sun and stars.
From 1965 until 1968 he was president of the Association of Universities for Research in Astronomy. In the period 1966-1968 he also held the post of the chairman of the department of astronomy at Yale, and from 1973 until his death he was professor emeritus. He died in Orleans, Massachusetts.Shukrayaan-1
Shukrayaan-1 (शुक्रयान-१ or Venus craft) is a proposed orbiter to Venus by the Indian Space Research Organisation (ISRO) to study the surface and atmosphere of Venus.Funds were released in 2017 to complete preliminary studies, and solicitations for instruments have been announced. If fully funded, it would be launched some time after the Mars Orbiter Mission 2 in the early 2020s. The orbiter, depending on its final configuration, would have a science payload capability of approximately 100 kg with 500 W available power. The initial elliptical orbit around Venus is expected to have 500 km at periapsis and 60,000 km at apoapsis.Venera
The Venera (Russian: Вене́ра, pronounced [vʲɪˈnʲɛrə]) are a series of space probes developed by the Soviet Union between 1961 and 1984 to gather data from Venus. The name Venera comes from the Russian name for Venus.
Ten probes from the Venera series successfully landed on Venus and transmitted data from the surface of Venus, including the two Vega program and Venera-Halley probes. In addition, thirteen Venera probes successfully transmitted data from the atmosphere of Venus.
Among other results, probes of the series became the first human-made devices to enter the atmosphere of another planet (Venera 4 on October 18, 1967), to make a soft landing on another planet (Venera 7 on December 15, 1970), to return images from the planetary surface (Venera 9 on June 8, 1975), and to perform high-resolution radar mapping studies of Venus (Venera 15 on June 2, 1983).
The latter probes in the Venera series successfully carried out their mission, providing the first direct observations of the surface of Venus. Since the surface conditions on Venus are extreme, the probes only survived on the surface for durations varying between 23 minutes (initial probes) up to about 2 hours (final probes).Venera 5
Venera 5 (Russian: Венера-5 meaning Venus 5) was a space probe in the Soviet space program Venera for the exploration of Venus.
Venera 5 was launched towards Venus to obtain atmospheric data. The spacecraft was very similar to Venera 4 although it was of a stronger design. The launch was conducted using a Molniya-M rocket, flying from the Baikonur Cosmodrome.
When the atmosphere of Venus was approached, a capsule weighing 405 kg (893 lb) and containing scientific instruments was jettisoned from the main spacecraft. During satellite descent towards the surface of Venus, a parachute opened to slow the rate of descent. For 53 minutes on May 16, 1969, while the capsule was suspended from the parachute, data from the Venusian atmosphere were returned. It landed at 3°S 18°E. The spacecraft also carried a medallion bearing the State Coat of Arms of the Soviet Union and a bas-relief of Lenin to the night side of Venus.
Given the results from Venera 4, the Venera 5 and Venera 6 landers contained new chemical analysis experiments tuned to provide more precise measurements of the atmosphere's components. Knowing the atmosphere was extremely dense, the parachutes were also made smaller so the capsule would reach its full crush depth before running out of power (as Venera 4 had done).Venera 6
Venera 6 (Russian: Венера-6 meaning Venus 6), or 2V (V-69) No.331, was a Soviet spacecraft, launched towards Venus to obtain atmospheric data. It had an on-orbit dry mass of 1,130 kg (2,490 lb).
The spacecraft was very similar to Venera 4 although it was of a stronger design. When the atmosphere of Venus was approached, a capsule with a mass of 405 kilograms (893 lb) was jettisoned from the main spacecraft. This capsule contained scientific instruments.
During descent towards the surface of Venus, a parachute opened to slow the rate of descent. For 51 minutes on May 17, 1969, while the capsule was suspended from the parachute, data from the Venusian atmosphere were returned. It landed at 5°S 23°E.
The spacecraft also carried a medallion bearing the State Coat of Arms of the Soviet Union and a bas-relief of Lenin to the night side of Venus.
Given the results from Venera 4, the Venera 5 and Venera 6 landers contained new chemical analysis experiments tuned to provide more precise measurements of the atmosphere's components. Knowing the atmosphere was extremely dense, the parachutes were also made smaller so the capsule would reach its full crush depth before running out of power (as Venera-4 had done).Venera 7
Venera 7 (Russian: Венера-7, meaning Venus 7) was a Soviet spacecraft, part of the Venera series of probes to Venus. When it landed on the Venusian surface, it became the first spacecraft to land on another planet and first to transmit data from there back to Earth.Venus
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 in the Solar System and rotates in the opposite direction to most other planets (meaning the Sun rises in the west and sets 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 volcanism.
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 star. Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BC.As the planet with the closest approach 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.Venus Express
Venus Express (VEX) was the first Venus exploration mission of the European Space Agency (ESA). Launched in November 2005, it arrived at Venus in April 2006 and began continuously sending back science data from its polar orbit around Venus. Equipped with seven scientific instruments, the main objective of the mission was the long term observation of the Venusian atmosphere. The observation over such long periods of time had never been done in previous missions to Venus, and was key to a better understanding of the atmospheric dynamics. It was hoped that such studies can contribute to an understanding of atmospheric dynamics in general, while also contributing to an understanding of climate change on Earth. ESA concluded the mission in December 2014.
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