View source for Atmosphere of Venus

{{Short description|Gas layer surrounding Venus}}
{{Good article}}
{{AstronomicalAtmosphere
|name = Venus
|image = Venus - May 23 2018.png
|caption = Cloud structure in Venus's atmosphere <br/>revealed by ultraviolet observations
|info_refs = <ref name=Basilevsky2003/>
|height = {{convert|250|km|mi|abbr=on}}
|avg_surface_pressure = {{convert|93|bar|psi|abbr=on}}
|mass = 4.8{{E-sp|20}}&nbsp;kg
|composition_refs = <ref name=Basilevsky2003/><ref name=Bertaux2007/>
|species = [[Molar fraction]]
|chemical1 = [[Carbon dioxide]]
|quantity1 = 96.5 %
|chemical2 = [[Nitrogen]]
|quantity2 = 3.5 %
|chemical3 = [[Sulfur dioxide]]
|quantity3 = 150&nbsp;[[Parts per million|ppm]]
|chemical4 = [[Argon]]
|quantity4 = 70&nbsp;ppm
|chemical5 = [[Water vapor]]
|quantity5 = 20&nbsp;ppm
|chemical6 = [[Carbon monoxide]]
|quantity6 = 17&nbsp;ppm
|chemical7 = [[Helium]]
|quantity7 = 12&nbsp;ppm
|chemical8 = [[Neon]]
|quantity8 = 7&nbsp;ppm
|chemical9 = [[Hydrogen chloride]]
|quantity9 = 0.1–0.6&nbsp;ppm
|chemical10 = [[Hydrogen fluoride]]
|quantity10 = 0.001–0.005&nbsp;ppm
}}
The '''atmosphere of Venus''' is the very dense layer of gases surrounding the planet [[Venus]]. Venus's [[atmosphere]] is composed of 96.5% [[carbon dioxide]] and 3.5% [[nitrogen]], with other chemical compounds present only in trace amounts.<ref name=Basilevsky2003/> It is much denser and hotter than [[atmosphere of Earth|that of Earth]]; the temperature at the surface is 740&nbsp;[[Kelvin|K]] (467&nbsp;°C, 872&nbsp;°F), and the pressure is {{convert|93|bar|psi|abbr=on}}, roughly the pressure found {{convert|900|m|ft|abbr=on}} under water on Earth. The atmosphere of Venus supports decks of opaque clouds of [[sulfuric acid]] that cover the entire planet, preventing [[optics|optical]] Earth-based and orbital observation of the surface. Information about surface [[topography]] has been obtained exclusively by [[radar imaging]].
 
Aside from the very surface layers, the atmosphere is in a state of vigorous circulation.<ref name=Svedhem2007/> The upper layer of [[troposphere]] exhibits a phenomenon of [[Atmospheric super-rotation|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&nbsp;m/s (≈360&nbsp;km/h or 220&nbsp;mph)<ref name=Svedhem2007/> 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.<ref>{{cite journal |author=Normile, Dennis |title=Mission to probe Venus's curious winds and test solar sail for propulsion|journal=Science|pages=677|volume=328|date=2010|doi=10.1126/science.328.5979.677-a|pmid=20448159|issue=5979|bibcode= 2010Sci...328..677N}}</ref> 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 2.8&nbsp;m/s (≈10&nbsp;km/h or 6.2&nbsp;mph) on the surface.<ref>DK Space Encyclopedia: ''Atmosphere of Venus'' p 58.</ref> Near the poles are [[anticyclonic]] structures called polar [[vortex|vortices]]. Each vortex is double-eyed and shows a characteristic S-shaped pattern of clouds.<ref name=Piccioni2007/> Above there is an intermediate layer of [[mesosphere]] which separates the troposphere from the [[thermosphere]].<ref name=Svedhem2007/><ref name=Bertaux2007/> The [[thermosphere]] is also characterized by strong circulation, but very different in its nature—the gases heated and partially [[ionization|ionized]] by [[sunlight]] in the sunlit hemisphere migrate to the dark hemisphere where they [[recombination (chemistry)|recombine]] and [[downwelling|downwell]].<ref name=Bertaux2007/>

Unlike Earth, Venus lacks a magnetic field. Its [[ionosphere]] separates the atmosphere from [[outer space]] and the [[solar wind]]. This ionized 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]].<ref name=Svedhem2007/> It is speculated that the atmosphere of Venus up to around 4&nbsp;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 gas]]es.<ref name=Kasting/><ref>{{cite web |url=http://www.whiteworld.com/technoland/stories-nonfic/2008-stories/Venus-temp.htm|title=How Hot is Venus?|date=May 2006}}</ref>

Despite the harsh conditions on the surface, the atmospheric pressure and temperature at about 50&nbsp;km to 65&nbsp;km above the surface of the planet are 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 [[Observations and explorations of Venus|exploration]] and [[Colonization of Venus|colonization]].<ref name=Landis2003>{{cite journal|url=http://link.aip.org/link/?APCPCS/654/1193/1 |title=Colonization of Venus |first=Geoffrey A. |last=Landis |journal=AIP Conf. Proc. |volume=654 |issue=1 |pages=1193–1198 |doi=10.1063/1.1541418 |date=2003 |bibcode=2003AIPC..654.1193L |url-status=dead |archive-url=https://archive.today/20120711103532/http://link.aip.org/link/?APCPCS/654/1193/1 |archive-date=2012-07-11 }}</ref>

==History==

[[Christiaan Huygens]] was the first to hypothesize the existence of an atmosphere on Venus. In the Book II of Cosmotheoros, published in 1698, he writes:<ref>{{Cite web |title=The Cosmotheoros of Christiaan Huygens - Book II |url=https://webspace.science.uu.nl/~gent0113/huygens/huygens_ct_en_book_2.htm |access-date=2022-10-06 |website=webspace.science.uu.nl}}</ref>{{blockquote|I have often wonder’d that when I have viewed Venus at her nearest to the Earth, when she resembled an Half-moon, just beginning to have something like Horns, through a Telescope of 45 or 60 Foot long, she always appeared to me all over equally lucid, that I can’t say I observ’d so much as one spot in her, tho in Jupiter and Mars, which seem much less to us, they are very plainly perceived. For if Venus had any such thing as Sea and Land, the former must necessarily show much more obscure than the other, as anyone may satisfy himself, that from a very high Mountain will but look down upon our Earth. I thought that perhaps the too brisk Light of Venus might be the occasion of this equal appearance; but when I used an Eye-glass that was smok’d for the purpose, it was still the same thing. What then, must Venus have no Sea, or do the Waters there reflect the Light more than ours do, or their Land less? or rather (which is most probable in my opinion) is not all that Light we see reflected from an Atmosphere surrounding Venus, which being thicker and more solid than that in Mars or Jupiter, hinders our seeing any thing of the Globe it self, and is at the same time capable of sending back the Rays that it receives from the Sun?}}

Decisive evidence for the atmosphere of Venus was provided by [[Mikhail Lomonosov]], based on his observation of the transit of Venus in 1761 in a small observatory near his house in [[Saint Petersburg]], [[Russia]].<ref name=Shiltsev2014>{{cite journal |title=The 1761 Discovery of Venus' Atmosphere: Lomonosov and Others |journal=[[Journal of Astronomical History and Heritage]]|bibcode=2014JAHH...17...85S |s2cid=53394126 |last1=Shiltsev |first1=Vladimir |year=2014 |volume=17 |issue=1 |page=85 |doi=10.3724/SP.J.1440-2807.2014.01.06 }}</ref>

==Structure and composition==

===Composition===
[[File:Atmosphere of venus.png|300px|right|thumb|Composition of the atmosphere of Venus. The chart on the right is an expanded view of the trace elements that all together do not even make up a tenth of a percent.]]
The atmosphere of Venus is composed of 96.5% [[carbon dioxide]], 3.5% [[nitrogen]], and traces of other gases, most notably [[sulfur dioxide]].<ref name=SolarSystemEncyclopedia>{{cite book |last1=Taylor|first1=Fredric W.|editor1-last=Tilman|editor1-first=Spohn|editor2-last=Breuer|editor2-first=Doris|editor3-last=Johnson|editor3-first=T. V.|title=Encyclopedia of the Solar System|date=2014|publisher=Elsevier Science & Technology|location=Oxford|isbn=9780124158450|edition=3rd|chapter-url=http://literati.credoreference.com/content/entry/estsolar/venus_atmosphere/0|access-date=12 January 2016|chapter=Venus: Atmosphere}}</ref> 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.<ref name=Basilevsky2003/><ref name=Institutdemecanique>{{cite web|url=http://www.imcce.fr/vt2004/en/fiches/fiche_n13_eng.html|title=Clouds and atmosphere of Venus|publisher=[[Institut de mécanique céleste et de calcul des éphémérides]]|access-date=2008-01-22|url-status=dead|archive-url=https://web.archive.org/web/20110721211122/http://www.imcce.fr/vt2004/en/fiches/fiche_n13_eng.html|archive-date=2011-07-21}}</ref>

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.<ref name=Bertaux2007/><ref name=Svedhem2007/> 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,<ref name=Lovelock1979>{{cite book |title=Gaia: A New Look at Life on Earth|url=https://archive.org/details/gaianewlookatlif00loverich|url-access=registration|author=Lovelock, James|isbn=978-0-19-286218-1|publisher=Oxford University Press|date=1979}}</ref> with the remainder being mostly bound up in water vapour and [[sulfuric acid]] (H<sub>2</sub>SO<sub>4</sub>). Strong evidence of significant hydrogen loss over the historical evolution of the planet is the very high [[Deuterium#Abundance|D–H ratio]] measured in the Venusian atmosphere.<ref name=Svedhem2007/> The ratio is about 0.015–0.025, which is 100–150 times higher than the terrestrial value of 1.6{{e|−4}}.<ref name=Bertaux2007/><ref>{{cite journal |doi=10.1016/j.icarus.2013.02.010|title=Observations of D/H ratios in H2O, HCl, and HF on Venus and new DCl and DF line strengths|journal=Icarus|volume=224|issue=1|pages=57–65|year=2013|last1=Krasnopolsky|first1=V.A.|last2=Belyaev|first2=D.A.|last3=Gordon|first3=I.E.|last4=Li|first4=G.|last5=Rothman|first5=L.S.|bibcode= 2013Icar..224...57K}}</ref> According to some measurements, in the upper atmosphere of Venus D/H ratio is 1.5 higher than in the bulk atmosphere.<ref name=Bertaux2007/>

{{Multiple image
| align             = center
| direction         = horizontal
| header            = Atmospheric composition
| footer            = Green colour—water vapour, red—carbon dioxide, WN—[[wavenumber]] (other colours have different meanings, shorter [[wavelength]]s on the right, longer on the left).
| width1            = 380
| image1            = Synthetic atmosphere absorption spectrum.gif
| alt1              = The atmosphere of Earth is represented as a series of coloured spikes. The green of water dominates, while the red of carbon dioxide clusters near the left side.
| caption1          = Absorption spectrum of a simple gas mixture corresponding to [[Atmosphere of Earth|Earth's atmosphere]]
| width2            = 400
| image2            = Synthetic Venus atmosphere absorption spectrum.gif
| alt2              = The atmosphere of Venus is represented on the same graph. Here the red of carbon dioxide is almost overwhelming, but the green of water and the purple of carbon monoxide are present.
| caption2          = The composition of the atmosphere of Venus based on [[HITRAN]] data<ref name=HITRAN>{{cite web |url=http://www.cfa.harvard.edu/hitran/ |title=The HITRAN Database |publisher=Atomic and Molecular Physics Division, [[Harvard-Smithsonian Center for Astrophysics]] |access-date=8 August 2012 |quote=HITRAN is a compilation of spectroscopic parameters that a variety of computer codes use to predict and simulate the transmission and emission of light in the atmosphere. |archive-date=14 August 2012 |archive-url=https://web.archive.org/web/20120814161841/http://www.cfa.harvard.edu/hitran/ |url-status=live }}</ref> created using HITRAN on the Web system.<ref name=hitraniaoru>{{cite web |url=http://hitran.iao.ru/ |title=HITRAN on the Web Information System |publisher=[[V.E. Zuev Institute of Atmospheric Optics]] |access-date=11 August 2012 |archive-date=19 April 2013 |archive-url=https://web.archive.org/web/20130419191421/http://hitran.iao.ru/ |url-status=live }}</ref>
}}

==== Phosphine ====
In 2020, there was considerable discussion regarding whether [[phosphine]] (PH<sub>3</sub>) might be present in trace amounts in Venus's atmosphere. This would be noteworthy as phosphine is a potential biomarker indicating the presence of life. This was prompted by an announcement in September 2020 that this compound had been detected in trace amounts. No known abiotic source present on Venus could produce phosphine in the quantities detected.<ref name="Greaves et al">{{cite journal |last1=Greaves |first1=Jane S. |last2=Richards |first2=A.M.S. |last3=Bains |first3=W |title=Phosphine gas in the cloud decks of Venus |journal=Nature Astronomy |date=14 September 2020 |volume=5 |issue=7 |pages=655–664 |doi=10.1038/s41550-020-1174-4 |arxiv=2009.06593 |bibcode=2021NatAs...5..655G |s2cid=221655755 |url=https://www.nature.com/articles/s41550-020-1174-4#citeas |access-date=16 September 2020}}</ref><ref name="sample1">{{cite news |last1=Sample |first1=Ian |title=Scientists find gas linked to life in atmosphere of Venus |url=https://www.theguardian.com/science/2020/sep/14/scientists-find-gas-linked-to-life-in-atmosphere-of-venus |access-date=16 September 2020 |work=The Guardian |date=14 September 2020}}</ref> On review, an interpolation error was discovered that resulted in multiple spurious spectroscopic lines, including the spectral feature of phosphine. Re-analysis of data with the fixed algorithm either do not result in the detection of the phosphine<ref>{{citation|last1=Snellen|first1=I. A. G.|title=Re-analysis of the 267-GHz ALMA observations of Venus No statistically significant detection of phosphine|journal=Astronomy and Astrophysics|volume=644|pages=L2|year=2020|arxiv=2010.09761|bibcode=2020A&A...644L...2S|doi=10.1051/0004-6361/202039717|last2=Guzman-Ramirez|first2=L.|last3=Hogerheijde|first3=M. R.|last4=Hygate|first4=A. P. S.|last5=van der Tak|first5=F. F. S.|s2cid=224803085}}</ref><ref name="Thompson2020">{{citation|last1=Thompson|first1=M. A.|title=The statistical reliability of 267 GHz JCMT observations of Venus: No significant evidence for phosphine absorption|journal=Monthly Notices of the Royal Astronomical Society: Letters|volume=501|issue=1|pages=L18–L22|year=2021|arxiv=2010.15188|bibcode=2021MNRAS.501L..18T|doi=10.1093/mnrasl/slaa187|doi-access=free |s2cid=225103303}}</ref> or detected it with much lower concentration of 1&nbsp;ppb.<ref name="Greaves202011" />

The announcement promoted re-analysis of [[Pioneer Venus project|Pioneer Venus]] data which found part of [[chlorine]] and all of [[hydrogen sulfide]] spectral features are instead [[phosphine]]-related, meaning lower than thought concentration of [[chlorine]] and non-detection of [[hydrogen sulfide]].<ref name="Mogul2020">{{citation|arxiv=2009.12758|title=Is Phosphine in the Mass Spectra from Venus' Clouds?|year=2020|last1=Mogul|first1=Rakesh|last2=Limaye|first2=Sanjay S.|last3=Way|first3=M. J.|last4=Cordova |first4=Jamie A. Jr|doi=10.1002/essoar.10504552.4|s2cid=231854943}}</ref> Another re-analysis of archived infrared spectral measurements by the [[NASA Infrared Telescope Facility]] in 2015 did not reveal any phosphine in the Venusian atmosphere, placing an upper limit for phosphine concentration at 5&nbsp;ppb—a quarter of the spectroscopic value reported in September.<ref>{{citation|arxiv=2010.07817|title=A stringent upper limit of the PH3 abundance at the cloud top of Venus|year=2020|doi=10.1051/0004-6361/202039559|last1=Encrenaz|first1=T.|author1-link=Thérèse Encrenaz|last2=Greathouse|first2=T. K.|last3=Marcq|first3=E.|last4=Widemann|first4=T.|last5=Bézard|first5=B.|last6=Fouchet|first6=T.|last7=Giles|first7=R.|last8=Sagawa|first8=H.|last9=Greaves|first9=J.|last10=Sousa-Silva|first10=C.|journal=Astronomy & Astrophysics|volume=643|pages=L5|bibcode=2020A&A...643L...5E|s2cid=222377688}}</ref>

In 2022, no phosphine detection with an upper limit concentration of 0.8 ppb was announced for Venusian altitudes of 75–110&nbsp;km.<ref>{{citation|arxiv=2210.13519|year=2022|title=Phosphine in the Venusian Atmosphere: A Strict Upper Limit from SOFIA GREAT Observations|doi=10.1029/2022GL101055 |last1=Cordiner |first1=M. A. |last2=Villanueva |first2=G. L. |last3=Wiesemeyer |first3=H. |last4=Milam |first4=S. N. |last5=De Pater |first5=I. |last6=Moullet |first6=A. |last7=Aladro |first7=R. |last8=Nixon |first8=C. A. |last9=Thelen |first9=A. E. |last10=Charnley |first10=S. B. |last11=Stutzki |first11=J. |last12=Kofman |first12=V. |last13=Faggi |first13=S. |last14=Liuzzi |first14=G. |last15=Cosentino |first15=R. |last16=McGuire |first16=B. A. |journal=Geophysical Research Letters |volume=49 |issue=22 |bibcode=2022GeoRL..4901055C |s2cid=253086965 }}</ref>

In September 2024, the preliminary analysis of the [[James Clerk Maxwell Telescope|JCMT-Venus]] data has confirmed the existence of phosphine in the atmosphere of Venus, with the concentration 300 ppb at altitude 55km. Further data processing is still needed to measure phosphine concentration deeper in the Venusian cloud deck.<ref>{{citation|arxiv=2409.13438|title=Venus Phosphine: Updates and lessons learned|year=2024 |last1=Clements |first1=David L. }}</ref>

====Ammonia====
The ammonia in the atmosphere of Venus was tentatively detected by two atmospheric probes - [[Venera 8]] and [[Pioneer Venus Multiprobe]], although the detection was rejected that time due to poorly characterized sensors behavior in Venusian environment and ammonia believed to be chemically unstable in the strongly oxidizing atmosphere of Venus.<ref>{{citation|arxiv=2211.07786|year=2022|title=Ammonia and Phosphine in the Clouds of Venus as Potentially Biological Anomalies|last1=Cleland |first1=Carol E. |last2=Rimmer |first2=Paul B. |journal=Aerospace |volume=9 |issue=12 |page=752 |doi=10.3390/aerospace9120752 |bibcode=2022Aeros...9..752C |doi-access=free }}</ref>

===Troposphere===
[[File:Atmosphere composition.gif|thumb|right|300px|Comparison of Atmosphere Compositions – [[Venus]], [[Atmosphere of Mars|Mars]], [[Atmosphere of Earth|Earth]] (past and present).]]
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&nbsp;km. The winds are slow near the surface,<ref name=Basilevsky2003>{{cite journal |last=Basilevsky|first=Alexandr T.|author2=Head, James W.|title=The surface of Venus|journal=Rep. Prog. Phys.|date=2003|volume=66|issue=10|pages=1699–1734|doi=10.1088/0034-4885/66/10/R04 |bibcode= 2003RPPh...66.1699B|s2cid=250815558 }}</ref> but at the top of the troposphere the temperature and pressure reaches Earth-like levels and clouds pick up speed to 100&nbsp;m/s (360&nbsp;km/h).<ref name=Svedhem2007/><ref name=Patzold2007/>
[[File:Lomonosov's drawings for his opening of Venus atmosphere 1761.jpg|thumb|left|150px|1761 drawing by [[Mikhail Lomonosov]] in his work on the discovery of atmosphere of Venus]]
The atmospheric pressure at the surface of Venus is about 92 times that of the Earth, similar to the pressure found {{convert|900|m|ft|abbr=on}} below the surface of the ocean. The atmosphere has a mass of 4.8{{e|20}} kg, about 93 times the mass of the Earth's total atmosphere.<ref name=":2">{{Cite web |title=Venus Fact Sheet |url=https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html |access-date=2022-12-02 |website=nssdc.gsfc.nasa.gov}}</ref> The density of the air at the surface is 65&nbsp;kg/m<sup>3</sup>,<ref name=":2" /> which is 6.5% that of liquid water on Earth.<ref name="u3r1a"/> 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, with a 6.5% density of water,<ref name="u3r1a">{{cite journal | last1=Lebonnois | first1=Sebastien | last2=Schubert | first2=Gerald | title=The deep atmosphere of Venus and the possible role of density-driven separation of CO2 and N2 | journal=Nature Geoscience | publisher=Springer Science and Business Media LLC | volume=10 | issue=7 | date=2017-06-26 | issn=1752-0894 | doi=10.1038/ngeo2971 | pages=473–477| bibcode=2017NatGe..10..473L | s2cid=133864520 | url=https://hal.archives-ouvertes.fr/hal-01635402/file/deepatm_persp_rev2.pdf }}</ref> 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).<ref name=Fegley1997>{{cite book |title=Geochemistry of Surface-Atmosphere Interactions on Venus (Venus II: Geology, Geophysics, Atmosphere, and Solar Wind Environment)|isbn=978-0-8165-1830-2|publisher=University of Arizona Press|date=1997|author=Fegley, B.|display-authors=etal}}</ref> Particularly at possible higher atmospheric pressures in Venus' past might have created an even more fluid-like layer of supercritical carbon dioxide shaping Venus' landscape; altogether, it is unclear how the supercritical environment behaves and is shaped.<ref name="Choi 2014">{{cite web | last=Choi | first=Charles Q. | title=Venus Gets Weirder: CO2 Oceans May Have Covered Surface | website=Space.com | date=2014-12-28 | url=https://www.space.com/28112-venus-weird-superfluid-oceans.html | access-date=2023-04-13}}</ref>

The large amount of CO<sub>2</sub> 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&nbsp;K (467&nbsp;°C),<ref name=Institutdemecanique/> hotter than any other terrestrial planet in the [[Solar System]], even that of [[Mercury (planet)|Mercury]] despite being located farther out from the Sun and receiving only 25% of the solar energy (per unit area) Mercury does.{{citation needed|date=October 2012}} The average temperature on the surface is above the melting points of [[lead]] (600&nbsp;K, 327&nbsp;°C), [[tin]] (505&nbsp;K, 232&nbsp;°C), and [[zinc]] (693&nbsp;K, 420&nbsp;°C). The thick troposphere also makes the difference in temperature between the day and night side small, even though the slow [[retrograde motion|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.<ref name=Basilevsky2003/>
{| class="wikitable" style="float:right; clear:right; margin:0.5em 0 0.5em 1em;"
|+Atmosphere<ref>{{Cite book|title=Understanding Our Universe|last=Blumenthal, Kay, Palen, Smith|publisher=W.W. Norton & Company|year=2012|isbn=9780393912104|location=New York|pages=167}}</ref>
|-
|colspan="3"|[[File:11214 2023 956 Fig6 HTML.webp|300px]]
|-
!Height<br />(km)!!Temp.<br />(°C)!!Atmospheric pressure<br />([[atmosphere (unit)|atm]])
|-
|{{0|00}}0||{{0}}462||92.10
|-
|{{0|00}}5||{{0}}424||66.65
|-
|{{0}}10||{{0}}385||47.39
|-
|{{0}}15||{{0}}348||33.04
|-
|{{0}}20||{{0}}306||22.52
|-
|{{0}}25||{{0}}264||14.93
|-
|{{0}}30||{{0}}222||{{0}}9.851
|-
|{{0}}35||{{0}}180||{{0}}5.917
|-
|{{0}}40||{{0}}143||{{0}}3.501
|-
|{{0}}45||{{0}}110||{{0}}1.979
|-
|{{0}}50||{{0|00}}75||{{0}}1.066
|-
|{{0}}55||{{0|00}}27||{{0}}0.531&nbsp;4
|-
|{{0}}60||{{0}}−10||{{0}}0.235&nbsp;7
|-
|{{0}}65||{{0}}−30||{{0}}0.097&nbsp;65
|-
|{{0}}70||{{0}}−43||{{0}}0.036&nbsp;90
|-
|{{0}}80||{{0}}−76||{{0}}0.004&nbsp;760
|-
|{{0}}90||−104||{{0}}0.000&nbsp;373&nbsp;6
|-
|100||−112||{{0}}0.000&nbsp;026&nbsp;60
|}

The troposphere on Venus contains 99% of the atmosphere by mass. 90% of the atmosphere of Venus is within 28&nbsp;km (17.5&nbsp;mi) of the surface; by comparison, 90% of the atmosphere of Earth is within 16&nbsp;km (10&nbsp;mi) of the surface. At a height of 50&nbsp;km (31&nbsp;mi) the atmospheric pressure is approximately equal to that at the surface of Earth.<ref name=Nave>{{cite web |url=http://hyperphysics.phy-astr.gsu.edu/hbase/solar/venusenv.html|title=The Environment of Venus|author=Nave, Carl R. |work=[[Hyperphysics]]|publisher=Department of Physics and Astronomy, Georgia State University|access-date=2008-01-23 |archive-url= https://web.archive.org/web/20080214034840/http://hyperphysics.phy-astr.gsu.edu/Hbase/solar/venusenv.html |archive-date= 14 February 2008 |url-status= live}}</ref> On the night side of Venus clouds can still be found at 80&nbsp;km (50&nbsp;mi) above the surface.<ref name=CloudyWorld/>

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&nbsp;km.<ref name=Patzold2007/> According to measurements by the ''[[Magellan probe|Magellan]]'' and ''[[Venus Express]]'' probes, the altitude from 52.5 to 54&nbsp;km has a temperature between 293&nbsp;K (20&nbsp;°C) and 310&nbsp;K (37&nbsp;°C), and the altitude at 49.5&nbsp;km above the surface is where the pressure becomes the same as Earth at sea level.<ref name=Patzold2007/><ref name=Profiles>{{cite web|url=http://www.shadetreephysics.com/vel/1918vpt.htm|title=Venus Atmosphere Temperature and Pressure Profiles|publisher=Shade Tree Physics|access-date=2008-01-23|archive-url=https://web.archive.org/web/20080205025041/http://www.shadetreephysics.com/vel/1918vpt.htm|archive-date=2008-02-05|url-status=dead}}</ref> As crewed ships sent to Venus would be able to compensate for differences in temperature to a certain extent, anywhere from about 50 to 54&nbsp;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&nbsp;K (0&nbsp;°C) to 323&nbsp;K (50&nbsp;°C) and the air pressure the same as habitable regions of Earth.<ref name=Landis2003/><ref name=Landis2002/> As CO<sub>2</sub> is heavier than air, the colony's air (nitrogen and oxygen) could keep the structure floating at that altitude like a [[dirigible]].

====Circulation====
[[File:The Evening Star in a New Light (3083434398).jpg|thumb|Composite image of the polar vortex of Venus in strong red (red image is an infrared view of hot high clouds and the grey image is an ultra-violet view of lower clouds)]]
The circulation in Venus's troposphere follows the so-called [[cyclostrophic balance|cyclostrophic flow]].<ref name=Svedhem2007>{{cite journal |last=Svedhem|first=Hakan|author2=Titov, Dmitry V.|author3= Taylor, Fredric V.|author4= Witasse, Oliver|title=Venus as a more Earth-like planet|journal=[[Nature (journal)|Nature]]|date=2007|volume=450|pages=629–632|doi=10.1038/nature06432 |bibcode=2007Natur.450..629S|pmid=18046393|issue=7170|s2cid=1242297}}</ref> Its windspeeds are roughly determined by the balance of the [[pressure gradient]] and [[Centrifugal force (fictitious)|centrifugal]] forces in almost purely [[zonal flow]]. In contrast, the circulation in the Earth's atmosphere is governed by the [[geostrophic wind|geostrophic]] balance.<ref name=Svedhem2007/> Venus's windspeeds can be directly measured only in the upper troposphere (tropopause), between 60 and 70&nbsp;km, altitude, which corresponds to the upper cloud deck.<ref name=Markiewicz2007>{{cite journal |last=Markiewicz|first=W.J.|title=Morphology and dynamics of the upper cloud layer of Venus|journal=Nature|date=2007|volume=450|pages=633–636|doi=10.1038/nature06320 |bibcode=2007Natur.450..633M|pmid=18046394|issue=7170|author2=Titov, D.V.|last3=Limaye|first3=S.S.|last4=Keller|first4=H. U.|last5=Ignatiev|first5=N.|last6=Jaumann|first6=R.|last7=Thomas|first7=N.|last8=Michalik|first8=H.|last9=Moissl|first9=R. |s2cid=4420096|display-authors=8}}</ref> The cloud motion is usually observed in the [[ultraviolet]] part of the [[spectrum]], where the contrast between clouds is the highest.<ref name=Markiewicz2007/> The linear wind speeds at this level are about 100&nbsp;±&nbsp;10&nbsp;m/s at lower than 50° latitude. They are [[retrograde and direct motion|retrograde]] in the sense that they blow in the direction of the retrograde rotation of the planet.<ref name=Markiewicz2007/> 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.<ref name=Svedhem2007/> In other words, these high-speed winds circle the whole planet faster than the planet itself rotates.<ref name=Landis2002>{{cite conference|url=http://gltrs.grc.nasa.gov/reports/2002/TM-2002-211467.pdf |title=Atmospheric Flight on Venus |first=Geoffrey A. |last=Landis |author2=Colozza, Anthony |author3=LaMarre, Christopher M |conference=40th Aerospace Sciences Meeting and Exhibit sponsored by the American Institute of Aeronautics and Astronautics |place=Reno, Nevada |date=January 14–17, 2002 |book-title=Proceedings |pages=IAC–02–Q.4.2.03, AIAA–2002–0819, AIAA0 |issue=5 |url-status=dead |archive-url=https://web.archive.org/web/20111016143148/http://gltrs.grc.nasa.gov/reports/2002/TM-2002-211467.pdf |archive-date=2011-10-16 }}</ref> The super-rotation on Venus is differential, which means that the [[equatorial orbit|equatorial]] troposphere super-rotates more slowly than the troposphere at the midlatitudes.<ref name=Markiewicz2007/> The winds also have a strong vertical gradient. They decline deep in the troposphere with the rate of 3&nbsp;m/s&nbsp;per&nbsp;km.<ref name=Svedhem2007/> 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&nbsp;m/s and with an average of 0.3 to 1.0&nbsp;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.<ref name=Basilevsky2003/><ref name=Moskin>{{cite journal |last1=Moshkin|first1=B.E.|last2=Ekonomov|first2=A.P.|last3=Golovin|first3=Iu.M.|date=1979|title=Dust on the surface of Venus|journal=Kosmicheskie Issledovaniia (Cosmic Research)|volume=17|pages=280–285 |bibcode=1979KosIs..17..280M}}</ref>

[[File:Venus circulation.jpg|300px|thumb|Meridional (north-south) component of the atmospheric circulation in the atmosphere of Venus. Note that the meridional circulation is much lower than the zonal circulation, which transports heat between the day and night sides of the planet]]
All winds on Venus are ultimately driven by [[convection]].<ref name=Svedhem2007/> 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]].<ref name=Svedhem2007/> 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.<ref name=Svedhem2007/> 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.<ref name=Svedhem2007/> Poleward of the Hadley cell a different pattern of circulation is observed. In the latitude range 60°–70° cold polar collars exist.<ref name=Svedhem2007/><ref name=Piccioni2007/> They are characterized by temperatures about 30–40&nbsp;K lower than in the upper troposphere at nearby latitudes.<ref name=Piccioni2007/> The lower temperature is probably caused by the upwelling of the air in them and by the resulting [[adiabatic]] cooling.<ref name=Piccioni2007/> Such an interpretation is supported by the denser and higher clouds in the collars. The clouds lie at 70–72&nbsp;km altitude in the collars—about 5&nbsp;km higher than at the poles and low latitudes.<ref name=Svedhem2007/> A connection may exist between the cold collars and high-speed midlatitude jets in which winds blow as fast as 140&nbsp;m/s. Such jets are a natural consequence of the Hadley-type circulation and should exist on Venus between 55 and 60° latitude.<ref name=Markiewicz2007/>

Odd structures known as [[polar vortex|polar vortices]] lie within the cold polar collars.<ref name=Svedhem2007/> 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 [[dipole]]s.<ref name=Piccioni2007>{{cite journal|last=Piccioni|first=G.|title=South-polar features on Venus similar to those near the north pole|journal=Nature|date=2007|volume=450|pages=637–640|doi=10.1038/nature06209|bibcode=2007Natur.450..637P|pmid=18046395|issue=7170|author2=Drossart, P.|last3=Sanchez-Lavega|first3=A.|last4=Hueso|first4=R.|last5=Taylor|first5=F. W.|last6=Wilson|first6=C. F.|last7=Grassi|first7=D.|last8=Zasova|first8=L.|last9=Moriconi|first9=M. |s2cid=4422507|display-authors=8|url=https://zenodo.org/record/1064102}}</ref> Vortices rotate with the period of about 3 days in the direction of general super-rotation of the atmosphere.<ref name=Piccioni2007/> The linear wind speeds are 35–50&nbsp;m/s near their outer edges and zero at the poles.<ref name=Piccioni2007/> The temperature at the cloud-tops in each polar vortex is much higher than in the nearby polar collars, reaching 250&nbsp;K (−23&nbsp;°C).<ref name=Piccioni2007/> The conventional interpretation of the polar vortices is that they are [[anticyclone]]s with downwelling in the centre and upwelling in the cold polar collars.<ref name=Piccioni2007/> 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&nbsp;km altitude, i.e. to the base of the clouds.<ref name=Piccioni2007/> 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%.<ref name=Markiewicz2007/> This event was probably caused by an injection of [[sulfur dioxide]] into the mesosphere, which then condensed, forming a bright haze.<ref name=Markiewicz2007/> The two eyes in the vortices have yet to be explained.<ref name=SouthPole/>

[[File:Venus clouds Galileo Color PIA00124.jpg|left|thumb|False colour near-infrared (2.3&nbsp;μm) image of the deep atmosphere of Venus obtained by [[Galileo (spacecraft)|''Galileo'']], red areas are signatures of the hot surface radiating through the atmosphere relatively unhindered. The dark spots are clouds silhouetted against the very hot lower atmosphere emitting thermal infrared radiation.]]
The first vortex on Venus was discovered at the north pole by the [[Pioneer Venus project|Pioneer Venus]] mission in 1978.<ref name=Lakdawalla>{{cite web |url=http://www.planetary.org/news/2006/0414_First_Venus_Express_VIRTIS_Images_Peel.html|title=First Venus Express VIRTIS Images Peel Away the Planet's Clouds|author=Lakdawalla, Emily |date=2006-04-14|access-date=2008-01-17 |archive-url= https://web.archive.org/web/20071222143246/http://www.planetary.org/news/2006/0414_First_Venus_Express_VIRTIS_Images_Peel.html |archive-date= 22 December 2007 |url-status= live}}</ref> A discovery of the second large "double-eyed" [[polar vortex|vortex]] at the south pole of Venus was made in the summer of 2006 by ''Venus Express'', which came with no surprise.<ref name=SouthPole>{{cite web |url=http://www.esa.int/SPECIALS/Venus_Express/SEMYGQEFWOE_0.html|title=Double vortex at Venus South Pole unveiled!|publisher=European Space Agency|date=2006-06-27|access-date=2008-01-17 |archive-url= https://web.archive.org/web/20080107154945/http://www.esa.int/SPECIALS/Venus_Express/SEMYGQEFWOE_0.html |archive-date= 7 January 2008 |url-status= live}}</ref>

Images from the [[Akatsuki (spacecraft)|''Akatsuki'' orbiter]] revealed something similar to [[jet stream]] winds in the low and middle cloud region, which extends from 45 to 60&nbsp;km in altitude. The wind speed maximized near the equator. In September 2017, JAXA scientists named this phenomenon "Venusian equatorial jet".<ref name="Update Sep 2017">{{cite web |url=http://global.jaxa.jp/projects/sat/planet_c/topics.html#topics10633 |title=Venus: Jet-setting atmosphere |work=Japan Aerospace Exploration Agency (JAXA) |date=5 September 2017 |access-date=2017-09-26 }}</ref>

===Upper atmosphere and ionosphere===
The [[mesosphere]] of Venus extends from 65&nbsp;km to 120&nbsp;km in height, and the [[thermosphere]] begins at approximately 120&nbsp;km, eventually reaching the upper limit of the atmosphere (exosphere) at about 220 to 350&nbsp;km.<ref name=Patzold2007>{{cite journal |last=Patzold|first=M.|title=The structure of Venus' middle atmosphere and ionosphere|journal=Nature|date=2007|volume=450|pages=657–660|doi=10.1038/nature06239 |bibcode=2007Natur.450..657P |pmid=18046400 |issue=7170 |author2=Hausler, B.|last3=Bird |first3=M.K. |last4=Tellmann |first4=S. |last5=Mattei |first5=R. |last6=Asmar|first6=S. W. |last7=Dehant |first7=V.|last8=Eidel |first8=W. |last9=Imamura |first9=T. |s2cid=4415782|display-authors=8}}</ref> The [[exosphere]] begins when the atmosphere becomes so thin that the average number of collisions per air molecule is less than one.

The mesosphere of Venus can be divided into two layers: the lower one between 62 and 73&nbsp;km<ref name=mesosphere1>This thickness corresponds to the polar latitudes. It is narrower near the equator—65–67&nbsp;km.</ref> and the upper one between 73 and 95&nbsp;km.<ref name=Patzold2007/> In the first layer the temperature is nearly constant at 230&nbsp;K (−43&nbsp;°C). This layer coincides with the upper cloud deck. In the second layer, the temperature starts to decrease again, reaching about 165&nbsp;K (−108&nbsp;°C) at the altitude of 95&nbsp;km, where [[mesopause]] begins.<ref name=Patzold2007/> It is the coldest part of the Venusian dayside atmosphere.<ref name=Bertaux2007/> In the dayside mesopause, which serves as a boundary between the mesosphere and thermosphere and is located between 95 and 120&nbsp;km, temperature increases to a constant—about 300–400&nbsp;K (27–127&nbsp;°C)—value prevalent in the thermosphere.<ref name=Bertaux2007/> In contrast, the nightside Venusian thermosphere is the coldest place on Venus with temperature as low as 100&nbsp;K (−173&nbsp;°C). It is even called a cryosphere.<ref name=Bertaux2007/>

The circulation patterns in the upper mesosphere and thermosphere of Venus are completely different from those in the lower atmosphere.<ref name=Bertaux2007>{{cite journal |last=Bertaux|first=Jean-Loup |title=A warm layer in Venus' cryosphere and high-altitude measurements of HF, HCl, H2O and HDO |journal=Nature |date=2007 |volume=450 |pages=646–649 |doi=10.1038/nature05974 |bibcode=2007Natur.450..646B |pmid=18046397|issue=7170 |author2=Vandaele, Ann-Carine |last3=Korablev|first3=Oleg|last4=Villard|first4=E.|last5=Fedorova|first5=A.|last6=Fussen|first6=D.|last7=Quémerais|first7=E.|last8=Belyaev|first8=D.|last9=Mahieux|first9=A. |s2cid=4421875 |url=https://orbi.uliege.be/bitstream/2268/29200/1/Bertaux-2007-a%20warm.pdf |display-authors=8}}</ref> At altitudes 90–150&nbsp;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&nbsp;km.<ref name=Svedhem2007/><ref name=Bertaux2007/> The temperature of this layer—230&nbsp;K (−43&nbsp;°C)—is far higher than the typical temperature found in the nightside thermosphere—100&nbsp;K (−173&nbsp;°C).<ref name=Bertaux2007/> The air circulated from the dayside also carries oxygen atoms, which after [[Recombination (chemistry)|recombination]] form excited [[molecule]]s of [[oxygen]] in the long-lived [[singlet state]] (<sup>1</sup>Δ<sub>g</sub>), which then relax and emit [[infrared]] radiation at the wavelength 1.27&nbsp;μm. This radiation from the altitude range 90–100&nbsp;km is often observed from the ground and spacecraft.<ref name=Drossart2007>{{cite journal |last=Drossart|first=P. |title=A dynamic upper atmosphere of Venus as revealed by VIRTIS on Venus Express |journal=Nature|date=2007|volume=450|pages=641–645|doi=10.1038/nature06140 |bibcode=2007Natur.450..641D|pmid=18046396|issue=7170|author2=Piccioni, G.|last3=Gerard|first3=G.C.|last4=Lopez-Valverde|first4=M. A.|last5=Sanchez-Lavega|first5=A.|last6=Zasova|first6=L.|last7=Hueso|first7=R.|last8=Taylor|first8=F. W.|last9=Bézard|first9=B. |hdl=2268/29723 |s2cid=4344611 |display-authors=8|url=https://orbi.uliege.be/handle/2268/29723 }}</ref> The nightside upper mesosphere and thermosphere of Venus is also the source of non-[[local thermodynamic equilibrium]] emissions of CO<sub>2</sub> and [[nitric oxide]] molecules, which are responsible for the low temperature of the nightside thermosphere.<ref name=Drossart2007/>

The ''[[Venus Express]]'' probe has shown through [[occultation|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&nbsp;km and extends up to about 65&nbsp;km, whereas on the night side the cloud deck in the form of a thick haze reaches up to 90&nbsp;km in altitude—well into mesosphere, continuing even further to 105&nbsp;km as a more transparent haze.<ref name=CloudyWorld>{{cite web |url=http://www.venustoday.com/news/viewsr.html?pid=21319 |archive-url=https://web.archive.org/web/20070928123440/http://www.venustoday.com/news/viewsr.html?pid=21319 |url-status=dead |archive-date=2007-09-28 |title=Flying over the cloudy world&nbsp;– science updates from Venus Express |publisher=Venus Today |date=2006-07-12 |access-date=2007-01-17 }}</ref> In 2011, the spacecraft discovered that Venus has a thin [[ozone layer]] at an altitude of 100&nbsp;km.<ref>{{cite news |url=https://www.bbc.co.uk/news/science-environment-15203281 |title=Venus springs ozone layer surprise |last=Carpenter |first=Jennifer |date=7 October 2011 |publisher=BBC |access-date=2011-10-08}}</ref>

Venus has an extended [[ionosphere]] located at altitudes 120–300&nbsp;km.<ref name=Patzold2007/> 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 [[electron]]s is almost zero.<ref name=Patzold2007/> The ionosphere of Venus consists of three layers: v1 between 120 and 130&nbsp;km, v2 between 140 and 160&nbsp;km and v3 between 200 and 250&nbsp;km.<ref name=Patzold2007/> There may be an additional layer near 180&nbsp;km. The maximum electron volume density (number of electrons in a unit of volume) of 3{{e|11}}&nbsp;m<sup>−3</sup> is reached in the v2 layer near the [[subsolar point]].<ref name=Patzold2007/> The upper boundary of the ionosphere (the ionopause) is located at altitudes 220–375&nbsp;km and separates the [[Plasma (physics)|plasma]] of the planetary origin from that of the induced [[magnetosphere]].<ref name=Russell993/><ref name=Zhang2007/> The main ionic species in the v1 and v2 layers is O<sub>2</sub><sup>+</sup> ion, whereas the v3 layer consists of O<sup>+</sup> ions.<ref name=Patzold2007/> 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.<ref>{{cite journal |last1= Whitten |first1= R. C. |last2= McCormick |first2= P. T. |last3= Merritt |first3= David |author3-link= David Merritt |last4= Thompson |first4= K. W. |last5= Brynsvold |first5= R.R. |last6= Eich |first6= C.J. |last7= Knudsen |first7= W.C. |last8= Miller |first8= K.L.|display-authors=etal|title= Dynamics of the Venus ionosphere: A two-dimensional model study |journal= Icarus |volume= 60 |issue= 2 |pages= 317–326 |date= November 1984 |doi= 10.1016/0019-1035(84)90192-1 |bibcode=1984Icar...60..317W}}</ref>

[[File:Arc-1978-ac78-9464 copy.jpg|thumb|upright=1.5|The ionosphere of Venus and its interaction with the [[solar wind]].]]

===Induced magnetosphere===
[[File:Venusian magnetosphere.svg|thumb|Venus interacts with the solar wind. Components of the induced magnetosphere are shown.]]
Venus is known not to have a [[magnetic field]].<ref name=Russell993>{{cite journal |last=Russell|first=C.T.|title= Planetary Magnetospheres |journal=Rep. Prog. Phys.|volume=56|issue=6|pages=687–732|date=1993 |bibcode=1993RPPh...56..687R|doi= 10.1088/0034-4885/56/6/001|s2cid=250897924 }}</ref><ref name=Zhang2007/> 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 (geology)|mantle]]. Venus only has an induced [[magnetosphere]] formed by the Sun's magnetic field carried by the [[solar wind]].<ref name=Russell993/> 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]].<ref name=Russell993/><ref name=Zhang2007>{{cite journal |last=Zhang|first=T.L.|title=Little or no solar wind enters Venus' atmosphere at solar minimum|journal=Nature|date=2007|volume=450|pages=654–656|doi=10.1038/nature06026 |bibcode=2007Natur.450..654Z|pmid=18046399|issue=7170|author2=Delva, M.|last3=Baumjohann|first3=W.|last4=Auster|first4=H.-U.|last5=Carr|first5=C.|last6=Russell|first6=C. T.|last7=Barabash|first7=S.|last8=Balikhin|first8=M.|last9=Kudela|first9=K. |s2cid=4412430|display-authors=8}}</ref>

At the subsolar point the bow shock stands 1900&nbsp;km (0.3 R<sub>v</sub>, where R<sub>v</sub> is the radius of Venus) above the surface of Venus. This distance was measured in 2007 near the solar activity minimum.<ref name=Zhang2007/> Near the solar activity maximum it can be several times further from the planet.<ref name=Russell993/> The magnetopause is located at the altitude of 300&nbsp;km.<ref name=Zhang2007/> The upper boundary of the [[ionosphere]] (ionopause) is near 250&nbsp;km. Between the magnetopause and ionopause there exists a magnetic barrier—a local enhancement of the magnetic field, which prevents the 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&nbsp;[[Tesla (unit)|nT]].<ref name=Zhang2007/> 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 [[electron]]s and ions in the magnetotail are around 100 and 1000&nbsp;[[electronvolt|eV]] respectively.<ref name=Barabash2007/>

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.<ref>[https://web.archive.org/web/20040303125126/http://sunearth.gsfc.nasa.gov/sunearthday/2004/vt_venus_planetary_2004.htm 2004 Venus Transit information page], Venus Earth and Mars, NASA</ref> The loss happens mainly via the magnetotail. Currently the main ion types being lost are O<sup>+</sup>, H<sup>+</sup> and He<sup>+</sup>. The ratio of [[hydrogen]] to [[oxygen]] losses is around 2 (i.e. almost [[stoichiometric]] for water) indicating the ongoing loss of water.<ref name=Barabash2007>{{cite journal |last=Barabash|first=S.|title=The loss of ions from Venus through the plasma wake|journal=Nature|date=2007|volume=450|pages=650–653|doi=10.1038/nature06434 |bibcode=2007Natur.450..650B|pmid=18046398|issue=7170|author2=Fedorov, A.|last3=Sauvaud|first3=J.J.|last4=Lundin|first4=R.|last5=Russell|first5=C. T.|last6=Futaana|first6=Y.|last7=Zhang|first7=T. L.|last8=Andersson|first8=H.|last9=Brinkfeldt|first9=K. |display-authors=8|url=https://deepblue.lib.umich.edu/bitstream/2027.42/62594/1/nature06434.pdf|hdl=2027.42/62594|s2cid=4419879|hdl-access=free}}</ref>

==Clouds==
[[File:Venus night side IR (Akatsuki).jpg|thumb|Infrared image of the night-side of Venus, showing different layers of clouds at altitudes of 35 to 50 km in different colours. Red coloured clouds are the highest, green and blue are below. Carbon dioxide and monoxide areas are absorbing infrared signatures.]]
Venusian clouds are thick and are composed mainly (75–96%) of sulfuric acid droplets.<ref>{{cite web|last1=Wilson|first1=C.F.|title=Beyond sulphuric acid – what else is in the clouds of Venus?|url=https://www.hou.usra.edu/meetings/venus2014/pdf/6005.pdf|website=Venus Exploration Targets Workshop ( 2014 )|access-date=21 September 2017}}</ref>  These clouds obscure the surface of Venus from optical imaging, and reflect about 75%<ref name=stub1>This is the spherical albedo. The geometrical albedo is 85%.</ref> of the sunlight that falls on them.<ref name=Basilevsky2003/> 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.<ref name=SolarAirPlane/> The density of the clouds is highly variable with the densest layer at about 48.5&nbsp;km, reaching 0.1 g/m<sup>3</sup> similar to the lower range of [[Cumulonimbus cloud|cumulonimbus storm clouds]] on Earth.<ref>{{cite web |last1=Lee|first1=Yeon Joo |title=Venus Cloud Structure and Radiative Energy Balance of the Mesosphere |url=http://www.mps.mpg.de/phd/theses/venus-cloud-structure-and-radiative-energy-balance-of-the-mesosphere.pdf |pages=14|date=2012}}</ref>

The cloud cover is such that it reflects more than 60% of the solar light Venus receives, leaving the surface with typical light levels of 14,000&nbsp;[[lux]], comparable to that on Earth "in the daytime with overcast clouds".<ref>{{cite journal |title=The Unveiling of Venus: Hot and Stifling |journal=Science News |volume=109 |issue=25 |pages=388–389 |date=1976-06-19 |quote=100 watts per square meter ... 14,000 lux ... corresponds to ... daytime with overcast clouds |jstor=3960800 |doi=10.2307/3960800}}</ref> 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, despite its proximity to the Sun.
[[File:PIA00072 Venus Cloud Patterns - colorized and filtered.jpg|thumb|right|Photograph taken by the uncrewed [[Galileo (spacecraft)|''Galileo'']] space probe en route to [[Jupiter]] in 1990 during a Venus [[Planetary flyby|flyby]]. Smaller-scale cloud features have been emphasized and a bluish hue has been applied to show that it was taken through a violet filter.]]
Sulfuric acid is produced in the upper atmosphere by the Sun's [[photochemistry|photochemical]] action on [[carbon dioxide]], [[sulfur dioxide]], and water vapour.<ref name="European Space Agency ESA">{{cite web |url=http://m.esa.int/Our_Activities/Space_Science/Venus_Express/Acid_clouds_and_lightning |title=VenusExpress: Acid clouds and lightning |work=European Space Agency (ESA) |access-date=2016-09-08 |archive-date=2019-03-28 |archive-url=https://web.archive.org/web/20190328164734/http://m.esa.int/Our_Activities/Space_Science/Venus_Express/Acid_clouds_and_lightning |url-status=dead }}</ref> [[Ultraviolet]] [[photon]]s of wavelengths less than 169 [[nanometer|nm]] can photodissociate [[carbon dioxide]] into [[carbon monoxide]] and monatomic [[oxygen]]. Monatomic 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.<ref>{{cite journal |title=Chemical composition of the atmosphere of Venus |author1=Krasnopolsky, V. A. |author2=Parshev, V. A. |journal=Nature |volume=292 |issue=5824 |pages=610–613 |date=1981 |doi=10.1038/292610a0 |bibcode=1981Natur.292..610K|s2cid=4369293 }}</ref>
:{{nowrap|[[carbon dioxide|CO<sub>2</sub>]] → [[carbon monoxide|CO]] + [[oxygen|O]]}}
:{{nowrap|[[sulfur dioxide|SO<sub>2</sub>]] + [[oxygen|O]] → [[sulfur trioxide|SO<sub>3</sub>]]}}
:{{nowrap|2 [[sulfur trioxide|SO<sub>3</sub>]] + 4 [[water|H<sub>2</sub>O]] → 2 [[sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]] · [[water|H<sub>2</sub>O]]}}

Surface level [[humidity]] is less than 0.1%.<ref name=Koehler>{{cite journal |last=Koehler|first=H. W. |bibcode=1982S&W....21..282K|title=Results of the Venus sondes Venera 13 and 14|journal=Sterne und Weltraum|volume=21|date=1982|pages=282}}</ref> 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]].<ref name=BBC>{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/4335628.stm|title=Planet Venus: Earth's 'evil twin'|work=BBC News|date= 7 November 2005}}</ref> 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.<ref name=gsu>{{cite web |url=http://hyperphysics.phy-astr.gsu.edu/HBASE/Solar/venusenv.html|title=The Environment of Venus|publisher=hyperphysics.phy-astr.gsu.edu|access-date=2014-04-06}}</ref> Besides sulfuric acid, cloud droplets can contain a wide array of sulfate salts, raising pH of droplet to 1.0 in one of scenarios explaining the [[sulfur dioxide]] measurements.<ref>{{citation|arxiv=2101.08582|title=Three Different Ways to Explain the Sulfur Depletion in the Clouds of Venus|year=2021|last1=Rimmer|first1=Paul B.|last2=Jordan|first2=Sean|last3=Constantinou|first3=Tereza|last4=Woitke|first4=Peter|last5=Shorttle|first5=Oliver|last6=Hobbs|first6=Richard|last7=Paschodimas|first7=Alessia}}</ref>

[[File:1518175353-20180113-uvi-20160620-134349-283-l2b-v10-pseudorgb-f840.jpg|thumb|Close-up view of a cloud front encircling Venus' south polar vortex in morning infrared and ultra-violet light]]

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.<ref name=BBCspot>{{cite news |url=http://news.bbc.co.uk/1/hi/sci/tech/8179067.stm|title=Experts puzzled by spot on Venus|work=BBC News|date= 1 August 2009}}</ref>

===Lightning===
The clouds of Venus may be capable of producing [[lightning]],<ref name=Russell2007/> but the debate is ongoing, with volcanic lightning and sprites also under discussion.<ref>[https://www.space.com/venus-missing-lightning.html The Strange Case of Missing Lightning at Venus.]  Meghan Bartels, ''Space''. 26 August 2019.</ref><ref>{{Cite journal|last=Lorenz|first=Ralph D.|date=2018-06-20|title=Lightning detection on Venus: a critical review|journal=Progress in Earth and Planetary Science|language=En|volume=5|issue=1|page=34|doi=10.1186/s40645-018-0181-x|bibcode=2018PEPS....5...34L|issn=2197-4284|doi-access=free}}</ref> The Soviet [[Venera]] 9 and 10 orbiters obtained ambiguous optical and electromagnetic evidence of lightning.<ref name="Phillips">{{cite journal|last1=Russell|first1=C. T.|last2=Phillips|first2=J. L.|date=1990|title=The Ashen Light|url=http://www-ssc.igpp.ucla.edu/personnel/russell/papers/ashen/|journal=[[Advances in Space Research]]|volume=10|issue=5|pages=137–141|bibcode=1990AdSpR..10e.137R|doi=10.1016/0273-1177(90)90174-X|access-date=2016-09-08|archive-date=2015-12-08|archive-url=https://web.archive.org/web/20151208005538/http://www-ssc.igpp.ucla.edu/personnel/russell/papers/ashen/|url-status=dead}}</ref><ref>V. A. Krasnopol'skii, ''Lightning on Venus according to information obtained by the satellites Venera 9 and 10''. Kosmich. Issled. 18, 429-434 (1980).</ref> There have been attempts to observe lightning from the Venera 11, 12, 13, and 14 landers, however no lightning activity was recorded,<ref name=":0">{{Cite journal |last=Russell |first=C.T. |date=1991 |title=Venus lightning |url=http://link.springer.com/10.1007/BF00177140 |journal=Space Science Reviews |language=en |volume=55 |issue=1–4 |page=317 |doi=10.1007/BF00177140 |bibcode=1991SSRv...55..317R |s2cid=189774459 |issn=0038-6308}}</ref> but very low frequency (VLF) waves were detected during descent.<ref name=":1">{{Cite journal |last1=Delitsky |first1=M. L. |last2=Baines |first2=K. H. |date=2015-08-01 |title=Storms on Venus: Lightning-induced chemistry and predicted products |url=https://www.sciencedirect.com/science/article/pii/S0032063314003973 |journal=Planetary and Space Science |series=SI:Exploration of Venus |language=en |volume=113-114 |pages=184–192 |doi=10.1016/j.pss.2014.12.005 |bibcode=2015P&SS..113..184D |issn=0032-0633}}</ref> The [[European Space Agency]]'s ''[[Venus Express]]'' in 2007 detected [[whistler (radio)|whistler waves]] which could be attributed to lightning.<ref>{{cite journal|author=Russell, C. T.|author2=Zhang, T. L.|author3=Delva, M.|author4=Magnes, W.|author5=Strangeway, R. J.|author6=Wei, H. Y.|date=29 November 2007|title=Lightning on Venus inferred from whistler-mode waves in the ionosphere|url=http://aten.igpp.ucla.edu/personnel/russell/papers/lightning_venus_whistler-mode_waves.pdf|journal=Nature|volume=450|issue=7170|pages=661–662|bibcode=2007Natur.450..661R|doi=10.1038/nature05930|pmid=18046401|s2cid=4418778|access-date=8 September 2016|archive-url=https://web.archive.org/web/20160304120534/http://aten.igpp.ucla.edu/personnel/russell/papers/lightning_venus_whistler-mode_waves.pdf|archive-date=4 March 2016|url-status=dead}}</ref> Their [[wikt:intermittent|intermittent]] appearance suggests a pattern associated with weather activity. According to the whistler observations, the lightning rate is at least half of that on Earth<ref name=Russell2007>{{cite journal |last=Russell|first=C.T. |title=Lightning on Venus inferred from whistler-mode waves in the ionosphere |journal=Nature |date=2007 |volume=450 |pages=661–662|doi=10.1038/nature05930 |bibcode=2007Natur.450..661R |pmid=18046401 |issue=7170 |author2=Zhang, T.L. |last3=Delva |first3=M. |last4=Magnes |first4=W.|last5=Strangeway|first5=R. J.|last6=Wei |first6=H. Y.|s2cid=4418778 }}</ref> and may possibly be similar.<ref name=":1" /> However, the Venus Express findings are incompatible with data from the JAXA Akatsuki spacecraft which indicate a very low flash rate.<ref>{{Cite journal|last1=Lorenz|first1=Ralph D.|last2=Imai|first2=Masataka|last3=Takahashi|first3=Yukihiro|last4=Sato|first4=Mitsuteru|last5=Yamazaki|first5=Atsushi|last6=Sato|first6=Takao M.|last7=Imamura|first7=Takeshi|last8=Satoh|first8=Takehiko|last9=Nakamura|first9=Masato|date=2019|title=Constraints on Venus Lightning From Akatsuki's First 3 Years in Orbit|journal=Geophysical Research Letters|language=en|volume=46|issue=14|pages=7955–7961|doi=10.1029/2019GL083311|bibcode=2019GeoRL..46.7955L|issn=1944-8007|doi-access=|s2cid=198423897 }}</ref> Recent work from a Parker Solar Probe flyby indicates that the direction of the whistler waves is towards Venus rather than away, indicating a non-planetary origin.<ref>{{Cite journal |last1=George |first1=H. |last2=Malaspina |first2=D. M. |last3=Goodrich |first3=K. |last4=Ma |first4=Y. |last5=Ramstad |first5=R. |last6=Conner |first6=D. |last7=Bale |first7=S. D. |last8=Curry |first8=S. |date=2023-10-16 |title=Non-Lightning-Generated Whistler Waves in Near-Venus Space |journal=Geophysical Research Letters |language=en |volume=50 |issue=19 |doi=10.1029/2023GL105426 |issn=0094-8276|doi-access=free |bibcode=2023GeoRL..5005426G }}</ref>

The Pioneer Venus Orbiter (PVO) was equipped with an electric field detector specifically to detect lightning and the Venera 13 and 14 missions included a radio receiver and point discharge sensor to search for thunderstorms. Other missions equipped with instruments that could search for lightning included Venera 9 which had a visible spectrometer; Pioneer which had a star sensor; and VEGA which had a photometer.<ref name=":0" />

The mechanism generating lightning on Venus, if present, 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.<ref>{{Cite journal|last1=Michael|first1=Marykutty|last2=Tripathi|first2=Sachchida Nand|last3=Borucki|first3=W. J.|last4=Whitten|first4=R. C.|date=2009-04-17|title=Highly charged cloud particles in the atmosphere of Venus|journal=Journal of Geophysical Research|language=en|volume=114|issue=E4|pages=E04008|doi=10.1029/2008je003258|bibcode=2009JGRE..114.4008M|issn=0148-0227}}</ref>

Lightning could potentially contribute to atmospheric chemistry, through heating which could break apart molecules that contain carbon, oxygen, sulfur, nitrogen, and hydrogen molecules (carbon dioxide, nitrogen gas, sulfuric acid, and water), that will recombine to form new molecules ("carbon oxides", "suboxides", "sulfur oxides", "oxygen", "elemental sulfur", "nitrogen oxides", "sulfuric acid clusters", "polysulfur oxides", "carbon soot", etc.).<ref name=":1" /> Lightning could contribute to the production of carbon monoxide and oxygen gas by converting sulfur and sulfur dioxide into sulfuric acid, and water and sulfuric dioxide to sulfur to sustain clouds. Regardless of how frequent lightning on Venus is, it is important to study as it can be a potential hazard for spacecraft.<ref name=":0" />

Throughout the 1980s, it was thought that the cause of the night-side glow ("[[ashen light]]") on Venus was lightning<ref>{{cite journal |title=Discovery of frequent lightning discharges in clouds on Venus |journal=Nature |date=20 March 1980 |last=Ksanfomaliti |first=L. V. |volume=284 |issue=5753 |pages=244–246 |doi=10.1038/284244a0 |bibcode= 1980Natur.284..244K|s2cid=11234166 }}</ref><ref name=":0" /> however, there may be the possibility that Venus lightning would be too weak to cause it.<ref name=":0" />

==Possibility of life==
{{Main|Life on Venus}}
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|life on Earth]] itself has not yet been shown. Creatures known as [[extremophiles]] exist on Earth, preferring extreme habitats. [[Thermophile]]s and [[hyperthermophile]]s thrive at temperatures reaching above the boiling point of water, [[acidophile (organisms)|acidophiles]] thrive at a [[pH]] level of 3 or below, [[polyextremophile]]s can survive a varied number of extreme conditions, and many other types of extremophiles exist on Earth.<ref name=Cockell1999>{{cite journal |last=Cockell|first=Charles S|title=Life on Venus|journal=Planet. Space Sci.|date=1999|volume=47|issue=12|pages=1487–1501|doi=10.1016/S0032-0633(99)00036-7|bibcode=1999P&SS...47.1487C}}</ref>

The surface temperature of Venus (over 450&nbsp;°C) is far beyond the extremophile range, which extends only tens of degrees beyond 100&nbsp;°C. However, the lower temperature of the cloud tops means that life could plausibly exist there, the same way that bacteria have been found living and reproducing in clouds on Earth.<ref name=Landis2003b>{{cite journal |url=http://gltrs.grc.nasa.gov/reports/2003/TM-2003-212310.pdf |title=Astrobiology: the Case for Venus |last=Landis |first=Geoffrey A. |journal=Journal of the British Interplanetary Society |volume=56 |issue=7/8 |date=2003 |pages=250–254 |bibcode=2003JBIS...56..250L |url-status=dead |archive-url=https://web.archive.org/web/20110807004311/http://gltrs.grc.nasa.gov/reports/2003/TM-2003-212310.pdf |archive-date=August 7, 2011}}</ref> Any such bacteria living in the cloud tops, however, would have to be hyper-acidophilic, 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.<ref name=Cockell1999/>

The Venusian atmosphere has been found to be sufficiently out of equilibrium as to require further investigation.<ref name=Cockell1999/> Analysis of data from the Venera, Pioneer, and Magellan missions has found [[hydrogen sulfide]] (later disputed<ref name=Mogul2020/>) and [[sulfur dioxide]] (SO<sub>2</sub>) 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.<ref name=Landis2003b/> However, the planet's volcanism could explain the presence of carbonyl sulfide.<ref name=Landis2003b/> In addition, one of the early Venera probes detected large amounts of toxic [[chlorine]] just below the Venusian cloud deck.<ref name=Grinspoon1998>{{cite book |title=Venus Revealed: A New Look Below the Clouds of Our Mysterious Twin Planet |first=David |last=Grinspoon |isbn=978-0-201-32839-4 |date=1998 |publisher=Addison-Wesley Pub. |location=Reading, Mass.}}</ref>

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 the "unknown UV absorber" seen as dark patches on UV images of the planet.<ref name=ABC>{{cite news |url=http://www.abc.net.au/news/scitech/2002/09/item20020926135029_1.htm |title=Venus could be a haven for life |work=ABC News |date=2002-09-28 |url-status=dead |archive-url=https://web.archive.org/web/20090814215837/http://www.abc.net.au/news/scitech/2002/09/item20020926135029_1.htm |archive-date=August 14, 2009}}</ref><ref name=Clark>{{cite web |url=https://www.newscientist.com/article/dn2843|title=Acidic clouds of Venus could harbour life|publisher=NewScientist.com|date=2002-09-26}}</ref> The existence of this "unknown UV absorber" prompted [[Carl Sagan]] to publish an article in 1963 proposing the hypothesis of [[microorganism]]s in the upper atmosphere as the agent absorbing the UV light.<ref>[https://astronomy.com/news/2019/08/mysterious-dark-patches-in-venus-clouds-are-affecting-the-weather-there Mysterious dark patches in Venus' clouds are affecting the weather there.] What the dark patches are is still a mystery, though astronomers dating back to Carl Sagan have suggested they could be extraterrestrial microorganisms. Erica Naone, ''Astronomy''. 29 August 2019.</ref> 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,<ref name=Molaverdikhani2012>{{cite journal |last=Molaverdikhani|first=Karan|title=The abundance and vertical distribution of the unknown ultraviolet absorber in the venusian atmosphere from analysis of Venus Monitoring Camera images|journal=Icarus|date=2012|volume=217|issue=2|pages=648–660|doi=10.1016/j.icarus.2011.08.008|bibcode= 2012Icar..217..648M}}</ref> but their composition is still unknown.<ref name=Cockell1999/> In 2016, [[disulfur dioxide]] was identified as a possible candidate for causing the so far unknown UV absorption of the Venusian atmosphere.<ref>{{cite journal |title=Identification of OSSO as a near-UV absorber in the Venusian atmosphere|year=2016|journal=Geophys. Res. Lett.|volume=43|issue=21|pages=11,146|doi=10.1002/2016GL070916|last1=Frandsen|first1=Benjamin N.|last2=Wennberg|first2=Paul O.|last3=Kjaergaard|first3=Henrik G.|bibcode=2016GeoRL..4311146F|url=https://authors.library.caltech.edu/73255/1/Frandsen_et_al-2016-Geophysical_Research_Letters.pdf|doi-access=free}}</ref> The dark patches of "unknown UV absorbers" are prominent enough to influence the weather on Venus.<ref>{{cite news|url=http://www.astronomy.com/news/2019/08/mysterious-dark-patches-in-venus-clouds-are-affecting-the-weather-there|title=Mysterious dark patches in Venus' clouds are affecting the weather there|date=29 August 2019|access-date=29 August 2019}}</ref> In 2021, it was suggested the color of "unknown UV absorber" match that of "red oil" - a known substance comprising a mixed organic carbon compounds dissolved in concentrated sulfuric acid.<ref>{{citation|arxiv=2108.02286|year=2021|title=Organic Carbon Cycle in the Atmosphere of Venus|last1=Spacek|first1=Jan}}</ref>

In September 2020, research studies led by [[Cardiff University]] using the [[James Clerk Maxwell Telescope|James Clerk Maxwell]] and [[Atacama Large Millimeter Array|ALMA]] radio telescopes noted the detection of [[phosphine]] in Venus's atmosphere that was not linked to any known [[Abiotic component|abiotic method]] of production present, or possible under Venusian conditions. It is extremely hard to make, and the chemistry in the Venusian clouds should destroy the molecules before they could accumulate to the observed amounts. The phosphine was detected at heights of at least 48&nbsp;km above the surface of Venus, and was detected primarily at mid-latitudes with none detected at the poles of Venus. Scientists note that the detection itself could be further verified beyond the use of multiple telescopes detecting the same signal, as the phosphine fingerprint described in the study could theoretically be a false signal introduced by the [[telescope]]s or by data processing.<ref name="Nadia Drake">{{cite news |last1=Drake |first1=Nadia |author-link=Nadia Drake |title=Possible sign of life on Venus stirs up heated debate |url=https://www.nationalgeographic.com/science/2020/09/possible-sign-of-life-found-on-venus-phosphine-gas/ |archive-url=https://web.archive.org/web/20200914153820/https://www.nationalgeographic.com/science/2020/09/possible-sign-of-life-found-on-venus-phosphine-gas/ |url-status=dead |archive-date=September 14, 2020 |access-date=14 September 2020 |work=National Geographic |date=14 September 2020}}</ref><ref name="NA-20200914">{{cite journal |author=Greaves, Jane S. |display-authors=et al. |title=Phosphine gas in the cloud decks of Venus |url=https://www.nature.com/articles/s41550-020-1174-4 |date=14 September 2020 |journal=[[Nature Astronomy]] |volume=5 |issue=7 |pages=655–664 |doi=10.1038/s41550-020-1174-4 |arxiv=2009.06593 |bibcode=2021NatAs...5..655G |s2cid=221655755 |access-date=14 September 2020 }}</ref><ref name="NYT-20200914">{{cite news |last1=Stirone |first1=Shannon |last2=Chang |first2=Kenneth |last3=Overbye |first3=Dennis |title=Life on Venus? Astronomers See a Signal in Its Clouds - The detection of a gas in the planet's atmosphere could turn scientists' gaze to a planet long overlooked in the search for extraterrestrial life. |url=https://www.nytimes.com/2020/09/14/science/venus-life-clouds.html |date=14 September 2020 |work=[[The New York Times]] |access-date=14 September 2020 }}</ref><ref>{{Cite web|title=Possible sign of life on Venus stirs up heated debate|url=https://www.msn.com/en-gb/news/technology/possible-sign-of-life-on-venus-stirs-up-heated-debate/ar-BB191n86?ocid=msedgdhp|access-date=2020-09-14|website=www.msn.com|language=en-GB}}</ref> The detection was later suggested to be a false positive<ref name=Thompson2020/> or true signal with much over-estimated amplitude, compatible with 1 ppb concentration of phosphine.<ref name=Greaves202011>{{citation|arxiv=2011.08176|title=Reply to: No evidence of phosphine in the atmosphere of Venus from independent analyses|year=2021|last1=Greaves|first1=Jane S.|last2=Richards|first2=Anita M. S.|last3=Bains|first3=William|last4=Rimmer|first4=Paul B.|last5=Clements|first5=David L.|last6=Seager|first6=Sara|last7=Petkowski|first7=Janusz J.|last8=Sousa-Silva|first8=Clara|last9=Ranjan|first9=Sukrit|last10=Fraser|first10=Helen J.|journal=Nature Astronomy|volume=5|issue=7|pages=636–639|doi=10.1038/s41550-021-01424-x|bibcode=2021NatAs...5..636G|s2cid=233296859}}</ref> The re-analysis of ALMA dataset in April 2021 have recovered the 20 ppb phosphine signal, with signal-to-noise ratio of 5.4,<ref name=Greaves202011/> and by August 2021 it was confirmed the suspected contamination by sulfur dioxide was contributing only 10% to the tentative signal in phosphine spectral line band.<ref>{{citation|arxiv=2108.08393|year=2022|title=Low levels of sulphur dioxide contamination of Venusian phosphine spectra|last1=Greaves|first1=Jane S.|last2=Rimmer|first2=Paul B.|last3=Richards|first3=Anita M. S.|last4=Petkowski|first4=Janusz J.|last5=Bains|first5=William|last6=Ranjan|first6=Sukrit|last7=Seager|first7=Sara|last8=Clements|first8=David L.|author9=Clara Sousa Silva|last10=Fraser|first10=Helen J.|journal=Monthly Notices of the Royal Astronomical Society |volume=514 |issue=2 |pages=2994–3001 |doi=10.1093/mnras/stac1438 |doi-access=free }}</ref>

==Evolution==
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&nbsp;billion years ago,<ref name=Newman>{{cite journal |last=Newman|first=M.J.|author2=Rood, R. T.|title=Implications of solar evolution for the Earth's early atmosphere |journal=Science|volume=198|pages=1035–1037|date=1977|bibcode=1977Sci...198.1035N|doi=10.1126/science.198.4321.1035|pmid=17779689|issue=4321}}</ref> 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 away from Earthlike is not known, but is estimated to have occurred around 4&nbsp;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 gas]]es that followed. Venus's atmosphere has therefore received a great deal of attention from those studying [[climate change]] on Earth.<ref name=Kasting>{{cite journal |last=Kasting|date=1988|title=Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus|journal=Icarus|volume=74|issue=3|pages=472–494 |bibcode=1988Icar...74..472K|doi=10.1016/0019-1035(88)90116-9|first= J.F.|pmid=11538226|url=https://zenodo.org/record/1253896}}</ref><ref name=Sutter>{{cite web|author=Paul M. Sutter|url=https://www.space.com/venus-runaway-greenhouse-effect-earth-next.html|title=How Venus Turned Into Hell, and How the Earth Is Next|publisher=space.com|date=2019|access-date=2019-08-30|author-link=Paul M. Sutter}}</ref>

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 [[history of Earth|formed Earth]] and gave it its water during its early history, possibly from the original rocks that formed the planet or later on from [[comet]]s. The common view among research scientists is that water would have existed for about 600&nbsp;million years on the surface before evaporating, though some such as [[David Grinspoon]] believe that up to 2&nbsp;billion years could also be plausible.<ref name=Bortman>{{cite web |url=http://www.space.com/scienceastronomy/venus_life_040826.html |title=Was Venus Alive? 'The Signs are Probably There'|first=Henry |last=Bortman|work=Astrobiology Magazine|date=2004-08-26|access-date=2008-01-17}}</ref> This longer timescale for the persistence of oceans is also supported by General Circulation Model simulations incorporating the thermal effects of clouds on an evolving Venusian hydrosphere.<ref>M. Way et al. "Was Venus the First Habitable World of Our Solar System?" Geophysical Research Letters, Vol. 43, Issue 16, pp. 8376–8383.</ref>

The early Earth during the [[Hadean]] eon is believed by most scientists to have had a Venus-like atmosphere, with roughly 100 bar of CO<sub>2</sub> and a surface temperature of 230&nbsp;°C, and possibly even sulfuric acid clouds, until about 4.0&nbsp;billion years ago, by which time [[plate tectonics]] were in full force and together with the early water oceans, removed the CO<sub>2</sub> and sulfur from the atmosphere.<ref>{{cite journal |first1=N. H. |last1=Sleep |first2=K. |last2=Zahnle |first3=P. S. |last3=Neuhoff |date=2001 |title=Initiation of clement surface conditions on the earliest Earth |journal=[[Proceedings of the National Academy of Sciences|PNAS]] |volume=98 |issue=7 |pages=3666–3672 |doi=10.1073/pnas.071045698 |bibcode= 2001PNAS...98.3666S |pmid=11259665 |pmc=31109|doi-access=free }}</ref> 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.{{citation needed|date=November 2017}} Its surface is estimated to be about 500&nbsp;million years old, so it would not be expected to show evidence of plate tectonics.<ref name=Nimmo1998>{{cite journal |last=Nimmo|first=F.|author2=McKenzie, D.|title=Volcanism and Tectonics on Venus|journal=Annu. Rev. Earth Planet. Sci.|date=1998|volume=26|pages=23–51|doi=10.1146/annurev.earth.26.1.23|bibcode= 1998AREPS..26...23N}}</ref>

==Observations and measurement from Earth==
{{Main|Transit of Venus}}
[[File:Venustransit 2004-06-08 07-44.jpg|thumb|left|Venus transits the face of the Sun on June 8, 2004, providing valuable information on the upper atmosphere through [[Astronomical spectroscopy|spectroscopic]] measurements from Earth]]
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.<ref name=Marov2004>{{cite journal |bibcode=2005tvnv.conf..209M|journal=Proceedings of the International Astronomical Union|title=Mikhail Lomonosov and the discovery of the atmosphere of Venus during the 1761 transit|volume=2004|issue=IAUC196|pages=209–219|doi=10.1017/S1743921305001390|publisher=Cambridge University Press|date=2004|author=Marov, Mikhail Ya.|doi-access=free}}</ref><ref>[https://www.britannica.com/eb/article-9048817/Mikhail-Vasilyevich-Lomonosov Britannica online encyclopedia: Mikhail Vasilyevich Lomonosov]</ref> In 1940, [[Rupert Wildt]] calculated that the amount of CO<sub>2</sub> in the Venusian atmosphere would raise surface temperature above the boiling point for water.<ref name=Weart>Weart, Spencer, ''[http://www.aip.org/history/climate/index.htm The Discovery of Global Warming] {{Webarchive|url=https://web.archive.org/web/20120521121128/http://www.aip.org/history/climate/index.htm |date=2012-05-21 }}'', "[http://www.aip.org/history/climate/index.htm Venus & Mars] {{Webarchive|url=https://web.archive.org/web/20120521121128/http://www.aip.org/history/climate/index.htm |date=2012-05-21 }} ", June 2008</ref> 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.<ref name=Weart/>

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 analyze 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,<ref name=Britt>{{cite web |url=http://www.space.com/scienceastronomy/astronomy/extrasolar_atmosphere_011127-1.html |title=First Detection Made of an Extrasolar Planet's Atmosphere |author=Britt, Robert Roy |publisher=Space.com |date=2001-11-27 |access-date=2008-01-17 |url-status=dead |archive-url=https://web.archive.org/web/20080511202913/http://www.space.com/scienceastronomy/astronomy/extrasolar_atmosphere_011127-1.html |archive-date=May 11, 2008}}</ref> 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&nbsp;km.<ref name=SpaceCOM>{{cite web |url=http://www.space.com/scienceastronomy/venus_science_040607.html |title=Venus' Atmosphere to be Probed During Rare Solar Transit |publisher=Space.com |date=2004-06-07 |access-date=2008-01-17 |url-status=dead |archive-url=https://web.archive.org/web/20060213154524/http://www.space.com/scienceastronomy/venus_science_040607.html |archive-date=February 13, 2006}}</ref> 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 planet]]s. The atmosphere of mostly CO<sub>2</sub>, 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.<ref name=Transit>{{cite web|url=http://www.ucar.edu/news/releases/2004/venus.shtml|title=NCAR Scientist to View Venus's Atmosphere during Transit, Search for Water Vapor on Distant Planet|publisher=National Center for Atmospheric Research and UCAR Office of Programs|date=2004-06-03|access-date=2008-01-17|url-status=dead|archive-url=https://web.archive.org/web/20120305042039/http://www.ucar.edu/news/releases/2004/venus.shtml|archive-date=2012-03-05}}</ref>

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.<ref name=SpaceCOM/><ref name=Transit/>

==Space missions==
{{Main|List of missions to Venus}}

===Recent and current spaceprobes===
[[File:Global view uvi Venus (Akatsuki).jpg|thumb|This image shows Venus in [[ultraviolet]], seen by the [[Akatsuki (probe)|Akatsuki mission]].]]
The ''[[Venus Express]]'' spacecraft formerly in orbit around the planet probed deeper into the atmosphere using [[infrared]] [[imaging spectroscopy]] in the 1–5&nbsp;[[μm]] spectral range.<ref name=Svedhem2007/>

The [[Japan Aerospace Exploration Agency|JAXA]] probe [[Akatsuki (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.<ref>"Venus Climate Orbiter "AKATSUKI" Inserted Into Venus' Orbit" http://global.jaxa.jp/press/2015/12/20151209_akatsuki.html; accessed 2015-12-09</ref> 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).<ref>{{cite web |url=http://global.jaxa.jp/article/special/explore/imamura01_e.html |title=The World's First Planetary Meteorological Satellite: Exploring the Mystery of the Wind on Venus |last=Imamura |first=Takeshi |publisher=[[JAXA]] |access-date=2018-10-18}}</ref><ref>{{cite web |url=https://www.nec.com/en/global/techrep/journal/g11/n01/pdf/110110.pdf |title=Development of the Venus Climate Orbiter PLANET-C (Akatsuki ) |last1=Oshima |first1=Takeshi |last2=Sasaki |first2=Tokuhito |publisher=[[NEC]] |date=2011 |access-date=2018-10-18}}</ref> 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 [[Orbital eccentricity|eccentric]] orbit ([[Apsis|periapsis]] altitude of 400&nbsp;km and [[Apsis|apoapsis]] of 310,000&nbsp;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.<ref name=PlanetC>{{cite web|url=http://www.jaxa.jp/missions/projects/sat/exploration/planet_c/index_e.html|title=Venus Exploration Mission PLANET-C|publisher=Japan Aerospace Exploration Agency|date=2006-05-17|access-date=2008-01-17|archive-date=2006-12-08|archive-url=https://web.archive.org/web/20061208125942/http://www.jaxa.jp/missions/projects/sat/exploration/planet_c/index_e.html|url-status=dead}}</ref>

[[File:Venus In-Situ Explorer.png|thumb|[[Venus In-Situ Explorer]] proposed by NASA's New Frontiers program]]

===Proposed missions===
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.<ref name=NewFrontier>{{cite web|url=http://newfrontiers.nasa.gov/program_plan.html|title=New Frontiers Program&nbsp;– Program Description|publisher=NASA|access-date=2008-01-17|archive-url=https://web.archive.org/web/20080226160348/http://newfrontiers.nasa.gov/program_plan.html|archive-date=26 February 2008|url-status=dead}}</ref>

A craft called the Venus Mobile Explorer has been proposed by the Venus Exploration Analysis Group (VEXAG) to study the composition and [[isotope|isotopic]] measurements of the surface and the atmosphere, for about 90 days. The mission has not been selected for launch.<ref name="Venus Mobile Explorer">{{cite web |url=http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=4569|archive-url=https://web.archive.org/web/20070217191633/http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=4569|url-status=dead|archive-date=2007-02-17|title=Venus Mobile Explorer—Description|publisher=NASA|access-date=2008-12-23}}</ref>

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 afterward, however, and many of these involve the little-known upper atmosphere. The [[USSR|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.<ref name=Myers>{{cite news |url=http://www.gaerospace.com/press-releases/pdfs/Robotic_balloon.pdf|title=Robotic Balloon Probe Could Pierce Venus's Deadly Clouds|first=Robert|last= Myers|publisher= SPACE.com|date=2002-11-13|access-date=2011-03-23}}</ref>

A solar flyer has also been proposed by [[Geoffrey A. Landis]] in place of a balloon,<ref name=Landis2002/> 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&nbsp;km has an upward solar intensity of 90%, meaning that [[solar panel]]s on both the top and the bottom of a craft could be used with nearly equal efficiency.<ref name=SolarAirPlane>{{cite journal |bibcode=2001AIPC..552...16L|title=Exploring Venus by Solar Airplane|first=Geoffrey A.|last=Landis|publisher=American Institute of Physics|date=2001|journal=AIP Conference Proceedings|volume=522|pages=16–18|doi=10.1063/1.1357898|hdl=2060/20020022923|s2cid=129272536 |hdl-access=free}}</ref> 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&nbsp;km and 60&nbsp;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 (rover)|Spirit]] and [[Opportunity (rover)|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,<ref name=Landis2001b>{{cite journal |title=Robotic Exploration of the Surface and Atmosphere of Venus|first=Geoffrey A.|last=Landis|journal=Acta Astronautica|date=2006|doi=10.1016/j.actaastro.2006.04.011|pages=570–579|issue=7|volume=59|bibcode= 2006AcAau..59..570L}}</ref> 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.<ref name=Marks>{{cite web |url=https://www.newscientist.com/article.ns?id=dn7354|title=To conquer Venus, try a plane with a brain|author=Marks, Paul |publisher=NewScientist.com|date=2005-05-08|access-date=2008-01-17 |archive-url= https://web.archive.org/web/20080102092724/http://www.newscientist.com/article.ns?id=dn7354 |archive-date= 2 January 2008 |url-status= live}}</ref>

[[Roscosmos#Scientific programs|Russian space science plans]] include the launch of the [[Venera-D]] (Venus-D) probe in 2029.<ref>{{cite web |last=Zak |first=Anatoly |url=http://www.russianspaceweb.com/venera-d-2021.html |title=New promise for the Venera-D project |work=RussianSpaceWeb |date=5 March 2021 |access-date=7 March 2021}}</ref> 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.<ref name=VenusD2>{{cite web|url=http://venera-d.cosmos.ru/index.php?id=676&L=2|title=Scientific goals of the Venera-D mission|publisher=[[Russian Space Research Institute]]|access-date=2012-02-22|archive-date=2013-05-10|archive-url=https://web.archive.org/web/20130510180045/http://venera-d.cosmos.ru/index.php?id=676&L=2|url-status=dead}}</ref> It has been proposed to fly together with Venera-D an inflatable aircraft designed by Northrop Grumman, called [[Venus Atmospheric Maneuverable Platform]] (VAMP).<ref name=Scalable>[https://www.hou.usra.edu/meetings/vexag2017/pdf/8029.pdf Venus Atmospheric Maneuverable Platform (VAMP) – Future Work and Scaling for a Mission]. (PDF). S. Warwick, F. Ross, D. Sokol.  15th Meeting of the Venus Exploration Analysis Group (VEXAG) 2017.</ref><ref>[http://earthsky.org/space/new-study-ponders-possible-life-adrift-in-venus-clouds Astronomers ponder possible life adrift in Venus' clouds].  Deborah Byrd, ''Earth & Sky''. 31 March 2018.</ref><ref>[https://www.inquisitr.com/4850106/scientists-explore-the-possibility-of-life-hidden-inside-the-clouds-of-venus/ Scientists Explore The Possibility Of Life Hidden Inside The Clouds Of Venus]. Kritine Moore, ''The Inquisitr''. 1 April 2018.</ref>

The [[High Altitude Venus Operational Concept (HAVOC)]] is a NASA concept for a crewed 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 (spacecraft)|VERITAS]], [[Venus Origins Explorer]], [[Venus In Situ Atmospheric and Geochemical Explorer|VISAGE]], and [[Venus In situ Composition Investigations|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.<ref>[https://www.space.com/41033-venus-atmosphere-aircraft-nasa-contract.html A Venus Aircraft Could Be in NASA's Plans].  Leonard David, ''Space''. 29 June 2018.</ref>

[[File:DAVINCI Venus mission descent.jpg|thumb|Artist's concept of the planned [[DAVINCI+]] probe's descent stages through Venus' atmosphere]]

In June 2021, NASA selected the [[DAVINCI+]] mission to send an atmospheric probe to Venus in the late 2020s. DAVINCI+ will measure the composition of Venus' atmosphere to understand how it formed and evolved, as well as determine whether the planet ever had an ocean. The mission consists of a descent sphere that will plunge through the planet's thick atmosphere, measuring noble gases and other elements to understand Venus' climate change. This will be the first U.S.-led mission to Venus' atmosphere since 1978.<ref>{{cite web|last=Potter|first=Sean|title=NASA Selects 2 Missions to Study "Lost Habitable" World of Venus |url=https://www.nasa.gov/press-release/nasa-selects-2-missions-to-study-lost-habitable-world-of-venus|publisher=NASA|date=2 June 2021|access-date=2021-06-02}}{{PD-notice}}</ref>

== See also ==
* [[Aerospace architecture]]

==References==
{{Reflist}}

==External links==
{{Commons category-inline|Atmosphere of Venus}}

{{Atmospheres}}
{{Venus}}
{{Extraterrestrial life}}
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[[Category:Planetary atmospheres of the Solar System|Venus]]
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