Back غلاف الزهرة الجوي Arabic Атмасфера Венеры Byelorussian Atmosfera de Venus Catalan Atmosféra Venuše Czech Ατμόσφαιρα της Αφροδίτης Greek Venusa atmosfero Esperanto Atmósfera de Venus Spanish Veenuse atmosfäär Estonian Artizarraren atmosfera Basque جو زهره Persian

Atmosphere of Venus

Atmosphere of Venus
Venus
Cloud structure in Venus's atmosphere
revealed by ultraviolet observations
General information[1]
Height250 km (160 mi)
Average surface pressure93 bar (1,350 psi)
Mass4.8 × 1020 kg
Chemical speciesMolar fraction
Composition[1][2]
Carbon dioxide96.5 %
Nitrogen3.5 %
Sulfur dioxide150 ppm
Argon70 ppm
Water vapor20 ppm
Carbon monoxide17 ppm
Helium12 ppm
Neon7 ppm
Hydrogen chloride0.1–0.6 ppm
Hydrogen fluoride0.001–0.005 ppm

The atmosphere of Venus is the very dense layer of gasses 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.[1] It is much denser and hotter than that of Earth; the temperature at the surface is 740 K (467 °C, 872 °F), and the pressure is 93 bar (1,350 psi), roughly the pressure found 900 m (3,000 ft) under water on Earth. The atmosphere of Venus supports decks of opaque clouds of sulfuric acid that cover the entire planet, making optical Earth-based and orbital observation of the surface impossible. 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.[3] The upper layer of troposphere exhibits a phenomenon of super-rotation, in which the atmosphere circles the planet in just four Earth days, much faster than the planet's sidereal day of 243 days. The winds supporting super-rotation blow at a speed of 100 m/s (≈360 km/h or 220 mph)[3] 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.[4] 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 m/s (≈10 km/h or 6.2 mph) on the surface.[5] Near the poles are anticyclonic structures called polar vortices. Each vortex is double-eyed and shows a characteristic S-shaped pattern of clouds.[6] Above there is an intermediate layer of mesosphere which separates the troposphere from the thermosphere.[3][2] The thermosphere is also characterized by strong circulation, but very different in its nature—the gases heated and partially ionized by sunlight in the sunlit hemisphere migrate to the dark hemisphere where they recombine and downwell.[2]

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.[3] It is speculated that the atmosphere of Venus up to around 4 billion years ago was more like that of the Earth with liquid water on the surface. A runaway greenhouse effect may have been caused by the evaporation of the surface water and subsequent rise of the levels of other greenhouse gases.[7][8]

Despite the harsh conditions on the surface, the atmospheric pressure and temperature at about 50 km to 65 km above the surface of the planet 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 exploration and colonization.[9]

  1. ^ a b c Cite error: The named reference Basilevsky2003 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Bertaux2007 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Svedhem2007 was invoked but never defined (see the help page).
  4. ^ Normile, Dennis (2010). "Mission to probe Venus's curious winds and test solar sail for propulsion". Science. 328 (5979): 677. Bibcode:2010Sci...328..677N. doi:10.1126/science.328.5979.677-a. PMID 20448159.
  5. ^ DK Space Encyclopedia: Atmosphere of Venus p 58.
  6. ^ Cite error: The named reference Piccioni2007 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Kasting was invoked but never defined (see the help page).
  8. ^ "How Hot is Venus?". May 2006.
  9. ^ Landis, Geoffrey A. (2003). "Colonization of Venus". AIP Conf. Proc. 654 (1): 1193–1198. Bibcode:2003AIPC..654.1193L. doi:10.1063/1.1541418. Archived from the original on 2012-07-11.

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