Atmosphere of Venus
 | |
| Carbon dioxide | 96% |
| Nitrogen | 3.5% |
| Carbon monoxide | < 1% |
| Argon | < 1% |
| Sulfur dioxide | < 1% |
| Water vapor | < 1% |
Venus, the second planet from the Sun, has a very different atmosphere from that of Earth. It is both much thicker than that of Earth, and extends to a much higher altitude. Cloud structure in the atmosphere makes the surface impossible to see from outside without observing through radar mapping or other means, and the surface was not imaged until the Magellan probe arrived in 1989. Despite the harsh conditions on the surface, at a 50-kilometre level above the surface of the planet the atmospheric pressure and temperature is nearly the same as that of the Earth, making it the most Earth-like area in the Solar System. Due to the similarity in pressure, temperature and the fact that breathable air 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. [1]
Extent and composition
The probe Venus Express arrived at Venus in April 2006 has recently shown through stellar occultation that the atmospheric haze extends much further up on the night side than the day side. On the day side the cloud deck has a thickness of 20 kilometres and extends up to about 65 kilometres, whereas on the night side the cloud deck reaches 90 kilometres in altitude, continuing even further to 105 kilometres as a more transparent haze. [2]
The atmosphere is composed mainly of carbon dioxide, along with a small amount of nitrogen, and the air pressure compared to Earth at the surface is immense: about 96 times that of the Earth, similar to the pressure found one kilometre below the surface of the ocean. The enormous amount of CO2 in the atmosphere creates a strong greenhouse effect, raising the surface temperature to around 500 °C, hotter than any other planet in the solar system, even that of Mercury in spite of being located further out from the Sun and receiving only 25% of the solar energy that Mercury does. The thick atmosphere also causes there to be little difference in temperature between the day and night side, even though the slow retrograde rotation of the planet causes a single day to be the length of 243 days on Earth.
History
Through studies of the cloud structure and the fact that the Sun has increased in temperature since its creation, it is thought that the atmosphere of Venus billions of years ago was more like that of Earth with liquid water on the surface. The runaway greenhouse effect may have been caused by the evaporation of the surface water and the rise of the levels of greenhouse gases that followed. Venus' atmosphere has held a great deal of attention due to this by those studying climate change on Earth. [3]
Wind
| Height (km) |
Temp. (°C) |
Atmospheric pressure (x Earth) |
|---|---|---|
| 0 | 462 | 92.10 |
| 5 | 424 | 66.65 |
| 10 | 385 | 47.39 |
| 15 | 348 | 33.04 |
| 20 | 306 | 22.52 |
| 25 | 264 | 14.93 |
| 30 | 222 | 9.851 |
| 35 | 180 | 5.917 |
| 40 | 143 | 3.501 |
| 45 | 110 | 1.979 |
| 50 | 75 | 1.066 |
| 55 | 27 | 0.5314 |
| 60 | -10 | 0.2357 |
| 65 | -30 | 0.09765 |
| 70 | -43 | 0.03690 |
| 80 | -76 | 0.004760 |
| 90 | -104 | 0.0003736 |
| 100 | -112 | 0.00002660 |
The wind on Venus varies by altitude. The wind near the surface is very slow, much slower than that on Earth. The winds on the surface move at only a few kilometres per hour, but due to the high density at the surface this is still enough to transport dust and small stones across the surface. [4] In the cloudtops however, the wind speed suddenly picks up, reaching up to 95 m/s at the cloud top level. These high-speed winds circle the planet approximately every four days in a phenomenon known as "super-rotation". [5] As regular convection driven by differential solar heating would only create winds of a few metres per second it is not yet clear what causes the extreme change in wind speeds at varying altitudes. It is hoped that the European Space Agency's probe Venus Express will shed light on this.
Clouds
Clouds above the CO2 layer are thick and are composed of sulfur dioxide and droplets of sulfuric acid. [6] These clouds reflect about 60% of the sunlight that falls on them, which is what obscures the surface of Venus from regular imaging. The reflectivity of the clouds would allow a probe exploring the cloud tops to harness solar energy almost as well from below as above, enabling solar cells to be fitted just about anywhere. In addition to this, the extremely slow rotation of the planet would mean that a flying craft could maneuver itself so as to never experience night.
See also
References
- ^ Colonization of Venus (pdf), Geoffrey A. Landis, Conference on Human Space Exploration, Space Technology & Applications International Forum,Albuquerque NM, Feb. 2-6 2003.
- ^ Flying over the cloudy world – science updates from Venus Express, Venus Today, Wednesday, July 12, 2006.
- ^ Kasting J.F. (1988), Runaway and moist greenhouse atmospheres and the evolution of earth and Venus, Icarus, v. 74, p. 472-494
- ^ Moshkin B.E., Ekonomov A.P., Golovin Iu.M. (1979), Dust on the surface of Venus, Kosmicheskie Issledovaniia (Cosmic Research), v. 17, p. 280-285
- ^ Atmospheric Flight on Venus (pdf) - Geoffrey A. Landis, Anthony Colozza, Christopher M. LaMarre. 40th Aerospace Sciences Meeting & Exhibit, 14-17 January 2002, Reno Nevada.
- ^ Krasnopolsky V.A., Parshev V.A. (1981), Chemical composition of the atmosphere of Venus, Nature, v. 292, p. 610-613