Venus, named for the mythological goddess of love and beauty is often called Earth's twin planet because its size mass and density so closely match Earth's. Venus is however definitely Earth's evil twin sister. The atmospheric pressure is about 100 times Earth's and surface temperatures are hot enough to melt lead. The clouds are mostly sulphuric acid rather than water.
Clouds on Venus
Three thick layers of clouds veil the surface of Venus. These clouds are not water vapor clouds like clouds on Earth. In fact if all the water in the clouds on Venus were to condense onto the surface it would make a layer of water perhaps only a few inches thick – a far cry from the amount of water in Earth's oceans.
The clouds on Venus are sulfuric acid rather than water. The large amounts of sulfuric acid vapor gives Venus its highly corrosive atmosphere.
Greenhouse Effect and Global Warming on Venus
The atmosphere of Venus is over 95% carbon dioxide. This carbon dioxide produces a runaway greenhouse effect on Venus and very extreme global warming. At about 730 Kelvin degrees, the surface temperature of Venus is hot enough to melt lead.
The fact that excess carbon dioxide produces such a strong greenhouse effect on Venus serves as a good warning about the possibility of carbon dioxide induced global warming on Earth. Earth does however have much less than the 95% carbon dioxide atmosphere that Venus has.
Atmospheric Pressure
In addition to the extremely high temperatures and the acid clouds, Venus has an extremely thick atmosphere. The atmospheric pressure on the surface of Venus is about 90 times the Earth's atmospheric pressure.
The atmosphere of Venus is so thick that it refracts light enough that if there were a strong enough light beam, it would travel in a complete circle around the planet. If it were possible to see about 24,000 miles, someone standing on Venus could, in principle, see the back of his own head. Of course seeing that far and surviving on Venus would not be possible.
The Sun, however, never sets on Venus. When the Sun is below the horizon, even at midnight, this strong refraction bends the sunlight coming from the other side of the planet. A glow will always be visible along the horizon.
Spacecraft on Venus
Spacecraft that land on the planet Mars, such as the Mars Excursion Rovers, can last for years beyond their original missions. This is not the case on Venus. The Russian space program has landed several Venera missions on Venus. They have sent back some data and pictures, but the landers only lasted a short while. Between the corrosive acid, extreme temperatures, and crushing pressures, spacecraft that land on Venus stop working after about an hour.
The goddess of love and beauty is truly a harsh mistress.
Further Reading
Zeilik. Michael. Astronomy: The Evolving Universe, 9th ed. Cambridge, 2002.
Paul A. Heckert - I have a Ph.D. in astrophysics, over 30 years experience teaching physics and astronomy, and over 60 published research articles.
