This is an artist's rendition of a column of clouds on Venus. The temperature of the different layers is shown at the left. Click on image for full size version (183K JPEG) Windows Original

The atmosphere of Venus is very hot and thick. If you were on the surface of the planet, the air above you would be about 90 times heavier than the Earth's atmosphere. This is like what a submarine experiences at 3000 ft below the surface of the Earth's ocean. The atmosphere is composed mainly of carbon dioxide (96%), 3.5% nitrogen, and less than 1% is made up of carbon monoxide, argon, sulfur dioxide, and water vapor.

All this carbon dioxide in the air has produced at strong greenhouse effect, which traps heat in the atmosphere. A small amount of sunlight can penetrate the planet's thick cloud layer (about 2%) without being reflected by the sulfuric acid clouds or absorbed by the atmosphere. Whatever sunlight does make it through heats the surface, and is reemitted in the infrared. But virtually all energy emitted by the planet in the infrared (heat radiation) is absorbed by the carbon dioxide rich air. The result is unusually high surface temperatures of about 460C (860F).

Why should Venus and not the Earth have a hot and thick atmosphere? Some scientists call it the Goldilocks phenomenon.

Measurements made by probes which travelled through the atmosphere have shown that temperature varies no more than a few degrees from the equator to the poles, and that the atmospheric temperature remains nearly constant through the long dark night. Thus there are no significant daily, seasonal, or latitudinal temperature gradients in the atmosphere.