The pressure of Venus' atmosphere at the surface
is about the same as the pressure at a depth of 1 km in Earth's
oceans. It consists mostly of carbon dioxide. There are many layers
of clouds several kilometers thick composed of sulfuric acid.
These clouds completely shadow our view of the surface. This dense
atmosphere creates a run-away greenhouse effect that raises Venus'
surface temperature by about 400 degrees to over 740K. Venus'
surface is actually hotter than Mercury's even though it is nearly
twice as far from the Sun.
Most likely, Venus once had large amounts
of water like Earth but it all boiled away and Venus is now quite
dry. The same thing would have happened to Earth had it been just
a little closer to the Sun. First, since the atmosphere is mostly
CO2, Venus has a powerful Greenhouse Effect. In fact, the surface
temperature on Venus is about 880F.
The surface conditions have two effects.
- There is no water on the surface of Venus,
and there is almost no water in the air, either. The clouds
are mostly made of sulfuric acid and are much, much higher than
most clouds on the Earth.
- Due to the high atmospheric pressure,
the winds on Venus are also relatively slow. Thus, neither wind
nor rain can really affect the surface on Venus. As a result,
volcanic traits will look freshly formed for a long time.
