|Diameter||12164 km, 0.95 x Earth's|
|Mean Density||5.24 g/cm3|
|Mean Distance from Sun||108 x 106km = 0.723AU|
|Eccentricity of Orbit||0.007|
|Inclination of Equator to Orbit||177.36°|
|Inclination of Orbit to Ecliptic||3.4°|
|Colour||White cloud cover.
Surface is brown rock.
|Atmosphere||Carbon dioxide (96.5%)
Clouds: Sulphuric acid
|Length of Day||243 days|
|Length of Year||224.7 days|
|No. of Moons||None|
|Surface Pressure||90 x Earth's|
|Gravity||0.903 x Earth's|
|Escape velocity||10.36 km/s|
Venus is the second planet in our Solar System and is the brightest object in the sky after the Sun and Moon. The apparent magnitude can reach a value of – 4.7. The high albedo is due to the almost continuous layer of clouds that cover the whole surface. These clouds are made of sulphuric acid and intensify the runaway greenhouse effect on the planet. Venus is also highly volcanic, contributing to the high levels of sulphur dioxide in the atmosphere.
The temperature on the surface of Venus is hot enough to melt lead. The greenhouse effect has meant that the planet is hotter than Mercury, even though it is twice as far from the Sun. All of the water has boiled away and there is a large amount of lightning seen in the atmosphere. The pressure on Venus is the same as at 1km beneath the sea on Earth. The incredibly high pressures and temperatures mean that it is very difficult to land a spacecraft on the surface, and the atmosphere is also corrosive to metal. The Soviet Venera probes that landed on Venus lasted for only a few minutes before being destroyed.
The planet has been mapped by radar from space, allowing the creation of 3D computer simulations like the picture on the left. The measurements show a rocky and mountainous surface like the Earth, broken by large, open plains. All of the features on Venus are named after famous women except for the first one found: Maxwell Mountain.
The planet has fewer craters than most of the other terrestrial planets. This is partly because it has a much thicker atmosphere, so more of the incoming meteors burn up before they hit the ground. This cannot account for all of the missing craters, though. The answer may lie in the fact that Venus has no tectonic plates, and therefore no easy vent for volcanic activity. On Earth, volcanoes will tend to erupt along a fault line, but on Venus the theory is that the hot magma gets trapped underground until the pressure becomes so high that a series of huge eruptions occur, releasing so much lava that the entire surface of the planet is covered. Every time this happens it wipes out all traces of impact craters, making it seem like Venus has rarely been hit by meteorites in the past.
Venus has the most circular orbit of all the planets. The rotational axis is inclined at almost 180 degrees to the direction of orbit, so the direction of rotation is retrograde (in the opposite direction to the orbital motion) while all of the other planets, with the possible exception of Uranus, rotate prograde. The slow rotational period of the planet means that a day on Venus lasts longer than a year.
Authors: Carolyn Brinkworth and Claire Thomas
Last updated: July 2001