Venus Fact File
|Mass (Earth masses)||0.82||1|
|Mean density (g/cm³)||5.24||5.52|
|Day (Earth days)||243.02||1|
|Year (Earth days)||224.701||365.25|
|Mean orbital radius (AU)||0.723||1.0|
|Atmospheric pressure (bar)||~100 (at surface)||1|
|Escape velocity (km/s)||10.36||11.18|
The radius quoted is the mean equatorial radius. Due to their rotation, planets such as the Earth are often slightly flattened at the poles. Venus is unusual in that its polar radius is almost the same as its equatorial radius.
The mean density is the average density throughout the entire planet. The surface rocks are generally much less dense than the mean, while the core is made up of large amouts of nickel and iron and is much denser than the average. In geology, this is known as differentiation. See Venus Surface.
Mean orbital radius is often measured in Astronomical Units, or AU. This is the mean Earth-Sun distance and is approximately equal to 150 million km. See Science.
Orbital eccentricity is a measure of how circular a planet's orbit is - the lower the number, the more circular the orbit. Venus has one of the most circular orbits in the solar system.
The atmosphere of Venus is very thick and quite different to that of the Earth. See The Atmosphere.
The escape velocity of Venus is similar to the Earth's. This is a measure of how hard it is to leave the surface due to the downward pull of gravity. Venus and the Earth are similar both in size and mean density so the gravitational force is similar at the surface of both planets. (For comparison, although the Sun has a mean density of only 1.41 g/cm3, its volume is over a million times that of the Earth and so its escape velocity is 617 km/s!)