Jodrell Bank Observatory - Transit of Venus 2004

VENUS - within this section - Structure | Surface | Atmosphere | Facts & Figures

Venus Fact File

  Venus Earth
Mass (Earth masses) 0.82 1
Radius (km) 6052 6378
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
Orbital eccentricity 0.007 0.017
Atmospheric pressure (bar) ~100 (at surface) 1
Albedo 0.65 0.37
Escape velocity (km/s) 10.36 11.18

The masses of planets are often quoted in units of the Earth's mass which is 6x1024 kg.

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.

Venus has an extremely long day; the Earth rotates on its axis over 240 times in the same time it takes Venus to rotate once.

The Venusian year (time taken taken to orbit the Sun) is only 224 days. By the time you reached the age of 50 on the Earth, your identical twin on Venus would have had 81 birthdays!

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
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.

Albedo is a measure of the reflectivity of a planet. Venus has the highest albedo of all the planets, largely due to the complete cloud cover.

Escape Velocity
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!)