Venus

Venus is the second planet from the Sun. It is a terrestrial planet, and its size is closest to that of Earth: its diameter is roughly 95 per cent of Earth's, and its mass about 80 per cent. For this reason it is sometimes called 'Earth's sister', though the conditions on its surface are quite different.

As seen from Earth, Venus is the third-brightest object in the sky after the Sun and the Moon. It can only be observed in the early morning or at dusk, because its orbit lies inside Earth's orbit. This led many cultures to give it two names: the morning star and the evening star.

Atmosphere and temperature

Venus has an extremely dense atmosphere composed mainly of carbon dioxide (CO₂), with clouds in the upper layers containing sulfuric acid. Surface pressure reaches roughly 90 times that of Earth's atmosphere. Because of the greenhouse effect of CO₂, the surface temperature remains around 460 degrees Celsius, varying little between night and day or between different locations.

Rotation and orbit

Venus rotates in a direction opposite to that of other planets (retrograde), meaning the Sun rises in the west. Its rotation is slower than its orbit around the Sun: a single day on Venus is longer than a single year on Venus. The planet has no moon.

Surface

The dense atmosphere makes the surface invisible in ordinary light. Maps of the surface have been made using radar from spacecraft, particularly from the Magellan mission in the 1990s. The surface shows extensive volcanic features, mountains, and relatively few impact craters, suggesting that the surface is young compared to the Moon or Mercury.