Venus is a hellishly hot world. In-fact, it is the hottest planet in the Solar System despite being the second out from the Sun. This is mainly because of Venus' extremely thick atmosphere which is made up of around 96% carbon dioxide (CO₂). The atmosphere is at a pressure of around 90 times that of Earth’s at sea-level. This traps the heat from the Sun and reflects it back to the surface instead of into space. This is known as the "green house" effect.

Hover your mouse over this image to cut away the clouds and see a radar map made by the Magellan space craft.

Venus spins the opposite way to the other planets, possibly because it has flipped upside down. This may be due to drift caused by gravity from the other planets, and the fact that Venus has no moon to stabilise the axis tilt. The atmosphere of Venus is comprised mostly of CO₂ and contains thick clouds of sulphuric acid (H₂SO₄) and, lightning has recently been observed by the Venus Express probe.

This is a computer generated image from the surface of Venus showing the 8 km high volcano. The vertical scale is exaggerated.

The planet has numerous volcanoes, one of which is Maat Mons (see left). Some volcanoes may still be active, although none have been seen erupting. When scientists tried to date the surface of Venus by counting the number of craters in various locations, they found an anomaly. The craters were evenly distributed across the planet, suggesting that the entire surface had been molten at the same time (about 150 million years ago).

Something that has puzzled scientists is the fact that Venus has no magnetic field to speak of. The reason this is odd is because

the planet is of similar size and composition as the Earth, and so one would expect electromagnetic induction to take place within the core. It is now thought that this may be due to Venus' slow rotation which reduces the speed at which molten iron flows in the outer core. Since motion is needed to generate a magnetic field, there is not enough kinetic energy in Venus' core to do this. Another line of thought is that because Venus has no plate tectonics, the volcanoes on Venus do not erupt anywhere near as often as the ones on Earth do. Meaning there is no mechanism for cooling the mantle due to the loss of heat from such volcanoes. So the mantle remains too hot for heat in the core to flow into it. (Heat flows from a hot source to a cold sink.) Work is done i.e. energy released when heat moves in this way. The energy is in the form of electric and magnetic fields. However, the true reason for Venus' nonexistent magnetic field may well be a combination of both factors.

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