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Bob the Alien's Tour of the Solar System
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Venus' Poisonous Atmosphere

Venus may be the planet closest to Earth and the brightest object in the sky after the Sun and the Moon and has been observed for thousands of years, but it is only in the last twenty years that we have been able to discover what the planet's surface is like. We didn't know whether Venus was a planet covered with craters like Mercury, Mars and the Moon, whether it had hills, mountains, valleys or volcanoes, or showed any signs of life existing on its surface. This is because Venus is totally covered by a heavy cloudy shield, as shown in the picture below.


The swirling clouds look peaceful, but they are definitely not! The planet receives heat from the Sun, but, because of its thick cloud cover, the heat is trapped under the cloud, unable to escape back into space as it does on Earth. This is similar to how a greenhouse works on Earth. Temperatures can reach up to 600c. It is because of this reason that Venus is the hottest planet in the Solar System, even though it is not the closest planet to the Sun.

Diagram showing greenhouse effect on Venus

The cloud that covers Venus is not like the cloud in the skies on Earth. It is full of deadly sulphuric acids droplets, not water droplets as on Earth. Nearly all of Venus' atmosphere is made up of carbon dioxide, a poisonous, suffocating gas which would kill any living creature if it was breathed in. Earth's atmosphere is made up of nitrogen and oxygen. Since the 1970s, missions to Venus have set out to discover what lies under its mysterious and deadly cloudy cover, the most successful being the Magellan radar mapping mission from 1990 to 1994 which has allowed us to put together maps of Venus' landscape. If you want to find out about Venus' surface, click here.