The surface temperature on Venus is between 460 and 480 deg C,
making it the hottest planet in the solar system. The high
venusian temperature is due to the dense atmosphere of carbon
dioxide. The atmosphere acts as an insulating blanket: the
average temperature is 500 degrees higher than it would be
without the atmosphere. Solar radiation penetrates Venus's
clouds and its heat becomes trapped because of the properties of
carbon dioxide, a phenomenon known as the greenhouse effect.
In its early history, when the Sun was dimmer than it is now,
Venus would have been cooler with oceans of liquid water. But
over its first million years or so the water evaporated,
contributing to the greenhouse effect, and was finally lost to
space. As the temperature went up, more carbon dioxide was
released from rocks on the surface leading to a 'runaway
greenhouse effect' and the superheated state of Venus today.
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