You might be surprised to know that Venus is the hottest planet in the Solar System. The temperature across the entire planet is 735 Kelvin, or 462 degrees Celsius.
That makes it hotter than Mercury, which can dip down to -220 degrees Celsius and get up to 420 degrees C. Venus is nearly twice as far away from the Sun as Mercury, and receives 25% of it’s sunlight.
The temperature on the surface of Venus is the same across the entire planet. It doesn’t matter if it’s day or night, at the poles or at the equator – the temperature is always the same 462 degrees.So why is Venus so hot? Billions of years ago, the atmosphere of Venus was probably very similar to the Earth’s, with liquid water lasting on the surface. But a runaway greenhouse effect evaporated all the water, leaving a thick atmosphere of carbon dioxide. The light from the Sun is trapped by the carbon dioxide atmosphere and keeps the planet so warm.
It’s also believed that Venus once had plate tectonics like we have on Earth. Here on Earth, the plate tectonics help regulate the amount of carbon dioxide in the atmosphere by trapping excess carbon dioxide underneath the surface of the Earth. When the plate tectonics stopped, the carbon cycle stopped as well, and carbon dioxide was able to accumulate in the atmosphere of Venus.
We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.