Mercury and Venus are the two closest planets to the Sun, so it stands to reason that they are also the hottest planets in the solar system. However, even though Mercury is the closest planet to the Sun, it is actually cooler than Venus. Most people find this to be an amazing fact, but the reason for this is actually quite easy to explain. Read on to find out the answer.
The temperature of Mercury and Venus
The temperature of Mercury can reach 700 Kelvin (427° C or 800° F), but it is usually much cooler than that. In fact, during night on Mercury the temperature plummets to 100 Kelvin (-173° C or -279.4 ° F). On the other hand the average temperature on Venus is 735 Kelvin (460 °C) and unlike Mercury this temperature remains constant through the day and night. Even at its hottest, Mercury never reaches the constant temperature of Venus.
Why is Venus hotter than Mercury?
This occurs because of two important factors. The first is that Mercury has no atmosphere to trap heat from the Sun and Venus has the thickest atmosphere of any planet in the solar system (93 times thicker than the atmosphere of Earth). The second factor is the Venus has an atmosphere made up of 96.5% carbon dioxide. Just like on Earth, this gas traps heat from the sun, creating a very large greenhouse effect. It is no wonder that Venus is the hottest planet in the solar system.