Our solar system has 8 planets, 4 terrestrial planets, and 4 gas giants. The four gas giants (Jupiter, Saturn, Uranus, and Neptune) because of their large distance from the Sun remain very cold. Mercury is the closest planet to the Sun. Venus which is the second closest planet to the Sun is the hottest planet in the Solar system. Why is Mercury not the hottest planet despite being closest to the Sun? Let’s learn.
Mercury has an average distance of 36 million miles from the Sun. The average temperature on Mercury during the day is 430°C/806°F and during the night is -180°C/-292°F. The day temperature on Mercury although seems extremely high, is not the peak of planet temperatures. Venus which is the second planet from the Sun is the hottest planet in the solar system. The average temperature on Venus is 464°C (867°F).
Why is Venus the hottest planet in the Solar system?
1. Venus is not the closest planet to the Sun but it is still very close. The average distance of Venus from the Sun is 67 million miles.
2. Venus has a very dense atmosphere (atmospheric pressure on Venus is 93 bar). Mercury’s atmosphere on the other hand is very thin (atmospheric pressure on Mercury is 10−12 bar). The atmosphere on Venus is mainly composed of Carbon dioxide and Nitrogen. There are also thick clouds of Sulfuric acid on Venus.
This thick atmosphere traps the heat causing a runaway greenhouse effect, thereby increasing the average temperature on Venus. Because of this runaway greenhouse effect, the temperatures on Venus do not vary much with the time of the day, season, or location.
The average temperature on Solar System planets
| Planet | Average temperature |
|---|---|
| Mercury | 430°C/806°F during the day, -180°C/-292°F during the night |
| Venus | 464°C (867°F) |
| Earth | 15°C (59°F) |
| Mars | -65°C (-85°F) |
| Jupiter | -110°C (-166°F) |
| Saturn | -140°C (-220°F) |
| Uranus | -195°C (-320°F) |
| Neptune | -200°C (-330°F) |
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