Is Mercury the hottest planet in the solar system?

One might expect that Mercury, the closest planet to the Sun, is also the hottest in the entire Solar System.

Going to compare the surface temperatures of the various planets, however, we see that the hottest one is not Mercury, but Venus!

This strange fact can simply be explained through the properties of the two planets. Due to its small size and its proximity to the Sun Mercury is not able to retain an atmosphere around it, which otherwise would be quickly blown away by the solar wind. Consequently, the absence of atmospheric phenomena means that the temperature excursion between day and night on Mercury is very high: in the daytime hemisphere it reaches 420 °C, while in the night one it can touch -180 °C .

Venus, on the other hand, is surrounded by an atmosphere made up of 96.5% carbon dioxide and it is about 90 times denser than Earth's one. The composition and high density therefore create an impressive greenhouse effect, which raises the surface temperature to an impressive 465 °C.

It is therefore for this reason that Venus is the hottest planet in the Solar System, despite being further away from the Sun than Mercury.

Credit: NASA, JPL.

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