The closer one is to a heat source, the warmer it is. You’d assume that the same rule is followed in our solar system and you’d be right...for the most part. Venus, which is at a distance of about twice that Mercury is from the Sun, is actually hotter than the latter. In fact its temperature is higher at midnight than Mercury’s at noon. This discovery bamboozled scientists for quite some time and understandably so. Let's try to understand why this happens. I promise I’ll try to keep it as simple as possible. Venus is hotter than Mercury despite being farther from the Sun due to its thick atmosphere, primarily composed of greenhouse gases, trapping heat and creating a runaway greenhouse effect. Before I explain, we need to look at a few facts about Venus. · Venus is about twice as far from the sun as Mercury. · Venus is much more reflective than Mercury. · Venus has quite a thick atmosphere while Mercury has none. The first two points are probably what puzzled scientists. Being twice as far from the sun as Mercury, Venus receives 1/4th the solar energy flux that Mercury does. On top of that, Mercury being much less reflective than Venus, also absorbs more(almost 9 times that of Venus) sunlight. Venus's thick atmosphere, primarily composed of carbon dioxide, traps heat through the greenhouse effect, leading to a higher average temperature than Mercury, which lacks a substantial atmosphere for heat retention. This is why Venus(465 •C) is hotter than Mercury(450 •C).
Why is Venus the hottest planet in our solar system while mercury is the closest to the sun?
Why does Venus have higher temperatures than Mercury ?
Now, coming to the third and the most important point - Venus’s atmosphere. Venus has an incredibly thick atmosphere, many times that of Earth’s. And much of that atmosphere is packed with thick layers of highly reflective sulphuric acid clouds. Mercury on the other hand has no atmosphere. Now, all planets receive light energy, absorb some of it, and re-radiate most of it back into space. Earth does this as well. However, if a planet has an atmosphere, varying amounts of that re-radiated light energy is reflected back to the planet again by the atmospheric molecules. This is called the greenhouse effect and is what keeps the Earth’s average surface temperature habitable. Because Mercury has no atmosphere, all of the re-radiated energy escapes into space. On the other hand, Venus, owing to its extremely thick atmosphere, retains much of the re-radiated light energy.
