Why is Venus hotter than Mercury? Understanding the solar system


The sun and the objects that orbit it make up the solar system. Among these objects, the planets are well known and have been the subject of research for a very long time.

Scientific research has given rise to many theories and experiments. From this research, scientists have come to various conclusions.

This helps us better understand these bodies that orbit the sun. Among these planets, there are Venus and Mercury.

Venus is the second closest to the sun in our solar system. On the other hand, Mercury is the smallest of all the planets and it is the closest to the sun.

Following several mathematical calculations and experiments in physics, it has been established that Mercury is only slightly larger than the moon.

The sun could appear three times its size compared to what it looks like on planet Earth. Venus is the brightest object outside of the moon at night.

This article is about the temperature of the planets Venus and Mercury. It will also touch another planet in the solar system to help you understand it better. So let’s come back to the question.

Why is Venus hotter than Mercury?

Venus is hotter than Mercury because the atmosphere of Venus is denser than that of Mercury. Mercury has almost no atmosphere, while the atmosphere of Venus is thicker.

The sun’s heat will quickly be returned to space in the case of Mercury; however, Venus will tend to trap heat, resulting in very high temperatures on its surface.

The solar system

The term “solar system” describes the planetary system that has our beautiful planet Earth Earth. According to the National Aeronautics and Space Administration (NASA), there are several planetary systems with planets orbiting a host star.

It is known as the solar system because of the sun, the host star, known as “solis” in Latin. Everything that relates to the sun is then called solar.

Some bodies are linked by the sun due to its gravitational pull. These masses in our solar system include planets, dwarf planets, dozens of moons, many comets, meteorites, and asteroids.

The planets that revolve around the sun are Saturn, Earth, Uranus, Mercury, Venus, Neptune, Mars and Jupiter. A familiar dwarf planet is Pluto.

The known moons that exist in the solar system are over 200. Mercury and Venus are the first two planets near the sun. These are the only planets of the eight without moon.

The biggest planets are Saturn and Jupiter. These two planets are known to have many moons. The popular Pluto has five moons, and even the smallest asteroids have moons.

The formation of the solar system is attributed to the “birth” of the sun from a combination of hydrogen atoms to form helium. This releases a very large amount of energy in the process.

Gravity plays its role in crushing clusters of matter into each other. So large bodies were big and gravity played the role of shaping them into spheres. These are the spheres that are now known as planets.

What is the role of the atmosphere in the planets?

Atmosphere comes from the Greek words meaning “vapor, vapor” and “sphere”. It is a layer or layers of gas. These layers envelop a planet.

These are gases and could diffuse quickly. Yet a planetary body usually has its force of gravity, which would hold back these layers of gas, thus holding back the atmosphere.

The atmosphere plays a crucial role in determining the temperatures and surface characteristics of substances present in a planetary body.

To understand the role of the atmosphere on planetary bodies, their composition and structure, we take a look at the Earth’s atmosphere before discussing the atmospheres of Mercury and Venus.


Earth’s atmosphere is made up of layers of gases. Extensive studies have been carried out on the Earth’s atmosphere. The results show that planet Earth has five different layers, each with different characteristics.

The Earth’s atmosphere consists of 78% nitrogen, 21% oxygen, and small percentages of argon and other gases.

About fifteen kilometers from the surface of the Earth, we have the first layer, which is known as the troposphere.

Most of the substance that makes up the entire mass of the atmosphere is found in the troposphere.

Dust, water vapor, and ash particles are believed to be mostly found in this layer, explaining why most clouds are found. The other layers include the stratosphere, mesosphere, thermosphere, and exosphere.


The planet Mercury is closest to the sun. It has no atmosphere but instead has a fine exosphere.

An exosphere is almost equivalent to an atmosphere. However, its density is so low that the molecules that are gravitationally bound to the body – in this case.

Mercury is essentially collisionless. The exosphere of Mercury is made up of oxygen, sodium, hydrogen, helium and potassium.


Venus is the closest planet to Earth and is similar in size and density to Earth. He has been labeled as the Earth twin. Venus has a thick, toxic atmosphere.

Indeed, the gaseous carbon dioxide is perpetually enveloped in thick clouds of somewhat yellow sulfuric acid.

This greatly affects the air pressure at the surface. Scientists describe it as “overwhelming” because it is estimated to be over ninety times that of Earth. This type of pressure is similar to that found a mile under the ocean on Earth.

The envelopment of planetary bodies by these layers of gas exerts a force on the surface. This force is known as atmospheric pressure and differs from one planetary body to another.

Atmospheric pressure depends entirely on the thickness and density of the atmosphere and the molecular substances that make up the gases present in these atmospheres.


Temperature is the degree of heat or cold of a body. The planets revolve around the sun, which is the main source of heat.

The presence of thermal energy would therefore lead to an increase in the temperature of a given body. The solar system has its temperatures.

Studying planetary bodies within the solar system helps researchers obtain the average temperatures of the planets.

The average temperatures of these eight planets and the dwarf planet, Pluto, in degrees Fahrenheit in their order of proximity to the sun are as follows;

  • 800
  • 900
  • 60
  • -80
  • -238
  • -285
  • -353
  • -373
  • -387

The temperature always drops from one planetary body to another as the distance from the sun increases. Only Venus is an exception because of its extremely dense atmosphere.

Greenhouse effect

After understanding the role, structure and composition of the atmosphere and the relative surface temperatures of planetary bodies, let’s take a look at the greenhouse effect.

The greenhouse effect intervenes to help understand the correlation of the two parameters and how this relationship affects the planets. The greenhouse effect determines the flow of energy in and out of planetary bodies.

Thermal energy from the sun radiates off the surface of the planets. The planets then release energy into space; however, certain atmospheric gases trap this outgoing heat.

It is a natural phenomenon that has helped planet Earth welcome life. Without it, the average temperatures on Earth will be thirty degrees lower than the current fifteen degrees Celsius.

Greenhouse gases enhance the greenhouse effect. Some of these gases are water vapor, carbon dioxide, and many more.


On planet Earth, the burning of fossil fuels and deforestation have resulted in an increase in greenhouse gases in the atmosphere.

This causes drastic changes in the climate due to the increase in the amount of thermal energy trapped in the atmosphere.

Most thermal energy can no longer escape into space, and surface temperatures have increased over the past century. Icebergs are melting and the water level in the oceans continues to rise.


The atmosphere of Venus is thick and consists mainly of carbon dioxide. This major component of the Venusian atmosphere is a greenhouse gas.

This means that the greenhouse effect is robust in Venus. Due to its proximity to the sun, it receives more thermal energy.

Yet, it fails to return most of this energy to space, because the high concentration of carbon dioxide in its atmosphere retains thermal energy.

The greenhouse effect on the planet Venus makes it the hottest world, hotter than Mercury, closest to the sun.


The planet Mercury is the smallest and closest to the sun. Due to its location in the solar system, it makes sense for anyone to consider it the hottest planet.

However, Mercury has an almost nonexistent atmosphere. The molecular components of the atmosphere surrounding Mercury do not exhibit the characteristics of greenhouse gases.

As a result, the unusually high thermal energy that reaches Mercury’s surface from the sun is quickly radiated out to space with almost no heat trapped in its atmosphere.

The Venusian atmosphere, which is mostly carbon dioxide, traps heat that radiates to space from the surface while allowing heat from the sun. This causes very high temperatures on the surface of the planet Venus.

The proximity factor could easily have made Mercury warmer than Venus, but the atmosphere and its contents had a say in determining the surface temperatures of these two planets.

In conclusion, Venus is warmer than Mercury due to the role of the atmosphere in retaining the heat returned to space by the planetary bodies of the solar system.

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