Difference Between Outer and Inner Planets

The inner planets are those that are closest to the sun and are separated from the outer ones by the asteroid belt that lies between Mars and Jupiter, the inner planets are Mercury, Venus, Earth and Mars. The outer planets are larger than the inner ones and are Jupiter, Saturn, Uranus and Neptune.

Outer planets

They are the ones that are farthest from the Sun and are located after the asteroid belt. These planets are known as giant planets, since they are larger than the inner planets.

Their atmosphere is very heavy and because they are made up of gas and liquids, they are also known as gas planets. These have orbits farther from the sun, their atmospheres are made of helium and hydrogen, they also have water, ammonia and methane.

Examples of outer planets:

  • Jupiter: It is the closest to the Sun of all the outer planets and is the largest planet in the Solar System, it has a lot of matter that exceeds all the other planets together. It has 17 satellites and rings that are invisible from Earth.
  • Saturn: It is the second largest planet in the entire Solar System, it has rings and more than 25 satellites, highlighting Titan that contains an atmosphere.
  • Uranus: It has a faint blue surface due to the high concentration of methane. It is the only planet that rotates on its side, spinning on its own orbit.
  • Neptune: It is the furthest planet from the Sun, its surface withstands very strong winds and it has 13 satellites, Triton is the largest of them. It also has rings but they are very difficult to notice.

Characteristics of outer planets:

These planets have some common characteristics:

  • They are within the solar system.
  • They do not have a solid surface.
  • They are called giant planets or Jovian planets, a name that comes from Jupiter.
  • Much of the planets discovered outside our Solar System have a composition similar to that of the outer planets.
  • They have high magnetic fields.
  • They are known as the Jovian planets, a name that comes from Jupiter.
  • Its rotation is very fast, Jupiter completes a revolution in less than 10 hours, Saturn does not reach 11 hours, Neptune rotates in 16 hours and Uranus does it in almost 17 hours and a quarter.
  • In their orbits we find rings and satellites.
  • The cores of Neptune and Uranus are made up of primordial ice subjected to great pressure and temperature and in a liquid state.

Fifth outer planet, Phattie

A study done in 2016 created the theory of a fifth gas giant planet that would explain the anomalies originating in the Kuiper Belt objects. There are theories that this planet has an orbit of 10,000 – 20,000 Earth years and a size similar to Earth or Neptune, its orbit is 20 times farther than Neptune’s.

inner planets

They are the ones that are before the asteroid belt, they are small planets created by rocks and have an atmosphere except for Mercury. These planets are called telluric or terrestrial, since they are dense and solid.


Examples of inner planets

  • Mercury: It is the smallest planet and closest to the Sun, it has very high temperatures, so it does not have an atmosphere.
  • Venus: It is located after Mercury, it is the hottest planet, with a surface covered by lava. It has a very thick atmosphere so it cannot be observed directly.
  • Earth: It is the only planet with the essential characteristics to have life. It has an atmosphere composed of nitrogen and oxygen, large amounts of water and climatic variations.
  • Mars: It barely has an atmosphere, so it has no solar radiation and temperature changes of more than 100ºC. On Mars is the highest volcano in the Solar System, Olympus, with more than 25 kilometers high.

Characteristics of the inner planets

The inner planets have a number of similar characteristics:

  • They are small and have a high density, between 3 and 5 g/cm³.
  • They are known as rocky because they are made up of silicates.
  • The rotation on its axis is slow. Mars and Earth complete a revolution in 24 hours, Venus completes it in 243 days and Mercury in 58 days.
  • Its core is composed of stone or rock.
  • The only ones that have an atmosphere are Mars, Venus and Earth.

Difference Between Outer and Inner Planets

The inner planets are rocky and have a compact surface. Gaseous planets have a surface made up of gas and liquid.
The inner planets are small in size. The outer planets are much larger.
The inner planets have a slow rotation. The outer planets have a very fast rotation.
The inner planets do not have many satellites. The outer planets have many satellites and moons.
The core of the inner planets is made of hot rock. The core of the outer planets is made of ice.
The atmosphere of the inner planets is made up of helium and hydrogen or nitrogen and CO2. The atmosphere of the outer planets is made up of helium and hydrogen.

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