Difference Between Inner and Outer Planets

 Inner and outer planets are what our solar system is divided into based on a few differences.

Humans have always been interested in the intergalactic world and have always tried to gather as much information as possible.

Now we know more about the galaxy than we have ever and can easily distinguish between the two types of planets.

Inner vs Outer Planets

The main difference between inner and outer planets is that inner planets are seen much closer to the sun, therefore, having greater solar access while the outer planets are seen much further away from the sun thereby giving them lesser sunlight access and also giving the whole orbital area a colder aura.

Inner vs Outer Planets

Inner planets are the planets present between the sun and the asteroid belt. This closer association with the sun gives the planets a pretty hot or humid planet temperature making some of them not suitable for the survival of organisms. This planet’s temperature determines many other factors in all of the inner planets such as the terrain and the way the planet has been formed.

Outer planets are placed at a much larger distance from the sun and beyond the great asteroid belt. These planets have attained a great drop in temperature due to the distance from the sun. Such a drop in the temperature affects the general aura around the planet creating a huge difference in the planet’s terrain and atmospheric growth.

Comparison Table Between Inner and Outer Planets

Parameters of ComparisonInner PlanetsOuter Planets
Planets In The GalaxyMercury, Venus, Earth, and MarsJupiter, Saturn, Uranus, and Neptune
General CompositionRocksInert gases
Revolutionary PeriodShortLong
Distance From SunVery small in comparisonHigh

What is Inner Planets?

The inner planets in the Milky Way are Mercury, Venus, Earth, and Mars.

Inner planets are all placed in their orbits that are around the sun and are present in the galactic space between the sun and an asteroid belt.

This means that their position in the Milky Way is very close to the sun when compared to most other things in space.

Being this close to the sun gives the planets a great advantage in many cases.

The higher temperature has to lead to the formation of a species inhabitable environment in our planet Earth.

The greater temperature has also helped in creating the different surface type that is unique to each of the four inner planets.

All the inner planets have a rocky terrain accompanied by the gradual formation of a mountain or hill-like structures and valleys.

The major composition of the inner planets is all minerals and inert elements like silver and platinum.

The surface of most of the inner planets is rich in silicone and iron thereby helping scientists come up with certain speculation.

This speculative thinking is that all the inner planets have a core that has iron content in the form of molten iron.

This has given the inner planets another name that is terrestrial planets.

The periods of revolution around the sun are low as they are close to the sun.

The planets tend to have a higher density as the major component in all the planets is rocky in structure.

The orbits that the terrestrial planets revolve around are closed and therefore revolve in a complete elliptical form.

The most fascinating thing about the inner planets is that despite being similar in all the properties, the general environment of each planet is unique.

The surface of each planet along with the atmospheric thickness and composition are all different for the inner planets.

While earth plays host to water, no traces of it have been found in any other inner planet as of now.

The spin of each planet around their axis tends to be slower in their case.

The inner planets possess a very little number of moons with earth having a single moon.

What is Outer Planets?

 The outer planets are Jupiter, Saturn, Uranus, and Neptune.

The position of the outer planets in the galaxy is much beyond the asteroid belt.

Due to their large distance from the sun, the outer planets are pretty cold and the atmospheric temperature is usually below zero.

These planets are mainly composed of inert gases such as helium. This inertness of the gases affects the general environment of these planets.

Some planets are greater in acidic content and can therefore be dangerous for survival if not protected extensively.

The period of revolution of the outer planets tends to be much larger as their distance from the sun is equally big.

The planets are all in general very low in density and their densities can be considered equal to or less than that of water.

Outer planets are also commonly called Jovian planets. This name is concerning one of the major outer planets that is Jupiter.

The orbits of the Jovian planets are all broken and therefore not always do the planets form a proper ellipse while rotating around the sun.

It isn’t normal for all the outer planets to have the same composition as they are all made up of different gases.

The atmosphere is considered strongly magnetic and has a great storm-like center due to the great magnetic fields present in the atmosphere.

The low temperature and the strong gravitational pull of the planets keep the atmosphere intact as it is gaseous.

The planets often experience a stormy hurricane that is termed the Coriolis effect that can be seen from the earth.

The Great Red Spot in Jupiter and the Great Dark Spot in Neptune are two clear examples of the Coriolis effect.

Main Differences Between Inner and Outer Planets

  1. While the inner planets are found between the sun and the asteroid belt, the outer planets are well beyond the asteroid belt and at a greater distance from the sun.
  2. The outer planets have a greater number of moons of varying sizes while the number is small for the inner planets.
  3. The orbits of the outer planets are not a complete ellipse and are broken while the orbits of the inner planets are a complete ellipse and therefore give them a shorter period of revolution.
  4. The general composition of all the inner planets is the same and is rocky while the composition of the outer planets even though it is all gas, the types of gases are varying.
  5. The density of the inner planets is much greater than that of the outer planets.


 All the planets in the galaxy are composed of either gases or rocky terrain-like structures.

Irrespective of whether the planet is inner or outer, they all have to follow a specific orbit around which they have to move.

The difference in densities is all related to the general characterization of the composition of each planet that falls into each category.

Not all planets have mineral composition nor do all have gaseous composition.

Venus and Mercury are too close to the sun to be considered suitable for life.

Other planets in the inner planets category are still under the human radar for any characteristics that may indicate living beings.

Saturn is the only planet as of now that has a density less than that of water.


  1. https://books.google.com/books?hl=en&lr=&id=k6QRAAAAYAAJ&oi=fnd&pg=PA1&dq=inner+planets&ots=GNFUuX8p4G&sig=W-hKfXeHWPuoni1-m6B6nEPUhCg
  2. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/93JE00980
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