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Inner and Outer Planets  

Our solar system consists of total eight planets including earth. All of them orbit the Sun. These planets are divided in to two groups, Inner and Outer planets. These two types are decided on the basis of the planet’s position with respect to the Sun. Mercury, Venus, Mars and Earth are inner planets as they are closest to the Sun and Neptune, Saturn, Jupiter and Uranus are outer planets. Inner planets are also known as terrestrial planets and outer planets are known as gas giants. Mercury is the closest and Neptune is the furthest planet.

Inner Planets: –

  • Mercury: – Mercury is the smallest of the four terrestrial or Inner planets with a diameter of 4,878 km. This planet does not have any moons. Mercury has a thin atmosphere that contains oxygen, hydrogen, helium, sodium and potassium.
  • Venus: – This planet was once considered a twin planet to earth. But later scientists discovered that the surface of this planet has a lead-melting temperature of 480°C. Venus has no moons or rings.
  • Mars: – This planet shows signs of liquid water flowing on its surface in the past. Atmosphere of Mars contains nitrogen, argon and carbon dioxide. This planet has two moons, Phobos and Deimos.
  • Earth: – It is the largest of all the inner planets. The diameter of our planet is 12,756 km. It is the only planet with life. This planet has one moon and does not have any rings. Earth has an atmosphere that contains nitrogen and oxygen.


Outer Planets: –

  • Neptune: – This planet has six rings and 13 confirmed moons. Atmosphere of Neptune is made up of hydrogen, methane and helium. It is smallest of all the out planets.
  • Saturn: – This planet has 7 known rings and 53 known moons. This planet is mostly made up of hydrogen and helium and has an atmosphere that is somewhat similar to Jupiter’s.
  • Jupiter: – It is the largest of all the outer planets. It is visible with the naked eye. This planet has 50 known moons.
  • Uranus: – Uranus has 27 moons and has an atmosphere that is mostly made up of helium, methane and hydrogen.




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Declan, Tobin. " Fun Facts for Kids about Inner and Outer Planets of Solar System ." Easy Science for Kids, Jan 2017. Web. 22 Jan 2017. < >.

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Tobin, Declan. (2017). Fun Facts for Kids about Inner and Outer Planets of Solar System. Easy Science for Kids. Retrieved from

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