Classification of planets.

• The eight planets have been divided into two groups. All the planets of a particular group have some common features. ‘terrestrial planet’ or ‘rocky planet’ and ‘jovian planets’ or ‘gaseous planets’ (Gas Giants) are the two group of planets.

• The four planets nearest to the sun – mercury, Venus, earth and mars are called the terrestrial planet, because their structure similar to the earth.
• Other four planets- Jupiter, Saturn, Uranus, Neptune are called jovian planets.

• Planets are classified into the following two groups inner and outer planets. These are separated by asteroid belt.
• Inner planets

1. They are made up of dense metallic minerals.
2. They move faster and have a shorter period of revolution.
3. They have thin, rocky crust.
4. They have a mantle rich in iron and magnesium.
5. They have a core of molten metals.
6. They have thin atmosphere.
7. They have very few natural satellites (or moons) or no satellite.

• Outer planets

1. They are made up of hot gases, mainly hydrogen and helium.
2. They move rather slowly and have a longer period of revolution.
3. They are all gaseous bodies.
4. Made of gases.
5. They have ring system around them.
6. They have a large number of natural satellites (or moons).