It is estimated that the atmosphere is spread up to a radius of 1600 kms. 

It can be divided into four main layers described as follows :

1. Troposphere: This is the lowermost layer of atmosphere and is closest to the earth. Its average height is 12 km. Most of the clouds, water vapours and dust particles are found in this layer. This is the weather-making layer and favours human life. The temperature decreases in this layer at the rate of 1°C for every 165 metres.

2. Stratosphere: This layer lies next to the troposphere. Its height ranges from 12 to 80 km. The temperatures are very low and fairly constant. It is free from clouds, dust particles and convection currents.

3. Ozonosphere: This is a zone of ozone gas. It absorbs ultraviolet rays of the sun. It has high temperature. It is known as thermosphere also.

4. Ionosphere: This layer extends upto a height of 800 kms. Ozone gas, lone gas electrons and atoms are found in this layer. This layer absorbs ultraviolet rays of the sun and reflects radio waves.

5. Exosphere: This is the uppermost layer of the atmosphere. Its upper height is unknown due to inaccessibility. It is a highly rarefied layer. It is known only to aerospace-ships.