An atmosphere is a sheet of gases that surround a material body or a planet. It is controlled by the gravity of that body. Argon, oxygen and nitrogen from the three main constitutions of the atmosphere.

Earth’s Atmosphere

About 80% of the mass of earth’s atmosphere is contained below 10 km altitude. The atmosphere of earth is mostly composed of many gases including nitrogen, oxygen, carbon dioxide. This helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays.

Layers of Atmosphere

The earth’s atmosphere is divided into layers based on the temperature field. These layers are:

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Ionosphere
  • Exosphere


It is the undermost layer of the earth’s atmosphere. At the base of the troposphere, the air is warmer. Density and air pressure also decrease with altitude.


It is the 2nd layer of the atmosphere. It occurs at an altitude of fifty kilometres.


It lies beneath troposphere and above the stratosphere. Temperature decreases with the altitude.


It extends to six hundred kilometres high. Aurora and satellites occur in this layer. It starts just above the mesosphere.

The ionosphere

It is an abundant layer composed of ionized atoms, molecules and electrons that expand from about forty-eight kilometres above the surface overlapping into the mesosphere and thermosphere.

The exosphere

It is the upper limit of the earth’s atmosphere. It extends from the top of the thermosphere up to 10,000 km.

Gases in Atmosphere

The atmospheric composition of gas on Earth is largely conducted by the by-products of the life that it nurse.

Dry air from earth’s atmosphere contains 0.038% of carbon dioxide, 20.95% of oxygen, 78.08% of nitrogen and 0.93% of argon.

Traces of hydrogen, neon, helium, nitrous oxide, ozone and other “noble” gases, but generally a variable amount of water vapour is also present, on average about 1% at sea level.