Earth’s Atmosphere Is Made Up Of A Variety Of Gases

The atmosphere of earth, commonly referred to as air, is the thin band layer of gases that is retained by the gravitational force surrounding the planet. By mole fraction, the atmosphere consists of a mixture of gases, primarily nitrogen (78.08%) and oxygen (20.95%). Other gases present in the atmosphere include argon (0.93%), carbon dioxide (0.04%), methane (0.0002%), etc. apart from gases, the atmosphere of the earth also comprises water vapour, on average around 1% at sea level, and 0.4% over the entire air. 

What are the different layers of the atmosphere?

When talking about different layers of the atmosphere of earth, there are five major and several secondary layers. Mentioned in ascending order, the major five layers of the earth’s atmosphere are troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

• Troposphere: 

From the surface of the earth, the troposphere layer extends to, on an average, about 12 kilometres in height. The height of the troposphere is lower at the poles of the earth and higher at the equator. It is the main layer of the earth’s atmosphere holding all the air organisms need to breathe and plants need for photosynthesis. In addition to this, the troposphere also consists of 99% of all water vapour and aerosols. Now that most of the heat found in this particular layer of atmosphere is generated by the transfer of energy from the surface of the earth, the temperature typically falls when going higher. 

• Stratosphere: 

The stratosphere is the second layer of the atmosphere of earth and is located between approximately 12 and 50 kilometres, above the surface of the earth. This particular layer is home to the earth’s ozone layer which is effective in protecting the earth’s surface from harmful ultraviolet rays coming from the Sun. The higher up one goes to the stratosphere, the more the temperature increases and the warmer the surrounding gets. This layer in the atmosphere is nearly cloud-and-weather-free. In addition to this, this layer is considered the highest part of the atmosphere that jet planes can reach. 

• Mesosphere: 

Located between 50 and 8- kilometres above the surface of the earth, the average temperature in the mesosphere is around minus 85 degrees Celsius. With this temperature, it can be said that this particular layer gets progressively colder with the altitude. In fact, the top of the mesosphere is found to be the coldest place in the entire system of the planet earth. The very scarce water vapours that are present at the top of the mesosphere are responsible for forming the noctilucent clouds. These are the highest formed clouds in the atmosphere of earth which an individual can see with naked eyes only under specific conditions and times of the day. 

• Thermosphere: 

The thermosphere is present above the mesosphere and is located between approximately 80 and 700 kilometres above the surface of the earth. It is the lower part of the thermosphere that contains the ionosphere. Due to the very low density of molecules found in this layer, the temperature in the thermosphere increases with altitude. There are no clouds and water vapour present in this layer of atmosphere. Sometimes, scientists can see aurora borealis and aurora australis in this layer. 

• Exosphere: 

Present above the thermosphere and located between 700 kilometres and 10,000 kilometres above the surface of the earth, the exosphere is the highest layer of the earth’s atmosphere. The tops of this layer merge with the solar wind. The molecules present in the exosphere are very low in density. Therefore, it can be said that this particular layer does not behave like a gas, and particles found in this layer escape into space. Although there is no weather in this layer, the aurora borealis and aurora australis can be sometimes seen by scientists in the lowest part of the exosphere. Most satellites of earth revolve around this layer.

Why is the atmosphere essential for life?

If you are thinking about why the atmosphere is essential for life, let us inform you that the atmosphere acts like the blanket of gases surrounding the planet Earth. Following mentioned are the points describing the importance of atmosphere for life:

• Oxygen, which is an essential gas for the survival of all living organisms, is found in the atmosphere.
• Water apart from oxygen, the atmosphere also consists of other gases like nitrogen, carbon dioxide, etc that are required by plants and animals for different life processes.
• Carbon dioxide is an important gas used by plants to complete the process of photosynthesis.
• The ozone layer, found in the stratosphere protects the earth’s surface from harmful ultraviolet rays coming from the Sun.

Conclusion

The atmosphere of earth is considered as a thin band layer that consists of different gases and water vapours. There are five main layers and multiple secondary layers in the earth’s atmosphere- troposphere, stratosphere, thermosphere, mesosphere, and exosphere. The atmosphere acts as the blanket for the earth’s surface which protects the earth from harmful UV rays, controls and maintains the appropriate temperature, and provides access to the gases important for the survival of all species.