Introduction

Earth is the only planet in the solar system that has a life, this is because of the earth’s unique atmosphere. The evolution of the earth’s atmosphere did not happen suddenly, it takes place through various processes and the present atmosphere has been created.

Life has not yet been found among the other planets in the solar system. There are many natural reasons behind the existence of life on this earth. These factors are the distance of the earth from the sun, rotation of the earth, the revolution of the earth, length of the day, changes of seasons, etc.

In addition to all these factors, there is another factor that has created life on Earth. This is the vast atmosphere above the earth and the various gases present in the atmosphere. One of these gases is oxygen, which is essential for life on Earth.

Other planets have atmospheres, but they are either very cold or very hot. Either the air pressure is too high or too low. But every element in the earth’s atmosphere explains the mystery of the creation of this atmosphere (4) & (1).

What is the Earth’s atmosphere?                                     

The atmosphere is a mixture of different gases around the earth that hold the earth by gravity. The layer of an invisible gas that surrounds the Earth above the Earth’s surface is called the Earth’s atmosphere.

According to G. T. Trewartha, “The Earth’s atmosphere is a gas envelope several hundred miles thick which surrounds the solid and liquid Earth”.

Earth’s atmosphere cannot be seen with the naked eye, only its existence can be felt. Under the influence of the gravitational force of the Earth, this atmosphere rotates with the rotation of the Earth (3) & (2).

Extension of atmosphere

The atmosphere surrounds the land and water of the earth and is a mixture of different gases. It extends vertically from about 10,000 meters above sea level (5).

Characteristic of atmosphere

1. It is the invisible covering that surrounds the earth.

2. This is an essential part of the earth.

3. It protects life on Earth by absorbing ultraviolet rays from the sun through the ozone layer.

4. Suitable air for the survival of terrestrial plants and animals is found only in the earth’s atmosphere.

5. It warms the surface by retaining heat and decreases the night temperature compared to the day.

6. As the altitude increases, the atmosphere becomes thinner.

7. There is no definite boundary between the atmosphere and space. The Karman line, which is 100 km above the earth’s ocean surface, or 1.57% of the earth’s radius, is often used as a boundary between the atmosphere and space (3) & (5).

Elements of atmosphere

The atmosphere is composed of different types of gaseous substances and water vapor. The two main components of the atmosphere are nitrogen and oxygen, which is about 99% of the total. The remaining 1% is other ingredients. Up to 90 km vertically from the earth’s surface, the elements of the atmosphere are almost identical, known as homosphere. The part of the atmosphere above 90 km adjacent to the earth’s surface is called the heterosphere because the ratio of different gases is not the same (4) & (2).

The elements that make up the atmosphere are mainly divided into three parts. Such as

1. Gases element

The gases and elements that make up the atmosphere are

a. Nitrogen

It is an essential element of the atmosphere. Nitrogen gas has the highest predominance in the atmosphere. All animals and plants cannot survive without nitrogen. This element plays an important role in plant growth. It helps to prepare the protein food of the living world.

b. Oxygen

Oxygen is an active gas. This is because it easily forms compounds with other elements. It is essential for the survival of animals. It is used to increase the respiration and energy of animals.

c. Carbon dioxide

Although the amount of carbon dioxide in the atmosphere is limited, its importance is immense. This is because carbon dioxide is an essential element for food production in the process of photosynthesis of plants. It also plays a role in heat absorption and climate control. The amount of carbon dioxide is not the same everywhere on the earth’s surface.

d. Ozone

Ozone is also an important element in the atmosphere. It is made up of three atoms of oxygen. It is important for the living things on earth. This gas absorbs the ultraviolet rays of the sun and makes the earth suitable for living. The ultraviolet rays of the sun can cause harmful cancers.

e. Other gases

Other gases include argon, neon, helium, krypton, xenon, hydrogen, radon, methane, nitrous oxide, etc.

2. Water vapor

This is an important element of the atmosphere that is usually in the lower layers. As the temperature increases or decreases, the water vapor holding capacity of the air also increases or decreases. Molecules of water vapor move in the air similar to nitrogen and oxygen molecules. It causes clouds, rain, snow, dew, fog, storms, etc. which have a special climatic effect on the earth’s surface.

3. Dust

There is very fine dust in the lower part of the atmosphere. These are floats like other gas molecules. Dust particles are usually formed from volcanic rock and ash, coal dust, smoke, etc., and are released into the atmosphere. Atmospheric dust helps water vapor to be converted into water particles (3) & (5).

Layers of the atmosphere

The gaseous coating on the earth’s surface that is under the influence of gravity and is rotating with the earth is called the atmosphere. It is divided into several layers above the surface. As it rises above the surface, the temperature of the atmosphere constantly decreases or increases. Scientists have studied the atmosphere and identified many layers of the atmosphere after the evolution of Earth’s atmosphere.

1. The Troposphere

It is the lowest layer of the atmosphere. The depth of this layer in the polar region is about 8 km and in the equatorial region, it is 18 to 19 km. water vapor and dust at this level mix with turbulent air to form clouds, storms, rain, lightning, etc.

2. The Stratosphere

The second layer of the atmosphere is the stratosphere. It extends up to 50 km. The amount of dust in this layer is very low and clouds are not visible. The upper boundary of the stratosphere is known as stratopause. This layer contains a large amount of ozone gas.

3. The Mesosphere

The next 50 to 80 km wide layer of the stratosphere above the earth’s surface is the mesosphere. This layer protects the earth from meteorites. Meteorites come to this layer and become extinct.

4. The Thermosphere or ionosphere

It is the air layer up to 500 km above the mesosphere. The radio waves sent from the surface are interrupted by various ions in this layer and return to the earth’s surface.

5. The Exosphere

The air layer above 500 km is known as the exosphere. At this layer, the air is so light.

6. The Magnetosphere

This is the last layer in the atmosphere above the exosphere. A magnetic field of protons and electrons is formed around the atmosphere in this layer (4) & (5).

Evolution of Earth’s atmosphere

According to scientists concept, the atmosphere is about 350 million years old. The evolution of the earth’s atmosphere was not created abruptly. The earth has cooled through various evolutions over billions of years since its creation. Gradually an invisible layer of gas has formed over the earth which is the atmosphere (4). The evolution of Earth’s atmosphere is done by following the process

1. The first phase (atmosphere at the beginning of the creation of Earth)

In the first stage of creation, the earth was extremely hot. According to scientists, the Earth’s atmosphere is probably made up of hydrogen and helium. This is because of the dusty gaseous ring around the sun which consists mainly of hydrogen and helium.

Earth is a hot gas ball at the time of creation. Hydrogen and helium gas were as warm as Earth. This caused the molecules of this gas to move very quickly and eventually go into space. This creates a layer on top of the earth called the atmosphere.

2. The second phase (The gradual evolution of the earth’s atmosphere)

There have been more volcanoes on Earth in the past than present day. These volcanoes emit large amounts of water vapor, carbon dioxide, and ammonia. Most of the carbon dioxide from volcanoes dissolves in seawater.

Some bacteria produce oxygen as a by-product of the reaction of sunlight and carbon dioxide. In this way, oxygen is produced and mixed with the atmosphere.

3. The third phase (the present earth’s atmosphere)

Thus most of the carbon dioxide is dissolved in the oceans. Oxygen is produced by the reaction of bacteria with sunlight and carbon dioxide. Oxygen production gradually increases. In this way, the formation of oxygen in the Earth’s atmosphere begins. The presence of this oxygen in the earth’s atmosphere makes the earth capable of transmitting life.

Ammonia molecules are separated by sun rays, leaving nitrogen and hydrogen. Hydrogen is the lightest so it is at the top of the atmosphere. Most of the hydrogen eventually goes into space. This is how the Earth’s atmosphere evolved (3) & (2).

Operin & Haldane theory

The scientist Operin wrote about the origin and evolution of the ancient atmosphere in “The Origin of Life” in 1936. According to Operin & Haldane, when the earth was formed, gaseous substances condensed into a liquid center and formed outer layers according to the density around it. Gases such as helium, hydrogen, oxygen, argon, carbon, and nitrogen floated to form the paleoclimatic atmosphere.

About 3.7 billion years ago, this atmosphere had a reducing atmosphere. It was not possible for hydrogen, oxygen, carbon, and nitrogen to be free in this superheated earth’s atmosphere. These were attached to the metal. The current atmosphere is an atmosphere with oxygen known as oxidizing atmosphere.

Notably, when the primordial earth did not cool or harden, the combined composition of the heated gaseous substances in the atmosphere changed drastically. Oxygen, which is essential for the survival of living things, is thought to have originated much later.

The amount of carbon dioxide was so high that if it were still present, the earth would be so hot that life would be almost impossible. Among the other notable elements of the atmosphere, nitrogen, and water vapor, the amount of water vapor was many times higher than at present (5) & (2).

Importance of atmosphere

Different types of gaseous elements, water vapor, and dust particles are present in different layers of the atmosphere. The importance of the atmosphere is

1. It mainly plays an important role in preserving the life of plants and animals. The ozone in the atmosphere absorbs harmful rays of the sun and sustains the existence of life on Earth.

2. The various gaseous elements in the atmosphere such as oxygen and carbon dioxide help to keep plants and animals alive.

3. Clouds are formed due to water vapor in the atmosphere. This results in rainfall and protects the wildlife.

4. Without the atmosphere, sound waves would not be transmitted anywhere. Because the radio waves sent from the earth get interrupted in the ionosphere and come back to the earth.

5. It is basically a covering that protects the living world from solar energy.

6. The atmosphere contains the ozone layer, which protects the Earth’s ecosystem from meteorites coming from space.

7. Due to the high levels of nitrogen in the atmosphere, the plant produces protein-rich food and the organism receives the required protein from the plant (1) & (3).

Written By: Manisha Bharati

References

1. D.S Lal, Publisher: Sharda Pustak Bhawan, Publishers & Booksellers.

2. Savindra Singh. Pravalika Publication Allahabad. Climatology: Atmosphere Weather Climate. By Siddhartha. Publisher: Kitab Mahal; New edition (1 January 2018).