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Atmosphere Definition

The atmosphere refers to the layers of gases surrounding the planet, like Earth, which help to sustain life on the planet. The atmosphere is composed of a mixture of gases, including nitrogen (78%), oxygen (21%), and small amounts of other gases, such as argon, carbon dioxide, and neon. The atmosphere also contains water vapor, dust particles, and other particles, which vary depending on the location and time of year. An atmosphere and its elements are held in place by the gravity of the respective planetary body.

Atmosphere Definition

Layers of the Atmosphere

When you go outside your house and look up, you see a pure blue ocean-colored sky and a bunch of clouds in the sky, and at night, you will see a white moon and stars. But, the richness of our atmosphere is something more than what you see with the naked eye.

The atmosphere is made up of several layers. It can be divided into several layers based on temperature and pressure changes with altitude. The five layers of the atmosphere result from the difference in temperature that occurs at different altitudes. The Earth's atmosphere is divided into five major levels, as follows: the first one is the exosphere (outermost) and the second one is the thermosphere, the third is the mesosphere, the fourth one is the stratosphere, and the last one is the troposphere. Let us now discuss each (from inner to outer) in brief:


The first layer is the troposphere, which extends from the Earth's surface to about 10 to 12 kilometers (depending on latitude). It is where weather occurs and most of the Earth's air masses are located. Also, this layer is where most of the Earth's atmospheric gases and water vapor are found. The temperature in the troposphere decreases as we go up in the layer, and so does the pressure.


The stratosphere is above the troposphere and extends from about 12 to 50 kilometers. The temperature in the stratosphere increases with increasing altitude. The ozone layer is located in the stratosphere, which protects life on Earth from harmful sun ultraviolet (UV) radiation.


The mesosphere is the layer above the stratosphere and extends from about 50 to 80 kilometers. The temperature in the mesosphere decreases with increasing altitude. This layer is where meteors burn up upon entering the Earth's atmosphere. This layer typically consists of the coldest parts of the atmosphere where the temperature may reach around reach -90C.


The thermosphere is the layer above the mesosphere and extends from about 80 to 700 kilometers. Unlike other layers, the temperature in the thermosphere grows warmer with increasing altitude, and this layer is where the Northern and Southern Lights occur. The increased temperature is caused by the absorption of energetic ultraviolet and X-ray radiation from the sun. Satellites are located in this layer.


The exosphere is the highest or outermost major layer of the atmosphere. It generally serves as the final boundary of Earth's gaseous envelope. It should be noted that there is no real distinction between this layer of Earth's atmosphere and that of outer space. In this layer, air continually but slowly gets leaked from Earth's atmosphere into outer space.

Important Roles of Atmosphere

The atmosphere also plays an important role in regulating the Earth's temperature and protecting the planet from harmful radiation from the sun. The gases in the atmosphere, such as carbon dioxide and methane, trap heat from the sun, which helps to keep the Earth warm. This is known as the greenhouse effect. The Earth would be too cold to support life without the greenhouse effect. However, an intense increase in the levels of greenhouse gases in the atmosphere can lead to global warming and climate change.

The atmosphere also helps to protect the Earth from harmful solar and cosmic radiation. The ozone layer in the stratosphere absorbs most of the harmful UV radiation from the sun, reducing its impact on the planet and allowing life to exist on the surface.

It also plays an important role in the water cycle: water movement between the Earth's surface and the atmosphere. The water cycle helps to regulate the Earth's temperature and provides fresh water for plants and animals. The atmosphere helps to distribute water vapor from the oceans to the land, where it can be used for agriculture and other purposes.

The atmosphere also helps to distribute heat and energy around the planet, which is important for weather and climate patterns. The atmosphere helps disperse heat from the equator to the poles, which helps regulate the Earth's temperature and prevent extreme weather conditions in any location.

Features/ Characteristics of Atmosphere

The atmosphere and outer space have no physical boundaries, and the atmosphere gradually becomes denser and less thick until it "blends" with space.

To prevent genetic damage to life, the atmosphere's stratified structure reduces the destructive effects of sunlight, UV radiation, solar wind, and cosmic rays. After being biochemically altered by living things for billions of years, the paleo atmosphere has become the makeup of the Earth's atmosphere today. Some of the key contributions of the atmosphere are as follows:

  • Helps keep the sun's heat from leaking back into space.
  • Shields life from the sun's damaging radiation.
  • Plays a crucial part in the water cycle on Earth.
  • Contributes to maintaining a mild climate on Earth.

Gases in Atmosphere

The Earth's atmosphere is composed of several gases, the most abundant of which are nitrogen (78%) and oxygen (21%). Other gases present in smaller amounts include argon (0.93%), carbon dioxide (0.04%), neon (0.0018%), methane (0.0002%), and krypton (0.0001%).

Water vapor is also present in the atmosphere, but its concentration varies greatly depending on temperature, humidity, and location. Water vapor typically makes up between 1% and 3% of the atmosphere at any time.

Ozone (O3), a form of oxygen, is also present in the atmosphere, and it is found primarily in the stratosphere in a region known as the Ozone Layer. The ozone layer absorbs harmful ultraviolet (UV) radiation from the sun, preventing causes like skin cancer, cataracts, and other health problems in humans and animals.

Other gases in the atmosphere include trace amounts of hydrogen, nitrogen oxides, sulfur dioxide, and gases produced by natural processes such as volcanic eruptions and biological activity. In addition, gases produced by human activities such as industrial processes and transportation are also trapped in the atmosphere. These gases play crucial roles in the atmosphere and can impact the Earth's climate and air quality.

Planetary Atmosphere

A planetary atmosphere is a layer of gases surrounding a planet that protects it from the harsh conditions of space and regulates the planet's climate. Like the Earth's atmosphere, a planetary atmosphere is composed of a mixture of gases. Its properties, such as temperature, pressure, and composition, can vary greatly depending on the planet's distance from the star, its size, and geological activity.

Planetary atmospheres can be classified into several types based on the composition of their atmospheres. For example:

Terrestrial planets, such as Earth, Venus, and Mars, have atmospheres composed mostly of nitrogen and oxygen, with smaller amounts of carbon dioxide, water vapor, and other gases.

Ice giants, such as Uranus and Neptune, have atmospheres composed mostly of hydrogen and helium, with smaller amounts of methane, ammonia, and water vapor. These atmospheres are much colder than gas giants and contain more water and ice. These atmospheres are much thicker and more massive than terrestrial planets and play a significant role in the planet's internal heat balance.

Rocky exoplanets, or exoplanets similar in size and composition to Earth, may have atmospheres composed of various gases, including nitrogen, oxygen, carbon dioxide, water vapor, and other gases. The presence of life, volcanic activity, and other geological processes can influence the composition of these atmospheres.

In summary, a planet's atmosphere plays a critical role in protecting it from the harsh conditions of space and regulating its climate. The composition and properties of a planetary atmosphere can be used to study the planet's geology, environment, and potential for habitability.


Finally, the atmosphere is a combination of complex and dynamic layers of gases surrounding a planet (such as Earth) that plays a vital role in sustaining life on the planet. The atmosphere helps to regulate the Earth's temperature, protect the planet from harmful radiation, distribute water and heat, and support weather patterns and the water cycle. Understanding the atmosphere and its functions is important for predicting and addressing Earth's climate and environmental changes. The atmosphere is a complex and dynamic system that plays a crucial role in sustaining life on Earth.

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