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We know the earth’s atmosphere is a vital element for living. The atmosphere is the layer of invisible gases surrounding the earth. The reason why earth features living beings is because of the atmosphere. The atmosphere covers the entire globe and consists of 99% of nitrogen and oxygen. 1% of the atmosphere is filled with other gases, dust particles and water vapour. In this article, let us know about the last layer of the atmosphere, the exosphere in detail.

Layers of Atmosphere

The atmosphere acts as a barrier to protect the earth from harmful UV (Ultra Violet) rays and lets in moderate sunlight. UV radiations are harmful radiations and are the prime cause of sunburns. There are five layers of the atmosphere; they are:

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere

The troposphere is the lowest layer of the earth’s atmosphere. The stratosphere lies above the troposphere and extends up to a height of 50 km. The layer above the stratosphere is known as the mesosphere. This layer extends 85 kilometres from the Earth’s surface. The mesosphere is the coldest layer in the atmosphere, where the temperature goes down as low as -120 degrees Celsius.

The thickest layer of the atmosphere is the thermosphere. Air density is too low in the thermosphere. The lower thermosphere is called the ionosphere, and this ionosphere features electrically charged particles known as ions. The outermost layer of the atmosphere is the exosphere.

Composition and Features of the Exosphere

The outermost layer of the atmosphere and the layer above the thermosphere is the exosphere. Exosphere is derived from the Greek word, where ‘exo’ means outer or external. The region where the exosphere ends, space begins. The Exosphere gradually merges and fades into the vacuum of space.

Air density in this region is extremely thin as hydrogen is the most commonly found gas in the atmosphere. By nature, hydrogen is the lightest element on the earth. The layer below the exosphere witnesses molecules and atoms of atmospheric gases that constantly collide with each other. Along with hydrogen various gases like carbon dioxide, oxygen, and helium are present in the exosphere.

Turbopause is the fluctuating region between the thermosphere and the exosphere. Exobase is the lowest level of the exosphere. The upper boundary of the exosphere is known as geocorona. This boundary is visible to the satellite images of the earth as the blue light that circles the earth.

Facts About Exosphere

  • Many satellites, including the notable International Space Station (ISS), orbit within the exosphere or below.
  • Exosphere starts at a distance of 311 to 621 miles from the earth’s surface and ends approximately at 6200 miles away from the earth’s surface.
  • Exosphere is considered to be the best region to place the satellite
  • The pressure in the exosphere is created by solar wind storms that compress it.
  • Most gas particles in the exosphere travel in curved paths without colliding with another molecule or atom, eventually arching back into the lower atmosphere due to the gravitational pull.

The video below lets you know about the air and atmosphere

Air and Atmosphere

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Frequently Asked Questions on Exosphere

1. Which is the last layer of the atmosphere?

The exosphere.

2. What is a geocorona?

It is the upper boundary of the exosphere.

3. List the various gases present in the exosphere.

Hydrogen, carbon dioxide, oxygen, and helium.

4. List the five layers of the atmosphere.

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere

5. Which is the lowest layer of the earth’s atmosphere?


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