The atmosphere of Earth. Layers and structure of atmosphere: Mesosphere, Thermosphere, Exosphere.

Earth atmosphere layers

The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth. It is retained by Earth’s gravity and is almost 480-10000 km thick. Earth’s atmosphere is divided into five primary layers: Troposphere, Stratosphere, Mesosphere, Thermosphere and the Exosphere. The atmosphere thins out in each higher layer until the gases diffuse in space. There is no distinct boundary between the atmosphere and space, but an imaginary line100 Km from the surface of earth called the Karman line. It is usually where scientists say atmosphere meets outer space. Earth’s Atmosphere consists of 78%Nitrogen, 21%Oxygen, 1% Argon, CO2 and remaining everything and having a mass of 5*10 power 18 Kg.


The troposphere is the layer closest to Earth’s surface. It is 7-20Km thick. This is where clouds form, where commercial airplane fly, temperature decreases as altitude increases. This layer is where nearly all weather conditions take place. It contains approximately 75% of the atmosphere’s mass and 99% of the total mass of water vapor.


Stratosphere the second layer of Earth’s atmosphere. It starts above the troposphere and ends about 50 km above ground.  About 20% of the atmosphere’s mass is contained in the stratosphere. This layer is free of clouds or has only cloud tops. Temperature increases gradually and Ozone O³ layer is at the top of this layer. The rise of temperature with elevation is a result of the absorption of the Sun’s ultraviolet radiation by the ozone layer. This is in contrast to the troposphere, near the Earth’s surface, where temperature decreases with altitude. The air here is very dry and it is about a thousand times thinner here than it is at sea level. Because of that, this is where jet aircraft and weather balloons fly.


The mesosphere starts at 50 km and stretches to 85 km high. The top of the mesosphere, called the mesopause, is the coldest part of Earth’s atmosphere, with temperatures averaging about minus 90 Celsius. This layer is tough to study. Jet planes and balloons don’t go high enough, and satellites and space shuttles orbit too high. This is the layer where meteors burn up.


The Iono/Thermosphere extends from about 90 km to between 500 and 1,000 km. Temperatures can get up to 1,500 C at this height, but actually feel cold as we know that the temperature is actually how fast the particles move and because this layer is very thin and have less matter and few particles thats why not feel hot. The thermosphere is recognized as part of Earth’s atmosphere, but air density here is so low that most of this layer is what is typically considered as outer space. In fact, this is where the space shuttles flew and where the International Space Station orbits Earth. Radio waves bounce back from Ionosphere, and this is helpful for Skywave propagation. Due to Ionosphere, all world is getting distant Radio TV signals.


The exosphere is the highest layer at 1000 Km. It is much thin and is where the atmosphere merges into outer space. It is comprised of very widely dispersed particles of hydrogen and helium. There is no collision of particles in this layer and no fluid-like properties.

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