Atmosphere of Earth

Our beautiful earth is the only planet in the solar system which has an atmosphere in which life can exist. The gases in the atmosphere protect us from heat, radiation and dangerous rays from the sun as well as it provides us sufficient air to breath. Our atmosphere contains water vapors  traces of dust particles, pollen, plant grains and many other solid particles.  From the past century, air pollution and many dangerous gases such as greenhouse are destroying our atmosphere. It has severe impact on the atmosphere, they are causing changes like Acid rain, holes in the ozone layer, Global warming etc etc.

Composition: Earth's atmosphere is a think layer of gases. Which are composed of 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and trace amount of other gases. There is no exact place where the atmosphere ends; it just gets thinner and thinner, until it merges with outer space. 

Layers: There are five main layers of Earth’s atmosphere. Which are Troposphere, Stratosphere, Mesosphere, Ionosphere and Exosphere. As mentioned above, there no end to atmosphere but we do have an imaginary line of about 110 Km from the surface and it’s called Karman line. Scientists say that our atmosphere meets outer space at Karman line. Let’s read each layer in brief:

Troposphere: This layer is the closest one to Earth. It is 4 – 12 miles (7 – 20 km) thick and contains almost half of Earth’s atmosphere. We find clouds in this sphere because almost all the dust and water vapors are in this sphere. In the troposphere, the temperature generally decreases as altitude increases.

Stratosphere: It is the second layer and ends about 50 km above ground. This is the layer where jet aircrafts and weather balloons fly. Ozone is abundant here and it heats the atmosphere while also absorbing harmful radiation from the sun. Only the highest clouds (cirrus, cirrostratus, and cirrocumulus) are in the lower stratosphere.

Mesosphere: It starts at 31 miles (50 km) and extends to 53 miles (85 km) high. The top of the mesosphere, called the mesopause, is the coldest part of Earth's atmosphere with temperatures averaging about minus 130 degrees F (minus 90 C). This layer is hard to study. Jets and balloons don't go high enough, and satellites and space shuttles orbit too high. Scientists do know that meteors burn up in this layer.

Thermosphere: It extends from about 56 miles (90 km) to between 310 and 620 miles (500 and 1,000 km). Temperatures can get up to 2,700 degrees F (1,500 C) at this altitude. The thermosphere is considered part of Earth's atmosphere, but air density is so low that most of this layer is what is normally thought of as outer space. In fact, this is where the space shuttles flew and where the International Space Station orbits Earth.

Exosphere: This is the highest layer, is extremely thin and is where the atmosphere merges into outer space. It is composed of very widely dispersed particles of hydrogen and helium.