How does planet Earth sustain life even after receiving Ultraviolet Radiation from the sun? Why is the sky dark even during the daytime in Mercury? Why do some planets have extreme day and night temperatures?

The answer to all questions lies in the thin band of air wrapped around our Earth like a protective blanket, the atmosphere.

The atmosphere on Earth is a mixture of around 78% Nitrogen, 21% oxygen, 0.93% Argon, 0.04% carbon dioxide, and other gases, including water vapour. Our gravity bounds it to the Earth.

The atmosphere extends 10,000 km from the surface to the point at which it blends with the space. It is divided into 5 different layers based on its temperature:

Troposphere
The troposphere is the densest atmospheric layer as it contains approximately 80% of its mass. It extends 12 km-15 km from the surface of the Earth. As this layer has 99% of water vapour, most of the clouds are found here. The word “Tropos” means change and it earns this name because the gases are constantly mixing in this layer, explaining why most of the weather takes place here. It is thicker at the equator and thinner at the poles. Here the temperature decreases with a rise in altitude.

Stratosphere
The second layer lies 50 km from the Earth's surface. The stratosphere is where the Earth's ozone layer lies, shielding us from damaging UV radiation. In this layer, clouds and weather are mostly absent but stratospheric clouds can be formed in the lowest and coldest region. Due to the absorption of the UV rays, the temperature here increases the higher you go, and this is the highest level at which planes and jets can fly.

Mesosphere
Beginning just above the stratosphere and extending 85 km from the Earth's surface, the Mesosphere is where most objects entering the Earth's atmosphere burn up. Though water vapour is scarce, noctilucent clouds can still be formed in this layer. The coldest temperature in the atmosphere is found at the top of this layer, with temperatures averaging at -90°C.

Thermosphere
While it is still a part of the atmosphere, the air density in the thermosphere is low. As the density of the molecules in this layer is low, the temperature increases with a rise in altitude. It extends 700 km from the Earth's surface and contains no water-vapour or clouds, and this is where the International Space Station orbits our planet.

Exosphere
The highest layer of the earth's surface is where the particles escape into space. The Exosphere is between 700-10,000 km from the surface and has a very low density of molecules, which is why this layer doesn't act like a gaseous one. The topmost layer merges with the solar winds emitted by the sun. Even though the weather is absent in this layer, the northern lights are sometimes visible at their lowest parts, where most of the Earth's satellites orbit.

While we are blessed to have an atmosphere which makes it possible for us to sustain life, our contribution to the increase of greenhouse gases has caused a hole in the ozone layer.

We hope the future generation will choose more sustainable options, as negligence will only result in the devastation of life on the only planet known.

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