The atmosphere is a layer of gases that surrounds a celestial body. In our case, the terrestrial atmosphere that surrounds the surface of planet Earth has an average thickness of 150 kilometers.
The presence of this layer of gases is essential for many physicochemical and biological processes in the biosphere and an important factor in meteorological phenomena.
In our Solar System, there are only eight moons or planets that have an atmosphere worth considering.
The gaseous composition of the Earth's atmosphere, water vapor and various impurities affect the transmission of solar radiation and the retention of heat in the gound.
The blue color of the atmosphere is due to the emission of light by gas molecules. As it increases, the atmosphere gradually becomes thinner, the pressure decreases, and its structure changes.
The composition of the atmosphere
The atmosphere is made up of a mixture of gases, chemicals, and water vapor. The atmosphere can be divided into four layers based on the temperature distribution:
The troposphere or lower layer
The troposphere is the densest layer of air near the Earth's surface. The lower atmosphere is 12 km above sea level. The troposphere is 4/5 of all the air and is the layer where clouds, precipitation, wind and other phenomena appear.
In this layer, the temperature decreases as a function of the height. The temperature drops 0.64 kelvin for every 100 meters of ascent.
Stratosphere
The stratosphere is a layer located at an altitude of up to 80 km above the troposphere and constitutes 20% of the total weight. This is due to the presence of the ozone layer, which strongly absorbs the sun's ultraviolet radiation.
This layer is divided into two parts:
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Lower stratosphere, with a constant temperature
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Upper stratosphere, in which the temperature increases with increasing height.
Mesosphere
The mesosphere is the middle layer of the atmosphere that extends above 50 km. As altitude increases, the temperature in the mesosphere decreases to a minimum of 85 degrees Celsius.
Thermosphere or ionosphere
In this layer, ultraviolet radiation plays a very important role since they are capable of dissociating the oxygen and nitrogen molecules present. The absorption of these radiations causes the temperature in the thermosphere to reach 1,500 degrees Celsius.
What is the atmosphere for?
The earth's atmosphere has a protective function for life. Due to its characteristics, it performs the following functions:
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It absorbs part of the ultraviolet rays that reach the Earth through solar radiation in the ozone layer, which is vital to keep the planet in a stable temperature range.
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The gases that compose it prevent the dispersion of heat causing a greenhouse effect that prevents the planet from freezing.
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It acts as a protective shield against meteorites that come from outer space. These disintegrate by friction with the air.
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It attenuates and reflects the electromagnetic waves that come from outer space.
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They contain oxygen, carbon dioxide and other gases essential for life (respiration, photosynthesis, water vapor, etc.)