- What is the atmosphere?
- Characteristics of the atmosphere
- Layers of the atmosphere
- Importance of the atmosphere
We explain what an atmosphere is and what is the importance of the earth's atmosphere. Layers and characteristics of the atmosphere.
What is the atmosphere?
The atmosphere is a homogeneous layer of gases concentrated around a planet o celestial star and held in place by action of the gravity. On some planets, composed mostly of gas, this layer can be particularly dense and deep.
The earth's atmosphere reaches about 10,000 km away from the planet's surface, and harbors in different layers the gases necessary to preserve temperature stable planetary system and allow the development of life. The air currents present in it are closely related to the hydrosphere (the set of Water planetaria), and affect each other reciprocally.
Our atmosphere can be divided into two large regions: homosphere (the lower 100 km) and heterosphere (from 80 km to the outer edge), according to the variety of gases that make up each one, much more varied and homogeneous in the first one, and stratified and differentiated in the second.
The origin and evolution of the atmosphere date from the very beginnings of the planet, in which a thick layer of primordial gases remained around the planet, made up mostly of hydrogen and helium from the Solar system. However, the gradual cooling of the Earth and the much later appearance of life were changing the atmosphere and varying its content until reaching what we know today, through processes such as photosynthesis and chemosynthesis or breathing.
Characteristics of the atmosphere
The Earth's atmosphere is composed of various types of gases, the highest percentage of which mass it accumulates in the first 11 km of height (95% of the air is in its initial layer) and whose total mass is around 5.1 x 1018 kg.
The main gases that make it up (in the homosphere) are nitrogen (78.08%), oxygen (20.94%), water steam (between 1 and 4% at the surface level) and argon (0.93%). However, other gases are present in minor amounts, such as carbon dioxide (0.04%), neon (0.0018%), helium (0.0005%), methane (0.0001%), among others.
For its part, the heterosphere is made up of differentiated layers of molecular nitrogen (80-400 km), atomic oxygen (400-1100 km), helium (1100-3500 km) and hydrogen (3500-10,000 km).
The Pressure and atmospheric temperature decrease with height, so the outer layers are cold and not very dense.
Layers of the atmosphere
The Earth's atmosphere is made up of the following layers:
- Troposphere. The initial layer, in contact with the earth's surface, where the greatest amount of atmospheric gases accumulates. It reaches 6 km in height at the poles and 18 km in the rest of the planet, being the warmest layer of all, despite the fact that in its outer limits the temperature reaches -50 ° C.
- Stratosphere. It ranges from 18 to 50 km high, in various gaseous layers. One of them is the ozonosphere, where solar radiation impacts oxygen, forming molecules of ozone (O3) that constitute the well-known “ozone layer”. This process generates heat, so that the stratosphere registers a considerable increase in temperature down to -3 ° C.
- Mesosphere. The intermediate layer of the atmosphere, between 50 and 80 km high, is the coldest part of the entire atmosphere, reaching -80 ° C.
- Ionosphere or thermosphere. It ranges from 80 to 800 km high and presents a air very thin that allows drastic temperature oscillations depending on the solar intensity: it can register temperatures of 1500 ° C during the day and drop dramatically at night.
- Exosphere. The outer layer of the atmosphere, which ranges from 800 to 10,000 km in height, is relatively undefined, little more than the transit between the atmosphere and outer space. It is there that the lighter elements of the atmosphere, such as helium or hydrogen, escape.
Importance of the atmosphere
The atmosphere plays a vital role in protecting the planet and therefore also life. Its density deflects or attenuates the forms of electromagnetic radiation coming from space, as well as the eventual meteorites and objects that could impact with its surface, most of which dissolves due to the friction with the gases when entering it.
On the other hand, in the stratosphere is the ozone layer (ozonosphere), an accumulation of this gas that prevents direct access of solar radiation to the earth's surface, thus keeping the planet's temperature stable. At the same time, the mass of gases prevents the rapid dispersion of heat into space, in what is called "greenhouse effect”.
Finally, the atmosphere contains the gases essential for life as we know it, and plays a vital role in perpetuating the water cycle from evaporation, condensation and water precipitation.