We can survive on our planet thanks to a layer of varying gas composition that envelops the entire Earth. This layer remains on Earth thanks to gravity. It is the Earth's atmosphere , and its exact thickness is difficult to determine, since the gases that compose it become less dense with altitude, practically disappearing a few hundred kilometers above the surface.
The atmosphere fulfills various functions for life on the planet and if it weren't for it, we would not be able to have life as we know it. Do you want to know everything about the atmosphere?
Composition of the atmosphere
The atmosphere is made up of a mixture of gases, most of which are concentrated in the so-called homosphere, which extends from the ground up to 80-100 kilometers high. In fact, this layer contains 99,9% of the total mass of the atmosphere.
Among the gases that make up the atmosphere, the most important are Nitrogen (N2), Oxygen (O2), Argon (Ar), Carbon Dioxide (CO2), and water vapor. It is important to know that the concentration of these gases varies with altitude, with the variations in water vapor being particularly pronounced, as it is concentrated mainly in the layers near the surface.
The presence of the gases that make up air is essential for the development of life on Earth. On the one hand, O2 and CO2 allow animals and plants to carry out their vital functions, and on the other hand, the presence of water vapor and CO2 allows temperatures on Earth to be suitable for life. Water vapor and CO2, along with other less abundant gases such as methane and ozone, are called greenhouse gases . Solar radiation can easily pass through these gases, but the radiation emitted by the Earth (after being heated by solar energy) is partially absorbed by them, unable to escape into space entirely. Thanks to this greenhouse effect, we can live with a stable temperature. Without these heat-trapping gases that generate this effect, average global temperatures would be below -15 degrees Celsius. Imagine those temperatures almost all year round; life on Earth as we know it would be impossible.
In the atmosphere, the density, composition, and temperature of the air vary with altitude. This means that each layer of the atmosphere has its own characteristics, as can be seen in the structure of the atmosphere and also in this article on the composition of the atmosphere.
Layers of the atmosphere
The atmosphere is divided into several layers based on their composition, density, and temperature. Here is a brief summary of the atmospheric layers.
Troposphere: This is the lowest layer, where life develops and most weather phenomena occur. It extends to an approximate altitude of 10 km at the poles and 18 km at the equator. In the troposphere, the temperature gradually decreases with altitude, reaching -70°C. Its upper boundary is the tropopause.
Stratosphere: In this layer, the temperature increases to approximately -10°C at an altitude of about 50 km. It is in this layer that the highest concentration of ozone is found, the "ozone layer," a gas that, by absorbing some of the Sun's ultraviolet and infrared radiation, makes conditions suitable for life on Earth's surface possible. The top of this layer is called the stratopause.
Mesosphere: In this layer, the temperature decreases again with altitude, reaching -140°C. It extends to an altitude of 80 km, at the end of which lies the mesopause.
Thermosphere: This is the outermost layer, extending to several hundred kilometers in altitude, with temperatures reaching up to 1000°C. Here, the gases have a very low density and are ionized. If you want to learn more about how temperature varies with altitude , you can consult additional resources.
Why is atmosphere important?
Our atmosphere is important for several reasons. More than important, we should say it's essential. Thanks to the atmosphere, life can develop on our planet, as it absorbs much of the sun's ultraviolet radiation in the ozone layer. If a meteorite were to enter Earth's orbit and strike us, the atmosphere would disintegrate it into dust due to the friction it experiences upon contact with the air . Without the atmosphere, the collision speed of these objects would be the sum of their own inertial velocity in space (measured from our planet) plus the acceleration due to Earth's gravity, making it vitally important to have one.
It's also important to mention that Earth's atmosphere hasn't always had the same composition . For millions of years, its composition has changed, giving rise to different types of life. For example, when the atmosphere had very little oxygen, methane regulated the climate , and methanogenic life predominated. After the appearance of cyanobacteria, the amount of oxygen in the atmosphere increased, making different life forms possible, such as plants, animals, and humans. This process is related to the importance of Earth's atmosphere.
Another important function of the atmosphere is the magnetosphere. This is a region of the atmosphere located outside the Earth that protects us by deflecting solar winds laden with electromagnetic radiation . It is thanks to the Earth's magnetic field that we are not consumed by solar storms.
The atmosphere plays a crucial role in the development of biogeochemical cycles. Its current composition is due to photosynthesis carried out by plants. It also controls the climate and the environment in which humans live (in the troposphere), generating meteorological phenomena such as rain (from which we obtain water) and maintaining the necessary concentrations of nitrogen, carbon, and oxygen. Furthermore, its study is fundamental to understanding aspects such as the vertical dimension of clouds.
Man's action on the atmosphere
Unfortunately, humans are altering the composition of the atmosphere. Industrial activities are increasing emissions of greenhouse gases such as carbon dioxide and methane, as well as emissions of nitrogen oxides that cause acid rain.
The continuous increase in these greenhouse gases is causing global warming. Average temperatures everywhere on the planet are rising, destabilizing the balance of all ecosystems. This is causing climate change, which is triggering a shift in weather patterns. For example, climate change is increasing the frequency and intensity of extreme weather events such as hurricanes, tornadoes, floods, droughts, and so on. It is also disrupting the cycles of phenomena like El Niño and La Niña, many species are migrating or dying due to changes in their habitats, the ice caps are melting, leading to a rise in sea levels, and so forth. To better understand the effects of global warming on our atmosphere, you can read more about it in this related article about cities that could disappear.
As you can see, the atmosphere plays a fundamental role in the life of our planet , which is why we must combat climate change and ensure that greenhouse gas concentrations become stable as they were in the past, before the industrial revolution.
