The atmosphere is the outer shell of celestial bodies. On different planets, it differs in composition, chemical and physical properties. What are the basic properties of the Earth’s atmosphere? What does it consist of? How and when did it arise? Learn more about this later.
Atmosphere formation
The atmosphere is a mixture of gases that envelop the planet from the outside and are retained by its gravitational forces. At the time of its formation, our planet did not yet have a gas shell. It formed a little later and managed to change several times. It is not completely known what the basic properties of the atmosphere were then.
Scientists suggest that the very first atmosphere was picked up from a solar nebula and consisted of helium and hydrogen. The high temperatures of the planet and the effects of the solar wind quickly destroyed this shell.
The next atmosphere was formed due to volcanoes that released gases from the mantle of the Earth. It was thin and consisted of greenhouse gases (methane, carbon dioxide, ammonia), water vapor and acids.
Two billion years ago, the state of the atmosphere began to transform into the present. External processes (weathering, solar activity) on the planet and the first bacteria and algae took part in this, due to the release of oxygen by them.
Composition and properties of the atmosphere
The gas shell of our planet does not have a clear edge. Its outer contour is blurred and gradually passes into outer space, merging with it into a homogeneous mass. The inner edge of the shell is in contact with the earth's crust and the hydrosphere of the Earth.
What are the basic properties of the atmosphere is largely determined by its composition. Most of it is represented by gases. The main share falls on nitrogen (75.5%) and oxygen (23.1%). In addition to them, atmospheric air consists of argon, carbon dioxide, hydrogen, methane, helium, xenon, etc.
The concentration of substances is practically unchanged. Variable values are characteristic of water and carbon dioxide. The carbon dioxide content is determined by the amount of vegetation. Water is contained in the form of water vapor. Its number varies depending on geographical latitudes and amounts to 2.5%. The atmosphere also contains combustion products, sea salt, dust impurities, ice in the form of small crystals.
Physical properties of the atmosphere
The main properties of the atmosphere are pressure, humidity, temperature and density. In each of the atmospheric layers, their meanings are different. The air of the Earth’s shell is a multitude of molecules of various substances. The forces of attraction hold them within the planet, drawing them closer to its surface.
The bottom of the molecules is the most, so the density and pressure are greater there. They decrease with height, and in outer space they become almost invisible. In the lower atmosphere, pressure decreases by 1 mm Hg. Art. every 10 meters.
Unlike the surface of the planet, the atmosphere is not heated by the sun. Therefore, the closer to Earth, the higher the temperature. For every hundred meters, it decreases by about 0.6 degrees. In the upper part of the troposphere, it reaches -56 degrees.
The parameters of air are greatly affected by the content of water in it, that is, humidity. The total mass of the planet’s air is (5.1-5.3) · 10 18 kg, where the proportion of water vapor is 1.27 · 10 16 kg. Since the properties of the atmosphere in different areas differ, standard values are derived that are taken as “normal conditions” on the Earth’s surface:
Pressure | 101.35 kPa |
Density | 1.2 kg / m 3 |
Temperature | +20 ° C |
Humidity | 50 % |
The structure of the gas shell of the Earth
The nature of the gas shell changes with height. Depending on what the basic properties of the atmosphere are, it is divided into several layers:
- troposphere;
- stratosphere;
- mesosphere;
- thermosphere;
- exosphere.
The main parameter for distinguishing is temperature. Between the layers, boundary areas are identified, called pauses, in which a constant temperature indicator is fixed.
The troposphere is the lowest layer. Its border runs at an altitude of 8 to 18 kilometers, depending on latitude. Above all, it is on the equator line. About 80% of the atmospheric air mass falls precisely on the troposphere.
The outer layer of the atmosphere is represented by the exosphere. Its lower boundary and thickness depend on the activity of the Sun. On Earth, the exosphere begins at an altitude of 500 to 1000 kilometers and reaches one hundred thousand kilometers. Below it is saturated with oxygen and nitrogen, above - with hydrogen and other light gases.
The role of the atmosphere
The atmosphere is the air we breathe. Without it, a person will not live even five minutes. It saturates all the cells of plants and animals, facilitating the exchange of energies between the body and the environment.
The atmosphere is a filter of the planet. Passing through it, solar radiation is scattered. This reduces its intensity and the harm that it can do in a concentrated form. The shell plays the role of the Earth’s shield, in the upper layers of which many meteorites and comets burn up, not reaching the surface of the planet.
Temperature, density, humidity and atmospheric pressure form the climate and weather conditions. The atmosphere is involved in the distribution of heat on the planet. Without it, the temperature would fluctuate within two hundred degrees.
The Earth’s shell is involved in the cycle of substances, is the habitat of part of living things, and promotes the transmission of sounds. Its absence would make life on the planet impossible.