A shell of air and gases surrounds our earth. This is also called the atmosphere. It consists primarily of oxygen and nitrogen. We humans and many animals need the oxygen to breathe and to survive.
The atmosphere consists of five layers. Each of these layers has its own characteristics and benefits the earth in different ways.
The first and thinnest layer around our earth is the troposphere. It goes up to 17 kilometers in height. About 85 percent of the total air mass collects here. This allows us humans to breathe and survive. All weather processes also take place in this layer. The higher you go in the troposphere, the colder it gets. Temperatures can reach as low as minus 80 degrees Celsius at the outermost edge of this layer. The temperature decreases by about 6.5 degrees Celsius for every kilometer in altitude.
The second layer is the stratosphere. It ranges from 16 kilometers to 50 kilometers in height. In this layer it gets warmer again and no longer cold. The ozone layer is also in the stratosphere. This protects us humans on earth from dangerous radiation. It also converts the ultraviolet rays of sunlight into heat. These rays are also known as UV rays. This heat causes temperatures to rise from minus 80 degrees Celsius back down to zero degrees Celsius.
From 50 to 85 kilometers in height is the mesosphere. Since there is hardly any ozone left in this layer, the temperatures drop again. It can be as low as minus 100 degrees Celsius here. This makes the mesosphere the coldest layer in our atmosphere. In this layer happens what we perceive as shooting stars on earth. When dust particles and smaller rock fragments from space enter the mesosphere, they burn up because of the low temperatures here. Without this braking layer, these chunks would fall to earth.
The fourth layer of the Earth's atmosphere is the thermosphere. It is located between 85 and 500 kilometers from Earth. Space Shuttles and the International Space Station are located in this layer. It orbits the earth at a height of 350 kilometers. Temperatures in this layer rise to over 1,700 degrees Celsius.
The ionosphere is part of the mesosphere and the thermosphere. The ion content in this layer is very high, causing radio waves and light to be reflected. We perceive these reflections on Earth in the polar regions as aurora borealis.
The outermost layer of our atmosphere is the exosphere. It starts at an altitude of about 500 kilometers and reaches up to 10,000 kilometers in altitude. This layer does not have a precise boundary, since gravity is weakening here. As a result, at some point gas molecules can no longer be held and flow into space.