The atmosphere is the gaseous layer surrounding our planet. It is comprised of nitrogen, oxygen, water vapour, and other gases. Gases consist of molecules. The atmosphere is thickest near the surface of the
Earth. It thins out as you go higher and higher into the sky. The thinnest part is called the exosphere. The exosphere is located at an altitude of about 500 km. It ends at the edge of space, where there is no atmosphere.
The atmosphere protects life on earth by filtering out harmful radiation. The atmosphere also helps regulate temperature. It absorbs some of the sun’s energy, which keeps the earth warm.
Water is a very important part of the atmosphere. Water vapour is found in the air. It can also be found in liquid form on the Earth’s surface. It can even be found in solid form, like snow and ice.
The troposphere is the lowest layer of the earth’s atmosphere, extending from the surface of the earth to a height of about 10 km. It contains approximately 80% of the mass of the atmosphere. The average temperature of the troposphere is 15 degrees Celsius.
The stratosphere is the second layer of the atmosphere. The stratosphere starts at an altitude of 11 km and ends at 50 km. The stratosphere is characterised by a decrease in temperature with increasing altitude and the concentration of ozone increases in this layer. The ozone layer is important to life on earth because it absorbs harmful ultraviolet (UV) radiation from the Sun, which would otherwise damage the Earth’s biosphere.
The mesosphere lies between 50 and 85 km above the Earth’s surface. It is the coldest layer of the Earth’s atmosphere. Temperature decreases with height from approximately −90 °C at 50 km to approximately −85 °C at 85 km. The temperature of the mesosphere increases with height during the day and decreases with height at night due to the absorption of radiation from the surface by the ozone layer.
The thermosphere is a layer of the atmosphere between the mesosphere and the exosphere. It extends from the mesosphere to a height of about 500 km above the Earth’s surface and has a temperature between about 500°C to 1,700 °C. The average molecular weight within this layer is about a quarter of that of the molecules below exosphere.
The exosphere is that outermost layer of the Earth’s atmosphere. The exosphere is the most rarefied layer of the Earth’s atmosphere. It extends from the thermosphere to about 10,000 kilometers above the surface of the Earth. The exosphere is mainly composed of highly ionized atoms and molecules. Some of the molecules are so high up in the exosphere that they no longer significantly affect the composition of the atmosphere around them.