Earth’s atmosphere is composed of gases. The gases contained in the atmosphere are made up of 78.09% nitrogen, 20.95% oxygen, 0.93% argon and .038% carbon dioxide. Water vapor and other gases also exist in minute amounts. Volcanic ash, sea spray, pollen, dust and meteoroids can be found in the atmosphere as well. The gasses are kept on earth by gravity. The atmosphere on earth is the only known atmosphere in the universe to be able to protect and sustain life. The atmosphere absorbs harmful ultraviolet radiation as well as warms the earth’s surface by heat retention. It also reduces the temperature extremes of day and night.

Earth’s atmosphere thins out with altitude. The atmosphere slowly dissipates in outer space. There is no distinct boundary to separate the two. The Karman line, which is 100 km away from the surface of the earth, is often credited as being the boundary of the atmosphere and space.

The earth’s atmosphere is divided into five main parts: The exosphere, the thermosphere, the mesosphere, the stratosphere and the troposphere.

The exosphere is the highest point of the atmosphere and is composed of helium and hydrogen. The particles in this part of the atmosphere are so far apart that they do not collide with each other.

In the thermosphere, temperature increases as height increases. Temperatures can go as high as 1,500 degrees Celsius in this area of the atmosphere.

In the mesosphere, temperature decreases as height decreases. Meteors that find their way into the earth typically burn up at this part of the atmosphere. The mesopause, which is the highest peak of the mesosphere, is the coldest place on earth with temperatures averaging at -85 degrees Celsius

In the stratosphere, temperature increases as height increases. The pressure in the stratosphere is 1/1000th sea level. The boundary between the mesosphere and the stratosphere is known as the strato-pause and is normally 50-55km above ground.

The troposphere is the lowest part of the atmosphere it begins at the surface of the earth and ends on the tropo-pause. In this area temperature decreases with altitude.

Revealing Earth’s Atmosphere