What Are the Gases of the Thermosphere?

In the thermosphere, the three major gases making up the air are atomic oxygen, atomic nitrogen and helium. Unlike below the mesopause, the gas components of the thermosphere are separated based on their chemical elements.

The thermosphere is the layer of the earth's atmosphere above the mesophere and below the exosphere. It starts at 56 miles above ground and extends to between 311 and 621 miles and is referred to as the beginning layer of outer space. At this altitude, air turbulence and density is almost nonexistent. This allows the gases to separate based on their chemical properties, unlike the mixed gases below the mesopause, the border between the mesosphere and the thermosphere.

In their natural forms, both oxygen and nitrogen are diatomic molecules, meaning they contain only two atoms of the same element. However, the atomic oxygen and nitrogen in the thermosphere are no longer diatomic. This is caused by high temperatures that fall between 932 and 3,632 degrees Fahrenheit. In addition to the effects of the high temperatures, ultraviolet and x-ray photons from the sun break apart the oxygen and nitrogen molecules, forming atomic oxygen and nitrogen. The high energy from the photons can also tear away electrons from the gases, creating oxygen, nitrogen and helium ions.