The earth’s atmosphere is composed of (in order from lowest of highest);
The density of the molecules of air reduce with increase in altitude. Therefore the higher layers have low air density that those below them.
The exosphere (the outermost layer) extends to outer space and is composed of lighter gases such as helium, hydrogen, carbon dioxide and atomic oxygen.
The rest of the layers consist of molecular oxygen, atomic oxygen, molecule nitrogen, atomic nitrogen, and hydrogen.
The thermosphere has a temperature inversion – increase in temperatures with altitude. This is due to absorption of UV by the ozone layer; the highest ozone layers absorb most of the UV.
