What gas makes up most of the atmosphere of earth?

The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). read more

The next most common gas is oxygen, which is used by both animals and plants for respiration. It accounts for 21 percent of the Earth's atmosphere. The remaining gases combined make up just one percent of the atmosphere. The largest of these is argon, but there are also variable gases like carbon dioxide, which is fourth on the list. Carbon dioxide accounts for about 0.038 percent of the gases in the atmosphere. read more