Where Does Atmospheric Oxygen Come From?
Atmospheric oxygen is an important part of the Earth’s atmosphere and of the conditions that allow for life on Earth. The atmosphere is composed of approximately 80% nitrogen and 20% oxygen, with trace amounts of other elements. The air we breathe has atmospheric oxygen in it, but the atmosphere also helps to make a protective envelope for the planet. There are two sources of atmospheric oxygen, but the primary way in which the Earth generates oxygen for the atmosphere is through photosynthesis. Photosynthesis accounts for 98% of the world’s atmospheric oxygen, while the breakup of water molecules by ultraviolet radiation composes the other 1-2%.
