About 78 percent of the Earth's atmosphere consists of nitrogen, and oxygen makes up 21 percent. The remaining 1 percent is a combination of argon, water, carbon dioxide and other gases. The Earth's atmosphere is the only atmosphere in the solar system where there is plentiful free oxygen.
The bottom layer of the Earth's atmosphere, the troposphere, is responsible for the weather. The ozone layer is contained within the next layer of Earth's atmosphere, the stratosphere. The Earth's surface is situated roughly 30 miles below the stratosphere. The Earth is largely shielded from the sun's damaging ultraviolet radiation by the ozone layer.