This page will focus on information on the formation of the atmosphere. We will quickly touch on how our planet has the atmosphere that it has now.
A long time ago, our atmosphere was composed greatly of methane and ammonia. Then a chemical reaction occurred, breaking down the methane and ammonia into nitrogen, hydrogen, and carbon dioxide. The lightweight hydrogen escaped our atmosphere, traveling out into space.
That left nitrogen and carbon dioxide. Soon, water vapor in the upper atmosphere was broken down into hydrogen and oxygen. The hydrogen escaped into space, but the oxygen stayed and soon formed an ozone layer. After the formation of the atmosphere, certain blue-green algae began to form on or near the surface of Earth's oceans. They converted the planet's COČ into oxygen. Soon, plants began to grow on land and the oxygen and carbon dioxide levels began to balance. From then on, the levels of OČ and COČ have been somewhat steady.