The atmosphere is created by a mixture of gases and water vapours around the planet that makes it habitable. On earth, the oxygen percentage is mainly responsible for the habitable atmosphere. The presence of water and water vapours is another factor that makes earth habitable. These factors prevent the sudden temperature and climate changes that would have been there due to outer space effects and rotation and revolution of the earth. Without them, the earth would have existed but not as a life-supporting planet. However, these factors have still not been found on Venus and Mars which makes them inhabitable planets for now.
