An atmosphere is a layer of gas or layers of gases that envelop a planet and is held in place by the gravity of the planetary body
. The atmosphere of Earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%), and trace gases
. The atmosphere plays a crucial role in sustaining life on Earth by providing us with air to breathe, shielding us from hostile environmental factors, and maintaining a stable temperature
. The atmosphere is divided into several layers, each with unique properties such as gaseous composition, temperature, and pressure
:
- Troposphere : The lowest layer of the atmosphere, extending from the planetary surface to the bottom of the stratosphere. It contains 75–80% of the mass of the atmosphere and is the layer where weather occurs. The height of the troposphere varies between 17 km at the equator and 7.0 km at the poles
- Stratosphere : The second layer of the atmosphere, which begins at the top of the troposphere and extends up to the stratopause. The stratosphere is characterized by a decrease in temperature and an increase in ozone concentration, which helps protect the Earth's surface from ultraviolet radiation
- Mesosphere : The third layer of the atmosphere, which begins at the stratopause and extends up to the mesopause. The mesosphere is characterized by a decrease in temperature and an increase in humidity, which leads to the formation of water clouds
- Thermosphere : The fourth layer of the atmosphere, which begins at the mesopause and extends up to the thermopause. The thermosphere is characterized by a decrease in temperature and an increase in ionization, which affects the Earth's upper atmosphere and space
- Exosphere : The fifth and highest layer of the atmosphere, which begins at the thermopause and extends up to the exobase. The exosphere is characterized by a decrease in temperature and an increase in the escape of gases into space
The atmosphere is essential for life on Earth, as it protects us from incoming ultraviolet radiation, keeps the planet warm through insulation, and prevents extremes between day and night temperatures
. The Sun heats layers of the atmosphere, causing convection and driving air movement and weather patterns around the world
