The atmosphere is a thin coating of gases that surrounds Earth. It stretches to over 560 kilometers from the surface of the Earth. It protects us by blocking out hazardous rays from the sun. It is retained by the Earth’s gravity. The thickness of the atmosphere is the equilibrium between the gravity of the Earth and the energetic molecules that move towards space.

Earth’s atmosphere is composed of Nitrogen (78%), Oxygen (21%), and other gases (1%) including water vapor, argon, carbon dioxide  and traces of hydrogen, helium, and “noble” gases. Additional elements from natural sources include dust, pollen, and spores, sea spray and meteoroids. Industrial pollutants such as chlorine, fluorine, mercury, and sulfur are also present in the air. It has specific molecules like ozone (O3) that filter out unsafe radiation from space. The atmospheres of other planets like Venus and Mars are composed of carbon dioxide and traces of nitrogen, argon, oxygen and other gases.

The atmosphere is divided into four layers namely the troposphere, stratosphere, mesosphere, and thermosphere. There is no specific edge between the atmosphere and outer space. It gradually becomes thinner and diminishes into space. About 80% to 90% of earth’s atmosphere is found in the troposphere which stretches about 12km of the earth’s surface. It is a layer where we live. The stratosphere stretches up to about 53 km.

Atmosphere is moving source of life

• It protects us from the vacuum of space.
• It protects us by absorbing ultraviolet solar radiation.
• It protects us by warming the surface through heat retention (greenhouse effect).
• It protects us by reducing temperature extremes between day and night.
• It protects us from cosmic debris.
• It offers oxygen for respiration, carbon dioxide for photosynthesis, nitrogen for nitrogen fixation, and water vapor for precipitation.
• Carbon dioxide and water vapor decrease temperature extremes between day and night.

Properties of Atmosphere

• The atmosphere is not an ideal gas but it behaves like an ideal gas.
• The density of air at sea level is about 1.2 kg/m3 which decrease as the altitude increases.
• The mass of the atmosphere is about 1/1,200,000 the mass of Earth.
• The atmosphere radiates sunlight back into space. Important examples of this are clouds and the greenhouse effect.
• The atmosphere scatters light. For example, due to a phenomenon of Rayleigh scattering, the blue color of shorter wavelengths scatter more easily than the red color of longer wavelengths. This makes the sky look blue. On the other hand, during sunset, as the sun is closer to the horizon the sun rays pass through more atmospheres the sky appears red.
• Absorption and emission is an important property of atmosphere. The greenhouse effect is directly related to this absorption and emission effect.
• Meteors strike the thermosphere and mesosphere and burn from the heat generated by air friction.

Atmospheric problems

Human activities such as industrial production and fuel burning have been liberating pollutants into the atmosphere.

Greenhouse Effect: Owing to increases in gases like carbon dioxide, the atmosphere is getting affected through the greenhouse effect and global warming. The main source of emissions of carbon dioxide, nitrous oxide, and methane are combustion of fossil fuels and deforestation.

Damage to the ozone layer: Ozone shields the Earth from the sun’s harmful UV rays. Concentrations of ozone appeared to be dropping due to the emission of CFCs into the environment. There is a decrease in the amount of stratospheric ozone of atmosphere.  Up to 60% of the total overhead amount of ozone in Antarctica is depleted during the Antarctic in September-November.  This   is known as the Antarctic ozone hole.

Acid rain: Rainwater is naturally acidic which reacts with sulfur dioxide and nitrogen oxides in the atmosphere and causes many problems when they fall to the ground. Lakes become acidic due to which marine plants and animals die, the growth of the trees is hampered. It also attacks the metal structures of buildings and houses which become weak.

Other effects of the depletion of the atmosphere are:

• Thermal increase of the water and melting of glaciers causes the sea levels to rise.
• Rise in temperatures is leading to changes in wind systems which influence rain distribution and lead to the floods, droughts and forest fires.
• Rise in sea temperatures has led to the destruction of coral reefs.
• Water supplies would become disrupted and droughts are frequent.

Various measures are taken to reduce the emission of pollutants:

• Reducing air pollution by cutting down on vehicle miles driven by car pools and use of buses.
• Use of clean burning fuels.
• Handling chlorofluorocarbon refrigerant in refrigerators and air conditioners properly which damages the protective ozone layer.
• Use alternative fuels vehicles motorized by natural gas. It produces less pollution. Electric vehicles produce no air pollution.
• Industrial air pollution should be controlled.