THE ATMOSPHERE

The atmosphere is a mixture of different gases, particles and aerosols collectively known as air which envelops the Earth. The atmosphere provides various functions, not least the ability to sustain life. The atmosphere protects us by filtering out deadly cosmic rays, powerful ultraviolet (UV) radiation from the Sun, and even meteors on collision course with Earth.

• The earth's atmosphere is a very thin layer wrapped around a very large planet.
• Two gases make up the bulk of the earth's atmosphere: nitrogen which comprises 78% of the atmosphere, and oxygen , which accounts for 21%. Various trace gases make up the remainder.
• Based on temperature, the atmosphere is divided into four layers: the troposphere, stratosphere, mesosphere, and thermosphere.

Nitrogen	N2	78.08%
Oxygen	O2	20.95%
*Water	H2O	0 to 4%
Argon	Ar	0.93%
*Carbon Dioxide	CO2	0.0360%
Neon	Ne	0.0018%
Helium	He	0.0005%
*Methane	CH4	0.00017%
Hydrogen	H2	0.00005%
*Nitrous Oxide	N2O	0.00003%
*Ozone	O3	0.000004%