Introduction to the Atmosphere

Introduction to the Atmosphere
The atmosphere is a mixture of different gases, particles and aerosols collectively known as air which envelops the Earth, 99% of the mass of the atmosphere lies below about 25 to 30km altitude, whilst 50% is concentrated in the lowest 5km.
Air is uniform in composition, and that the result of efficient recycling processes and turbulent mixing in the atmosphere. Such recycling and mixing of the air helps to minimize the amount of time which man-made pollution spends in the atmosphere at any location, thereby reducing the environmental impacts. Dry air from Earth s atmosphere contains 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and traces of hydrogen, helium, and other "noble gases" (neon, helium, krypton, xenon and ozone), but generally a variable amount of water vapor is also present, on average about 1% at sea level. While the atmospheres of the planets Venus and Mars are primarily composed of carbon dioxide, with small quantities of nitrogen, argon, oxygen and traces of other gases.