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The Atmosphere
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Introduction

Gas Symbol Content
Nitrogen N2 78.084% 99.998%
Oxygen O2 20.947%
Argon Ar 0.934%
Carbon Dioxide CO2 0.033%
Neon Ne 18.20 parts per million
Helium He 5.20 parts per million
Krypton Kr 1.10 parts per million
Sulfur dioxide SO2 1.00 parts per million
Methane CH4 2.00 parts per million
Hydrogen H2 0.50 parts per million
Nitrous Oxide N2O 0.50 parts per million
Xenon Xe 0.09 parts per million
Ozone O3 0.07 parts per million
Nitrogen dioxide NO2 0.02 parts per million
Iodine I2 0.01 parts per million
Carbon monoxide CO trace
Ammonia NH3 trace
The atmosphere is a cloud of gas and suspended solids extending from the Earth's surface out many thousands of miles, becoming increasingly thinner with distance but always held by the Earth's gravitational pull. The atmosphere is made up of layers surrounding the earth that holds the air we breath, protects us from outer space, and holds moisture (clouds), gases, and tiny particles. In short, the atmosphere is the protective bubble we live in.

This protective bubble consists of several gases (below) with the top four making up 99.998% of all gases. By far, the most common, nitrogen, dilutes oxygen and prevents rapid burning at the earth's surface. Living things need it to make proteins. Oxygen is used by all living things and is essential for respiration. It is also necessary for combustion or burning. Argon is used in light bulbs. Plants use carbon dioxide to make oxygen. Carbon dioxide also acts as a blanket and prevents the escape of heat into outer space.

 Next:  Layers of the Atmosphere

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Updated: January 6, 2005
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