The Earth's
atmosphere is composed of 78% nitrogen, 21% oxygen and less than 1% of argon
and carbon dioxide, excluding water
vapor and pollution. Very small amounts of hydrogen, neon, helium, krypton,
xenon, methane and ozone are also present.
Earth's
original atmosphere was composed of ammonia and methane. 2 million years ago
different types of elements started to be added to the air. The weight of the
atmosphere is approximately 50000000000000000 tons. It exerts an average
pressure of 14.7 pounds per square inch on Earth's
surface.
