THE atmosphere is a swathe of air that protects us from the sun's harmful rays and traps enough warmth to keep temperatures from falling too low at night.
Analysis shows the atmosphere consists of 78 per cent nitrogen, 21 per cent oxygen and 1 per cent other gases. It also contains water vapour.
While the atmosphere reaches more than 1,000km above the Earth's surface, some 72 per cent of its mass is below 10,000 metres - the height at which commercial aircraft fly.
Layers of protection
The atmosphere has special zones, each with its own characteristics. A standard method of reference recognises four layers that are defined by temperature, plus an outer layer called the exosphere.
The troposphere is the layer that lies closest to the Earth's surface. The temperature in this layer falls with altitude. The troposphere contains about 75 per cent per cent of the total mass of the atmosphere and is on average 12km high. All weather phenomena such as rain occurs here.