2. Stratosphere: 7 to 30 miles (12 to 50 km)
There are hardly any clouds in stratosphere. Weather balloons reach this layer. Also, high altitude spy planes fly at this altitude.
3. Mesosphere: 30 to 50 miles (50 to 80 km)
Meteors (shooting stars) burn in mesosphere.
4. Thermosphere: 50 to 185 miles (80 to 300 km)
During its flights, the space shuttle orbited the Earth within this layer and the one above it – the Exosphere. These atmospheric layers also display the Northern and Southern Lights (Aurorae).
5. Exosphere: 185 to 430 miles (300 to 700 km)
There is a thin but vital layer of the gas ozone in the stratosphere. So far, it has been enough to shield us from dangerous ultraviolet rays from the Sun. But now is is being attacked by chemical gases, such as the CFCs (chlorofluorocarbons) once used in aerosol sprays and as coolants in refrigerators. Now holes in the ozone appear over the South pole and North Pole every spring and are lasting longer each year.
More than 99 percent of the atmosphere is just two gases. These are nitrogen (78 percent) and oxygen (21 percent). The remaining one per cent includes argon, carbon dioxide, water vapor and minute traces of other gases such as helium and ozone. (Adapted from World of Science)