ABSTRACT
The Earth’s present atmosphere is unique. The Moon and the planet Mercury are airless, whilst Venus and Mars have atmospheres consisting almost entirely of carbon dioxide. Plants and the atmosphere have greatly affected each other, and still do. Air is a mixture of various gases added together. It also contains water vapour, dust and droplets, in quantities which vary with time, location and altitude. Even the world’s human population adds about 0.4 GtC to the atmosphere annually by exhaling; about 5 per cent of what we breathe out is carbon dioxide. The formation of upper-atmosphere ozone involves photo-dissociation of normal oxygen. A standard atmosphere is a nominal relationship between altitude and mean temperatures. An important feature of the upper atmosphere is its ability to conduct electricity through the movement of negative ions, which are whole or part-molecules to which electrons have become attached.
