If there is life anywhere else in the Universe, it is very likely that it is based on the carbon molecule, just as it is on Earth. This theory makes sense because the possible compounds of carbon out number the compounds of all the other elements put together, ten times over.

Carbon atoms seem able to join together to form stable molecules almost regardless of the number of carbon atoms involved. As a result of this property, a virtually endless variety of molecular ‘backbones’ can be constructed from carbon. Giant molecules like the ones which combine to make up natural proteins and man-made plastics, are based on it. Very few known elements can form such large molecules and those that can, such as sulfur, are more restricted in the range of other elements with which they will combine.

Each carbon atom can link with up to four other atoms, including other carbon atoms. So the number of possible compounds which can be made from carbon escalates rapidly as the number of carbon atoms in a molecule increases. Try some basic mathematics here: five carbon molecules can attract twenty more, which can attract eighty, and so on.

Propane, which is used as bottled gas, has the chemical formula CH3CH2CH3 which shows that each molecule contains three carbon and eight hydrogen atoms. Butane C4H10 is a similar gas which has four carbon atoms and ten hydrogen. The four atoms can be arranged in a single chain or with the fourth carbon forming a branch in the middle. These different structures give rise to two compounds which are known as isomers and these have different properties. Here, the straight chain of atoms would be normal butane and the other would be isobutane.

As the number of carbon atoms in a molecule increases, more and more forms of the same molecule are possible. By the time a molecule has gathered up 40 carbon atoms there are 62.5 million million possibilities, giving a vast range of possible compounds, many of which are still unknown to science.

This relativly easy chemistry lesson demonstrates how carbon can combine with so many other elements to come up with almost infinite possibilities. Carbon is the most versatile element in the Universe, so, by the law of averages, it is likely that life anywhere else will be based on the carbon atom. Science has not yet investigated all the possibilities that carbon offers and has no idea what might be possible. With so many millions of untested and uninvestigated options, chemistry is indeed a fascinating subject and may some day hold the key to understanding life elsewhere in the Universe.