So the major obstacle to the development of new supplies is not geology but what happens above ground: international affairs politics investment and technology.

As in geology so in social institutions we may discover the causes of all past changes in the present invariable order of society.

A permanent base on Mars would have a number of advantages beyond being a bonanza for planetary science and geology. If as some evidence suggests exotic micro-organisms have arisen independently of terrestrial life studying them could revolutionise biology medicine and biotechnology.