From its very beginnings the development of algorithms for the enumeration of chemical space was closely related to NASA's early exobiology activities. The complete and non-redundant generation of all connectivity isomers corresponding to a given molecular formula was part of the DENDRAL program, established in the mid-1960s. In the 1970s mathematicians provided new techniques to increase efficiency of the first approaches, and starting with the 1990's implementations became available as software packages for customary computers. Recently these methods have been rediscovered for application in astrobiology and origins of life research, particularly for generating and analyzing virtual chemical compound libraries of amino acids and nucleotide analogs.