Conclusions

Abstract

The chemical richness of the Milky Way and other galaxies can be explained by a combination of gas phase reactions together with reactions on the surfaces of dust grains and reactions in ices deposited on those grains. Molecules and dust grains play important roles within galaxies, affecting their physical evolution by driving star and planet formation and modifying the content of the interstellar medium. We show that the difficulties (expressed in Chapter 1) of creating extensive chemistry in the apparently hostile environments of the Milky Way and other galaxies can be readily overcome. Star and planet formation provide locations in which a remarkably rich range of organic molecules can form; these species include a number of amino acids that may form the building blocks of RNA and DNA. This result, confirmed by many laboratory experiments, lends support to the concept of abiogenesis – the origin of life as a consequence of reactions in non-living matter. However, the necessary intervening steps are not yet understood.