Studies of the organic chemicals in meteorites and in “space snow” that falls continually on the Earth, show that amino acids and nucleotides (the CGAT building blocks of nucleic acids), together with other moderately complex compounds, were widespread in the solar nebula as it formed.  They can form in the absence of life.  Life’s dependence on DNA and RNA for its necessary self-replication marks a chemically complex step that assembled such building blocks by a process of polymerisation.  That presupposes an awful lot of chance reactions, none more so than the formation of the peptide bond that dominates genetic material and proteins.  Lots of mechanisms have been tested, but none work sufficiently well in a test tube to be plausible candidates for processes on the early Earth.  Perhaps the simplest, first proposed more than 30 years ago is the operation of a simple gas called carbonyl sulphide (COS).  Experiments that expose amino acids to carbonyl sulphide in water at “room temperature” yield lots of peptides in a matter of a few minutes to hours (Leman, L. et al. 2004.  Carbonyl sulphide – mediated prebiotic formation of peptides.  Science, v. 306, p. 283-286).  The more metal ions, such as those of iron, lead and cadmium, that are in the solution, the more efficient the reactions.  The likeliest place for such processes to go on would be near submarine hydrothermal vents, as COH quickly breaks down once emerged from a volcanic source.  Its role could have been crucial in the complex molecular evolution that many biochemists believe to have been intimately associated with the structures of clays and sulphide minerals that hydrothermal activity produces in abundance.