More recently, theories based on a hydrothermal origin have gained ground. Cody et al . It occurs in numerous metabolic pathways, notably the reductive citric acid cycle and the pathways that produce amino acids and sugars. Cody et al. provide experimental support for this suggestion. They show that pyruvic acid forms from formic acid in the presence of nonylmercaptane and iron sulfide at 250C and 200 MPa.
Water is initially absent and forms only by the dehydration of the formic acid.
This result poses fascinating thermodynamic and kinetic questions. It appears paradoxical that at the very high temperature required for dehydration of formic acid, the relatively unstable pyruvic acid can form and exist at detectable concentrations. Moreover, it is astonishing that acetic acid is formed at a lower yield than pyruvic acid. The explanation may well lie in the very high pressure. It remains to be established whether such conditions are geophysically possible.