John Michael Hayes

Now retired from active research, but working on a textbook on the subject of "Isotopic Biogeochemistry."  Earlier research focused on Earth's carbon cycle. This refers to the network of processes linking atmospheric carbon dioxide and methane, the biota, and carbon in the Earth''s sedimentary shell. Worked to reconstruct the related coevolution of life and the global environment and to examine the underlying mechanisms.  Together with coworkers studied the relative abundances of the stable isotopes of carbon, nitrogen, sulfur, and hydrogen, often developing new techniques of measurement. They found that distribution of isotopes within molecules reflect their biosynthetic origins and that, in sediments, isotopic differences between molecules reflect the diversity of sources producing those compounds. Exploitation of such lines of evidence has allowed resolution of processes within ancient environments.