Robert N. Clayton Enrico Fermi Distinguished Service Professor Emeritus, Departments of Chemistry and the Geophysical Sciences, Enrico Fermi Institute, and the College Enrico Fermi Institute 5640 S. Ellis Ave. RI 440 Chicago, IL 60637 USA Phone: 773-702-7777 E-mail: r-clayton@uchicago.edu Publications Solid Earth and Planetary Sciences

Many chemical elements show variations in the abundances of their stable isotopes in extraterrestrial materials (e.g., meteorites and lunar samples) which are much greater than variations in terrestrial materials. In some instances, these variations can be traced back to processes of nucleosynthesis, both in stars and in interstellar space. In other cases, isotopic variability has been introduced by processes of evaporation and condensation in the solar nebula from which the sun and planets formed. For other elements, isotopic variability results from interactions with energetic particles from the sun (solar flares and solar wind) or from the galactic cosmic rays. We use a variety of mass spectrometric techniques to measure isotopic abundances of many elements: H, C, N, O, Mg, Si, K, Ca, Ti, Cr, Fe, Ni, Sr, Zr, Mo, and others. A method currently under development in collaboration with scientists at the Argonne National Laboratory is Resonance Ionization Mass Spectrometry (RIMS). This ultra-sensitive method allows measurement of nucleosynthetic effects in minor elements present in individual interstellar grains preserved in primitive meteorites.

Isotope abundance variations are also powerful tools for investigation of terrestrial natural processes. For example, the geochemical cycling of carbon and nitrogen through the Earth's crust and mantle can be traced by means of their isotopic compositions. Similarly, the movements of aqueous fluids in the Earth's interior are studied through the isotopic ratios of hydrogen and oxygen.

Education:

• Ph.D., California Institute of Technology , 1955
• Member, National Academy of Sciences
• Fellow, Royal Society (London)
• Fellow, Royal Society of Canada