Robert N. ClaytonEnrico Fermi Distinguished Service Professor, Emeritus

Research Focus:
Isotope geochemistry, cosmochemistry
(773) 702-7777
Hinds 341

Research Interests

Our research centers on the application of stable isotope abundance measurements to geochemical and cosmochemical problems. We found that oxygen isotopes in solid bodies of the solar system (on scales from planets to individual mineral grains) follow a pattern of nearly constant ratios of 18O/17O, and variable amounts of 16O. This pattern is unlike that seen in natural processes on Earth, where fractionation patterns are linearly dependent on mass differences of the isotopes. We attribute this difference to the dominance of photochemical processes in the early solar system. This interpretation led to a prediction that the Sun should have a several percent excess of 16O, relative to the inner solar system. This prediction has been verified by measurement of the isotopic composition of solar wind oxygen collected by NASA’s Genesis spacecraft.

Other recent studies have dealt with the behavior of the Earth’s atmosphere: the use of oxygen isotopes as natural tracers of stratosphere-troposphere transport rates, and the use of isotopes of oxygen and sulfur isotopes as tracers of the chemical evolution of the atmosphere, especially the rise of the atmospheric O2 in Precambrian time. This latter study involves laboratory measurements of isotope effects in the photodissociation of SO2 gas. All of these studies require precise mass spectrometric abundance measurements of all of the stable isotopes of each element.

Selected Publications

  • Marks, N. E., et al. "Samarium–neodymium chronology and rubidium–strontium systematics of an Allende calcium–aluminum-rich inclusion with implications for 146 Sm half-life." Earth and Planetary Science Letters 405 (2014): 15-24.
  • Clayton, R. N. "Oxygen and Nitrogen Isotopes in the Earth and the Sun." Meteoritics and Planetary Science Supplement 74 (2011): 5010.
  • Ivanova, Marina A., et al. "Dhofar 225 and Dhofar 735: Relationship to CM2 chondrites and metamorphosed carbonaceous chondrites, Belgica‐7904 and Yamato‐86720." Meteoritics & Planetary Science 45.7 (2010): 1108-1123.