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James H. Chen's Picture
Address:
Jet Propulsion Laboratory
M/S 183-601
4800 Oak Grove Drive
Pasadena, CA 91109

James H. Chen

Education
  • M. A., Geology, University of California at Santa Barbara (1974)
  • Ph.D., Geology, University of California at Santa Barbara (1977)

Research Interests
  • Cosmochemistry and astrophysics: Improving upon our knowledge of the age and evolution of the solar system by studying terrestrial and extraterrestrial (lunar and meteoritic) samples. The major experimental techniques have involved petrochemical identification of materials derived from stardust, meteorites or different planetary objects, and high precision mass spectrometric determinations of their elemental and isotopic abundances. Evaluating these data using the framework of models for stellar nucleosynthesis in the galaxies and models for nebular and planetary processes in the early solar system.
  • Some of my recent research interests are on the nucleosynthetic origins of some elements in meteorites. These elements (Zr, Mo, Ru) have unusually high abundance of the "p-process" only isotopes. They are very useful indicators for nucleosynthetic processes. Ru and Mo have two p-process only isotopes, all with unusually high abundances (96Ru, 98Ru; 92Mo, 94Mo), one s-process only (100Ru; 96Mo), one r-process only (100Ru; 100Mo) and three (99Ru, 101Ru, 102Ru; 95Mo, 97Mo, 98Mo) that are produced by both r- and s-processes. It may be possible to use Ru and Mo to identify effects due to the decay of the short-lived Tc isotopes: 97Tc-97Mo (τ1/2 = 2.6 x 106y), 98Tc-98Ru (τ1/2 = 4.2 x 106y) and 99Tc-99Ru (τ1/2 = 2.1 x 105y). In addition, I have developed new analytical techniques to separate and measure the isotopic composition of nickel and iron by both the MC-ICP-MS and the P-TIMS instruments. The purpose was to search for evidence for the presence of short-lived 60Fe (decaying into 60Ni, with the half life of 1.5 Ma) in the early solar system. The decay of 60Fe (and 26Al) could be one of the possible heat sources for melting small planetesimals.
  • Geochemistry and geochronology: Application of existing techniques and development of new techniques for solving geochronologic problems over a wide time range (from the Quaternary to planetary time scales). Application of the systematics of U-Th-Pb, Rb-Sr, Sm-Nd and Re-Os to the timing of major thermal events in the solar system.

Professional Experience
  • Jet Propulsion Laboratory (2003-Present)
    • Research Scientist, Advanced Instrumentation and Spectroscopy Group, Planetary and Life Sciences Section, (2005-present)
    • Research Scientist, Instrument Development and Spectroscopy Research Element, Astrophysics and Space Sciences Section, (2003-2004)
  • California Institute of Technology (1980-2003)
    • Senior Scientist and Member of the Professional Staff, Division of Geological and Planetary Sciences (1984 2003)
    • Senior Scientist (1981 1984)
    • Scientist (1979 1981)

Selected Publications
  1. J. H. Chen, D. A. and Papanastassiou (2006) Nickel isotope investigation by MC-ICP-MS and PTIMS., Lunar Planet. Sci. Conf. XXXVII, Lunar Planet. Inst., Houston
  2. D. A. Papanastassiou and J. H. Chen (2006) Comparison of MC-ICP-MS and NTIMS Ru endemic isotope anomalies in meteorites, Lunar Planet. Sci. Conf. XXXVII, Lunar Planet. Inst., Houston.
  3. J. H. Chen, D. A. and Papanastassiou, The palladium isotopic composition in iron meteorites, Lunar Planet. Sci. Conf. XXXVI, Lunar Planet. Inst., Houston, #1495 (2005)
  4. J. R. Boles, P. Eichhubl, G. Garven and J. Chen, Evolution of a hydrocarbon migration pathway along basin-bounding faults: Evidence from fault cement. AAPG Bulletin, 88, 947-970 (2004)
  5. J. H. Chen, D. A. Papanastassiou, G. J. Wasserburg, and H. H. Ngo, Endemic Mo isotopic anomalies in iron and carbonaceous meteorites. Lunar Planetary Science XXXV, Abstract #1431 (2004)
  6. D. A. Papanastassiou, J. H. Chen, and G. J. Wasserburg, More on Ru endemic isotope anomalies in meteorites. Lunar Planetary Science XXXV, Abstract #1828 (2004)
  7. J. H. Chen, D. A. Papanastassiou and G. J. Wasserburg (2002) Re-Os and Pd-Ag systematics in Group IIIAB irons and in pallasites. Geochim. Cosmochim. Acta 66(21), 3793-3810.
  8. J. H. Chen, D. A. Papanastassiou and G. J. Wasserburg (1998). Re-Os systematics in chondrites and the fractionation of the Platinum Group Elements in the early solar system. Geochim. Cosmochim. Acta 62(19), 3379-3382.
  9. J. H. Chen and G. J. Wasserburg (1996), Live 107Pd in the early solar system and implications on planetary evolution. In Earth Processes: Reading the Isotopic Code, Geophysical Monograph 95, (ed. A. Basu and S. Hart), Washington: Amer. Geophys. U., 1-20.
  10. J. H. Chen, R. L. Edwards and G. J. Wasserburg (1990), Mass spectrometry and applications to uranium series disequilibrium, Chapter 6, in book: U-series Disequilibrium, Applications to Environmental Problems (eds. Ivanovich and R. S. Harmon).

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