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Chemistry & Chemical Biology / New Brunswick |
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| Gregory F. Herzog Professor B.A. 1964, Cornell M.A. 1965, Ph.D. 1970, Columbia Visiting Scientist, Max Planck Institute for Kernphysik, Heidelberg 1976-77 |
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Research
Summary
Cosmochemistry. Origin and evolution of extraterrestrial materials, which include meteorites, micrometeorites, and Moon rocks.Interactions of extraterrestrial materials with cosmic rays
One line of research focuses on the interactions of extraterrestrial materials with cosmic rays. Cosmic rays produce tiny but measurable quantities of various "cosmogenic" radionuclides, which can be measured in extraterrestrial materials. These radionuclides provide information about how long the object was exposed to cosmic rays and about major collisions that the object underwent. In some cases, they help identify the particular parent bodies from which the object came. The cosmogenic radionuclides also have many terrestrial applications. For example, they give clues to the long-term effects of erosion on the Earths surface. We use accelerator mass spectrometry, an extremely sensitive technique, to determine the cosmogenic radionuclide contents of extraterrestrial and terrestrial materials.Thermal histories of extraterrestrial materials
A second line of research is directed toward determining the thermal histories of extraterrestrial materials. When a molten system evaporates, changes in its isotopic composition may occur. We use various forms of mass spectrometry to measure these changes. The results constrain the degree of mass loss experienced by the system and provide information about its composition before heating. Examples of systems studied are micrometeorites, which undergo extensive evaporation as they pass through the Earths atmosphere, and chondrules, which formed from molten siliceous droplets about 4.5 billion years ago.Three-dimensional analysis of micrometeorites
The image at right is a reconstruction of the interior of a type-I deep-sea spherule. The object is about 300?m in diameter. The different colors correspond to different degrees of x-ray attenuation. The yellow area is a hole. The compact blue feature in the upper right is a small nugget composed mainly of Ru, Os, Ir, and Pt that coalesced as the surrounding iron and nickel (not shown) oxidized.Representative Publications
| Articles Schnabel C., Herzog G.F., Pierazzo E., Xue S., Masarik J., Cresswell R.G., di Tada M.L., Liu K., and Fifield L.K. (1999) Shock melting of the Canyon Diablo impactor: Constraints from nickel-59 measurements and numerical modeling. Science 285, 85-88. Terribilini D., Eugster O., Herzog G.F., and Schnabel C. (2000) Evidence for common break-up events of the acapulcoites/lodranites and chondrites. Meteorit. Planet. Sci. 35, 1043-1050. Albrecht A., Schnabel C., Vogt S., Xue S., Herzog G.F., Begemann F., Weber H.W., Middleton R., Fink D., and Klein J. (2000) Light noble gases and cosmogenic radionuclides in Estherville, Budulan, and other mesosiderites: Implications for exposure histories and production rates. Meteorit. Planet. Sci. 35, 975-986. Leya I., Wieler R., Aggrey K., Herzog G.F., Schnabel C., Metzler K., Hildebrand A.R., Bouchard M., Jull A.J.T., Andrews H.R., Wang M.-S., Ferko T.E., Lipschutz M.E., Wacker J.F., Neumann S., and Michel R. (2001). Exposure history of the St-Robert (H5) fall. Meteorit. Planet. Sci. 36, 1479-1494. Alexander C.M.O’D., Taylor S., Delaney J.S., Ma P., and Herzog G.F. (2002) Mass-dependent fractionation of Mg, Si, and Fe isotopes in five stony micrometeorites. Geochim. Cosmochim. Acta 66, 173-183. Herzog G.F. (2002) Isotopes. In: The New Encyclopedia Britannica, Macropaedia. Leya I., Wieler R., Ma P. Schnabel C., and Herzog G.F. (2002) Pre-atmospheric depths and thermal histories of Canyon Diablo spheroids. Meteorit. Planet. Sci. 37, 1015-1025. Herzog G.F. (2003) Cosmic-ray exposure ages of meteorites. In: Treatise on Geochemistry 1, Meteorites, Comets, and Planets (Volume editor, A.M. Davis), Elsevier Pergamon, pp. 347-380. Ma P., Aggrey K., Tonzola C., Schnabel C., de Nicola P., Herzog, G.F., Wasson J.T., Glass B.P., Brown L., Tera F., Middleton R., and Klein J. (2004) Beryllium-10 in Australasian tektites: constraints on the location of the source crater. Geochim. Cosmochim. Acta, submitted.. Eugster O., Herzog G.F., Marti K., and Caffee M.W. (2004) Recent irradiation and cosmic-ray exposure ages. In: Meteorites and the Early Solar System II, submitted. Book Tuniz C., Bird J. Roger, Fink D. and Herzog G.F. (1998) Accelerator Mass Spectrometry: Ultrasensitive Analysis for Global Science. CRC Press, 371 pp. |