Cosmochemistry: isotopic studies on the origin and evolution of the solar system, planet Mars, meteorites and asteroids; synthesis of the elements
Office: Urey Hall Addn 3050E
University of Berne
University of Berne, Switzerland
Awards and Academic Honors
Visiting Professor, University of Bordeaux
Assistant Research Chemist
Postgraduate Research Chemist
Our research interests are the origin and evolution of the solar system, of planets and aesteroids, and the origin and distribution of the elements and their isotopes.
We are studying processes which were operative in the early solar nebula, on the moon, on Mars, and on the parent bodies of meteorites. Significant variations in the isotopic composition of some elements are observed and these signatures help to constrain the origin of the solar system. Isotopic variations, as well as abundances of now extinct nuclides, also provide clues regarding the origin and synthesis of the elements.
Primitive meteorites are isotopically not fully homogenized, revealing that signatures of matter which formed the solar system were preserved. For example, graphite grains retained their isotopic signatures from the interstellar environment despite the high temperatures reached during melting processes on their parent asteroids.
We investigate the composition of solar particle radiation, the interaction with solar system objects and the relations to planetary atmospheres and meteorites. Cosmic ray reaction products, both stable and radioactive, give information on the history of the investigated samples and on the variation of the cosmic ray flux in time and space. The cosmic ray record, when coupled to data from radiogenic nuclides, permits us to study the history of meteorites and possible links to parent asteroids. We study the cause of cosmic ray flux variations on different time scales using fossil records in iron meteorites. The records of trans-bismuth nuclides which are now extinct show that these were present in the early solar system. The evidence for extinct nuclides 41Ca, 26Al, 107Pd and 129I indicates the addition of freshly synthesized matter during or just prior to solar system formation. Short-lived isotopes provide ideal chronometers for the study of processes in the solar nebula and of the evolutionary history of planets and small solar system bodies. The cratering record and the geological evolution of planetary surfaces are investigated on the basis of cosmic ray reaction products coupled with radioactive isotopes. The evolution of planetary atmospheres, e.g. Mars, is addressed by studies of primitive Martian material which has retained some signatures which were established either during accretion or during the early differentiation of the planet.
- Signatures of Early Differentiation of Mars. With B. Marty. Earth and Planet. Sci. Lett. 196, 251 (2002).
- Early Evolution of Martian Volatiles: Nitrogen and Noble Gas Components in ALH84001 and Chassigny. With K.J. Mathew. J. Geophys. Res. 106, 1401 (2001).
- Ancient Martian Nitrogen. With K.J. Mathew. Geophys. Res. Lett. 27, 1463 (2000).
- Neutron Capture Effects and Radionuclei in the Early Solar Nebula. With X-M. Hua, R.E. Lingenfelter, and A.N. Zytkow. Ap. J. 531, 1081 (2000).
- The 36Cl-36Ar- 40K-41K Records and Cosmic Ray Production Rates in Iron Meteorites. With B. Lavielle, J.-P. Jeannot, J.-P., K. Nishiizumi, and M. Caffee. Earth Planet. Sci. Lett. 170, 93 (1999).
- Signatures of the Martian Atmosphere in Glass of the Zagami Meteorite. With J.S. Kim , A.N. Thakur, T.J. McCoy and K. Keil. Science 267, 1981 (1995).