| 2001 - present : | Professor, Dept of Geology, & Head of Research Unit Earth System Science, Vrije Universiteit Brussel, Brussels, Belgium. |
| 2010 - present : | Guest Professor, Dept. of Geology, Katholieke Universiteit Leuven, Leuven, Belgium. |
| 2009 - present : | Guest Professor, Dept of Geology and Soil Sciences, Ghent University, Ghent, Belgium. |
| 2008 - present : | Guest Professor, Dept of Geology, University of Liège, Liège, Belgium. |
| 1996 - 2000 : | Senior Scientist & Director of Analytical Laboratories, Institute of Mineralogy, Natural History Museum, Berlin, Germany. |
| 1994 - 1995 : | Research Geologist, Dept of Earth and Planetary Science, University of California at Berkeley, Berkeley, California, USA. |
| 1993 : | Postdoctoral Researcher, Institute of Geophysics and Planetary Physics, University of California at Los Angeles, Los Angeles, California, USA. |
| 1991 - 1992 : | Exploration Geologist, Shell Oil Exploration & Production Co - Houston - Texas, USA. |
| 1989 - 1990 : | Research Assistant, Nuclear Chemistry Dept, Lawrence Livermore National Laboratory, Livermore, California, USA (part-time). |
| 1987 - 1992 : | Teaching and/or Research Assistant, Dept of Gelogy, University of California at Davis, Davis, California, USA. |