Joachim R. R. Ritter is an expert in seismological experiments and seismic tomography. He has conducted research at volcanic fields in East Africa, California and Central Europe to reveal the deep roots of the magmatic processes. He is working at the Geophysical Institute at the University of Karlsruhe. Ulrich R. Christensen is a director at the Max Planck Institute for Solar System Research in Lindau Katlenburg. He applies fluid dynamics to study the dynamic processes in planets.