The European Research Council (ERC) has awarded Prof. Dr. Tomo Katsura of the Bavarian Research Institute of Experimental Geochemistry & Geophysics, University of Bayreuth, with an ERC Advanced Grant. For his research project with which he intends to explore an unsolved riddle of the earth's mantle, he will receive a total of 2.6 million euros in funding over the next five years. The ERC Advanced Grant is the most important European research prize. It is presented to outstanding scholars whose pioneering ideas have made especially innovative contributions to developments in their disciplines.
It has long been known that the crust of the earth is made of tectonic plates, which float on the upper mantle and are constantly drifting, similar to ice floes on the sea. However, plate tectonics are not the only determining cause for the present form of Earth's surface. They also cause a material cycle between the surface and Earth's interior, which is probably a basic condition for life on Earth. Despite numerous research findings, our scientific understanding of the cycle is still incomplete, especially with regard to the lower mantle. Recent geoscientific discoveries have corroborated the assumption that the material cycle slows down significantly at a depth of between 660 and 1,000 kilometers. The material becomes more and more rigid and gluey in this section of the lower mantle; in physical terms, the viscosity increases. The reasons for this remain unclear to this day.
Prof. Dr. Tomo Katsura has now proposed a possible explanation which addresses a mineral that accounts for more than half the volume of our planet: bridgmanite. This mineral belongs to the class of perovskite compounds. Geoscientific researchers agree that bridgmanite plays a crucial role in the physico-chemical processes in the earth's mantle.
Katsura believes that properties of bridgmanite change with increasing pressure in the lower mantle. At a depth of 660 kilometres - at the upper limit of the lower mantle - the crystal lattice of the bridgmanite develops numerous voids: many parts of the crystal lattice have atoms missing. These structural defects make the mineral loose and highly movable, facilitating the material transport in Earth's interior. However, at greater depths up to 1,000 kilometres, the voids in the crystal lattice are almost completely filled. As the bridgmanite becomes rigid, the material cycle comes to a halt.
Prof. Katsura plans to test this hypothesis over the next five years. The tests will involve large-volume presses used to investigate material samples at extremely high pressures. Previously, it was generally impossible to exceed a pressure of 26 gigapascals using such presses. However, Katsura developed technological modifications for the presses which enable them to far exceed this limit, simulating pressures that are found in the earth's lower mantle at a depth of between 660 and 1,000 kilometres. Because of this innovation, it can be determined with great precision what structural defects appear at changing pressures and how these changes affect the viscosity of Earth's mantle. The high-performance large volume presses (LVPs) are mentioned in the title of the funded research project: "UltraLVP".
Katsura will be working together with other researchers in various fields at the Bavarian Research Institute of Experimental Geochemistry & Geophysics (BGI), in particular with Prof. Dan Frost (Thermodynamic Modelling), Dr. Catherine McCammon (Mössbauer Spectroscopy), Dr. Nobuyoshi Miyajima (Transmission Electron Microscopy), and Prof. Gregor Golabek (Geodynamic Modelling). For a few special tests, he is planning to use the research technology at the German Research Centre for Geosciences (GFZ) in Potsdam and the SPring-8 Synchrotron in Harima Science Park (Japan).
Prof. Dr. Tomo Katsura was born in Nishinomiya/Japan (between Osaka and Kobe) in 1962. After studying geoscience and materials science, he completed his doctorate at Okayama University in 1991 and joined the University of Bayreuth's Bavarian Research Institute of Experimental Geochemistry & Geophysics (BGI) in the same year for a two-year postdoctoral position. In 1993, he returned to Okayama University, where he worked as a professor until accepting his current position as Professor of Structure & Dynamics of Earth Materials at the University of Bayreuth in 2010. He has also belonged to the the Directorate of the BGI since 2010.