Obituary for a brilliant materials scientist—on Klaus Thoma's death

Abstract

On June 9, 2018, Prof. Dr. Klaus Thoma passed away at the age of 68 after a pulmonary embolism. His sudden death leaves a huge void for us. Until his retirement in 2014, Klaus Thoma was the director of the Fraunhofer-Institute for High-Speed Dynamics, Ernst-Mach-Institute (EMI) in Germany. He characteristically shaped EMI over almost 20 years. Klaus Thoma was an internationally renowned scientist, expert in experimental and computational dynamic materials research, and mentor and promoter for generations of scientists. He was a visionary leader, indefatigably identifying and shaping new topics in materials research and associated applications. He inspired countless people from inside and outside the institute with his passionate way of tackling scientific problems and technological challenges. At the time when Klaus Thoma became director of the Ernst-Mach-Institute in 1996, EMI was mainly known for its experimental capabilities in dynamic materials research and specifically so for defense applications. At EMI, large and unique test facilities were already established for the investigation of the strain-rate-dependent mechanical behavior of materials and shock wave physics. Having a profound international expertise in the development and application of wave propagation codes, Klaus Thoma early on perceived the strategic opportunity of integrating those experiments with the upcoming numerical simulation methodologies for transient processes. He strongly expanded the experimental material testing capabilities of EMI for various fields of applications and laid the foundation for new experimental and numerical approaches in geoscientific dynamic material research and impact cratering research. For the characterization of the shock behavior of materials at extreme conditions flyer plate test facilities are used. This technique is ideally suited to investigate shock metamorphism in minerals and rocks. Recognizing the significance of this technique for crater research, Dieter Stöffler and co-workers started to cooperate with EMI in the early 1970s in the field of experimental investigation of shock behavior of rock-forming minerals such as quartz, feldspar, or olivine. EMI's explosively driven flyer plate method allowed the recovery of the specimen, and led to development of the widely used scheme of progressive shock metamorphism of minerals. Based on a long-lasting cooperation with researchers from the Museum of Natural History Berlin, Klaus Thoma soon recognized that by combining the strengths of EMI in the field of experimental impact testing capabilities with the expertise of cratering research in rocks, a new and comprehensive joint research topic could be initiated, dedicated to the investigation of natural crater formation at the laboratory scale. With EMI internal research funds, Klaus Thoma performed two pilot impact tests on large sandstone blocks on EMI's extra-large two-stage light gas gun during a joint pilot test phase. This prefeasibility study was key for the foundation of the DFG-funded research unit MEMIN—Multidisciplinary Experimental and Modeling Impact crater research network—in 2009, with Thomas Kenkmann as speaker and Klaus Thoma as well as Alex Deutsch as co-speakers. The two-stage light gas guns of EMI played a pivotal role for cratering research within MEMIN, since they allowed reaching previously not achieved crater dimensions at laboratory scales. The purpose of MEMIN was to comprehensively quantify impact processes in various lithologies under lab conditions. After Thomas Kenkmann became Chair of Geology at the Faculty of Environment and Natural Resources at Albert-Ludwigs-University (ALU) of Freiburg in 2010, the close cooperation between ALU and EMI further fertilized crater research: The German Research Foundation (DFG) subsequently also funded MEMIN Phase II, some results of which are published in the August 2018 special issue of MAPS. Klaus Thoma was a brilliant scientist and a gifted research manager. For us, having known and interacted with Klaus Thoma so closely was a great privilege. His visionary thinking, commitment, and persistence made MEMIN possible. This is his heritage in geosciences!