2014 Barringer Medal for Alexander Deutsch

Impact is a geological process that has, quite literally, its origin “out of this world.” That asteroids and comets collide with Earth and cause global catastrophes did not fit in, for a long time, with the uniformitarian view of gradual changes in the geological record. Considering that Earth is the most endogenically active of the terrestrial planets and, thus, has retained the poorest geological record of impact events, one may understand that it took so long to recognize the importance of impacts. Starting with the pioneering works in the 1950s and 1960s, impact research has now evolved from a qualitative, descriptive science to a quantitative, well-recognized branch of geosciences. This development would have not been possible without the remarkable contributions by Alexander Deutsch. Alexander Deutsch Alex himself describes his research in terms of a ternary phase diagram with these apices: field geology, isotope dating, and impact experiments. These apices confine also the chronology of his scientific career and a fourth, more recent dimension could be added: modeling. Having graduated from the University of Vienna, Alex started his career with geological mapping in the Alps (first apex: “field geology”). Then, he moved to the Eidgenössische Technische Hochschule Zürich, where he gained his knowledge in radiometric age dating (second apex: “isotope dating”). Starting from this background he joined the group of Dieter Stöffler at the University of Münster in 1983 and thus entered into a field of research that was new to him: impact cratering. His first impressive contribution to the new field was the precise Rb-Sr dating of the Imbrium basin on the Moon. Inspired by this study, he continued to examine the isotope systematics of terrestrial impact rocks (e.g., at Haughton, Sudbury, Araguainha, Dellen, Lappajärvi, and Popigai) and to design shock experiments allowing him to constrain the conditions that must be fulfilled to reset an isotope system by impact (third apex: “impact experiments”). Alex received the venia legendi (permission to supervise Ph.D. students) for this outstanding work and published a number of fundamental papers on the dating of impact events, mostly together with Urs Schärer. Throughout Alex's further career, impact experiments became an indispensable tool to simulate and understand natural impact phenomena. To assess the environmental consequences of the Chicxulub impact, he was strongly engaged in experimental studies of volatiles, particularly CO2 and SOx, released from shocked rocks and evaluated the role of rapid back-reactions. In this context, Alex collaborated with Boris Ivanov to model the pressure–temperature paths of shocked carbonates in a theoretically calculated phase diagram of CaCO3 (fourth apex: “modeling”). More recently, Alex's research has moved back and forth between the apices of the Deutsch ternary diagram. His geochemical studies on establishing the link between (micro-) tektites and source craters (Chesapeake Bay, Chicxulub, Bosumtwi) are highly recognized and recent mesoscale cratering experiments within the MEMIN research group are an innovative approach to realistically reproduce and study cratering processes in the laboratory. One of the most memorable events in Alex's career was possibly the international Popigai expedition (IPEX) in 1997 led by Victor Masaitis, which brought us to a very remote impact place in Northern Siberia. This adventure involved breath-taking helicopter flights; harsh nights at freezing temperatures; energy-sapping hikes through swamps and over stony hills; and scientific discussions in the tent with Boris Ivanov, Richard Grieve, Victor Masaitis, and other members of the IPEX team. Alex managed under enormous efforts to bring back a unique collection of impact rocks that represents a treasure chest for studying a large 3-D model crater on Earth, the well-preserved 100 km diameter Popigai impact structure. In awarding the Barringer Medal to Alex, we recognize also his exemplary professional services to the scientific community and Meteoritical Society. Alex is known to have an evenhanded and well-balanced judgement. Thus, it is not surprising that he has been associate editor of Meteoritics & Planetary Science for almost 20 yr, and was a member of several advisory boards including the Council of the Meteoritical Society. He was a member of the steering committee of the ESF program Impact, organized workshops, edited special volumes on impact cratering, was engaged in ERASMUS teaching activities, and has popularized planetary research in public talks and popular scientific articles. It is hardly possible for me to appreciate all the achievements of Alex, as his work has touched on almost every aspect of impact research. There is no doubt that Alex is an outstanding scientist and has made long-standing fundamental contributions to the petrology, geochemistry, and shock metamorphism of impact rocks. I am grateful for the enormous support in nominating him and heartily congratulate Alex on winning the Barringer Medal 2014.

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