Ahmed El Goresy 1934–2019

Photo: Bayerisches Geoinstitut Ahmed El Goresy died at his home in Heidelberg on October 3, 2019, at the age of 85. Ahmed El Goresy was a highly regarded mineralogist with a worldwide reputation. His research focused on minerals and mineral assemblages of extraterrestrial samples. With his major tool, reflected light microscopy, he studied meteorite samples from asteroids, the Moon, and Mars, and lunar rocks and terrestrial impactites. He was a pioneer in complementing his microscopic findings using scanning electron microscopy, electron microprobe, and later the ion probe and Raman spectroscopy. He made numerous discoveries of shock-induced high pressure phases in meteorites and samples from terrestrial impact craters; he detected unusual mineral assemblages in a variety of meteorite types and studied their chemistry and isotopic composition. Ahmed El Goresy obtained his BSc in 1955 in mineralogy and petrology at the University of Heliopolis, Cairo, Egypt. In 1961, he received his PhD for work on ore deposits by using ore microscopy. His supervisor was the famous pioneer of ore microscopy Paul Ramdohr at the University of Heidelberg. Ahmed El Goresy was Ramdohr's last and best student. In 1961, he briefly returned to Egypt taking a research position in Cairo. In 1963, he became research scientist at the Max-Planck Institut für Kernphysik in Heidelberg. He then spent some months as guest scientist at the Smithsonian Astrophysical Observatory and at Harvard University before taking a 2-year postdoctoral fellowship at the Carnegie Institution of Washington. After his return to Germany, he became a senior scientist at the Max-Planck-Institut für Kernphysik in Heidelberg, and later, he was appointed professor at the Universität Heidelberg. In 1998, he officially retired from his position in Heidelberg and moved to the cosmochemistry department of the Max-Planck-Institut für Chemie in Mainz. After closure of the cosmochemistry department in 2005, Ahmed El Goresy moved to the Bayerisches Geoinstitut in Bayreuth, where he continued his research projects until August 2017. During some 20 years, Ahmed El Goresy worked in close cooperation with Paul Ramdohr at the Max-Planck-Institut für Kernphysik in Heidelberg. Paul Ramdohr, the world-leading scientist in opaque mineralogy, began his studies on meteorites only after he had retired from university in 1958. Ramdohr shared his immense knowledge of opaque minerals and his special skills in reflected light microscopy with Ahmed El Goresy. Werner Schreyer characterized Paul Ramdohr with a few sentences that apply equally well to Ahmed El Goresy: “Two keen, extremely observant eyes that could recognize the slightest differences in color or brightness; a memory with the quality of a computer to store the observations made; unlike a computer, however, brilliant intelligence that allowed combination and coordination of these observations with data on occurrence and paragenesis, etc.; and, last but not least, never-ending patience and dedication for his work” (Schreyer 1986). In 1969, Paul Ramdohr became principal investigator (PI) of NASA's lunar sample analysis program. His focus was on the opaque mineralogy of lunar rocks. Ahmed El Goresy was his co-investigator, who eventually took over as PI. El Goresy and Ramdohr made fundamental contributions to the opaque mineralogy and phase assemblages of lunar mare basalts as well as highland rocks and they both participated in the detection of two new minerals, armalcolite and tranquilitite. Further work led to the recognition of subsolidus reduction reactions in lunar spinels, which allowed workers to estimate temperature and oxygen fugacity. An important prerequisite of the scientific success of Ahmed El Goresy and Paul Ramdohr was a fully automated electron microprobe at the Heidelberg Institute. It was the second microprobe of this type after the Geophysical Laboratory in Washington. After lunar research activities had declined Ahmed El Goresy returned to meteorites, which he had never really given up. He now focused his research on the famous Ca, Al-rich inclusions in carbonaceous chondrites and in particular on their opaque phases. These phases do not only include the PGE (platinum group elements) grains but also a conglomerate of other phases like magnetite, MoS2, pentlandite ([Fe,Ni]9S8), Nb-rich ZrO2, Ca- phosphate, and scheelite (CaWO4), and a series of alloys enriched in volatile siderophile and chalcophile elements like Ga, Ge, As, Sn, Zn, etc. The textural setting of these complex objects indicated that they were not formed in situ in their present host CAIs, but were injected in the CAIs before solidification of the hosts. The acronym “Fremdling” (German for stranger) coined by El Goresy is still widely used, although “Fremdlinge” do not come from outside the solar system as initially thought by El Goresy. The “Fremdling” research of Ahmed El Goresy has, nevertheless, stimulated a series of experimental investigations and calculations to explain the occurrence of oxidized and sulfidized phases. In subsequent studies, Ahmed El Goresy discovered that the unusual Acapulco meteorite contains a menagerie of graphite morphologies each with different carbon and nitrogen isotopic compositions. The absence of isotopic homogenization in an otherwise well-equilibrated meteorite is remarkable. This work is typical of Ahmed El Goresy's approach. Detailed petrographic observations are combined with ion-probe isotope analyses, which require close cooperation with isotope researchers. Ahmed El Goresy had the ability to assemble a team of researchers to attack a problem. When he needed a new tool to solve a problem, he would approach the best and most experienced researchers in the field for collaboration. From about 1995 on Ahmed El Goresy intensified his studies of shock effects in chondrites, Martian meteorites, and samples from terrestrial impact craters. Here, his approach to combine optical microscopy with microchemical and microstructural methods unfolded its full potential. He and his coworkers discovered new shock-induced mineral phases including post-stishovite polymorphs (seifertite), high-pressure aluminum-silicate phases (lingunite), akaogiite (high-pressure polymorph of TiO2), and a polymorph of graphite. El Goresy and his coworkers also observed solid-state transformations of olivine to wadsleyite and ringwoodite, decomposition of olivine, growth of wadsleyite, ringwoodite, and majorite from melts during shock events. This work was done in cooperation with scientists from different countries: Tom Sharp (ASU) and Brigitte Wopenka (St. Louis) from the United States, Ming Chen and Xiande Xie from Guangzhou in China, Eiji Ohtanni (Sendai) from Japan, Philippe Gillet and Pierre Beck (Lyon) from France, and Leonid Dubrovinsky (Bayreuth) from Germany. The study of high-pressure polymorphs, their textural occurrence, and relevant phase relations can be used to estimate the magnitude and conditions of impacts in the early solar system. These findings are not only important for the early collisional history of meteorite parent bodies but they are also relevant for studies of the structure and compositions of the interior of the Earth and of other planets. In recent years, Ahmed El Goresy resumed earlier work on enstatite chondrites, in particular the petrographic and chemical characterization of sulfide assemblages, which he did with Yangting Lin (Beijing). His petrographic observations were complemented by SIMS and later nanoSIMS techniques in Ernst Zinner's laboratory at Washington University in St Louis. More recently, he cooperated with Maud Boyet's group in Clermont-Ferrand on the chemical and isotopic characterization of oldhamites and other phases in enstatite chondrites. In addition, he was working with Smail Mostefaoui and the nanoSIMS group in Paris on in situ Mn-Cr dating of niningerite and sphalerite in enstatite chondrites. These studies helped to unravel the timing and evolution of the enstatite chondrite parent body. As with his teacher Paul Ramdohr, much of Ahmed El Goresy's scientific work was done after his retirement in 1998, demonstrating that innovative and creative research is independent of age, at least in the area where Ahmed El Goresy was active. In scientific meetings, Ahmed El Goresy was very outspoken. He clearly stated his opinion and never avoided discussion of controversial issues. He was extremely enthusiastic about his research. It was almost impossible to talk to him about things other than his own research. He was so excited about his findings that in his talks, he would often exceed the time limit. His contributions in meetings and discussions will be missed. Ahmed El Goresy had about 25 students; many of them have made a career in science. The first thing he taught them was to look through a microscope, as the base of any further work. Ahmed El Goresy saw features in thin sections that others did not see. His knowledge of minerals, particularly opaque minerals, was enormous and as he was familiar with all relevant phase relations, he could right away explain these or speculate on the origin of the observed mineral assemblage. He liked to do science. Many times he said: “I am doing science because I am fond of finding unexpected phenomena that bring new knowledge to our community.” Ahmed El Goresy served the scientific community as Council Member of the Meteoritical Society; Chairman of the International Commission on Cosmic Mineralogy of the International Mineralogical Association; and United Nations Visiting Professor at the Institute of Mineral Deposits of the Chinese Academy of Geology, Beijing, China. He participated in the NASA Lunar and Planetary Science Review Board. He was awarded with the Victor-Moritz Goldschmidt Award and the Abraham-Gottlob-Werner Medal of the German Mineralogical Society, the highest award of the German Mineralogical Society. In 1972, he became fellow of the Meteoritical Society, and was the recipient of the Leonard Medal in 2013, the highest honor of the Society (Caillet and Bouvier 2013). Ahmed El Goresy was invited as Fairchild Distinguished Scholar in 1983 to the California Institute of Technology in Pasadena, and he was guest professor at the Muséum National d'Histoire Naturelle in Paris in 1994, and more recently at the Tohoku University in Sendai, Japan, and at the Ecole Polytechnique Fédérale de Lausanne, Switzerland. The International Astronomical Union baptized the asteroid 1981EK8 El Goresy in recognition of his outstanding work on meteorites and their parent bodies. With Ahmed El Goresy, the Meteoritical Society lost a highly motivated researcher with extraordinary abilities. He dedicated his work to the observation and interpretation of microstructures in meteorites and he was one of the key drivers for progress in the field of cosmochemistry. Scientists like him have become rare.