Citation for 2021 Barringer Award to G. Osinski

Gordon Osinski (Oz) in the field on Devon Island, Canadian Arctic. I first interacted with Prof. Osinski (Oz) some 20 years or so ago, when he was a graduate student at the University of New Brunswick (UNB). His PhD thesis dealt with the Haughton impact structure on Devon Island, in the Canadian Arctic. Oz's thesis on Haughton was awarded the Governor General's Gold Medal as the best PhD thesis at UNB that year. It was a portent of what was to come, with respect to his research contributions to our understanding of hypervelocity impact processes and their products. Oz is now a Professor at the University of Western Ontario and, over the intervening years, he has produced a truly outstanding record of research publications into a variety of “products and processes” with respect to impacts, which includes co-editing a book with the late E. Pierazzo, which has these words in the title and has been cited some 200 times. His overall citation record for his publications stands at around 8000. Although these numbers are, in themselves, truly impressive, what is more noteworthy is the significance of the contributions to our understanding of impacts that he has made through his research. As way of illustration, I will note some examples in this regard. The seminal paper by Kieffer and Simonds (1980) documented the lack of coherent impact melt rocks at impact structures in sedimentary and mixed targets, with their place taken by lithic breccias and suevitic (melt-bearing) breccias, respectively. Why this was the case was not truly understandable, as theoretically sedimentary lithologies will undergo melting at lower shock pressures than crystalline lithologies. This apparent conundrum remained for over 20 years, until Oz's work at the Haughton and, later, Ries impact structures. Through fieldwork and analytical work, using the scanning electron microscopy, Oz first documented the occurrence of impact-melted carbonates, sulfates, and silicates in the matrices of the crater-filling “lithic” breccias at Haughton, and confirmed their presence in surficial suevite breccias at Ries. The continuation of this work led to a defining series of works that documented and summarized the differences in impact melt-bearing lithologies due to differences in the target lithologies. To paraphrase the conclusions, impact melting occurs in all target types but the physical nature of the final melt products differs. One outcome of the documentation of melted sedimentary lithologies in suevite at the Ries was a redefinition of suevite from having a “clastic” matrix to having a “particulate” matrix, to accommodate the melt particles derived from sedimentary lithologies. Oz's continuing fieldwork and analysis of the surficial suevite at the Ries led him to formulate a working hypothesis for its origin as a late-stage melt-bearing flow. Until this working hypothesis, the tenet hypothesis had been that the suevite was derived from some form of late-stage ballistic ejecta. This new working hypothesis for the Ries suevite was not acceptable to some of our colleagues, who countered by proposing that most of the suevite deposits at the Ries owed their origin to the so-called melt-fuel–coolant interaction (MFCI) process, whereby impact melt reacts explosively with water and is fragmented by bubble implosions. This, to a significant extent, was predicated on the working hypothesis that such a process was responsible for the creation of the voluminous breccia deposits above the impact melt sheet at the Sudbury impact structure and mapped as the so-called Onaping Formation. Oz has since countered this by the first in a series of proposed papers dealing with the “suevite conundrum”. In it, he demonstrated that the characteristics of the melt particles in the Ries suevite and the Onaping Formation and not equivalent in their size, shape and degree of sorting, and that only those from the Onaping Formation show equivalence to those in from MFCI processes in the volcanic environment. As all are agreed that the surficial suevite at the Ries is an allochthonous deposit, the most obvious conclusion is that, if it is not emplaced as ballistic ejecta or through MFCI processes, the working hypothesis of Oz that is emplaced by flow still must be given consideration and, as such, our community looks forward to the next installment of the “suevite conundrum” from Oz. Oz's fieldwork at Haughton, Ries and, later, Mistastin, combined with planetary imagery of what are most likely melt-bearing lithologies on the Moon, Venus, and Mars, led him to propose a modified overarching working hypothesis for ejecta emplacement on the terrestrial planets. Namely, the bulk of the ejecta is emplaced by ballistic processes but it is followed by a late stage out-running flow of melt-bearing materials. The extent of such late-stage flows is a function of planetary properties, largely gravity, with a secondary consideration related to the nature of the target lithologies. In hindsight, this seems so obvious from planetary data sets that it was not discerned earlier seems incredible. It is likely that it was missed, as we tend to recognize what we know. The terrestrial environment is the only source of ground-truth data on impact products but terrestrial erosion has served to almost remove field evidence of the occurrence of such late-stage surficial deposits completely. In this case, by far the bulk of the terrestrial observations are not, in fact, the final arbiter of what a fresh complex impact structure would look like on Earth. Another outcome of Oz's early work at Haughton has been his documentation of impact-induced hydrothermal activity and the potential effects of impact, not for the destruction, but for the enhancement of life. One of his publications on Haughton, in fact, has the words “warm and wet oasis” in the title. This relation between impacts and the biosphere is one that is seldom considered and has implications for the early history of Earth. Some of this work has demonstrated that not only do impact events provide a warm and wet postimpact environment but that shocked rocks provide a better environment for microbial life than their unshocked counterparts. Most recently, the culmination of this work linking impact and enhanced biological activity has been accepted as summarizing work in Astrobiololgy entitled “The role of meteorite impacts in origin of life.” Based on Oz's record of accomplishment with previous publications, it is destined to result in our rethinking of our beliefs regarding impacts and their effects and will serve as a highly cited, benchmark publication. I could continue with more examples of Oz's research contributions but I would surmise that they would only serve to exemplify that he has made major, tenet-changing contributions to the understanding of major aspects of the impact cratering process and their effects. I would, however, like to touch on what is sometimes overlooked in terms of an important contribution to the health and future of our community; namely, public outreach, for our research activities do not exist in isolation. Oz has an equally outstanding record in public outreach, having secured funding of over $ 1 million for such activities and projects over his career. While the Director of the Institute for Earth and Space Exploration, Oz developed the most active outreach program at Western University. It had a “Space Explorers Program” that offered themed professional days and summer camps to teachers and Grade 4–6 students, as well as a “Space Academy” during the summer to older students. Of particular relevance to this Society, Oz created and leads the “Impact Earth” initiative, which aims to provide a holistic view of meteorite impacts, from fireballs, to meteorite falls, to the largest crater-forming events for our and the larger community. In addition to an interactive database of all impact craters and deposits on Earth, it provides activities that teachers can use in their classroom, as well as “impactite” rock kits that can be loaned to schools and universities. In summary, Oz has already established a truly exceptional career as a researcher and educator in impact studies. It is my honor to welcome him to the companionship of Barringer Awardees.

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