It is a great honor for me to write this award citation for Prof. Dr. Gareth S. Collins and Prof. Dr. Kai Wünnemann, two extraordinary geophysicists, who both have devoted their careers to the study of impact craters and the role impact processes play in the solar system (Figure 1). The joint Barringer Medal is awarded for their outstanding and fundamental advancements in numerical modeling of shock physics and impact cratering. The award and medal honors the joint development of the iSALE shock physics code and its application to understanding impact crater formation at scales that range from the microscopic level to giant impacts. Thanks to Gareth and Kai, the iSALE computer code has become the numerical tool of choice for anyone interested in simulating impacts. The iSALE code is practically the only impact physics code with open access and has more than 200 users worldwide. Kai, Gareth, and their students continue to develop the code to cover more unresolved problems and to merge the gap between geological observations and physical models. Most of Gareth's and Kai's research involves the use of sophisticated computer codes. With an outstanding intuitive grasp of physics, they were able to efficiently implement relevant petrophysical parameters necessary for realistic simulations of natural impact processes. The iSALE shock physics code is based on the original SALE code (Simplified Arbitrary Lagrangian Eulerian; Amsden et al., 1980) that included an elasto-plastic constitutive model and allowed the use of various equations of state of multiple materials (Ivanov et al., 1997; Melosh et al., 1992). Gareth Collins and Kai Wünnemann improved the code in various ways by developing a modified strength and damage model (Collins et al., 2004), a porosity compaction model (Collins et al., 2011; Wünnemann et al., 2006) the 3-D version iSALE-3D (Elbeshausen et al., 2009; Elbeshausen & Wünnemann, 2011), and a dilatancy model (Collins, 2014). Having implemented porosity (Wünnemann et al., 2006), both were, for the first time ever, able to numerically derive the observed “scaling relations” between crater diameter and impact energy for small craters in porous materials such as sand, and showed that both porosity and friction between grains contribute almost equally to the observed scaling relation. They have also used this model to understand how porosity enhances melt production within impact craters and asteroidal collisions (Wünnemann et al., 2008). As preparations began for NASA's GRAIL mission to measure the Moon's gravity field, Gareth realized that the one critical piece missing from impact crater modeling is a reliable means for computing the volumetric expansion (dilatancy) due to fragmentation by a stress wave during impact. With the implementation of dilatancy (Collins, 2014), it is now possible to precisely correlate and match gravity signatures of craters with numerical simulations. Almost all craters are formed by oblique impacts. To adequately model obliquity, in particular highly oblique impacts, that show strong deviations from axial symmetry, full three-dimensional modeling is required. The development of the iSALE-3D version (Elbeshausen et al., 2009, 2013; Elbeshausen & Wünnemann, 2011) was the logical solution to address these issues. Numerical simulations must be rigorously tested for their validity. The iSALE hydrocode has been benchmarked against other hydrocodes (Pierazzo et al., 2008) and is validated against experimental data to assure the best performance (Pierazzo et al., 2008; Stickle et al., 2020). Based on these jointly developed and constantly improved iSALE hydrocodes, Kai and Gareth have investigated and solved many open questions in the field of impact cratering research, either together or with their students or other collaborating scientists. I would like to start with a few examples of common projects of Gareth and Kai. An important study was that of the buried and partly submerged Chesapeake Bay impact structure in Virginia, which is the largest impact crater in the United States. Gareth and Kai used a considerable strength contrast between the crystalline basement and the semi- to unconsolidated shelf sediments and were able to model a final crater that was consistent with the observational constraints (Collins & Wünnemann, 2005). This modeling was extremely important for the subsequent deep drilling project in the Chesapeake Bay impact structure in 2008 that was jointly funded by ICDP and the USGS. The predictions turned out to be so good that they were subsequently used to guide further geologic interpretation of the crater (Kenkmann et al., 2009b). Initially, Gareth and Kai concentrated on modeling mid-sized complex craters, such as the Ries (Wünnemann et al., 2005), Sierra Madera (Goldin et al., 2006), and Elgygytgyn and Haughton craters and compared their structural differences (Collins et al., 2008a). They explained the structural differences between them by the difference in thickness of the pre-impact sedimentary cover resting on crystalline basement. Kai and Gareth joined the impact cratering community at almost the same time at the beginning of the new millennium and they both have rapidly made it to the forefront of impact crater studies. Their careers run remarkably parallel. Kai Wünnemann graduated in 1998 at the Westfälische Wilhelms Universität Münster in Germany and started his career there at the Institute of Geophysics as a PhD fellow, later as a Research Associate. During this time, he got in touch with Barringer awardee (1998) Prof. B. A. Ivanov of the Russian Academy of Science, the developer of the SALE-B code. In the following years, Boris Ivanov became his mentor and teacher. Gareth received a Bachelor degree in Geophysics with Mathematics at the University of Liverpool in 1998 and then started a PhD at Imperial College London in the group of Barringer awardee (2020) Prof. J. Morgan. This was also the time when Kai met Gareth and the intense collaboration of both began. After completing his PhD, Gareth became a Research Associate at the Lunar and Planetary Laboratory at the University of Arizona, USA, and joined the group of Prof. H. J. Melosh in 2002. Jay Melosh, Barringer Awardee of 1999, who sadly passed away in 2020, was an outstanding scientist of modern impact cratering who brought a high level of physical rigor to the field of impact cratering. During this time, Kai became post-doctoral fellow at the Imperial College London, and later on also at the Lunar and Planetary Laboratory (LPL) in Tucson, USA. In the scientifically inspiring environment at LPL, the iSALE code rapidly grew and has been transformed to the fundamental tool in impact science that we are facing today. In 2005, after his post-doctoral period, Kai went back to Germany and became head of a junior research group at the Museum of Natural History Berlin, Germany. I had the great luck to work with Kai in this institute at that time for a couple of years and we used the time for joint projects. In 2011, Kai became head of the Department Impacts and Meteorites Research and since 2017 he is a Professor of Impact and Planetary Physics at Freie Universität Berlin and the Museum of Natural History. When Gareth returned to the UK in 2004, he passed through the various stages of academia at Imperial College London and became at first a NERC Research Fellow (2004), then an Advanced Research Fellow (2007), a Senior Lecturer (2011), a Reader (2014), and, since 2018 he is a Professor of Planetary Science. Both Gareth and Kai are training young impact researchers to ensure that their knowledge is passed onto the next generation. The diligent supervision assured the high level of quality that characterizes their common publications. Some of the former PhD students and staff have since made names for themselves and are well known in the impact community: Dr. A. S. P. Rae, Dr. V. Bray, Dr. R. W. Potter, and Dr. T. M. Davison went through the “Collins” school, while Dr. M. Zhu, Dr. D. Elbeshausen, Dr. N. Güldemeister, and Dr. R. Luther passed the “Wünnemann” school. Of course, Gareth and Kai also tread separate paths and they have set their respective scientific priorities. In the following, I would like to list some scientific milestones that both have achieved so far in the middle of their careers. Even though these studies are not mutually co-authored, they are based on the common groundwork documented in the iSALE code and prosper from intense communication between both of them. To my opinion, one of the major achievements of Gareth is his modeling of the Chicxulub impact structure and proving the formation of peak rings by central-peak collapse (Collins et al., 2002, 2008b, 2020; Morgan et al., 2016). He showed in detail how a central uplift forms and how the inner ring of the crater results from the collision of the inward-collapsing rim with the outward-moving base of a collapsing central peak. This interpretation was consistent with the structures imaged by deep seismic sounding of the crater and is now largely confirmed by the results of the IODP/ICDP 364 drilling expedition. He has definitively laid to rest the melt cavity model of peak ring formation (Baker et al., 2016). He also applied these studies, for example, to craters on the Moon such as the Schrödinger basin (Kring et al., 2016). Gareth is a co-developer of a very popular interactive web program, called the Earth Impact Effects Program (impact.ese.ic.ac.uk) for estimating the environmental consequences of impact events (Collins et al., 2005). It has gotten a great deal of media attention. This website continues to receive more than 2000 “hits” per week (and up to 10 times more when asteroids or comets are in the news), with users ranging from elementary school children to professional scientists and the journalists for whom the website was actually designed. Finally, to make this website something more than the “cartoon” that such sites may become, Gareth took the lead in writing up a scientific paper in which the code, all of its approximations, and the actual equations evaluated by the program are described. Gareth has continued to improve the program, recently adding a link to Google Earth to produce area maps of impact damage as well as the ability to predict tsunami effects in the event of an impact into the oceans. This capability was recently called for by civil defense groups in the United States to aid in disaster response in the event of a large asteroid impact. Gareth is also involved in many planetological studies. He has contributed to determining the size and formation process of the largest impact basins on the Moon, the Orientale basin (Johnson et al., 2016; Potter et al., 2013) and the South Pole Aitken basin (Miljković et al., 2015; Potter et al., 2012). He was involved in understanding the positive gravity anomalies of the large impact craters on the Moon (mascons). The multi-author research group found out that while pre-impact target porosities of less than ~7% produce negative residual Bouguer anomalies, porosities greater than ~7% such as those of the Lunar regolith, produce positive anomalies (Milbury et al., 2015). Impact crater modeling on the icy satellites Ganymede and Europa (Bray et al., 2012) allowed Gareth and coworkers to estimate the thickness of the icy crust of these Jovian satellites. Together with F. Ciesla and his PhD student T. Davison, Gareth conducted a series of simulations to investigate the heating and melting of porous planetesimals and minor bodies upon hypervelocity collisions (Davison et al., 2010, 2012). Gareth also supports the recent InSight Mission (Daubar et al., 2018) and has detected some impact events based on their seismic signature. Major achievements of Kai Wünnemann include the modeling of oceanic impacts that are of eminent importance as 2/3 of the Earth is covered by water (Wünnemann & Lange, 2002). Together with his colleague Robert Weiss, Kai conducted pioneering work in modeling the generation, propagation, and shoaling of impact-generated tsunamis and published several landmark papers on this topic (Bahlburg et al., 2010; Weiss et al., 2006; Weiss & Wünnemann, 2007; Wünnemann et al., 2007, 2010; Wünnemann & Weiss, 2015), among them the modeling of the Eltanin oceanic impact event that took place in the Arctic Pacific Ocean (Weiss et al., 2015). Kai has been closely collaborating with field geologists to investigate terrestrial impact craters and, based on their findings and geophysical constraints, he has modeled various impact events numerically to achieve the best matching between nature and model. An important contribution was the numerical modeling of the formation of the Ries crater combining the iSALE and the SOVA hydrocodes to reproduce crater morphology, size, and composition and deposition of the ejecta. Two landmark papers led by the Barringer awardees Prof. D. Stöffler (1993) and Dr. N. Artemieva (2015) shed light on the formation of suevite (Artemieva et al., 2013; Stöffler et al., 2013). Moreover, he has investigated Carancas, Peru (Kenkmann et al., 2009a), Serra da Cangalha, Brazil (Vasconcelos et al., 2012), Morasko, Poland (Bronikowska et al., 2017), and Vista Alegre craters, Brazil (Vasconcelos et al., 2019). Prof. Wünnemann was also involved in the experimental impact cratering initiative MEMIN (2009–2018) (Kenkmann et al., 2018) as the principal investigator of its modeling part. He modeled the experimentally produced craters and used acoustic emissions of impact experiments to investigate the attenuation of shock waves and the seismicity of impact events (Güldemeister & Wünnemann, 2017; Moser et al., 2013). Scaling of experimentally formed craters is key for the application of the experimental results. Kai Wünnemann used the numerical codes as the principal tool to bridge the gap between experiment and nature (Güldemeister et al., 2015; Ormö et al., 2015; Prieur et al., 2017). A novel understanding of microstructures arose from his and his coworker's mesoscale models. He was able to simulate the heterogeneous distribution of shock pressures and temperatures at the grain scale that allowed us to understand shock effects in various minerals and rocks. Modeling led to the re-calibration of shock features in quartz at low shock pressures (Kowitz et al., 2013, 2016) and the quantification of the effect of porosity (Durr et al., 2012; Güldemeister et al., 2013). These mesoscale models were also used to understand the microstructure and heterogeneous distribution of shock effects in meteorites (Moreau et al., 2017, 2019). More recently, Kai Wünnemann switched the scale to focus on the role of impact bombardment in the late accretion history of the Moon (Marchi et al., 2013, 2014; Rolf et al., 2016; Zhu, Artemieva, et al., 2019; Zhu, Wünnemann, et al., 2019). Together with Menghua Zhu, he modeled giant, cataclysmic impact events and their influence on the thermal state of the early Moon (Zhu et al., 2017) and conducted systematic computational analyses to understand melt production and the formation of the lunar mega-regolith (Liu et al., 2019). Recently, both Gareth and Kai have been involved in the Impact Modeling Working Group of the DART-HERA mission of NASA and ESA. The rapid increase in newly discovered near-Earth asteroids document that asteroid impacts pose a real threat to the Earth. Gareth and Kai are the leading scientists to better understand the environmental effects of both, smaller, relatively frequent events and large, rare events (Morgan et al., 2022). For me, as a field structural geologist and experimentalist, the common work with Kai and Gareth has always been very educative, rewarding, and productive. I have learned so much on the mechanics of impact cratering from them and I really appreciated the excellent and intense collaboration and fruitful exchange between modelers and observers. Kai and Gareth have developed a new conference format to further improve the cooperation between modelers and observers and to understand each other better. The “Virtual Field Trip” at the Bridging the Gap III Conference in Freiburg, Germany, 2015, was designed in parallel to the “Ries crater field trip” and everyone got a chance to observe in person how capable impact crater models have become and what their limitations are. In turn, Gareth and Kai do also prove their theoretical concepts in the field. To conclude, Kai and Gareth together developed and applied the comprehensive computational tool iSALE to understand shock and impact phenomena at various scales ranging from the micro-scale to the mega-scale. With this universally applicable tool and its applications, they were able to push forward impact cratering studies extraordinarily. There is nobody that deserves the Barringer Award like these two awardees. I salute Kai and Gareth for their groundbreaking work that is key to understanding impact craters and that guides geologists! Congratulations to the 2022 Barringer Medal and Award. Open Access funding enabled and organized by Projekt DEAL. Data sharing not applicable—no new data generated, or the article describes entirely theoretical research.