- https://doi.org/10.1111/maps.13965
2022 Joint Barringer Medal for Kai Wünnemann and Gareth S. Collins
Translate Article 
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.
- Research Article
50 - 10.1016/j.icarus.2019.113430
- Oct 28, 2019
- Icarus
Troctolite 76535: A sample of the Moon's South Pole-Aitken basin?
- Book Chapter
- 10
- 10.1007/978-3-540-68778-8_3
- Jan 1, 2007
Currently about 170 impact craters are known on Earth; about one third of those structures are not exposed on the surface and can only be studied by geophysics or drilling. The impact origin of geological structures can only be confirmed by petrographic and geochemical studies; thus, it is of crucial importance to obtain samples of subsurface structures. In addition, structures that have surface exposures commonly require drilling and drill cores to obtain information of the subsurface structure, to provide ground-truth for geophysical studies, and to obtain samples of rock types not exposed at the surface. For many years, drilling of impact craters was rarely done in dedicated projects, mainly due to the high cost involved. Structures were most often drilled for reasons unrelated to their impact origin. In the former Soviet Union a number of impact structures were drilled for scientific reasons, but in most of these cases the curation and proper care of the cores was not guaranteed.More recently the International Continental Scientific Drilling Program (ICDP) has supported projects to study impact craters. The first ICDPsupported study of an impact structure was the drilling into the 200-kmdiameter, K-T boundary age, subsurface Chicxulub impact crater, Mexico, which occurred between December 2001 and February 2002. The core retrieved from the borehole Yaxcopoil-1, 60 km SSW from the center of the structure, reached a depth of 1511 m and intersected 100 m of impact melt breccia and suevite, which has been studied by an international team. From June to October 2004, the 10.5 km Bosumtwi crater, Ghana, was drilled within the framework of an ICDP project, to obtain a complete 1 million year paleoenvironmental record in an area for which only limited data exist, and to study the subsurface structure and crater fill of one of the best preserved large, young impact structures. From September to December 2005, the main part of another ICDP-funded drilling project was conducted, at the 85-km-diameter Chesapeake Bay impact structure, eastern USA, which involved drilling to a depth of 1.8 km. In 2008, it is likely that the El’ygytgyn structure (Arctic Russia) will be drilled as well. So far only few craters have been drilled — not enough to gain a broad understanding of impact crater formation processes and consequences.In this chapter we summarize the current status of scientific drilling at impact craters, and provide some guidance and suggestions about future drilling projects that are relevant for impact research. Points we cover include: what is the importance of studying impact craters and processes, why is it important to drill impact craters or impact crater lakes, which important questions can be answered by drilling, which craters would be good targets and why; is there anything about the impact process, or of impact relevance, that can be learned by drilling outside any craters; what goals should be set for the future; how important is collaboration between different scientific fields? In the following report, we first briefly discuss the importance of impact cratering, then summarize experience from past drilling projects (ICDP and others), and finally we try to look into the future of scientific drilling of impact structures.KeywordsImpact CraterImpact StructureDrilling ProjectCentral UpliftCrater FloorThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
- Research Article
- 10.1111/maps.13192
- Sep 24, 2018
- Meteoritics & Planetary Science
It is a great honor for us to deliver the citation for Prof. Dr. Thomas Kenkmann, a multitalented geologist, who has made remarkable scientific contributions in the field of impact geology over the last 20 years. With a background in structural geology, Thomas is one of the leading field geologists who has worked at numerous terrestrial impact structures making significant contributions to a better understanding of impact crater formation. However, considering Thomas just as an exceptionally talented field geologist falls way too short as he is also involved in laboratory impact cratering and shock wave experiments, remote sensing of terrestrial and extraterrestrial impact structures, microanalysis of impactites and shock features, experimental rock mechanics, and numerical modeling. This long list is probably still incomplete and we mention only those activities in which Thomas became a distinguished expert himself or where he initiated important developments by his particular ability to collaborate with colleagues of different scientific disciplines. Due to his extremely broad methodological background and his multidisciplinary approach, Thomas also continues to act as a bridge builder to close the gap between impact researchers using field observations, laboratory experiments, and numerical modeling to gain a better understanding of impact processes on Earth and other planets. Most scientists in the field of impact geology became involved in this topic early in their academic career, often already as M.Sc. or Ph.D. students. To our knowledge, Thomas was initially fascinated by tectonic structures on Earth and, coupled with his interest in architecture, he wanted to study how nature has created the given landforms on Earth—in fact, we always found it very inspiring to experience Thomas interpreting geological (impact) structures with the eyes of an architect. Like many other geologists, he initially did not consider the impact of cosmic bodies as an important geological process and, thus, he focused on tectonic processes as a student of geology at the University of Cologne and during his Ph.D. thesis at the GeoForschungsZentrum (GFZ) in Potsdam, Germany. It was Dieter Stöffler who recognized Thomas’s exceptional talent, and who got him interested in impact geology. In 1998, Thomas became part of Dieter's multidisciplinary research team at the Natural History Museum in Berlin, an experience which was certainly formative for Thomas’s holistic research philosophy later on in his career. Soon after, with his first publication (jointly with Boris Ivanov and Dieter Stöffler, both Barringer medalists) on faults in the basements of ancient impact structures, Thomas’s rapid rise into the ranks of the top researchers in impact geology began. Since then he has consistently made benchmark contributions based primarily on field work at numerous impact structures, as well as work coupled with numerical modeling, laboratory experiments, or remote sensing data of impact structures on Earth and Mars. Looking through the long list of papers, conference contributions, and popular scientific articles that Thomas has produced in only 20 years of research activity in this area, there is hardly any aspect of impact cratering and shock wave processes he has not dealt with. Among his numerous talents, Thomas is an outstanding field geologist and, speaking for myself (KW) as somebody who works mostly on the theoretical side, also an excellent field guide. I have been on several excursions with Thomas where he initiated vibrant discussions. He was able to put across his often highly innovative ideas to non–field experts, too. Furthermore, both students and colleagues alike who have joined him for fieldwork can account for his almost uncanny ability to recognize and unravel structures in the field, along with his general love of the outdoors. Early on in his impact cratering career, Thomas started to study the fault systems at impact structures (e.g., Ries crater, Germany; Upheaval Dome, USA) in order to reconstruct the mechanics of crater formation, especially the crater collapse and formation of central peaks. Over the years and through numerous field trips to different structures (e.g., Jebel Waqf as Suwwan, Jordan; Serra da Cangalha, Brazil; several impact craters in Australia and the United States), he started to notice deviations from circular geometry, which he interpreted as an indication of the direction of impact. Although his catalog of criteria for oblique impact is still debated, this example demonstrates Thomas’s exceptional ability to develop new ideas from detailed field mapping and observations serving as basis for the development of quantitative models that can be tested by computer models or laboratory experiments. Thomas has been active in both disciplines through collaboration with modelers and by initiating experimental campaigns. The impact modeling community owes a great deal to Thomas for inspiring modeling studies, many of which have led to the confirmation of processes that Thomas had suggested from observations ranging from the macroscale of terrestrial and extraterrestrial craters down to the microscale of specific shock features and the formation of shatter cones. Collaboration with Boris Ivanov, Natasha Artemieva, Alex Deutsch—all Barringer medalists—Gareth Collins, and my (KW) group has led to pioneering studies demonstrating how large-scale morphological characteristics and microscale shock metamorphic features can be linked to numerical modeling. While models are a satisfactory approach to account for the exceptional dynamics of impact cratering, they do not consider the heterogeneous nature of rocks. So it was a logical step for Thomas to become involved in laboratory impact experiments with natural and thus more complex materials. In a very early publication, he addressed the effect of heterogeneities on shock wave propagation using experiments to study the formation of local melts. Several years later, Thomas initiated the large “Multidisciplinary Experimental and Modeling Impact Research Network” (MEMIN) research unit of German impact researchers, where the very important aspect of rock heterogeneities on the entire impact process has been investigated in a quite holistic way. Thomas has been the speaker of this research unit since 2009, which has become a highly successful and productive research consortium in the field of impact research. In addition to his multiple research activities, Thomas has served the impact community by organizing two conferences (Large Meteorite Impacts III, Nördlingen, 2003; Bridging the Gap III, Freiburg, 2015), by editing four special volumes on impact cratering (GSA Special Paper No. 384, 2005—LMI; M&PS 48(1), 2013—MEMIN I; M&PS 52(7), 2017—BtG III; and the upcoming M&PS 53, 2018—MEMIN II), as a team leader of the ICDP deep drilling of the Chesapeake Bay impact structure, and as a reviewer of highly ranked journals and for international funding organizations. His dedication to impact cratering research was honored by the Governor of Utah (2009) for his work at the Upheaval Dome structure and by the Arab Union of Astrophysics and Astronomy for his work at the Waqf as Suwwan impact structure. Besides his outstanding abilities as a researcher, Thomas has also been an excellent teacher, Ph.D. supervisor, and promoter to the public. As curator of the impactites and petrographical and geological rock collections at the Natural History Museum in Berlin and of the ZERIN (Center of Ries Crater and Impact Research in Nördlingen) he was extensively involved in public outreach, he published several popular science articles, and he led the conception of an exhibition on earth science and impact cratering. In 2010, he was appointed professor and head of the Geology Department at the Albert-Ludwigs University Freiburg, Germany, honoring his scientific status and collaborative strength. His teaching talent was awarded by the Ministry of Science and Education of the federal state of Baden-Württemberg, especially for the student project “Screening Earth” to search for new impact craters. Numerous bachelor and master students have since experienced Thomas’s unbridled and youthful enthusiasm for teaching geology both in the classroom and in the field with sometimes rather unconventional methods. He has helped many young scientists to start their careers, several of which are now outstanding researchers in their own right. I (MHP) certainly would not be the researcher I am today without his ongoing support. We could carry on listing all the outstanding scientific achievements, skills, and services of Thomas, but the list would remain incomplete. Above all, we do want to emphasize that Thomas is one of the best colleagues and friends we have ever had in this business, and we owe Thomas special thanks for his friendship. His advice and support was vital in many projects we carried out together. Finally, we would like to thank all the colleagues who contributed to Thomas’s nomination. The enormous support speaks for the high reputation the awardee enjoys among the community. On behalf of all of them we sincerely congratulate Thomas on winning the Barringer Medal and Award.
- Report Component
- 8
- 10.3133/pp1688a
- Jan 1, 2005
- USGS professional paper
The late Eocene Chesapeake Bay impact structure on the Atlantic margin of Virginia is the largest known impact crater in the United States, and it may be the Earth's best preserved example of a large impact crater that formed on a predominantly siliciclastic continental shelf. The 85-kilometer-wide (53-mile wide) crater also coincides with a region of saline ground water. It has a profound influence on ground-water quality and flow in an area of urban growth. The USGS-NASA Langley corehole at Hampton, Va., is the first in a series of new coreholes being drilled in the crater, and it is the first corehole to penetrate the entire crater-fill sec tion and uppermost crystalline basement rock. The Langley corehole is located in the southwestern part of the crater's annu lar trough. A comprehensive effort to understand the crater's materials, architecture, geologic history, and formative processes, as well as its influence on ground water, includes the drilling of coreholes accompanied by high-resolution seismic-reflection and seismic-refraction surveys, audio-magnetotelluric surveys, and related multidisciplinary research. The studies of the core presented in this volume provide detailed information on the outer part of the crater, including the crystalline basement, the overlying impact-modified and impact-generated sediments (physical geology, paleontology, shocked minerals, and crystalline ejecta), and the upper Eocene to Quaternary postimpact sedimentary section (stratigraphy, paleontology, and paleoenvironments). The USGS-NASA Langley corehole has a total depth below land surface of 635.1 meters (m; 2,083.8 feet (ft)). The deepest unit in the corehole is the Neoproterozoic Langley Granite. The top of this granite at 626.3 m (2,054.7 ft) depth is overlain by 390.6 m (1,281.6 ft) of impact-modified and impact-generated siliciclastic sediments. These crater-fill materials are preserved beneath a 235.6-m-thick (773.12-ft-thick) blanket of postimpact sediments. A high-resolution seismic-reflection and seismic-refraction profile that crosses the Langley drill site is tied to the core by borehole geophysical logs, and it reveals the details of extensional collapse structures in the western annular trough. Electrical cross sections based on audio-magnetotelluric (AMT) soundings image a nearly vertical zone of high resistivity at the outer margin of the annular trough, possibly indicating fresh ground water at that location, and they show impedance trends that match the curvature of the structure. They also image the subsurface contact between conductive sediments and resistive crystalline basement, showing that the depth to crystalline basement is relatively constant in the western part of the annular trough. Chemical and isotopic data indicate that saline ground water of the Virginia inland saltwater wedge or bulge is a mixture of freshwater and seawater, and evidence for a mixing zone at the crater's outer margin supports the concept of differential flushing of residual seawater to create the bulge. Ground-water brine in the central part of the crater was produced by evaporation, and brine production from the heat of the impact is at least theoretically possible.
- Research Article
- 74
- 10.1016/j.chemer.2004.10.003
- Dec 30, 2004
- Geochemistry
Hypervelocity collisions into continental crust composed of sediments and an underlying crystalline basement: comparing the Ries (∼24 km) and Chicxulub (∼180 km) impact craters
- Research Article
- 10.1088/1742-6596/2145/1/012051
- Dec 1, 2021
- Journal of Physics: Conference Series
During impact events, planetary crusts experience high pressures that can impart rocks with shock remanent magnetisation (SRM) if an ambient magnetic field or demagnetise rocks if a field is absent. If rocks experience substantial impact heating or are pressurised above ~40 GPa (inducing melting and recrystallisation) they may instead record a thermo-viscous remanent magnetisation (TVRM) as they cool below their Curie temperatures. Understanding impact re-magnetisation is crucial for studying terrestrial impact craters, but also unraveling the history of long-lived core dynamo fields on other planetary bodies. In this research we studied impact-related re-magnetisation recorded in natural rock samples from the Chesapeake Bay impact crater, Virginia. As a case study, here we discuss the natural remanent magnetisation (NRM) of two samples of different rock types: a suevite (sample I9-UI, depth 1.40 km beneath the ground) and a schist (sample S32, depth 1.67 km beneath the ground) using thermal and alternating field demagnetisation. The suevite represents a sample that contains material that experience impact remelting, whereas the schist represents an unmelted rock. From the NRM spectra, we found that the sample ITH9-UI was remagnetised by TVRM due to impact-related heating, while the sample STH32 shows the indication of shock deformation of magnetic minerals.
- Research Article
- 10.1016/j.epsl.2025.119542
- Oct 1, 2025
- Earth and Planetary Science Letters
Subsurface structure of a buried Eratosthenian crater on the far-side of the Moon
- Preprint Article
- 10.5194/epsc2024-491
- Jul 3, 2024
Introduction:  The composition and provenance of the materials in South Pole - Aitken Basin (SPA) on southern farside is essential to a number of unresolved science questions relevant to lunar and solar system evolution. The Chang’E-4 mission is the first landed mission to this unexplored region, which provide a unique chance to further constrain the composition and provenance of the lunar interior [1].There is still controversy about the composition and provenance of materials in Chang 'e-4 landing site [1-7]. The first spectral interpretation results based on the Modified Gaussian Model (MGM) indicate that the landing site is dominated by Low-Ca Pyroxene (LCP) and olivine, which may represent deep-seated materials potentially from the lunar mantle, delivered to the Chang’E-4 landing site by ejecta from the Finsen crater [1-3]. The Hapke model was also used to infer the minerals and glasses’ abundances, which indicated that the landing site is dominated by plagioclase and lesser amount of mafic minerals [4-6]. Other study suggests that the composition of the landing site is still dominated by mare materials, which may be excavated and delivered by Zhinyu Crater [7].The Yutu-2 rover has been exploring on the lunar surface for more than 60 lunar days, lots of in-situ spectra have been obtained, we will use these in-situ spectral data, orbiting spectral data (M3) and Apollo lunar soils' spectral data in the laboratory to perform a detailed survey on the composition and provenance  of materials on the Yutu-2 rover tranverse.Data and methods: Over 60 lunar days’ data of the Visible and Near-Infrared Imaging Spectrometer (VNIS) on the Yutu-2 lunar rover and the orbiting spectral data of the Moon Mineralogical Mapper (M3) are used. The VNIS data have been processed by dark current subtraction, flat field and instrument temperature correction, radiometric correction, reflectance calculation and spectral smoothing [1], etc. After deducting some data affected by terrain shadows and scattered light, a total of 131 spectral data of lunar soils were selected. For M3 data, the spectral data of some fresh impact craters in the ejecta area of Finsen impact crater and the inner area of Zhinyu impact crater are selected. The location and spectral curves of M3 data are shown in Figure 1. Besides, the spectral data of lunar soils (mare and highland) obtained by Relab are also used.Figure 1: The location of typical spectra of the selected M3 data. a) the spectral data locations of the fresh impact craters selected along the wall of Finsen impact crater (points A and B) and along the direction of ejecta (points C-G), H point located in side of Zhinyu impact crater. b) Typical spectral curves of the selected M3.Results and discussion:  We firstly calculated the absorption bands of VNIS, M3 and Relab data at ~1μm and ~2μm, the results show that the absorption bands of VNIS at ~1μm and ~2μm are different from M3 and RELAB data (Figure 2). The absorption bands of VNIS at ~1μm are mainly concentrated in the range of 0.95~1.0μm, while the absorption bands at ~2μm are mainly concentrated in the range of 1.95~2.1μm. The absorption bands of VNIS at 2μm is lower than that of the M3’s H point in the Zhiyu impact crater, and is closer or even shorter than that of M3’s A~G points in the Finsen impact ejecta. However, the absorption bands of VNIS at ~1μm is significantly higher than that of Finsen impact ejecta (A~G points) and Zhinyu impact crater (H points). The ~2μm absorption bands results indicate that the composition of the Chang 'e-4 landing site may be closer to the impact ejecta of Finsen crater, but the  ~1μm absorption bands results are different from that of the impact ejecta of Finsen crater. In order to further constrain the composition, the ~1μm asymmetry parameters are also calculated [8], and the results indicate that the Chang 'e-4 landing site may be rich in olivine or glass components (Figure 3).Figure2: Plot of the absorption bands of VNIS, M3 and Relab spectral data at ~1μm and ~2μm. a) The black data points are VNIS spectral data, and the color data points are M3 spectral data selected in the ejecta direction of Finsen impact crater and Bajie / Zhinyu impact crater.Figure 3: Plot of the ~1μm asymmetry of VNIS. The black data points are VNIS spectral data.
- Research Article
- 1
- 10.1111/maps.13419
- Nov 28, 2019
- Meteoritics & Planetary Science
Conference report: Large Meteorite Impacts and Planetary Evolution VI
- Research Article
- 1
- 10.1029/2023je008006
- Mar 1, 2024
- Journal of Geophysical Research: Planets
Research on the lithospheric elastic thickness (Te) of lunar mascon basins can provide a deeper understanding of heterogeneous thermal activity. In this study, we focused on four basins (Moscoviense, Freundlich‐Sharonov, Hertzsprung, and Apollo) located on the far side of the Moon. These basins exhibit a significant variation in admittance and correlation spectra, making it challenging to develop precise fitted models. Based on the global lunar crustal thickness model and mare basalt thickness, we developed a mantle and mare basalt load model to estimate the Te. This small Te (10.1 km) suggests a double impact process or extreme thermal activity caused by volcanism during the formation of the Moscoviense. For the typical highland basins, that is, Freundlich‐Sharonov and Hertzsprung, the Te (∼20 km) corresponds to a minimum heat flux of 34 mW m−2. Considering the additional energy introduced by the impact, this heat flux can be considered as the upper limit for the heat flux of the highland itself during the formation of a mascon basin. For the Apollo basin within the South Pole‐Aitken (SPA) terrane, the Te is 30.7 km. The crust beneath the SPA region is thinned, allowing a greater contribution of stiffer mantle material to the lithosphere, perhaps explaining the higher effective Te. Furthermore, the disparity between the highland and SPA terranes can give rise to their distinct basin formation processes. Impact basins formed within the SPA terrane may have experienced a faster cooling process compared to those formed on the highland terrane following the impact event, leading to a higher Te.
- Research Article
- 18
- 10.1016/j.icarus.2014.07.030
- Aug 20, 2014
- Icarus
Volcanism on farside of the Moon: New evidence from Antoniadi in South Pole Aitken basin
- Research Article
- 3
- 10.1111/maps.13804
- Mar 29, 2022
- Meteoritics & Planetary Science
Among all geophysical methods, gamma ray spectrometry is not widely used in impact cratering studies, despite its efficiency in the investigation of physical/chemical changes in rocks. The application of gamma ray spectrometry method to data from the Maâdna crater is aimed at detection and verification of the presumed impact‐derived melt rocks or breccias, as well as discussing its implications on process of formation. The resulting information also demonstrates the potential of these specific data regarding our general understanding of impact cratering, while a few case studies have been reported in the literature to date within the impact community. Maâdna crater is dated at 2.6–3.1 Ma of ~1.7 km and is emplaced in Upper‐Cretaceous to Eocene limestones of the northern part of the Algerian Saharan platform. Although originally accepted as an impact crater, its origin is still controversial. Several thousands of field measurements were taken using a field portable gamma ray spectrometer. The measurements can be equivalently expressed by up to about 42 km footpath recordings in real‐time ground acquisitions, covering the entire structure and surrounding areas beyond the crater edge. The collected data included the total count (Tc) and the concentrations of the radionuclides calculated in wt% for K and in ppm for U and Th. The spectra rates recorded inside and outside the crater did not exceed the maximum average concentrations corresponding to 75.3 Cps, 4.94 ppm, 10.5 ppm, and 1.79 wt% for Tc, U, Th, and K, respectively. The database was processed using various gridding data methods, from which the minimum curvature was adopted as it provides a powerful visualization and interpretation of the anomalous distribution of radioactive elements and their corresponding ratios maps. In addition, an improved statistical analysis was carried out in order to extract a maximum of information about the radiometric response of each rock unit. This analysis consisted of a series of multiple linear regression, mean differencing, Q–Q (quantile–quantile) plots, and ternary mapping. Maps and plots of various models allowed us to examine the background variability in the distribution of K, Th, and U concentrations at the surface of the three distinctive litho‐type zones in the surveyed area, which are the central part, the crater edge, and the outside of the crater including the wadi deposits. Observed results of different radiometric responses clearly reflect the effect of various lithological units, especially in the areas with high K concentration. Note that this positive K‐anomaly has been observed in recent deposits that fill the Maâdna depression or external wadi beds. In contrast, the surrounding limestone rocks showed lower levels of radioelement concentrations. Relevant similarities found between the radiometric signatures of the Neogene formations inside and outside the crater can be considered as a strong argument to exclude preferential radionuclides enrichment caused by an impact event. Consequently, the natural origin of radioactive sources can be easily explained. Compared to other radiometric signatures documented on proven impact structures, the Maâdna structure has been notably discussed in the context of a diapiric hypothesis rather than a meteoritic one. Moreover, the methods used here contribute to our knowledge of the regional sedimentary history in terms of natural radioactivity.
- Research Article
- 1
- 10.1029/2024je008535
- Dec 1, 2024
- Journal of Geophysical Research. Planets
Impact cratering is one of the fundamental processes throughout the history of the Solar System. The formation of new impact craters on planetary bodies has been observed with repeat images from orbiting satellites. However, the time gap between images is often large enough to preclude detailed analysis of smaller‐scale features such as secondary impact craters, which are often removed or buried over a short time period. Here we use a seismic event detected on Mars by the NASA InSight mission to investigate secondary cratering at a new impact crater. We strengthen the case that the seismic event that occurred on Sol 1034 (S1034a) is the result of a new impact cratering event. Using the exact timing of this event from InSight, we investigated the resulting new impact crater in orbital image data. The S1034a impact crater is approximately 9 m in diameter but is responsible for over 900 secondary impact events in the form of low albedo spots that are located at distances of up to almost 7 km from the primary crater. We suggest that the low albedo spots formed from relatively low energy ejecta, with individual ejecta block velocities less than 200 m s−1. We estimate that the low albedo spots, the main evidence of secondary impact processes at this new impact event, fade within 200–300 days after formation.
- Research Article
- 6
- 10.1016/j.icarus.2024.116329
- Sep 20, 2024
- Icarus
Chandrayaan-3 landing site evolution by South Pole-Aitken basin and other impact craters
- Research Article
- 6
- 10.1016/j.icarus.2023.115723
- Jul 26, 2023
- Icarus
Evidence for trail forming ejecta boulder falls around fresh simple impact craters at the lunar Orientale multi-ring basin and implications for ballistic ejecta sedimentation on the Moon
Save Important notes in documents
Highlight text to save as a note, or write notes directly
You can also access these Documents in Paperpal, our AI writing tool
Powered by our AI Writing Assistant
