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The Charity Shoal structure is a circular, ∼1.2‐km‐diameter, bedrock‐rimmed shoal in eastern Lake Ontario with a ∼20‐m‐deep central basin. The structure has been proposed as a possible Middle Ordovician impact crater or volcanic intrusion. We conducted marine seismic and magnetic surveys (9‐km2) and 3‐D geophysical modeling to better resolve the Charity Shoal subsurface geology and possible origins. Three models were evaluated: (a) a buried (>450 m) impact structure in Mesoproterozoic basement, (b) a maar‐diatreme, (c) a cylindrical, zoned volcanic plug. Seismic profiles and multi‐beam bathymetry revealed >30 m of Quaternary sediments overlying Middle Ordovician (Trenton Group) carbonate bedrock and complex, 3‐dimensional folding and faulting of the structure rim. Magnetic surveys recorded an annular magnetic high (>600 nT) over the structure rim and a central magnetic low (∼500–600 nT) coincident with a ∼−1.7 mGal Bouguer gravity anomaly. The continuity of Trenton Group strata in seismic profiles rules out a previously proposed Mesozoic maar‐diatreme intruded into Paleozoic strata. The zoned volcanic plug model reproduced the annular magnetic anomaly but was incompatible with Bouguer gravity profiles. The magnetic anomaly was best reproduced by a simple impact structure seated in Mesoproterozoic basement at 450–500 m depth with a rim‐to‐rim diameter of ∼1.2 km and rim height of ∼10–20 m. A 100‐m wide and 50‐m‐deep channel in the Mesoproterozoic basement may record fluvial dissection of the southwestern rim. A buried (>450 m), simple impact crater is most compatible with all available geophysical data at Charity Shoal. Plain Language Summary: The Charity Shoal structure is 1.2‐km‐diameter, circular bedrock‐rimmed shoal on the lakebed of eastern Lake Ontario. The crater‐like structure has been investigated in three previous studies (Holcombe et al., 2001, https://doi.org/10.1016/s0380‐1330(01)70664‐8; Holcombe et al., 2013, https://doi.org/10.1007/s00367‐013‐0322‐6; Suttak, 2013, http://hdl.handle.net/11375/13532) and proposed as a possible karst sinkhole, glacial erosional feature, volcanic intrusion or meteorite impact crater. We conducted geophysical surveys and 3‐D modeling at Charity Shoal to evaluate several possible geological origins. An impact crater model was most compatible with the available geophysical data, which indicate a deeply buried "crater‐form" structure in the Precambrian basement at a depth of >450 m. Our geophysical results rule out a proposed impact crater within the Middle Ordovician sedimentary rocks, as that model cannot reproduce the large gravity and magnetic anomalies recorded at Charity Shoal. Key Points: Charity Shoal is a 1.2 km diameter, crater‐like bedrock shoal in northeastern Lake Ontario previously proposed as a Middle Ordovician impact structure or maar‐diatreme3‐D subsurface modeling of magnetic, seismic, and gravity data indicates a deep‐seated (>450 m) crater‐form structure in Mesoproterozoic basementGeophysical modeling supports a probable origin as a Mesoproterozoic‐early Paleozoic simple impact structure [ABSTRACT FROM AUTHOR]

When Peter Millman, an astronomer at the Dominion Observatory in Ottawa, read Ralph Baldwin's 1949 book The Face of the Moon, he excitedly brought it to the attention of the Observatory's recently-appointed Director, Carlyle Beals. Baldwin's book argued that the Moon's numerous circular features were not of volcanic origin, but were due to meteorite impacts, and that the Earth should similarly have an abundance of meteorite impact scars. Beals and Millman decided to test Baldwin's arguments, and Beals initiated an innovative program at the Observatory to search for meteorite craters on the Canadian Shield. By the mid-1960s, ten craters had been discovered in Canada. Today, 190 meteorite craters have been confirmed worldwide, with nearly one-sixth of them in Canada. Investigations of the Canadian craters, employing gravity, magnetic, seismic, and diamond drilling studies, became a model for all future crater studies, and brought international attention to Canadian scientists. [ABSTRACT FROM AUTHOR]

This paper investigates the directional distribution of extraterrestrial objects (meteors, fireballs) impacting Earth's surface and forming craters. It also introduces a novel directional statistical mixture model to analyze their falls, validated through rigorous testing. First, we address whether these falls follow non-uniform directional patterns by explicitly employing directional statistical tools for analysing such data. Using projection techniques for longitude and latitude and more importantly, a general spherical statistical approach, we statistically investigate the suitability of the von Mises distribution and its spherical version, the von Mises–Fisher distribution, (a maximum entropy distribution for directional data). Moreover, leveraging extensive data sets encompassing meteor falls, fireball showers, and craters, we propose and validate a novel mixture von Mises–Fisher model for comprehensively analysing extraterrestrial object falls. Our study reveals distinct statistical characteristics across data sets: fireball falls exhibit non-uniformity, while meteor craters suggest a potential for both uniform and von Mises distributions with a preference for the latter after further refinement. Meteor landings deviate from a single-directional maximum entropic distribution; we demonstrate the effectiveness of an optimal 13-component mixture von Mises–Fisher distribution for accurate modelling. Similar analyses resulted in 3- and 6-component partitions for fireball and crater data sets. This research presents valuable insights into the spatial patterns and directional statistical distribution models governing extraterrestrial objects' fall on Earth, useful for various future works. [ABSTRACT FROM AUTHOR]

At present, there are still many meteorite craters and boulders on the surface of Mars and the Moon that cannot be accessed by existing planetary exploration robots. To provide a solution to this issue, this paper proposes a four-link rocker-suspension planetary exploration robot that combines both the reliability and low complexity of wheeled rovers with competent terrain adaptability and obstacle-crossing performance. Relying on its special differential pitch device, the robot can adapt to fluctuations in terrain by using both active and passive modes. Moreover, the four-link rocker suspensions on both sides of the robot can increase the instantaneous rotation radius of the rockers when the robot climbs over obstacles. In this paper, using modelling and simulations, we demonstrate that the four-link rocker suspension can improve the robot's obstacle-crossing capability. The geometric and static conditions required for the robot to cross obstacles are derived and discussed, and numerical simulations are conducted to identify the maximum obstacle-crossing heights that satisfy different conditions. Finally, a physical prototype of the robot is developed. [ABSTRACT FROM AUTHOR]

We provide new support for habitable microenvironments in the near-subsurface of Mars, hosted in Fe- and Mg-rich rock units, and present a list of minerals that can serve as indicators of specific water–rock reactions in recent geologic paleohabitats for follow-on study. We modeled, using a thermodynamic basis without selective phase suppression, the reactions of published Martian meteorites and Jezero Crater igneous rock compositions and reasonable planetary waters (saline, alkaline waters) using Geochemist's Workbench Ver. 12.0. Solid-phase inputs were meteorite compositions for ALH 77005, Nakhla, and Chassigny, and two rock units from the Mars 2020 Perseverance rover sites, Máaz and Séítah. Six plausible Martian groundwater types [NaClO4, Mg(ClO4)2, Ca(ClO4)2, Mg-Na2(ClO4)2, Ca-Na2(ClO4)2, Mg-Ca(ClO4)2] and a unique Mars soil-water analog solution (dilute saline solution) named "Rosy Red", related to the Phoenix Lander mission, were the aqueous-phase inputs. Geophysical conditions were tuned to near-subsurface Mars (100 °C or 373.15 K, associated with residual heat from a magmatic system, impact event, or a concentration of radionuclides, and 101.3 kPa, similar to <10 m depth). Mineral products were dominated by phyllosilicates such as serpentine-group minerals in most reaction paths, but differed in some important indicator minerals. Modeled products varied in physicochemical properties (pH, Eh, conductivity), major ion activities, and related gas fugacities, with different ecological implications. The microbial habitability of pore spaces in subsurface groundwater percolation systems was interrogated at equilibrium in a thermodynamic framework, based on Gibbs Free Energy Minimization. Models run with the Chassigny meteorite produced the overall highest H2 fugacity. Models reliant on the Rosy Red soil-water analog produced the highest sustained CH4 fugacity (maximum values observed for reactant ALH 77005). In general, Chassigny meteorite protoliths produced the best yield regarding Gibbs Free Energy, from an astrobiological perspective. Occurrences of serpentine and saponite across models are key: these minerals have been observed using CRISM spectral data, and their formation via serpentinization would be consistent with geologically recent-past H2 and CH4 production and sustained energy sources for microbial life. We list index minerals to be used as diagnostic for paleo water–rock models that could have supported geologically recent-past microbial activity, and suggest their application as criteria for future astrobiology study-site selections. [ABSTRACT FROM AUTHOR]

The concentric impact rings of the Vredefort Crater contain rocks with elevated uranium concentrations resulting from the geological signature of a meteoric impact. The decay of this uranium was estimated to lead to elevated indoor radon concentrations in the Crater, but such a study has never been carried out. This study explores the relationship between the natural radionuclides i-0found in the geology of the Vredefort Crater and indoor radon concentrations. This was achieved through soil sampling and radionuclide surveys conducted on three impact rings, supplemented by indoor radon measurements in dwellings found in the area. In situ measurements revealed that one impact ring had higher-than-average uranium concentrations at 50 Bq/kg. Surprisingly, the measured indoor radon levels were lower than expected (113 Bq/m3). These measurements were taken during the COVID-19 pandemic and colder months, conditions that would typically result in elevated indoor radon levels. Soil samples indicated uranium activity of 30 Bq/kg, comparable to the world average of 35 Bq/kg. However, defunct mine tunnels in the area exhibited elevated radon concentrations, averaging 364 Bq/m3. The disparity between expected and measured indoor radon levels was attributed to the composition of surficial deposits, bedrock, and architectural features of the dwellings preventing radon accumulation. [ABSTRACT FROM AUTHOR]

Jeptha Knob is a deformed structure, 4.5 km in diameter, composed entirely of carbonate rocks in the stable craton of North America. At Jeptha Knob, conventional evidence of meteorite impact, shock metamorphism, has not been found. I used calcite twin analysis to test the hypothesis that Jeptha Knob is a meteorite impact crater. Calcite twinning gives differential stresses of >170 MPa in rocks that were 600 to ≈800 m below the surface when the rocks were deformed. Under these conditions, high differential stresses cannot be explained by tectonic processes. In addition, twin intensities are >150 twins/mm which are >50% higher than the highest twin intensities observed in limestone from a wide variety of tectonic settings. Twin intensities and differential stresses are the same magnitudes as those found at Serpent Mound, a proven impact structure. Consistent with meteorite impact, differential stresses increase toward the center of the structure. If one accepts that Jeptha Knob is a marine impact crater, then (1) the presence of high temperature (>250°C) thick twins in calcite from a resurge deposit; (2) the extensive dolomitization of the central uplift with water/rock ratios >1.0; and (3) two episodes of calcite twin recorded incremental strains, are explained. [ABSTRACT FROM AUTHOR]

Landing on small-bodies is a very challenging problem that requires high degrees of robustness and autonomy. Being able to perform simulations with great flexibility and accuracy is paramount for the development and design of landing systems. To this end, contact dynamics plays a fundamental role and is often handled by complex tools that require large amount of development and validation efforts and very specific expertise. In the last decade, the Visual Effects (VFX) industry has developed numerous suites that deal with contact dynamics frameworks. In this work, the possibility of leveraging on the work of the VFX industry by using Blender, one of these tools, as the source for the contact dynamics modelling is investigated. This research focuses on the description of the methodology used for the landing simulations and the validation of the tool developed. A step-by-step guide through the simulation setup is given, discussing how the wrapping GNC simulator and Blender interact. Validation tests for the different parameters and dynamic models involved in the simulations are also presented. The results refer to the landing of a CubeSat in the crater region of an asteroid. In particular, the artificial crater that will be generated on Dimorphos by NASA's DART impact in late September 2022, is considered in the simulations presented in this work. Safety maps are generated by post-processing these results, and are used to assess different landing strategies or site-selection criteria on the Dimorphos crater study case. Finally, the role of the developed tool in optimising the use of space resources and its contribution to landing design strategies is discussed. [ABSTRACT FROM AUTHOR]

Ultrahigh-pressure high-temperature glasses are characterized by unusual structural and phase aspects that require closer investigation in order to elucidate their physical properties and the possibility of using innovative materials as prototypes. Experimental modeling of an impact process in laboratory conditions makes it possible to shed light on the nature of phase transformations on impacto-genesis. Impact glasses were obtained experimentally by melting the aluminosilicate and quartz components of the rocks of the target of the Kara astro-problem at pressure about 90 GPa and temperature about 7000°C. Investigations have shown that as a result of extreme external conditions, glasses of a specific composition are formed containing a high proportion of Ca and carbon. Thus, the results obtained indicate the possibility of obtaining glass of wide compositions, including carbon-containing glass, which can be used for further research in order to develop new materials and technologies for their production. [ABSTRACT FROM AUTHOR]

Eugene (also spelled Yevgeniy or Evgeny) Gurov (Figure 1) was born in Kharkov, Ukrainian SSR, on March 24, 1934. 10th Lunar and Planetary Science Conference, pp. 479 - 81. 22 Gurov, E. P., Valter, A. A., Gurova, E. P., and Serebrennikov, A. I. 1978. The geological structure of the crater rim was described by Gurov and Gurova ([4]) and Gurov and Yamnichenko ([23]); see also Gurov et al. ([16]). 21 Gurov, E. P., Valter, A. A., Gurova, E. P., and Kotlovskaya, F. I. 1979. [Extracted from the article]

The basal contact of the Sudbury Igneous Complex (SIC) on the North Range is interpreted as the outer edge of a meteorite impact crater. Yet, the base of the SIC, and contacts within the SIC, and the overlying Onaping are not circular. Their outline is elliptical. This and other details of the geology of the North Range which have not been fully explained include variations in the width of the metamorphic contact aureole, lateral discontinuous variations in the thickness of the norite and granophyre units, paleomagnetic evidence that the North Range contact of the SIC originally had a dip of around 20°, and differing magnetic fabrics in the norite/gabbro versus the granophyre. Several metrics are used to determine how much of the current outline of the North Range is the result of post-impact deformation and how much is a primary feature related to a meteorite impact. Uplift, rotation, and translation experienced by different segments of the North Range of the SIC are established using dyke azimuth and petrographic analysis of Matachewan diabase dykes, and paleomagnetic and magnetic fabric data analysis. These analyses show (a) the elliptical form of the North Range is a primary feature associated with a near-circular impact crater, (b) some of the original crater wall must have been preserved, and (c) deformation of the North Range is limited to regional scale block rotation producing a southwest dip modified by minor block rotation tilting and vertical displacement associated with north–northwest-trending faults. [ABSTRACT FROM AUTHOR]

Wispy Terrain, with its chasmata, is one of the enigmatic regions of Dione. It consists of quasi-parallel graben, and troughs, in parts with horsts, indicating extensional and shear stresses. This study introduces some observations of compression-related features and proposes a new regional formation model. The study of the relationship between impact craters and tectonic features revealed certain "lost" parts of some crosscut craters, indicating additional cryotectonic features, the appearance of accretionary prism-like phenomena, and, theoretically, subsumption-like processes. This study provides new information about the surface renewal processes at one of the youngest and probably still active regions of Dione. [ABSTRACT FROM AUTHOR]

The release and transformation mechanism of residual stress contributes to the improvement of metal materials' processing and performance, enhancing their structural stability, surface integrity, and fracture resistance. This paper focuses on the Ultrasonic Impact Treatment-Solid Particle Entrainment by Waterjet (UIT-SPEWJ) composite surface modification of 7075-T6 aluminum alloy, investigating the effects of UIT-SPEWJ process parameters (jet pressure and target distance) on the alloy's surface quality, roughness, microhardness, residual stress, and the evolution mechanism of microstructure. The results indicate that the 7075-T6 aluminum alloy modified by UIT-SPEWJ mainly exhibits a "meteorite crater" effect, accompanied by significant smearing and ploughing phenomena. Surface roughness shows a trend of first decreasing and then increasing with the rise of jet pressure and target distance. The minimum surface roughness, 0.852 μm, is achieved at a jet pressure of 25 MPa and a target distance of 7.5 mm. The microhardness of the samples modified by UIT-SPEWJ gradually decreases from the surface to the substrate with increasing depth. The hardened layer depths of the samples UIT-SPEWJ-1–6 after modification are approximately 174 μm, 226 μm, 200 μm, 196 μm, 176 μm, and 172 μm, respectively. After UIT, SPEWJ, and UIT-SPEWJ surface modifications, the surface of 7075-T6 aluminum alloy mainly exhibits compressive residual stress (CRS). The surface residual stress σ_srs of samples modified by UIT and SPEWJ are approximately 195.161 and 215.752 MPa, respectively. The surface residual stresses of UIT-SPEWJ-1–6 samples are significantly improved to 277.089, 529.499, 393.615, 459.261, 368.084, and 220.635 MPa, respectively, with UIT-SPEWJ-2 sample having the highest surface residual stress, which is 2.7 and 2.4 times that of UIT and SPEWJ modified surfaces. Samples modified by UIT-SPEWJ present significant dislocation phenomena, and the precipitated phases mainly include the needle-like metastable phase η', as well as the equilibrium phase η (MgZn 2) with a rod-like structure. At lower jet pressures and larger target distances, the 7075-T6 aluminum alloy exhibits a continuous PFZ with a size of approximately 12–23 nm. As jet pressure increases and target distance decreases, discontinuous grain boundary precipitate bands appear, sized around 8–17 nm. Moreover, when the jet pressure is 25 MPa and the target distance is 7.5 mm, the grain boundary precipitated phases are more dispersed. • The synergistic strengthening mechanism of ultrasonic impact and water jet is studied. • The release and transformation mechanism of residual stress induced by ultrasonic impact during jet strengthening process are analyzed. • The microstructure evolution mechanism under the composite strengthening process was studied. [ABSTRACT FROM AUTHOR]

The paper presents the characteristics of impact diamonds from the Popigai meteorite crater, formed by martensite transformation of graphite-bearing gneisses due to meteorite impacts. These diamonds have a nanopolycrystalline structure and consist of two phases, i.e., cubic (diamond) and hexagonal (lonsdaleite). They are distinguished by phenomenal abrasion resistance, on average twice as high as the abrasion resistance of single-crystalline diamonds. The work considers the possibility of producing similar diamonds by explosion. It is noted that diamonds, which are most similar in structure, are produced through exploding a composition of graphite and hexogen; lonsdaleite is present in the material obtained in this way. However, in any case, diamonds produced by explosion are very small in size, incomparable with natural ones. [ABSTRACT FROM AUTHOR]

Compared to intensive research on km‐sized meteorite impact craters, fewer studies focus on smaller craters. The small craters are often hard or impossible to recognize using "classical" criteria like the presence of shatter cones, shocked quartz, and geochemical indicators. Therefore, a long list of candidate structures awaiting approval/disapproval of their origin has been formed over the last decades. One of them is the Tor structure in central Sweden. To test a hypothesis of an impact origin of this structure, we have performed topographical analysis, geophysical studies, 10Be exposure dating of boulders, and 14C dating of Tor‐associated charcoal. None of the methods gave us a reason to claim the Tor structure is of impact origin. Thus, we support a recently suggested idea of Tor being formed by a grounded iceberg within a glacial lake. [ABSTRACT FROM AUTHOR]

The frequency of crater-producing asteroid impacts on Earth is not known. Of the predicted Holocene asteroid impact craters of <200 m diameter, only -30% have been located. Until now there has been no way to distinguish them from "normal" terrestrial structures unless pieces of iron meteorites were found nearby. We show that the reflective properties of charcoal found in the proximal ejecta of small impact craters are distinct from those produced by wildfires. Impact-produced charcoals and wildfire charcoals must derive from different heating regimes. We suggest that charcoal with specific reflective properties may help to recognize the meteoritic origin of small craters. [ABSTRACT FROM AUTHOR]

The data on the concentrations of major and trace elements, including platinum group elements (PGE) and Re, in suevite samples collected in different parts of the Popigai meteorite crater are reported. The suevite studied shows the identity of the bulk composition; gneiss of the Anabar Shield is identified as the protolith. It was found that the total concentrations of PGEs in suevite are not uniform: they decrease successively in the samples from the western to the southern, and further to the eastern part of the crater. The results of this study showed that the enrichment of suevite on PGEs is a characteristic of meteoritic contamination and is not associated with either crustal or mantle rocks of mafic or ultramafic composition. [ABSTRACT FROM AUTHOR]

The paradigm of plate tectonics has aided in the identification of the journey of continents on the globe, their assembly into supercontinents, disruption, and re‐assembly. Here, we use meteorite impact craters as proxies for tracking the voyage of lithospheric plates. Employing the provisions in GPlates, an interactive geographic information system‐based plate tectonic reconstruction model, we were able to identify the palaeo‐position, and velocity of the 174 terrestrial impact craters, formed after 1,100 Ma, across the globe. These parameters of craters were evaluated for independent tectonic plates and were correlated with global tectonic events. For example, the similarity in the velocity of Beaverhead (900 Ma) and Holleford (550 Ma) craters since 550 Ma is traced to the connection between the Eastern Basin and North America Craton commencing 1,100 Ma, and through the South Basin and Range. Likewise, the drastic reduction in the velocity of Spider Crater (700 Ma) in Australia after 600 Ma can be attributed to the subduction between east and west Gondwana. The accelerated motion of the Indian Plate at 63 Ma, when the lithosphere was hovering over the Réunion hotspot, is also explained. With the advent of more improved plate tectonic models and the discovery of more impact craters, improvised interpretations will be possible. [ABSTRACT FROM AUTHOR]

The JAXA Hayabusa2 mission accomplished the formation of an artificial crater on the asteroid Ryugu. The aim of this work is to analyse the area surrounding the artificial crater and reveal spectral variability compared to the same region before the crater formation, to mineralogically and physically characterize the subsurface exposed material. The crater's investigation focused on the analysis of two regions corresponding to the inner part of crater (the pit and the crater wall/floor), two areas related to ejecta deposited close to the crater, two areas of ejecta moved far from the crater, and two external areas. Each area was investigated both before and after the crater formation, by the study of the photometrically corrected spectral parameters: the 1.9  |$\mu$| m reflectance, the near-infrared spectral slope, and the depth of the bands at 2.7 and 2.8  |$\mu$| m. The subsurface material of the post-crater areas shows deeper absorption bands, a decrease in reflectance, and a reddening in spectral slope with respect to the surface material of pre-crater areas. The subsurface regolith could have experienced a lower OH devolatilization due to space weathering and/or could be composed of finer dark grains than the surface layer. The ejecta reached distances of |$\sim $| 20 m from the impact point, mainly moving in the northern direction; nevertheless, a few ejecta also reached the south-eastern part of crater. [ABSTRACT FROM AUTHOR]

The article discusses research on the use of two-dimensional (2D) seismic reflection dataset to examine the evidence of a complex impact crater referred to as the Nadir Crater in West Africa. Topics explored include the construction of a seismic stratigraphic framework for the Guinea Plateau region to estimate the age and paleoenvironment of the said crater, the seismic characteristics particularly morphology and damage zone of the crater, and the observed deformation in the crater subsurface.

Interest in impact craters on the earth's surface has increased worldwide and is being investigated by using remote sensing, geological, boreholes, geophysical, and laboratory measurements. These measurements are used to build dynamic models to study crater formation. In this work, the near‐crater sediments at the young Wabar crater field in Saudi Arabia have been investigated using magnetic, transient electromagnetic (TEM), seismic, and ground‐penetrating radar (GPR) methods. The main objectives of this research were to (a) explore the possibility of any remnant major pieces of the meteorite, (b) investigate the meteoroid direction, and (c) map the deformational structures associated with the meteorite impact. Our results show five different magnetic anomaly types and three layers in the subsurface. The maximum depth of deformation due to the impact of the meteorite is about 25 m as shown by the seismic travel time tomogram, the quasi‐2D TEM, and the 3D GPR model. TEM survey confirmed the geometrical characteristics of the major crater and located another small crater (known as Philby‐A). The magnetic survey shows no evidence of any remnant major pieces of the meteorite; however, it was used to trace ejecta material containing highly dilute magnetic material. The magnetic carrier is most likely spheres of metal incorporated in the black/green glasses. During the expedition, many small pieces of the meteoroid were found and collected for further geochemical analysis. Based on the geophysical findings, the meteorite direction was found to be from north to south. Plain Language Summary: In this study, we used magnetic, transient electromagnetic, seismic, and ground‐penetrating radar methods to explore the subsurface at the Wabar meteoroid impact site. This site is located in the Empty Quarter (Rub Al‐Khali) area, southeast of Saudi Arabia, where a large piece of the meteoroid was found and moved to the British Museum in the 1930s. The geophysical data were processed and interpreted to create a subsurface model of the impact crater and its surroundings to (a) investigate the possibility of finding any remnant major pieces of the meteorite at the crater site, (b) investigate the meteorite direction, and (c) map the deformational structures associated with meteorite impacts at the Wabar site. Key Points: A subsurface model of the impact crater field at Wabar is developedTo investigate the meteoroid directionOverlapping deformation zones of the two major craters [ABSTRACT FROM AUTHOR]

The use of materials for remote sensing of the Earth made it possible to identify a new type of crustal structures and features of their expression in relief. These are ring structures that complicate the structure of the studied structures of a linear type. As a result of the study of the morphology, geological and tectonic structure of ring structures, it was established that they represent formations of various origins: pluton-volcanic, cosmogenic, and anthropogenic. Cosmogenic structures of different ages and differ in various degrees of transformation.

Apatite has been widely used for assessing the volatile inventory and hydrothermal fluid compositions of asteroidal and planetary bodies. We report the OH, F, and Cl abundances, as well as the hydrogen isotope composition, of apatite in the CM1‐2 chondrite Boriskino and in the C1‐ungrouped Bench Crater meteorite. Apatite in both meteorites is halogen‐poor, close to the hydroxylapatite endmember composition, and characterized by average δDSMOW values of −226 ± 59% and 233 ± 92%, respectively. Compared to apatite, the matrix in Bench Crater is depleted in D with a δDSMOW value of −16 ± 119‰. Comparing apatite and water H isotope compositions yields similar apatite‐water D/H fractionation ΔDApatite‐Water of approximately 120–150‰ for both chondrites, suggesting that apatite formed at similar temperatures. Combining a lattice strain partitioning model with apatite F and Cl abundances in Boriskino and Bench Crater yields low F and Cl abundances <300 μg g−1 in apatite‐forming fluids, and fluid F/Cl ratios that are roughly consistent with the bulk F/Cl ratios of other CI and CM chondrites. This suggests that hydrothermal alteration on these meteorite parent bodies took place under closed‐system conditions. Based on the OH abundance estimates for the apatite‐forming fluids, we estimated the pH values of alteration fluids to be of approximately 10–13. Such alkaline fluid compositions are consistent with previous modeling and suggest that apatite formed late, toward the end of completion of hydrothermal alteration processes on the Boriskino and Bench Crater parent bodies. [ABSTRACT FROM AUTHOR]

The Yutu‐2 rover of the Chang'E‐4 spacecraft observed many meter‐sized shallow pits fully covered with small fragments, distinct from the typical rock‐free impact craters with comparable sizes in the landing area. The unique morphology of the pits and the visible and near‐infrared spectra of the fragments suggest that the fragments are broken pieces of impact melt‐conglutinated regolith breccia projectiles, which were excavated from preexisting craters. The rareness of rock on the landing area surface suggests that the preexisting craters were probably small in size (e.g., <60 m in diameter), not large enough to penetrate the thick regolith (~12 m) and to excavate the beneath rock breccia and/or bedrock. The presence of the impact melts was confirmed by the glass‐like spectra of some fragments with unusually high albedo and blue‐green tint in the centers of the pits. These observations reveal the gardening and consolidating processes on the Moon. Plain Language Summary: There are very rare outcrops of bedrock on the lunar surface because the Moon is covered by the lunar regolith. The detailed formation processes of the lunar regolith are important for understanding the orbiting and landing exploration data, and for planning future sample return missions. The lunar rover Yutu‐2 discovered fragment‐filled pits and identified in situ impact glass in the fragments. The glass‐bearing and regolith‐like fragments were probably broken pieces of lunar regolith breccia projectiles, which were excavated from the consolidated bottom and walls of preexisting small craters within the lunar regolith (<12–15 m in thickness). These observations contribute to our understanding of the formation processes of the lunar regolith. Key Points: Unique fragment‐filled pits distinct from the meteorite impact craters were observed at the Chang'E‐4 landing siteImpact glass in the fragment‐filled pits was identified in situ for the first timeThe discoveries of the Yutu‐2 rover provide important evidence for the recycling of the lunar regolith [ABSTRACT FROM AUTHOR]

Phase relations in MgFe2O4 at 20–27 GPa and 1,000–1,200 °C were investigated, and a novel post‐spinel phase of MgFe2O4 (space group, Pnma) was identified. This phase has a Z‐shape framework of edge‐sharing (Mg,Fe)O6 octahedra, with other Mg and Fe cations randomly occupying one tetrahedral and two octahedral sites in tunnel spaces within the framework. This structure is similar to Nax (Fe,Ti)xTi2‐xO4 phase (0.75 ≤ x ≤ 0.9) with (Fe,Ti)O6 Z‐shape framework and tricapped‐prism sites for Na. Compression data showed ~6% volume reduction at 16–20 GPa. The recovered phase may have transformed during decompression from the Nax (Fe,Ti)xTi2‐xO4‐type structure due to cations in the tunnel spaces shifting, probably because of cation‐size misfit. The novel phase may be found in impact craters and shocked meteorites and may serve as an indicator of shock P‐T conditions. Without crystal structure refinement, post‐spinel phases are likely to be misidentified due to similar crystallographic features. Plain Language Summary: The high‐pressure behavior of spinel‐structured minerals is an important issue in Earth science to understand physics and chemistry of the mantle, particularly its redox state. Spinel‐type MgFe2O4 and its high‐pressure phase are found in diamonds and shocked meteorites. During the past two decades, high‐pressure forms of spinel‐type MgFe2O4 have been intensively investigated, but uncertainty about their stability fields and crystal structures persists. We examined the phase relations in a MgFe2O4 system up to 27 GPa, which is representative of the uppermost lower mantle pressures, at 1,000–1,200 °C, and synthesized a previously unknown MgFe2O4 phase. So far, CaFe2O4‐, CaTi2O4‐, and CaMn2O4‐type structures have served to define as the high‐pressure spinel‐type structures. Structural analysis of the novel compound revealed that it has features similar to those of conventional high‐pressure structures, but its cation arrangement is very different. Based on known phase relations, this phase may occur in impact craters and shocked meteorites and possibly plays an important role as a P‐T indicator for shock events. The finding of the novel MgFe2O4 phase highlights the necessity of careful phase identification of high‐pressure phases of spinel‐type structures by crystal structure refinement in any experimental products and natural samples due to their crystallographic similarity. Key Points: We investigated phase relations in MgFe2O4 and found a new MgFe2O4 high‐pressure phase that is stable at 21–27 GPa and 1,000–1,200 °CThe new phase has features similar to conventional post‐spinel structures, but it is a novel type that can be formed in shock eventsWe stress the risk of misidentification of post‐spinel phases in the absence of structure analysis due to their crystallographic similarity [ABSTRACT FROM AUTHOR]

Unexploded ordnance (UXO) pose a significant threat to post-conflict communities, and current efforts to locate bombs rely on time-intensive and dangerous in-person enumeration. Very high resolution (VHR) sub-meter satellite images may offer a low-cost and high-efficiency approach to automatically detect craters and estimate UXO density. Machine-learning methods from the meteor crater literature are ill-suited to find bomb craters, which are smaller than meteor craters and have high appearance variation, particularly in spectral reflectance and shape, due to the complex terrain environment. A two-stage learning-based framework is created to address these challenges. First, a simple and loose statistical classifier based on histogram of oriented gradient (HOG) and spectral information is used for a first pass of crater recognition. In a second stage, a patch-dependent novel spatial feature is developed through dynamic mean-shift segmentation and SIFT descriptors. We apply the model to a multispectral WorldView-2 image of a Cambodian village, which was heavily bombed during the Vietnam War. The proposed method increased true bomb crater detection by over 160 percent. Comparative analysis demonstrates that our method significantly outperforms typical object-recognition algorithms and can be used for wide-area bomb crater detection. Our model, combined with declassified records and demining reports, suggests that 44 to 50 percent of the bombs in the vicinity of this particular Cambodian village may remain unexploded. [ABSTRACT FROM AUTHOR]

The ~70 km-diameter Yarrabubba impact structure in Western Australia is regarded as among Earth's oldest, but has hitherto lacked precise age constraints. Here we present U–Pb ages for impact-driven shock-recrystallised accessory minerals. Shock-recrystallised monazite yields a precise impact age of 2229 ± 5 Ma, coeval with shock-reset zircon. This result establishes Yarrabubba as the oldest recognised meteorite impact structure on Earth, extending the terrestrial cratering record back >200 million years. The age of Yarrabubba coincides, within uncertainty, with temporal constraint for the youngest Palaeoproterozoic glacial deposits, the Rietfontein diamictite in South Africa. Numerical impact simulations indicate that a 70 km-diameter crater into a continental glacier could release between 8.7 × 1013 to 5.0 × 1015 kg of H2O vapour instantaneously into the atmosphere. These results provide new estimates of impact-produced H2O vapour abundances for models investigating termination of the Paleoproterozoic glaciations, and highlight the possible role of impact cratering in modifying Earth's climate. The ~70 km-diameter Yarrabubba impact structure in Western Australia has previously been regarded as among Earth's oldest meteorite craters, but has hitherto lacked absolute age constraints. Here, the authors determine a precise impact age of 2229 ± 5 Ma, which extends the terrestrial cratering record back in time by > 200 million years and establishes Yarrabubba as the oldest recognised meteorite impact structure on Earth. [ABSTRACT FROM AUTHOR]

The article focuses on the concept of GeoArt, which involves appreciating and studying the aesthetic beauty found in various geological features and landforms, encompassing both scientific and artistic aspects. It explores GeoArt from the perspective of geological formations in India; intriguing examples like unique hills, rock formations and land shapes that resemble humanoids, animals, hearts & more; and the fusion of natural processes and artistic appreciation in the Earth's landscapes.