Large Craters Research Articles

Review of temporal trend in Archean granitoid chemistry- implications for Eoarchean (3.7–3.9 Ga) transition in geodynamic regime of crust formation

In this study, we review changes in Archean granitoid chemistry using stacked probability density estimation and statistical change-point analyses. A significant change in Archean sodic granitoid composition occurs in the 3.9–3.75 Ga period, marked by a shift of SiO2, Al2O3, Na2O, V, Cr, Sr, Sr/Y to higher, and TiO2, FeOT, MnO, P2O5, A/NK, A/CNK, Sc, Ba, Ta, Nb, Hf, Y, and rare earth elements to lower values, which reflects different formation P-T regime and petrogenetic processes. Using phase equilibria and trace element modelling, we demonstrate that the pre-3.9 Ga Acasta Tonalite Gneiss (ATG)-like granitoids formed at shallow depths (∼3 km) but are chemically distinct from impactites of all known large impact craters with basaltic/mixed target rocks. Impact melting produces MgO-rich melts at relatively greater “apparent” depths, reflecting target rock chemistry and contribution from the upwelling mantle, and is unlikely to have produced the shallow-seated ATG rocks. The ATG trace element chemistry is similar to many modern-day non-arc settings felsic rocks, which suggests that the melting regime in these extensional settings also existed before 3.9 Ga and ATG formed in a mantle plume-driven extensional tectonic regime involving melting of long-lived mafic proto-crust at shallow crustal depths above mantle upwelling. In contrast, the 3.9–3.75 Ga transitional and post-3.75 Ga TTGs formed by deep-seated (25–50 km) melting in equilibrium with garnet-bearing amphibolite. When considered together with Ti isotopic evidence of shift from tholeiitic to calc-alkaline magmatism in the 4.0–3.75 Ga period, the evidence for a transition from a regime dominated by crustal reworking to one of significant juvenile input at 3.60–3.85 Ga, noted in trace element/Hf-isotope composition of detrital zircon from several cratons and the reported ultra-high pressure metamorphism/interleaving arc-plume sequence, require a greater depth of melting. We interpret this transition to mark a gradual shift from stagnant-lid to intermittent mobile-lid-type plate tectonics involving deeper subduction of oceanic lithosphere. However, from the single occurrence of pre-3.9 Ga ATG rocks and their similarity with some Archean Fe-rich silica-saturated rocks chemistry, it is unknown whether plume magmatism was the only active mechanism or operated in conjunction with mobile-lid tectonics on early Earth, like in Archean.

Spectral Analysis of Mare Ingenii Basin (Lunar Farside)

AbstractMare Ingenii is a site of great interest for lunar geology as it is one of the few basaltic plains on the farside of the Moon. It is located within the outer edge of the South Pole‐Aitken basin, the largest and oldest impact basin in our Solar System. Mare Ingenii includes two large craters, Thomson and Thomson M, and a prominent swirl, a high‐albedo sinuous feature whose origin is still debated. We conducted spectral analysis on 28 selected regions of interest within Mare Ingenii, with the aim of inferring its mineralogy. We considered reflectance data acquired in the visible to near‐infrared spectral range by the Moon Mineralogy Mapper (M3) imaging spectrometer onboard the Chandrayaan‐1 mission, to derive a set of spectral parameters. Our results show wide compositional variability, with the dark material of the mare basaltic floor showing the centers of the Fe2+ absorption bands of the pyroxenes shifted toward long wavelengths (0.96–0.99 and 2.03–2.12 μm, respectively), consistent with the spectral characteristics of high‐Ca pyroxenes (as well as swirl material and intermediate albedo regions). In contrast, the bright material of the small surrounding craters shows Fe2+ absorption bands shifted toward short wavelengths (0.91–0.94 and 1.91–2.04 μm, respectively), more consistent with low‐Ca or Ca‐free pyroxenes. The obtained results suggest a mafic signature throughout the surface of Mare Ingenii, probably representative of the composition of the lower lunar crust.

Effect of 3.5 % NaCl solution with different Na2S concentrations on ultrasonic cavitation erosion behaviors of HVOF sprayed WC-Ni coatings

In this article, the WC-10Ni coatings were fabricated by HVOF spray, then the ultrasonic cavitation erosion performances of the coatings in distilled water and 3.5 wt% NaCl solution with various Na2S concentrations (0, 20 and 200 ppm) were investigated. The results of the cumulative volume loss of the coating in different mediums showed that the coating exhibited enhanced cavitation erosion resistance with the increase of Na2S concentrations in medium. The reason for the improvement on the cavitation erosion performance was the growth of corrosion product films containing sulphide. In comparison with the coating after cavitation erosion in medium without Na2S, no large craters and deep grooves were observed on the eroded coating surface in medium with Na2S. The ultrasonic cavitation damage of the coating manifests as the spall of the metal binder phase (Ni) and exposure of the hard phase (WC).

Magnetic Field Signatures of Intermediate-sized Impact Craters on Mars

Magnetic field signatures over impact craters provide constraints for the history of the Martian dynamo. Due to limitations of the spatial resolution of magnetic field models, previous studies primarily focused on large impact craters (mostly ≥ 500 km in diameter). To fill the impact crater age gaps of previous studies, we investigate the magnetic field signature of 23 intermediate-sized craters (150–500 km in diameter) on Mars using both MAVEN data and a magnetic field model. Ten impact craters located in the South Province, the unmagnetized primordial crust, exhibit no or weak magnetic field signatures. The other 13 impact craters produce stronger magnetic anomalies, with the ratio of the averaged magnetic field inside and outside the craters (B in/B out) ranging from 0.4 to 1.2. The B in/B out values exhibit correlation coefficients of −0.54, −0.57, and −0.69 with the diameters of craters, calculated from the MAVEN data, the crustal field model at the surface, and 150 km altitude, respectively. A B in/B out larger than 1.0 usually appears in craters with smaller diameters, which is also demonstrated by the forward modeling in this study. Furthermore, the results of the forward modeling indicate that the craters of stronger magnetizations show a larger B in/B out. According to this, the Martian dynamo can be associated with the magnetization of craters of different ages, and the characteristic time of the dynamo can be limited. Our study supports the hypothesis that the Martian dynamo weakened or ceased at ∼4.0 Ga and a late dynamo was perhaps active at ∼3.7 Ga.

YOLO-Crater Model for Small Crater Detection

Craters are the most prominent geomorphological features on the surface of celestial bodies, which plays a crucial role in studying the formation and evolution of celestial bodies as well as in landing and planning for surface exploration. Currently, the main automatic crater detection models and datasets focus on the detection of large and medium craters. In this paper, we created 23 small lunar crater datasets for model training based on the Chang’E-2 (CE-2) DOM, DEM, Slope, and integrated data with 7 kinds of visualization stretching methods. Then, we proposed the YOLO-Crater model for Lunar and Martian small crater detection by replacing EioU and VariFocal loss to solve the crater sample imbalance problem and introducing a CBAM attention mechanism to mitigate interference from the complex extraterrestrial environment. The results show that the accuracy (P = 87.86%, R = 66.04%, and F1 = 75.41%) of the Lunar YOLO-Crater model based on the DOM-MMS (Maximum-Minimum Stretching) dataset is the highest and better than that of the YOLOX model. The Martian YOLO-Crater, trained by the Martian dataset from the 2022 GeoAI Martian Challenge, achieves good performance with P = 88.37%, R = 69.25%, and F1 = 77.65%. It indicates that the YOLO-Crater model has strong transferability and generalization capability, which can be applied to detect small craters on the Moon and other celestial bodies.

Inversion of the Lunar Subsurface Rock Abundance Using CE-2 Microwave Brightness Temperature Data

The rock strongly affects the surface and subsurface temperature due to its different thermophysical properties compared to the lunar regolith. The brightness temperature (TB) data observed by Chang’E-1 (CE-1) and Chang’E-2 (CE-2) microwave radiometers (MRM) give us a chance to retrieve the lunar subsurface rock abundance (RA). In this paper, a thermal conductivity model with an undetermined parameter β of the mixture has been employed to estimate the physical temperature profile of the mixed layer (rock and regolith). Parameter β and the physical temperature profile of the mixed layer are constrained by the Diviner Channel 7 observations. Then, the subsurface RA on the 16 large (Diameter > 20 km) Copernican-age craters of the Moon is extracted from the average nighttime TB of the CE-2 37 GHz channel based on our previous rocky TB model. Two conclusions can be derived from the results: (1) the subsurface RA values are usually greater than the surface RA values retrieved from Diviner observations of the studied craters; (2) the spatial distribution of subsurface RA extracted from CE-2 MRM data is not necessarily consistent with the surface RA detected by Diviner data. For example, there are similar RA spatial distributions on both the surface and subsurface in Giordano Bruno, Necho, and Aristarchus craters. However, the distribution of subsurface RA is obviously different from that of surface RA for Copernicus, Ohm, Sharonov, and Tycho craters.

Sands on Meridiani Planum, Mars

AbstractThe analyses of 184 sediment targets and more than 70,000 individual grains revealed that along the Opportunity rover traverse there are four distinct fractions of deposits related to different geomorphological settings: (a) dust mixed with very fine sand is common behind topographical obstacles, (b) fine sands are deposited in depressions, (c) very coarse sands occur in coarse‐grained ripple fields, and (d) gravel dominates at the rims of craters and on bedrock as lag deposits. Medium size sands were not observed on the plains, but they can be trapped in relatively large craters, where they form dunes and are within coarse‐grained ripples and transverse aeolian ridges (TARs). The fine sands show no regional variations in chemical composition and granulometry, as these sands are easily transported by wind. The very coarse sands vary in composition and shape between the plains and the Endeavour crater rim as their sources are local and their transport distances are short. On the plains, the gravel and the coarse sands are enriched in iron and characterized by higher roundness than the grains from the Endeavour crater rim. The source of iron‐rich, rounded grains on the plains are hematite spherules that are eroded out of Burns formation rocks. The smallest, the best sorted, and the least rounded coarse sand samples are found on coarse‐grained ripple crests. They are mainly composed of spherule fragments and their low roundness indicates shorter transport path lengths than those of grains transported in the past when coarse‐grained ripples migrated.

Automated precision counting of small lunar craters - A broader view

An automated system for counting small craters at lunar landing sites has been expanded to include selected locations on the Moon's far side and high latitudes. Highland areas were generally excluded from this new survey, because sloping terrain can have a significant effect on crater lifetimes. But some locations on highland light plains units were analysed, as were some young Copernican age crater ejecta blankets and impact melts.This study focuses on craters having diameters between 2.5 m and 50 m, for which counts are so high that they are best plotted as Crater Size Frequency Histograms (CSFHs), rather than the conventional cumulative plots (CSFDs). This histogram representation enables the finest details of the plots to be compared across sites. Using multiple precisely aligned images of each site enables false negatives to be included and false positives rejected, ensuring that no visually recognisable craters are missed, a capability that is not possible when analysing single images.There are some very distinct differences between the curves at different sites. Based on the known ages of boulder tracks and counts of craters formed over the last 50 years, the largest craters within the size range up to 50 m are thought to be no more that a few hundred million years old. A model for the evolution of small crater populations on an absolute time scale is presented and the absolute ages of young features are estimated.There is no evidence in the data for secondary cratering, nor is there any clear variation of counts and slopes with longitude or latitude, so other possible explanations for the variabilities between sites must be found.The results obtained by this project should prove useful for modelling crater formation and destruction and also as training data for machine learning systems.

The inevitability of large shallow craters on Callisto and Ganymede: Implications for crater depth-diameter trends

Complex craters with diameters (D) ≥ 40 km on Callisto and Ganymede are shallower than would be expected from simply extrapolating the depth-diameter trend from smaller (D ≤ 40 km) craters. This unusual depth-diameter (d-D) trend, and associated changes in crater morphology, have been hypothesized to result from rheological transitions, including the existence of an ocean, within the moons' ice shell. Simulations of impact crater formation can reproduce the observed shallow depths but require heat fluxes roughly twice the maximum radiogenic flux to do so. Here we demonstrate that the d-D trends on Callisto and Ganymede can instead be explained as a direct consequence of viscous relaxation under radiogenic heating. We use numerical simulations of viscous relaxation to show that if craters form at the depth expected from an extrapolation of the complex crater d-D trend, they will evolve to the observed depths over timescales of 200 Myrs to 1 Gyrs. Large craters (e.g., D ≥ 80 km) younger than 200 Myrs, which would retain greater depths, should be relatively rare. If we instead assume that the craters formed at their observed depths, as proposed by previous impact modeling, they quickly become much shallower than observed. We find excellent agreement between observed crater depths on Ganymede and our simulated crater depths by assuming a pure-water ice composition and a diurnally averaged surface temperature of 120 K, but require either larger-grained or “dirty” ice with a modestly higher viscosity to match observations at Callisto, where the surface temperature is warmer (130 K). We favor the latter explanation because it is consistent with the existence of a dusty lag on Callisto's surface and the absence of a similar lag on Ganymede. Our results predict that, for a given crater diameter, post-relaxation crater depth should increase with increasing latitude, a hypothesis best tested on Callisto, whose relatively quiescent geologic history best preserves the signature of viscous relaxation under radiogenic heating.

Mathematical Models and System of Intelligent Servo for High-Efficiency Electrical Discharge Assisted Arc Milling on Difficult-to-Cut Materials

Difficult-to-cut materials, such as superalloys and titanium alloys, have been increasingly used in aerospace and other fields. However, commonly used mechanical milling methods for difficult-to-cut materials have problems, including low processing efficiency and severe tool wear. Electrical discharge assisted arc milling (EDAAM) is a novel high-efficiency machining method proposed by the authors to solve these processing problems. The machining efficiency achieved by EDAAM when processing difficult-to-cut materials is much higher than that achieved by mechanical milling and conventional electrical discharge machining (EDM) milling. However, if EDAAM adopts the traditional EDM servo control method, it will easily form deep and large discharge craters on the surface of the workpiece, which may lead to high machining errors and cause the workpiece to be scrapped. To ensure normal processing, low-energy discharge parameters that may reduce the processing efficiency have to be adopted. To address the above issues and achieve the optimal machining condition of difficult-to-cut materials, mathematical models and system of intelligent servo for EDAAM are proposed. An EDAAM discharge information dataset is obtained, and the intelligent recognition and classification method for discharge states is proposed. The EDAAM intelligent servo control system is proposed based on mathematical models created. The experimental results of superalloy Inconel 718 by EDAAM show that, compared with the nonintelligent servo control system, the intelligent servo control system can increase the material removal rate by up to ten times, reduce the relative electrode wear rate by 37%, and avoid the scrapping of the workpiece.

Review of morphological changes of Anak Krakatau before and after 2018 eruption using Aerial photogrammetry

We carried out drones photogrammetry on Anak Krakatau in 2013, 2019, 2020 and 2021. Changes in the morphology of Anak Krakatau occurred so quickly as its volcanic activity never stopped. Its pyroclastic cone in 2013 reached a height of 334 meters with a coastline circumference of 6.8 km. The circumference of the pyroclastic cone calculated from the traces of the old crater wall has a volume of 31971 m3. During the 2018 eruption, a large part of the cone was pulverised, resulting in a large crater of 400 m in diameter. Paradoxically, while the top of the volcano has dropped to 156 m, the island-volcano has grown relatively large, with an additional circumference of 7.2 km. The body of Anak Karakatu has experienced an addition to the coastline, especially on the South, East and North sides. This happened due to the eruption and tsunami accompanied by avalanches during the December 2018 eruption. During the 2020 and 2021 eruption periods, the coastline has not changed. This period was marked by the growth of a pyroclastic cone in the crater that had formed previously during the 2019 eruption. The pyroclastic cone was opened to the southwest by lava flows that flowed westward as far as 600 meters.

Viscous Relaxation of Oort and Edgeworth Craters on Pluto: Possible Indicators of an Epoch of Early High Heat Flow

AbstractImpact craters, with their well‐defined initial shapes, have proven useful as heat flow probes of a number of icy bodies, provided characteristics of viscous relaxation can be identified. For Pluto's numerous craters, such identifications are hampered/complicated by infilling and erosion by mobile volatile ices, but not in every case. Large craters offer relatively deep probes of rheological structure, and on Pluto two large old craters in a major dark (volatile‐ice free) region are probably the best examples for possible viscous relaxation: Oort (115‐km diameter) and Edgeworth (140‐km diameter). They are similar in size, location, and apparent age (morphological preservation), but may or may not be coeval. Edgeworth is particularly shallow and its floor appears bowed up above the original ground plane, a classic hallmark of viscous relaxation in which viscosity decreases sharply with depth. Oort is less relaxed, but may be somewhat younger and less affected by an early epoch of high heat flow. Finite element calculations show that this heat flow would have to have been substantial to explain Edgeworth's upbowed floor by viscous relaxation, several times steady‐state radiogenic values for present‐day surface temperatures. We expect Pluto's brittle ice lithosphere to be fractured and porous, however, markedly reducing thermal conductivity and increasing temperatures at depth and relaxation for a given heat flow. We find that most relaxation occurs well within 100 Myr after impact for Edgeworth and Oort, and focus attention on a temporal (and/or regional) epoch of elevated heat flow, possibly tied to the serpentinization of Pluto's rocky core.

Three-Dimensional Reconstruction and Geometric Morphology Analysis of Lunar Small Craters within the Patrol Range of the Yutu-2 Rover

Craters on the lunar surface are the most direct method for the study of geological processes and are of great significance to the study of lunar evolution. In order to fill the research gap on small craters (diameter less than 3 m), we focus on the small craters around the moving path of the Yutu-2 lunar rover and carry out a 3D reconstruction and geometrical morphology analysis on them. First, a self-calibration model with multiple feature constraints is used to calibrate the navigation camera and obtain the internal and external parameters. Then, the sequence images with overlapping regions from neighboring stations are used to obtain the precise position of the rover through the bundle adjustment (BA) method. After that, a cross-scale cost aggregation for a stereo matching network is proposed to obtain a parallax map, which can further obtain 3D point clouds of the lunar surface. Finally, the indexes of the craters are extracted (diameter D, depth d, and depth–diameter ratio dr), and the different indicators are fitted and analyzed. The results suggest that CscaNet has an anomaly percentage value of 1.73% in the KITTI2015 dataset, and an EPE of 0.74 px in the SceneFlow dataset, both of which are superior to GC-Net, DispNet, and PSMnet, and have higher reconstruction accuracy. The correlation between D and d is high and exhibits a positive correlation, while the correlation between D and dr is low. The geometric morphology expressions of small craters fitted by using D and d are significantly different from the expressions proposed by other scholars for large craters. This study provides a priori knowledge for the subsequent Von Karmen crater survey mission in the SPA Basin.

Rapid glacial sedimentation and overpressure in oozes causing large craters on the mid-Norwegian margin: integrated interpretation of the Naust, Kai and Brygge formations

Abstract Along continental margins with rapid sedimentation, overpressure may build up in porous and compressible sediments. Large-scale release of such overpressure has major implications for fluid migration and slope stability. Here, we study if the widespread crater-mound-shaped structures in the subsurface along the mid-Norwegian continental margin are caused by overpressure that accumulated within high-compressibility oozes sealed by low-permeability glacial muds. We interpret 56 000 km 2 of 3D and 150 000 km 2 of 2D-cubed seismic data in the Norwegian Sea, combining horizon picking, well ties and seismic geomorphological analyses of the crater-mound landforms. Along the mid-Norwegian margin, the base of the glacially influenced sediments abruptly deepens to form 28 craters with typical depths of c. 100 m, areal extents of up to 5130 km 2 and volumes of up to 820 km 3 . Mounds are observed in the vicinity of the craters at several stratigraphic levels above the craters. We present a new model for the formation of the craters and mounds where the mounds consist of remobilized oozes evacuated from the craters. In our model, repeated and overpressure-driven sediment failure is interpreted to cause the crater-mound structures, as opposed to erosive megaslides. Seismic geomorphological analyses suggest that ooze remobilization occurred as an abrupt energetic and extrusive process. The results also suggest that rapidly deposited, low-permeability and low-porosity glacial sediments seal overpressure that originated from fluids being expelled from the underlying high-permeability and high-compressibility biosiliceous oozes.

Experimental study on the influences of charging structure with various filling mediums on rock blasting performances

Decoupled charge blasting is widely used in tunnel contour excavation to mitigate overbreak/underbreak and the extent of excavation damaged zone, which plays a pivotal role in enhancing the safety and efficiency of tunnel construction. This study experimentally investigates the influences of filling medium (air, water, sand and clay) on blasting performances. Five single hole blast (SHB) tests with a blasthole length of 1.0 m and blasthole diameter of 45 mm are first conducted in an underground tunnel. The ground vibration signals are captured using three-component seismic vibrometers installed at different distances away from the blasthole. The blast-induced crater is automatically measured using a 3D laser scanner and the post-blast rock fragmentation is analyzed using the open-source program ImageJ. Subsequently, the peak pressure, particle velocity and displacement on the borehole wall with respect to various filling mediums are theoretically deduced and analyzed. The experimental results indicated that the fully coupled blasting produces the largest near-field peak particle velocity (PPV), finest rock fragmentation and largest crater, but also the highest PPV attenuation rate. Among these decoupled charge blasts, water-decoupled blasting results in the finest fragmentation and maximum crater, whereas the corresponding PPV is at a much smaller level than coupled blasting. Sand and clay-decoupled blasts yield smaller PPV and crater but coarser fragmentation than water-decoupled blasting. Air-decoupled charge structure causes the minimum PPV and crater size, as well as the coarsest fragmentation. The theoretical analysis shows that the fully coupled blasting yields the largest borehole wall pressure (BWP), particle velocity and displacement on borehole wall than those induced by decoupled blasts, as well as the maximum attenuation rate of BWP and velocity. Additionally, water-decoupled blasting exhibits higher energy transfer efficiency so that a finer rock fragmentation and a larger crater are obtained than air, clay and sand decoupled blasts, but more attention should be paid to the blast vibration.

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

The topographic slopes of the Moon host different types of mass wasting features, in which boulder falls are abundant globally. Boulder falls are characterized by trails that are produced by rolling, bouncing and sliding of boulders on the lunar surface, in response to ground shaking originating from shallow moonquakes, impact events and other surface processes. Our previous work showed evidence for moonquake-triggered boulder falls at hundreds of sites on the interior of Orientale multi-ring basin. In this study, we document new evidence for ejecta boulder falls around 135 fresh simple impact craters with diameters ranging from 0.1 to 2.5 km in the same basin. Our detailed characterization of ejecta boulder falls around eight selected impact craters reveal their modes of occurrences, morphological properties, formation ages and clues to their impact origins. The ejecta boulder falls have the characteristic boulder trails arranged radially around the host impact craters, shorter trail lengths, narrow trail widths and shallow trail depths, when compared to the moonquake-triggered boulder falls in the same basin. Some impact craters exhibit radial asymmetry of boulder trails around these craters because of oblique impacts, in which longer trails are abundant in down-range directions, while fewer and shorter trails characterize up-range directions. In some cases, local slopes also contribute to increased trail lengths and deviation from radial distribution of trails. Formation ages of a few host impact craters, determined based on conventional crater counting method, are in the range of 0.94–6.4 Ma, and the age of ejecta boulder falls is consistent with the host impact crater ejecta. These characteristics suggest that the trails were produced by the ejecta boulders, during the ejecta blanket formation stage of the host impact craters. The relationship between the host impact crater diameter and the average size of large ejecta boulders present in their ejecta blankets suggests that the host impact craters are primary impact craters. Hence, the initial ejecta boulder fall velocities are expected to be in the ejection velocity range of ∼5–100 m/s. During ballistic sedimentation, these ejecta boulders erode the local target materials including regolith and mix them along their trails. It is also observed that ejecta boulder falls occur around small fresh simple impact craters (<2–3 km) at the Schrödinger and Lorentz basins. Around large size impact craters and basins, ejecta boulder falls produced large-size radial grooves, lineaments and sculptures on the Moon. We conclude that the characteristics of ejecta boulder falls and moonquake boulder falls are distinctly different from each other, reflecting their distinct formation conditions, but these form contemporaneously on the Moon.

Morphological characteristics of impact craters with diameters of 5–20 km on the Moon

The morphology of impact craters on the Moon plays an important role in understanding impact cratering process, surface and subsurface properties, and their evolutions. In this study, we systematically analyzed the depth, rim height, slope, and rock abundance of 15,135 impact craters between 5 and 20 km in diameter on the Moon, covering the simple and simple-to-complex transitional crater regimes. We found that the decline rates of inner average slopes of mare craters are generally larger than those of non-maria craters and that the degradation rate of inner upper wall slopes around rim crest is not uniform, which decreases rapidly when the depth/diameter ratio (d/D) lies in 0.25–0.15 but slowly when d/D is in 0.15–0.05. However, we found that there is no difference in crater rim height between different terrains (e.g., maria and highlands). In addition, we also found the decrease in rock abundance is more rapid than the ejecta infilling of the crater floor, especially for large simple craters. Moreover, we investigated the diameter-dependent morphological features of fresh craters in different terrains and revised the onset of transitional crater diameters based on the 180 freshest craters. We found that crater initial depth depends on target properties (e.g., strength and porosity) whereas that the degradation rate of the crater depth is independent of terrains. Furthermore, we found that the power-law relations for depth and diameter of fresh simple craters are d = 0.293D0.865 (mare), d = 0.297D0.884 (highland), d = 0.221D0.959 (north pole) and d = 0.209D0.981 (south pole). The onsets of transitional crater diameters are ∼14.2 km (mare), ∼15.7 km (highland), ∼16.6 km (north pole), and ∼ 16.8 km (south pole). These morphological characteristics and their differences in different terrains suggest that target properties (e.g., strength, layering, and porosity) affect the formation and degradation of larger simple and transitional craters.

Morphological Analysis of Anak Krakatau Volcano after 22 December 2018 Eruption using Differential Interferometry Synthetic Aperture Radar (DInSAR)

Anak Krakatau Volcano is an active volcano located in the Krakatau Complex, Sunda Strait, Indonesia. On 22 December 2018, the volcano experienced a major eruption that led to a tsunami that devastated the shores of the islands of Java and Sumatra and killed up to 437 people. The eruption also destroyed the volcano’s body and change its shape drastically and forming a large crater in the southwestern part. After that eruption, the volcano continues to grow up. This research aims to analyze the deformation of the Anak Krakatau Volcano post-2018 eruption by using the differential interferometry SAR method (DInSAR). In order to support the analysis, we additionally compare the DInSAR result with tectonic-volcanic activity. Sentinel 1-A type SLC satellite imagery data from 5 June 2019 to 7 January 2020; consisting of 19 images or 18 pairs as master and slave were used to producing a deformation map. DInSAR result shows the volcano was generally experiencing deflation during the period, ranging from -1.03 to -4.81 cm (-3.01 cm average). However, inflation also occurred ranging from 0 to 5.99 cm, correlating with shallow and deep volcanic activity and followed by eruptions in October 2019 when the highest activities were observed. Furthermore, coherence value should be highly considered along with DInSAR processing, and this research allows that coherence to be acceptable.

Current and potential landscape functions of areas with the remnants of World War II bombing in the Koźle Basin, southern Poland

Abstract Wars bring civilisation and environmental disasters. In the forests and wetlands of the Koźle Basin (southern Poland), clusters of bomb craters remain, which are associated with the air campaign conducted by the USAAF to disable the Third Reich’s fuel facilities. They are among the most spectacular in Europe today. There are nearly 6,000 large bomb craters with a diameter of 7-15 meters and smaller ones from the fall of unexploded ordnance. These areas, with their characteristic scarred relief, currently pose difficulties in terms of economic use. The depressions left after the bombs fell, naturally became small sedimentation basins and niches that were taken over by nature. Landscape and nature mapping of the surveyed areas, altered by the bombing, in conjunction with historical data, suggest that they require protection in the form of two landscape-nature protected complexes (a form of landscape protection in Poland). They can serve as environmental and historical education zones, wildlife sanctuaries, as well as areas for the introduction and reintroduction of species. This is important in a region where hundreds of years of agricultural dominance, as well as decades of intensive industrial development and urban settlement, have caused major changes in the natural environment and degradation of its structures. Similar historical sites, trails and cultural parks dedicated to the war campaigns have been introduced in different European countries.

Quantifying the Ejecta Thickness From Large Complex Craters on (1) Ceres

AbstractQuantifying the ejecta thickness distribution from complex craters is key to understanding surface‐evolving processes on Ceres. Using the Park et al. (2019, https://doi.org/10.1016/j.icarus.2018.10.024) shape model, we estimated the ejecta thickness of five complex craters located in Ceres' equatorial region by analyzing 1,778 smaller, simple craters in their continuous ejecta deposits. In addition, we constrained their rim‐crest ejecta thickness following Sharpton (2014, https://doi.org/10.1002/2013JE004523). The ejecta thicknesses range from ∼3 to 73 m and ∼96–223 m around complex craters and at their rim crest localities, respectively. We find that ejecta thicknesses on Ceres are thinner than those on the Moon. Meltwater likely facilitates thin ejecta deposits on Ceres, given that fluid pressure conditions allow transient liquid water stability at shallow depths (∼1.8 m). Such water must be short‐lived because the atmospheric pressure on Ceres is too low (≳2.09 × 10−8 Pa) to allow a stable liquid phase. Our findings are consistent with previous work that ascribes fluidized appearing ejecta morphologies to the melting of subsurface water ice.