Complex Craters Research Articles

Chandrayaan-3 landing site evolution by South Pole-Aitken basin and other impact craters

The Chandrayaan-3 mission with the Vikram-lander and the Pragyan rover landed in the high latitude highland region near the south pole of the Moon. The landing site is located ∼350 km from the South Pole-Aitken basin rim, an ancient and highly cratered terrain. This site has undergone the complex emplacement sequence of SPA basin ejecta followed by the nearby and distant impact basins and crater ejecta materials. To evaluate the source of individual basin and crater ejecta emplacement over this landing site, we carefully demarcated the nearby and distal basins and craters that could have contributed to the source regolith material. We found that the SPA basin is the major contributor, which deposited nearly ∼1400 m of ejecta materials, and 11 other basins deposited ∼580 m of ejecta. The other complex craters contributed up to ∼90 m of ejecta. Meanwhile, secondary craters of a few km in diameter located adjacent to the landing site contributed to ∼0.5 m ejecta, which are crucial target materials for the Pragyan rover insitu analysis. Pragyan rover images revealed the landing site is devoid of >1 m boulders along the traverse revealing typical highland terrain. The Pragyan rover Navcam and Orbital High Resolution Camera regional images revealed linear distal ejecta rays possibly from the distant impacts as insitu evidence of foreign material at the CH-3 landing site. We found a semi-circular, heavily degraded structure encompassed around the landing site, which is interpreted as a buried impact crater ∼160 km in diameter probably formed before the SPA basin. The erasure of pre-SPA basin craters is caused by both the direct burial by SPA basin ejecta, high seismic shaking during SPA formation, and then followed by various post-SPA craters and its associated some of the degradation processes. Overall, Chandrayaan-3 landed within an ancient region that hosts some of the most deeply excavated materials on the Moon.

Enhancement of the Cerean Exosphere by Sublimation from Complex Craters

On icy bodies like the dwarf planet Ceres, impacts excavate volatile-rich material from beneath a dessicated lag layer and deposit it in the near-surface environment where higher temperatures drive sublimation. Ice has been detected in the upper meter of the ejecta blanket and interior of Occator crater, suggesting that large craters could be a significant source of exospheric water vapor. We assess the present-day exospheric contribution of a complex crater by first estimating the extent of volatile-rich deposits associated with a crater of a given size. We use a vapor diffusion model to calculate sublimation rates from the deposits, taking into account constraints on the thermophysical parameters of icy regolith from the Dawn mission. Extrapolating this model to craters formed throughout Ceres’ history, we find that the cumulative present-day sublimation rate from all complex crater deposits is ∼0.01 kg s−1, a factor of a few times greater than the outgassing rate from the global ice table. The dominant source of sublimation is not the conspicuous faculae but rather the volatile-rich ejecta blankets, which cover a significantly larger area than deposits in the crater interior. Because large impacts can blanket a significant fraction of the surface with ice-rich ejecta, complex craters are crucial for understanding the background present-day exosphere and the history of sublimation on icy bodies.

Morphological and chronological mapping of Petavius crater, nearside of the Moon

Petavius, a complex crater from the late Imbrian epoch, features a giant central peak, numerous smaller peaks, and an inner terraced wall arising nearly 3 km above the crater floor. The region has seen periods of tectonic and volcanic activity. A meter-scale detailed mapping of LROC- Narrow Angle Camera (NAC) images was carried out to understand the tectonic features and associated volcanic history under this crater. We found many fragmented blocks, fields of striated boulders, grabens, layering near grabens and striated boulders, rock exposures, and many fractures from NAC mapping, indicating magmacreating pressure underneath the floor of a crater. The fractures identified from NAC images are probably linked with an underlying magmatic sill of high-density bodies. Crater size-frequency distribution analysis indicates that magmatic activity likely persisted for ∼2.75 Ga in the Petavius crater. It is noteworthy that this relatively recent age of volcanism has not been reported previously. The crustal thickness of the study region varies from 27 to 40 km; at the mapped tectonic features and volcanic regions, the crustal thickness of 30–34 km is found. The unique tectonic environment of the Petavius crater, in combination with the associated morphological variation and numerous exposures of mafic, suggests that the crater formed in phases associated with its structural and morphologic features and is derived from the lower crust. The morphometric analysis and previous studies support a model of magmatic intrusion and sill formation within the fractured crust beneath the crater floor; such a sill would be a likely source both for effusive mare material erupted through floor fractures into low-lying portions of the crater floor. The tectonic system on the floor of the crater was the result of post-impact processes.

The Effect of Antecedent Topography on Complex Crater Formation

AbstractImpact craters that form on every planetary body provide a record of planetary surface evolution. On heavily cratered surfaces, new craters that form often overlap antecedent craters, but it is unknown how the presence of antecedent craters alters impact crater formation. We use overlapping complex crater pairs on the lunar surface to constrain this process and find that crater rims are systematically lower where they intersect antecedent crater basins. The rim morphology of the new crater depends on the depth of the antecedent crater and the degree of overlap between the craters. Our observations suggest that new craters do not always obliterate underlying topography and that transient rim collapse is altered by antecedent topography. This study represents the first formalization of the influence of antecedent topography on rim morphology and provides process insight into a common impact scenario relevant to the geology of potential Artemis landing sites.

Morphometric and structural parameters of impact craters in Algeria: Control of sedimentary target rocks and effect of post impact process

The Earth Impact Database (EID) currently includes four impact craters located in Algeria. These craters are well-exposed, morphologically visible, partially covered and all situated in a vast, very arid Saharan geological domain devoid of any vegetation cover. Consequently, they can be easily identified using the TanDEM-X digital elevation model and Alsat-1B satellite images. The aim of this work is to identify the characteristics of sedimentary target rocks that control the morphometric and structural parameters of Algerian craters, as well as the effects of post-impact processes. Crater exposure, type, and structure (depth-diameter ratio, rim-to-floor height, central peak and moat diameters), outline (circular, polygonal, elongated) and impactite types are therefore discussed. Relative or stratigraphic dating and erosion/burial rates are estimated for the craters. Results indicate that Amguid and Talemzane are simple, well-preserved young craters, closer to a pristine state. Tin Bider is a complex exposed structure showing an irregular outline with a well-developed central peak and two rings. Ouarkziz is a transitional crater; based on its diameter alone it is classified as a complex crater; however, a topographic central peak is not observed. A deep formation uplift is detected in the central zone, interpreted as a stratigraphic peak where the uplift has not reached significant heights to form a clearly visible peak. This may be due to the reduced diameter of Ouarkziz, which is smaller than what has always been described.

Quantitative Research on the Morphological Characteristics of Lunar Impact Craters of Different Stratigraphic Ages since the Imbrian Period

Impact craters serve as recorders of lunar evolutionary history, and determining the stratigraphic ages of craters is crucial. However, the age of many craters on the Moon remains undetermined. The morphology of craters is closely related to their stratigraphic ages. In the study, we systematically and quantitatively analyzed seven morphological parameters of 432 impact craters with known stratigraphic ages (Copernican, Eratosthenian, Imbrian), including crater depth, wall width, wall height, rim height, irregularity, volume, and roughness, as well as rock abundance. The study provided a range of morphological parameters for craters from the Copernican, Eratosthenian, and Imbrian. Additionally, we derived power law relationships between five morphological parameters and crater diameter, excluding irregularity and roughness. Furthermore, the transitional crater diameters from simple to complex crater morphology were determined for the Copernican and Eratosthenian, approximately 13 km and 15 km, respectively. These results suggest systematic differences in the lunar regolith in different stratigraphic ages. For impact craters of the same diameter, as crater age increases, irregularity tends to be greater, while crater depth, wall width, wall height, rim height, volume, roughness, and rock abundance tend to be smaller. Therefore, in cases where the diameter is determined, the actual values of morphological parameters and rock abundance can be used to constrain the stratigraphic age information of craters of an unknown age.

An Image Retrieval Method for Lunar Complex Craters Integrating Visual and Depth Features

In the geological research of the Moon and other celestial bodies, the identification and analysis of impact craters are crucial for understanding the geological history of these bodies. With the rapid increase in the volume of high-resolution imagery data returned from exploration missions, traditional image retrieval methods face dual challenges of efficiency and accuracy when processing lunar complex crater image data. Deep learning techniques offer a potential solution. This paper proposes an image retrieval model for lunar complex craters that integrates visual and depth features (LC2R-Net) to overcome these difficulties. For depth feature extraction, we employ the Swin Transformer as the core architecture for feature extraction and enhance the recognition capability for key crater features by integrating the Convolutional Block Attention Module with Effective Channel Attention (CBAMwithECA). Furthermore, a triplet loss function is introduced to generate highly discriminative image embeddings, further optimizing the embedding space for similarity retrieval. In terms of visual feature extraction, we utilize Local Binary Patterns (LBP) and Hu moments to extract the texture and shape features of crater images. By performing a weighted fusion of these features and utilizing Principal Component Analysis (PCA) for dimensionality reduction, we effectively combine visual and depth features and optimize retrieval efficiency. Finally, cosine similarity is used to calculate the similarity between query images and images in the database, returning the most similar images as retrieval results. Validation experiments conducted on the lunar complex impact crater dataset constructed in this article demonstrate that LC2R-Net achieves a retrieval precision of 83.75%, showcasing superior efficiency. These experimental results confirm the advantages of LC2R-Net in handling the task of lunar complex impact crater image retrieval.

Polygonal impact craters on Ganymede

AbstractPolygonal impact craters (PICs) are unique geological features observed on various planetary bodies and constitute a small percentage of the impact crater population. This study focuses on PICs on Ganymede, where no such craters have been investigated so far. Here we present the distribution of PICs, examine their morphological characteristics, investigate the causes for their polygonal shapes, and discuss the factors that support their formation. We identified and analyzed 459 PICs on Ganymede with complex crater morphologies. They are widely distributed across the Moon and occur on both dark and light terrain. Our analysis revealed that the majority of orientations of straight rim segments align parallel or subparallel to adjacent tectonic linear features. There is at least one tectonic linear orientation adjacent to PICs, even in dark, cratered terrains. Based on the comparison of the number of PICs and tectonic linear features, Ganymede is believed to have undergone more intense tectonic activity than other icy bodies like Ceres and Dione, where PICs were described. The presence of numerous PICs on Ganymede suggests that surface lineations and grooves are expressions of fractures that form zones of weakness in the ice crust that got reactivated during impact cratering.

New geophysical and zircon data support an impact hypothesis for the Velingara structure (Senegal)

On Earth, impact structures are rare in intertropical zones. Here we evaluate the 35–40 km diameter Velingara depression in Senegal as a candidate impact structure. The depression has a topographic relief of only 50 m and is essentially buried under modern sediments. For the first time, potential-field ground observations and a microstructural survey of detrital zircons for shock features were conducted at Velingara. A 15 mGal gravity low in a 10 km diameter central anomaly was found, while significant (100 nT) amplitude magnetic field anomalies were observed in the depression. Forward modeling was used to explain the crustal sources of the anomalies, arguing in favor of the presence of a buried impact structure. An electron backscatter diffraction survey of circa 5,000 detrital zircons from a sample of modern alluvium identified a single granular zircon; orientation data for the grain does not record the former presence of reidite, but does closely resemble grains with highly dispersed neoblast orientations that have only been reported from impact settings. Age determination by LA-ICP-MS indicates the unusual granular zircon recorded an age of ca. 550 Ma. Results of the geophysical data and zircon microstructural survey reported here are consistent with, but do not yet prove, an impact origin hypothesis for the Velingara structure. The difference in amplitude between the diameter of the depression, and that of the gravity anomaly remains puzzling. Several impact scenarios are considered, which include the subsequent evolution via surface processes of a 10-km crater into a larger depression, or a large-scale (d = 40 km) complex impact crater with a peculiar geophysical anomaly limited to its central region.

Ion emission from warm dense matter produced by irradiation with a soft x-ray free-electron laser

We report on an experiment performed at the FLASH2 free-electron laser (FEL) aimed at producing warm dense matter via soft x-ray isochoric heating. In the experiment, we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model. We find that most emitted ions are thermal, but that some impurities chemisorbed on the target surface, such as protons, are accelerated by the electrostatic field created in the plasma by escaped electrons. The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures. We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.

Sanātana Vijñāna & Warangal Fort

Telengana, the new province of India (2014) is explored from a Science Heritage perspective. It is seen she has an ‘impact crater’ of a geological period of the pre-Himalayan (Eocene) period. It has dual rings like complex craters acting as ramparts and hence the entire is the Warangal Fort. This is a case of ‘natural heritage’. Inside it is a Siva temple which is the central piece. It is a case of ‘man-made heritage’ and provides material for the Caption. Temple’s remains (demolished during the Islamic period) are studied from Science and engineering Heritage perspectives. Engrossing field study leads to interesting transpiration that yields a plethora of Hindu Sc & Tech aspects dating to c.13-14th A.D. Astronomically the temple appears to be associated with the star Betelgeuse i.e., Rigel of the Orion constellation (Vana Rājā Kalāpuruṣa Maṇḍala). The 1000-pillar temple complex -Hanamkonda (Han ūmān \ Hanūmā town) is associated possibly with the same constellation. There are three structures and the layout is alike Orion’s eastern triplet (κ-Ori – ε-Ori -&- α Orionis from S-to-N). These construe archaeo-astronomy (ancient pure science). Historically belongs to the Kakatiya (medieval) extending backward to tribal societies and pre-periods. Preliminary surface scanning of the satellite images of the Hyderabad Muslim heritage region indicates vestiges of a star\triangular shaped foundation of a possible erstwhile structure to the west by southwest of the Golconda fort. An excellent example of Vedic Sc. & Tech.

Understanding the Ries impact structure subsurface from high-resolution seismic data

Abstract The Ries impact structure (southern Germany) formed ca. 15 Ma and is 22–26 km in diameter, making it one of the youngest and best-preserved mid-size terrestrial impact craters, yet the subsurface has not been studied with modern geophysics. We present the first high-resolution seismic profiles of the Ries impact structure; the profiles show discontinuous intra-basement reflectors and a central crater floor without a significant central topographic high. The inner crystalline ring sits adjacent to, not on top of, the crater terrace zone. These morphologies indicate that during the crater modification stage, the rebounding central uplift at Ries rose and then collapsed without the continued outward motion required to form a fully developed peak ring. The Ries impact structure may be best considered a transitional complex crater form between a central-peak crater and a peak-ring crater as documented on the Moon and other rocky planets. A series of high-amplitude, discontinuous, topographically influenced reflectors overlying the basement implies that the suevite within the crater basin was emplaced via lateral transport.

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.

Investigation of compositionally distinct lithologies at and around the central peaks of some recent LUNAR craters

Central peaks of Copernican period complex craters of the Moon, provides the best examples to study impact melts morphologies alongwith the exposed subsurface, as they are better preserved and less affected by the space weathering. Crater Tycho, present towards nearside (SW) of the Moon, is one such example of young and fresh complex crater. Present study is high-resolution compositional investigation involving spectroscopic analysis coupled with morphological study of central peaks and floor of crater Tycho. Alongwith the other contemporary craters the study is intended to understand the nature of occurrence and distribution of compositionally distinct lithologies identified near their central peaks and crater floor that differ in colour and specific appearance. A detailed high-resolution analysis suggests that the clastic exposures associated with the melts have a mafic composition that have been observed at similar other contemporary craters. They represent the fragmental polymictic breccia clasts whose mineralogy and stratigraphic relation with the melts suggests them to be representative of subsurface anorthositic gabbro/noritic body. Their association with structural features, such as cooling cracks/fractures and breccias dikes indicate their formation at different stages of cratering and associated crustal modification. The formation mechanism of the polymictic breccia clasts causing lithological variability has been discussed.

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.

Peak-ring magnetism: Rock and mineral magnetic properties of the Chicxulub impact crater

The Chicxulub impact event at ca. 66 Ma left in its wake the only complex crater on Earth with a preserved peak ring, characterized by a well-developed magnetic anomaly low. To date, little is known about its magnetic properties. The joint Integrated Ocean Drilling Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drill core M0077A revealed that the peak ring consists of uplifted and strongly deformed granitoid basement rocks overlain by a 130-m-thick impact melt and suevite layer. Pre- and postimpact hydrothermal systems affected this basement with maximum temperatures up to 450 °C. We used microscopy, mineral chemistry, temperature-dependent magnetic susceptibility, and hysteresis properties to characterize the magnetic mineralogy of pre-, syn-, and postimpact rocks. Compared to its amount of pure, stoichiometric shocked magnetite, the granitoid basement shows low magnetic susceptibility, which is in line with earlier experimental studies indicating that shock reduces magnetic susceptibility. Cation-substituted magnetite with varying compositions in the melt rocks carries a higher induced and remanent magnetization compared to the basement. In the granitoid basement, magnetite was partially oxidized to hematite by a pre-impact hydrothermal event, but at lithological contacts with high-temperature impact melt rock, this hematite was locally retransformed back to magnetite. Elsewhere in the granitoid basement, the temperature reached in the hydrothermal system was too low for hematite retransformation. It was also too low to anneal all the lattice defects in the shocked magnetite, which likely occurs above 540 °C. The presence of shocked magnetite in the granitoid basement well explains the magnetic anomaly low due to its unusually low induced magnetization.

2022 Joint Barringer Medal for Kai Wünnemann and Gareth S. Collins

2022 Joint Barringer Medal for Kai Wünnemann and Gareth S. Collins

The Chicxulub impact structure reveals the first in-situ Jurassic magmatic intrusions of the Yucatán Peninsula, Mexico

Impact events that create complex craters excavate mid- to lower-crustal rocks, offering a unique perspective on the interior composition and internal dynamics of planetary bodies. On the Yucatán Peninsula, Mexico, the surface geology mainly consists of ∼3 km thick sedimentary rocks, with a lack of exposure of crystalline basement in many areas. Consequently, current understanding of the Yucatán subsurface is largely based on impact ejecta and drill cores recovered from the 180–200-km-diameter Chicxulub impact structure. In this study, we present the first apatite and titanite UPb ages for pre-impact dacitic, doleritic, and felsitic magmatic dikes preserved in Chicxulub's peak ring sampled during the 2016 IODP-ICDP Expedition 364. Dating yielded two age groups, with Carboniferous dacites (328–318 Ma) and a felsite (330± 9 Ma) overlapping in age with most of the granitoid basement sampled in the Expedition 364 drill core, as well as Jurassic dolerites (169–159 Ma) and a felsite (158 ± 19 Ma) that represent the first in situ sampling of Jurassic-age magmatic intrusions for the Yucatán Peninsula. Further investigation of the Nd, Sr, and Hf isotopic compositions of these pre-impact lithologies and impact melt rocks from the peak ring structure suggest that dolerites generally contributed up to ∼10 vol% of the Chicxulub impact melt rock sampled in the peak ring. This percentage implies that the dolerites comprised a large part of the Yucatán subsurface by volume, representing a hitherto unsampled pervasive Jurassic magmatic phase. We interpret this magmatic phase to be related to the opening of the Gulf of Mexico, representing the first physical sampling of lithologies associated with the southern extension of the opening of the Gulf of Mexico and likely constraining its onset to the Late Middle Jurassic.

Influence of Target Properties on Wall Slumping in Lunar Impact Craters Within the Simple‐To‐Complex Transition

AbstractThe 15–20 km crater diameter range on the Moon spans simple to transitional to complex crater morphologies. Simple craters in this range are only in the highlands. Transitional craters that contain localized slumps are scattered across the lunar surface. Most craters with localized slumps in the highlands superpose pre‐impact topography with obvious slope breaks. We interpret this as a condition favorable for post‐excavation internal slumping. However, some of these craters formed on terrains with topographic variation like the settings of simple craters: flat or gradually sloping surface, or degraded structures of older craters such as rims and terraces. To resolve the conundrum of two morphologies on one terrain type, we performed investigations of the local geology and topography of the inferred pre‐impact terrains. We assessed if the localized slumping in the craters happened during or well after crater formation, looked for spatial variations in the strength of the highlands crust, detected topographic breaks (through elevation data) that were unnoticeable in the optical data, and examined rim circularity. Our findings corroborate the influence of pre‐existing slopes on mass wasting along crater walls. Most of the craters with localized slumps have walls superposing topographic breaks that slope toward the crater interior. These walls are located near the uphill sector of the rims which initiated localized slumping. Most simple craters were found to have formed on surfaces with topographic breaks/slopes that face away from the adjoining crater walls, so that any immediate mass wasting would likely be outside the crater cavity.

Complex Crater Formation by Oblique Impacts on the Earth and Moon

AbstractAlmost all meteorite impacts occur at oblique incidence angles, but the effect of impact angle on crater size is not well understood, especially for large craters. To improve oblique impact crater scaling, we present a suite of simulations of complex crater formation on Earth and the Moon over a range of impact angles, velocities and impactor sizes. We show that crater diameter is larger than predicted by existing scaling relationships for oblique impacts; there is little dependence on obliquity for impacts steeper than 45° from the horizontal. Crater depth, volume and diameter depend on impact angle in different ways—relatively shallower craters are formed by more oblique impacts. Our simulation results have implications for how crater populations are determined from impactor populations and vice‐versa. They suggest that existing approaches to account for impact obliquity may underestimate the number of complex craters larger than a given size by as much as one‐third.