Crater Formation Research Articles

Evolution of Subkilometer-scale Impact Craters on the Lunar Maria as Constrained from Mini-RF Data and Topographic Degradation Model

Physical properties (e.g., ejecta size and distribution) of impact craters are crucial and essential to understanding the ejecta excavation and deposition process, estimating rock breakdown rate, and revealing their evolution characteristics. However, whether these physical properties are scale-dependent and how they evolve in different radial regions needs further studies. In this study, we first investigated the physical properties and evolution of sub-kilometer (D ≤ 800 m) craters on lunar maria based on the radar circular polarization ratio (CPR). In addition, we estimated the periods over which rocks and blocky ejecta are exposed and buried in the shallow subsurface layer (termed as exposure time) in different radial regions and assessed the retention time and degradation states for potential radar anomalous craters. We found that in the central region of craters, the largest median CPR occurs after an 80 Myr delay following crater formation. In the rim region, there is no obvious CPR peak in the first 100 Ma, whereas in the upper wall region, an evident CPR peak occurs beyond 100 Ma and could last over one billion years. In addition, the probable exposure time of rocks and blocky ejecta is estimated to be ∼2.0 Gyr (central region), ∼2.7 Gyr (upper wall region), ∼2.1 Gyr (rim region), and ∼0.6 Gyr (continuous ejecta blanket region). We also propose that the retention time of radar anomalous craters depends on the crater size, whereas their degraded states are independent of crater size.

A Tectonic Origin for the Largest Marsquake Observed by InSight

AbstractThe S1222a marsquake detected by InSight on 4 May 2022 was the largest of the mission, at 4.7. Given its resemblance to two other large seismic events (S1000a and S1094b), which were associated with the formation of fresh craters, we undertook a search for a fresh crater associated with S1222a. Such a crater would be expected to be ∼300 m in diameter and have a blast zone on the order of 180 km across. Orbital images were targeted and searched as part of an international, multi‐mission effort. Comprehensive analysis of the area using low‐ and medium‐resolution images reveals no relevant transient atmospheric phenomena and no fresh blast zone. High‐resolution coverage of the epicentral area from most spacecraft are more limited, but no fresh crater or other evidence of a new impact have been identified in those images either. We thus conclude that the S1222a event was highly likely of tectonic origin.

Dual-wavelength femtosecond laser-induced single-shot damage and ablation of silicon

An experimental and theoretical study of laser-induced damage and ablation of silicon by two individual femtosecond pulses of different wavelengths, 1030 and 515 nm, is performed to address the physical mechanisms of dual-wavelength ablation and reveal possibilities for increasing the ablation efficiency. The produced craters and damaged areas are analyzed as a function of laser fluence and time separation between the pulses and are compared with monochromatic irradiation. The order of pulses is demonstrated to be essential in bi-color ablation with higher material removal rates when a shorter-wavelength pulse arrives first at the surface. Simulations based on the two-temperature model show that the visible pulse is profitable for the generation of the electron-hole plasma while the delayed IR pulse is efficiently absorbed in the plasma enhancing energy coupling to the target. At long delays of 30–100 ps, the dual-wavelength ablation is found to be particularly strong with formation of deep smooth craters. This is explained by the expansion of a hot liquid layer produced by the first pulse with a drastic decrease in the surface reflectivity at this timescale. The results provide insight into the processes of dual-wavelength laser ablation offering a better control of the energy deposition into material.

Tissue Ablation with Multi‐Millimeter Depth and Cellular‐Scale Collateral Damage by a Femtosecond Mid‐Infrared Laser Tuned to the Amide‐I Vibration

AbstractLaser ablation of bio‐tissues is the key technology of future surgeries, owing to the merits of submicron accuracy, non‐contact operation, and precision control assisted by automation and computer intelligence. Excellent efficiency, minimal collateral damage, biological safety, and tissue selectivity are the ideal parameters for delicate surgical applications. Here, by exploring the mid‐infrared (MIR) resonant ablation and the femtosecond cold processing, tissue ablation with multi‐millimeter depth and cellular collateral damage, enabled by a tabletop femtosecond MIR optical parametric amplifier operating at the amide‐I resonant wavelength of 6.1 µm, is demonstrated. Remarkably, the collateral damage is observed to be 15, <4, and <1 µm in the porcine cornea, sclera, and articular cartilage, respectively, with multi‐millimeter incision depth. In addition, preliminary proof‐of‐concept experiments of tissue‐selective ablation, microchannels on cartilage for drug delivery, laser glaucoma, keratotomy, neurologic tissue incision, dentin deep crater formation, and hypertrophic scarring ablation are demonstrated, which pave the way for high‐precision surgical applications with a tabletop solution.

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.

Ice breaking by low-velocity impact with a rigid sphere

Penetrator–ice plate impact subjected to dynamic loading constitutes many scientific applications for ice, such as controlling ice disasters by penetrating the ice cover and then entering underwater to explosive ice breaking on Earth, and life detection and resource development under water ice sheet on outer space planets. We present experimental results of brittle damage induced by a small spherical projectile impacting an ice plate with a thickness of 6–50 mm using a drop ball test device or a vertical gas gun. The corresponding impact velocities vary from 2 to 74 m/s. Crater parameters, residual velocity and energy absorption are investigated and assessed. The main fracture patterns and crater formation are captured by two high-speed cameras. A dynamic recrystallization phenomenon of polycrystalline ice is observed, and its formation mechanism is preliminarily analysed. The effects of the impact velocity, ice sample thickness, and restriction conditions on dynamic fracture processes and failure modes are systematically explored. These results improve our understanding of dynamic fracturing mechanism in ice engineering applications.

Investigating projectile penetration into immersed granular beds via CFD-DEM coupling

Projectile penetration into an immersed granular bed is a common phenomenon in both geophysics and engineering, encompassing various scenarios such as immersed crater formation and offshore soil-structure interaction. It involves the complex physical interaction between the fluid and granular materials. In this study, we investigate the dynamics of projectile penetration into a granular bed immersed in a fluid using a coupled computational fluid dynamics and discrete element method (CFD-DEM). The granular bed is composed of polydisperse particles, and the projectile is modeled as a rigid sphere. The morphology of crater formation, the dynamics of the projectile, and the drag force characteristics in immersed cases were studied in detail and compared to the dry scenario. The numerical results show that the final penetration depth of the projectile follows an empirical relation derived from experimental observations, where the falling height and the drag force during penetration obey a power-law function and a modified generalized Poncelet law, respectively. The interstitial fluid not only provides direct drag force, but also enhances the effective drag force of the granular bed by improving its generalized friction and effective viscosity in different configurations. Micro-analyses of the velocity evolution and contact force network in different stages of the fluid–solid interaction were performed to clarify the penetration dynamics. This research provides insights into the mechanisms of projectile penetration and the effects of interstitial fluid on granular media, which are crucial in engineering applications such as offshore anchoring, ball penetration tests in soft sediments, and soil-structure interactions.Graphical

Subsurface magma movement inferred from extensometer and tiltmeter records during the early stage of the 2018 Shinmoe-dake eruptions, Japan

We infer the temporal changes in the pressure sources that induced crustal deformation during the 2018 Shinmoe-dake eruption using strain and tilt observations and discern that the deep magmatic activity associated with the early stage of this eruption began approximately 19 h earlier than the previously defined onset of magmatic activity. Distinct tilt changes were observed from around 09:00 on 6 March to 12:00 on 8 March 2018 (JST), coincident with observed lava outflow into the crater and lava dome formation. Existing studies have attributed this tilt change to the onset of the deflation of a spherical pressure source located at ~ 7 km bsl (below sea level) to the northwest of Shinmoe-dake. Here we examine strain and tilt data that were acquired in the Kirishima volcanic group, and we find that the distinct changes in the measured strain at Isa-Yoshimatsu Observatory began at around 14:00 on 5 March. This change can be explained by the deflation of a spherical pressure source, thereby suggesting that the onset of magma ascent was earlier than previously thought. The time variation in the spherical pressure source is estimated using the time-dependent inversion of the Ensemble Kalman Filter; the deflation source ascended from ~ 11 to 7 km bsl during Phase 1 (14:00 on 5 March to 06:00 on 6 March) and descended from 7 to 8 km bsl during Phase 2 (06:00 on 6 March to 12:00 on 8 March). Interferometric synthetic aperture radar analysis suggests that a dike intrusion had occurred just below Shinmoe-dake crater until 5 March, and this inflatable crustal deformation is attributed to the emplacement of residual volcanic fluids from the 2011 eruption. It is also known that the surface eruptive activity increased during Phase 1, including an increase in ash venting from the night of 5 March. These strain and tilt observations, therefore, suggest that magma ascended from ~ 11 km bsl to the magma reservoir at 7 km bsl during Phase 1, followed by a deflation of the magma reservoir during Phase 2 due to the large magma supply to the surface.Graphical

Numerical investigation of ice plate fractures upon rigid ball impact

The fracture process and breaking capability of ice cover impacted by high-speed projectiles before underwater explosion is an urgent subject of scientific research in ice engineering applications. This paper presents the results of numerical simulations of the dynamic fracture behaviour induced by the impact of a small spherical projectile on an ice plate. The proposed 3D rate-dependent peridynamics model is validated by the dynamic ring Brazilian disc testing of ice specimens. Good agreements between the present model and the previous experiments are obtained in ice breaking processes and damage patterns of thin, medium and thick ice plates. Several cases are analysed and discussed in terms of various impact velocities, ice thicknesses, and boundary constraint conditions. The simulations identify detailed fracturing characteristics that are not observed in experiments, including the sequence and shape of crack propagation in a short time interval, the crater formation and the damage evolution along the thickness direction. The proposed peridynamics computational model provides new understanding of the potential of using penetrator–ice block impact tests to observe the evolution of complex brittle damage and reveal the failure mechanism.

Émile Belot’s Models, or an Engineer’s Quest for Scientific Legitimacy

Abstract Between 1905 and 1937, Émile Belot, an engineer and then director of a public tobacco factory, threw himself into scientific research seeking to reconstruct the history of the formation of the solar system. This article goes over and analyses the experimental practices Belot drew on in support of his theory, looking at the equipment he manufactured and operated in his “experimental cosmogony laboratory.” Together with a few other French engineers, Belot persistently sought to prove his legitimacy to address astronomical and geological issues. His machines reproducing the formation of spiral nebulae, volcanoes, or lunar craters acted both as material resources for deciding between rival scientific hypotheses, and as tools which, by analogy, materialised the mechanical nature of the cosmos Belot hoped to study without being confined to the scientific margins.

NEW DATA ON MUD VOLCANISM IN THE ARCTIC ON THE YAMAL PENINSULA

A wide range of geological and geophysical methods was carried out on the Yamal Peninsula in the Arctic in the period 2014–2022. The results were analyzed together with data from remote sensing of the Earth. Fundamentally new data on the gas-dynamic mechanisms of dangerous processes in permafrost have been obtained. These data included catastrophic gas blowouts and explosions with the formation of giant craters. More than three thousand zones of powerful gas blowouts with the formation of craters at the bottom of thermokarst lakes, rivers, and the coast of the Kara Sea have been discovered. According to data on remote sensing of the Earth, large mud volcanic structures, located at the bottom of the Labvarto and Yambuto thermokarst lakes, were discovered on the Yamal Peninsula in 2022–2023 for the first time. Monitoring of their state with the use of retrospective satellite images showed the presence of periodic release of underground fluids, including gas. A conclusion was made about the discovery of active mud volcanoes on the Yamal Peninsula

Новые данные об интенсивной дегазации Земли в Арктике на севере Западной Сибири: термокарстовые озера с кратерами выбросов газа и грязевыми вулканами

In the last decade, in the north of Western Siberia, the authors carried out a large amount of comprehensive research, which made it possible to obtain fundamentally new information about the gas-dynamic mechanisms of dangerous processes in the Arctic permafrost. According to remote sensing data, at the bottom of thermokarst lakes, rivers and coastal zones of the Kara Sea, more than 4.5 thousand zones of powerful gas blowouts with the formation of craters (pockmark) were found. There are reasons to believe that powerful gas emissions mainly come from shallow deposits with ultrahigh (superlithostatic) pressures. For the first time, large mud volcanic uplifts with pronounced craters have been found at the bottom of the Arctic thermokarst lakes. Based on the monitoring of the ice situation and the water environment on the basis of retrospective satellite images on lakes Otkrytie, Labvarto and Yambuto, the presence of periodic emissions of formation fluids, including gas, is shown. Based on the combination of a number of features, the discovered objects can be classified as active mud volcanoes with a high level of probability. The results of the studies allow us to state that mud volcanism is widespread in the Circum-Arctic megaregion.

Plume effects on Martian surface: Revealing evolution characteristics of plume-surface interaction at Tianwen-1 landing site

Engine plumes can seriously erode the Martian surface during the landing phase, causing a substantial alteration of the terrain of the immediate touchdown area and beyond. Furthermore, large amounts of lifted dust can block the view of boulders or craters, posing a serious threat to the lander's safety. Improving our understanding of the plume-surface interaction can reduce the risk of failure on a Mars landing mission. In situ studies on this subject are limited, particularly those relating to high-thrust single-nozzle engines. The Tianwen-1 represents the only Mars landing mission that employed such an engine with a thrust of ∼3000 N during the landing phase: Its success represents a unique opportunity in addressing this issue, providing an important reference for future Mars return missions. Here, we report the evolution characteristics of the plume-induced regolith erosion and the plume impingement effect measurements at the Tianwen-1 landing site. The results show that depressions and infilling are a complex process accompanying the changing of patterns as the lander descends. Specifically, the plume will seriously erode the area beneath the nozzle, causing the formation of a deep crater. Meanwhile, the expanding radial flow tends to flatten the peripheral area of the lander, which depends on the homogeneity of the regolith. To better quantify the impingement effects, some crucial parameters were extracted. The measured volume, diameter, and depth of the crater are 0.115 ± 0.019 m3, 1.50 m, and ∼0.35 m, respectively. We also calculated the total erosion area and volume as 4879.4 ± 297.7 m2 and 376.9 ± 102.2 m3. In addition, plume-induced infilling/erosion depths and rates during the landing phase were measured. Further, we investigated the shallow stratigraphic architecture exposed by the plume-induced crater beneath the lander, showing that it represents probably dust/sand-coated black rocks above at least ~35 cm thick, bright reddish materials. These results provide valuable insights into the plume impingement effects on the Martian surface and the shallow subsurface layer at the Tianwen-1 landing site, which will benefit future Mars explorations.

Automatic crater shape retrieval using unsupervised and semi-supervised systems

Impact craters are depressions formed due to impacts on the surface of planetary bodies. Recent deep learning-based crater detection methods assume craters as circular-shaped without much attention to extracting craters’ shape and morphology. Craters’ shape information (i.e., instance segmentation map for craters) can be helpful for many advanced analyses including crater formation and surface characteristics. However, publicly available ground truth catalogs for the lunar surface do not contain crater shape annotations and are also challenged by the missing craters problem. We attempt to solve these challenges by proposing a novel estimation and refinement-based approach using a combination of unsupervised and semi-supervised systems. Our method consists of (a) learning estimated crater segmentation (ECS) maps by a novel adaptive rim estimation algorithm (unsupervised system) using side information, (b) refining ECS by a cascade of Mask region-based convolutional neural networks (R-CNNs) to obtain refined crater segmentation (RCS) maps (semi-supervised system), and (c) combining RCS followed by predicting a highly accurate crater segmentation map. In the absence of any publicly available catalog for crater shape annotations, we conducted a ranking-based user study to compare against the state-of-the-art. The proposed method outperforms by achieving the best ranking for 63.53% crater images as compared to 9.67% for state-of-the-art. Further, the extracted shapes of the craters are utilized to improve the estimate of the craters’ diameter, depth, and other morphological factors to be made publicly available: https://drive.google.com/drive/folders/1ghBf2FXNIJUEQkAM2GjLZNiIXKEhZMEB?usp=sharing.

Effect of gas cluster species on crater formation for fused silica

The interactions of the Ne, Ar, and Kr clusters with the fused silica surface were investigated by molecular dynamics simulations. The impacts of noble gas clusters with kinetic energies ranging from 25 to 110 eV per atom were compared. The characteristics of the formed craters were examined at cluster incidence angles of 0° and 60°. It was found that the crater diameter is almost the same for different gas species at normal incidence. However, at oblique incidence, the depths of craters formed by the Ne and Kr clusters differ insignificantly. Additionally, it has been shown that the ratio of crater length to depth is a function of the energy per cluster atom and can be the same for clusters with different energies and sizes. The dependencies of the crater volume on the scaled cluster energy and energy per unit area were studied. The cratering efficiency of different gas species was estimated, and the relationship between crater volume and sputtering yield was revealed. Moreover, it was shown that the ratio of sputtered volume to crater volume is power law related to the ratio of the sputtered atoms energy to the initial kinetic energy of clusters.

Laser ablation microsampling of copper phthalocyanine blue by the second-harmonic radiation of Nd:YAG laser

An original nonlinear optical method employing laser ablation with single nanosecond laser pulses at a wavelength of λ = 532 nm is used to study organic paint layer (copper phthalocyanine blue (PB15)). Two processes (photochemical reaction and formation of craters), which appear to be nonlinear result from the pulsed radiation. It is shown that the nonlinear optical procedure (laser ablation microsampling (LAMS)) can be used to obtain microparticles of PB15 sufficient for the further analysis. The Raman spectra of the surface of the paint layer prior to and after LAMS and microparticles are obtained. Spectral data, including those in the low-frequency region, are discussed.

Crater formation and deuterium production in laser irradiation of polymers with implanted nano-antennas.

Recent validation experiments on laser irradiation of polymer foils with and without implanted golden nanoparticles are discussed. First we analyze characteristics of craters, formed in the target after its interaction with the laser beam. Preliminary experimental results show significant production of deuterons when both the energy of laser pulse and concentration of nanoparticles are high enough. We consider the deuteron production via the nuclear transmutation reactions p+C→d+X where protons are accelerated by the Coulomb field generated in the target plasma. We argue that maximal proton energy can be above threshold values for these reactions and the deuteron yield may noticeably increase due to presence of nanoparticles.

Dynamic Behavior of Droplet Impact on Laminar Superheated Particles.

The impact of droplets on particles involves a wide range of complex phenomena and mechanisms, including bubble nucleation, crater formation, fluidization, and more intricate changes in the boiling regime when impacting superheated particles. In this study, we focus on droplet impact behavior on superheated laminar particles at various temperatures and define six typical characteristic patterns of a single droplet impact on superheated laminar particles, including film evaporation, bubbly boiling, immersion boiling, sputter boiling, transition boiling, and film boiling. It is worth noting that the variations of inertial force FI caused by gravity, the capillary force FC generated by the pores of the droplets, and the dewetting force by the vapor phase FV are the main contributors to different evaporation regimes. Interestingly, we find that the Leidenfrost point (LFP) of droplets on the laminar superheated particles decreases with particle size, which is related to the effect of the pore space generated between the laminar particles. Finally, the effect of temperature, particle size, and Weber number (We) on the dynamic behavior of droplet impact is revealed. Experimental results show that the instantaneous diameter of droplets is inversely proportional to the change of height, with different patterns of maximum spreading diameter and maximum bounce height at different particle sizes, while the maximum spreading velocity and maximum bounce velocity are independent of particle size. We believe the present work would provide a broader knowledge and comprehension of the droplet impact on heated particles and promote the development of the safety and productivity of industrial processes such as fluid catalytic cracking, spray drying, and spray cooling.

Object-Oriented Remote Sensing Approaches for the Detection of Terrestrial Impact Craters as a Reconnaissance Survey

The purpose of this study is to employ a remote sensing reconnaissance survey based on optimal segmentation parameters and an object-oriented random forest approach to the identification of possible terrestrial impact craters from the global 30-m resolution SRTM DEM. A dataset consisting of 94 confirmed and well-preserved terrestrial impact craters, 104 volcanic calderas, and 124 valleys were extracted from real-world surface features. For craters with different sizes, eight optimal scale parameters from 80 to 3000 have been identified using multi-resolution segmentation, where the scale parameters have a positive correlation (R2 = 0.78) with the diameters of craters. The object-oriented random forest approach classified the tested impact craters, volcanic calderas, and valleys with an overall accuracy of 88.4% and a Kappa coefficient of 0.8. The investigated terrestrial impact craters, in general, have relatively lower rim circularity, higher length-to-width ratio, and lower relief, slope, and elevation than volcanic calderas. The topographic characteristics can be explained by geological processes associated with the formation and post-deformation of impact craters. The excavation and ejection by initial impact and rebound of excavated materials contribute to low elevation. The post-impact deformation, including inward collapse and slump of unstable rims, weathering, erosion, and sediment deposition, further reduces elevation and relief and modifies shapes resulting in lower circularity and higher length-to-width ratio. Due to the resolution limitation of the source DEM data and the number of real-world samples, the model has only been validated for craters of 0.88 to 100 km in diameter, which can be generalized to explore undiscovered terrestrial impact craters using cloud computing with global datasets provided by platforms such as Google Earth Engine and Microsoft Planetary Computer.