Crater Model Research Articles

Discrete element model of low-velocity projectile penetration and impact crater on granular bed

The present study investigates the low-velocity impacts of a spherical projectile into a bed of spherical particles using Discrete Element Method (DEM) simulations and laboratory experiments. The findings reveal intricate forces and energy transformations, indicating the phenomena leading to projectile impact, penetration, cessation, and crater formation. The DEM result indicates that the penetration stopping time of the projectile is not influenced by impact velocity. Further, simulations show that projectile penetration depth correlates with 1/2.7 power of total impact height, while crater diameter and depth scale with 1/4.32 power of nondimensional impact energy. The shape of the resulting crater appears independent of impact velocity and the maximum diameter of the fluidized region varies with the 1/2.68 power of impact velocity. Experimental validation confirms the accuracy of predicted penetration depths and crater diameters, enhancing confidence in DEM simulations. These findings extend scaling laws and reveal the influence of larger particles on low-velocity impact dynamics, addressing unexplored aspects of granular cratering.

History of Ceres’s Cold Traps Based on Refined Shape Models

Permanently shadowed regions (PSRs) in the north polar region of Ceres have been previously mapped by the Dawn spacecraft. Putative ice deposits are found in some of these PSRs, whereas most PSRs host no bright deposits, which is thought to be due to oscillations of the axis tilt with a ∼25 ka period. We use stereophotoclinometry to construct refined topographic models of PSR-hosting craters. Ray-tracing calculations reveal that no PSRs remain at the maximum axis tilt, which implies that the ice deposits are remarkably young. The bright ice deposits do not extend beyond PSRs at an axis tilt of 10°, which last occurred about 6 ka ago. This suggests that water is delivered to the polar regions or exposed within the craters by frequent and short-lived events. Surface temperatures are calculated with a terrain irradiance model to delineate cold traps. Based on maximum equilibrium temperatures, Cerean PSRs are too warm to trap supervolatiles.

Research on physical explosion crater model of high-pressure natural gas pipeline

In this study, Hypermesh and LS-DYNA numerical simulation software are used to build a multi domain coupling model of natural gas pipeline, including soil, pipeline, TNT explosive and air domain, and the non-reflection boundary conditions are set for the model. The TNT equivalent method is used to convert the physical explosion amount of natural gas pipeline into 1387.38 kg TNT explosive amount. The simulation results show that the physical explosion of pipeline forms an approximate elliptical crater with a width of 12.68 m and a depth of 4.12 m; the TNT equivalent of the model is corrected by comparing the crater simulation value and the size value of the crater calculated by the PRCI empirical formula under the same laying condition, and the correction coefficient is selected as 0.9, and the corrected TNT equivalent is 1248.64 kg; the modified model crater size is 3.72 m deep and 12.66 m wide, compared with the crater size obtained from the field test, the error of crater depth and width calculated by the modified model simulation is 5.7% and 15.5% respectively.

Lunar polar volatile remobilization in regolith-filled craters

Under lunar polar cold traps, volatile molecules within porous regolith may experience temperature and depth dependent slow mobility. Many degraded lunar craters exhibit thick regolith fill based on models of topographic diffusion and observations of fresh and degraded craters. Regolith has a low thermal conductivity relative to megaregolith and may act as a blanket for internal lunar heat flow, leading to increased temperatures at depth. We develop 2D thermal models of fresh and regolith-filled lunar craters over depths of meters to hundreds of meters below the surface. We find that the base of the stability and slow mobility zones migrate upward with regolith fill, which leads to temperatures that may increase the sublimation rate of volatiles at depth. For a notional cold trap crater 1.6 km in diameter and 3.6 billion years old, topographic diffusion fills it with approximately 90 m of regolith, and the regolith fill's blanketing effect causes the 110 K isotherm to shift about 180 m upward. This places it approximately 25 m below the current cold trap surface and well above the initial crater floor. The slow water ice mobility zone below the 110 K isotherms also shifts upward with regolith fill, potentially increasing volatile concentrations at shallower depths. These secondary volatile concentrations may be targets for sampling and testing hypotheses of volatile system processes. In addition, remobilized volatile concentrations may be a resource for future In-Situ Resource Utilization (ISRU) applications. The thick regolith fill in degraded craters and volatile remobilization potential in lunar subsurface cold traps have implications for future exploration instruments, sampling, and ISRU architectures.

Development of site specific blasting index parameters based on single hole blast test cratering

ABSTRACT An experimental method is proposed to assess blasting requirements based on in-situ cratering behavior. The method relies on single hole blast (SHB) tests to derive burden-dependent relationships. A non-linear crater model of the form is calibrated from SHB test results to describe the cratering behavior. Parameters and represent characteristic blastability index parameters that depend on geomechanical and operational conditions. A series of experimental SHB tests were conducted at three hard rock mines. The craters were mapped to capture the breakout profile and calibrate the model. Results showed that coefficient presents an inverse linear correlation with burden , while exponent s is approximately constant for a considerable range of burden values. Experimental results are used to define burden dependent relationship for bench blast designs and blasthole placement in underground development rounds. A complementary analysis addresses the prevalence of multiple cratering mechanisms according to geology and burden dimension.

The Complex Exhumation History of Jezero Crater Floor Unit and Its Implication for Mars Sample Return

AbstractDuring the first year of NASA's Mars 2020 mission, Perseverance rover has investigated the dark crater floor unit of Jezero crater and four samples of this unit have been collected. The focus of this paper is to assess the potential of these samples to calibrate the crater‐based Martian chronology. We first review the previous estimation of crater‐based model age of this unit. Then, we investigate the impact crater density distribution across the floor unit. It reveals that the crater density is heterogeneous from areas which have been exposed to the bombardment during the last 3 Ga to areas very recently exposed to bombardment. It suggests a complex history of exposure to impact cratering. We also display evidence of several remnants of deposits on the top of the dark floor unit across Jezero below which the dark floor unit may have been buried. We propose the following scenario of burying/exhumation: the dark floor unit would have been initially buried below a unit that was a few tens of meters thick. This unit then gradually eroded away due to Aeolian processes from the northeast to the west, resulting in uneven exposure to impact bombardment over 3 Ga. A cratering model reproducing this scenario confirms the feasibility of this hypothesis. Due to the complexity of its exposure history, the Jezero dark crater floor unit will require additional detailed analysis to understand how the Mars 2020 mission samples of the crater floor can be used to inform the Martian cratering chronology.

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

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

Flow Past Mound-Bearing Impact Craters: An Experimental Study

An experimental investigation into the flow produced by mound-bearing impact craters is reported herein. Both an idealized crater and a scaled model of a real martian crater are examined. Measurements were performed using high-resolution planar particle image velocimetry (PIV) in a refractive-index matching (RIM) flow environment. Rendering the crater models optically invisible with this RIM approach provided unimpeded access to the flow around and within each crater model. Results showed that the mean flow within the idealized crater exhibits more structural complexity compared to its moundless counterpart. Second-order statistics highlighted regions of minimal and elevated turbulent stresses, the latter of which revealed a complex interaction between shear layers that are present at the upstream and downstream parts of the rim and the central mound. Periodic vortex shedding of quasi-spanwise vortices from the upstream rim was revealed by POD-filtered instantaneous flow fields. Vertical flapping of this shear layer resulted in vortices occasionally impinging on the inner wall of the downstream rim. Further, conditional averaging analysis suggested periodic lateral oscillations of wall-normal vortices within the crater rim region reminiscent of those observed for flow inside spherical dimples. These results have implications for intra- to extra-crater mass and momentum exchange, and for sediment transport processes. Lastly, experiments with the Gale Crater model showed both similarities with and differences from the primary flow features found for the idealized model.

Horizontal single hole blast testing – Part 2: Field observations and experimental trends from SHB campaigns at two underground salt mines

This results presented in this paper follow the basic principles and methodology developed for horizontal Single Hole Blast (SHB) testing using terrestrial laser scanning (TLS), introduced in Part 1, and shows specific SHB test applications as a mean to investigate rock blasting behavior. Part 1 introduced a detailed procedure for consistent and systematic SHB testing to provide the means for reproducible and comparable data collection and characterization. The concept of crater breakout angle was expanded to account for the observed non linear shape, based on measurements made at small increments along the blasthole to capture variability of the overall geometry.This paper describes SHB testing campaigns conducted at two underground salt mines. Traditional reporting parameters (e.g. breakout angle, crater area) are presented in an enhanced approach by capturing their variation along the blasthole, and with respect to measured burden dimensions. A new crater model is proposed to better capture and represent the observed crater shape, and avoid the simplification of best-fitting triangular crater shapes. Results from the field campaigns are presented in details using LiDAR point clouds and SHB characteristic plots of the crater geometry. The crater model is calibrated from the test results to obtain site-specific burden-dependent trends of the crater shape. Two methods are then proposed for implementing SHB test results into blast pattern designs using the proposed crater model.

Simulation of arc crater formation and evolution on plasma facing materials

• A 2D axially symmetric arc crater model was developed by COMSOL software. • Formation and evolution of arc craters on PFMs were simulated and analyzed. • Refractory metals W and Mo are more difficult to be damaged by arcs than Cu and Al. Arc erosion on plasma facing materials in tokamak devices is a potential source of impurities and dust in plasma. A two dimensional axially symmetric COMSOL model with heat transfer, fluid dynamics including phase transition and surface tension effect has been used to describe the formation and evolution of arc craters on plasma facing materials. The formation and evolution of arc crater on W cathode is described in detail. The energy flux loading causes melting of central area within a few nanoseconds. Due to the gradients of incident pressure, the melted layer is extruded out, and thus forms the melt jets. The differences of the arc craters on several related materials in tokamaks under the same pressure and energy flux density are also discussed. The crater temperature of W and Mo is much higher than that of Cu and Al. And, the melting volume of refractory metals W and Mo is significantly lower than that of Cu and Al. Refractory metals are more difficult to be damaged by the arcs, and more suitable for plasma facing materials.

Study of cathode-spot crater and droplet formation in a vacuum arc

A 3D transient model of a cathode-spot crater and droplet formation in a vacuum arc is developed. The model includes mass, momentum, heat transfer (energy), current continuity and potential equations. Using the energy flux density, current density and pressure as external parameters, the shape of the cathode-spot crater and the temperature, velocity, potential and current density distributions at each time step are determined via numerical simulation. Under symmetrical conditions, the 3D simulation results are highly consistent with those from the previous 2D model. The new cathode spot tends to appear in the direction in which the protrusion is largest because the liquid-metal velocity is lower and the liquid-metal ridge radius is larger in this direction. The effect of the external transverse magnetic field is considered by using a symmetric space function to represent the pressure and energy flux density of the plasma cloud. Simulation results show that even small changes in the plasma cloud distribution have a significant impact on the cathode-spot crater process and droplet formation. Since the pressure is asymmetric, the crater becomes asymmetric and the new cathode spot tends to appear opposite to the direction of the Ampere force. Based on this phenomenon, a possible explanation for the retrograde motion phenomenon of cathode spots is proposed.

Numerical modeling of fracture in ceramic micro-particles and insights on ceramic retention during composite cold spray process

The retention and fragmentation of the polycrystalline ceramic particles have a significant influence on the properties of the cold sprayed coatings. In this computational study, polycrystalline ceramic models were developed which demonstrated that ceramic fragmentation and retention were influenced by particle grain sizes and their impact velocities. The underlying mechanisms of crack initiation and propagation were outlined. Larger grain sizes showed higher crater depths and lower rebounding velocities, while smaller grain sizes exhibited significantly lower fragmentation. Based on the results, an optimum grain size range was proposed for lower fragmentation and higher retention. Moreover, using multiple particles and first-layer crater models, the beneficial role of surrounding metal particles on reducing fragmentation has been clarified and compared to the experimental observations. The present work provides theoretical insights on the damage mechanism and retention of ceramics during metal-ceramic composite cold spraying.

Lunar Crater Models

Abstract This article traces the story of three amateur astronomers who created relief models to help them depict the changing illumination of certain lunar craters, examples of which can be found in UK museum collections today. English chemist Henry Blunt (1806–1853) adopted the emerging technology of electrotyping to reproduce and distribute his plaster model of the Eratosthenes crater to a wider audience. Scottish industrial engineer James Nasmyth (1808–1890) used a combination of drawing, modelling and photography to support his thesis on the volcanic origin of lunar craters in his popular book The Moon Considered … (1874). Spanish sculptor Dionis Renart (1878–1946) produced a series of plaster models for the Exposición General De Estudios Lunares (1912) that eventually came to Greenwich via the British selenographer Hugh Percy Wilkins (1896–1960). These three case studies provide us with valuable insights into the rationale behind the production, use and distribution of lunar crater models within amateur and popular astronomy.

Understanding Asteroid 16 Psyche’s composition through 3D impact crater modeling

Asteroid 16 Psyche is the largest M-type (metallic) Main Belt Asteroid (MBA). Radar albedo data indicate Psyche’s surface is rich in metallic content, but estimates for Psyche’s bulk structure vary widely, with bulk density estimates ranging from 1.4 ± 0.3 g/cm3 to 4.5 ± 1.4 g/cm3 and porosity estimates ranging from 30% to 70%. A forthcoming NASA discovery mission will visit Psyche. Narrowing the range of estimated compositions of Psyche prior to mission launch can help to determine the necessary tools for asteroid analysis. Psyche has two large impact structures in its Southern hemisphere, with estimated diameters from 50 km to 70 km and estimated depths up to 6.4 km. In this work, we present results from 2D and 3D hydrocode simulations of the largest of these impact structures. Through quantitative comparison of the simulated crater dimensions with measured values, our models suggest that Psyche is largely composed of porous, metallic material. In addition, to match the crater dimensions, our simulations indicate that the angle of impact was significantly altered from vertical by 45–60 degrees.

Relative Crater Scaling Between the Major Moons of Saturn: Implications for Planetocentric Cratering and the Surface Age of Titan

AbstractThe chronology of the moons of Saturn, especially Titan, has been limited by a lack of strong constraints on the cratering rate, low number statistics for small‐N counts of large‐diameter craters, and uncertainty about whether impactors are mostly heliocentric impactors orbiting the Sun or planetocentric impactors orbiting Saturn itself. Here, I propose to address these three problems. Instead of looking for an absolute cratering rate, I focus on the relative crater densities, calculating scaling relationships between the moons. I update crater analysis methodology by numerically modeling probability density functions of the uncertainty of crater density, enabling me to accurately assess the error of even single‐crater observations. Using these updated statistics, I show how the heliocentric cratering model leads to a dramatic increase in relative crater density for Mimas, Tethys, Dione, Rhea, and Iapetus with distance from Saturn. Under this model, the surface age of Titan is probably older than the cratered plains of Mimas—implying a very low erosion rate and minimal endogenic resurfacing on Titan. I explore possible explanations, concluding that the likeliest explanation is planetocentric cratering, although saturation effects cannot be ruled out. Under the planetocentric model, the relative crater densities of the cratered plains of Mimas, Tethys, Dione, Rhea, and Iapetus are all very close, with the relative crater density at Titan between 1 and 2 orders of magnitude lower. Under planetocentric cratering, the cratering rate on Titan allows for vigorous erosion and endogenic resurfacing.

Explosion force and shape fitting based modelling of dynamic virtual crater deformation

The dynamic deformation of virtual terrain is an important research content to improve the dynamic adaptability of virtual geographic environment, which can support the research of disaster simulation, combat simulation and so on. It is also a novel method to support human-environment interaction research in the community of geographic information science. In this paper, the dynamic generation of bomb crater is taken as an example to study the construction method of virtual terrain deformation model. Starting from the formation process of crater in explosive mechanics, the deformation model is coupled with the calculation method to control the radius and depth of crater shape. Through the method of geometric fitting, the shape of crater is modeled in different regions and the basic crater model is established. On the basis of the basic model, the incidence angle of projectile is introduced to build the relationship model between crater deformation and incidence angle of projectile. Based on the Digital Terrain Model (DTM), the terrain data model is improved by coupling the radius coefficient and depth coefficient related to the geological characteristics, and the crater shape algorithm reflecting the geological characteristics is proposed. Finally, the Perlin noise is added to realize the disturbance of the elevation value of each position point in the crater zone. The simulation environment of crater deformation is established by Unity, and the crater model is simulated and verified. The results show that the crater model can basically reflect the impact of different projectile incidence angle, explosion equivalent and geological characteristics. The deformation state of crater is similar to the actual situation. The research results can provide support for the simulation of the dynamic process of the crater produced by the projectile touch-down explosion in the virtual battlefield environment.

Quantitative assessment of uncertainties in modeled crater retention ages on Mars

With increasing high-resolution coverage of Mars' surface, crater count analysis is being used to estimate the formative ages of small depositional features (<1000 km2) to constrain timing of climate-driven events. We introduce a probabilistic cratering model that quantifies how modeled age estimates vary strongly with crater obliteration rates (β, defined as the combined rate of erosion and infilling), minimum crater diameter counted, and surface area size. Model results show that crater obliteration introduces significant uncertainty on small surfaces, where moderate obliteration rates (β ~ 25 nm a−1) require surface areas of about 10,000 km2 to date 2 to 3 Ga surfaces accurately, and strongly obliterated surfaces (β = 200 nm a−1) require surface areas up to 100,000 km2. In practice, smaller areas can nonetheless be analyzed probabilistically by estimating a range of likely obliteration rate and modeled age combinations and optimizing these values relative to observed crater count data, resulting in a distribution of possible modeled surface ages and associated β. We demonstrate this method using data from the Coprates Chasma landslide (~200 km2) and numerous fan and delta deposits in the Gale crater region. Although the deposits in and around Gale are <1000 km2, a probabilistic analysis enables us to suggest that deltaic deposits in and near Gale have a higher probability of being older (~>3 Ga) than nearby fans (~1–3 Ga). This analysis provides a simple quantitative framework for assigning probable surface age ranges for small features on Mars.

The Tsiolkovskiy crater landslide, the moon: An LROC view

Evidence suggests that the lobate flow feature that extends ~72 km outward from the western rim of Tsiolkovskiy crater is a long runout landslide. This landslide exhibits three (possibly four) morphologically different parts, likely caused by local conditions. All of these, plus the ejecta of Tsiolkovskiy crater, and its mare fill are approximately of the same crater model age, i.e., ~3.55 ± 0.1 Ga. The enormous size of this landslide is unique on the Moon and is a result of a combination of several geometric factors (e.g., its location relative to Fermi crater), and that Tsiolkovskiy crater was an oblique impact that produced an ejecta forbidden zone on its western side (Schultz, 1976). The landslide formed in this ejecta free zone as the rim of Tsiolkovskiy collapsed and its debris flowed across the relatively smooth, flat floor of Fermi crater. In this location, it could be easily identified as a landslide and not ejecta. Its mobility and coefficient of friction are similar to landslides in Valles Marineris on Mars, but less than wet or even dry terrestrial natural flows. This suggests that the Mars landslides may have been emplaced dry. The high density of small craters on the landslide is likely an illusion caused by the effects of age related differences in regolith thickness on crater morphology, and the presence of the abundant young, circular secondary craters produce by debris ejected from distant fresh craters.

Thickness of Lunar Mare Basalts: New Results Based on Modeling the Degradation of Partially Buried Craters

AbstractPartially buried craters on the Moon are those craters whose distal ejecta are covered by lava flows and where the crater rim crest still protrudes above the mare plain. Based on the difference in rim heights between a partially buried crater and an unburied crater, previous studies estimated the thicknesses of the lunar mare basalts. However, these studies did not consider the erosion of the crater rim height, which can result in an overestimate in the derived thickness. By using recent high‐resolution topographic data, we report a basalt thickness estimation method based on numerically modeling the topographic degradation of partially buried craters. We identified 661 buried craters over the lunar surface, and their spatial distribution suggests a preferential occurrence along the mare‐highland boundaries. An elevation model of fresh lunar craters was derived, and the topographic diffusion equation was used to model crater degradation. By modeling the formation, degradation, and flooding of partially buried craters, basalt thicknesses were estimated for 41 mare craters whose rims are completely exposed. The resulting mare basalt thicknesses vary from 33 to 455 m, with a median value of 105 m that is 95 m smaller than that derived when not considering crater degradation. The estimated eruption rate of lunar mare basalts is found to have peaked at 3.4 Ga and then decreased with time, indicating a progressive cooling of the lunar interior. As a by‐product from the crater degradation model, our results suggest that the topographic diffusivity of lunar craters increases with diameter.

Thermal model of lava in Mt. Agung during December 2017 episodes derived from Integrated SENTINEL 2A and ASTER remote sensing datasets

In the beginning of December 2017, Mt. Agung eruption powered down to minor ash emissions and on the middle of December, aerial photographs of the crater were taken by Indonesia Centre of Volcanology and Geological Hazard Mitigation (PVMBG) showing a steadily growing lava occupying approximately one third of the crater. 3D digital elevation model (DEM) of crater were created by PVMBG during and before the eruption, corresponded to lava volume around 2 x 10−2 km3 has been filled the crater. Here we present a method for deriving thermal model within the lava during eruption on 8 and 9 December 2017 using observations from multi infrared satellite SENTINEL 2A and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). We use Thermal Eruption Index (TEI) based on the Shortwave infrared (SWIR) on SENTINEL 2A and Thermal Infrared (TIR) on ASTER, allowing us to differentiate thermal domain within the lava. This study has successfully produced model of sub-pixel temperature (Th), radiant flux (Φrad) and crust thickness model of lava (Δh). The subpixel temperature and radiant flux during the eruption is in the range 655 to 975 °C and 179 MW respectively. The crust thickness model of the lava in the range of 9 to 14 m and the total volume of lava crust during this period is estimated at 3 x 10−3 km3. The combination of infrared satellite remote sensing data shows a potential for fast and efficient classification of difference thermal domains and derive thermal model of lava.