Crater Cavity Research Articles

What Is a Polygonal Impact Crater? A Proposed Framework Toward Quantifying Crater Shapes

AbstractImpact craters are used for a wide array of investigations of planetary surfaces. A crater form that is somewhat rare, forming only ∼10% of impact craters, is the polygonal impact crater (or PIC). These craters have been visually, manually identified as having at least two rim segments that are best represented as straight lines. Such straight lines or edges are most often used to infer details about the subsurface crust where faults control the structure of the crater cavity as it formed. The PIC literature is scant, but almost exclusively these craters are identified manually, and the potentially straight edges are classified and measured manually. The reliance on human subjectivity in both the identification and measurement motivated us to design a more objective algorithm to fit the crater rim shape, measure any straight edges, and measure joint angles between straight edges. The developed code uses a Monte Carlo approach from a user‐input number of edges to first find a reasonable shape from purely random possible shapes; it then uses an iterative Monte Carlo approach to improve the shape until a minimum difference between the shape and rim trace is found. It returns the result in a concise, parameterized form. This code is presented as a first step because, while we experimented with several different metrics, we could not find one that could consistently, objectively return an answer that stated which shape for a given crater was the best; this objective metric is an area for future improvement.

Fabrication of micro patterns on BaTiO3:Er3+/Yb3+ perovskite films by femtosecond laser micromachining

Femtosecond lasers currently show much promise as potential sources for the fabrication of optical and photonic devices, displaying high performance due to their high resolution, excellent geometric flexibility, and low collateral damage. In particular, devices displaying high performance based on BaTiO3:Er3+/Yb3+ (BTEY) films have been widely investigated, promising for the innovation of perovskite patterning applications. Herein, we fabricated BTEY perovskite films by spin coating at room temperature. XRD pattern and Raman spectroscopy analysis of the BTEY films revealed a tetragonal crystal structure. The study of Williamson-Hall's method calculated the strain and crystallite size for the BTEY film. Different parameters in the exploiting cylindrical focusing of an fs-laser were adopted to modulate the crater cavity of patterning, which gives the opportunities to evaluate their impact on the energy ablation threshold (Eth). It was found that cavity radius is proportional to the energy cross-section, thus providing wide range dependence of damaged spot size versus pulse energy. The Eth was measured using Liu's method, determining a value of Eth that decreased from 33.4 nJ to 22.4 nJ when the number of applied laser pulses per spot increased. It is found that the number of pulses per spot low possesses the best performance, successfully producing highly uniform patterning. Moreover, the evolution with the number of pulses also revealed changes in the surface morphology of the crater cavity via AFM and scanning confocal fluorescence microscopy (SCFM) analysis. These results are crucial for determining the Eth required to damage the material, understating the driving mechanism of formations of cavity profile surfaces, and changes in their optics properties in the edges owing to the balling effects and structural defects.

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.

Methane-saturated Layers Limit the Observability of Impact Craters on Titan

Abstract As the only icy satellite with a thick atmosphere and liquids on its surface, Titan represents a unique end-member to study the impact cratering process. Unlike craters on other Saturnian satellites, Titan’s craters are preferentially located in high-elevation regions near the equator. This led to the hypothesis that the presence of liquid methane in Titan’s lowlands affects crater morphology, making it difficult to identify. This is because surfaces covered by weak fluid-saturated sediment limit the topographic expression of impact craters, as sediment moves into the crater cavity shortly after formation. Here we simulate crater-forming impacts on Titan’s surface, exploring how a methane-saturated layer overlying a methane-clathrate layer affects crater formation. Our numerical results show that impacts form smaller craters in a methane-clathrate basement than a water-ice basement due to the differences in strength. We find that the addition of a methane-saturated layer atop this basement reduces crater depths and influences crater morphology. The morphology of impact craters formed in a thin methane-saturated layer is similar to that in a “dry” target, but a thick saturated layer produces an impact structure with little to no topography. A thick methane-saturated layer (thicker than 40% of the impactor diameter) could explain the dearth of craters in the low-elevation regions on Titan.

A contribution to numerical prediction of surface damage and residual stresses on die-sinking EDM of Ti6Al4V

A numerical simulation under plane-strain assumption of residual stresses and damage on titanium alloy Ti6Al4V in die-sinking electrical discharge machining (EDM) process is presented using Johnson–Cook (J–C) model and dynamic explicit temperature-displacement algorithm. A special attention is given to model the damaged thermo-mechanical behavior of EDMed Ti6Al4V alloy while considering the ductile damage evolution via a fully uncoupled damage formulation. A rigorous selection method including analytical and finite-element (FE) computations of tensile fracture behavior with thermal effect is proposed for suitable selection of J–C model parameters for the grade of Ti6Al4V alloy under investigation. The relationships between the machining parameters and both the heat flux density and the available sparking radius are considered for defining sparking analysis input. For a selected set of machining settings, the residual stresses and surface damage profiles were retrieved at the end of a cooling analysis. It has been concluded that J–C constitutive model can be used to describe material damaged thermo-plastic behavior under die-sinking EDM process conditions and thereby forecast temperature distribution, crater cavity shape, thermally induced residual stresses, white layer thickness and EDM thermal cracks formation. Unusually, an approach including damage criterion was proposed for assessment of both the geometry of crater cavity and the thickness of white layer and compared to based-on temperature criterion classical approach. Thus, numerical simulation of damage in die-sinking EDM offers a new insight into the mechanism of surface damage creation and helps to find out such phenomenon very precociously, which is otherwise difficult to access by experiment, such as surface crack formation due to damage mechanism as triggered in sparking phase and which was re-established in cooling. The numerical model yields reliable results for residual stresses profiles when compared with titanium alloy Ti6Al4V experimental results available in literature in the same machining conditions.

Investigation of in situ synthesized TiB2 particles in iron-based composite coatings processed by hybrid submerged arc welding

Abstract In the study for this contribution, production of in situ synthesized TiB2 particles in iron-based composite coatings using four different submerged arc welding powders (fluxes) containing increasing amounts of ferrotitanium and ferroboron with S1 welding wire, were targeted. For this purpose, coating deposition was carried out to improve the hardness and wear properties of the AISI 1020 steel surfaces using hybrid submerged arc welding. In hybrid submerged arc welding, the welding pool is protected by both welding powders and an argon gas atmosphere. To examine the composite coatings, visual, chemical, microstructural analyses and hardness and wear tests were carried out. With the use of increasing amounts of ferrotitanium and ferroboron in the welding powders, it was observed that the microstructure of the coatings changed in terms of TiB2 particle geometries such as rectangular and hexagonal; volume fractions of TiB2 particles in the coating microstructures increased; hardness values of coatings were enhanced from 34 HRC to 41 HRC; the wear resistance of the coatings improved, and worn surface images of the coatings caused by the counter body changed from continuous with deep scratches to discontinuous with fine scratches and crater cavities.

Morphologic differences in radial grooves on martian layered (fluidized) ejecta: Implications for emplacement processes and conditions

Detailed morphologic and morphometric analysis of the radial grooves on Martian layered ejecta indicates that the grooves fall into three groups that correlate with different types of layered ejecta craters. We collected over 16,000 width and length measurements of 2402 radial grooves on the inner ejecta layers of 36 relatively fresh, layered ejecta craters. These include seven single layered ejecta craters (SLE), seven double layered Type-2 (DLE Type-2), ten double ejecta layer Type-1 (DLE-Type-1), and twelve multiple ejecta layer (MLE) test craters. These test craters are in the diameter range 8.3 km – 38.8 km for latitudes ranging from 45oS to 54oN. Radial grooves resembling longitudinal grooves in landslides throughout the solar system occur on all ejecta layers of SLE, DLE Type-2, and MLE craters (i.e., SDM grooves). This leads us to propose that SDM grooves are structures formed in flowing ejecta by the same processes that produce longitudinal grooves in landslides (e.g., shear and divergent flow). In contrast, the radial grooves on the inner and outer ejecta layers of DLE Type-1 are morphologically and morphometrically different from one another and from SDM grooves. The only type of geophysical flows that form grooves similar to grooves on the inner ejecta layers of DLE Type-1 craters are ones produced by high velocity (i.e., supersonic) blast surges associated with explosive volcanic eruptions (e.g., that occurred during the May 18th1980 eruption of Mount St. Helens USA). This leads us to propose that these Martian grooves are produced by high-speed outflow of particles and gas towards the last phase of crater formation. Furthermore, we propose that this high speed flow is generated when volatile-rich target materials slide into the crater cavity to mix with hot impactite. This generates a fuel-coolant explosion that creates a blast surge that subsequently produces the grooves on the inner ejecta layer. In addition, as the velocity of the outflow drops to subsonic outward of the inner ejecta layer, both erosion and deposition processes operate that result in deposition of a thin layer of material that contains channel-like grooves that are unique to this ejecta layer of this type of crater. This thin deposit is found on the outer ejecta layers, and beyond (on the terrain surrounding fresh DLE Type-1 craters). The production of these grooves on DLE Type-1 ejecta layers likely destroys and/or masks SDM grooves that may have initially formed on DLE Type-1 ejecta layers when they were initially emplaced as dense ground hugging flows.

Evidence for shock provides insight into the formation of the central elevated area in the Dhala impact structure, India

AbstractThe central elevated area is a postimpact morphological landmark in the otherwise flat eroded remnant of the Dhala impact structure, India. Its base is the Bundelkhand granitic complex followed by beds of Dhala and Kaimur Formations. The beds of the Dhala and Kaimur Formation present typical sedimentary textures and structures such as cross‐bedding. The grains are angular, sorting is moderate to poor, and brittle–ductile deformation of the protolith is still preserved in some grains. This reveals a short distance of transport. Detailed microscopy and U‐stage measurements confirm planar deformational features (PDFs) oriented (0001) and {10–13} in few quartz grains. Based on these facts, it is suggested that the quartz with PDFs was shocked, ejected out of the crater, and deposited near the crater cavity. Reworking of the ejecta blanket redeposited these quartz grains to their present location. Relatively few shocked grains in the rocks favor a postimpact fluvial process over impact resurge.

Central uplift collapse in acoustically fluidized granular targets: Insights from analog modeling

AbstractDepending on their sizes, impact craters have either simple or complex geometries. Peak‐ring craters such as the Chicxulub impact structure possess a single interior ring of peaks and hills and a flat interior floor. The exact mechanisms leading to the formation of a morphological peak‐ring are still a matter of debate. In this study, analog modeling was used to study the flow field of a collapsing central uplift. A 3‐D‐printed cast was used to bring the analog material in the shape of an overheightened central uplift that was based on numerical modeling. The cast was then quickly removed and the central peak collapsed, forming a flattened broad mound that spread out onto the annular moat of the crater cavity. A subwoofer was used to fluidize the granular target material. The kinematics of the collapse were analyzed with the aid of particle image velocimetry, revealing a downward and outward collapse of the central uplift. This mode of collapse is partly in agreement with numerical models, in particular for the initial and middle phases. The overthrusting of the collapsing central peak onto the inward moving crater floor predicted by numerical modeling was observed, though to a lesser degree. A peak‐ring, however, could not be reproduced since the collapse came to a halt before the central peak was completely leveled. Nevertheless, the method provides qualitative insights into the kinematics of collapse phenomena. This experimental study provides independent support of the theory of acoustic fluidization, in addition to numerical simulations.

2019 Barringer Medal for Mark Cintala

2019 Barringer Medal for Mark Cintala

The Role of Breccia Lenses in Regolith Generation From the Formation of Small, Simple Craters: Application to the Apollo 15 Landing Site

AbstractImpact cratering is likely a primary agent of regolith generation on airless bodies. Regolith production via impact cratering has long been a key topic of study since the Apollo era. The evolution of regolith due to impact cratering, however, is not well understood. A better formulation is needed to help quantify the formation mechanism and timescale of regolith evolution. Here we propose an analytically derived stochastic model that describes the evolution of regolith generated by small, simple craters. We account for ejecta blanketing as well as regolith infilling of the transient crater cavity. Our results show that the regolith infilling plays a key role in producing regolith. Our model demonstrates that because of the stochastic nature of impact cratering, the regolith thickness varies laterally, which is consistent with earlier work. We apply this analytical model to the regolith evolution at the Apollo 15 site. The regolith thickness is computed considering the observed crater size‐frequency distribution of small, simple lunar craters (< 381 m in radius for ejecta blanketing and <100 m in radius for the regolith infilling). Allowing for some amount of regolith coming from the outside of the area, our result is consistent with an empirical result from the Apollo 15 seismic experiment. Finally, we find that the timescale of regolith growth is longer than that of crater equilibrium, implying that even if crater equilibrium is observed on a cratered surface, it is likely that the regolith thickness is still evolving due to additional impact craters.

Optimizing laser crater enhanced Raman scattering spectroscopy

The laser crater enhanced Raman scattering (LCERS) spectroscopy technique has been systematically studied for chosen sampling strategy and influence of powder material properties on spectra intensity enhancement. The same nanosecond pulsed solid state Nd:YAG laser (532 nm, 10 ns, 0.1–1.5 mJ/pulse) was used for laser crater production and Raman scattering experiments for l-aspartic acid powder. Increased sampling area inside crater cavity is the key factor for Raman signal improvement for the LCERS technique, thus Raman signal enhancement was studied as a function of numerous experimental parameters including lens-to-sample distance, wavelength (532 and 1064 nm) and laser pulse energy utilized for crater production. Combining laser pulses of 1064 and 532 nm wavelengths for crater ablation was shown to be an effective way for additional LCERS signal improvement. Powder material properties (particle size distribution, powder compactness) were demonstrated to affect LCERS measurements with better results achieved for smaller particles and lower compactness.

Numerical simulation of multi-spark electric discharge machining analysis for Ti6Al4V alloy drilling

In this paper a thermal model has been developed for numerically analyzing the multi spark EDM drilling mechanism using finite element methods. The sequential multi electric sparks for drilling process provides heat flux for simulation model. The thermal model also envelopes realistic considerations like effective latent heat of melting, Gaussian heat distribution of heat source, spark radius equation encompassing discharge current and pulse on time, etc for predicting the rate of metal removal and shape of the drilled hole cavity. This developed model has been used to determine the effect of parameters used as input for EDM process like discharge current, voltage, pulse duration and duty cycle on MRR and crater cavity. The impact of discharge energy on MRR is studied and behaviors of crater depth on variance in input operation parameters are examined. The results obtained could be used to carry out experiments and develop an empirical model which could predict results for operation output parameters like MRR, TWR and surface roughness in advance.

Prediction of root mean square surface roughness in low discharge energy die-sinking EDM process considering the effects of successive discharges and plasma flushing efficiency

In this paper, a detailed novel approach is presented to adequately predict the root mean square surface roughness parameter (Rq) in electro-discharge machining (EDM) process by taking into account the effects of consecutive discharges and plasma flushing efficiency (PFE). The procedure first starts simulating crater formation due to a single spark based on more realistic assumptions using finite element method (FEM). The Abaqus FEM software has been employed to estimate the transient temperature distribution, crater cavity dimensions and volume to obtain the removal rate per discharge pulse on AISI 304 stainless steel as the work piece. To evaluate the amounts of (PFEs), the theoretically ideal material removal rates (MRRs) were compared with a set of experimental MRRs under the same low discharge energy zone (less than 100mJ) typically used for finishing purposes. Finally, an iterative-based statistical approach derived from the concept of normal distribution of surface heights along with the impacts of each crater cavity formed due to repetitive discharges on the surface profile have properly been formulated to simulate the final work piece surface roughness achieved under the erosive effects of multiple discharges. The simulated values of Rq have also been validated experimentally. Reasonable agreement has been attained which confirms the robustness and correctness of proposed methodology.

Impact velocity dependence of transient cratering growth

AbstractThe present paper describes observations of crater growth for various impact velocities up to ∼6 km s−1. Spherical polycarbonate projectiles (4.76 mm) were impacted vertically into dry sand targets at impact velocities vi ranging from 0.7 to ∼6 km s−1, and the temporal change (diameter growth) in diameter of crater cavities was measured by a high‐speed profilometer with 2000 frames per second. Our data show that the diameter growth follows a power law relation at the early stages, but the data at the later stages deviate from the power law relation. It is also shown that the power law exponent at the early stages decreases with increasing vi, indicating a possibility that the growth rate of the transient crater cavity decreases with increasing vi. On the other hand, the power law relation for final crater sizes in our data is consistent with the classical scaling relation for final crater sizes, which is thought to be independent of vi. Thus, our data may suggest that there is a difference in the power law behavior between the crater growth and the final crater sizes.

Impact cratering on slopes

The majority of impact craters have circular outlines and axially symmetric morphologies. Deviation from crater circularity is caused by either target heterogeneity, a very oblique impact incidence, post-impact deformation, or by topography. Here, we investigate the effect of topography on crater formation and systematically study impact cratering processes on inclined hillsides up to 25° slope utilizing analogue experiments. A spring-driven air gun mounted in a vertical position shoots into three different types of granular bulk solids (two sorts of glass beads, quartz sand) to emulate impact cratering on slopes. In all, 170 experiments were conducted. The transient crater develops roughly symmetrically perpendicular to the slope plane, resulting in higher ejection angles uphill than downhill when measured with respect to a horizontal plane. Craters become increasingly elliptical with increasing slope angle. At slope angles close to angle of repose of the respective bulk solids, aspect ratios of the craters reach ∼1.7. Uphill-downhill cross sections become increasingly asymmetric, the depth-diameter ratio of the craters decreases, and the deepest point shifts downhill with increasing slope angle. Mass wasting is initiated both in the uphill and downhill sectors of the crater rim. For steep slopes the landslides that emanate from the uphill rim can overshoot the crater cavity and superpose the downhill crater rim in a narrow tongue. Mass wasting initiated at the downhill sector forms broader and shallower tongues and is triggered by the deposition of ejecta on the inclined slope. Our experiments help to explain asymmetric crater morphologies observed on asteroids such as Ceres, Vesta, Lutetia, and also on Mars.

Timescales of fluvial activity and intermittency in Milna Crater, Mars

Milna Crater, Mars (23.4S, 12.3W) exhibits signs of fluvial modification early in Mars history, including a large multi-lobed fan deposit cut by several sinuous valleys. We describe the past hydrologic conditions in Milna and the surrounding area, including a potential lake with a volume of 50km3. We also introduce new methods (i) to calculate the timescale of sediment deposition by considering fluvial sediment input into the entire crater while accounting for non-fluvial input, and (ii) to place improved constraints on the channel dimensions through which sediment was delivered to Milna by comparing to the dimensions of inner channels found in valleys in the region surrounding Milna. By calculating the flux of fluid and sediment into the crater, we find that the crater cavity was flooded for at least months and that the time of active fluvial sediment transport without hiatus is on the order of decades to centuries, with a preferred timescale of centuries. We also calculate the total amount of water required to transport the volume of sediment we measure in Milna and conclude that impacts alone are likely insufficient to deliver enough water to Milna to allow the sedimentary fill we see.Combining the timescales of fluvial activity in the adjacent Paraná Valles with estimates for global Noachian erosion rates, we calculate an intermittency factor for fluvial activity of ∼0.01–0.1% during 105–106yr near the Noachian–Hesperian boundary in the Paraná Valles region. These values are comparable to arid climates on Earth where the majority of fluvial sedimentary transport takes place during floods with multi-year to decadal recurrence intervals. Our calculations of intermittency help to quantitatively reconcile the divergent estimates of the short and long timescales of fluvial activity on Mars reported in the literature.

In situ flash X-ray observation of projectile penetration processes and crater cavity growth in porous gypsum target analogous to low-density asteroids

Recent studies of impact craters formed on low-density asteroids led to the proposal of a new crater formation mechanism dominated by pore collapse and compaction. Thus, it is important to study the crater formation process associated with the projectile penetration on porous cohesive targets. Laboratory impact experiments were conducted for a porous gypsum target with porosity of 50%, and flash X-rays were used to visualize the interior of the target for in situ observation of crater formation and projectile penetration. Spherical projectiles made of three different materials, stainless steel, aluminum, and nylon were impacted at 1.9–2.4km/s (low-velocity impact) and 5.6–6.4km/s (high-velocity impact) by using a two-stage light-gas gun. Two imaging plates were used to take two X-ray images at a different delay time from the impact moment for one shot. Two types of crater cavity shape were found on the porous gypsum target, that is, penetration holes or hemispherical cavities, depending on the projectile size and density, and the impact velocity. The drag coefficient of a projectile was determined by measuring the penetration depth changing with time, and we found that it was closely related to the crater cavity shape: it was about 0.9 for a penetration hole, while it was 2.3–3.9 for a hemispherical cavity. This large value for a hemispherical cavity could have been caused by the deformation or the disruption of the projectile. The cratering efficiency, ρtVcr(t)/mp, was found to have a power law relationship to the scaling time for crater growth, πt=vit/rp, where vi is the impact velocity, rp is the projectile radius, and t is the time after the impact, and all data for stainless steel and aluminum projectiles merged completely and could be fitted by a power-law equation of ρtVcr(t)/mp=2.69×10-1πt1.10. Furthermore, the scaled crater volume, πV=Vcr_finalρt/mp, where Vcr_final is the final crater cavity volume, ρt is the target density, and mp is the projectile mass, was successfully fitted by a power law equation when another scaling parameter was used for the crater formation in strength regime, πY=Yt/ρtvi2, where Yt is the target material strength, as follows: πV=1.69×10-1πY-0.51. As a result, the crater formed on porous gypsum was revealed to be more than one order of magnitude smaller than that formed on basalt. Based on our experimental results, which visualize how crater cavities on porous cohesive materials grow with projectile penetration, we are able to discuss compression and excavation processes during crater formation quantitatively. This observation enables us to investigate and revise numerical models and crater scaling laws for high-velocity impacts into porous cohesive materials.

An investigation of Martian northern high‐latitude and polar impact crater interiors: Atypical interior topographic features and cavity wall slopes

Abstract– We examine Martian northern high‐latitude and polar impact craters (NPICs) to better understand the north polar materials and polar processes. We examine topographic characteristics for 346 NPICs and compare them to global fit data (e.g., Garvin et al. 2003; Boyce and Garbeil 2007) as well as to a small set (N = 92) of southern high‐latitude and polar impact craters (SPICs). We find that the NPIC population above 57° N is significantly shallower than the global crater population. This suggests that the NPICs (1) were initially shallow due to target properties of polar geologic units; (2) were once deeper, but have been infilled due to polar processes; or (3) a combination of both. Indeed, many of the NPICs exhibit considerable noncentral peak interior topographic features (IFTs), which may be indicative of infilling processes. The NPIC IFTs also appear to display trends in their preferential orientation within the crater cavity; some SPICs display similar interior features, but do not show a clear preference in their orientation within the crater cavity. In addition, the NPIC population displays cavity wall slope trends that seem to indicate steepening of slopes with increasing crater diameter in comparison to the global slope trend (Garvin et al. 2003). These trends suggest that the NPICs are unique in their geometry when compared to the global data set as well as with the SPICs further indicating that the north polar region may exhibit target properties and polar processes not seen in the south polar region or elsewhere on Mars.

Low energy deposition in the Chicxulub crater during the impact to post-impact transition

The crater fill units that were deposited during the terminal stages of the formation of the shallow marine Chicxulub crater in northern Yucatan were interpreted by some authors as products of a catastrophic resurge of water. This interpretation contrasts markedly with the dominant sand grain size <300µm and the abundant small-scale current cross bedding structures indicative of low energy deposition. To solve this discrepancy we applied first principles of physical sedimentology in an analysis of grain size and sedimentary structures to determine current velocities and minimum water depths required to generate the observed sedimentary bedforms. We combine this approach with numerical modeling of crater formation in order to explore the dimensions of the ejecta ring wall being formed by a Chicxulub impactor in water depths of 1000m. We find that the ejecta wall reaches heights in the order of 1200m above sea floor and 200m above sea level. It thus prevented the resurge of water into the crater cavity and consequently also the subsequent formation of a collapse wave. The ring wall significantly retarded the refilling of the crater cavity with seawater, and refilling took place by permeation through and localized erosion of the ring wall. This resulted in low-energy currents with velocities between 1.5 and 0.18ms−1 slowly reentering the crater and depositing the cm-scale, low energy laminated and crossbedded sandy terminal impact deposits.