Meteoroid Impacts Research Articles

Geology of the Eastern Barberton Greenstone Belt, South Africa: Early Deformation and the Role of Large Meteor Impacts

The eastern Barberton Greenstone Belt (BGB) includes four stratigraphic and structural divisions: from northwest to southeast, the Mlumati, Manzimnyama, and Paulus Synclines and the Emlembe Belt. All are made up largely of sedimentary rocks of the Fig Tree Group separated by antiformal belts of sheared Onverwacht Group komatiitic rocks. Fig Tree rocks in the Mlumati and Manzimnyama Synclines are mostly chemically precipitated banded iron formation (BIF) and banded ferruginous chert (BFC) with a major siliciclastic unit, the Gelegela Grit, composed of quartz-poor (<5% monocrystalline quartz, Qm) volcaniclastic sandstone showing abundant ~3.445–3.455 Ga detrital zircons. The Paulus Syncline is dominated by shale containing in the upper half chert-clast conglomerate and sparse lithic sandstone (Qm<10%) but includes near the middle lenticular units up to unit 30 m thick of quartz-rich (Qm >50%) sandstone. The Emlembe Belt consists largely of chert-clast conglomerate and quartz-bearing (Qm = 10–50%) sandstone. The Paulus and Emlembe belts show detrital zircon age peaks at ~3.295–3.275 Ga and ~3.445–3.455 Ga. While exhibiting overall similar stratigraphic development and detrital zircon ages, Fig Tree rocks in these belts show contrasting compositions and sediment sources. They do not represent parts a single basin or fairway of sediment transport and deposition. Fig Tree siliciclastic rocks mark the first deformation, uplift, and erosion in the BGB. However, the thinness of Fig Tree strata, mostly less than 1000 m, and rapid facies changes argue that deformation involved local uplifts and small basins that accumulated thin sedimentary sequences. We suggest that early Fig Tree deformation is consistent with crustal disruption triggered by large meteor impacts, starting perhaps as early as ~3.277 Ga but certainly by ~3.260 Ga. The Fig Tree Group may record a cluster of impacts that fragmented and destabilized a long-lived crust followed during later or post-Fig Tree time by tectonic uplift and orogeny.

Determining Peak Shock Pressure and Cratering due to Hypervelocity Meteoroid Impact on Lunar Structures for Engineering Design

Determining Peak Shock Pressure and Cratering due to Hypervelocity Meteoroid Impact on Lunar Structures for Engineering Design

Water Generation on the Moon from Solar Wind and Meteoroid Impacts

The kinetics of water formation on the lunar surface from impact-driven melts (IM) of meteoroids and recombinative desorption (RD) of solar-wind-implanted regolith grains is assessed. The ratio of water generated from RD:IM is ultimately controlled by the diffusion constant of the implanted defects. Higher diffusion activation energies of hydroxyls (-OH) result in more trapping of the implanted defects and, consequently, higher water production from IM versus RD. At diffusion activation energies >1 eV, water production from RD is negligible and IM is the dominant channel. Our results suggest that RD can be associated with the observed latitude and diurnal dependence but RD and/or micrometeorite IM are not major contributors to the water ice observed within the permanently shadowed regions (PSRs). This suggests that volcanic and/or delivery via large impactors are the more likely major sources of water on the Moon. However, our model generally agrees with the observed latitudinal dependence of the inferred OH/H2O and the overall diurnal trend from orbital observations in the infrared. In addition, our results also suggest that micrometeorites are responsible for the high content of molecular water in the glass of regolith grains.

An estimate of the impact rate on Mars from statistics of very-high-frequency marsquakes

The number density of impact craters on a planetary surface is used to determine its age, which requires a model for the production rate of craters of different sizes. On Mars, however, estimates of the production rate of small craters (<60 m) from orbital imagery and from extrapolation of lunar impact data do not match. Here we provide a new independent estimate of the impact rate by analysing the seismic events recorded by the seismometer onboard NASA’s InSight lander. Some previously confirmed seismically detected impacts are part of a larger class of marsquakes (very high frequency, VF). Although a non-impact origin cannot be definitively excluded for each VF event, we show that the VF class as a whole is plausibly caused by meteorite impacts. We use an empirical scaling relationship to convert between seismic moment and crater diameter. Applying area and time corrections to derive a global impact rate, we find that 280–360 craters >8 m diameter are formed globally per year, consistent with previously published chronology model rates and above the rates derived from freshly imaged craters. Our work shows that seismology is an effective tool for determining meteoroid impact rates and complements other methods such as orbital imaging.

Development of ballistic limit equations in support of the Mars sample return mission

NASA and ESA are currently planning the Mars Sample Return campaign, comprising missions whose combined objective is to bring the first samples of Mars material back to Earth for detailed study. Until recently, the NASA-ESA plan was to return samples to Earth using three missions. The final component, the Earth Entry System (EES), will bring the Mars samples back to the Earth, where it will land following safe entry through the Earth's atmosphere. There is a concern regarding the risk of biological contamination of the Earth's biosphere from returned Mars samples if, for example, the structural integrity of the EES were compromised during its return mission due to a perforation of a critical surface resulting from a high-speed meteoroid impact. To assess the risks associated with such an event, NASA is developing equations that predict the damage that various EES elements will sustain as a result of such an impact, as well as equations that predict whether or not a particular system will sustain a critical failure following such an impact. In this paper, we review recent progress in the development of such equations for the EES forebody and the EES aftbody, the two elements of the EES that are most exposed to the meteoroid environment. Limitations of the BLEs are also discussed, which can also be used to further inform the next steps in the BLE development.

The Dimorphos ejecta plume properties revealed by LICIACube.

The Double Asteroid Redirection Test (DART) had an impact with Dimorphos (a satellite of the asteroid Didymos) on 26 September 20221. Ground-based observations showed that the Didymos system brightened by a factor of 8.3 after the impact because of ejecta, returning to the pre-impact brightness 23.7 days afterwards2. Hubble Space Telescope observations made from 15 minutes after impact to 18.5 days after, with a spatial resolution of 2.1 kilometres per pixel, showed a complex evolution of the ejecta3, consistent with other asteroid impact events. The momentum enhancement factor, determined using the measured binary period change4, ranges between 2.2 and 4.9, depending on the assumptions about the mass and density of Dimorphos5. Here we report observations from the LUKE and LEIA instruments on the LICIACube cube satellite, which was deployed 15 days in advance of the impact of DART. Data were taken from 71 seconds before the impact until 320 seconds afterwards. The ejecta plume was a cone with an aperture angle of 140 ± 4degrees. The inner region of the plume was blue, becoming redder with increasing distance from Dimorphos. The ejecta plume exhibited a complex and inhomogeneous structure, characterized by filaments, dust grains and single or clustered boulders. The ejecta velocities ranged from a few tens ofmetres per second to about 500 metres per second.

Selection of shaped charges parameters for producing aluminum particles with velocities in the range of 2.5–16 km/s

Testing rocket and space technology objects in ground conditions for resistance to the impact of meteoroids and fragments of space debris can be carried out using shaped charges. To substantiate the design parameters of shaped charges that ensure the formation of aluminum particles in a wide velocity range (from 2.5 to 16 km/s), numerical modeling of the formation process was carried out within the framework of a two-dimensional axisymmetric problem of continuum mechanics using three different computing codes to increase the reliability of the results. The calculations consider shaped charges with a diameter of 20–100 mm with aluminum liners of various shapes. It is shown that the formation of particles with velocities close to the lower limit of the considered range is ensured by gently sloping segmental liners of degressive thickness. To form higher-velocity particles with velocities over 5 km/s, it is proposed to use combined liners, the jet-forming part of which has the shape of a hemisphere of constant thickness or the shape of a semi-ellipsoid or semi-superellipsoid of rotation of degressive thickness.

Flextegrity arched structures for Lunar bases built from indigenous materials

Flextegrity is a broad structural concept, represented here by a chain of perforated massive segments in dry contact, coupled by a passing-through pre-tensioned tie-rod (tendon). Contact surfaces realize pure rolling along tailor-designed pitch lines, so that the relative rotation of adjacent segments determines the tendon elongation: the bending constitutive law can be optimized simply by re-shaping the contact surfaces. Flextegrity arches are placed side by side to form a vault, pressurized via an interposed air-tight membrane. The arch follows an almost complete circle (the vault approaches a tube), to minimize the actions on the foundations from internal pressure. The structure also supports a thick radiation shield above, made up of loose Lunar debris. The main characteristic is that the massive segments can be made from cast Lunar regolith, fused into solar-powered devices, whose weight is mitigated by the reduced Lunar gravity. Huge savings on mission budget are expected, because the only components from Earth are the tendons, made of high-performance lightweight carbon nanotube fibers, and the air-tight membrane. Small-scale prototypes are manufactured from cast concrete. The structural response is analyzed through a theoretical model. The concept is applied to a Moon base example, verifying compatibility with the strength of Lunar regolith under various actions, including meteoroid impact.

Structure of the Martian Crust Below InSight From Surface Waves and Body Waves Generated by Nearby Meteoroid Impacts

AbstractWe measure group velocity dispersion of surface waves generated by two meteoroid impacts on Mars close to the lander of the InSight mission. This allows us to probe the crustal structure in the first few kilometers beneath the InSight lander. In combination with body wave arrival times from five impact events, we obtain direct seismic constraints on the seismic velocity of the crust in the vicinity of the InSight landing site. We confirm the existence of a uppermost low‐velocity layer with a mean thickness of ∼1.2 km, interpreted as layered volcanic materials, possibly interstratified with sedimentary and altered materials. Our joint inversion of surface and body waves shows a four‐layer model for the Martian crust, compatible with high‐ and low‐frequency P‐to‐S receiver functions estimated in previous studies.

Lunar ejecta origin of near-Earth asteroid Kamo’oalewa is compatible with rare orbital pathways

Near-Earth asteroid, Kamo’oalewa (469219), is one of a small number of known quasi-satellites of Earth; it transitions between quasi-satellite and horseshoe orbital states on centennial timescales, maintaining this dynamics over megayears. The similarity of its reflectance spectrum to lunar silicates and its Earth-like orbit both suggest that it originated from the lunar surface. Here we carry out numerical simulations of the dynamical evolution of particles launched from different locations on the lunar surface with a range of ejection velocities in order to assess the hypothesis that Kamo‘oalewa originated as a debris-fragment from a meteoroidal impact with the lunar surface. As these ejecta escape the Earth-Moon environment, they face a dynamical barrier for entry into Earth’s co-orbital space. However, a small fraction of launch conditions yields outcomes that are compatible with Kamo‘oalewa’s orbit. The most favored conditions are launch velocities slightly above the escape velocity from the trailing lunar hemisphere.

Hidden morphology of Shackleton Crater, lunar South Pole

The article's goal is the detailed description of geomorphologic structures on the floor and interior walls of Shackleton Crater and a reconstruction of their formation histories.A Digital Elevation Model (DEM) with 20 m grid was constructed for the area around the crater based on Lunar Orbiter Laser Altimeter (LOLA) data. The DEM was analysed for slope steepness, Maximal Catchment Area (MCA) and four curvatures: maximal (kmax), minimal (kmin), horizontal (kh) and vertical (kv). Using this extensive set of Morphometric Variables (MVs) for the first time for a detail lunar DEM revealed unknown structures in permanently shaded areas.The previously identified large elevated structures “A" and “C" are attributed to landslides. “A" is related to a relatively large meteoroid impact that produced a recognisable crater on the exterior slope of Shackleton. “C" is associated with a landslide scar affecting the rim of Shackleton Crater directly above it. Structure “B” is not related to landsliding, but without of additional high-resolution geophysical data, its origin remains unclear.The low number of small impact craters on the steep slopes and sediment fields indicates ongoing surface erosion due to migration of unconsolidated fine grains and their deposition downslope. The foot slope zone is characterised by multiple accumulations of debris flows in the form of thin strips, identified as local landforms with kh > 0. On the surface of elevated structures “A”, “B” and “C” the map of kh reveals tree-like structures – erosion forms previously unknown in lunar geomorphology. These structures are formed by branching spurs characterised by several orders. The spurs are located relatively perpendicularly to the altitude isolines.The thickest (up to 120 m) slope deposits form a relatively flat area between the elevated structure “B" and the crater wall. These deposits should be of the greatest interest for future investigations searching for buried volatiles mixed with slope deposits.

Global Mapping of Fragmented Rocks on the Moon with a Neural Network: Implications for the Failure Mode of Rocks on Airless Surfaces

Failure modes of lunar boulders depend both on rheology and the erosion agents acting in the lunar surface environment. Here, we address the failure modes of lunar boulders and their variations at a quasi-global scale (60°N to S). We deploy a neural network and map a total of ∼130,000 fragmented boulders (width > ∼10 m) scattered across the lunar surface and visually identify a dozen different disintegration morphologies corresponding to different failure modes. Our findings suggest that before a boulder is catastrophically shattered by an impact, there is an internal weakening period with minor morphological evidence of damage at the rock scale at the resolution of the used imagery. We find that some of the rare pre-shattering morphologies (e.g., fractures) are equivalent to morphologies observed on asteroid Bennu, suggesting that these morphologies on the Moon and on asteroids are likely not diagnostic of their formation mechanism (e.g., meteoroid impact, thermal stresses). In addition, we identify new morphologies such as breccia boulders with an advection-like erosion style. We publicly release the produced fractured boulder catalog along with this paper.

Large mass inflow rates in Saturn’s rings due to ballistic transport and mass loading

The Cassini mission provided key measurements needed to determine the absolute age of Saturn’s rings, including the extrinsic micrometeoroid flux at Saturn, the volume fraction of non-icy pollutants in the rings, and the total ring mass. These three factors constrain the ring age to be no more than a few 100 Myr (Kempf et al., 2022). Observations during the Cassini Grand Finale also showed that the rings are losing mass to the planet at a prodigious rate. Some of the mass flux falls as “ring rain” at high latitudes. However, the influx in ring rain is considerably less than the total measured mass influx of 4800 to 45000 kg s−1 at lower latitudes (Waite et al., 2018).In addition to polluting the rings, micrometeoroid impacts lead to ballistic transport, the mass and angular momentum transport due to net exchanges of meteoroid impact ejecta. Because the ejecta are predominantly prograde, they carry net angular momentum outward. As a result, ring material drifts inward toward the planet. Here, for the first time, we use a simple model to quantify this radial mass inflow rate for dense rings and find that, for plausible choices of parameters, ballistic transport and mass loading by meteoroids can produce a total inward flux of material in the inner B ring and in the C ring that is on the order of a few ⋅103 to a few ⋅104 kg s−1, in agreement with measurements during the Cassini Grand Finale. From these mass inflow rates, we estimate that the remaining ring lifetime is ∼ 15 to 400 Myr. Combining this with a revised pollution age of ∼ 120 Myr, we conclude that Saturn’s rings are not only young but ephemeral and probably started their evolution on a similar timescale to their pollution age with an initial mass of one to a few Mimas masses.In addition to showing that meteoroid impacts can produce a large sustained mass inflow through the B and C rings, this paper addresses various uncertainties and considers possible contributions by additional transport mechanisms and by external torques. We also map out a set of future research projects, including global simulations.

Latitudinal and radial dependence of the lunar sodium exospheric temperature and linewidths

A latitudinal and radial study of the lunar sodium exosphere has been performed utilizing observations made from two different methods: (1) observations made at targeted altitudes using a Fabry-Perot Spectrometer (FPS) and (2) observations made from a coronagraph. The FPS observations made from the National Solar Observatory McMath-Pierce Solar Telescope, Kitt Peak, Arizona and the coronagraph observations were made at the Winer Observatory, Sonoita, Arizona. A small subset of the high resolution FPS observations were made concurrently with coronagraph measurements. Measured linewidths and linewidth-derived temperatures from FPS observations were compared to temperatures derived from the coronagraphic intensity altitude profiles, with FPS linewidth-derived temperatures shown to be consistently lower. We suggest that the coronagraph method samples a velocity distribution perpendicular to the FPS's LOS, while the FPS samples a velocity distribution tangential to the lunar limb (i.e., along the FPS LOS). We also suggest that the coronagraph measurements may be more sensitive to the escaping population of atoms as the population close to the surface is not observed. The concurrent FPS measurements sit below the occulting disk of the coronagraph and measure the atoms closer to the surface. Furthermore, both the FPS linewidth-derived temperatures and the coronagraph scale heights show an increase towards high latitudes, an effect which is attributed to particle transport and/or contributions from a source like meteoroid impact vaporization. FPS linewidths decrease as a function of altitude, a result confirmed through a simulation of velocity distributions from nonthermal source mechanisms. And, finally, Linewidths are largest when looking over the dawn/dusk terminator. These results will enable improved characterization of the sources for the lunar sodium exosphere.

Численный анализ взрывного формирования алюминиевых частиц в диапазоне скоростей 2…16 км/c

Explosive gun launchers are used to test rocket and space systems for their resistance to the impact of meteoroids and fragments of space debris. This work applies numerical simulation within the framework of the two-dimensional axisymmetric problem of continuum mechanics and substantiates design parameters of the shaped charges that form compact aluminum particles weighing up to 1 g and more in a wide range of speeds (from 2 km/s to 16 km/s). Simulation was carried out in relation to the shaped charges of different diameters (from 20 mm to 100 mm) using the ANSYS/AUTODYN, ERUDIT and KOLDUN computer systems. It is shown that charges of larger diameter are required to form faster particles identical in mass. Besides, it is necessary to use segmental cumulative liners of digressive thickness to form particles approaching the lower boundary of the indicated speed range. Wherein, to form faster particles moving at the speeds from 10 km/s to 16 km/s, it is necessary to implement the combined shaped charge liners, where the jet-forming part is shaped as a semi-ellipsoid or a semi-superellipsoid of rotation of the digressive thickness.

Оценка траектории метеороидов по марсианским кластерам

Recently, about 1200 fresh meteoroid impact sites were discovered on Mars, they are single craters and crater fields with crater sizes up to 50 m. Atmosphere density on the surface of Mars corresponds to about 30 km height of the Earth's atmosphere. Thus, scattering fields of craters on Mars allow one to study fragmentation details, which are hidden in terrestrial conditions. Previously, data on 77 Martian clusters were analyzed. To estimate the trajectory of meteoroids, the scattering ellipses were constructed. The ellipse size determines the angle of the meteoroid entry into the atmosphere and provides information about the height of destruction and the density of a space object. For more than 70% of clusters, the obtained azimuth estimations are within 20° of those determined by independent evaluations. For some clusters, the flight direction can be specified from crater ejecta on Martian HiRISE images. Estimations of azimuth angles for 42 clusters coincide with previous results obtained for 70% of clusters, while the data on the flight direction fit only for 30%. The discrepancy between different estimations of azimuth angles requires the use of other approaches. Continuing on the topic, this work presents numerical modeling of the flight and fragmentation of a meteoroid in the atmospheres of two planets, Mars and Earth. It is assumed that the simulation results will allow one to determine meteoroid parameters, in particular, the trajectory parameters. The main purpose of the presented work is to demonstrate the efficiency of the fragmentation model, its applicability to Martian clusters, and the difference in the scattering fields on the Earth and Mars: the atmospheric sorting effect is weak on Mars, and the scattering field is mainly dependent on fragmentation and the lateral spreading of fragments. The area of the simulated cluster is described with an accuracy of about 10%; the size of the maximum crater, with an accuracy of about 35%. The ratios of crater diameters to the maximum crater diameter for the model and real cluster are close to each other. In the future, it is planned to implement a series of numerical simulations with different initial data and to compare the results with real clusters on Mars, which have already been analyzed in previous works. The aim is to propose the advanced methods for determining the direction of the flight of meteoroids and the properties of impactors such as density and strength.

Martian buildings: structural forms using in-place sources

On Mars, structural loads and the low tensile strength of in-place Martian binders make existing solutions for Martian structures uneconomical because they are based on the terrestrial sources like inflatable units. Here we address this issue by introducing and analyzing three innovative structural forms in accordance with the structural engineering point of view using symmetric optimum parabolic rotated arch shapes and in-place waterless sulfur-based concrete. These forms minimize the tensile stresses under Martian structural loads. Probable Martian structural loads, including gravity, wind, marsquakes, asteroid and meteoroid impact loads and their effects have been investigated and calculated. The proposed models were analyzed under Martian structural loads using the implicit finite element method and the results were compared to two concrete structural forms from previous studies. The proposed models could tolerate Martian structural loads with complete elastic behavior and would significantly decrease the Martian colonization cost due to using Martian resources and reduce element importing from Earth.

Martian Buildings: Design loading

Multiplanetary life has been studied by scientists as a way to supply energy or sustain human life in the future. Mars is likely to be man’s first destination, colonization using onsite structural construction would be one of the main options. The first step to designing a reliable building is to know the applied structural loads and to have an accurate design load combination. Due to lack of complete knowledge, short span of recorded data, Martian environment, and hazardous environment that Martian structures face, constructed Martian structures should behave appropriately under the highest likely live, dead and environmental loads either simultaneously or as a worst-case scenario. The present study evaluated and calculated probable Martian structural loads, including live, internal pressure, snow, gravity (dead), dust accumulation, thermal stress, wind, marsquake, asteroid, and meteoroid impact loads and their effects. Information was gathered from previous studies and valid data from Martian landers, rovers and orbiters. Wind loads were calculated based on the over 6.5 years of data recorded by Vikings 1 and 2, temperature and winds for InSight (TWINS) sensor. A wind shear exponent and wind profile have been proposed for a Martian flat terrain construction site. Marsquake lateral loads, frequency content and seismicity were assessed using data from the seismic experiment for interior structure (SEIS) and the Viking 2 seismometer. Considering the high influx of micrometeoroids, their penetration distance, impact loads and their effects on structures were calculated. The annual probability of an asteroid impact on a settlement was assessed for a 30-year mission. A load map for Martian residential buildings that considers the worst-case scenario in which a Martian structure should be designed based on them has been proposed.

Performance of Lunar Regolith Shield under Meteoroid Impact: Uncertainties of a Numerical Prediction

The protection of the future lunar base from radiation, thermal stresses and impacts of meteoroids can be achieved by several options, generally consisting in a shielding system, made of either regolith or combined materials. In the present paper, the incidence of two sources of uncertainty on the FEM calculation of stress propagation through the covering regolith layer has been assessed. First, the investigation has pointed out, for a given impact and a given constitutive model, the uncertainty in the stress prediction related to the strain interval adopted for the soil stiffness measurement. Thereafter, calculation has been performed, for a given stiffness value, changing the assumed collision duration of one order of magnitude for equal impact momentum, that is, changing the maximum impact force too, correspondingly. The simulation has been performed based on physical and mechanical parameters of DNA-1A lunar simulant. The results provide indication of the relative importance of the calculation assumptions, which could address the design of a regolith shield.

Ejection velocities, age, and formation process of SPE meteoroid cluster

Context. Meteoroid clusters represent a unique opportunity to study processes of meteoroid disruptions in interplanetary space. We follow our previous work about the September epsilon Perseid (SPE) meteoroid cluster from 2016 with a detailed analysis of the observed data and cluster formation conditions. Aims. Our goal is to determine ejection velocities of the cluster members and SPE’s age, as well as to estimate the most probable formation process. Methods. We precisely determined mutual positions and masses of all meteoroids including the errors. We assumed that the massdominated meteoroid is the parent body of the cluster and that the observed positions of meteoroids are controlled by the ejection velocities and the action of solar radiation pressure. A formula for the dependence of meteoroid ejection velocities on the mutual positions, masses, and cluster age was derived. It was assumed that the time at which the initial kinetic energy of all meteoroids reached a minimum value corresponds to the age of the cluster. Knowing values and directions of ejection velocities together with meteoroid masses then allowed us to determine the most likely process of cluster formation. Results. The meteoroids occupy a volume of 66 × 67 × 50 km and are shifted in the antisolar direction by 27 km relative to the parent meteoroid. The age of the cluster is 2.28 ± 0.44 days. The ejection velocities range from 0.13 ± 0.05 m s−1 to 0.77 ± 0.34 m s−1 with a mean value of 0.35 m s−1. The ejection velocity directions are inside the cone with an apex angle of 101 ± 5°. The axis of the cone is ~45° away from the solar direction and ~34° away from the mean direction of the flux of small meteoroids’ incident on the parent meteoroid. Formation due to the separation of part of the surface due to very fast rotation is the least likely thing to occur. We estimate the rotation frequency to be about 2 Hz and the corresponding stress is several orders of magnitude lower than the predicted strength limit. It is also difficult to explain the formation of the cluster by an impact of a small meteoroid on the parent body. However, this possibility, although not very likely, cannot be completely ruled out. The most probable process is the exfoliation due to thermal stresses. Their estimated magnitude is sufficient and the derived ejection velocities are consistent with this process of formation.