Chelyabinsk Meteorite Research Articles

Atmospheric entry and strewn fields estimation for rubble-pile meteoroids

One of the potentially catastrophic risks to human survival is the impact of a meteorite on Earth. When a meteoroid enters the atmosphere at an ultra-high speed, a series of complex evolution processes occur, mainly including ablation, fragmentation, airburst, and ground impact. This paper proposes a new systematic dynamical method for simulating the entire process of a meteoroid entering the atmosphere. In the new method, the DEM (Discrete Element Method) model is utilized to describe the initial structure and shape of a rubble-pile meteoroid. A combination of an aerodynamic trajectory model, a thermal ablation model, and an airburst model is introduced to simulate the entry process. Particularly, the Jone-Wilkins-Lee state equation is employed to characterize the large-scale airburst phenomenon caused by the internal expansion of the meteoroid. Referring to the observational data of the Chelyabinsk meteorite event, this paper parametrically simulates the trajectories, ablation, fragmentation, and airburst, and predicts the strewn field of different-shaped meteoroids. Compared with existing debris cloud models, this method considers the shape effect of rubble-pile meteoroids and can obtain the strewn field as a side effect. Numerical validation is carried out, indicating the result of the new method is more in line with the actual scenarios.

Thermal metamorphism of metal assemblage in the light lithology of the Chelyabinsk LL5 meteorite

Research subject. Metal assemblage in the light lithology of the Chelyabinsk ordinary chondrite (LL5). Aim. The study of the structure of kamacite (α-Fe(Ni, Co)) and taenite (γ-Fe(Ni, Co)), as well as identification of the morphological features resulting from heating of chondrite matter. Materials and methods. Samples from the unaltered light lithology of the Chelyabinsk meteorite. The chemical composition of the samples was studied using optical microscopy (Zeiss Axiovert 40 MAT) and scanning electron microscopy (FE-SEM ∑IGMA VP) with an EDS unit. Results. The studied fragments can be divided into three groups depending on their structural composition: 1) metal grains with an unchanged structure; a zonal structure is observed in taenite (tetrataenite, cloudy zone); 2) metal grains with a taenite structure similar to the zonal one; 3) fragments in which no grains with a zonal structure were found; martensite-like structures formed during reheating were present. The structure of metal assemblage in the Chelyabinsk chondrite is compared with the structure of metal assemblage obtained in previous experiments with the Seymchan iron meteorite. It was established that heating to a temperature of 400°C for 6 h causes no changes in the metal grain structure. Heating to temperatures of 500 and 600°C for 6 h initiates transformation processes of the cloudy zone, which disappears completely after heated to 700°C for 6 h. Conclusions. Fragments of the light lithology of the Chelyabinsk ordinary chondrite were heating unevenly as a result of an impact event in its cosmic history. The presence of tetrataenite and a cloudy zone in one of the fragments means that temperature in this area didn’t exceed 400°C. Some areas underwent heating in the temperature range of 500–600°C and above 700°C.

Актуализация ОБРАЗОВ И стереотипов ОБЫДЕННОГО и профессионального СОЗНАНИЯ в устных рассказах о челябинском метеорите

The article is devoted to the analysis of images and stereotypes of everyday and professional consciousness represented in oral stories about the Chelyabinsk meteorite. The stories include various linguistic means for describing and considering the unique phenomenon that occurred on the morning of February 15, 2013. For the first time in the world history a large space body (in scientific terms an asteroid, meteoroid or bolide) flew and exploded over an industrialized and densely populated region, causing considerable destruction. The article views the stories of people who witnessed the event. Some of these stories were recorded in different years and stored in the folklore archive of the South Ural State Humanitarian and Pedagogical University, others were published in the popular science book “Chelyabinsk Superbolide” and the newspaper of Chelyabinsk State University “University Embankment.” The authors of the article consider that the stories reflect the subjective image of the objective world, largely due to the experience of people. The basis for the storytellers’ describing and interpreting what they saw and experienced includes either ordinary images and stereotypes (fire, car headlights, fireworks, building noise), or images and stereotypes characteristic of professional consciousness (shock wave, inversion trail, welding arc radiation, etc.) A certain part of the oral stories about the Chelyabinsk meteorite demonstrates the transition from the use of images and stereotypes of everyday consciousness to understanding the event in line with the folklore tradition. The analysis proved that a person’s cognitive activity relies on existing knowledge schemes, on the one hand, and is focused on the conceptual system of a particular individual, on the other hand.

Emission spectroscopy at high frame rates during ablation tests of meteorite samples in plasma wind tunnel

Optical emission spectra between 522–580 nm of ablating meteorites have been recorded at frame rates as high as 1 kHz for the first time during ground testing with simultaneous spatial and temporal resolution. A novel high frame rate emission spectroscopy arrangement has been developed and employed to diagnose the ablating meteorites in several experimental campaigns. In addition to the identification of species from emission lines detected, the resulting high-speed spectral data were used to study the temporal and spatial evolution of melting droplets and the associated spectral signatures. The time history of radiance from the atomic species emission was used to interpret the fragmentation behavior of various meteorites. Chelyabinsk meteorite exhibit almost constant radiance over time indicating steady droplet detachment whereas Ragland meteorite shows infrequent radiance peaks corresponding to random fragmentation/droplet detachment of varying sizes. A gradual rise in radiance history from iron meteorite Mount Joy shows that it takes finite time for melting and accumulation of droplets.

Shock-induced potassium and zinc isotope fractionation in ordinary chondrites and its implications

To constrain how impacts influence the behavior of moderately volatile elements (MVEs), we report potassium (K) and zinc (Zn) contents and isotopic compositions of shock melt pockets (SMPs) and unmelted parts of three heavily shocked ordinary chondrites and bulk rocks of Chelyabinsk meteorite. All SMPs are enriched in K content and have lower isotopic values (δ41K = −1.99‰, −1.22‰ and −1.40‰) while the adjacent unmelted parts are enriched in heavy K isotopes (δ41K = −0.41‰, −0.01‰ and 0.04‰) compared to the bulk rocks of Chelyabinsk meteorite (δ41K = −0.77‰ and −0.73‰). By contrast, Zn is depleted in SMPs and the isotopic compositions are heavier (δ66Zn = −0.19‰, 2.42‰, 1.74‰) in SMPs than that in unmelted parts (δ66Zn = −0.65‰, 1.76‰, −0.97‰). Our results indicate a decoupling between the two MVEs that Zn is lost from shock melts while K is dramatically enriched in shock melts during impacts. The isotope fractionation of Zn is probably caused by evaporation of shock melts, while K isotope fractionation is most likely caused by solid-melt diffusion which is controlled by its incompatibility. The isotopic decoupling of K from Zn during major impacts further enhances our understanding of high temperature elemental and isotopic behavior of MVEs and may shed new light on the variously heterogeneous distribution of MVEs in solar system.

Comparison of two different infrared spectral analysis based evaluation of impact induced shock events of the Chelyabinsk meteorite

Shock metamorphic processes in minerals were observed in the recently fallen Chelyabinsk meteorite and compared with two infrared laboratory methods: DRIFT and ATR based spectral analysis types, attached to a Fourier Transformational Infrared Spectrometer (FTIR). Both of ATR and DRIFT methods have advantages and disadvantages for shock stage identification. However, while the ATR method has wide literature background, the DRIFT method was not used in shock metamorphic research yet, hence this study links ATR spectra with DRIFT spectra to obtain reference for such IR methods in the analysis of shock metamorphism. The results show that shock-based spectral changes could be better followed by the decreasing number of peaks with DRIFT than with ATR data; while the situation is opposite for FWHM values, which better characterizes the shock consequences from ATR data. The DRIFT analyses made from bulk meteorite material. Hence more mineral phases were identified than by separate measurements of ATR. The ATR spectra includes rather major vibration, But with DRIFT the minor bands could be also measured. Hence the other shock indicator, the disappearance of minor bands with increasing shock stage could be better followed by DRIFT. The important shock metamorphic indicator, the FWHM could be identified rather from ATR spectra, as the DRIFT spectra includes small sized peaks, and the FWHM values are near to the spectral resolution of DRIFT spectra. Both of ATR and DRIFT methods show shift of IR bands to higher wavenumber with increasing shock stage. Moreover, the DRIFT method shows the split of some minor bands in case of feldspar and pyroxene due to dimerization of silicate structure.With increasing shock stage one band disappeared and a new one appeared in case of feldspar DRIFT data, while feldspar did not emerge using ATR observations. In case of olivine the major bands shifted by +2… +5 cm−1 using DRIFT and ATR spectra also. In case of pyroxene one band disappeared and new forbidden bands emerged. These results provide starting points to develop shock estimation using DRIFT method too, what is a much more available at various laboratories. However, it is worth mentioning that DRIFT method usually identifies more mineral phases than ATR because of the difference in spatial resolution.

Meteoritic materials within sulfate aerosol particles in the troposphere are detected with transmission electron microscopy

When meteorites impact the Earth’s atmosphere, they fractionalize and ablate, generating aerosol particles containing extraplanetary materials. Meteoritic materials have been identified among aerosol particles using elemental markers (iron and magnesium); however, their shapes and mixing states are largely unknown. Here we demonstrate the presence of meteoritic materials collected by a research aircraft from the troposphere over the western Pacific using transmission electron microscopy. The distribution of meteoritic elements within individual particles coincided with sulfur, indicating that they were in forms of sulfates, i.e., water-soluble. Enhanced number fractions of sulfate particles with meteoritic materials were observed during tropopause-folding events, suggesting that they originated from the stratosphere. We also estimated the potential contributions of the Chelyabinsk meteorite event, which occurred 5 months prior to the sampling and represents the largest meteorite event in the past century. This study provides unique observational evidence for the linkage between extraplanetary materials and tropospheric aerosols.

The Elemental and Texture Analysis of the Chelyabinsk Meteorite Fragment by Non-Destructive Neutron Methods

The Elemental and Texture Analysis of the Chelyabinsk Meteorite Fragment by Non-Destructive Neutron Methods

Ancient and recent collisions revealed by phosphate minerals in the Chelyabinsk meteorite

The collision history of asteroids is an important archive of inner Solar System evolution. Evidence for these collisions is brought to Earth by meteorites. However, as meteorites often preserve numerous impact-reset mineral ages, interpretation of their collision histories is controversial. Here, we combine analysis of phosphate U-Pb ages and microtextures to interpret the collision history of Chelyabinsk—a highly shocked meteorite. We show that phosphate U-Pb ages correlate with phosphate microtextural state. Pristine phosphate domain U-Pb compositions are generally concordant, whereas fracture-damaged domains universally display discordance. Combining both populations best constrains upper (4473 ± 11 Ma) and lower intercept (−9 ± 55 Ma, i.e., within error of present) U-Pb ages. All phosphate U-Pb ages were completely reset during an ancient high energy collision, whilst fracture-damaged domains experienced further Pb-loss during mild and recent collisional re-heating. Targeting textural sub-populations of phosphate grains permits more robust reconstruction of asteroidal collision histories.

Elemental composition of the Chelyabinsk meteorite determined by neutron activation analysis

Elemental composition of the Chelyabinsk meteorite determined by neutron activation analysis

Correlating whole sample EDS and Raman mappings – A case study of a Chelyabinsk meteorite fragment

Whole sample microscopy mappings are of interest in many cases as they provide analytical information of phases varying in size by orders of magnitude and in composition across the sample. These benefits are amplified if more than one microscopic technique is used for the mappings. However, to take full advantage of correlative whole sample mappings, the data of each technique has to be carefully prepared, treated, correlated and evaluated. With this work, we want to present the key steps of our data treatment approach as well as the results on an exemplary sample, the Chelyabinsk meteorite.The most important step in our data treatment approach is to start by evaluating the spectral maps separately as far as possible (at-% quantification for EDS for example) and then generate pseudo spectral maps from this evaluation in the form of image stacks. This allows us to preserve the advantages of specialized software packages and standard work flows for every spectral mapping, whilst also unifying the data format and compressing the data sufficiently for correlation and the application of machine learning tools.We have performed whole sample mappings using SEM, EDS and Raman on a cross-section of a Chelyabinsk meteorite fragment, roughly 1.0cm × 0.8cm large. Combining these mappings into a single “super” spectral map, we were able to produce a uniquely detailed mapping of the composition of the meteorite fragment, as well as perform a quantitative analysis of the elemental composition of several crystallographic phases. The results of our compositional analysis; olivine (Fo72Fa28), pyroxene (≈ 97 % En80Fs20Wo0 and 3 % En56Fs6Wo38), feldspar (albite), troilite, FeNi (taenite and kamacite), merrillite, chromite and hydroxyapatite; agree qualitatively with other reports from literature.

On the Mass Distribution of Fragments of an Asteroid Disrupted in the Earth’s Atmosphere

To model the interaction with the atmosphere of fragments of a disrupted asteroid, which move independently of each other, it is necessary to know their mass distribution. In this regard, an analogy is drawn with fragmentation in high-speed impact experiments performed to simulate the disruption of asteroids at their collisions in outer space. Based on the results of impact experiments and assuming a power law for the mass distribution in a differential form, we obtained the cumulative number of fragments as a function of the fragment mass m normalized to the total mass of fragments, the mass fraction of the largest fragment(s), the number of the largest fragments, and the power index. The formula for the cumulative number of fragments of a disrupted body is used to describe the results of impact experiments for different fragmentation types. The proposed fragment mass distribution is also tested by comparison with the mass distributions of recovered meteorites in the cases of Mbale, Bassikounou, Almahata Sitta, Košice, and Chelyabinsk meteorite falls.

The Mechanical Properties of Chelyabinsk LL5 Chondrite Under Compression and Tension

The mechanical properties of Chelyabinsk LL5 chondrite (Chelyabinsk meteorite) were studied by uniaxial compression and diametral compression/indirect tension test. Twenty cylindrical samples, 10 for compression and 10 for tension, with the diameter 3.3 mm and 1.65 mm in height have been prepared for testing. It was shown that the strength of the tested samples under compression almost 45 times greater than it is at tension: 372 ± 10 MPa and 8.2 ± 0.7 MPa, respectively. Fracture behaviour under compression and tension was similar and can be characterised as brittle. The obtained compression strength of the Chelyabinsk meteorite lies close to the maximal values of strength for many other chondrites, whereas its tensile strength magnitude resides in the bottom quarter of the range of similar measurements. It may be caused by the small sizes of the investigated samples together with a large number of tiny cracks between the grains in the Chelyabinsk chondrite. Our estimations have shown that if one assumes that the initial shape of the Chelyabinsk fireball was spherical or ellipsoidal, then its fragmentation stress is close to the experimental tensile strength and much lower than the compression strength. Hence, a stress state equivalent to one appearing at the indirect tension test could occur in the Chelyabinsk fireball during its fall in the Earth atmosphere.

Post-impact metamorphism of the Chelyabinsk meteorite in shock experiment

The vast majority of the studied samples of the Chelyabinsk LL5 meteorite shower is represented by the light, dark and impact melt lithologies. Their regular relative positions were revealed in the sections of the large fragments of the Chelyabinsk meteorite. Thus, the zones of light lithology are surrounded by the zones of dark lithology and they both are located within the impact melt. In the present study, we compare the breccia texture of large samples with the lithology zones formed after shock experiment. It was shown that during the spherical shock experiment performed using the light lithology material of the Chelyabinsk meteorite, the gradient of P-T conditions was realized so that dark lithology, mixed lithology, and impact melt were formed within one shock experiment. In the present study, we focus on structural changes associated with metal and troilite. The formation mechanism of the breccia texture in the large fragments of the Chelyabinsk meteoroid was proposed.

Analysis of Ionospheric Disturbances Caused by the 2018 Bering Sea Meteor Explosion Based on GPS Observations.

The Bering Sea meteor explosion that occurred on 18 December 2018 provides a good opportunity to study the ionospheric disturbances caused by meteor explosions. Total electron content (TEC) is the core parameter of ionospheric analysis. TEC and its changes can be accurately estimated based on the Global Positioning System (GPS). TID is detected in time and frequency domain based on power spectrum and Butterworth filtering method. By analyzing the waveform, period, wavelength, propagation speed and space-time distribution of TID, the location of the TID source is determined, and the process of TID formation and propagation is understood. The TID caused by meteor explosions has significant anisotropy characteristic. Two types of TID were found. For the first type, the average horizontal propagation velocity is 250.22 ± 5.98 m/s, the wavelength is ~135–240 km, the average period is about 12 min, and the propagation distance is less than 1400 km. About 8 min after the meteor explosion, the first type of TID source formed and propagated radially at the velocity of 250.22 ± 5.98 m/s. For the second type, the propagation velocity is ~434.02 m/s. According to the waveform, period, wavelength and propagation velocity of the TID, it is diagnosed to be the midscale traveling ionospheric disturbances (MSTID). Based on the characteristics of TID, we infer that the TID is excited by the gravity waves generated by the meteor explosion, which is in accordance with the propagation law of gravity waves in the ionosphere. And it is estimated that the average velocity of the up-going gravity waves is about 464.58 m/s. A simple model was established to explain the formation and the propagation of this TID, and to verify the characteristics of the TID propagation caused by nuclear explosion, earthquake, tsunami, and Chelyabinsk meteorite blast. It is estimated that the position of the TID source is consistent with the meteor explosion point, which further indicates that the TID is caused by the meteor explosion and propagates radially.

Study of the Chelyabinsk Meteorite Magnetism by Nuclear Gamma-Resonance Spectroscopy

Three fragments of the Chelyabinsk meteorite have been investigated by Mossbauer spectroscopy in a temperature range of 300–830 K. They are found to contain iron in the composition of various minerals in different physicochemical and crystallographic states. Anomalous behavior of the temperature dependences of hyperfine magnetic fields on iron nuclei in all fragments is demonstrated. The results obtained are qualitatively explained within the concept of structural magnetic phase transitions, in which iron ions play a role of stabilization centers for new crystal structures in specific temperature ranges.

Survey, defence and resource development of NEO

A near-Earth object (NEO) is any small Solar system body whose orbit brings it to proximity with Earth. Currently, more than 20000 NEOs are detected, most of which have diameters less than 1 km. The study of NEOs is significant to understand the solar system. NEOs formed in the very early stage of solar system according to isotope dating, and remain most original material in proto-planetary disk. Thus, the study of NEOs can reveal the components of early solar system. Besides, NEOs are also important to explain the formation of Earth-Moon systems in giant impact hypothesis, i.e., a mar-size asteroid hit Earth 4.5 billion years ago and the fragments around Earth formed Moon via gravitational accretion. Furthermore, survey of NEOs is also important for human beings, because of the potentially hazardous objects (PHOs), which lead to the Cretaceous-Paleogene (K-Pg) extinction event, as well as the Tunguska event. Fortunately, we have lots of NEO survey programs, e.g., Catalina Sky Survey, Near-Earth Asteroid Tracking, Pan-STARRS, Zwicky Transient Facility in ground, and Near-Earth Object WISE in space with near infrared telescope, etc. These projects provide a nearly completed catalog for NEOs with diameter>1 km. We can determine the orbits of these NEOs via the astrometric time series data. However, lots of smaller NEOs with diameter <140 m are still missing, due to the detection limits of faint objects using current survey telescopes. These missing small NEOs can also lead to local destruction on Earth, e.g., the Chelyabinsk meteorite in 2013. More survey programs with larger telescopes, e.g., LSST, will be helpful to generate a more completed catalog of small NEOs and to recognize more small PHOs. After knowing the threat of PHOs, human beings need defense plans to avoid the impact or minimize the influence on human being. Although a big asteroid impact event would occur in a very low possibility, we need to take precaution. However, we do not have any feasible and effective plan to avoid the asteroid impact currently. Either nuclear explosive plan or drag the asteroid away using spacecraft engines can hardly work, Because of the huge mass (>millions tons) of the asteroid. Besides, the big fragments of the asteroid after explosion may lead to more impacts on Earth and make conditions worse. Better forethought plans need experts in astronomy, geology, life science, climatology etc., to discuss together. The NEOs may be harmful if it impacts Earth. However, the resources on asteroid, e.g., water, metal can be utilized by human beings. Utilizing the resources in space is the only way to break through the limits of Earth’s resources, and extend the footprint of human being further in space. Currently, some companies are set up and aim to mine on asteroids, e.g., the Planetary Resources Company and the Deep Space Industries. Chinese people also set up a company named Origin Space to study the plan in this field. Although, there is a long way to go, including lots of crucial techniques need to be studied, the success of development of the resources on asteroid would bring our technique and civilization in a new era.

Investigation of the Meteorite “Chelyabinsk” by Means of the Positron Annihilation Lifetime and Transmission Mössbauer Spectroscopies

Bulk of the main part of the Chelyabinsk meteorite (ordinary chondrite, LL5) for the presence of nanometer pores therein is investigated by means of the positron annihilation lifetime spectroscopy (PALS). In addition, its phase composition is studied with a help of the transmission Mossbauer spectroscopy (TMS). These results are refined by means of the powder X-ray diffraction (XRD). The obtained data demonstrate an absence of the nanometer pores in the meteorite. TMS data show that the meteorite consists of mineral phases (olivine and pyroxene), which are rather typical for the ordinary chondrites. Iron is present in sulfide and nickel forms. Possible applications of nuclear-physics methods for analysis of an origin of meteorites and evolution of the Solar system are discussed.

УРАЛ

The article shows the monitoring results of the Ural region seismic network in 2013. It describes the seismic stations and registration abilities of the network. The analysis of seismic activity in Ural in 2013 and infor-mation about changes of the regional seismic regime since 2006 are given. The seismicity in the Ural is unique as it is presented by a wide spectrum of natural earthquakes (tectonic, earthquakes due to collapse, impact) as well as induced earthquakes (explosions, rock falls, rockbursts). Whereby the number of explosions in the region predominates among other seismic events, the number of rockbursts is much more than tectonic earth-quakes. A structural ordering can be seen for tectonic earthquakes. They tend to the basic geologic structure of the region to the Main Ural Fault. The induced events tend to mining regions. Also, there is a weak scat-tered seismicity that is typical for platform territories. Acting since 1999 the regional seismic network pro-vides the representative registration on the magnitude level ML≥2.5. In general in 2013 in Ural it was regis-tered 173 seismic events, and their basic seismic parameters were determined. The common number of in-dustrial explosions was 173. The summarized seismic explosions energy was 3.99E+9 Joules. The number of rockbursts was 29; their seismic energy was 2.82E+9 Joules. The five tectonic earthquakes made the min-imal contribution to the seismicity of the region. The unique event registered by seismic network was the ex-plosion of Chelyabinsk meteorite, and its parameters are shown in the article. Parameters of all mentioned above seismic events are presented in catalogue. The strongest events with ML≥3.0 including Chelyabinsk meteorite explosion, are considered separately, including their seismograms and parameters provided by other international seismic centers. The article shows the map with the actual locations of regional seismic stations and event epicenters in 2013. Generally the seismic regime of the region in 2013 was quite calm; the summarized seismic explosions energy was low. The trend to the seismic activity decay continues since 2010. The location of the natural and induced seismic events in space confirms the active zones previously determined.

A structural insight into the Chelyabinsk meteorite: neutron diffraction, tomography and Raman spectroscopy study

The internal structural organization and phase composition of a fragment of the Chelyabinsk meteorite have been studied using neutron diffraction, tomography methods, optical microscopy, and Raman spectroscopy. The bulk mineral composition of the meteorite and spatial distribution of different components were determined. In addition to previously found phases of olivine, orthopyroxene, plagioclase and troilite, the obtained data of optical microscopy and neutron diffraction provide evidence of the presence of kamacite phase in the studied meteorite fragment. The heterogeneous distribution of the iron in the olivine and orthopyroxene phases was observed, the morphological calculations were used to analyze the spatial arrangement of metal components.