Meteorite Fragments Research Articles

Meteorite Chelyabinsk: Features of Destruction

A space object exploded near the city of Chelyabinsk on February 15, 2013. Meteorite fragments reached the Earth’s surface, and accordingly we may consider this space object to have been a meteorite. However, this event showed a number of features not corresponding to the destruction of a meteorite. The space object began to disintegrate at an altitude of 70 km when pressure (dynamical loads) on its front surface was ~6.7 × 103 N·m-2. The substance from the object’s surface was not blown off by drops, as at ablation, but was dumped by jets over a distance up to 1 km. The trail of this space object visually reminded us of a jet aircraft’s contrail, made up of water. But there is no enough water at altitudes of 30 - 70 km. It may be assumed that the object itself delivered water to these altitudes. The calculation of gas rise over the trail showed that the temperature in some parts of this trail was about 900 K. Heating of large masses of gas can be explained not only by the release of kinetic energy of the space object, but also by combustion processes of its substance. Thus, it was concluded that the meteorite could have been delivered by a comet.

The Chelyabinsk meteorite: New insights from a comprehensive electron microscopy and Raman spectroscopy study with evidence for graphite in olivine of ordinary chondrites

AbstractWe present results of petrographic, mineralogical, and chemical investigations of three Chelyabinsk meteorite fragments. Three distinct lithologies were identified: light S3 LL5, dark S4–S5 LL5 material, and opaque fine‐grained former impact melt. Olivine–spinel thermometry revealed an equilibration temperature of 703 ± 23 °C for the light lithology. All plagioclase seems to be secondary, showing neither shock‐induced fractures nor sulfide‐metal veinlets. Feldspathic glass can be observed showing features of extensive melting and, in the dark lithology, as maskelynite, lacking melt features and retaining grain boundaries of former plagioclase. Olivine of the dark lithology shows planar deformation features. Impact melt is dominated by Mg‐rich olivine and resembles whole‐rock melt. Melt veins (<2 mm) are connected to narrower veinlets. Melt vein textures are similar to pegmatite textures showing chilled margins, a zone of inward‐grown elongated crystals and central vugs, suggesting crystallization from supercooled melt. Sulfide‐metal droplets indicate liquid immiscibility of both silicate and sulfide as well as sulfide and metal melts. Impact melting may have been an important factor for differentiation of primitive planetary bodies. Graphite associated with micrometer‐sized melt inclusions in primary olivine was detected by Raman mapping. Carbon isotopic studies of graphite could be applied to test a possible presolar origin.

Phase equilibria in the nominally Al65Cu23Fe12 system at 3, 5 and 21 GPa: Implications for the quasicrystal-bearing Khatyrka meteorite

Two of the three natural quasiperiodic crystals found in the Khatyrka meteorite show a composition within the Al-Cu-Fe system. Icosahedrite, with formula Al63Cu24Fe13, coexists with the new Al62Cu31Fe7 quasicrystal plus additional Al-metallic minerals such as stolperite (AlCu), kryachkoite [(Al,Cu)6(Fe,Cu)], hollisterite (AlFe3), khatyrkite (Al2Cu) and cupalite (AlCu), associated to high-pressure phases like ringwoodite/ahrensite, coesite, and stishovite. These high-pressure minerals represent the evidence that most of the Khatyrka meteoritic fragments formed at least at 5GPa and 1200°C, if not at more extreme conditions. On the other hand, experimental studies on phase equilibria within the representative Al-Cu-Fe system appear mostly limited to ambient pressure conditions, yet. This makes the interpretation of the coexisting mineral phases in the meteoritic sample quite difficult.We performed experiments at 3, 5 and 21GPa and temperatures of 800–1500°C using the multi-anvil apparatus to investigate the phase equilibria in the Al65Cu23Fe12 system representative of the first natural quasicrystal, icosahedrite. Our results, supported by single-crystal X-ray diffraction and analyses by scanning electron microscopy, confirm the stability of icosahedrite at high pressure and temperature along with additional coexisting Al-bearing phases representative of khatyrkite and stolperite as those found in the natural meteorite. One reversal experiment performed at 5GPa and 1200°C shows the formation of the icosahedral quasicrystal from a pure Al, Cu and Fe mixture, a first experimental synthesis of icosahedrite under those conditions. Pressure appears to not play a major role in the distribution of Al, Cu and Fe between the coexisting phases, icosahedrite in particular. Results from this study extend our knowledge on the stability of icosahedral AlCuFe at higher temperature and pressure than previously examined, and provide a new constraint on the stability of icosahedrite.

A low-background [formula omitted]-coincidence spectrometer for radioisotope studies

The performance of a new, low-background NaI(Tl) spectrometer, based on γγ-coincidence counting, is discussed. We present experimental coincidence efficiencies, timing resolutions, background count rates, and minimum detectable activities. The spectrometer has been simulated using Geant4, and the results are used for estimating coincidence efficiencies for volume sources. To test the device, we measured the cosmogenic 26Al activity in a small (17.7 g) meteorite fragment. We find a value of 52.9±7.8dpm∕kg, in agreement with the activity measured previously in a much larger fragment of the same meteorite using a HPGe detector.

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Cover: The largest fragment (1.32 kg) found within the Stubenberg meteorite strewn field. The meteorite fell on March 6, 2016, near Stubenberg (Bavaria, Germany). Six meteorite fragments, totaling 1473 g, were recovered so far. Details of the meteorite and the fall circumstances are discussed by Bischoff et al. in their article on pp. 1683–1703. Image courtesy of Rico Mettler.

A chondrite strewn field was found in east of Lop Nor, Xinjiang

The meteorites are the most important extraterrestrial samples for understanding the formation and the evolution history of the solar system, although ~382 kg lunar samples and ~1500 asteroid mineral grains have been returned by human space exploration activities. The Northwest region of China, especially the Xinjiang, has a vast area of sandy deserts and Gobi Deserts. The lower annual rainfall and the dry climate of this region provide a good condition for meteorite preservation. In recent years, the number of recovered meteorites from the Gobi Deserts in Xinjiang increased significantly. The Sanfengshan area, located about 65 km east of Lop Nor, is one of the research regions. We first collected three ordinary chondrites in Sanfengshan area on October 9, 2013. Then, we carried out 11 meteorite search campaigns in this area. More than 130 meteorite fragments with a total mass over 160 kg have been recovered. The map of all collected Sanfengshan meteorites depicts a clearly 3 km×11 km elliptic strewn field. The sizes are sorted in the SE-NW-oriented ellipsoid of the strewn field, therefore indicating that the meteor entered the atmosphere from SE at a low angle relative to the ground. In this study, six meteorites (Tuya 002–007) from the Sanfengshan field have been measured using a Scios-FIB field emission scanning electron microscope (SEM), a JXA 8230 electron microprobe analysis (EMA), and a self-made noble gas mass spectrometer. Among all of the collected meteorites, Tuya 002 is the only one unusual sample, which doesn’t show any fusion crust on its surface. We inferred that Tuya 002 is not paired with the other collected meteorites. The well-defined chondrule boundaries and heavy weathering grade, i.e. W3 (the occurrence of large amounts of calcium sulfate in Tuya 002 indicates that it suffered a heavy terrestrial weathering) also support the conclusion that Tuya 002 is obviously different from the other meteorites collected in the Sanfengshan area. In addition to Tuya 002, all the meteorites collected in this region most likely originate from one single meteoric shower. These meteorites all belong to the L5 ordinary chondrite group, with a moderate shock stage of S2 and a heavy weathering grade of W3. The cosmic ray exposure age of Tuya 003 (the representative meteorite of the Sanfenghshan meteoric shower) is 45.6±4.4 Ma. This indicates that the meteoroid that produced the Sanfengshan meteoric shower could be produced in the 45 Ma break-up event on L chondrite parent body. On the other hand, petrographic observations and noble gas measurements shown that Tuya 002 belongs to the L4 ordinary chondrite group. A rather lower CRE age relative to the Sanfengshan L5 chondrites of 17.0±4.1 Ma has been calculated. This also indicates that Tuya 002 is not paired with other L5 meteorites collected in the same strewn field. Our studies shown that the meteorites collected in Sanfengshan area consist of more than one meteorite fall. It includes the main L5 meteorite fall (produced the Sanfengshan L5 strewn field) and the L4 meteorite fall (represented by Tuya 002). This indicates that the Sanfengshan area is not a meteorite dense area. In recent years, several meteorite dense areas (e.g., Loulan Yizhi, Lop Nur, Argan, and Xingdi) have been gradually reported. The limited meteorite types found in such reported meteorite dense areas indicates that these regions are maybe not the real meteorite dense areas, but probably represents the meteorites strewn field. Therefore, it is necessary, in the future, to carry out detailed petrology, mineralogy, cosmic ray exposure age as well as terrestrial age measurements to identify the meteorite dense area in/around the Xinjiang.

On the occurrence and origin of anthropogenic radionuclides found in a fragment of the Chelyabinsk (LL5) meteorite

A piece of the 2013 Chelyabinsk meteorite was investigated for its content of anthropogenic radionuclides. In addition to traces of cesium-137 that had been previously reported for this particular fragment, we found an unusually high amount of strontium-90, which indicates that the source of this contamination was the Kyshtym accident (1957). A high Sr-90/Cs-137 activity ratio is characteristic for Kyshtym-derived contaminations. Based on the cesium-137 content in the soil from the finding site, it is estimated that the fragment was contaminated with soil particles in the milligram range upon impact. Investigation of the soil revealed very unusual ferromagnetic characteristics and an iron-rich chemical composition. Mössbauer spectroscopy indicated the presence of steel components in this soil, suggesting that the investigated meteorite fragment was found in an industrial dumping site rather than natural soil.

Experimental Simulation of Meteorite Ablation during Earth Entry Using a Plasma Wind Tunnel

Abstract Three different types of rocks were tested in a high enthalpy air plasma flow. Two terrestrial rocks, basalt and argillite, and an ordinary chondrite, with a 10 mm diameter cylindrical shape were tested in order to observe decomposition, potential fragmentation, and spectral signature. The goal was to simulate meteoroid ablation to interpret meteor observation and compare these observations with ground based measurements. The test flow with a local mass-specific enthalpy of 70 MJ kg−1 results in a surface heat flux at the meteorite fragment surface of approximately 16 MW m−2. The stagnation pressure is 24 hPa, which corresponds to a flight condition in the upper atmosphere around 80 km assuming an entry velocity of 10 km s−1. Five different diagnostic methods were applied simultaneously to characterize the meteorite fragmentation and destruction in the ground test: short exposure photography, regular video, high-speed imaging with 10 kHz frame rate, thermography, and Echelle emission spectroscopy. This is the first time that comprehensive testing of various meteorite fragments under the same flow condition was conducted. The data sets indeed show typical meteorite ablation behavior. The cylindrically shaped fragments melt and evaporate within about 4 s. The spectral data allow the identification of the material from the spectra which is of particular importance for future spectroscopic meteor observations. For the tested ordinary chondrite sample a comparison to an observed meteor spectra shows good agreement. The present data show that this testing methodology reproduces the ablation phenomena of meteoritic material alongside the corresponding spectral signatures.

Remnants of altered meteorite in the Cretaceous‐Paleogene clay boundary in Poland

AbstractFossil iron meteorites are extremely rare in the geological sedimentary record. The paleometeorite described here is the first such finding at the Cretaceous‐Paleogene (K‐Pg) boundary. In the boundary clay from the outcrop at the Lechówka quarry (Poland), fragments of the paleometeorite were found in the bottom part of the host layer. The fragments of meteorite (2–6 mm in size) and meteoritic dust are metallic‐gray in color and have a total weight of 1.8181 g. Geochemical and petrographic analyses of the meteorite from Lechówka reveal the presence of Ni‐rich minerals with a total Ni amount of 2–3 wt%. The identified minerals are taenite, kamacite, schreibersite, Ni‐rich magnetite, and Ni‐rich goethite. No relicts of silicates or chromites were found. The investigated paleometeorite apparently represents an independent fall and does not seem to be derived from the K‐Pg impactor. The high degree of weathering did not permit the chemical classification of the meteorite fragments. However, the recognized mineral inventory, lack of silicates, and their pseudomorphs and texture may indicate that the meteorite remains were an iron meteorite.

Asteroid Origins Satellite (AOSAT) I: An On-orbit Centrifuge Science Laboratory

Exploration of asteroids, comets and small moons (small bodies) can answer fundamental questions relating to the formation of the solar system, the availability of resources, and the nature of impact hazards. Near-earth asteroids and the small moons of Mars are potential targets of human exploration. But as illustrated by recent missions, small body surface exploration remains challenging, expensive, and fraught with risk. Despite their small size, they are among the most extreme planetary environments, with low and irregular gravity, loosely bound regolith, extreme temperature variation, and the presence of electrically charged dust. Here we describe the Asteroid Origins Satellite (AOSAT-I), an on-orbit, 3U CubeSat centrifuge using a sandwich-sized bed of crushed meteorite fragments to replicate asteroid surface conditions. Demonstration of this CubeSat will provide a low-cost pathway to physical asteroid model validation, shed light on the origin and geophysics of asteroids, and constrain the design of future landers, rovers, resource extractors, and human missions. AOSAT-I will conduct scientific experiments within its payload chamber while operating in two distinct modes: (1) as a nonrotating microgravity laboratory to investigate primary accretion, and (2) as a rotating centrifuge producing artificial milligravity to simulate surface conditions on asteroids, comets and small moons. AOSAT-I takes advantage of low-cost, off-the-shelf components, modular design, and the rapid assembly and instrumentation of the CubeSat standard, to answer fundamental questions in planetary science and reduce cost and risk of future exploration.

Smashing bits to show asteroid strength

Planetary Science![Figure][1] Optical image showing chondrules in a meteorite fragment. PHOTO: YVES MARROCCHI How strong is an asteroid? Earth rocks are poor analogs because of differences in composition, gravity during formation, and geologic processing. Cotto-Figueroa et al. tested samples from two large meteorites (pieces of asteroid that have fallen to Earth) by crushing them in a vice to measure the bulk material properties. By comparing cubes of different sizes, they extrapolated the strength of meter-sized asteroids, finding values that are consistent with the observed break-up of meteors as they enter Earth's atmosphere. The results will be useful for planning sample return or asteroid mining missions or for deflecting potentially hazardous asteroids away from Earth. Icarus 277 , 73 (2016). [1]: pending:yes

The Agoudal (High Atlas Mountains, Morocco) shatter cone conundrum: A recent meteorite fall onto the remnant of an impact site

AbstractAssociations between impact structures and meteorite occurrences are rare and restricted to very young structures. Meteorite fragments are often disrupted in the atmosphere, and in most cases, meteorite falls that have been decelerated by atmospheric drag do not form a crater. Furthermore, meteorites are rapidly weathered. In this context, the finding of shatter cones in Jurassic marly limestone in the same location as a recent (105 ± 40 ka) iron meteorite fall near the village of Agoudal (High Atlas Mountains, Morocco) is enigmatic. The shatter cones are the only piece of evidence of a meteorite impact in the area. The overlap of a meteorite strewn field with the area of occurrence of shatter cones led previous researchers to consider that the meteorite fall was responsible for the formation of shatter cones in the context of formation of one or several small (<100 m) impact craters that had since been eroded. Shatter cones are generally not reported in association with subkilometer‐diameter impact craters. Here, we present new field observations and an analysis of the distribution and characteristics of shatter cones, breccia, and meteorites in the Agoudal area. Evidence for local deformation not related to the structural High Atlas tectonics has been observed, such as a vertical to overturned stratum trending N150‐N160. New outcrops with exposures of shatter cones are reported and extend the previously known area of occurrence. The area of in situ shatter cones (~0.15 km2) and the strewn field of meteorites are distinct, although they show some overlap. The alleged impact breccia is revealed as calcrete formations. No evidence for a genetic relationship between the shatter cones and the meteorites can be inferred from field observations. The extent of the area where in situ shatter cones and macrodeformation not corresponding to Atlas tectonic deformation are observed suggest that the original diameter of an impact structure could have been between at least 1–3 km. For typical erosion rates in the Atlas region (~0.08 cm yr−1), the period of time required for the erosion of such a structure (1.25–3.75 Ma) is much larger than the age of the meteorite fall. This line of reasoning excludes a genetic link between the shatter cones and the meteorite fall and indicates that the observed shatter cones belong to an ancient impact structure that has been almost entirely eroded.

Estimation of the initial shape of meteoroids based on statistical distributions of fragment masses

An approach to the estimation of the initial shape of a meteoroid based on the statistical distributions of masses of its recovered fragments is presented. The fragment distribution function is used to determine the corresponding scaling index of the power law with exponential cutoff. The scaling index is related empirically to the shape parameter of a fragmenting body by a quadratic equation, and the shape parameter is expressed through the proportions of the initial object. This technique is used to study a representative set of fragments of the Bassikounou meteorite and compare the obtained data with the results of statistical analysis of other meteorites.

The Chelyabinsk Meteorite as a multiple source of acoustic and seismic waves

Shock waves and impact of the Chelyabinsk Meteorite fragments on the ground initiated various waves in the atmosphere and the earth. Three different sources of seismic and infrasound waves were found by arrival time and azimuth of seismic and infrasound waves recorded by the International Monitoring System.

Impact Craters in South America, by Acevedo R. D., Rocca M. C. L., Ponce J. F., and Stinco S. G. Heidelberg: Springer, 2015. 104 p. SpringerBriefs in Earth Sciences: South America and the Southern Hemisphere. ISBN 978-3-319-13092-7.

Impact Craters in South America, by Acevedo R. D., Rocca M. C. L., Ponce J. F., and Stinco S. G. Heidelberg: Springer, 2015. 104 p. SpringerBriefs in Earth Sciences: South America and the Southern Hemisphere. ISBN 978-3-319-13092-7.

Mossbauer Investigation of the Chelyabinsk Meteorite Fragment

The article devoted to study of the fragments of Chelyabinsk meteorite with the help of Mossbauer spectroscopy. It is shown that the iron in various fragments of the meteorite exist in different crystallographic, physical and chemical conditions. A new phenomenon of sharp increasing effective magnetic field in the region of the iron nuclei in the temperature range of 553-573 К and jumps of the main parameters of Mossbauer spectra at other temperatures are observed. According to the data of the isomer shifts and quadruple splitting of the individual spectra, iron ions have a valence of Fe2+ − 3d6, Fe3+ − 3d5, Fe4+ − 3d4, Fe6+ − 3d2 and also intermediate between them. A qualitative explanation of the experimental data is proposed.

Search the Hard Magnetic Tetrataenite Phase in the Fragments of Chelyabinsk Meteorite

Few Fe-Ni particles with composition close 50:50 were found by EDX and SEM investigations in the fragment of Chelyabinsk meteorite. These inclusions were extracted and magnetic domains were observed with the help of sol-gel method. No hard magnetic particles with tetragonal L10 crystal structure (tetrataenite) were detected.

Mössbauer parameters of ordinary chondrites influenced by the fit accuracy of the troilite component: an example of Chelyabinsk LL5 meteorite

The influence of the fit accuracy of the troilite component in the Mossbauer spectra of ordinary chondrites on the parameters obtained for other spectral components was evaluated using the Mossbauer spectrum of Chelyabinsk LL5 meteorite fragment with light lithology as a typical example. It was shown that with respect to the application of a usual sextet component where quadrupole interaction is taken into account in the first-order perturbation limit, substantial improvement of the spectrum fit can be achieved either by using the full Hamiltonian description of the troilite component or by its formal approximation with the superposition of three symmetric doublet components. Parameter values obtained for the main spectral components related to olivine and pyroxene were not sensitive to the fit of troilite component while parameters of the minor spectral components depended on the way of troilite component fitting.

Study of Chelyabinsk LL5 meteorite fragments with different lithology using Mössbauer spectroscopy with a high velocity resolution

Study of four Chelyabinsk LL5 ordinary chondrite fragments with different lithology was carried out using optical and scanning electron microscopy, X-ray diffraction and 57Fe Mossbauer spectroscopy with a high velocity resolution at 295 K. Components revealed from the Mossbauer spectra were related to the main iron-bearing crystals of minerals such as olivine, pyroxene, troilite, kamacite, taenite and chromite. However, the relative amount of these minerals appeared to be different in the studied fragments.

High-sensitivity HPGe gamma-spectrometry analysis of radionuclides in Martian meteorites

Analysis of cosmogenic radionuclides in Martian meteorites is a great radioanalytical challenge because of the high scientific value of these meteorites, and necessity to apply non-destructive methods of analysis, e.g., low-level gamma-ray spectrometry. The measured 54Mn, 22Na, and 26Al levels in two fragments of the Tissint meteorite, a recent fall (18 July 2011), were 0.9, 1.1 and 0.6 Bq/kg in average. The high 22Na/26Al activity ratio (1.89 ± 0.05) measured in the larger sample (908.7 g) indicates an unsaturated production of 26Al in the Tissint meteorite.