Stony Meteorites Research Articles

57Fe hyperfine parameters and phase compositions in Fe-Ni-Co alloys from iron, stony-iron and stony meteorites

57Fe hyperfine parameters and phase compositions in Fe-Ni-Co alloys from iron, stony-iron and stony meteorites

Study of Iron and Stony Meteorite Ablation Based on Simulation Experiments in an Arc Heater

To observe meteorite ablation, simulation experiments were conducted on the L5 ordinary chondrite and IAB-MG iron meteorites in an arc-heated facility and three flight conditions were reproduced. To mimic the high heating rates and the significant shear stress that meteorites experience during Earth entry, the samples were machined into 9° spherical cones with a 20 mm nose radius. High-quality video, the surface temperature, a time-resolved spectrum, and infrared video were recorded. The atom species were determined via spectroscopy to analyze the ablation products. Due to the electrode erosion and dissociation of air, the atomic lines of copper, nitrogen, and oxygen were detected in all the tests. Although the copper atom is a pollutant to the flow field, the five copper lines were used to determine the flow-field temperature. The ablation rates and effective heat of ablation of both the samples were measured under different conditions. The results indicate that shear stress is the dominant factor influencing meteorite ablation. Furthermore, the diversity between stony and iron meteorites suggests that the mass loss of stony meteorites depends on the fragmentation of the main body and that of iron meteorites depends on the shearing loss of the molten layer. Then, the fusion crusts were analyzed, the microstructures of the samples were obtained, the crust thicknesses were measured, and the elemental distribution of the stony meteorites was determined via energy dispersion spectroscopy. The study results explain the differences in the ablation and recrystallization process between stony and iron meteorites.

Textural Study of Vesicles in Tagish Lake (C2-ung) Meteorite Fusion Crust: Constraints on Vesicle Formation during Their Entry into the Earth’s Atmosphere

Vesicles are characteristic structures within the outer layer of many stony meteorites’ fusion crusts. Although these features are well-developed in hydrated carbonaceous chondrites and some micrometeorites, their formation mechanism remains poorly understood. This study provides new insights into the understanding of physical vesiculation processes by presenting the results of vesicle size distribution (VSD)—i.e., a quantitative method for vesicle analysis—applied to the study of the Tagish Lake (C2-ung) meteorite fusion crust. Tagish Lake was chosen because it shows a scoriaceous texture and a significant number of vesicles (about 24,000 vesicles/mm2), thus allowing statistical analysis. Vesicles range from being spherical to irregular-shaped and from a few μm to ~70 μm (equivalent diameter) in size. Vesicle size distribution and cumulative number density analyses show a high nucleation event and a fractal distribution of the vesicle population, respectively. We suggest these features are due to disequilibrium degassing processes, which simultaneously produce continuous/accelerating vesicle nucleation and growth. Finally, possible analogies between the scoriaceous Tagish Lake fusion crust and the space-weathered “frothy layer” on the surface of Ryugu’s grains could be found in terms of vesicularity.

The Eagle Station impact site

The Eagle Station impact site is located along Eagle Creek in Carrol County, Kentucky. Pallasites (23 cm to ≤ 3 mm), a rare form of stony meteorites, occur in a late Archaic cultural period stratum with heat-altered flaked-stone artifacts, carbonized plant remains, and fire-cracked rocks. A calibrated AMS radiocarbon age of 3824 BP to 3593 BP (1875 BCE to 1644 BCE) on the pallasite-bearing stratum demonstrates that the impact event occurred during the late Holocene. The habitation site was abandoned after the impact event and the site was buried within 200 years by alluvium. The Eagle Station impact site increases our understanding of the frequency of late Holocene cosmic events and their possible influence on ancient cultures.

Low-background gamma spectrometry and neutron diffraction in the study of stony meteorites

Non-destructive characterisation of meteorites is here performed on a stony meteorite. The identification of the sample is performed by low-background γ-ray spectrometry in order to determine the presence of certain cosmogenic radionuclides, whereas a mineralogical phase quantitative analysis is carried out by Time-of-Flight Neutron Diffraction (ToF-ND) on the sample as-it-is. The protocol is then validated by applying micro-Raman Spectroscopy (μRS) and Energy Dispersive X-ray Spectroscopy (EDS). This paper is focused on γ-ray spectrometry, proving the meteoric origin of the sample, and it also presents some preliminary results of ToF-ND.

The fusion crust of the Winchcombe meteorite: A preserved record of atmospheric entry processes

AbstractFusion crusts form during the atmospheric entry heating of meteorites and preserve a record of the conditions that occurred during deceleration in the atmosphere. The fusion crust of the Winchcombe meteorite closely resembles that of other stony meteorites, and in particular CM2 chondrites, since it is dominated by olivine phenocrysts set in a glassy mesostasis with magnetite, and is highly vesicular. Dehydration cracks are unusually abundant in Winchcombe. Failure of this weak layer is an additional ablation mechanism to produce large numbers of particles during deceleration, consistent with the observation of pulses of plasma in videos of the Winchcombe fireball. Calving events might provide an observable phenomenon related to meteorites that are particularly susceptible to dehydration. Oscillatory zoning is observed within olivine phenocrysts in the fusion crust, in contrast to other meteorites, perhaps owing to temperature fluctuations resulting from calving events. Magnetite monolayers are found in the crust, and have also not been previously reported, and form discontinuous strata. These features grade into magnetite rims formed on the external surface of the crust and suggest the trapping of surface magnetite by collapse of melt. Magnetite monolayers may be a feature of meteorites that undergo significant degassing. Silicate warts with dendritic textures were observed and are suggested to be droplets ablated from another stone in the shower. They, therefore, represent the first evidence for intershower transfer of ablation materials and are consistent with the other evidence in the Winchcombe meteorite for unusually intense gas loss and ablation, despite its low entry velocity.

A new multidisciplinary non-destructive protocol for the analysis of stony meteorites: gamma spectroscopy, neutron and muon techniques supported by Raman microscopy and SEM-EDS

The physical and chemical characterisation of meteorites is of paramount importance in the study of the formation of the Solar System.

Evidence for a large late-Holocene Strewn Field in Kiowa County, Kansas, USA

The Brenham/Haviland meteor crater is just one of a plethora of impact features comprising a large (~800 ha) late-Holocene-age strewn field in Kiowa County, Kansas. More than 10,000 kg of pallasites, a rare class of stony meteorites, have been recovered from impact features and the surface of the strewn field. Six AMS radiocarbon ages demonstrate there is a 95.4% probability that the impact event occurred within a range of 1497 BCE to 419 BCE and most likely between 754 BCE and 419 BCE. The impact event is well described in Pawnee oral histories and illustrated in petroglyphs near the strewn field. The age and geographic extent of the Kiowa County, Kansas, strewn field increases our understanding of the frequency of cosmic impact events on Earth and their influence on people and culture change.

A Comparative Study on the Radiation Attenuation Properties of Iron and Stony Meteorites: A Case of Mundrabilla and NWA 7629 Meteorites

The goal of this paper is to compare and investigate the radiation attenuation properties of Mundrabilla and NWA 7629 meteorites in terms of the photon, fast neutron and charged particles. The linear attenuation coefficients of Mundrabilla are higher than those of NWA 7629. The half value layers, tenth value layers and mean free paths of NWA 7629 are greater than those of Mundrabilla. The effective atomic number, effective electron density, equivalent atomic number and effective conductivity of the Mundrabilla are nearly constant between 0.015 MeV–15 MeV. Both the exposure build-up factors and energy absorption build-up factors are maximum at 0.8 MeV for Mundrabilla and NWA 7629. The projected/ continuous-slowing-down approximation (CSDA) ranges for charged particles for NWA 7629 are higher than those of Mundrabilla. The fast neutron attenuation of Mundrabilla is better than those of NWA 7629. Consequently, it can be concluded that photon, fast neutron and charged particles attenuation capability of Mundrabilla are better than NWA 7629 due to the nickel content, higher density and higher content of iron.

A Comparative Study on the Radiation Attenuation Properties of Iron and Stony Meteorites: A Case of Mundrabilla and NWA 7629 Meteorites

The goal of this paper is to compare and investigate the radiation attenuation properties of Mundrabilla and NWA 7629 meteorites in terms of the photon, fast neutron and charged particles. The linear attenuation coefficients of Mundrabilla are higher than those of NWA 7629. The half value layers, tenth value layers and mean free paths of NWA 7629 are greater than those of Mundrabilla. The effective atomic number, effective electron density, equivalent atomic number and effective conductivity of the Mundrabilla are nearly constant between 0.015 MeV–15 MeV. Both the exposure build-up factors and energy absorption build-up factors are maximum at 0.8 MeV for Mundrabilla and NWA 7629. The projected/ continuous-slowing-down approximation (CSDA) ranges for charged particles for NWA 7629 are higher than those of Mundrabilla. The fast neutron attenuation of Mundrabilla is better than those of NWA 7629. Consequently, it can be concluded that photon, fast neutron and charged particles attenuation capability of Mundrabilla are better than NWA 7629 due to the nickel content, higher density and higher content of iron.

New Constraints on the Composition and Initial Speed of CNEOS 2014-01-08

We study the newly released light curve from the fireball of the first interstellar meteor CNEOS 2014-01-08. The measured velocity and three observed flares down to an altitude of 18.7 km imply ambient ram pressure in the range of 113–194 MPa when the meteor disintegrated. The required yield strength is ≳20 times higher than stony meteorites and ≳2 times larger than iron meteorites. The implied slowdown in the atmosphere suggests an initial speed of about 66.5 km s−1, strengthening the case for an interstellar origin of this meteor and making it an outlier relative to the velocity dispersion of local stars.

Study of Spectrally Resolved Thermoluminescence in Tsarev and Chelyabinsk Chondrites with a Versatile High-Sensitive Setup.

Thermoluminescence (TL) research provides a powerful tool for characterizing radiation-induced processes in extraterrestrial matter. One of the challenges in studying the spectral features of the natural TL of stony meteorites is its weak intensity. The present work showcases the capabilities of a high-sensitive original module for measuring the spectrally resolved TL characteristics of the Chelyabinsk and Tsarev chondrites. We have analyzed the emission spectra and glow curves of natural and induced TL over the 300–650 nm and RT–873 K ranges. A quasi-continuous distribution of traps active within the 350–650 K range was found in the silicate substructure of both meteorites under study. Based on the general order kinetic formalism and using the natural TL data, we also estimated the activation energies of EA = 0.86 and 1.08 eV for the Chelyabinsk and Tsarev chondrites, respectively.

Enstatite nodules in the harzburgites of the Southern Urals

Research subject. At two points on the northern shore of Lake Uvil’dy in the Southern Urals, two outcrops of unique rocks – nodular harzburgites – were discovered in the tectonic lenses of serpentinite melange among garnet-biotite gneisses of the Ilmenogorsko-Vishnevogorsky Сomplex. These outcrops form a body of about 9 m in thickness among amphibolized orthopyroxenites.Results. The fine-grained serpentinized enstatite-olivine matrix of the harzburgites under study contains numerous spherical formations (nodules) 2–7 cm in diameter, composed of large enstatite crystals and rare forsterite grains. The composition and structure of these spheroids are highly similar to the enstatite chondrules from stony meteorites, although differing in size (ten times larger).Conclusions. Such structures are very rare in hyperbasites and occur in slightly altered varieties. Judging by the microstructural features and relationships of the main minerals, it is concluded that these minerals were crystallized from a magmatic melt.

Sol-gel synthesis of nano-scale, end-member albite feldspar (NaAlSi3O8)

Feldspars are the most abundant minerals in the Earth’s crust, and are also important constituents of many lunar rocks and some stony meteorites. Albite (NaAlSi3O8) makes up the sodium corner of the feldspar ternary diagram (KAlSi3O8 - NaAlSi3O8 – CaAl2Si2O8) and connects the alkali-feldspar and plagioclase binary joins. Synthesis of albite, however, has long been a problem, even at high temperatures and even at high pressures when dry. In fact, most successful syntheses require the combination of high-pressure, high-temperature, and hydrothermal environments. This paper presents a sol–gel method of albite synthesis that requires hydrothermal processing followed by high-temperature recrystallization, but no high-pressure environments. This has the advantage of allowing synthesis of relatively large amounts of material and controlled elemental substitutions.

Cosmogenic 44Ti in meteorites – a divergence with 14C and 10Be data

A record of 44 Ti activity measured in 20 stony meteorites fallen during CE 1766–2001 was compared to six series of 44 Ti activity, calculated from the data on modulation parameter Φ based on cosmogenic isotopes 14 C and 10 Be. It was shown that both experimental and computed records have appreciable divergences. The secular trends of many model curves are flatter than that of the measured record and the difference in amplitude of the century-scale cycle of Gleissberg is highly significant ( p < 5.5 × 10 −4 ). Possible causes of this discrepancy are discussed. The obtained results show that at present the cosmogenic isotope data likely contain mostly qualitative information about the behavior of the cosmic ray flux in the past and not always are suited for quantitative estimations.

Amino acid abundances and compositions in iron and stony‐iron meteorites

AbstractThe organic compositions of carbonaceous chondrite meteorites have been extensively studied; however, there have been fewer reports of other meteorite classes, and almost none from iron meteorites, which contain much less carbon than carbonaceous chondrites but make up ~4% of observed meteorite falls. Here, we report the bulk amino acid content of three iron meteorites (Campo del Cielo, IAB; Canyon Diablo, IAB; and Cape York, IIIAB) and both the metal and silicate portions of a pallasite (Imilac). We developed a novel method to prepare the samples for analysis, followed by hot water extraction and analysis via liquid chromatography‐mass spectrometry. Free amino acid abundances ranging from 301 to 1216 pmol g−1 were observed in the meteorites, with the highest abundance in the silicate portion of the pallasite. Although some of the amino acid content could be attributed to terrestrial contamination, evidence suggests that some compounds are indigenous. A suite of C5 amino acids was observed with a distinct distribution favoring a straight chain (n‐pentanoic acid) structure; this straight chain dominance is suggestive of that observed in thermally altered stony meteorites. Amino acids were also observed in terrestrial iron granules that were milled and analyzed in the same way as the meteorites, although the distribution of detected amino acids was different. It is possible that similar formation mechanisms existed in both the meteorites and the terrestrial iron, or that observed amino acids resulted from reactions of precursors during sample preparation. This work suggests that iron meteorites should not be overlooked for contributions of amino acids and likely other soluble organic molecules to the early Earth. Future studies of iron–nickel meteorites and asteroids, such as Psyche, may provide further insights into their potential organic inventory.

In-situ visualisation of dynamic fracture and fragmentation of an L-type ordinary chondrite by combined synchrotron X-ray radiography and microtomography

The relationship between the dynamic mechanical properties of stony meteorites and their microstructures was investigated in-situ for an L-type ordinary chondrite using a split-Hopkinson pressure bar apparatus and ultra-high speed phase-contrast X-ray radiography at the European Synchrotron Radiation Facility (ESRF). Synchrotron X-ray microtomography (μCT) was performed both prior to and immediately following dynamic compression to correlate key structural features between the initial microstructure and recovered fragments as well as to identify the leading mechanisms for fracture and fragmentation. Real-time visualisation of damage evolution in the specimens revealed the very first cracks to be initiated at the sites of FeNi-metal nodules. These cracks propagated rapidly through the largest group of chondrules (the porphyritic olivine type chondrules) along the loading direction, which led to the formation of column-like fragments. μCT analysis of the collected fragments confirmed the dominant mode of fracture to be transgranular with a clear link between FeNi-metal nodule statistics and the size distribution of fragments, emphasising their role in mechanical failure and fragmentation process. The resulting fragmentation was used to validate the predictions of brittle fragmentation models, and found to be in good agreement with the laboratory-scale impacts. In turn, these models can help unravel the consequences of impact-induced fragmentation processes that have helped shape the solar system.

Quantitative determination of the shock stage of L6 ordinary chondrites using X-ray diffraction

Abstract The shock stages of 14 L6 ordinary chondrites are estimated using the random X-ray diffraction patterns of polished thin section samples and the in-plane rotation method. The mean lattice strains and grain size factors for olivine and orthopyroxene are determined from the analyses based on the Williamson–Hall plots, which depict the tangent Bragg angle and integral breadth β. The lattice strain in olivine, eOl, is distributed from ~0.05% to ~0.25%, while that in orthopyroxene, eOpx, is distributed from ~0.1 to ~0.4%, where we selected the isolated peaks of olivine and orthopyroxene. The olivine peaks have Miller indices of (130), (211), (222), and (322), while the orthopyroxene peaks have Miller indices of (610), (511), (421), (631), and (12.1.2). The intercept for integral breadth β0O1 and β0Opx for the Williamson–Hall plots correlates with the grain size of the constituent minerals. The grain size is proportional to the inverse of β0 since the β intercept increases with the shock stage. Introducing a new parameter, –ε/log β0 for olivine (0.04–0.16) and orthopyroxene (0.07–0.32) reveals a clear relationship between them: –εOpx/log β0Opx = –0.01+ 2.0 (–εOl/log β0O1) (R &amp;gt; 0.9). In addition, the isolated peak of plagioclase (201) systematically changes as the shock stage increases, suggesting the progress of amorphization (maskelynitization). Another parameter, (I/FWHM)Pl(201) reveals additional relationships: –εOl/log β0O1 = 0.14(±0.01) − 5.2 × 10−5 (±5.7 × 10−6) × (I/FWHM)Pl(201), and –εOpx/log β0Opx = 0.25(±0.04) − 8.9 × 10−5 (±2.6 × 10−5) × 10–5 × (I/FWHM)Pl(201). These three parameters systematically change with the shock stage, suggesting that they are suitable shock barometers. The present method is useful to evaluate the shock stage of L6 chondrites and potentially enables quantitative shock stage classification for stony meteorites.

New measurement technique for characterizing small extraterrestrial materials by X‐ray diffraction using the Gandolfi attachment

AbstractIdentification and characterization of small extraterrestrial samples, such as small Antarctic meteorites &lt;~1 cm, require the development of convenient laboratory‐based nondestructive analytical techniques using X‐ray diffraction (XRD). We explore the characterization criteria using an X‐ray diffractometer with a Gandolfi attachment using sub‐mm small fragments and powder aggregates for various kinds of stony meteorites and develop a new analytical technique. We primarily focus on olivine and pyroxene because they are the most abundant and important minerals for stony meteorite classification. A new calibration is performed to estimate the FeO content of the olivine in unequilibrated ordinary chondrites, which is useful for determining the meteorite chemical group irrespective of powder aggregate diameter but dependent on fragment grain diameter. This is because X‐ray intensity absorption is more effective for grains than for powders. Clinoenstatite (Cen) and orthoenstatite (Oen) were distinguished using the presence or absence of the isolated Oen 511 index peak. The method is also applied to other stony meteorites including carbonaceous chondrites and achondrites. The XRD results are consistent with studies based on polished sections involving textural observations by scanning microscope and chemical compositions of the constituent minerals. The new measurement technique presented here is convenient because of its use in air by the laboratory‐based X‐ray diffractometer, which makes it useful for the initial analyses of restricted extraterrestrial sample characterization.

Fe2+ partitioning between the M1 and M2 sites in silicate crystals in some stony and stony-iron meteorites studied using X-ray diffraction and Mössbauer spectroscopy

Study of the Fe2+ partitioning among the crystallographically non-equivalent M1 and M2 sites in silicate crystals such as olivine, orthopyroxene and clinopyroxene is of interest to analyze their features and thermal history. Especially, this is important for investigation of extraterrestrial silicate crystals in meteorites. We discuss the results of the study of Fe2+ partitioning among the M1 and M2 sites in silicate crystals in some stony and stony-iron meteorites based on the data obtained by means of two independent techniques: X-ray diffraction and Mössbauer spectroscopy with a high velocity resolution. It is possible to evaluate the ratios of the Fe2+ occupancies of the non-equivalent M1 and M2 sites in olivine, orthopyroxene and clinopyroxene crystals. Estimation of the Fe2+ and Mg2+ cations distribution coefficient and the temperature of equilibrium cation distribution for olivine and orthopyroxene in some stony and stony-iron meteorites is also considered. A good agreement between results obtained by means of two independent techniques is shown.