Meteorite Classes Research Articles

The Massalia asteroid family as the origin of ordinary L chondrites.

Studies of micrometeorites in mid-Ordovician limestones and impact craterson Earth indicate that our planet witnessed a massive infall of ordinary L chondrite material about 466 million years ago1-3 that may have been at the origin of an Ordovician ice age and major turnover in biodiversity4. The breakup of a large asteroid in the main belt is the likely cause of this massive infall. Currently, material originating from this breakup still dominates meteorite falls (>20% of all falls)5. Here we provide spectroscopic observations and dynamical evidence that the Massalia collisional family is the only plausible source of this catastrophic event and the most abundant class of meteorites falling on Earth today. This family of asteroidsis suitably located in the inner belt, at low-inclination orbits, which corresponds to the observed distribution of L-chondrite-like near-Earth objects and interplanetary dust concentrated at 1.4° (refs. 6,7).

Spectral properties of ablating meteorite samples for improved meteoroid composition diagnostics

Emission spectra and diagnostic spectral features of a diverse range of ablated meteorite samples with a known composition are presented. We aim to provide a reference spectral dataset to improve our abilities to classify meteoroid composition types from meteor spectra observations. The data were obtained by ablating meteorite samples in high-enthalpy plasma wind tunnel facilities recreating conditions characteristic of low-speed meteors. Near-UV to visible-range (320–800 nm) emission spectra of 22 diverse meteorites captured by a high-resolution Echelle spectrometer were analyzed to identify the characteristic spectral features of individual meteorite groups. The same dataset captured by a lower-resolution meteor spectrograph was applied to compare the meteorite data with meteor spectra observations. Spectral modeling revealed that the emitting meteorite plasma was characterized by temperatures of 3700–4800 K, similar to the main temperature component of meteors. The studied line intensity variations were found to trace the differences in the original meteorite composition and thus can be used to constrain the individual meteorite classes. We demonstrate that meteorite composition types, including ordinary chondrites, carbonaceous chondrites, various achondrites, stony-iron and iron meteorites, can be spectrally distinguished by measuring relative line intensities of Mg I, Fe I, Na I, Cr I, Mn I, Si I, H I, CN, Ni I, and Li I. Additionally, we confirm the effect of the incomplete evaporation of refractory elements Al, Ti, and Ca, and the presence of minor species Co I, Cu I, and V I.

Does the composition of meteoritic metal change with forging? An experimental study

AbstractThe use of meteoritic iron in the manufacture of human artifacts since the Bronze Age has been well documented, including the iron blade of Tutankhamun's dagger. Whereas the preservation of textures and mineral inclusions suggest relatively low temperature (<950°C) working of meteoritic metal used in artifacts, higher temperature working—that is, forging—could have occurred, based on studies of Bronze Age slag. The extent to which the forging of meteoritic iron might change the bulk composition, especially the trace elements used for classification of iron meteorites, is largely unknown. Using electron microbeam methods (SEM and EPMA), and trace element analysis (ICP‐MS), we analyze metal obtained at different stages during the modern forging of a set of knife blades from fragments of the Gebel Kamil meteorite, and assess the degree to which bulk element composition, mineral inclusions, and textures are modified. We find that while forging does destroy the original texture and removes mineral inclusions, it does not significantly modify the trace elements typically used in iron meteorite classification, at least for the relatively Ni‐rich composition represented by Gebel Kamil. While we acknowledge that the modern method by which the knife blades were forged from Gebel Kamil would not have occurred in the Bronze Age, our results represent an upper temperature limit relative to the inferred conditions used in ancient forging. The identification of the meteorite (if still in existence) that was used for artifacts is feasible, based on our results and current literature on ancient meteoritic artifacts.

Colin Trevor Pillinger. 9 May 1943—7 May 2014

Colin Pillinger was a larger-than-life planetary scientist with an infectious enthusiasm for science. He was a founding member of the Planetary and Space Sciences Research Institute at the Open University in Milton Keynes. He was a mass spectroscopist who applied these techniques with great success to the study of extraterrestrial rock samples from both meteorites and the Moon. He helped identify a class of meteorite found on Earth that originated from Mars. In turn, this led to leadership of the Beagle 2 Mars lander project, which was designed to take scientific instruments to Mars in order to search for evidence of past life. Against all odds, the landing on Mars was successful, but communication with the lander was never established. Colin was a brilliant innovator, both in his science and in adopting a somewhat unconventional approach to funding the ambitious Beagle 2 project. He enjoyed the fact that, even though it was possible to purchase off-the-shelf instrumentation, the truly creative aspect of his analytic method was in the details of how it was applied, for which the rule book was still being written. Throughout his career he continued to ride the wave of new developments and was always keen to push the limits. He was a brilliant communicator, always full of engaging enthusiasm.

The “Meteorite meter”: A handheld instrument for the combined measurement of magnetic susceptibility and electrical conductivity, with application to meteorite identification and classification

AbstractWe developed a simple, handheld, and user‐friendly magnetic susceptibility meter specialized for the identification of meteorites. The measurement is based on an LC resonance circuit. When provided with a rough estimate of the sample mass, the instrument displays directly the mass‐normalized magnetic susceptibility expressed in logχm (with χm in 10−9 m3 kg−1), a parameter that is widely used in the classification of meteorites. Moreover, the measurement of the impedance of the LC resonator provides a proxy of the electrical conductivity (C‐index) that can be helpful to distinguish metal‐bearing samples from magnetite‐bearing samples. This C‐index offers an additional diagnostic for the identification of meteorites. Our tests demonstrate that the precision and the accuracy of this instrument called “Meteorite meter” (MetMet) are sufficient to allow distinguishing most meteorites from most terrestrial rocks, for a minimum recommended sample mass of 5 g. The distinction of some meteorite groups is also possible, in particular the separation of the three ordinary chondrite groups. Meteorite hunters, collectors, and curators and non‐specialists, including children, can use this instrument as a guidance in the identification and classification of meteorites. This kind of instrument has an immense advantage over the widely used testing of meteorites with magnets, as it does not affect the paleomagnetic records of meteorites that are highly valuable for scientists.

Linking meteorites to their asteroid parent bodies: The capabilities of dust analyzer instruments during asteroid flybys

AbstractLinking meteorites to their asteroid parent bodies remains an outstanding issue. Space‐based dust characterization using impact ionization mass spectrometry is a proven technique for the compositional analysis of individual cosmic dust grains. Here we investigate the feasibility of determining asteroid compositions via cation mass spectrometric analyses of their dust ejecta clouds during low (7–9 km s−1) velocity spacecraft flybys. At these speeds, the dust grain mass spectra are dominated by easily ionized elements and molecular species. Using known bulk mineral volume abundances, we show that it is feasible to discriminate the common meteorite classes of carbonaceous chondrites, ordinary chondrites, and howardite–eucrite–diogenite achondrites, as well as their subtypes, relying solely on the detection of elements with ionization efficiencies of ≤700 or ≤800 kJ mol−1, applicable to low (~7 km s−1) and intermediate (~9 km s−1) flyby speed scenarios, respectively. Including the detection of water ion groups enables greater discrimination between certain meteorite types, and flyby speeds ≥10 km s−1 enhance the diagnostic capabilities of this technique still further. Although additional terrestrial calibration is required, this technique may allow more unequivocal asteroid‐meteorite connections to be determined by spacecraft flybys, emphasizing the utility of dust instruments on future asteroid missions.

A machine learning classification of meteorite spectra applied to understanding asteroids

Understanding the distribution of matter within our Solar System requires a robust methodology for evaluating the composition of small objects in the asteroid belt. Existing asteroid taxonomies have variously been based on spectral features relating to mineralogy and on classification of asteroid spectra alone. This project tests a fundamentally different approach, using machine learning algorithms to classify asteroids based on spectroscopic characteristics of existing meteorite classes. After evaluating four classification techniques built on labeled meteorite spectral data, logistic regression (LR) was determined to provide the most accurate results that distinguish eight robust groups of meteorite classes to which asteroid spectra can then be matched. The groups are rooted in mineralogical composition and directly relate meteorites to potential host bodies. A standalone LR algorithm classifies unknown asteroid spectra uniquely as one of eight specific group, allowing the distribution of compositions in the asteroid belt to be evaluated.

Hand Magnets and the Destruction of Ancient Meteorite Magnetism

AbstractMeteorites provide invaluable records of planetary formation and evolution. Studies of their paleomagnetism have constrained accretion in the protoplanetary disk, the thermal evolution and differentiation of planetesimals, and the history of planetary dynamos. Yet, the potential of these magnetic records in advancing the field of planetary science is severely hindered by a widely used technique: application of hand magnets to assist in meteorite classification. Touching a meteorite with a magnet results in near‐instantaneous destruction of its magnetic record. Here, we showcase the destructive effects of exposing meteorites to magnets through numerical modeling, a controlled remagnetization experiment on a terrestrial basalt, and a paleomagnetic study of the oldest known Martian meteorite, the Northwest Africa (NWA) 7034 pairing group. NWA 7034 is a polymict regolith breccia containing zircon crystals with crystallization ages older than 4.4 billion years. As such it contains materials that are sufficiently old to have formed during the time Mars is most likely to have had a core dynamo. Unfortunately, we found that all nine paired stones of NWA 7034 that we investigated were remagnetized by hand magnets, as has been observed for many other hot desert meteorites. We recommend that magnets not be applied to meteorites during collection and curation. Instead, a low‐field susceptibility meter is a far more sensitive and completely nondestructive tool for meteorite classification.

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.

Meteoritic noble gas constraints on the origin of terrestrial volatiles

The elemental and isotopic compositions of noble gases trapped in primitive meteorites have the potential to yield stringent constraints on the origin of matter in the solar system. The isotopic compositions of key elements like O, Ti, Ru, Mo suggest that the Earth accreted from material having similarities with two classes of meteorites, carbonaceous chondrites (CC) and non‑carbonaceous chondrites (NC), in particular enstatite chondrites (EC). In this contribution, I examine published noble gas (neon and argon) data for CI-CM as representative of CCs, and ECs as representative of NC terrestrial building blocks. Data were corrected for contributions of cosmic ray-produced isotopes in order to identify the trapped component compositions. For both CCs and ECs, corrected noble gas data indicate that high temperature objects such as chondrules were evolving in a dusty environment. The dust consisted of refractory phases including nanodiamonds, impacts-related debris, medium to low temperature phases mainly made of organics and, in the case of CC, hydrated minerals and icy grains. Remnants of such a dust are found as rims around chondrules and as a matrix between high temperature assemblages. The dust was probably the main source of volatiles on Earth.In terrestrial reservoirs, covariations of 20Ne/22Ne ratios with 36Ar/22Ne ratios are consistent with mixing between a solar-like neon component trapped in the mantle and a chondritic Ne–Ar component mainly present in the atmosphere and hydrosphere. The chondritic end-member is clearly of the CC type and excludes EC-like material as the source of atmospheric volatiles. In addition to CC-like material, the isotopic composition of heavy noble gases (Kr and Xe) in the atmosphere points to a ~ 20% contribution of cometary material akin of the composition of comet 67P/Churyumov-Gerasimenko. In contrast, comets might have contributed less than 1% terrestrial water, C and N. Solar-like neon in the terrestrial mantle might have originated from solar irradiation of free-floating dust before parent body compaction, but this would require a cleared, dust-free environment. Trapping of nebular gas into forming solids during the gas epoch of the nascent solar system appears a more promising possibility. For other mantle volatiles, the stable isotopes of H, N, Ar, Kr and Xe point to a chondritic origin. The hydrogen and nitrogen isotopic signatures of mantle rocks and minerals are consistent with an EC-like contribution whereas those of heavy noble gases are still too imprecise to conclude. Further progress in the field will require high precision analysis of noble gases (in particular, Kr and Xe) trapped in the terrestrial (and martian) mantle(s), as well as documenting the composition of the Venusian atmosphere.

Connecting asteroids and meteorites with visible and near-infrared spectroscopy

In this work we identify spectral similarities between asteroids and meteorites. Using spectral features such as absorption bands and spectral curvature, we identify spectral matches between 500 asteroid spectra and over 1,000 samples of RELAB meteorite spectra over visible plus near-infrared wavelengths (0.45–2.5μm). We reproduce and confirm many major and previously known meteorite–asteroid connections and find possible new, more rare or less-established connections. Well-established connections include: ordinary chondrites with S-complex asteroids; pristine CM carbonaceous chondrites with Ch-type asteroids and heated CMs with C-type asteroids ; HED meteorites with V-types; enstatite chondrites with Xc-type asteroids; CV meteorites with K-type asteroids; Brachinites, Pallasites and R chondrites with olivine-dominated A-type asteroids.In addition to the link between ordinary chondrite meteorites with S-complex asteroids, we find a trend from Q, Sq, S, Sr to Sv correlates with LL to H, with Q-types matching predominately to L and LL ordinary chondrites, and Sr and Sv matching predominantly with L and H ordinary chondrites. We find ordinary chondrite samples that match to the X-complex. These are measurements of slabs and many are labeled as dark or black (shocked) ordinary chondrites. We find carbonaceous chondrite samples having spectral slopes large enough to match D-type asteroid spectra.We find in many cases the asteroid type to meteorite type links are not unique, for classes with and without distinct spectral features. While there are examples of dominant matches between an asteroid class and meteorite class that are well established, there are less common but still spectrally compatible matches between many asteroid types and meteorite types. This result emphasizes the diversity of asteroid and meteorite compositions and highlights the degeneracy of classification by spectral features alone requiring additional measurements to firmly establish asteroid–meteorite links. Recent and upcoming spacecraft missions will shed light on the compositions of many of the asteroid classes, particularly those without diagnostic features, (C-, B-, X-, and D-types), with measurements of C-type Ceres, C-type Ryugu, B-type Bennu, M-type Psyche, and C-, P-, and D-types as part of the Lucy mission.

Planetesimal rings as the cause of the Solar System’s planetary architecture

Astronomical observations reveal that protoplanetary disks around young stars commonly have ring- and gap-like structures in their dust distributions. These features are associated with pressure bumps trapping dust particles at specific locations, which simulations show are ideal sites for planetesimal formation. Here we show that our Solar System may have formed from rings of planetesimals—created by pressure bumps—rather than a continuous disk. We model the gaseous disk phase assuming the existence of pressure bumps near the silicate sublimation line (at T ~ 1,400 K), water snowline (at T ~ 170 K) and CO snowline (at T ~ 30 K). Our simulations show that dust piles up at the bumps and forms up to three rings of planetesimals: a narrow ring near 1 au, a wide ring between ~3–4 au and ~10–20 au and a distant ring between ~20 au and ~45 au. We use a series of simulations to follow the evolution of the innermost ring and show how it can explain the orbital structure of the inner Solar System and provides a framework to explain the origins of isotopic signatures of Earth, Mars and different classes of meteorites. The central ring contains enough mass to explain the rapid growth of the giant planets’ cores. The outermost ring is consistent with dynamical models of Solar System evolution proposing that the early Solar System had a primordial planetesimal disk beyond the current orbit of Uranus. The planetary architecture of the Solar System and its isotopic dichotomy can be reproduced using a protoplanetary disk model structured with rings and gaps, as commonly seen in protoplanetary disks around other stars.

4M method \u2013 new application of M\xf6ssbauer spectroscopy to classification of meteorites. How it works?

4M method is a new application of Mössbauer spectroscopy to quantitative classification of ordinary chondrites. 4M derives from four words: meteorites, Mössbauer spectroscopy, multidimensional discriminant analysis, Mahalanobis distance. This method was published by us in 2019. In this paper we present application of 4M method to classification of four meteorites. Link to script with calculation needed for classification of ordinary chondrites was given.

Xenoliths in ordinary chondrites and ureilites: Implications for early solar system dynamics

AbstractForeign clasts (xenoliths) in meteoritic breccias are a serendipitous source of information about the impact environment in which their hosts formed, including impactor flux and cosmochemical types. These parameters may be related to timing and/or heliocentric distance of xenolith origin and implantation, and thus can be used to test or inform models of early solar system dynamics. We use xenoliths in ordinary chondrites (OCs) and ureilites to do this. We first conducted a petrologic and oxygen isotope study of a new, cm‐sized igneous‐textured clast in L3.7 Northwest Africa (NWA) 092, which highlighted some of the difficulties of identifying xenoliths in meteorites. Results indicate that this clast is not a xenolith but an impact melt of non‐local OC material. We add this result to a literature survey of more than 3000 OCs and find that the fraction of OCs that contain xenoliths is <<1%, and, even in these, the abundance and the diversity of xenoliths are very low. This contrasts markedly with the ureilites, ˜5% of which contain ˜1–10 vol% xenoliths from every major meteorite class, including multiple groups and petrologic types. To investigate reasons for this difference, we compare the histories of OC and ureilite parent bodies. The OC and ureilitic parent bodies accreted in the inner solar system within ˜1 AU of one another. The OC bodies accreted ˜2–3 Myr after calcium‐aluminum‐rich inclusion (CAI) formation and were heated slowly, experiencing thermal metamorphism over ˜50–60 Myr. The ureilite parent body (UPB) accreted <1 Myr after CAIs and was heated rapidly, experiencing partial melting over ˜4 Myr. Both OC parent bodies and the UPB were catastrophically disrupted and reassembled into rubble piles. For ureilites, this occurred ˜5.0–5.4 Ma after CAIs, while for OCs, it did not occur until 50–60 Myr after CAIs. Xenoliths in OC and ureilitic breccias were acquired as fragments of impactors on the rubble piles. The presence in polymict ureilites of xenoliths of all OC groups (H, L, LL) and petrologic types (3–6), and the intimate scale on which these and myriad other xenolith types are mixed, indicate that most xenoliths were acquired within a short time period around ˜50–60 Myr after CAIs when OC (likely also Rumuruti chondrite and enstatite chondrite) parent bodies were disrupted. This timing is consistent with the early instability dynamical model for a period of excitation in the asteroid belt. Outer solar system (CC) xenoliths were also acquired during this period, but were derived indirectly from C‐type bodies that had already been emplaced in orbits in the asteroid belt. The large discrepancy in xenolith abundance between ureilites and OC may be due to different physical properties of their regoliths at 50–60 Myr after CAIs. CC‐like xenoliths in OC may represent a different, more recently acquired, population than those in polymict ureilites.

Magnetic structure and exchange interactions in pyrrhotite end member minerals: hexagonal FeS and monoclinic Fe7S8

Iron mono-sulphides, or pyrrhotites, are minerals present in the Earth’s crust and mantle as well as major magnetic constituents of several classes of meteorites, thus are of interest to a wide range of disciplines including geology, geophysics, geochemistry, and material science. Despite displaying diverse magnetic properties as a result of iron vacancy ordering, the underlying exchange mechanism has not been quantified. This study presents an examination of the electronic and magnetic properties for the two pyrrhotite group end members, hexagonal FeS and monoclinic Fe7S8 (4C superstructure) by means of density functional theory coupled with a Heisenberg magnetic model. The easy magnetization axes of FeS and Fe7S8 are found to be positioned along the crystallographic c-direction and at an angle of 56° to the c-direction, respectively. The magnetic anisotropy energy in Fe7S8 is greatly increased as a consequence of the vacancy framework when compared to FeS. The main magnetic interaction, in both compounds, is found to be the isotropic exchange interaction favouring antiferromagnetic alignment between nearest-neighbouring spins. The origin of the exchange interaction is elucidated further following the Goodenough–Kanamori–Anderson rules. The antisymmetric spin exchange is found to have a minor effect in both compounds. The theoretical findings presented in this work thus help to further resolve some of the ambiguities in the magnetic features of pyrrhotites.

The Conductive Cooling of Planetesimals With Temperature‐Dependent Properties

AbstractModeling the planetary heat transport of small bodies in the early Solar System allows us to understand the geological context of meteorite samples. Conductive cooling in planetesimals is controlled by thermal conductivity, heat capacity, and density, which are functions of temperature (T). We investigate if the incorporation of the T‐dependence of thermal properties and the introduction of a nonlinear term to the heat equation could result in different interpretations of the origin of different classes of meteorites. We have developed a finite difference code to perform numerical models of a conductively cooling planetesimal with T‐dependent properties and find that including T‐dependence produces considerable differences in thermal history, and in turn the estimated timing and depth of meteorite genesis. We interrogate the effects of varying the input parameters to this model and explore the nonlinear T‐dependence of conductivity with simple linear functions. Then we apply non‐monotonic functions for conductivity, heat capacity, and density fitted to published experimental data. For a representative calculation of a 250 km radius pallasite parent body, T‐dependent properties delay the onset of core crystallization and dynamo activity by ∼40 Myr, approximately equivalent to increasing the planetary radius by 10%, and extend core crystallization by ∼3 Myr. This affects the range of planetesimal radii and core sizes for the pallasite parent body that are compatible with paleomagnetic evidence. This approach can also be used to model the T‐evolution of other differentiated minor planets and primitive meteorite parent bodies and constrain the formation of associated meteorite samples.

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.

Collisional history of Ryugu’s parent body from bright surface boulders

The asteroid (162173) Ryugu and other rubble-pile asteroids are likely re-accumulated fragments of much larger parent bodies that were disrupted by impacts. However, the collisional and orbital pathways from the original parent bodies to subkilometre rubble-pile asteroids are not yet well understood1–3. Here we use Hayabusa2 observations to show that some of the bright boulders on the dark, carbonaceous (C-type) asteroid Ryugu4 are remnants of an impactor with a different composition as well as an anomalous portion of its parent body. The bright boulders on Ryugu can be classified into two spectral groups: most are featureless and similar to Ryugu’s average spectrum4,5, while others show distinct compositional signatures consistent with ordinary chondrites—a class of meteorites that originate from anhydrous silicate-rich asteroids6. The observed anhydrous silicate-like material is likely the result of collisional mixing between Ryugu’s parent body and one or multiple anhydrous silicate-rich asteroid(s) before and during Ryugu’s formation. In addition, the bright boulders with featureless spectra and less ultraviolet upturn are consistent with thermal metamorphism of carbonaceous meteorites7,8. They might sample different thermal-metamorphosed regions, which the returned sample will allow us to verify. Hence, the bright boulders on Ryugu provide new insights into the collisional evolution and accumulation of subkilometre rubble-pile asteroids. The Hayabusa2 team has discovered two types of bright boulder on the dark, carbonaceous asteroid Ryugu. One type has a spectrum consistent with material from an anhydrous silicate-rich asteroid, likely introduced by one or more collisions in Ryugu’s past.

Secondary Ion Mass Spectrometry as an advanced tool for meteorite classification

A reliable classification of meteorites is of great importance in order to study the meteorite history. Secondary ion mass spectrometry is applied to collect a database of spectra for four meteorite classes, H chondrite, IAB iron, L chondrite, and achondrite and based on convolutional neural network to determine the meteorite class of un unknown sample. The focus of the presented analysis is on the Košice meteorite which is identified with following elements Li, B, Na, Mg, Al, Si, P, K, Ca, Ti, Cr, Mn, Fe, and Ni. Due to the high mass resolution of 7000, several isotopes of these elements are clearly identified. The Secondary ion mass spectrometry images provide also mineralogical analysis by revealing distributions of chemical composition. The minerals of albite, troilite, augite, and diopside are recognized. Using 88 reference spectra, the unknown sample is identified as the H chondrite based on calculated probability. Secondary ion mass spectrometry technique coupled with convolutional neural network proves to be the advanced tool to analyze meteorites, to classify them, and to determine a meteorite of unknown origin.

The surprising thermal properties of CM carbonaceous chondrites

AbstractMeasurements of the low‐temperature thermodynamic and physical properties of meteorites provide fundamental data for the study and understanding of asteroids and other small bodies. Of particular interest are the CM carbonaceous chondrites, which represent a class of primitive meteorites that record substantial chemical information concerning the evolution of volatile‐rich materials in the early solar system. Most CM chondrites are petrographic type 2 and contain anhydrous minerals such as olivine and pyroxene, along with abundant hydrous phyllosilicates contained in the meteorite matrix interspersed between the chondrules. Using a Quantum Design Physical Property Measurement System, we have measured the thermal conductivity, heat capacity, and thermal expansion of five CM2 carbonaceous chondrites (Murchison, Murray, Cold Bokkeveld, Northwest Africa 7309, Jbilet Winselwan) at low temperatures (5–300 K) which span the range of possible surface temperatures in the asteroid belt and outer solar system. The thermal expansion measurements show a substantial and unexpected decrease in CM2 volume as temperature increases from 210 to 240 K followed by a rapid increase in CM2 volume as temperature rises from 240 to 300 K. This transition has not been seen in anhydrous CV or CO carbonaceous chondrites. Thermal diffusivity and thermal inertia as a function of temperature are calculated from measurements of density, thermal conductivity, and heat capacity. Our thermal diffusivity results compare well with previous estimates for similar meteorites, where conductivity was derived from diffusivity measurements and modeled heat capacities; our new values are of higher precision and cover a wider range of temperatures.