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M D Suttle - One of the best experts on this subject based on the ideXlab platform.
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isotopic and textural analysis of giant unmelted Micrometeorites identification of new material from intensely altered 16o poor water rich asteroids
Earth and Planetary Science Letters, 2020Co-Authors: Luigi Folco, M D Suttle, Zelia Dionnet, I A Franchi, J M Gibson, R C Greenwood, A Rotundi, A King, S. S. RussellAbstract:Abstract Bulk oxygen isotope data has the potential to match extraterrestrial samples to parent body sources based on distinctive δ 18 O and Δ 17 O ratios. We analysed 10 giant (>500 μm) Micrometeorites using combined micro-Computer Tomography (μCT) and O-isotope analysis to pair internal textures to inferred parent body groups. We identify three ordinary chondrite particles (L and LL groups), four from CR chondrites and the first Micrometeorite from the enstatite chondrite (EH4) group. In addition, two Micrometeorites are from hydrated carbonaceous chondrite parent bodies with 16O-poor isotopic compositions and plot above the terrestrial fractionation line. They experienced intense aqueous alteration, contain pseudomorphic chondrules and are petrographically similar to the CM1/CR1 chondrites. These Micrometeorites may be members of the newly established CY chondrites and/or derived from the enigmatic “Group 4” Micrometeorite population, previously identified by Yada et al., 2005 [GCA, 69:5789-5804], Suavet et al., 2010 [EPSL, 293:313-320] (and others). One of our 16O-poor Micrometeorite plots on the same isotopic trendline as the CO, CM and CY chondrites – “the CM mixing line” (with a slope of ∼0.7 and a δ 17 O intercept of -4.23‰), this implies a close relationship and potentially a genetic link to these hydrated chondrites. If position along the CM mixing line reflects the amount of 16O-poor (heavy) water-ice accreted onto the parent body at formation, then the CY chondrites and these 16O-poor Micrometeorites must have accreted at least as much water-ice as CM chondrites but potentially more. In addition, thermal metamorphism could have played a role in further raising the bulk O-isotope compositions through the preferential loss of isotopically light water during phyllosilicate dehydration. The study of Micrometeorites provides insights into asteroid belt diversity through the discovery of material not currently sampled by larger meteorites, perhaps as a result of atmospheric entry biases preventing the survival of large blocks of friable hydrated material.
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intense aqueous alteration on c type asteroids perspectives from giant fine grained Micrometeorites
Geochimica et Cosmochimica Acta, 2019Co-Authors: Luigi Folco, M D Suttle, Matthew J Genge, S. S. Russell, Jens Najorka, M Van GinnekenAbstract:Abstract This study explores the petrology of five giant (>400 μm) hydrated fine-grained Micrometeorites from the Transantarctic Mountain (TAM) Micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these Micrometeorites represent ∼2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of
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diagenetically altered fossil Micrometeorites suggest cosmic dust is common in the geological record
Earth and Planetary Science Letters, 2017Co-Authors: M D Suttle, Matthew J GengeAbstract:Abstract We report the discovery of fossil Micrometeorites from Late Cretaceous chalk. Seventy-six cosmic spherules were recovered from Coniacian ( 87 ± 1 Ma ) sediments of the White Chalk Supergroup. Particles vary from pristine silicate and iron-type spherules to pseudomorphic spherules consisting of either single-phase recrystallized magnetite or Fe-silicide. Pristine spherules are readily identified as Micrometeorites on the basis of their characteristic mineralogies, textures and compositions. Both magnetite and silicide spherules contain dendritic crystals and spherical morphologies, testifying to rapid crystallisation of high temperature iron-rich metallic and oxide liquids. These particles also contain spherical cavities, representing weathering and removal of metal beads and irregular cavities, representing vesicles formed by trapped gas during crystallization; both features commonly found among modern Antarctic Iron-type (I-type) cosmic spherules. On the basis of textural analysis, the magnetite and Fe-silicide spherules are shown to be I-type cosmic spherules that have experienced complete secondary replacement during diagenesis (fossilization). Our results demonstrate that Micrometeorites, preserved in sedimentary rocks, are affected by a suite of complex diagenetic processes, which can result in disparate replacement minerals, even within the same sequence of sedimentary beds. As a result, the identification of fossil Micrometeorites requires careful observation of particle textures and comparisons with modern Antarctic collections. Replaced Micrometeorites imply that geochemical signatures the extraterrestrial dust are subject to diagenetic remobilisation that limits their stratigraphic resolution. However, this study demonstrates that fossil, pseudomorphic Micrometeorites can be recognised and are likely common within the geological record.
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thermal shock fragmentation of mg silicates within scoriaceous Micrometeorites reveal hydrated asteroidal sources
Geology, 2017Co-Authors: M D Suttle, Matthew J Genge, Matthias Van GinnekenAbstract:Scoriaceous Micrometeorites are highly vesicular extraterrestrial dust particles that have experienced partial melting during atmospheric entry. We report the occurrence of clusters of anhedral relict forsterite crystals within these particles that testify to in situ fragmentation. The absence of similar clusters within unmelted Micrometeorites suggests that fragmentation occurs during atmospheric entry rather than by parent body shock reprocessing. Clusters of broken forsterite crystals are shown to form as a result of fracturing owing to thermal stress developed during entry heating and require thermal gradients of >200 K µm–1 in order for differential thermal expansion to exceed the critical shear strength of olivine. Thermal gradients of this magnitude significantly exceed those resulting from thermal conduction and require the endothermic decomposition of phyllosilicates. Fragmented relict forsterite within scoriaceous Micrometeorites, therefore, indicate that the precursor grains were similar to CI and CM2 chondrites and retained phyllosilicate prior to atmospheric entry and thus were not dehydrated on the parent asteroid by shock or thermal metamorphism. Explosive fragmentation of hydrous asteroids during collisions, therefore, does not significantly bias the interplanetary dust population.
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Shock Fabrics in Fine-Grained Micrometeorites
Meteoritics & Planetary Science, 2017Co-Authors: M D Suttle, Matthew J Genge, Sara S. RussellAbstract:The orientations of dehydration cracks and fracture networks in fine-grained, unmelted Micrometeorites were analyzed using rose diagrams and entropy calculations. As cracks exploit pre-existing anisotropies, analysis of their orientation provides a mechanism with which to study the subtle petrofabrics preserved within fine-grained and amorphous materials. Both uniaxial and biaxial fabrics are discovered, often with a relatively wide spread in orientations (40°–60°). Brittle deformation cataclasis and rotated olivine grains are reported from a single Micrometeorite. This paper provides the first evidence for impact-induced shock deformation in fine-grained Micrometeorites. The presence of pervasive, low-grade shock features in CM chondrites and CM-like dust, anomalously low-density measurements for C-type asteroids, and impact experiments which suggest CM chondrites are highly prone to disruption all imply that CM parent bodies are unlikely to have remained intact and instead exist as a collection of loosely aggregated rubble-pile asteroids, composed of primitive shocked clasts.
Matthew J Genge - One of the best experts on this subject based on the ideXlab platform.
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intense aqueous alteration on c type asteroids perspectives from giant fine grained Micrometeorites
Geochimica et Cosmochimica Acta, 2019Co-Authors: Luigi Folco, M D Suttle, Matthew J Genge, S. S. Russell, Jens Najorka, M Van GinnekenAbstract:Abstract This study explores the petrology of five giant (>400 μm) hydrated fine-grained Micrometeorites from the Transantarctic Mountain (TAM) Micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these Micrometeorites represent ∼2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of
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diagenetically altered fossil Micrometeorites suggest cosmic dust is common in the geological record
Earth and Planetary Science Letters, 2017Co-Authors: M D Suttle, Matthew J GengeAbstract:Abstract We report the discovery of fossil Micrometeorites from Late Cretaceous chalk. Seventy-six cosmic spherules were recovered from Coniacian ( 87 ± 1 Ma ) sediments of the White Chalk Supergroup. Particles vary from pristine silicate and iron-type spherules to pseudomorphic spherules consisting of either single-phase recrystallized magnetite or Fe-silicide. Pristine spherules are readily identified as Micrometeorites on the basis of their characteristic mineralogies, textures and compositions. Both magnetite and silicide spherules contain dendritic crystals and spherical morphologies, testifying to rapid crystallisation of high temperature iron-rich metallic and oxide liquids. These particles also contain spherical cavities, representing weathering and removal of metal beads and irregular cavities, representing vesicles formed by trapped gas during crystallization; both features commonly found among modern Antarctic Iron-type (I-type) cosmic spherules. On the basis of textural analysis, the magnetite and Fe-silicide spherules are shown to be I-type cosmic spherules that have experienced complete secondary replacement during diagenesis (fossilization). Our results demonstrate that Micrometeorites, preserved in sedimentary rocks, are affected by a suite of complex diagenetic processes, which can result in disparate replacement minerals, even within the same sequence of sedimentary beds. As a result, the identification of fossil Micrometeorites requires careful observation of particle textures and comparisons with modern Antarctic collections. Replaced Micrometeorites imply that geochemical signatures the extraterrestrial dust are subject to diagenetic remobilisation that limits their stratigraphic resolution. However, this study demonstrates that fossil, pseudomorphic Micrometeorites can be recognised and are likely common within the geological record.
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thermal shock fragmentation of mg silicates within scoriaceous Micrometeorites reveal hydrated asteroidal sources
Geology, 2017Co-Authors: M D Suttle, Matthew J Genge, Matthias Van GinnekenAbstract:Scoriaceous Micrometeorites are highly vesicular extraterrestrial dust particles that have experienced partial melting during atmospheric entry. We report the occurrence of clusters of anhedral relict forsterite crystals within these particles that testify to in situ fragmentation. The absence of similar clusters within unmelted Micrometeorites suggests that fragmentation occurs during atmospheric entry rather than by parent body shock reprocessing. Clusters of broken forsterite crystals are shown to form as a result of fracturing owing to thermal stress developed during entry heating and require thermal gradients of >200 K µm–1 in order for differential thermal expansion to exceed the critical shear strength of olivine. Thermal gradients of this magnitude significantly exceed those resulting from thermal conduction and require the endothermic decomposition of phyllosilicates. Fragmented relict forsterite within scoriaceous Micrometeorites, therefore, indicate that the precursor grains were similar to CI and CM2 chondrites and retained phyllosilicate prior to atmospheric entry and thus were not dehydrated on the parent asteroid by shock or thermal metamorphism. Explosive fragmentation of hydrous asteroids during collisions, therefore, does not significantly bias the interplanetary dust population.
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Shock Fabrics in Fine-Grained Micrometeorites
Meteoritics & Planetary Science, 2017Co-Authors: M D Suttle, Matthew J Genge, Sara S. RussellAbstract:The orientations of dehydration cracks and fracture networks in fine-grained, unmelted Micrometeorites were analyzed using rose diagrams and entropy calculations. As cracks exploit pre-existing anisotropies, analysis of their orientation provides a mechanism with which to study the subtle petrofabrics preserved within fine-grained and amorphous materials. Both uniaxial and biaxial fabrics are discovered, often with a relatively wide spread in orientations (40°–60°). Brittle deformation cataclasis and rotated olivine grains are reported from a single Micrometeorite. This paper provides the first evidence for impact-induced shock deformation in fine-grained Micrometeorites. The presence of pervasive, low-grade shock features in CM chondrites and CM-like dust, anomalously low-density measurements for C-type asteroids, and impact experiments which suggest CM chondrites are highly prone to disruption all imply that CM parent bodies are unlikely to have remained intact and instead exist as a collection of loosely aggregated rubble-pile asteroids, composed of primitive shocked clasts.
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The thermal decomposition of fine-grained Micrometeorites, observations from mid-IR spectroscopy
Geochimica et Cosmochimica Acta, 2017Co-Authors: M D Suttle, Luigi Folco, Matthew J Genge, Sara S. RussellAbstract:Abstract We analysed 44 fine-grained and scoriaceous Micrometeorites. A bulk mid-IR spectrum (8–13 μm) for each grain was collected and the entire Micrometeorite population classified into 5 spectral groups, based on the positions of their absorption bands. Corresponding carbonaceous Raman spectra, textural observations from SEM-BSE and bulk geochemical data via EMPA were collected to aid in the interpretation of mid-IR spectra. The 5 spectral groups identified correspond to progressive thermal decomposition. Unheated hydrated chondritic matrix, composed predominantly of phyllosilicates, exhibit smooth, asymmetric spectra with a peak at ∼10 μm. Thermal decomposition of sheet silicates evolves through dehydration, dehydroxylation, annealing and finally by the onset of partial melting. Both CI-like and CM-like Micrometeorites are shown to pass through the same decomposition stages and produce similar mid-IR spectra. Using known temperature thresholds for each decomposition stage it is possible to assign a peak temperature range to a given Micrometeorite. Since the temperature thresholds for decomposition reactions are defined by the phyllosilicate species and the cation composition and that these variables are markedly different between CM and CI classes, atmospheric entry should bias the dust flux to favour the survival of CI-like grains, whilst preferentially melting most CM-like dust. However, this hypothesis is inconsistent with empirical observations and instead requires that the source ratio of CI:CM dust is heavily skewed in favour of CM material. In addition, a small population of anomalous grains are identified whose carbonaceous and petrographic characteristics suggest in-space heating and dehydroxylation have occurred. These grains may therefore represent regolith Micrometeorites derived from the surface of C-type asteroids. Since the spectroscopic signatures of dehydroxylates are distinctive, i.e. characterised by a reflectance peak at 9.0–9.5 μm, and since the surfaces of C-type asteroids are expected to be heated via impact gardening, we suggest that future spectroscopic investigations should attempt to identify dehydroxylate signatures in the reflectance spectra of young carbonaceous asteroid families.
Luigi Folco - One of the best experts on this subject based on the ideXlab platform.
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isotopic and textural analysis of giant unmelted Micrometeorites identification of new material from intensely altered 16o poor water rich asteroids
Earth and Planetary Science Letters, 2020Co-Authors: Luigi Folco, M D Suttle, Zelia Dionnet, I A Franchi, J M Gibson, R C Greenwood, A Rotundi, A King, S. S. RussellAbstract:Abstract Bulk oxygen isotope data has the potential to match extraterrestrial samples to parent body sources based on distinctive δ 18 O and Δ 17 O ratios. We analysed 10 giant (>500 μm) Micrometeorites using combined micro-Computer Tomography (μCT) and O-isotope analysis to pair internal textures to inferred parent body groups. We identify three ordinary chondrite particles (L and LL groups), four from CR chondrites and the first Micrometeorite from the enstatite chondrite (EH4) group. In addition, two Micrometeorites are from hydrated carbonaceous chondrite parent bodies with 16O-poor isotopic compositions and plot above the terrestrial fractionation line. They experienced intense aqueous alteration, contain pseudomorphic chondrules and are petrographically similar to the CM1/CR1 chondrites. These Micrometeorites may be members of the newly established CY chondrites and/or derived from the enigmatic “Group 4” Micrometeorite population, previously identified by Yada et al., 2005 [GCA, 69:5789-5804], Suavet et al., 2010 [EPSL, 293:313-320] (and others). One of our 16O-poor Micrometeorite plots on the same isotopic trendline as the CO, CM and CY chondrites – “the CM mixing line” (with a slope of ∼0.7 and a δ 17 O intercept of -4.23‰), this implies a close relationship and potentially a genetic link to these hydrated chondrites. If position along the CM mixing line reflects the amount of 16O-poor (heavy) water-ice accreted onto the parent body at formation, then the CY chondrites and these 16O-poor Micrometeorites must have accreted at least as much water-ice as CM chondrites but potentially more. In addition, thermal metamorphism could have played a role in further raising the bulk O-isotope compositions through the preferential loss of isotopically light water during phyllosilicate dehydration. The study of Micrometeorites provides insights into asteroid belt diversity through the discovery of material not currently sampled by larger meteorites, perhaps as a result of atmospheric entry biases preventing the survival of large blocks of friable hydrated material.
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intense aqueous alteration on c type asteroids perspectives from giant fine grained Micrometeorites
Geochimica et Cosmochimica Acta, 2019Co-Authors: Luigi Folco, M D Suttle, Matthew J Genge, S. S. Russell, Jens Najorka, M Van GinnekenAbstract:Abstract This study explores the petrology of five giant (>400 μm) hydrated fine-grained Micrometeorites from the Transantarctic Mountain (TAM) Micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these Micrometeorites represent ∼2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of
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The thermal decomposition of fine-grained Micrometeorites, observations from mid-IR spectroscopy
Geochimica et Cosmochimica Acta, 2017Co-Authors: M D Suttle, Luigi Folco, Matthew J Genge, Sara S. RussellAbstract:Abstract We analysed 44 fine-grained and scoriaceous Micrometeorites. A bulk mid-IR spectrum (8–13 μm) for each grain was collected and the entire Micrometeorite population classified into 5 spectral groups, based on the positions of their absorption bands. Corresponding carbonaceous Raman spectra, textural observations from SEM-BSE and bulk geochemical data via EMPA were collected to aid in the interpretation of mid-IR spectra. The 5 spectral groups identified correspond to progressive thermal decomposition. Unheated hydrated chondritic matrix, composed predominantly of phyllosilicates, exhibit smooth, asymmetric spectra with a peak at ∼10 μm. Thermal decomposition of sheet silicates evolves through dehydration, dehydroxylation, annealing and finally by the onset of partial melting. Both CI-like and CM-like Micrometeorites are shown to pass through the same decomposition stages and produce similar mid-IR spectra. Using known temperature thresholds for each decomposition stage it is possible to assign a peak temperature range to a given Micrometeorite. Since the temperature thresholds for decomposition reactions are defined by the phyllosilicate species and the cation composition and that these variables are markedly different between CM and CI classes, atmospheric entry should bias the dust flux to favour the survival of CI-like grains, whilst preferentially melting most CM-like dust. However, this hypothesis is inconsistent with empirical observations and instead requires that the source ratio of CI:CM dust is heavily skewed in favour of CM material. In addition, a small population of anomalous grains are identified whose carbonaceous and petrographic characteristics suggest in-space heating and dehydroxylation have occurred. These grains may therefore represent regolith Micrometeorites derived from the surface of C-type asteroids. Since the spectroscopic signatures of dehydroxylates are distinctive, i.e. characterised by a reflectance peak at 9.0–9.5 μm, and since the surfaces of C-type asteroids are expected to be heated via impact gardening, we suggest that future spectroscopic investigations should attempt to identify dehydroxylate signatures in the reflectance spectra of young carbonaceous asteroid families.
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The weathering of Micrometeorites from the Transantarctic Mountains
Geochimica et Cosmochimica Acta, 2016Co-Authors: Matthias Van Ginneken, Luigi Folco, Matthew J Genge, Ralph P. HarveyAbstract:Abstract Micrometeorites are cosmic dust particles recovered from the Earth’s surface that dominate the influx of extraterrestrial material accreting to our planet. This paper provides the first in-depth study of the weathering of Micrometeorites within the Antarctic environment that will allow primary and secondary features to be distinguished. It is based on the analysis of 366 particles from Larkman Nunatak and 25 from the Transantarctic Mountain collection. Several important morphological categories of weathering effects were identified: (1) irregular and faceted cavities, (2) surface etch pits, (3) infilled cavities, (4) replaced silicate phases, and (5) hydrated and replaced metal. These features indicate that congruent dissolution of silicate phases, in particular olivine, is important in generating new pore space within particles. Comparison of the preservation of glass and olivine also indicates preferential dissolution of olivine by acidic solutions during low temperature aqueous alteration. Precipitation of new hydrous phases within cavities, in particular ferrihydrite and jarosite, results in pseudomorph textures within heavily altered particles. Glass, in contrast, is altered to palagonite gels and shows a sequential replacement indicative of varying water to rock ratios. Metal is variably replaced by Fe-oxyhydroxides and results in decreases in Ni/Fe ratio. In contrast, sulphides within metal are largely preserved. Magnetite, an essential component of Micrometeorites formed during atmospheric entry, is least altered by interaction with the terrestrial environment. The extent of weathering in the studied Micrometeorites is sensitive to differences in their primary mineralogy and varies significantly with particle type. Despite these differences, we propose a weathering scale for Micrometeorites based on both their degree of terrestrial alteration and the level of encrustation by secondary phases. The compositions and textures of weathering products, however, suggest open system behaviour and variable water to rock ratios that imply climatic variation over the lifetime of the Micrometeorite deposits.
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oxygen isotopes in cosmic spherules and the composition of the near earth interplanetary dust complex
Geochimica et Cosmochimica Acta, 2014Co-Authors: Carole Cordier, Luigi FolcoAbstract:Abstract A long-standing controversy in the Micrometeorite community regards the relative contribution of primitive asteroids or comets and of evolved asteroids to the interplanetary dust cloud. We compiled and studied a large set of oxygen isotopic data from the literature on cosmic spherules from different collections covering different influx periods within the last ∼1 Myr. Cosmic spherules (Micrometeorites melted during atmospheric entry) are the most abundant Micrometeorites in worldwide collections. According to several models, they are representative of the composition and origin of Micrometeorites >50 μm in size. Spherule statistics (136 spherules, 50–2280 μm in size) indicate that at least 20% of the micrometeoroid complex is fed by asteroids observed in the inner asteroid belt: the ordinary chondrite and secondarily the HED parent asteroids likely belonging to the S-type and V-type spectral classes, respectively. Another ∼60% (or more) is related to primitive objects of the Solar System with carbonaceous chondrite compositions: either primitive asteroids belonging to the C-, D- or P-type spectral classes in the outer asteroid belt or comets. Contribution from terrestrial planets has not been identified yet. Oxygen isotopes also document that the composition of the micrometeoroid complex is different from that of macroscopic meteoroids, since the latter is dominated by materials from evolved and differentiated asteroids rather than primitive asteroids or comets. Cosmic spherule statistics show that the contribution of ordinary chondrite material to the composition of the micrometeoroid complex increases with Micrometeorite size, thereby documenting a continuum between meteorites and Micrometeorites. The transition in terms of relative abundance of the two cosmic spherule populations occurs around ∼500 μm in size.
Folco L. - One of the best experts on this subject based on the ideXlab platform.
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The atmospheric entry of fine-grained Micrometeorites: The role of volatile gases in heating and fragmentation
'Wiley', 2021Co-Authors: Suttle Martin, S. S. Russell, Folco L., M J Genge, Van Ginneken M, Lin Q, Najorka J.Abstract:The early stages of atmospheric entry are investigated in four large (250–950 lm) unmelted Micrometeorites (three fine-grained and one composite), derived from the Transantarctic Mountain Micrometeorite collection. These particles have abundant, interconnected, secondary pore spaces which form branching channels and show evidence of enhanced heating along their channel walls. Additionally, a Micrometeorite with a doublewalled igneous rim is described, suggesting that some particles undergo volume expansion during entry. This study provides new textural data which links together entry heating processes known to operate inside micrometeoroids, thereby generating a more comprehensive model of their petrographic evolution. Initially, flash heated Micrometeorites develop a melt layer on their exterior; this igneous rim migrates inwards. Meanwhile, the particle core is heated by the decomposition of low-temperature phases and by volatile gas release. Where the igneous rim acts as a seal, gas pressures rise, resulting in the formation of interconnected voids and higher particle porosities. Eventually, the igneous rim is breached and gas exchange with the atmosphere occurs. This mechanism replaces inefficient conductive rim-to-core thermal gradients with more efficient particle-wide heating, driven by convective gas flow. Interconnected voids also increase the likelihood of particle fragmentation during entry and, may therefore explain the rarity of large fine-grained Micrometeorites among collections.Copyright © 2018, Suttle, M.D. et al. This document is the author’s final accepted version of the journal article. You are advised to consult the published version if you wish to cite from it
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Isotopic and textural analysis of giant unmelted Micrometeorites – identification of new material from intensely altered 16O-poor water-rich asteroids
'Elsevier BV', 2021Co-Authors: Suttle Martin, Folco L., Dionnet Z., Rotundi A., Gibson J., King A., R C Greenwood, Russell SaraAbstract:Bulk oxygen isotope data has the potential to match extraterrestrial samples to parent body sourcesbased on distinctive 18O and Δ 17 O ratios. We analysed 10 giant (>500µm) Micrometeorites using combined µCT and O-isotope analysis to pair internal textures to inferred parent body groups. We identify three ordinary chondrite particles (L and LL groups), four from CR chondrites and the first Micrometeorite from the enstatite chondrite (EH4) group. In addition, two Micrometeorites are from hydrated carbonaceous chondrite parent bodies with 16 O-poor isotopic compositions above the terrestrial fractionation line. They experienced intense aqueous alteration, contain pseudomorphic chondrules and are petrographically similar to the CM1/CR1 chondrites. These Micrometeorites may be members of the newly established CY chondrites and/or derived from the enigmatic “Group 4” Micrometeorite population, previously identified by Yada et al., 2005 [GCA, 69:5789-5804], Suavet et al., 2010 [EPSL, 293:313-320] (and others). One of our 16 O-poor Micrometeorite plots on the same isotopic trendline as the CO, CM and CY chondrites – “the CM mixing line” (with a slope of ~0.7 and a 17 O intercept of -4.23‰), implies a close relationship and potentially a genetic link to these hydrated chondrites. If position along the CM mixing line reflects the amount of 16 O-poor (heavy) water-ice accreted onto the parent body at formation, then the CY chondrites and these 16 O-poor Micrometeorites must have accreted at least as much water-ice as CM chondrites but potentially more. In addition, thermal metamorphism could have played a role in further raising the bulk O isotope compositions through the preferential loss of isotopically light water during phyllosilicate dehydration. The study of Micrometeorites provides insights into asteroid belt diversity through the discovery of material not currently sampled by larger meteorites, perhaps as a result of atmospheric entry biases preventing the survival of large blocks of friable hydrated material.Copyright © 2021, Suttle MD, et al. This document is the author’s final accepted version of the journal article. You are advised to consult the published version if you wish to cite from it
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Isotopic and textural analysis of giant unmelted Micrometeorites – identification of new material from intensely altered 16O-poor water-rich asteroids
'Elsevier BV', 2020Co-Authors: Dionnet Z., Folco L., Franchi Ian, Gibson Jennifer, Greenwood Richard, Rotundi A., King Ashley, Russell S.s.Abstract:Bulk oxygen isotope data has the potential to match extraterrestrial samples to parent body sources based on distinctive δ18O and Δ17O ratios. We analysed 10 giant (>500µm) Micrometeorites using combined µCT and O-isotope analysis to pair internal textures to inferred parent body groups. We identify three ordinary chondrite particles (L and LL groups), four from CR chondrites and the first Micrometeorite from the enstatite chondrite (EH4) group. In addition, two Micrometeorites are from hydrated carbonaceous chondrite parent bodies with 16O-poor isotopic compositions above the terrestrial fractionation line. They experienced intense aqueous alteration, contain pseudomorphic chondrules and are petrographically similar to the CM1/CR1 chondrites. These Micrometeorites may be members of the newly established CY chondrites and/or derived from the enigmatic “Group 4” Micrometeorite population, previously identified by Yada et al., 2005 [GCA, 69:5789-5804], Suavet et al., 2010 [EPSL, 293:313-320] (and others). One of our 16O-poor Micrometeorite plots on the same isotopic trendline as the CO, CM and CY chondrites – “the CM mixing line” (with a slope of ~0.7 and a δ17O intercept of -4.23‰), implies a close relationship and potentially a genetic link to these hydrated chondrites. If position along the CM mixing line reflects the amount of 16O-poor (heavy) water-ice accreted onto the parent body at formation, then the CY chondrites and these 16O-poor Micrometeorites must have accreted at least as much water-ice as CM chondrites but potentially more. In addition, thermal metamorphism could have played a role in further raising the bulk O-isotope compositions through the preferential loss of isotopically light water during phyllosilicate dehydration. The study of Micrometeorites provides insights into asteroid belt diversity through the discovery of material not currently sampled by larger meteorites, perhaps as a result of atmospheric entry biases preventing the survival of large blocks of friable hydrated material
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Isotopic and textural analysis of giant unmelted Micrometeorites – identification of new material from intensely altered 16O-poor water-rich asteroids
'Elsevier BV', 2020Co-Authors: Suttle M. D., Folco L., Dionnet Z., Rotundi A., Gibson J., Greenwood R. C., King A., Russell S. S.Abstract:Bulk oxygen isotope data has the potential to match extraterrestrial samples to parent body sources based on distinctive δ18O and Δ17O ratios. We analysed 10 giant (>500 μm) Micrometeorites using combined micro-Computer Tomography (μCT) and O-isotope analysis to pair internal textures to inferred parent body groups. We identify three ordinary chondrite particles (L and LL groups), four from CR chondrites and the first Micrometeorite from the enstatite chondrite (EH4) group. In addition, two Micrometeorites are from hydrated carbonaceous chondrite parent bodies with 16O-poor isotopic compositions and plot above the terrestrial fractionation line. They experienced intense aqueous alteration, contain pseudomorphic chondrules and are petrographically similar to the CM1/CR1 chondrites. These Micrometeorites may be members of the newly established CY chondrites and/or derived from the enigmatic “Group 4” Micrometeorite population, previously identified by Yada et al., 2005 [GCA, 69:5789-5804], Suavet et al., 2010 [EPSL, 293:313-320] (and others). One of our 16O-poor Micrometeorite plots on the same isotopic trendline as the CO, CM and CY chondrites – “the CM mixing line” (with a slope of ∼0.7 and a δ17O intercept of -4.23‰), this implies a close relationship and potentially a genetic link to these hydrated chondrites. If position along the CM mixing line reflects the amount of 16O-poor (heavy) water-ice accreted onto the parent body at formation, then the CY chondrites and these 16O-poor Micrometeorites must have accreted at least as much water-ice as CM chondrites but potentially more. In addition, thermal metamorphism could have played a role in further raising the bulk O-isotope compositions through the preferential loss of isotopically light water during phyllosilicate dehydration. The study of Micrometeorites provides insights into asteroid belt diversity through the discovery of material not currently sampled by larger meteorites, perhaps as a result of atmospheric entry biases preventing the survival of large blocks of friable hydrated material
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The Extraterrestrial Dust Flux: Size Distribution and Mass Contribution Estimates Inferred From the Transantarctic Mountains (TAM) Micrometeorite Collection
'American Geophysical Union (AGU)', 2020Co-Authors: Suttle M. D., Folco L.Abstract:This study explores the long‐duration (0.8–2.3 Ma), time‐averaged Micrometeorite flux (mass and size distribution) reaching Earth, as recorded by the Transantarctic Mountains (TAM) Micrometeorite collection. We investigate a single sediment trap (TAM65), performing an exhaustive recovery and characterization effort and identifying 1,643 Micrometeorites (between 100 and 2,000 μm). Approximately 7% of particles are unmelted or scoriaceous, of which 75% are fine‐grained. Among cosmic spherules, 95.6% are silicate‐dominated S‐types, and further subdivided into porphyritic (16.9%), barred olivine (19.9%), cryptocrystalline (51.6%), and vitreous (7.5%). Our (rank)‐size distribution is fit against a power law with a slope of −3.9 (R2 = 0.98) over the size range 200–700 μm. However, the distribution is also bimodal, with peaks centered at ~145 and ~250 μm. Remarkably similar peak positions are observed in the Larkman Nunatak data. These observations suggest that the Micrometeorite flux is composed of multiple dust sources with distinct size distributions. In terms of mass, the TAM65 trap contains 1.77 g of extraterrestrial dust in 15 kg of sediment (<5 mm). Upscaling to a global annual estimate gives 1,555 (±753) t/year—consistent with previous Micrometeorite abundance estimates and almost identical to the South Pole Water Well estimate (~1,600 t/year), potentially indicating minimal variation in the background cosmic dust flux over the Quaternary. The greatest uncertainty in our mass flux calculation is the accumulation window. A minimum age (0.8 Ma) is robustly inferred from the presence of Australasian microtektites, while the upper age (~2.3 Ma) is loosely constrained based on 10Be exposure dating of glacial surfaces at Roberts Butte (6 km from our sample site)
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The atmospheric entry of fine-grained Micrometeorites: The role of volatile gases in heating and fragmentation
'Wiley', 2021Co-Authors: Suttle Martin, S. S. Russell, Folco L., M J Genge, Van Ginneken M, Lin Q, Najorka J.Abstract:The early stages of atmospheric entry are investigated in four large (250–950 lm) unmelted Micrometeorites (three fine-grained and one composite), derived from the Transantarctic Mountain Micrometeorite collection. These particles have abundant, interconnected, secondary pore spaces which form branching channels and show evidence of enhanced heating along their channel walls. Additionally, a Micrometeorite with a doublewalled igneous rim is described, suggesting that some particles undergo volume expansion during entry. This study provides new textural data which links together entry heating processes known to operate inside micrometeoroids, thereby generating a more comprehensive model of their petrographic evolution. Initially, flash heated Micrometeorites develop a melt layer on their exterior; this igneous rim migrates inwards. Meanwhile, the particle core is heated by the decomposition of low-temperature phases and by volatile gas release. Where the igneous rim acts as a seal, gas pressures rise, resulting in the formation of interconnected voids and higher particle porosities. Eventually, the igneous rim is breached and gas exchange with the atmosphere occurs. This mechanism replaces inefficient conductive rim-to-core thermal gradients with more efficient particle-wide heating, driven by convective gas flow. Interconnected voids also increase the likelihood of particle fragmentation during entry and, may therefore explain the rarity of large fine-grained Micrometeorites among collections.Copyright © 2018, Suttle, M.D. et al. This document is the author’s final accepted version of the journal article. You are advised to consult the published version if you wish to cite from it
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isotopic and textural analysis of giant unmelted Micrometeorites identification of new material from intensely altered 16o poor water rich asteroids
Earth and Planetary Science Letters, 2020Co-Authors: Luigi Folco, M D Suttle, Zelia Dionnet, I A Franchi, J M Gibson, R C Greenwood, A Rotundi, A King, S. S. RussellAbstract:Abstract Bulk oxygen isotope data has the potential to match extraterrestrial samples to parent body sources based on distinctive δ 18 O and Δ 17 O ratios. We analysed 10 giant (>500 μm) Micrometeorites using combined micro-Computer Tomography (μCT) and O-isotope analysis to pair internal textures to inferred parent body groups. We identify three ordinary chondrite particles (L and LL groups), four from CR chondrites and the first Micrometeorite from the enstatite chondrite (EH4) group. In addition, two Micrometeorites are from hydrated carbonaceous chondrite parent bodies with 16O-poor isotopic compositions and plot above the terrestrial fractionation line. They experienced intense aqueous alteration, contain pseudomorphic chondrules and are petrographically similar to the CM1/CR1 chondrites. These Micrometeorites may be members of the newly established CY chondrites and/or derived from the enigmatic “Group 4” Micrometeorite population, previously identified by Yada et al., 2005 [GCA, 69:5789-5804], Suavet et al., 2010 [EPSL, 293:313-320] (and others). One of our 16O-poor Micrometeorite plots on the same isotopic trendline as the CO, CM and CY chondrites – “the CM mixing line” (with a slope of ∼0.7 and a δ 17 O intercept of -4.23‰), this implies a close relationship and potentially a genetic link to these hydrated chondrites. If position along the CM mixing line reflects the amount of 16O-poor (heavy) water-ice accreted onto the parent body at formation, then the CY chondrites and these 16O-poor Micrometeorites must have accreted at least as much water-ice as CM chondrites but potentially more. In addition, thermal metamorphism could have played a role in further raising the bulk O-isotope compositions through the preferential loss of isotopically light water during phyllosilicate dehydration. The study of Micrometeorites provides insights into asteroid belt diversity through the discovery of material not currently sampled by larger meteorites, perhaps as a result of atmospheric entry biases preventing the survival of large blocks of friable hydrated material.
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intense aqueous alteration on c type asteroids perspectives from giant fine grained Micrometeorites
Geochimica et Cosmochimica Acta, 2019Co-Authors: Luigi Folco, M D Suttle, Matthew J Genge, S. S. Russell, Jens Najorka, M Van GinnekenAbstract:Abstract This study explores the petrology of five giant (>400 μm) hydrated fine-grained Micrometeorites from the Transantarctic Mountain (TAM) Micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these Micrometeorites represent ∼2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of
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Analysis of Cosmic Spherule Candidates from the Kwajalein Micrometeorite Collection
2015Co-Authors: P. J. Wozniakiewicz, M. C. Price, J. P. Bradley, H. A. Ishii, S. S. Russell, Michael E. Zolensky, Donald E. BrownleeAbstract:The Kwajalein Micrometeorite collection utilised high volume air samplers fitted with 5 micrometer laser-etched polycarbonate membrane filters to capture particles directly from the atmosphere. The filters were changed weekly over several months throughout 2011/12, providing the opportunity to investigate the contemporary flux of Micrometeorites. We recently reported the results of our initial survey of cosmic spherule-like particles on several of these filters. We identified three main groups of particle based on bulk compositions: 1. Silicate spherules rich in Mg, Ca and Fe, 2. Silicate spherules rich in Al, Ca, K and/or Na and 3. Fe-rich spherules. Abundances appeared to change over time suggesting links with celestial activity (e.g. meteor showers), however, spherules similar to groups 2 and 3 can be produced by terrestrial and anthropogenic activity (e.g. volcanic microspherules exhibit similar compositions to group 2 spherules and metallic spherules similar to those of group 3 can be formed during fuel combustion). We are now studying the internal structures and chemistries of these spherules and comparing against cosmic spherules identified in other collections to confrim their origins and further contrain the contemporary Micrometeorite flux. Particles are being picked, embedded in resin and polished through to reveal their interiors. Here we will describe our ongoing analyses of these particles via SEM. We will also introduce our new collection using this method that is currently being performed in the Antarctic.
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hydrogen isotopic composition of water from fossil Micrometeorites in howardites
Geochimica et Cosmochimica Acta, 2005Co-Authors: S. S. Russell, Michael E. Zolensky, Matthieu Gounelle, Olivier Alard, Cecile Engrand, P A Bland, J. DupratAbstract:We have measured the hydrogen isotopic composition (D/H ratios) of the water from 13 carbonaceous chondritic microclasts (CCMs, size <1 mm) trapped in two howardites (Kapoeta and Yamato-793497) early in the evolution of Solar System. The division into tochilinite-rich; magnetite-rich, olivine-poor; magnetite-rich, olivine-rich CCM types is corroborated by the hydrogen isotopic compositions. Both mineralogy and hydrogen isotopic compositions demonstrate that tochilinite-rich CCMs represent CM2 chondritic matter. In contrast, there is no good match between the isotopic and mineralogical properties of the magnetite-rich CCMs and the known groups of carbonaceous chondrites, suggesting that magnetite-rich CCMs represent a new kind of chondritic matter, not yet sampled in meteorite collections. This demonstrates that the view of the asteroid belt revealed by the collection of meteorites is incomplete. The study of (micro)clasts offers a unique opportunity to better decipher the nature and relative abundance of asteroids. The average hydrogen isotopic composition of water belonging to CCMs, D/H = (152.0 +/- 4.8) X 10(-6) (1 sigma(m)), is similar to that of Antarctic Micrometeorites (AMMs), D/H = (161.2 +/- 3.8) X 10(-6) (1 sigma(m)). The similarity, in terms of mineralogy and hydrogen isotopic composition, between CCMs and AMMs demonstrates that the composition of the Micrometeorites has not been modified over the whole history of the Solar System. It indicates that the composition of the Micrometeorite flux onto Earth has been, and is, dominated by a mixture of CM2-like; magnetite-rich, olivine-poor; magnetite-rich, olivine-rich carbonaceous chondritic matter exemplified by CCMs found in howardites. Because CCMs have not suffered atmospheric entry, they provide an abundant source of pristine Micrometeorites. The average D/H ratio of the whole population of CCMs is identical within errors to that of the Earth (149 +/- 3 X 10(-6)). The match between the CCMs D/H ratio and that of the Earth is especially remarkable because 1) three different populations of CCMs are needed to make the D/H ratio of the Earth; 2) there is no single carbonaceous chondrite group for which a similar match exists. This observation suggests that CCMs population might be representative of the late veneer agent(s) that delivered water to the Earth.