139 research outputs found
COSIMA-Rosetta calibration for in-situ characterization of 67P/Churyumov-Gerasimenko cometary inorganic compounds
20 pages, 3 figures, 5 tablesInternational audienceCOSIMA (COmetary Secondary Ion Mass Analyser) is a time-of-flight secondary ion mass spectrometer (TOF-SIMS) on board the Rosetta space mission. COSIMA has been designed to measure the composition of cometary dust grains. It has a mass resolution m/{\Delta}m of 1400 at mass 100 u, thus enabling the discrimination of inorganic mass peaks from organic ones in the mass spectra. We have evaluated the identification capabilities of the reference model of COSIMA for inorganic compounds using a suite of terrestrial minerals that are relevant for cometary science. Ground calibration demonstrated that the performances of the flight model were similar to that of the reference model. The list of minerals used in this study was chosen based on the mineralogy of meteorites, interplanetary dust particles and Stardust samples. It contains anhydrous and hydrous ferromagnesian silicates, refractory silicates and oxides (present in meteoritic Ca-Al-rich inclusions), carbonates, and Fe-Ni sulfides. From the analyses of these minerals, we have calculated relative sensitivity factors for a suite of major and minor elements in order to provide a basis for element quantification for the possible identification of major mineral classes present in the cometary grains
Triton Haze Analogs: The Role of Carbon Monoxide in Haze Formation
Triton is the largest moon of the Neptune system and possesses a thin nitrogen atmosphere with trace amounts of carbon monoxide and methane, making it of similar composition to that of the dwarf planet Pluto. Like Pluto and Saturn\u27s moon Titan, Triton has a haze layer thought to be composed of organics formed through photochemistry. Here, we perform atmospheric chamber experiments of 0.5% CO and 0.2% CH4 in N2 at 90 K and 1 mbar to generate Triton haze analogs. We then characterize the physical and chemical properties of these particles. We measure their production rate, their bulk composition with combustion analysis, their molecular composition with very high resolution mass spectrometry, and their transmission and reflectance from the optical to the near-infrared with Fourier Transform Infrared (FTIR) Spectroscopy. We compare these properties to existing measurements of Triton\u27s tenuous atmosphere and surface, as well as contextualize these results in view of all the small, hazy, nitrogen-rich worlds of our solar system. We find that carbon monoxide present at greater mixing ratios than methane in the atmosphere can lead to significantly oxygen- and nitrogen-rich haze materials. These Triton haze analogs have clear observable signatures in their near-infrared spectra, which may help us differentiate the mechanisms behind haze formation processes across diverse solar system bodies
Elephant Moraine 96029, a very mildly aqueously altered and heated CM carbonaceous chondrite: Implications for the drivers of parent body processing
Elephant Moraine (EET) 96029 is a CMcarbonaceous chondrite regolith breccia with evidence for unusually mild aqueous alteration, a later phase of heating and terrestrial weathering. The presence of phyllosilicates and carbonates within chondrules and the fine-grained matrix indicates that this meteorite was aqueously altered in its parent body. Features showing that water-mediated processing was arrested at a very early stage include a matrix with a low magnesium/iron ratio, chondrules whose mesostasis contains glass and/or quench crystallites, and a gehlenite-bearing calcium- and aluminium-rich inclusion. EET 96029 is also rich in Fe,Ni metal relative to other CM chondrites, and more was present prior to its partial replacement by goethite during Antarctic weathering. In combination, these properties indicate that EET 96029 is one of the least aqueously altered CMs yet described (CM2.7) and so provides new insights into the original composition of its parent body. Following aqueous alteration, and whilst still in the parent body regolith, the meteorite was heated to ~400â600 °C by impacts or solar radiation. Heating led to the amorphisation and dehydroxylation of serpentine, replacement of tochilinite by magnetite, loss of sulphur from the matrix, and modification to the structure of organic matter that includes organic nanoglobules. Significant differences between samples in oxygen isotope compositions, and water/hydroxyl contents, suggests that the meteorite contains lithologies that have undergone different intensities of heating. EET 96029 may be more representative of the true nature of parent body regoliths than many other CM meteorites, and as such can help interpret results from the forthcoming missions to study and return samples from C-complex asteroids
Modal mineralogy of CI and CI-like chondrites by X-ray diffraction
The CI chondrites are some of the most hydrated meteorites available to study, making them ideal samples with which to investigate aqueous processes in the early Solar System. Here, we have used position-sensitive-detector X-ray diffraction (PSD-XRD) to quantify the abundance of minerals in bulk samples of the CI chondrite falls Alais, Orgueil and Ivuna, and the Antarctic CI-like chondrites Y-82162 and Y-980115. We find that Alais, Orgueil and Ivuna are dominated by a mixed serpentine/saponite phyllosilicate (81â84 vol%), plus minor magnetite (6â10%), sulphides (4â7%) and carbonates (<3%). This reflects an extended period of aqueous alteration and the near-complete transformation of anhydrous phases into a secondary mineral assemblage. The similarity in total abundance of phyllosilicate suggests that the CI chondrites all experienced the same degree of aqueous alteration on the parent body.
In contrast, Y-82162 contains a highly disordered serpentine/saponite phyllosilicate (68 vol%), sulphide (19%), olivine (11%) and magnetite (2%). This mineralogy is distinct from that of the CI chondrites, attesting to both a different starting mineralogy and alteration history. The structure and relatively low abundance of the phyllosilicate, and the high abundance of olivine, are consistent with previous observations that Y-82162 represents CI-like material that following aqueous alteration suffered thermal metamorphism at temperatures >500 °C. Similarly, Y-980115 contains disordered serpentine/saponite (71 vol%), sulphide (19%), olivine (8%) and magnetite (2%), confirming that it too is a thermally metamorphosed CI-like chondrite. We suggest that the CI-like chondrites are derived from a different parent body than the CI chondrites, which underwent short-lived thermal metamorphism due to impacts and/or solar radiation
Carbon-rich dust in comet 67P/Churyumov-Gerasimenko measured by COSIMA/Rosetta
Cometary ices are rich in CO2, CO and organic volatile
compounds, but the carbon content of cometary dust was only measured for
the Oort Cloud comet 1P/Halley, during its flyby in 1986. The COmetary
Secondary Ion Mass Analyzer (COSIMA)/Rosetta mass spectrometer
analysed dust particles with sizes ranging from 50 to 1000Â ÎŒm, collected
over 2 yr, from 67P/Churyumov-Gerasimenko (67P), a Jupiter family
comet. Here, we report 67P dust composition focusing on the elements C
and O. It has a high carbon content (atomic | |â )
close to the solar value and comparable to the 1P/Halley data. From
COSIMA measurements, we conclude that 67P particles are made of nearly
50 per cent organic matter in mass, mixed with mineral phases that are
mostly anhydrous. The whole composition, rich in carbon and non-hydrated
minerals, points to a primitive matter that likely preserved its
initial characteristics since the comet accretion in the outer regions
of the protoplanetary disc.</p
Nitrogen-to-carbon atomic ratio measured by COSIMA in the particles of comet 67P/ChuryumovâGerasimenko
The COmetary Secondary Ion Mass Analyzer (COSIMA) on board the Rosetta mission has analysed numerous cometary dust particles collected at very low velocities (a few m sâ1)
in the environment of comet 67P/ChuryumovâGerasimenko (hereafter 67P).
In these particles, carbon and nitrogen are expected mainly to be part
of the organic matter. We have measured the nitrogen-to-carbon (N/C)
atomic ratio of 27 cometary particles. It ranges from 0.018 to 0.06 with
an averaged value of 0.035 ± 0.011. This is compatible with the
measurements of the particles of comet 1P/Halley and is in the lower
range of the values measured in comet 81P/Wild 2 particles brought back
to Earth by the Stardust mission. Moreover, the averaged value
found in 67P particles is also similar to the one found in the insoluble
organic matter extracted from CM, CI and CR carbonaceous chondrites and
to the bulk values measured in most interplanetary dust particles and
micrometeorites. The close agreement of the N/C atomic ratio in all
these objects indicates that their organic matters share some
similarities and could have a similar chemical origin. Furthermore,
compared to the abundances of all the detected elements in the particles
of 67P and to the elemental solar abundances, the nitrogen is depleted
in the particles and the nucleus of 67P as was previously inferred also
for comet 1P/Halley. This nitrogen depletion could constrain the
formation scenarios of cometary nuclei.</p
Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy
The CI and CI-like chondrites provide a record of aqueous alteration in the early solar system. However, the CI-like chondrites differ in having also experienced a late stage period of thermal metamorphism. In order to constrain the nature and extent of the aqueous and thermal alteration, we have investigated the bulk mineralogy and abundance of H2O in the CI and CI-like chondrites using thermogravimetric analysis and infrared spectroscopy.
The CI chondrites Ivuna and Orgueil show significant mass loss (28.5â31.8 wt.%) upon heating to 1000 °C due to dehydration and dehydroxylation of abundant phyllosilicates and Fe-(oxy)hydroxides and the decomposition of Fe-sulphides, carbonates and organics. Infrared spectra for Ivuna and Orgueil have a prominent 3-ÎŒm feature due to bound âOH/H2O in phyllosilicates and Fe-(oxy)hydroxides and only a minor 11-ÎŒm feature from anhydrous silicates. These characteristics are consistent with previous studies indicating that the CI chondrites underwent near-complete aqueous alteration. Similarities in the total abundance of H2O and 3 ÎŒm/11 ÎŒm ratio suggest that there is no difference in the relative degree of hydration experienced by Ivuna and Orgueil.
In contrast, the CI-like chondrites Y-82162 and Y-980115 show lower mass loss (13.8â18.8 wt.%) and contain >50 % less H2O than the CI chondrites. The 3-ÎŒm feature is almost absent from spectra of Y-82162 and Y-980115 but the 11-ÎŒm feature is intense. The CI-like chondrites experienced thermal metamorphism at temperatures >500 °C that initially caused dehydration and dehydroxylation of phyllosilicates before partial recrystallization back into anhydrous silicates. The surfaces of many C-type asteroids were probably heated through impact metamorphism and/or solar radiation, so thermally altered carbonaceous chondrites are likely good analogues for samples that will be returned by the Hayabusa-2 and OSIRIS-REx missions
Empreinte moléculaire des processus post-accrétionnels dans la matiÚre organique des chondrites carbonées
Type 1 and 2 carbonaceous chondrites include the most chemically and petrologically pristine meteorites. This intactness goes along with the abundance of organic matter which is a phase of choice to investigate the presolar material processing in the nebula and then on the first bodies. The purpose of this thesis is to study the influence of post-accretional processes on the molecular characteristics of organic matter and in particular the extent of oxidation effects due to aqueous alteration. We have carried out a comparative study based on the carbon structure and functional analysis of more than ten meteorites whose geologic histories were independently determined. The redox degree of sulfur in the insoluble fraction was measured by SK-Xanes spectroscopy. FT-IR spectroscopy gave access to the fine structures of aliphatic chains and oxygen-rich functions. Orbitrap very high resolution mass spectrometry was used to describe the heteroatomic diversity of soluble molecules in the Renazzo (CR2) chondrite. The aliphatic chains of CI chondrites and Murchison differ from others by a higher and unchanging abundance of methyl groups. Type 1 chondrites are the only carriers of oxidized sulfur functions whereas the sulfur speciation in type 2 chondrites is invariable. For all studied chondrites, the carbonyl groups are mainly under the form of ketones and their abundance canât be related to the degree of aqueous alteration. Any parameters we have measured in this study lead us to conclude that the molecular variability among type 1 and 2 carbonaceous chondrites are less due to the footprint left by the hydrothermal activity than due to the heterogeneity of an organic precursor accreted by each parent body. In particular, our measurements invalidate the hypothesis that the alteration would cause an oxidative conversion of aliphatic chains to carboxylic acid functions.Les chondrites carbonĂ©es de type 1 et 2 comprennent les mĂ©tĂ©orites les plus primitives dâun point de vue chimique et pĂ©trologique. Ce caractĂšre primitif est associĂ© Ă lâabondance de matiĂšre organique qui est une phase privilĂ©giĂ©e pour lâĂ©tude des phĂ©nomĂšnes concernant lâhĂ©ritage du matĂ©riel prĂ©solaire et sa transformation dans la nĂ©buleuse puis sur les premiers corps. Lâobjet de cette thĂšse est lâĂ©tude de lâinfluence des processus post-accrĂ©tionnels sur les caractĂ©ristiques molĂ©culaires de la matiĂšre organique et en particulier la mesure des effets dâoxydation dus Ă lâaltĂ©ration aqueuse. Nous avons menĂ© une Ă©tude comparative basĂ©e sur la structure carbonĂ©e et lâanalyse des fonctions oxygĂ©nĂ©es et soufrĂ©es dâune dizaine de mĂ©tĂ©orites dont les histoires gĂ©ologiques ont Ă©tĂ© dĂ©terminĂ©es par ailleurs. Le degrĂ© dâoxydation du soufre, hĂ©tĂ©roatome mineur dans la fraction insoluble, a Ă©tĂ© mesurĂ© par micro-spectromĂ©trie SK-Xanes. La spectroscopie FT-IR a permis la description des structures fines des chaines carbonĂ©es et des fonctions riches en oxygĂšne, hĂ©tĂ©roatome majeur. La spectromĂ©trie de masse Ă trĂšs haute rĂ©solution Orbitrap a Ă©tĂ© utilisĂ©e pour dĂ©crire la diversitĂ© hĂ©tĂ©roatomique des molĂ©cules solubles de la chondrite Renazzo (CR2). Les chaines carbonĂ©es des chondrites de classe CI et Murchison se diffĂ©rencient de celle des autres mĂ©tĂ©orites par une abondance en groupements terminaux mĂ©thyles Ă la fois supĂ©rieure et invariable. Les chondrites de type 1 sont les seules porteuses de fonctions soufrĂ©es oxydĂ©es acides alors que la spĂ©ciation du soufre dans les chondrites de type 2 est invariable. De la mĂȘme façon, et cette fois pour lâensemble des chondrites Ă©tudiĂ©es, les groupements carbonyles sont majoritairement dans les fonctions cĂ©tones, en proportion indĂ©pendante du degrĂ© dâaltĂ©ration aqueuse. Tous les paramĂštres mesurĂ©s dans cette Ă©tude nous poussent Ă conclure que la variabilitĂ© molĂ©culaire au sein des chondrites carbonĂ©es de type 1 et 2 trouve moins son origine dans lâempreinte de lâhydrothermalisme que dans une hĂ©tĂ©rogĂ©nĂ©itĂ© du prĂ©curseur organique accrĂ©tĂ© par chaque corps parent. En particulier, nos mesures invalident lâhypothĂšse selon laquelle lâaltĂ©ration serait Ă lâorigine dâune conversion oxydative des chaines carbonĂ©es en fonctions acides carboxyliques
Primordial history of the chondritic organic matter
Les chondrites carbonĂ©es de type 1 et 2 comprennent les mĂ©tĂ©orites les plus primitives dâun point de vue chimique et pĂ©trologique. Ce caractĂšre primitif est associĂ© Ă lâabondance de matiĂšre organique qui est une phase privilĂ©giĂ©e pour lâĂ©tude des phĂ©nomĂšnes concernant lâhĂ©ritage du matĂ©riel prĂ©solaire et sa transformation dans la nĂ©buleuse puis sur les premiers corps. Lâobjet de cette thĂšse est lâĂ©tude de lâinfluence des processus post-accrĂ©tionnels sur les caractĂ©ristiques molĂ©culaires de la matiĂšre organique et en particulier la mesure des effets dâoxydation dus Ă lâaltĂ©ration aqueuse. Nous avons menĂ© une Ă©tude comparative basĂ©e sur la structure carbonĂ©e et lâanalyse des fonctions oxygĂ©nĂ©es et soufrĂ©es dâune dizaine de mĂ©tĂ©orites dont les histoires gĂ©ologiques ont Ă©tĂ© dĂ©terminĂ©es par ailleurs. Le degrĂ© dâoxydation du soufre, hĂ©tĂ©roatome mineur dans la fraction insoluble, a Ă©tĂ© mesurĂ© par micro-spectromĂ©trie SK-Xanes. La spectroscopie FT-IR a permis la description des structures fines des chaines carbonĂ©es et des fonctions riches en oxygĂšne, hĂ©tĂ©roatome majeur. La spectromĂ©trie de masse Ă trĂšs haute rĂ©solution Orbitrap a Ă©tĂ© utilisĂ©e pour dĂ©crire la diversitĂ© hĂ©tĂ©roatomique des molĂ©cules solubles de la chondrite Renazzo (CR2). Les chaines carbonĂ©es des chondrites de classe CI et Murchison se diffĂ©rencient de celle des autres mĂ©tĂ©orites par une abondance en groupements terminaux mĂ©thyles Ă la fois supĂ©rieure et invariable. Les chondrites de type 1 sont les seules porteuses de fonctions soufrĂ©es oxydĂ©es acides alors que la spĂ©ciation du soufre dans les chondrites de type 2 est invariable. De la mĂȘme façon, et cette fois pour lâensemble des chondrites Ă©tudiĂ©es, les groupements carbonyles sont majoritairement dans les fonctions cĂ©tones, en proportion indĂ©pendante du degrĂ© dâaltĂ©ration aqueuse. Tous les paramĂštres mesurĂ©s dans cette Ă©tude nous poussent Ă conclure que la variabilitĂ© molĂ©culaire au sein des chondrites carbonĂ©es de type 1 et 2 trouve moins son origine dans lâempreinte de lâhydrothermalisme que dans une hĂ©tĂ©rogĂ©nĂ©itĂ© du prĂ©curseur organique accrĂ©tĂ© par chaque corps parent. En particulier, nos mesures invalident lâhypothĂšse selon laquelle lâaltĂ©ration serait Ă lâorigine dâune conversion oxydative des chaines carbonĂ©es en fonctions acides carboxyliques.Type 1 and 2 carbonaceous chondrites include the most chemically and petrologically pristine meteorites. This intactness goes along with the abundance of organic matter which is a phase of choice to investigate the presolar material processing in the nebula and then on the first bodies. The purpose of this thesis is to study the influence of post-accretional processes on the molecular characteristics of organic matter and in particular the extent of oxidation effects due to aqueous alteration. We have carried out a comparative study based on the carbon structure and functional analysis of more than ten meteorites whose geologic histories were independently determined. The redox degree of sulfur in the insoluble fraction was measured by SK-Xanes spectroscopy. FT-IR spectroscopy gave access to the fine structures of aliphatic chains and oxygen-rich functions. Orbitrap very high resolution mass spectrometry was used to describe the heteroatomic diversity of soluble molecules in the Renazzo (CR2) chondrite. The aliphatic chains of CI chondrites and Murchison differ from others by a higher and unchanging abundance of methyl groups. Type 1 chondrites are the only carriers of oxidized sulfur functions whereas the sulfur speciation in type 2 chondrites is invariable. For all studied chondrites, the carbonyl groups are mainly under the form of ketones and their abundance canât be related to the degree of aqueous alteration. Any parameters we have measured in this study lead us to conclude that the molecular variability among type 1 and 2 carbonaceous chondrites are less due to the footprint left by the hydrothermal activity than due to the heterogeneity of an organic precursor accreted by each parent body. In particular, our measurements invalidate the hypothesis that the alteration would cause an oxidative conversion of aliphatic chains to carboxylic acid functions
Empreinte moléculaire des processus post-accrétionnels dans la matiÚre organique des chondrites carbonées
Type 1 and 2 carbonaceous chondrites include the most chemically and petrologically pristine meteorites. This intactness goes along with the abundance of organic matter which is a phase of choice to investigate the presolar material processing in the nebula and then on the first bodies. The purpose of this thesis is to study the influence of post-accretional processes on the molecular characteristics of organic matter and in particular the extent of oxidation effects due to aqueous alteration. We have carried out a comparative study based on the carbon structure and functional analysis of more than ten meteorites whose geologic histories were independently determined. The redox degree of sulfur in the insoluble fraction was measured by SK-Xanes spectroscopy. FT-IR spectroscopy gave access to the fine structures of aliphatic chains and oxygen-rich functions. Orbitrap very high resolution mass spectrometry was used to describe the heteroatomic diversity of soluble molecules in the Renazzo (CR2) chondrite. The aliphatic chains of CI chondrites and Murchison differ from others by a higher and unchanging abundance of methyl groups. Type 1 chondrites are the only carriers of oxidized sulfur functions whereas the sulfur speciation in type 2 chondrites is invariable. For all studied chondrites, the carbonyl groups are mainly under the form of ketones and their abundance canât be related to the degree of aqueous alteration. Any parameters we have measured in this study lead us to conclude that the molecular variability among type 1 and 2 carbonaceous chondrites are less due to the footprint left by the hydrothermal activity than due to the heterogeneity of an organic precursor accreted by each parent body. In particular, our measurements invalidate the hypothesis that the alteration would cause an oxidative conversion of aliphatic chains to carboxylic acid functions.Les chondrites carbonĂ©es de type 1 et 2 comprennent les mĂ©tĂ©orites les plus primitives dâun point de vue chimique et pĂ©trologique. Ce caractĂšre primitif est associĂ© Ă lâabondance de matiĂšre organique qui est une phase privilĂ©giĂ©e pour lâĂ©tude des phĂ©nomĂšnes concernant lâhĂ©ritage du matĂ©riel prĂ©solaire et sa transformation dans la nĂ©buleuse puis sur les premiers corps. Lâobjet de cette thĂšse est lâĂ©tude de lâinfluence des processus post-accrĂ©tionnels sur les caractĂ©ristiques molĂ©culaires de la matiĂšre organique et en particulier la mesure des effets dâoxydation dus Ă lâaltĂ©ration aqueuse. Nous avons menĂ© une Ă©tude comparative basĂ©e sur la structure carbonĂ©e et lâanalyse des fonctions oxygĂ©nĂ©es et soufrĂ©es dâune dizaine de mĂ©tĂ©orites dont les histoires gĂ©ologiques ont Ă©tĂ© dĂ©terminĂ©es par ailleurs. Le degrĂ© dâoxydation du soufre, hĂ©tĂ©roatome mineur dans la fraction insoluble, a Ă©tĂ© mesurĂ© par micro-spectromĂ©trie SK-Xanes. La spectroscopie FT-IR a permis la description des structures fines des chaines carbonĂ©es et des fonctions riches en oxygĂšne, hĂ©tĂ©roatome majeur. La spectromĂ©trie de masse Ă trĂšs haute rĂ©solution Orbitrap a Ă©tĂ© utilisĂ©e pour dĂ©crire la diversitĂ© hĂ©tĂ©roatomique des molĂ©cules solubles de la chondrite Renazzo (CR2). Les chaines carbonĂ©es des chondrites de classe CI et Murchison se diffĂ©rencient de celle des autres mĂ©tĂ©orites par une abondance en groupements terminaux mĂ©thyles Ă la fois supĂ©rieure et invariable. Les chondrites de type 1 sont les seules porteuses de fonctions soufrĂ©es oxydĂ©es acides alors que la spĂ©ciation du soufre dans les chondrites de type 2 est invariable. De la mĂȘme façon, et cette fois pour lâensemble des chondrites Ă©tudiĂ©es, les groupements carbonyles sont majoritairement dans les fonctions cĂ©tones, en proportion indĂ©pendante du degrĂ© dâaltĂ©ration aqueuse. Tous les paramĂštres mesurĂ©s dans cette Ă©tude nous poussent Ă conclure que la variabilitĂ© molĂ©culaire au sein des chondrites carbonĂ©es de type 1 et 2 trouve moins son origine dans lâempreinte de lâhydrothermalisme que dans une hĂ©tĂ©rogĂ©nĂ©itĂ© du prĂ©curseur organique accrĂ©tĂ© par chaque corps parent. En particulier, nos mesures invalident lâhypothĂšse selon laquelle lâaltĂ©ration serait Ă lâorigine dâune conversion oxydative des chaines carbonĂ©es en fonctions acides carboxyliques
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