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COSIMA calibration for the detection and characterisation of the cometary solid organic matter
Abstract
On the orbiter of the Rosetta spacecraft, the Cometary Secondary Ion Mass Analyser (COSIMA) will provide new in situ insights about the chemical composition of cometary grains all along 67 P/Churyumov-Gerasimenko (67 P/CG) journey until end of December 2015 nominally. The aim of this paper is to present the pre-calibration which has already been performed as well as the different methods which have been developed in order to facilitate the interpretation of the COSIMA mass spectra and more especially of their organic content. The first step was to establish a mass spectra library in positive and negative ion mode of targeted molecules and to determine the specific features of each compound and chemical family analysed. As the exact nature of the refractory cometary organic matter is nowadays unknown, this library is obviously not exhaustive. Therefore this library has also been the starting point for the research of indicators, which enable to highlight the presence of compounds containing specific atom or structure. These indicators correspond to the intensity ratio of specific peaks in the mass spectrum. They have allowed us to identify sample containing nitrogen atom, aliphatic chains or those containing polyaromatic hydrocarbons. From these indicators, a preliminary calibration line, from which the N/C ratio could be derived, has also been established. The research of specific mass difference could also be helpful to identify peaks related to quasi-molecular ions in an unknown mass spectrum. The BPSS (Bayesian Positive Source Separation) technique will also be very helpful for data analysis. This work is the starting point for the analysis of the cometary refractory organic matter. Nevertheless, calibration work will continue in order to reach the best possible interpretation of the COSIMA observations.
... In addition, in the positive-ion spectra from the particles, the C + peak is the most intense one of the series C + , CH + , CH 2 + , CH 3 + (see Fig. 1 and Extended Data Figs 2, 3). Such spectral characteristics are very different from those observed for the large range of organic molecules with well defined structures that were previously analysed by the COSIMA ground models 17 . These characteristics also indicate a rather low hydrogen/carbon ratio for the detected cometary organic material, in comparison with the ratio for the molecules studied for calibration purposes 17 . ...
... Such spectral characteristics are very different from those observed for the large range of organic molecules with well defined structures that were previously analysed by the COSIMA ground models 17 . These characteristics also indicate a rather low hydrogen/carbon ratio for the detected cometary organic material, in comparison with the ratio for the molecules studied for calibration purposes 17 . This result is in line with the most recent interpretations of spectra from the surface of 67P that were measured by the visible and infrared thermal imaging spectrometer (VIRTIS) 18 . ...
... Results from laboratory simulations 19 and from analyses of natural analogues such as carbonaceous chondrites 20,21 have indicated that the solid phase of cometary particles should contain a very large variety of organic molecules, ranging from the smallest molecules to high-molecular-weight organic matter. In preparation for the interpretation of mass spectra measured by COSIMA in space, calibration of the COSIMA reference models on Earth was performed on pure organic compounds from a variety of chemical families 17 While we report evidence of high-molecular-weight organic matter in the particles of 67P, there is no detection by COSIMA of smaller molecules that would be an equivalent to the soluble organic matter found in carbonaceous chondrites (for example, carboxylic acids, aliphatic or polycyclic aromatic hydrocarbons, and amino acids) 17 . Moreover, polyoxymethylene-which has been considered as a possible source of gaseous formaldehyde in cometary atmospheres 22 , and tentatively reported by the PTOLEMY instrument at the surface of the nucleus 23 -has not been detected so far in the particles analysed by COSIMA. ...
The presence of solid carbonaceous matter in cometary dust was established by the detection of elements such as carbon, hydrogen, oxygen and nitrogen in particles from comet 1P/Halley. Such matter is generally thought to have originated in the interstellar medium, but it might have formed in the solar nebula-the cloud of gas and dust that was left over after the Sun formed. This solid carbonaceous material cannot be observed from Earth, so it has eluded unambiguous characterization. Many gaseous organic molecules, however, have been observed; they come mostly from the sublimation of ices at the surface or in the subsurface of cometary nuclei. These ices could have been formed from material inherited from the interstellar medium that suffered little processing in the solar nebula. Here we report the in situ detection of solid organic matter in the dust particles emitted by comet 67P/Churyumov-Gerasimenko; the carbon in this organic material is bound in very large macromolecular compounds, analogous to the insoluble organic matter found in the carbonaceous chondrite meteorites. The organic matter in meteorites might have formed in the interstellar medium and/or the solar nebula, but was almost certainly modified in the meteorites' parent bodies. We conclude that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before and/or after being incorporated into the comet.
... The up-to-date observational data revealed limitations of the models which assume sphericity of dust grains. Indeed, the evidence of irregular shape of dust particles was revealed by the Stardust mission, by the IDPs (Interplanetary Dust Particles) analysis (Rotundi et al. 2007(Rotundi et al. , 2008 and by the measurements obtained by the Grain Impact Analyzer and Dust Accumulator (GI-ADA, Della Corte et al. 2014)) and Cometary Secondary Ion Mass Analyzer (COSIMA, (Le Roy et al. 2015)) for the Rosetta mission (Langevin et al. 2016;Fulle & Blum 2017;Ivanovski et al. 2017a). The images provided by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS, (Keller et al. 2007)) revealed indications of rotational motion of particles by the brightness variation in the tracks of single particles, interpreted as rotational motion of non-spherical particles (Fulle et al. 2015;Frattin et al. 2017). ...
In this work we aim to characterise the dust motion in the inner coma of comet 67P/Churyumov- Gerasimenko to provide constraints for theoretical 3D coma models. The OSIRIS camera onboard the Rosetta mission was able for the first time to acquire images of single dust particles from inside the cometary coma, very close to the nucleus. We analyse a large number of particles, performing a significant statistic of their behaviour during the post perihelion period, when the spacecraft covered distances from the nucleus ranging between 80 and 400 km. We describe the particle trajectories, investigating their orientation and finding highly radial motion with respect to the nucleus. Then, from the particle brightness profiles, we derive a particle rotational frequency of v < 3.6 Hz, revealing that they are slow rotators and do not undergo fragmentation. We use scattering models to compare the observed spectral radiance of the particles with the simulated ones in order to estimate their size, finding values that range from millimetres up to centimetres. The statistics performed in this paper provide useful parameters to constrain the cometary coma dynamical models.
... These close distances also facilitated the observation of the direct interaction of the solar wind with the nucleus, resulting in sputtering of dust [106], revealing the comet refractories to have similar Na abundances to carbonaceous chondrites, a depletion in Ca and an excess of K. We note that these Na values are not consistent with those of Schulz et al. [57], who report preliminary values of high Na abundances (more than IDPs and chondrites). There are known contamination issues with Na [107] but this abundance is reported to persist throughout the mission [108]. The first measurement of pick-up ions was reported at approximately 3.5 AU [109]. ...
The international Rosetta mission was launched in 2004 and consists of the orbiter spacecraft Rosetta and the lander Philae. The aim of the mission is to map the comet 67P/Churyumov–Gerasimenko by remote sensing, and to examine its environment in situ and its evolution in the inner Solar System. Rosetta was the first spacecraft to rendezvous with and orbit a comet, accompanying it as it passes through the inner Solar System, and to deploy a lander, Philae, and perform in situ science on the comet's surface. The primary goals of the mission were to: characterize the comet's nucleus; examine the chemical, mineralogical and isotopic composition of volatiles and refractories; examine the physical properties and interrelation of volatiles and refractories in a cometary nucleus; study the development of cometary activity and the processes in the surface layer of the nucleus and in the coma; detail the origin of comets, the relationship between cometary and interstellar material and the implications for the origin of the Solar System; and characterize asteroids 2867 Steins and 21 Lutetia. This paper presents a summary of mission operations and science, focusing on the Rosetta orbiter component of the mission during its comet phase, from early 2014 up to September 2016.
This article is part of the themed issue ‘Cometary science after Rosetta’.
... The samples studied in this presentation are listed in Table 2. Calibration experiments validating the measurements of organics are also described separately in Le Roy (2014). ...
We describe how to use multivariate analysis of complex TOF-SIMS (time-of-flight secondary ion mass spectrometry) spectra
by introducing the method of random projections. The technique allows us to do
full clustering and classification of the measured mass spectra. In this
paper we use the tool for classification purposes. The presentation describes
calibration experiments of 19 minerals on Ag and Au substrates using positive
mode ion spectra. The discrimination between individual minerals gives a
cross-validation Cohen κ for classification of typically about 80%.
We intend to use the method as a fast tool to deduce a qualitative similarity
of measurements.
... In the cometary environment, mass spectrometry seems to be the most suitable technique to detect complex organic molecules either in a gas or solid phase thank to the ROSINA and COSIMA instruments (Balsiger et al. 2007;Kissel et al. 2007). Concerning COSIMA, some calibrations have already been performed for HMT (Le Roy et al. 2015), and it could be interesting to conduct further similar studies on the PMI molecule. The search for these molecules could be used as a probe to estimate the thermal history of the grain incorporated in the cometary nuclei during their formation. ...
Interstellar ices are submitted to energetic processes (thermal, UV, and cosmic-ray radiations) producing complex organic molecules. Laboratory experiments aim to reproduce the evolution of interstellar ices to better understand the chemical changes leading to the reaction, formation, and desorption of molecules. In this context, the thermal evolution of an interstellar ice analogue composed of water, carbon dioxide, ammonia, and formaldehyde is investigated. The ice evolution during the warming has been monitored by IR spectroscopy. The formation of hexamethylenetetramine (HMT) and polymethylenimine (PMI) are observed in the organic refractory residue left after ice sublimation. A better understanding of this result is realized with the study of another ice mixture containing methylenimine (a precursor of HMT) with carbon dioxide and ammonia. It appears that carbamic acid, a reaction product of carbon dioxide and ammonia, plays the role of catalyst, allowing the reactions toward HMT and PMI formation. This is the first time that such complex organic molecules (HMT, PMI) are produced from the warming (without VUV photolysis or irradiation with energetic particles) of abundant molecules observed in interstellar ices (H2O, NH3, CO2, H2CO). This result strengthens the importance of thermal reactions in the ices' evolution. HMT and PMI, likely components of interstellar ices, should be searched for in the pristine objects of our solar system, such as comets and carbonaceous chondrites. © 2015. The American Astronomical Society. All rights reserved.
... For the purpose of this study we use data from the database covering the substrates and minerals as shown in Table 1. 10 The samples studied in this presentation are listed in Table 2. Calibration experiments valdiating the measurements of organics are also discribed separately in Leroy (2014). ...
We describe how to use multivariate analysis of complex TOF-SIMS
spectra introducing the method of random projections. The technique
allows us to do full clustering and classification of the measured
mass spectra. In this paper we use the tool for classification
purposes. The presentation describes calibration experiments of 19
minerals on Ag and Au substrates using positive mode ion
spectra. The discrimination between individual minerals gives
a crossvalidation Cohen κ for classification of typically
about 80%. We intend to use the method as a fast tool to deduce
a qualitative similarity of measurements.
The fluorescence colour and molecular signature of oil inclusions can provide precious information on the thermal maturity of inclusion oils and the fluid migration history of basins. Here we show how molecular mass spectrometric analyses in combination with fluorescence microscopy can be used to reveal heterogeneities in the chemical compositions of oil inclusions within a micrometer sized quartz crystal. We used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to extract and directly analyse the molecular content of two yellow and two white-blue fluorescing oil inclusions in a single quartz crystal from the Barrandian Basin (Czech Republic). The cyclic ion species detected primarily in the yellow fluorescing oil inclusions likely originate from steranes, hopanes, and other tricyclic and tetracyclic terpanes, whereas these are less abundant in the white-blue fluorescing oil inclusions. Depth profiles of the fluid inclusions indicate that the white-blue fluorescing oil inclusions are emptied faster in the ToF-SIMS instrument, presumably due to a higher content of more volatile components than in the yellow fluorescing oil inclusions. The phenanthrene to dibenzothiophene ratio derived from ToF-SIMS of the four inclusion oils from the Barrandian Basin indicates marine clastic sediments as the source rocks for all the inclusion oils. The phenanthrene to alkylphenanthrene ratio derived from ToF-SIMS indicates no major difference in thermal maturity of the oil in the white-blue and yellow fluorescing oil inclusions. Instead, variation in the chemical content of the trapped oil induced by trapping fractionation may be the key control.
In this work we aim to characterise the dust motion in the inner coma of comet 67P/Churyumov-Gerasimenko to provide constraints for theoretical 3D coma models. The OSIRIS camera on board the Rosetta mission was able for the first time to acquire images of single dust particles from inside the cometary coma, very close to the nucleus. We analyse a large number of particles, performing a significant statistic of their behaviour during the post perihelion period, when the spacecraft covered distances from the nucleus ranging between 80 and 400 km. We describe the particle trajectories, investigating their orientation and finding highly radial motion with respect to the nucleus. Then, from the particle brightness profiles, we derive a particle rotational frequency of ν < 3.6 Hz, revealing that they are slow rotators and do not undergo fragmentation. We use scattering models to compare the observed spectral radiance of the particles with the simulated ones in order to estimate their size, finding values that range from millimetres up to centimetres. The statistics performed in this paper provide useful parameters to constrain the cometary coma dynamical models.
Combustion of hydrocarbons produces both particulate- and gas-phase emissions responsible for major impacts on atmospheric chemistry and human health. Ascertaining the impact of these emissions, especially on human health, is not straightforward because of our relatively poor knowledge of how chemical compounds are partitioned between the particle and gas phases. Accordingly, we propose coupling a two-filter sampling method with a multi-technique analytical approach to fully characterize the particulate- and gas-phase compositions of combustion by-products. The two-filter sampling method is designed to retain particulate matter (elemental carbon possibly covered in a surface layer of adsorbed molecules) on a first quartz fiber filter while letting the gas phase pass through and then trap the most volatile components on a second black-carbon-covered filter. All samples thus collected are subsequently subjected to a multi-technique analytical protocol involving two-step laser mass spectrometry (L2MS), secondary ion mass spectrometry (SIMS), and micro-Raman spectroscopy. Using the combination of this two-filter sampling–multi-technique approach in conjunction with advanced statistical methods, we are able to unravel distinct surface chemical compositions of aerosols generated with different set points of a miniCAST burner. Specifically, we successfully discriminate samples by their volatile, semi-volatile, and non-volatile polycyclic aromatic hydrocarbon (PAH) contents and reveal how subtle changes in combustion parameters affect particle surface chemistry.
Most of the gaseous molecules that are detected in cometary atmospheres are produced through sublimation of nucleus ices. Distributed sources may also occur, that is, production within the coma, from the solid component of dust particles that are ejected from the nucleus. Glycine, the simplest amino acid, was observed episodically in the atmosphere of comet 67P/Churyumov-Gerasimenko (67P) by the ROSINA mass spectrometer on board the Rosetta probe. A series of measurements on 28 March 2015 revealed a distributed density profile at between 14 and 26 km away from the nucleus. We here present and discuss three study cases: (i) glycine emitted directly and only from the nucleus, (ii) glycine emitted from the sublimation of solid-state glycine on the dust particles that are ejected from the nucleus, and (iii) glycine molecules embedded in water ice that are emitted from the sublimation of this ice from the dust particles that are ejected from the nucleus. A numerical model was developed to calculate the abundance of glycine in the atmosphere of comet 67P as a function of the distance from the nucleus, and to derive its initial abundance in the lifted dust particles. We show that a good fit to the observations corresponds to a distributed source of glycine that is embedded in sublimating water ice from dust particles that are ejected from the nucleus (iii). The few hundred ppb of glycine embedded in water ice on dust particles (nominally 170 ppb by mass) agree well with the observed distribution.
Context. Because comets are part of the most primitive bodies of our solar system, establishing their chemical composition and comparing them to other astrophysical bodies gives new constraints on the formation and evolution of organic matter throughout the solar system. For two years, the time-of-flight secondary ion mass spectrometer COmetary Secondary Ion Mass Analyzer (COSIMA) on board the Rosetta orbiter performed in situ analyses of the dust particles ejected from comet 67P/Churyumov-Gerasimenko (67P).
Aims. The aim is to determine the H/C elemental ratio of the refractory organic component contained in cometary particles of 67P.
Methods. We analyzed terrestrial and extraterrestrial calibration samples using the COSIMA ground-reference model. Exploiting these calibration samples, we provide calibration lines in both positive and negative ion registration modes. Thus, we are now able to measure the cometary H/C elemental ratio.
Results. The mean H/C value is 1.04 ± 0.16 based on 33 different cometary particles. Consequently, the H/C atomic ratio is on average higher in cometary particles of 67P than in even the most primitive insoluble organic matter extracted from meteorites.
Conclusions. These results imply that the refractory organic matter detected in dust particles of 67P is less unsaturated than the material in meteorites.
Saturn's moon Enceladus harbours a global water ocean 1 , which lies under an ice crust and above a rocky core 2 . Through warm cracks in the crust 3 a cryo-volcanic plume ejects ice grains and vapour into space4-7 that contain materials originating from the ocean8,9. Hydrothermal activity is suspected to occur deep inside the porous core10-12, powered by tidal dissipation 13 . So far, only simple organic compounds with molecular masses mostly below 50 atomic mass units have been observed in plume material6,14,15. Here we report observations of emitted ice grains containing concentrated and complex macromolecular organic material with molecular masses above 200 atomic mass units. The data constrain the macromolecular structure of organics detected in the ice grains and suggest the presence of a thin organic-rich film on top of the oceanic water table, where organic nucleation cores generated by the bursting of bubbles allow the probing of Enceladus' organic inventory in enhanced concentrations.
Since the pioneering work of Emanuel Gil-Av and his associates at the Weizmann Institute of Science the direct gas chromatographic resolution of enantiomers has found its application in different fields of natural sciences, even expanding to space research and astrobiology. In these domains the resolution of chiral molecules of prebiotic relevance is of particular interest, since the determination of ratios between l- and d-enantiomers within non-terrestrial samples is assumed to shed light on the origin of biomolecular homochirality and the beginnings of life itself. According to an astrophysical scenario, the first molecular symmetry breaking event occurred upon irradiation of chiral organic molecules with circularly polarized light present in the interstellar medium. To examine this hypothesis, among others, chiral gas chromatographic stationary phases have been widely used to provide the differentiation of enantiomers in extracts of meteorites, samples of simulated interstellar ices and Mars soil analogues. Moreover several chiral capillary columns have been selected for in situ analyses of extraterrestrial organic matter by Mars missions and the cometary Rosetta mission. This review will highlight current advances of enantioselective gas chromatography applied to space science.
Since the pioneering work of Emanuel Gil-Av and his associates at the Weizmann Institute of Science the direct gas chromatographic resolution of enantiomers has found its application in different fields of natural sciences, even expanding to space research and astrobiology. In these domains the resolution of chiral molecules of prebiotic relevance is of particular interest, since the determination of ratios between l- and d-enantiomers within non-terrestrial samples is assumed to shed light on the origin of biomolecular homochirality and the beginnings of life itself. According to an astrophysical scenario, the first molecular symmetry breaking event occurred upon irradiation of chiral organic molecules with circularly polarized light present in the interstellar medium. To examine this hypothesis, among others, chiral gas chromatographic stationary phases have been widely used to provide the differentiation of enantiomers in extracts of meteorites, samples of simulated interstellar ices and Mars soil analogues. Moreover several chiral capillary columns have been selected for in situ analyses of extraterrestrial organic matter by Mars missions and the cometary Rosetta mission. This review will highlight current advances of enantioselective gas chromatography applied to space science.
The emerging consensus that comets carry the biochemical seeds of life coincides with the first step that was reached as early as 1977 in the historical development of the Hoyle-Wickramasinghe theory of cosmic life. To mark the centenary of the birth of Sir Fred Hoyle on 24 June 2015 this brief article retraces early developments that essentially heralded the new science of astrobiology.
ABSTRACT
The COmetary Secondary Ion Mass Analyser instrument on board ESA!s Rosetta mission has collected dust
particles in the coma of comet 67P/Churyumov–Gerasimenko. During the early-orbit phase of the Rosetta mission,
particles and particle agglomerates have been imaged and analyzed in the inner coma at distances between 100 km
and 10 km off the cometary nucleus and at more than 3 AU from the Sun. We identi!ed 585 particles of more than
14 !m in size. The particles are collected at low impact speeds and constitute a sample of the dust particles in the
inner coma impacting and fragmenting on the targets. The sizes of the particles range from 14 !m up to submillimeter
sizes and the differential dust "ux size distribution is !tted with a power law exponent of −3.1. After
impact, the larger particles tend to stick together, spread out or consist of single or a group of clumps, and the
"occulent morphology of the fragmented particles is revealed. The elemental composition of the dust particles is
heterogeneous and the particles could contain typical silicates like olivine and pyroxenes, as well as iron sul!des.
The sodium to iron elemental ratio is enriched with regard to abundances in CI carbonaceous chondrites by a factor
from !1.5 to !15. No clear evidence for organic matter has been identi!ed. The composition and morphology of
the collected dust particles appear to be similar to that of interplanetary dust particles.
Samples from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity’s
Sample Analysis at Mars instrument suite. H2O, SO2, CO2, and O2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H2O is bound within an amorphous component of the sample. Decomposition of fine-grained Fe or Mg carbonate is the likely source
of much of the evolved CO2. Evolved O2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound.
Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the
fines. Several simple organic compounds were detected, but they are not definitively martian in origin.
The composition of cometary ices provides key information on the chemical and physical proper- ties of the outer solar nebula where comets formed, 4.6 Gyr ago. This chapter summarizes our current knowledge of the volatile composition of cometary nuclei, based on spectroscopic observations and in situ measurements of parent molecules and noble gases in cometary comae. The processes that govern the excitation and emission of parent molecules in the radio, infrared (IR), and ultraviolet (UV) wavelength regions are reviewed. The techniques used to convert line or band fluxes into molecular production rates are described. More than two dozen parent molecules have been identified, and we describe how each is investigated. The spatial distribution of some of these molecules has been studied by in situ measure- ments, long-slit IR and UV spectroscopy, and millimeter wave mapping, including interferometry. The spatial distributions of CO, H CO, and OCS differ from that expected during direct sublimation from the nucleus, which suggests that these species are produced, at least partly, from extended sources in the coma. Abundance determinations for parent molecules are reviewed, and the evidence for chemical diversity among comets is discussed.
The Cassini-Huygens probe gas chromatograph mass spectrometer (GCMS) determined the composition of the Titan atmosphere from ∼140 km altitude to the surface. After landing, it returned composition data of gases evaporated from the surface. Height profiles of molecular nitrogen (N2), methane (CH4), and molecular hydrogen (H2) were determined. Traces were detected on the surface of evaporating methane, ethane (C2H6), acetylene (C2H2), cyanogen (C2N2), and carbon dioxide (CO2). The methane data showed evidence that methane precipitation occurred recently. The methane mole fraction was (1.48 ± 0.09) × 10−2 in the lower stratosphere (139.8–75.5 km) and (5.65 ± 0.18) × 10−2 near the surface (6.7 km to the surface). The molecular hydrogen mole fraction was (1.01 ± 0.16) × 10−3 in the atmosphere and (9.90 ± 0.17) × 10−4 on the surface. Isotope ratios were 167.7 ± 0.6 for 14N/15N in molecular nitrogen, 91.1 ± 1.4 for 12C/13C in methane, and (1.35 ± 0.30) × 10−4 for D/H in molecular hydrogen. The mole fractions of 36Ar and radiogenic 40Ar are (2.1 ± 0.8) × 10−7 and (3.39 ± 0.12) × 10−5, respectively. 22Ne has been tentatively identified at a mole fraction of (2.8 ± 2.1) × 10−7. Krypton and xenon were below the detection threshold of 1 × 10−8 mole fraction. Science data were not retrieved from the gas chromatograph subsystem as the abundance of the organic trace gases in the atmosphere and on the ground did not reach the detection threshold. Results previously published from the GCMS experiment are superseded by this publication.
New spectroscopic data obtained with the three-channel spectrometer of
Vega 2 show, after subtracting the dust-scattered solar continuum, that
a broad band emissive feature between 342 and 375 nm progressively
arises. Four bands at 347, 356, 364 and 374 nm can be identified in this
feature. The 1/p type intensity increase (p: projected distance between
nucleus and line of sight) shows that the molecules responsible for the
emission are most probably of the parent-type. A search for a molecule
emitting fluorescence bands between 342 and 375 nm showed that
phenanthrene was a possible candidate. A laser-induced fluorescence
experiment was conducted in the laboratory to record the dispersed
emission spectrum of phenanthrene under jet-cooled conditions. An
excellent agreement was obtained between the cometary and laboratory
spectra, for both the wavelength positions of the main peaks and their
relative intensities. Present observations are coherent with the
detection by IKS of an IR band at 3.28 nm assigned to an X-CH organic
compound. The identification of a polycylic aromatic hydrocarbon (PAH)
in Halley's comet emphasized the similarities between the material
released by comets and diffuse interstellar nebulae. It adds a strong
argument in favor of the fact that comets would be constituted of
interstellar material.
Our previous analysis of cometary samples returned to Earth by NASA's Stardust spacecraft showed several amines and amino acids, but the origin of these compounds could not be firmly established. Here, we present the stable carbon isotopic ratios of glycine and ε-amino-n-caproic acid (EACA), the two most abundant amino acids identified in Stardust-returned foil samples measured by gas chromatography–mass spectrometry coupled with isotope ratio mass spectrometry. The δ 13 C value for glycine of +29 ± 6‰ strongly suggests an extraterrestrial origin for glycine, while the δ 13 C value for EACA of −25 ± 2‰ indicates terrestrial contamination by Nylon-6 during curation. This represents the first detection of a cometary amino acid.
Abstract– To investigate the effect of parent body processes on the abundance, distribution, and enantiomeric composition of amino acids in carbonaceous chondrites, the water extracts from nine different powdered CI, CM, and CR carbonaceous chondrites were analyzed for amino acids by ultra performance liquid chromatography-fluorescence detection and time-of-flight mass spectrometry (UPLC-FD/ToF-MS). Four aqueously altered type 1 carbonaceous chondrites including Orgueil (CI1), Meteorite Hills (MET) 01070 (CM1), Scott Glacier (SCO) 06043 (CM1), and Grosvenor Mountains (GRO) 95577 (CR1) were analyzed using this technique for the first time. Analyses of these meteorites revealed low levels of two- to five-carbon acyclic amino alkanoic acids with concentrations ranging from approximately 1 to 2,700 parts-per-billion (ppb). The type 1 carbonaceous chondrites have a distinct distribution of the five-carbon (C5) amino acids with much higher relative abundances of the γ- and δ-amino acids compared to the type 2 and type 3 carbonaceous chondrites, which are dominated by α-amino acids. Much higher amino acid abundances were found in the CM2 chondrites Murchison, Lonewolf Nunataks (LON) 94102, and Lewis Cliffs (LEW) 90500, the CR2 Elephant Moraine (EET) 92042, and the CR3 Queen Alexandra Range (QUE) 99177. For example, α-aminoisobutyric acid (α-AIB) and isovaline were approximately 100 to 1000 times more abundant in the type 2 and 3 chondrites compared to the more aqueously altered type 1 chondrites. Most of the chiral amino acids identified in these meteorites were racemic, indicating an extraterrestrial abiotic origin. However, nonracemic isovaline was observed in the aqueously altered carbonaceous chondrites Murchison, Orgueil, SCO 06043, and GRO 95577 with l-isovaline excesses ranging from approximately 11 to 19%, whereas the most pristine, unaltered carbonaceous chondrites analyzed in this study had no detectable l-isovaline excesses. These results are consistent with the theory that aqueous alteration played an important role in amplification of small initial left handed isovaline excesses on the parent bodies.
The ESA mission Rosetta, launched on March 2nd, 2004, carries an instrument suite to the comet 67P/Churyumov-Gerasimenko.
The COmetary Secondary Ion Mass Anaylzer – COSIMA – is one of three cometary dust analyzing instruments onboard Rosetta. COSIMA
is based on the analytic measurement method of secondary ion mass spectrometry (SIMS). The experiment’s goal is in-situ analysis
of the elemental composition (and isotopic composition of key elements) of cometary grains. The chemical characterization
will include the main organic components, present homologous and functional groups, as well as the mineralogical and petrographical
classification of the inorganic phases. All this analysis is closely related to the chemistry and history of the early solar
system. COSIMA covers a mass range from 1 to 3500 amu with a mass resolution m/Δm @ 50% of 2000 at mass 100 amu. Cometary dust is collected on special, metal covered, targets, which are handled by a target
manipulation unit. Once exposed to the cometary dust environment, the collected dust grains are located on the target by a
microscopic camera. A pulsed primary indium ion beam (among other entities) releases secondary ions from the dust grains.
These ions, either positive or negative, are selected and accelerated by electrical fields and travel a well-defined distance
through a drift tube and an ion reflector. A microsphere plate with dedicated amplifier is used to detect the ions. The arrival
times of the ions are digitized, and the mass spectra of the secondary ions are calculated from these time-of-flight spectra.
Through the instrument commissioning, COSIMA took the very first SIMS spectra of the targets in space. COSIMA will be the
first instrument applying the SIMS technique in-situ to cometary grain analysis as Rosetta approaches the comet 67P/Churyumov-Gerasimenko,
after a long journey of 10 years, in 2014.
This is the second of five books in the Amino Acids, Peptides and Proteins in Organic Synthesis series. Closing a gap in the literature, this is the only series to cover this important topic in organic and biochemistry. Drawing upon the combined expertise of the international "who's who" in amino acid research, these volumes represent a real benchmark for amino acid chemistry, providing a comprehensive discussion of the occurrence, uses and applications of amino acids and, by extension, their polymeric forms, peptides and proteins. The practical value of each volume is heightened by the inclusion of experimental procedures.
Using visual observations that were reported 140 years ago in the Comptes Rendus de l'Academie des Sciences de Paris, we have determined the atmospheric trajectory and the orbit of the Orgueil meteorite, which fell May 14, 1864, near Montauban, France. Despite the intrinsic uncertainty of visual observations, we were able to calculate a reasonably precise atmospheric trajectory and a moderately precise orbit for the Orgueil meteoroid. The atmosphere entry point was similar to 70 km high and the meteoroid terminal point was similar to 20 km high. The calculated luminous path was similar to 150 km with an entry angle of 20 degrees. These characteristics are broadly similar to that of other meteorites for which the trajectory is known. Five out of six orbital parameters for the Orgueil orbit are well constrained. In particular, the perihelion lies inside the Earth's orbit (q similar to 0.87 AU), as is expected for an Earth-crossing meteorite, and the orbital plane is close to the ecliptic (i similar to 0 degrees). The aphelion distance (Q) depends critically on the pre-atmospheric velocity. From the calculated atmospheric path and the fireball duration, which was reported by seven witnesses, we have estimated the pre-atmospheric velocity to be larger than 17.8 km/sec, which corresponds to an aphelion distance Q larger than 5.2 AU, the semi-major axis of Jupiter orbit. These results suggest that Orgueil has an orbit similar to that of Jupiter-family comets (JFCs), although an Halley-type comet cannot be excluded. This is at odds with other meteorites that have an asteroidal origin, but it is compatible with 140 years of data-gathering that has established the very special nature of Orgueil compared to other meteorites. A cometary origin of the Orgueil meteorite does not contradict cosmochemistry data on CII chondrites. If CII chondrites originate from comets, it implies that comets are much more processed than previously thought and should contain secondary minerals. The forthcoming return of cometary samples by the Stardust mission will provide a unique opportunity to corroborate (or contradict) our hypothesis.
The determination of the chemical composition of solid cometary dust particles was one of the prime objectives of the three missions to Comet Halley in 1986. The dust analysis was performed by time-of-flight mass-spectrometry. Within the experimental uncertainty the mean abundances of the rock-forming elements in cometary dust particles are comparable to their abundances in CI-chondrites and in the solar photosphere, i.e. they are cosmic. H, C, and N, on the other hand, in cometary dust are significantly more abundant than in CI-chondrites, approach solar abundances, are to some extent related to O, and reside in an omnipresent refractory organic component dubbed CHON. Element variations between individual dust grains are characterized by correlations of Mg, Si, and O, and to a lesser extent of Fe and S. From particle-to-particle variations of the rock forming elements information on the mineralogy of cometary dust can be obtained. Cluster analysis revealed certain groups that partly match the classifications of stratospheric interplanetary dust particles. About half of Halley's analyzed particles are characterized by anhydrous Fe-poor Mg-silicates, Fe-sulfides, and rarely Fe metal. The Fe-poor Mg-silicates link Halley's dust to that of Hale-Bopp as shown by recent IR observations. No significant deviation from normal of the isotopic composition of the elements is unequivocally present with the notable exception carbon: ^12C-rich grains with ^12C/^13C-ratios up to ≈ 5,000 link cometary dust to presolar circumstellar grains identified in certain chondrites.
Cometary nuclei consist of ices intermixed with dust grains and are thought to be the least modified solar system bodies remaining from the time of planetary formation. Flyby missions to Comet P/Halley in 1986 showed that cometary dust is extremely rich in organics (∼50% by mass). However, this proportion appears to be variable among different comets. In comparison with the CI-chondritic abundances, the volatile elements H, C, and N are enriched in cometary dust indicating that cometary solid material is more primitive than CI-chondrites. Relative to dust in dense molecular clouds, bulk cometary dust preserves the abundances of C and N, but exhibits depletions in O and H. In most cases, the carbonaceous component of cometary particles can be characterized as a multi-component mixture of carbon phases and organic compounds. Cluster analysis identified a few basic types of compounds, such as elemental carbon, hydrocarbons, polymers of carbon suboxide and of cyanopolyynes. In smaller amounts, polymers of formaldehyde, of hydrogen cyanide and various unsaturated nitriles also are present. These compositionally simple types, probably, are essential "building blocks", which in various combinations give rise to the variety of involatile cometary organics.
H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired
by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition
of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing
species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously
analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone;
however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.
One important component of refractory organic residues synthesized from
interstellar/cometary ice analogues is hexamethylenetetramine (HMT,
C6H12N4). However, HMT has never been
observed in any astrophysical or planetary environment so far. We
investigated thermal evolution of HMT above ambient temperature. The
synthesis of the organic residue (ice deposition, photolysis and
warming) as well as its heating to temperatures higher than 300 K are
performed by means of the same experimental apparatus. The later also
allows in situ continuous monitoring of both the solid organic residue
(by FTIR spectrometry) and of the gas species (by mass spectrometry).
H₂O, CO₂, SO₂, O₂, H₂, H₂S, HCl, chlorinated hydrocarbons, NO and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H₂O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO₂. Concurrent evolution of O₂ and chlorinated hydrocarbons suggest the presence of oxychlorine phase(s). Sulfides are likely sources for S-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic C sources may be preserved in the mudstone; however, the C source for the chlorinated hydrocarbons is not definitively of martian origin.
H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggest the presence of oxychlorine phase(s). Sulfides are likely sources for S-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic C sources may be preserved in the mudstone; however, the C source for the chlorinated hydrocarbons is not definitively of martian origin.
The presence of polyoxymethylene (POM) in cometary grains has been debated years ago. Although never proven, its presence can not be excluded. Rosetta, the ESA mission to comet 67P/Churyumov–Gerasimenko, may answer this question. On board the spacecraft, COSIMA (COmetary Secondary Ion Mass Analyzer) will analyze the grains ejected from the nucleus using a Time Of Flight Secondary Ion Mass Spectrometer (TOF-SIMS). In this paper we report the extent to which COSIMA will be able to detect POM if this compound is present on cometary grains. We have analyzed two kinds of POM polymers with a laboratory model of COSIMA. Positive mass spectra display alternating sequence of peaks with a separation of 30.011 Da between 1 and 600 Da related to formaldehyde and its oligomers but also to the fragmentation of these oligomers. The separation of 30.011 Da of numbers peaks, corresponding to the fragmentation into H2CO is characteristic of POM and we show that it could be highlight by mathematical treatment. POM lifetime on COSIMA targets have also been studied as POM is thermally instable. It can be concluded that the cometary grains analysis have to be planned not too long after their collection in order to maximize the chances to detect POM. This work was supported by the Centre National d'Etudes Spatiales (CNES).
The current Solar System architecture is a heritage of the protoplanetary disk that surrounded the young Sun, 4.56 Gy ago. Primitive extraterrestrial objects provide means to trace back the primordial composition and radial distribution of matter in this disk. Here, we present a combined micro-IR, Raman, chemical and isotopic study of two ultracarbonaceous micrometeorites recovered from Antarctica (UCAMMs). This study reveals particles containing an unusually high nitrogen- and deuterium-rich organic matter analogous to a polyaromatic hydrogenated carbon nitride, characterized by nitrogen concentration with bulk atomic N/C ratios of 0.05 and 0.12 (locally exceeding 0.15). We propose that such nitrogen-rich carbonaceous material can be formed by energetic irradiations of nitrogen-rich ices in very low temperature regions of the Solar System. Such conditions are encountered at the surface of small objects beyond the trans-neptunian region. UCAMMs provide unique insights on physico-chemical processes that occurred beyond the nitrogen snow-line, revealing organic material from the extreme outer regions of the Solar System that cannot be investigated by remote sensing methods.
Studying the chemical composition of organic matter in astrophysical environments is an important means to improve our understanding of its origin and evolution. This organic matter evolves from molecular clouds to protoplanetary disks, and as a final destination, takes part in the formation of many objects of our solar system, such as primitive chondritic material, planetesimals and finally planets. In this contribution, we perform experimental simulations based on the VUV irradiation and warming-up of primitive interstellar ice analogs (CH3OH:NH3:H2O), and characterize, for the first time, the resulting refractory residue, using very high resolution mass spectrometry (VHRMS) with an LTQ-orbitrap-XL instrument. An electrospray source allows ionizing all the molecules having proton donor or acceptor chemical functions, while limiting as much as possible their damages. Thus, this method provides the analysis of the whole ionizable molecules making up the residue. The analysis of the spectra shows that these residues contain a large number of molecules formed of CHNO elements, including macromolecular entities beyond 4000 Da. The average elemental composition of the residue is of H/C = 1.5, N/C = 0.4, O/C = 0.4. These first results are tentatively compared to VHRMS analyses of the soluble organic matter (SOM) present in the Murchison’s meteorite, a primitive chondrite of the CM class. The molecular richness observed can be considered as the “first step” of the complex abiotic organic matter in extraterrestrial media. This initial matter, that may be rather universal, could then evolve toward more processed materials in parent bodies, such as comets and asteroids, materials that are then observed and subsequently analyzed in meteorites found on Earth. In addition to providing some insight on the mixture complexity, VHRMS allows for the search of specific molecules. For instance, hexamethylenetetramine (HMT) and some of its derivatives are identified in these residues. With the possibility to characterize the whole residue as well as some specific molecules, we consider that VHRMS is a powerful analytical tool for the understanding of the chemical evolution of organic matter in astrophysical environments.
A model for pristine comet composition is derived on the basis of aggregated interstellar dust. The chemical and physical constituents of the precomet dust are derived by observing the evolution of clouds of dust and molecules into the molecular cloud phase and extrapolating theoretically to the ultimate composition of the dust. The observational characteristics of the dust are interpreted by a combination of theory with the results of laboratory simulation of the photochemical evolution of interstellar dust materials. Laboratory measures of the infrared absorption of mixtures containing H2O ice provide a key step in predicting that approximately 27% by volume of comets is in the form of amorphous H2O ice. The laboratory results also predict that approximately 21% of comets consists of complex nonvolatile organic molecules of prebiotic type. Predictions based on the aggregated interstellar dust comet model are consistent as of 1981 with many key observational properties of comets.
The determination of the chemical composition of solid cometary dust particles was one of the prime objectives of the three missions to Comet Halley in 1986. The dust analysis was performed by time-of-flight mass-spectrometry. Within the experimental uncertainty the mean abundances of the rock-forming elements in cometary dust particles are comparable to their abundances in CI-chondrites and in the solar photosphere, i.e. they are cosmic. H, C, and N, on the other hand, in cometary dust are significantly more abundant than in CI-chondrites, approach solar abundances, are to some extent related to O, and reside in an omnipresent refractory organic component dubbed CHON. Element variations between individual dust grains are characterized by correlations of Mg, Si, and O, and to a lesser extent of Fe and S. From particle-to-particle variations of the rock forming elements information on the mineralogy of cometary dust can be obtained. Cluster analysis revealed certain groups that partly match the classifications of stratospheric interplanetary dust particles. About half of Halley's analyzed particles are characterized by anhydrous Fe-poor Mg-silicates, Fe-sulfides, and rarely Fe metal. The Fe-poor Mg-silicates link Halley's dust to that of Hale-Bopp as shown by recent IR observations. No significant deviation from normal of the isotopic composition of the elements is unequivocally present with the notable exception carbon: 12C-rich grains with 12C/13C-ratios up to ≈ 5,000 link cometary dust to presolar circumstellar grains identified in certain chondrites.
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to study submonolayers of organic compounds of environmental significance adsorbed on coal flyash particles. Through the use of mass-resolved secondary ion images and mass spectra, chemical information on single particles was obtained. For example, TOF-SIMS was capable of distinguishing particles which had higher levels of adsorbed polycyclic organic matter (POM). For flyash particles coated with submonolayer coverages of benzo[e]pyrene, the carbonaceous fraction of these particles had much higher coverages of the adsorbate than did particles from the mineral fraction. TOF-SIMS was also used to monitor reactions such as the photooxidation of benz[a]anthracene on individual particle surfaces. Benz[a]anthracene-7, 12-dione was formed during the initial 15 min of photolysis and gradually decayed with increased photolysis time.
The major organic component of carbonaceous chondrites is a solvent-insoluble, high molecular weight macromolecular material that constitutes at least 70% of the total organic content in these meteorites. Analytical pyrolysis is often used to thermally decompose macromolecular organic matter in an inert atmosphere into lower molecular weight fragments that are more amenable to conventional organic analytical techniques. Hydropyrolysis refers to pyrolysis assisted by high hydrogen gas pressures and a dispersed catalytically-active molybdenum sulfide phase. Hydropyrolysis of meteorites has not been attempted previ- ously although it is ideally suited to such studies due to its relatively high yields. Hydropyrolysis of the Murchison macromolecular material successfully releases significant amounts of high molecular weight PAH including phenanthrene, carbazole, fluoranthene, pyrene, chrysene, perylene, benzoperylene and coronene units with varying degrees of alklyation. Analysis of both the products and residue from hydropyrolysis reveals that the meteoritic organic network contains both labile (pyrolysable) and refractory (nonpyrolysable) fractions. Comparisons of hydropyrolysis yields of Murchison macromolecular materials with those from terrestrial coals indicate that the refractory component probably consists of a network dominated by at least five- or six-ring PAH units cross-linked together. Copyright © 2004 Elsevier Ltd
Cometary nuclei consist of ices intermixed with dust grains and are thought to be the least modified solar system bodies remaining
from the time of planetary formation. Flyby missions to Comet P/Halley in 1986 showed that cometary dust is extremely rich
in organics (∼50% by mass). However, this proportion appears to be variable among different comets. In comparison with the
CI-chondritic abundances, the volatile elements H, C, and N are enriched in cometary dust indicating that cometary solid material
is more primitive than CI-chondrites. Relative to dust in dense molecular clouds, bulk cometary dust preserves the abundances
of C and N, but exhibits depletions in O and H. In most cases, the carbonaceous component of cometary particles can be characterized
as a multi-component mixture of carbon phases and organic compounds. Cluster analysis identified a few basic types of compounds,
such as elemental carbon, hydrocarbons, polymers of carbon suboxide and of cyanopolyynes. In smaller amounts, polymers of
formaldehyde, of hydrogen cyanide and various unsaturated nitriles also are present. These compositionally simple types, probably,
are essential "building blocks", which in various combinations give rise to the variety of involatile cometary organics.
Emission spectra of comet P/Halley in the 275–710nm wavelength range were obtained using a spectrometer mounted on the Vega 2 spacecraft, which encountered the comet on March 9, 1986. The spectra, after the removal of the dust-scattered solar continuum, show the presence of a broad-band emissive feature between 340 and 390nm with three peaks at 371, 376 and 382nm. Near the nucleus, the intensity increase illustrates that the molecules responsible for the emission are most likely of the parent type. Our cometary spectra were compared with UV laboratory spectra of polycyclic aromatic hydrocarbons having 4 benzenoid rings. A laser-induced fluorescence experiment conducted in the laboratory recorded the dispersed emission spectrum of pyrene under jet-cooled conditions. Moreels et al. (Astron. Astrophys. 284 (1994) 643) demonstrated that phenanthrene was a possible candidate for the four bands at 347, 356, 364 and 374nm.The comparison between the cometary and laboratory spectra suggests the possible presence of another PAH, probably pyrene, in Halley's comet. This new suggestion illustrates the link between cometary and interstellar matter. These observations are coherent with the detection of the cometary IR band at 3.28μm assigned to an X–CH organic compound.
This paper is a review dealing with the organic chemistry of comets. It describes how the chemical composition of comets can provide information about the chemistry of the interstellar medium, and the formation of the solar system. We discuss to what extent they could have brought to Earth the ingredients essential to the emergence of life: water and prebiotic compounds. We review all molecules which have been detected or tentatively detected in comets by remote sensing or in-situ observations, inputs of theoretical models, and all other organic species expected to be present from the results of experimental simulations. This compilation yields a list of more than a hundred molecules which can be used as a reference for the preparation of experiments developed for the Rosetta and Deep Space 4 cometary missions. We point out that further experiments are necessary to investigate the connections between the solid and gaseous phases of comets, especially studying the photodegradation of high molecular weight compounds which could be present in the nuclei.
A 1-g interior sample of the Murchison CII meteorite was examined for the presence of purines and pyrimidines by dual-column ion-exclusion chromatography and ultraviolet spectroscopy. Xanthine, not previously reported in meteorites, was found to be the major purine liberated by extraction with formic acid, with a concentration corresponding to 2.3 micrograms per gram of meteorite. Guanine (0.1 ppm) and hypoxanthine (0.04 ppm) were also tentatively identified. The presence of adenine could not be confirmed. No pyrimidines were detected at concentrations higher than the background level (0.01 ppm) in water, formic acid, or strong acid extracts. Silylation of the water extract, however, resulted in the appearance of 4-hydroxypyrimidine, 4-hydroxy-2-methylpyrimidine, and 4-hydroxy-6-methylpyrimidine. These compounds are thought to be formed during the silylation procedure from contaminants present in the reagent.
Poly(ethylene terephthalate)(PET) and polystyrene (PS) have been studied using static secondary ion mass spectrometry (SSIMS). A triple quadrupole analyser has been employed to investigate secondary ion fragmentation and formation mechanisms. Daughter spectra and neutral loss spectra were obtained and fragmentation patterns were deduced. Comparison of the fragmentation data obtained in the gas-phase collisionally activated dissociation (CAD) experiments with the SSIMS data suggested that ion formation probabilities during CAD were similar to ion formation probabilities at the solid surface during low-flux sputtering. It was concluded that low-energy gas-phase CAD processes model effectively the processes which lead to fragmentation of the polymer during low-flux sputtering.
Part 1 Static secondary ion mass spectrometry for surface chemical characterization: the SIMS phenomenon the experimental parameters the SIMS experiment experimental procedures used in acquisition of spectra. Part 2 Library of spectra. Part 3 Case studies: static SIMS in surface science cleaning of semiconductor materials SIMS imaging of the mechanism of oxide growth the use of MS/MS techniques in materials analysis SIMS imaging of semiconductor devices. (Part contents).
Edited by the people who were forerunners in creating the field, together with contributions from 34 leading international experts, this handbook provides the definitive reference on Blind Source Separation, giving a broad and comprehensive description of all the core principles and methods, numerical algorithms and major applications in the fields of telecommunications, biomedical engineering and audio, acoustic and speech processing. Going beyond a machine learning perspective, the book reflects recent results in signal processing and numerical analysis, and includes topics such as optimization criteria, mathematical tools, the design of numerical algorithms, convolutive mixtures, and time frequency approaches. This Handbook is an ideal reference for university researchers, R&D engineers and graduates wishing to learn the core principles, methods, algorithms, and applications of Blind Source Separation. Covers the principles and major techniques and methods in one bookEdited by the pioneers in the field with contributions from 34 of the world's expertsDescribes the main existing numerical algorithms and gives practical advice on their designCovers the latest cutting edge topics: second order methods; algebraic identification of under-determined mixtures, time-frequency methods, Bayesian approaches, blind identification under non negativity approaches, semi-blind methods for communicationsShows the applications of the methods to key application areas such as telecommunications, biomedical engineering, speech, acoustic, audio and music processing, while also giving a general method for developing applications
Synchrotron-based soft X-ray micro-analysis was performed on particles extracted from the Stardust aerogel collector in order to obtain detailed organic functional group information on any organic solids captured as part of the Principal Examination suite of analyses for samples from comet 81P/Wild 2. It is observed that cometary organic carbon captured in aerogel is present in a number of different manifestations and often intimately associated with silicates. Carbon X-ray absorption near edge structure (XANES) spectra reveal considerable chemical complexity in all of the organic particles studied so far. Universally, the comet 81P/Wild 2 organic particles contain low concentrations of aromatic and/or olefinic carbon relative to aliphatic and heteroatom-containing functional groups, e.g., amide, carboxyl, and alcohol/ethers. N-XANES confirms the presence and assignments of these functional groups. In general, the XANES data record considerable chemical complexity across the range of organic samples currently analyzed. The atomic ratios, N/C and O/C, derived from XANES data reveal a wide range in heteroatom content; in all cases these elemental ratios are higher than that of primitive meteoritic organic matter. The wide range in chemistry, both in elemental abundances and specific organic functional groups, suggests that the comet 81P/Wild 2 organic solids may have multiple origins.
We demonstrate that the ion probe technique of time of flight-secondary ion mass spectrometry (ToF-SIMS) is capable of identifying purified organic compounds in situ and could augment GC-MS analysis on small geological samples. ToF-SIMS has been applied to a number of purified organic compounds including polycyclic aromatic hydrocarbons, nitrogen-containing heterocyclics, n-alkanes and isoprenoids. It is found that ToF-SIMS allows detection of individual poly- and heterocyclic aromatic hydrocarbons from the presence of their molecular (or near molecular) ions. The identification of individual methylated and non-methylated aliphatic hydrocarbons has proven more difficult, as a molecular ion is not always produced. All cyclic and some aliphatic compounds could be identified, even in complex mixtures.
Caution must be taken in interpreting measurements of organics in Stardust samples. In particular, as noted in Sandford et
al. and reinforced in the comment by Spencer and Zare, one component of Stardust organics, the low-mass polycyclic aromatic
hydrocarbons seen diffusely along track surfaces, should be treated cautiously because they may be due to impact conversion
of aerogel carbon.
Infrared spectra in the 3-5 micron region have been obtained of Comet
Halley after perihelion, at heliocentric distances of 1.6 and 2.0 AU. A
broad emission feature, peaking near 3.4 microns and containing some
spectral substructure, was observed, while at longer wavelengths only a
featureless blackbody emission spectrum was seen. The emission feature
probably arises from UV-pumped infrared fluorescence of organic
molecules which are either in the gas phase or are embedded in very
small grains. In the former interpretation the molecules must be quite
large. These results lend support to the idea that comets formed out of
interstellar grains whose molecular ice mantles largely consist of
nonvolatile complex organic molecules.
Data extracted so far on the dust composition from the PIA and PUMA
experiments on board Giotto and Vega 1 and 2 are reviewed. It is found
that Halley's dust is composed of two end-member components: a
refractory organic phase (CHON) and a Mg-rich silicate phase. The CHON
component is argued to be coating silicate cores. The refractory
organics are highly unsaturated polycondensates rich in C=C and C-O
compounds. The CHON elements are more abundant than in CI chondrites.
The abundances of C and O approach the solar system abundances, N is
intermediate between the solar and CI-chondrite abundances, and H is
much closer to the CI-chondrite abundance than to the solar one. Within
a factor of two, the abundances of the rock-forming elements are the
same as in the whole solar system. The variations of the elements Mg,
Si, and Fe, as well as the enrichment of volatile elements (relative to
CI chondrites), provide a link between Halley's dust and interplanetary
dust particles, especially the anhydrous variety.
Using a nuclear microprobe, we measured the carbon and nitrogen
concentrations and distributions in several interplanetary dust
particles (IDPs) and Antarctic micrometeorites (MMs), and compared them
to 2 carbonaceous chondrites: Tagish Lake and Murchison. We observed
that IDPs are richest in both elements. All the MMs studied contain
carbon, and all but the coarse-grained and 1 melted MM contained
nitrogen. We also observed a correlation in the distribution of carbon
and nitrogen, suggesting that they may be held in an organic material.
The implications for astrobiology of these results are discussed, as
small extraterrestrial particles could have contributed to the origin of
life on Earth by delivering important quantities of these 2 bio-elements
to the Earth's surface and their gas counterparts, CO2 and N2, to the
early atmosphere.
Cometary nuclei contain the least modified material from the formative epoch of our planetary system, and their compositions reflect a range of processes experienced by material prior to its incorporation in the cometary nucleus. Dynamical models suggest that icy bodies in the main cometary reservoirs (Kuiper Belt, Oort Cloud) formed in a range of environments in the protoplanetary disk, and (for the Oort Cloud) even in disks surrounding neighboring stars of the Sun's birth cluster. Photometric and spectroscopic surveys of more than 100 comets have enabled taxonomic groupings based on free radical species and on crystallinity of rocky grains. Since 1985, new surveys have provided emerging taxonomies based on the abundance ratios of primary volatiles. More than 20 primary chemical species are now detected in bright comets. Measurements of nuclear spin ratios (in water, ammonia, and methane) and of isotopic ratios (D/H in water and HCN; 14N/15N in CN and HCN) have provided critical insights on factors affec...
Previous analyses of carbonaceous chondrites have demonstrated the presence of the biologically significant purines adenine, guanine, hypoxanthine and xanthine1–3. To date, however, no pyrimidine of biological importance has been reported. An earlier report4 of a fraction extracted from the Murray meteorite showing ‘cytosine-like’ spectral characteristics was later shown to be due to an artefact of the analytical method5,6. Some unusual pyrimidines which have no known biological function were reported in extracts from the Murchison, Murray and Orgueil carbonaceous chondrites7. However, these results have not been replicated and are now thought to have been due to artefacts2,3. Because of the reported synthesis of the pyrimidines uracil, thymine and cytosine in Fischer-Tropsch-type reactions8,9 and the suggestion that such reactions may have been of significance in the production of organic material in meteorites9,10, we have reinvestigated the possible occurrence of pyrimidines in extracts from the Murchison, Murray and Orgueil carbonaceous meteorites using specific fractionation techniques and high-sensitivity analysis. The pyrimidines uracil, thymine and cytosine, together with the purines adenine and guanine are, of course, the building blocks of terrestrial genetic inheritance. Therefore their presence or absence in meteorites is also of considerable interest to theories of chemical evolution and the origin of life. We report here the positive identification of uracil in water and formic acid extracts of all three meteorites.
The problems of computing, storing, and retrieving precise masses of the many combinations of elements likely to occur in the mass spectra of organic compounds are considerable. They can be significantly reduced by the adoption of a mass scale in which the mass of the CH2 radical is taken as 14.0000 mass units. The advantage of this scale is that ions differing by one or more CH2 groups have the same mass defect. The precise masses of a series of alkyl naphthalene parent peaks, for example, are 127.9195, 141.9195, 155.9195, etc. Because of the identical mass defects, the similar origin of these peaks is recognizable without reference to tables of masses. Tables of the mass defects for combinations of H, C12, C13, N, O, S32, and S34 are presented.
Abstract– We report a multi-wavelength Raman spectroscopy study of carbonaceous matter in 38 Antarctic micrometeorites (AMMs) from the 2006 CONCORDIA collection. The particles were selected as a function of their degree of thermal alteration developed during the deceleration in the atmosphere. These samples range from unmelted (fine-grained—Fg; ultracarbonaceous—UCAMMs) to partially melted AMMs (scorias—Sc) and completely melted particles (cosmic spherules—CS). More than half of the analyzed AMMs contain a substantial amount of polyaromatic carbonaceous matter with a high degree of disorder. The proportion of particles where carbon is not detected increase from the Fg to the Fg-Sc and to the Sc-AMMs, and no carbon is detected in CS. In addition, the spectral characteristics of the G and D bands of the carbonaceous matter in Sc-AMMs plot apart from the trend formed by the data from Fg-AMMs and UCAMMs. These results suggest that oxidation processes occurred during the deceleration of the particles in the atmosphere. In Fg-AMMs and UCAMMs, the spectral characteristics of the G and D bands reveal the high degree of disorder of the carbonaceous matter, precluding a long duration thermal metamorphism on the parent body and suggesting that AMMs have a connection with C1–C2 chondrites. The Raman parameters of the deuterium-rich carbonaceous matter of UCAMMs do not differ from that of Fg-AMMs. Using a 244 nm excitation, we detected the cyanide (–CN) functional group for the first time in a UCAMM, reinforcing the likely cometary origin of this type of micrometeorites.
A model is presented in which electron impact (EI)/electronic excitation plays a pivotal role in the formation of secondary ions in the SIMS experiment, especially those originating from discrete molecular species. Positive ions are formed by electron loss whereas negative ions are formed by electron capture. Collisions of the new ions with the surface and with other species directly above the sample, along with metastable decay events, reduce the number of odd electron ions detected and produce the changes that make SIMS spectra so different from EI mass spectra. Primary support for this model is gathered from static SIMS spectra themselves, which can be rationalized to a large degree by assuming that the same rearrangement and fragmentation mechanisms that are invoked to explain EI mass spectra take place at the surface after kiloelectron-volt ion impacts. The static secondary ion spectra of a variety of simple discrete molecular species, of simple hydrocarbons, of monofunctional organic species and of more complicated multifunctional organic species are analyzed in this way and the utility of this model is demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.
IntroductionISMCometsMeteoritesMicrometeorites and IDPsMarsDelivery of Extraterrestrial Amino Acid to the Earth and its Importance to the Origin of LifeConclusions
References
Secondary ion mass spectra (SIMS) and 252Cf plasma desorption ionization mass spectra (PDMS) of two carboxylic acids and two purine nucleobases have been compared. Results demonstrate that the positive ion mass spectra as well as the negative ion mass spectra are very similar in SIMS and PDMS. The principal characteristics are formation of quasimolecular ions (M + H)+ or (M−H)− and loss of small molecules producing nonradical fragment ions; fumaric acid exhibits a remarkable formation of radical cations and anions. A set of simplified rules has been formulated for typical ion production processes involved in these techniques. This work contributes to the development of methods for data interpretation applicable to in situ analyses of cometary grains during the ROSETTA space mission of European Space Agency to the comet 46p/Wirtanen.
Thin films of hydrocarbon molecules, unsaturated fatty acid and low molecular weight polystyrene deposited on different metal substrates (silver, copper and gold) were bombarded by 15 keV Ga ions and the secondary ions were mass-and energy-analysed by means of a time-of-flight secondary ion mass spectrometer. The samples were studied in order to evidence the effects of different substrates and coverages on the emission of the parent and cationised molecular ions, and to gain a better understanding of the large molecular ion emission processes. Ion beam degradation studies were realised for fundamental purposes too. In general, the kinetic energy distributions of metal-cationised molecules are broad in comparison with those of the parent ions, and of the smaller polystyrene fingerprint ions. In addition, the velocity distributions of the parent ions and of the metal-cationised molecules are similar. Parent ions of aromatic molecules are, on average, more energetic than those of aliphatic molecules. In the case of metal-cationised molecules, the three hypotheses of emission of a preformed complex, recombination in the selvedge and metastable decay of larger aggregates are critically reviewed in comparison with the experimental data. The recombination hypothesis cannot account for the whole set of observations. On the other hand, the very different evolutions of the parent ions and of the metal-cationised molecules in the degradation experiments cannot be explained solely in the frame of metastable decay reactions, although the kinetic energy measurements show that a significant fraction of the parent-like ions are produced in the vacuum. The augmentation of the secondary ion kinetic energy with increasing molecule size for triacontane monomers and dimers, and for silver-cationised polystyrene oligomers, is in disagreement with the sputtering by a single cascade atom, too. Finally, the discussion outlines the conditions that must be satisfied to model the experimental observations and proposes a view of the sputtering of these large molecular cations based on multiple collision processes and possible subsequent dissociation in the vacuum. © 1998 Published by Elsevier Science B.V. All rights reserved.
Abstract– Carbonaceous matter in Stardust samples returned from comet 81P/Wild 2 is observed to contain a wide variety of organic functional chemistry. However, some of this chemical variety may be due to contamination or alteration during particle capture in aerogel. We investigated six carbonaceous Stardust samples that had been previously analyzed and six new samples from Stardust Track 80 using correlated transmission electron microscopy (TEM), X-ray absorption near-edge structure spectroscopy (XANES), and secondary ion mass spectroscopy (SIMS). TEM revealed that samples from Track 35 containing abundant aliphatic XANES signatures were predominantly composed of cometary organic matter infilling densified silica aerogel. Aliphatic organic matter from Track 16 was also observed to be soluble in the epoxy embedding medium. The nitrogen-rich samples in this study (from Track 22 and Track 80) both contained metal oxide nanoparticles, and are likely contaminants. Only two types of cometary organic matter appear to be relatively unaltered during particle capture. These are (1) polyaromatic carbonyl-containing organic matter, similar to that observed in insoluble organic matter (IOM) from primitive meteorites, interplanetary dust particles (IDPs), and in other carbonaceous Stardust samples, and (2) highly aromatic refractory organic matter, which primarily constitutes nanoglobule-like features. Anomalous isotopic compositions in some of these samples also confirm their cometary heritage. There also appears to be a significant labile aliphatic component of Wild 2 organic matter, but this material could not be clearly distinguished from carbonaceous contaminants known to be present in the Stardust aerogel collector.
Abstract— We have analyzed Shişr 033, a CR chondrite from the Omani desert, using several different analytical techniques designed to study the degree of terrestrial alteration of this meteorite and also its petrologic classification. Bulk chemical analyses (including organic carbon and mean total H2O content) are consistent with a CR classification. Additionally, oxygen isotope analysis on a bulk sample indicates that Shişr 033 is of type CR2. Amino acid analysis using liquid chromatography with UV fluorescence detection (HPLC-FD) and liquid chromatography-time of flight-mass spectrometry (LC-ToF-MS) show that the absolute and the relative amino acid content of Shişr 033 is distinct from other carbonaceous chondrites. Oxygen isotope analysis of a phyllosilicate-rich dark inclusion shows that this inclusion is closer to CV3 or CO3 chondrites. The effects of terrestrial weathering in Shişr 033 are evident from the dark inclusion carbon isotopic data, bulk chemistry (through the elevated concentrations of Sr and Ba), and amino acid data, which suggests extensive amino acid contamination of the meteorite from the fall site soil. Nevertheless, Shişr 033 contains a small fraction of indigenous components, as indicated by the presence of the extraterrestrial amino acid α-aminoisobutyric acid (AIB) that was not detected in the Shişr soils. Finally, the terrestrial age of Shişr 033 was determined and is discussed in the context of high levels of contamination.
Abstract— Using visual observations that were reported 140 years ago in the Comptes Rendus de l'Académie des Sciences de Paris, we have determined the atmospheric trajectory and the orbit of the Orgueil meteorite, which fell May 14, 1864, near Montauban, France. Despite the intrinsic uncertainty of visual observations, we were able to calculate a reasonably precise atmospheric trajectory and a moderately precise orbit for the Orgueil meteoroid. The atmosphere entry point was ˜70 km high and the meteoroid terminal point was ˜20 km high. The calculated luminous path was ˜150 km with an entry angle of 20°. These characteristics are broadly similar to that of other meteorites for which the trajectory is known. Five out of six orbital parameters for the Orgueil orbit are well constrained. In particular, the perihelion lies inside the Earth's orbit (q ˜0.87 AU), as is expected for an Earth-crossing meteorite, and the orbital plane is close to the ecliptic (i ˜0°). The aphelion distance (Q) depends critically on the pre-atmospheric velocity. From the calculated atmospheric path and the fireball duration, which was reported by seven witnesses, we have estimated the pre-atmospheric velocity to be larger than 17.8 km/sec, which corresponds to an aphelion distance Q larger than 5.2 AU, the semi-major axis of Jupiter orbit. These results suggest that Orgueil has an orbit similar to that of Jupiter-family comets (JFCs), although an Halley-type comet cannot be excluded. This is at odds with other meteorites that have an asteroidal origin, but it is compatible with 140 years of data-gathering that has established the very special nature of Orgueil compared to other meteorites. A cometary origin of the Orgueil meteorite does not contradict cosmochemistry data on CI1 chondrites. If CI1 chondrites originate from comets, it implies that comets are much more processed than previously thought and should contain secondary minerals. The forthcoming return of cometary samples by the Stardust mission will provide a unique opportunity to corroborate (or contradict) our hypothesis.
Abstract– Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si-CH3 groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.
Abstract— Micrometeorites (MMs) are extraterrestrial particles ranging in size from 25 μm to 2 mm that survive atmospheric entry and are collected on the Earth's surface. They represent the largest mass flux (MF) of extraterrestrial material (30,000 ± 20,000 t/yr) to the present-day Earth. Studies of large collections of MMs suggest that about 20% have not been heated to high temperatures and that they contain organic carbon. Since non-protein amino acids have been found in some carbonaceous meteorites, they might also be found in unmelted MMs. However, previous searches for amino acids in MMs were inconclusive. We combined a new extraction method for amino acids with a highly sensitive analytical method to detect and quantitate amino acids in MMs collected at the South Pole. We found the non-protein amino acid -amino isobutyric acid (AIB) in one of our samples. The non-detection of this amino acid in the other samples analyzed suggests that there are amino acid-containing and amino acid-free MMs, with ˜14% of the MMs containing AIB. Since the MF of MMs is much higher than that of carbonaceous chondrites (CMs), amino acids in these small particles would represent an important source of exogenous delivery of organic molecules. Therefore, the results are discussed on the basis of their implications for astrobiology.
Many organic compounds or their precursorsfound in meteorites originated in the interstellar or circumstellarmedium and were later incorporated intoplanetesimals during the formation of thesolar system. There they either survivedintact or underwent further processing tosynthesize secondary products on themeteorite parent body.The most distinct feature of CI and CM carbonaceouschondrites, two typesof stony meteorites, is their high carbon content(up to 3% of weight), either in theform of carbonates or of organic compounds. The bulkof the organic carbon consistsof an insoluble macromolecular material with a complexstructure. Also present is asoluble organic fraction, which has been analyzedby several separation and analyticalprocedures. Low detection limits can be achievedby derivatization of the organicmolecules with reagents that allow for analysisby gas chromatography/massspectroscopy and high performance liquidchromatography. The CM meteoriteMurchison has been found to contain more than70 extraterrestrial amino acids andseveral other classes of compounds includingcarboxylic acids, hydroxy carboxylicacids, sulphonic and phosphonic acids, aliphatic,aromatic and polar hydrocarbons,fullerenes, heterocycles as well as carbonylcompounds, alcohols, amines and amides.The organic matter was found to be enriched indeuterium, and distinct organiccompounds show isotopic enrichments of carbon andnitrogen relative to terrestrialmatter.