C o M e C S - Project
Comet and Meteorite Materials - Studied by Chemometrics of Spectroscopic Data
COSIMA on Rosetta: Selected relevant publications
Last change 170105 [ CoMeCS Start
Compiled by Kurt Varmuza
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MNRAS 462, S323–S330 (2016) - Monthly Notices of the Royal Astronomical Society
This paper reviews the current knowledge on the composition of cometary dust (ice, minerals and organics) in order to constrain their origin and formation mechanisms. Comets have been investigated by astronomical observations, space missions (Giotto to Rosetta), and by the analysis of cometary dust particles collected on Earth, chondritic porous interplanetary dust particles (CP-IDPs) and ultracarbonaceous Antarctic micrometeorites (UCAMMs).
Most ices detected in the dense phases of the interstellar medium (ISM) have been identified in cometary volatiles. However, differences also suggest that cometary ices cannot be completely inherited from the ISM.
Cometary minerals are dominated by crystalline Mg-rich silicates, Fe sulphides and glassy phases including GEMS (glass with embedded metals and sulphides). The crystalline nature and refractory composition of a significant fraction of the minerals in comets imply a high temperature formation/processing close to the proto-Sun, resetting a possible presolar signature of these phases. These minerals were further transported up to the external regions of the disc and incorporated in comet nuclei. Cometary matter contains a low abundance of isotopically anomalous minerals directly inherited from the presolar cloud.
At least two different kinds of organic matter are found in dust of cometary origin, with low or high nitrogen content. N-poor organic matter is also observed in primitive interplanetary materials (like carbonaceous chondrites) and its origin is debated. The N-rich organic matter is only observed in CP-IDPs and UCAMMs and can be formed by Galactic cosmic ray irradiation of N2- and CH4-rich icy surface at large heliocentric distance beyond a ‘nitrogen snow line’.
Key words: comets: general – interplanetary medium –meteorites, meteors, meteoroids – minor planets, asteroids: general – ISM: abundances – dust, extinction.
Planetary and Space Science 133 (2016 ) 63–75
Soon after the arrival of the ROSETTA spacecraft at Comet 67/PChuryumov-Gerasimenko the on board instrument COSIMA (“Cometary Secondary Ion Mass Analyzer”) collected a large number of cometary dust particles on targets from gold black of thickness between 10 and 30 μm.
Inspection by its camera subsystem revealed that many of them consist of smaller units of typically some tens of micrometers in size. The collection process left the smaller dust particles in an essentially unaltered state where as most particles larger than about 100 μm got fragmented into smaller pieces.
Using the observed fragment size distributions, the present paper includes a first assessment of the strength for those dust particles that were disrupted upon impact.
M. Hilchenbach, J. Kissel, Y. Langevin, C. Briois, H. von Hoerner, A. Koch, R. Schulz, J. Silén, K. Altwegg, L. Colangeli, H. Cottin, C. Engrand, H. Fischer, A. Glasmachers, E. Grün, G. Haerendel, H. Henkel, H. Höfner, K. Hornung, E.K. Jessberger, H. Lehto, K. Lehto, F. Raulin, L. Le Roy, J. Rynö, W. Steiger, T. Stephan, L. Thirkell, R. Thomas, K. Torkar, K. Varmuza, K.P. Wanczek, N. Altobelli, D. Baklouti, A. Bardyn, N. Fray, H. Krüger, N. Ligier, Z. Lin, P. Martin, S. Merouane, F.R. Orthous-Daunay, J. Paquette, C. Revillet, S. Siljeström, O. Stenzel, B. Zaprudin:
The Astrophysical Journal Letters, 816:L32 (2016)
Comet 67P/Churyumov–Gerasimenko: Close-up on dust particle fragments.
Nicolas Fray, Anaďs Bardyn, Hervé Cottin, Kathrin Altwegg, Donia Baklouti, Christelle Briois, Luigi Colangeli, Cécile Engrand, Henning Fischer, Albrecht Glasmachers, Eberhard Grün, Gerhard Haerendel, Hartmut Henkel, Herwig Höfner, Klaus Hornung, Elmar K. Jessberger, Andreas Koch, Harald Krüger, Yves Langevin, Harry Lehto, Kirsi Lehto, Léna Le Roy, Sihane Merouane, Paola Modica, François-Régis Orthous-Daunay, John Paquette, François Raulin, Jouni Rynö, Rita Schulz, Johan Silén, Sandra Siljeström, Wolfgang Steiger, Oliver Stenzel, Thomas Stephan, Laurent Thirkell, Roger Thomas, Klaus Torkar, Kurt Varmuza, Karl-Peter Wanczek, Boris Zaprudin, Jochen Kissel, Martin Hilchenbach:
Nature 528, 72-74 (2016). doi:10.1038/nature19320
High-molecular-weight organic matter in the particles of comet 67P/Churyumov-Gerasimenko.
Icarus 271 (2016) 76–97
The COSIMA mass spectrometer on board the ROSETTA orbiter has collected dust in the near coma of comet 67P/Churyumov-Gerasimenko since August 11, 2014. The collected dust particles are identified by taking images with a microscope (COSISCOPE) under grazing incidence illumination before and after exposure of the target to cometary dust. More than 10,000 dust particles >14μm in size collected from August 11, 2014 to April 3, 2015 have been detected on three distinct target assemblies, including ∼500 dust particles with sizes ranging from 50 to more than 500μm, that can be resolved by COSISCOPE (pixel size 14μm). During this period, the heliocentric distance decreased from 3.5AU to less than 2AU.
The collection efficiency on targets covered with “metal black” has been very high, due to the low relative velocity of incoming dust. Therefore, the COSISCOPE observations provide the first optical characterization of an unbiased sample of particles collected in the inner coma of a comet. The typology of particles >100μm in size is dominated by clusters with a wide range of structure and strength, most originating from the disruption of large aggregates (>1mm in size) shortly before collection. A generic relationship between these clusters and IDPs/Antarctic meteorites is likely in the framework of accretion models. About 15% of particles larger than 100μm are compact particles with two likely contributions, one being linked to clusters and another leaving the cometary nucleus as single compact particles.
Rita Schulz, Martin Hilchenbach, Yves Langevin, Jochen Kissel, Johan Silen, Christelle Briois, Cecile Engrand, Klaus Hornung, Donia Baklouti, Anaiıs Bardyn, Hervé Cottin, Henning Fischer, Nicolas Fray, Marie Godard, Harry Lehto, Léna Le Roy, Sihane Merouane, François-Régis Orthous-Daunay, John Paquette, Jouni Rynö, Sandra Siljeström, Oliver Stenzel, Laurent Thirkell, Kurt Varmuza, Boris Zaprudin:
Nature 518, 216-218 (2015)
Comet 67P/Churyumov-Gerasimenko sheds dust coat accumulated over the past four years.
Silén, J., Cottin, H., Hilchenbach, M., Kissel, J., Lehto, H., Siljeström, S., Varmuza, K.:
Geosci. Instrum. Method. Data Syst., 4, 45-56 (2015). DOI:10.5194/gi-4-45-2015.
COSIMA data analysis using multivariate techniques.
Planetary and Space Science 105 (2015) 1–25
On the orbiter of the Rosetta space craft, the Cometary Secondary Ion Mass Analyser (COSIMA) will provide new in situ insights about the chemical composition of cometary grains all along 67P/ Churyumov–Gerasimenko (67P/CG ) journey until the 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 analyzed. 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 Bayesian Positive Source Separation (BPSS) 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.
Geosci. Instrum. Method. Data Syst., 4, 139–148, 2015
We describe the use of Bayesian analysis methods applied to time-of-flight secondary ion mass spectrometer (TOF-SIMS) spectra. The method is applied to the COmetary Secondary Ion Mass Analyzer (COSIMA) TOF-SIMS mass spectra where the analysis can be broken into subgroups of lines close to integer mass values. The effects of the instrumental dead time are discussed in a new way.
The method finds the joint probability density functions of measured line parameters (number of lines, and their widths, peak amplitudes, integrated amplitudes and positions). In the case of two or more lines, these distributions can take complex forms. The derived line parameters can be used to further calibrate the mass scaling of TOF-SIMS and to feed the results into other analysis methods such as multivariate analyses of spectra.
We intend to use the method, first as a comprehensive tool to perform quantitative analysis of spectra, and second as a fast tool for studying interesting targets for obtaining additional TOF-SIMS measurements of the sample, a property unique to COSIMA. Finally, we point out that the Bayesian method can be thought of as a means to solve inverse problems but with forward calculations, only with no iterative corrections or other manipulation of the observed data.
Planetary and Space Science 117 (2015) 35–44
COmetary Secondary Ion Mass Analyzer (COSIMA) is a time-of-flight secondary ion mass spectrometry (TOF-SIMS) instrument on board the Rosetta space mission. COSIMA has been designed to measure the composition of cometary dust particles. It has a mass resolution m/Δm of 1400 at mass100u, 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 demon strated 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 particles.
Varmuza K., Filzmoser P., Hilchenbach M., Krüger H., Silén J.:
Chemom. Intell. Lab. Syst., 138, 64-71 (2014). DOI: http://dx.doi.org/10.1016/j.chemolab.2014.07.011
KNN classification - evaluated by repeated double cross validation: Recognition of minerals relevant for comet dust.
Planetary and Space Science 103 (2014) 309–317
After a brief review of the instrument development and materials selection for collecting cometary dust in the vicinity of comet 67/PChuryumov–Gerasimenko we focus on laboratory verification for the capability of metal black targets to decelerate and capture dust particles (velocities in the order of 100m/s; sizes of some10 μm). The results indicate that particles between 10 and 100 μm size can be collected with high probability. Two basic mechanisms of energy dissipation upon impact could be identified: By internal friction within a highly structured dust and within the black’s nanostructure. In addition to the actual ROSETTA mission the data presented here might have a more general relevance for future, similar in-situ investigations.
Kissel J., Altwegg K., Briois C., Clark B.C., Colangeli L., Cottin H., Czempiel S., Eibl J., Engrand C., Fehringer H.M., Feuerbacher B., Fischer H., Fomenkova M., Glasmachers A., Greenberg J.M., Grün E., Haerendel G., Henkel H., Hilchenbach M., von Hoerner H., Höfner H., Hornung K., Jessberger E.K., Koch A., Krüger H., Langevin Y., Martin P., Parigger P., Raulin F., Rüdenauer F., Rynö J., Schmid E.R., Schulz R., Silén J., Steiger W., Stephan T., Thirkell L., Thomas R., Torkar K., Utterback N.G., Varmuza K., Wanczek K.P., Werther W., Zscheeg H.:
In Schulz R., Alexander C., Boehnhardt H., Glassmeier K.H. (editors): ROSETTA: ESA's mission to the origin of the solar system, p. 201-242, Springer, New York (2009)
COSIMA: High resolution time-of-flight secondary ion mass spectrometer for the analysis of cometary dust particles onboard ROSETTA.