Condensation processes in astrophysical environments: The composition and structure of cometary grains

Nuth, Joseph A.; Rietmeijer, Frans J. M.; Hill, H. G. M.

doi:10.1111/j.1945-5100.2002.tb00812.x

Cited by 86 publications

(68 citation statements)

References 42 publications

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“…Rietmeijer et al (1999) suggest that the observed growth occurs at metastable eutectic compositions and since MgO and FeO are completely miscible, there are no stable or metastable eutectic compositions along this axis of the phase diagram. This produces separate populations of magnesium silicate and iron silicate dust prior to aggregation and thermal processing of the aggregates (e.g., Nuth et al 2000Nuth et al , 2002. Formation of separate populations of magnesium silicate and iron silicate condensates from a mixed vapor may seem counterintuitive, but there is ample evidence to support this hypothesis in addition to the laboratory results cited above.…”

Section: Adding Iron and Magnesium To (Sio) N Nucleimentioning

confidence: 61%

A Model of Silicate Grain Nucleation and Growth in Circumstellar Outflows

Paquette

Ferguson

Nuth

2011

ApJ

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Based on its abundance, high bond energy, and recent measurements of its vapor pressure SiO is a natural candidate for dust nucleation in circumstellar outflows around asymptotic giant branch stars. In this paper, we describe a model of the nucleation and growth of silicate dust in such outflows. The sensitivity of the model to varying choices of poorly constrained chemical parameters is explored, and the merits of using scaled rather than classical nucleation theory are briefly considered. An elaboration of the model that includes magnesium and iron as growth species is then presented and discussed. The composition of the bulk of the grains derived from the model is consistent with olivines and pyroxenes, but somewhat metal-rich grains and very small, nearly pure SiO grains are also produced.

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Section: Adding Iron and Magnesium To (Sio) N Nucleimentioning

confidence: 61%

A Model of Silicate Grain Nucleation and Growth in Circumstellar Outflows

Paquette

Ferguson

Nuth

2011

ApJ

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“…Presently, a number of laboratories are conducting cosmic silicate and carbon dust analogues condensation experiments (e.g., Nuth et al, 2002;Fabian et al, 2000;Blanco et al, 1996) using similar but also different techniques than those reported in this paper. There are basically two different methods to generate the vapours in these experiments, viz.…”

Section: Introductionmentioning

confidence: 98%

Production, processing and characterization techniques for cosmic dust analogues

Rotundi

Brucato

Colangeli

et al. 2002

Meteorit & Planetary Scien

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Abstract-The laboratory analyses of cosmic dust analogues-that in the context ofthis paper include interstellar, circumstellar as well as cometary dust-have a critical role in the study of circumstellar and cometary dust. The morphological, structural and chemical characterization of these analogues are critical for comparisons oftheir infrared and ultraviolet spectra with those obtained by astronomical observations, as well as for modeling purposes. Besides, the results from these laboratory studies are important to the success of space missions to comets when testing and calibrating the payload instruments. The interpretations of returned scientific data would benefit from the comparison with data recorded by the instruments in a laboratory setting for different classes ofpreviously characterized analogues. We produced various types ofcondensed samples: (1) Mg,Fe-silicates, (olivine, pyroxene), (2) carbon-rich dust, and (3) mixed carbon-silicate dust. The samples were prepared using different techniques, viz. (1) laser bombardment of solid targets in an Ar and 02 atmosphere, (2) arc discharge in an Ar and H2 atmosphere, and (3) grinding powders of natural minerals. We simulated various post-condensation processes, such as thermal annealing, ultraviolet irradiation, ion bombardment and exposure to atomic hydrogen. These processes produced compound samples of a wide range of physico-chemical properties. To identify their textures, morphologies, grain compositions and crystallographic properties we used electron microscopy and far-ultraviolet to far-infrared (millimeter range) spectroscopy.

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“…Instead it will have a specific deep metastable eutectic composition. Most glass will be Mg-rich but there is no chemical constraint as DME dehydroxylate compositions can form in many chemical systems relevant to primitive dust compositions (Nuth et al 2000b(Nuth et al , 2002. I predict that when DME glass compositions in Stardust can be proven to be a recurring phenomenon, there is still a wealth of information on the smallest Wild 2 minerals hidden in these glasses.…”

Section: Discussionmentioning

confidence: 99%

Stardust glass: Indigenous and modified comet Wild 2 particles

Rietmeijer

2009

Meteorit & Planetary Scien

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There is no evidence among the collected comet dust for interstellar glass with embedded metals and sulfides. There is, however, ample evidence for melting of the smallest, sub-micrometer comet particles of nanometer-scale grains similar to those in the matrix of chondritic aggregate IDPs, including pyrrhotite. Massive patches of Mg-SiO, Al-SiO, or Ca-Si-O glass are incorporated in the familiar, vesicular Si-rich glass are melted Wild 2 silicates. Magnesiosilica glass has a deep metastable eutectic smectite-dehydroxylate composition. It indicates that very high temperatures well above the liquidus temperatures of forsterite were achieved very rapidly and were followed but ultrarapid quenching. This predictable and systematic response is not limited to Mg-silicates, and recognizing this phenomenon among massive glass will provide a means to complete the reconstruction of this comet's original minerals, as well as constrain the physiochemical environment created during aerogel melting and evaporation.

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Condensation processes in astrophysical environments: The composition and structure of cometary grains

Cited by 86 publications

References 42 publications

A Model of Silicate Grain Nucleation and Growth in Circumstellar Outflows

A Model of Silicate Grain Nucleation and Growth in Circumstellar Outflows

Production, processing and characterization techniques for cosmic dust analogues

Stardust glass: Indigenous and modified comet Wild 2 particles

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