A fine mist of very small comet dust particles

AbstractAn international armada of spacecraft encountered Comet Halley in March 1986. The present article gives a brief overview of this unique event during which a cometary nucleus was seen as a spatially resolved object for the first time. It is a very dark body, the shape is irregular and the structure is inhomogeneous; only the sunward side is active. Many parent molecules were identified in the coma, including complicated hydrocarbons. There was also organic matter in the comet dust particles. Extensive studies were made of the complicated plasma environment of the comet.

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Cometary dust: the diversity of primitive refractory grains

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2016.0260 ◽

2017 ◽

Vol 375 (2097) ◽

pp. 20160260 ◽

Cited By ~ 21

Author(s):

D. H. Wooden ◽

H. A. Ishii ◽

M. E. Zolensky

Keyword(s):

Interplanetary Dust ◽

Dust Particles ◽

Refractory Materials ◽

Type Ii ◽

Interplanetary Dust Particles ◽

Aqueous Alteration ◽

Diverse Range ◽

Cometary Dust ◽

Refractory Organic Matter ◽

Comet Dust

Comet dust is primitive and shows significant diversity. Our knowledge of the properties of primitive cometary particles has expanded significantly through microscale investigations of cosmic dust samples (anhydrous interplanetary dust particles (IDPs), chondritic porous (CP) IDPs and UltraCarbonaceous Antarctic micrometeorites, Stardust and Rosetta ), as well as through remote sensing ( Spitzer IR spectroscopy). Comet dust are aggregate particles of materials unequilibrated at submicrometre scales. We discuss the properties and processes experienced by primitive matter in comets. Primitive particles exhibit a diverse range of: structure and typology; distribution of constituents; concentration and form of carbonaceous and refractory organic matter; Mg- and Fe-contents of the silicate minerals; sulfides; existence/abundance of type II chondrule fragments; high-temperature calcium–aluminium inclusions and ameboid-olivine aggregates; and rarely occurring Mg-carbonates and magnetite, whose explanation requires aqueous alteration on parent bodies. The properties of refractory materials imply there were disc processes that resulted in different comets having particular selections of primitive materials. The diversity of primitive particles has implications for the diversity of materials in the protoplanetary disc present at the time and in the region where the comets formed. This article is part of the themed issue ‘Cometary science after Rosetta’.

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Saturn's E, G and F rings: modulated by the plasma sheet

International Astronomical Union Colloquium ◽

10.1017/s0252921100101666 ◽

1984 ◽

Vol 75 ◽

pp. 597

Author(s):

E. Grün ◽

G.E. Morfill ◽

T.V. Johnson ◽

G.H. Schwehm

Keyword(s):

Solar Wind ◽

Direct Contact ◽

Transport Processes ◽

Time Variable ◽

Dust Particles ◽

Spatial Diffusion ◽

Drag Forces ◽

Orbit Perturbation ◽

Time Variations ◽

F Ring

ABSTRACTSaturn's broad E ring, the narrow G ring and the structured and apparently time variable F ring(s), contain many micron and sub-micron sized particles, which make up the “visible” component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. It is suggested that the extent of the E ring and the braided, kinky structure of certain portions of the F rings as well as possible time variations are a result of plasma induced electromagnetic perturbations and drag forces. The G ring, in this scenario, requires some form of shepherding and should be akin to the F ring in structure. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 102to 104years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

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Laboratory and in-situ analysis of comet dust

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102122 ◽

1988 ◽

Vol 46 ◽

pp. 8-9

Author(s):

D.E. Brownlee ◽

A.L. Albee

Keyword(s):

Electron Microscopy ◽

Solar System ◽

Laboratory Study ◽

Isotopic Analysis ◽

Building Blocks ◽

Sem Analysis ◽

Early Solar System ◽

Cometary Material ◽

Comet Dust

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.

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Analytical Electron Microscopy Characterization of Electric Arc Furnace Dust

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100097326 ◽

1981 ◽

Vol 39 ◽

pp. 134-135

Author(s):

J. R. Porter ◽

J. I. Goldstein ◽

D. B. Williams

Keyword(s):

Electron Microscopy ◽

Analytical Electron Microscopy ◽

Electric Arc Furnace ◽

Electric Arc ◽

Dust Particles ◽

Particle Analysis ◽

Arc Furnace ◽

Analytical Electron ◽

Residual Elements ◽

Industry Practice

Alloy scrap metal is increasingly being used in electric arc furnace (EAF) steelmaking and the alloying elements are also found in the resulting dust. A comprehensive characterization program of EAF dust has been undertaken in collaboration with the steel industry and AISI. Samples have been collected from the furnaces of 28 steel companies representing the broad spectrum of industry practice. The program aims to develop an understanding of the mechanisms of formation so that procedures to recover residual elements or recycle the dust can be established. The multi-phase, multi-component dust particles are amenable to individual particle analysis using modern analytical electron microscopy (AEM) methods.Particles are ultrasonically dispersed and subsequently supported on carbon coated formvar films on berylium grids for microscopy. The specimens require careful treatment to prevent agglomeration during preparation which occurs as a result of the combined effects of the fine particle size and particle magnetism. A number of approaches to inhibit agglomeration are currently being evaluated including dispersal in easily sublimable organic solids and size fractioning by centrifugation.

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Improving soil remediation through characterization

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138300 ◽

1995 ◽

Vol 53 ◽

pp. 386-387

Author(s):

E. C. Buck ◽

N. L. Dietz ◽

J. K. Bates

Keyword(s):

Dust Particles ◽

Radiochemical Analysis ◽

Solid Product ◽

Uranium Contamination ◽

Physical Separation ◽

X Ray ◽

Rocky Flats ◽

Remediation Strategies ◽

Bearing Materials ◽

X Ray Absorption

Operations at former weapons processing facilities in the U. S. have resulted in a large volume of radionuclidecontaminated soils and residues. In an effort to improve remediation strategies and meet environmental regulations, radionuclide-bearing particles in contaminant soils from Fernald in Ohio and the Rocky Flats Plant (RFP) in Colorado have been characterized by electron microscopy. The object of these studies was to determine the form of the contaminant radionuclide, so that it properties could be established [1]. Physical separation and radiochemical analysis determined that uranium contamination at Fernald was not present exclusively in any one size/density fraction [2]. The uranium-contamination resulted from aqueous and solid product spills, air-borne dust particles, and from the operation of an incinerator on site. At RFP the contamination was from the incineration of Pu-bearing materials. Further analysis by x-ray absorption spectroscopy indicated that the majority of the uranium was in the 6+ oxidation state [3].

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