scholarly journals Cometary dust: the diversity of primitive refractory grains

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160260 ◽  
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’.

scholarly journals Dust of comet 67P/Churyumov-Gerasimenko collected by Rosetta/MIDAS: classification and extension to the nanometer scale

2019 ◽  
Vol 630 ◽  
pp. A26 ◽  
Author(s):  
T. Mannel ◽  
M. S. Bentley ◽  
P. D. Boakes ◽  
H. Jeszenszky ◽  
P. Ehrenfreund ◽  
...  
Keyword(s):  
Interplanetary Dust ◽  
Dust Particles ◽  
Nanometer Scale ◽  
Early Solar System ◽  
Interplanetary Dust Particles ◽  
Surface Features ◽  
Cometary Dust ◽  
Log Normal ◽  
Resolution Of Imaging ◽  
Comet 67P

Context. The properties of the smallest subunits of cometary dust contain information on their origin and clues to the formation of planetesimals and planets. Compared to interplanetary dust particles or particles collected during the Stardust mission, dust collected in the coma of comet 67P/Churyumov-Gerasimenko (67P) during the Rosetta mission provides a resource of minimally altered material with known origin whose structural properties can be used to further the investigation of the early solar system. Aims. The cometary dust particle morphologies found at comet 67P on the micrometer scale are classified, and their structural analysis is extended to the nanometer scale. Methods. We present a novel method for achieving the highest spatial resolution of imaging obtained with the MIDAS Atomic Force Microscope on board Rosetta. 3D topographic images with resolutions down to 8 nm were analyzed to determine the subunit sizes of particles on the nanometer scale. Results. Three morphological classes can be determined: (i) fragile agglomerate particles of sizes larger than about 10 μm comprised of micrometer-sized subunits that may themselves be aggregates and show a moderate packing density on the surface of the particles. (ii) A fragile agglomerate with a size of about a few tens of micrometers comprised of micrometer-sized subunits that are suggested to be aggregates themselves and are arranged in a structure with a fractal dimension lower than two. (iii) Small micrometer-sized particles comprised of subunits in the size range of hundreds of nanometers that show surface features that are again suggested to represent subunits. Their differential size distributions follow a log-normal distribution with means of about 100 nm and standard deviations between 20 and 35 nm. Conclusions. The properties of the dust particles found by MIDAS represent an extension of the dust results of Rosetta to the micro- and nanometer scale. All micrometer-sized particles are hierarchical dust agglomerates of smaller subunits. The arrangement, appearance, and size distribution of the smallest determined surface features are reminiscent of those found in chondritic porous interplanetary dust particles. They represent the smallest directly detected subunits of comet 67P.

scholarly journals Synthesis of the morphological description of cometary dust at comet 67P/Churyumov-Gerasimenko

2019 ◽  
Vol 630 ◽  
pp. A24 ◽  
Author(s):  
C. Güttler ◽  
T. Mannel ◽  
A. Rotundi ◽  
S. Merouane ◽  
M. Fulle ◽  
...  
Keyword(s):  
Interplanetary Dust ◽  
Dust Particles ◽  
Morphological Description ◽  
Complex Data ◽  
Particle Structure ◽  
Interplanetary Dust Particles ◽  
Data Set ◽  
Cometary Dust ◽  
Common Framework ◽  
Comet 67P

Before Rosetta, the space missions Giotto and Stardust shaped our view on cometary dust, supported by plentiful data from Earth based observations and interplanetary dust particles collected in the Earth’s atmosphere. The Rosetta mission at comet 67P/Churyumov-Gerasimenko was equipped with a multitude of instruments designed to study cometary dust. While an abundant amount of data was presented in several individual papers, many focused on a dedicated measurement or topic. Different instruments, methods, and data sources provide different measurement parameters and potentially introduce different biases. This can be an advantage if the complementary aspect of such a complex data set can be exploited. However, it also poses a challenge in the comparison of results in the first place. The aim of this work therefore is to summarize dust results from Rosetta and before. We establish a simple classification as a common framework for intercomparison. This classification is based on the dust particle structure, porosity, and strength and also on its size. Depending on the instrumentation, these are not direct measurement parameters, but we chose them because they were the most reliable for deriving our model. The proposed classification has proved helpful in the Rosetta dust community, and we offer it here also for a broader context. In this manner, we hope to better identify synergies between different instruments and methods in the future.

scholarly journals Scattering, absorption, and thermal emission by large cometary dust particles: Synoptic numerical solution

2019 ◽  
Vol 631 ◽  
pp. A164 ◽  
Author(s):  
Johannes Markkanen ◽  
Jessica Agarwal
Keyword(s):  
Light Scattering ◽  
Numerical Solution ◽  
Electromagnetic Waves ◽  
Random Media ◽  
Thermal Emission ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Conductive Heat ◽  
Interplanetary Dust Particles ◽  
Cometary Dust

Context. Remote light scattering and thermal infrared observations provide clues about the physical properties of cometary and interplanetary dust particles. Identifying these properties will lead to a better understanding of the formation and evolution of the Solar System. Aims. We present a numerical solution for the radiative and conductive heat transport in a random particulate medium enclosed by an arbitrarily shaped surface. The method will be applied to study thermal properties of cometary dust particles. Methods. The recently introduced incoherent Monte Carlo radiative transfer method developed for scattering, absorption, and propagation of electromagnetic waves in dense discrete random media is extended for radiative heat transfer and thermal emission. The solution is coupled with the conductive Fourier transport equation that is solved with the finite-element method. Results. The proposed method allows the synoptic analysis of light scattering and thermal emission by large cometary dust particles consisting of submicrometer-sized grains. In particular, we show that these particles can sustain significant temperature gradients resulting in the superheating factor phase function observed for the coma of comet 67P/Churyumov–Gerasimenko.

scholarly journals Tholins and their relevance for astrophysical issues

2008 ◽  
Vol 4 (S251) ◽  
pp. 409-416 ◽  
Author(s):  
E. Quirico ◽  
C. Szopa ◽  
G. Cernogora ◽  
V. Lees ◽  
S. Derenne ◽  
...  
Keyword(s):  
Analytical Techniques ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Chemical Information ◽  
Interstellar Space ◽  
Interplanetary Dust Particles ◽  
Absorption Bands ◽  
Visible Absorption ◽  
Organic Solids ◽  
Cometary Dust

AbstractTholins are polymeric hydrogenated carbon nitrides formed from N2:CH4 mixtures exposed to electrical discharges. They are complex disordered solids, and their structural chemistry and formation processes are not yet fully understood. Tholins have been widely adopted as useful analogs of reddish organic solids associated with planetary bodies or in interstellar space (e.g., Titan's aerosols, reddish surfaces of outer objects, interstellar organics, etc.) for fitting astronomical observations. However, there has been little evidence to date that they in fact constitute pertinent model materials, i. e. with chemical structure/composition similar to those presumed to be present in planetary or interstellar organic solids. In this contribution, we first review recent advances made regarding the determination of composition and structure of tholins produced in the laboratory. They point to a high chemical selectivity in the range of functional groups present, the control of unsaturation by nitrogen, and the highly disordered character of the structures. In a second section, we discuss the relationship between chemistry and the optical properties of tholins, and we point out the lack of a unique relationship between the shape and strength of the visible absorption bands and the chemical composition or structure of the model tholins. The tholins exhibit similarities with HCN “polymers”, that are suspected to be present in cometary refractory dust. This points to the existence of possible similar polymerisation processes, and it suggests they could also be used as analogs of N-rich cometary organics. Laboratory-based studies of cometary dust might offer new insights on the “chemical relevancy” of tholins, as combined micro-analytical techniques will allow direct comparison of chemical information between the materials produced. In a third section we present recent results pertaining to the search for such compounds in cometary grains (Stardust grains, interplanetary dust particles - IDPs). We show that some N-rich spots in stratospheric IDPs are rich in cyanide species, but no tholin-like compounds or polymeric HCN have been detected to date.

A comparison between polarimetric properties of cometary dust and interplanetary dust particles

Icarus ◽  
1990 ◽  
Vol 86 (1) ◽  
pp. 264-272 ◽  
Author(s):  
A.C. Levasseur-regourd ◽  
R. Dumont ◽  
J.B. Renard
Keyword(s):  
Interplanetary Dust ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Cometary Dust

scholarly journals The asteroid-comet continuum from laboratory and space analyses of comet samples and micrometeorites

2015 ◽  
Vol 11 (A29A) ◽  
pp. 253-256 ◽  
Author(s):  
Cécile Engrand ◽  
Jean Duprat ◽  
Noémie Bardin ◽  
Emmanuel Dartois ◽  
Hugues Leroux ◽  
...  
Keyword(s):  
Solar System ◽  
Interplanetary Dust ◽  
Cosmic Dust ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Cometary Dust ◽  
History Of ◽  
Polar Snow ◽  
Comet 67P ◽  
Cometary Origin

AbstractComets are probably the best archives of the nascent solar system, 4.5 Gyr ago, and their compositions reveal crucial clues on the structure and dynamics of the early protoplanetary disk. Anhydrous minerals (olivine and pyroxene) have been identified in cometary dust for a few decades. Surprisingly, samples from comet Wild2 returned by the Stardust mission in 2006 also contain high temperature mineral assemblages like chondrules and refractory inclusions, which are typical components of primitive meteorites (carbonaceous chondrites - CCs). A few Stardust samples have also preserved some organic matter of comet Wild 2 that share some similarities with CCs. Interplanetary dust falling on Earth originate from comets and asteroids in proportions to be further constrained. These cosmic dust particles mostly show similarities with CCs, which in turn only represent a few percent of meteorites recovered on Earth. At least two (rare) families of cosmic dust particles have shown strong evidences for a cometary origin: the chondritic porous interplanetary dust particles (CP-IDPs) collected in the terrestrial stratosphere by NASA, and the ultracarbonaceous Antarctic Micrometeorites (UCAMMs) collected from polar snow and ice by French and Japanese teams. Analyses of dust particles from the Jupiter family comet 67P/Churyumov-Gerasimenko by the dust analyzers on Rosetta orbiter (COSIMA, GIADA, MIDAS) suggest a relationship to interplanetary dust/micrometeorites. A growing number of evidences highlights the existence of a continuum between asteroids and comets, already in the early history of the solar system.

scholarly journals Cometary dust in Antarctic micrometeorites

2012 ◽  
Vol 8 (S288) ◽  
pp. 123-129 ◽  
Author(s):  
Naoya Imae
Keyword(s):  
Interstellar Dust ◽  
Compositional Analysis ◽  
Interplanetary Dust ◽  
Coarse Grained ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Interstellar Gas ◽  
Cometary Nuclei ◽  
Fine Grained ◽  
Cometary Dust

AbstractCometary nuclei consist of aggregates of interstellar dust particles less than ~1 μm in diameter and can produce rocky dust particles as a result of the sublimation of ice as comets enter the inner solar system. Samples of fine-grained particles known as chondritic porous interplanetary dust particles (CP-IDPs), possibly from comets, have been collected from the Earth's stratosphere. Owing to their fine-grained texture, these particles were previously thought to be condensates formed directly from interstellar gas. However, coarse-grained chondrule-like objects have recently been observed in samples from comet 81P/Wild 2. The chondrule-like objects are chemically distinct from chondrules in meteoritic chondrites, possessing higher MnO contents (0.5 wt%) in olivine and low-Ca pyroxene. In this study, we analyzed AMM samples by secondary electron microscopy and backscattered electron images for textural observations and compositional analysis. We identified thirteen AMMs with characteristics similar to those of the 81P/Wild 2 samples, and believe that recognition of these similarities necessitates reassessment of the existing models of chondrule formation.

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