scholarly journals Episodic formation of cometary material in the outburst of a young Sun-like star

Nature ◽  
2009 ◽  
Vol 459 (7244) ◽  
pp. 224-226 ◽  
Author(s):  
P. Ábrahám ◽  
A. Juhász ◽  
C. P. Dullemond ◽  
Á. Kóspál ◽  
R. van Boekel ◽  
...  
Keyword(s):  
Cometary Material

Laboratory and in-situ analysis of comet dust

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.

Polarization of disintegrating Comet C/2019 Y4 (ATLAS)

2020 ◽  
Vol 497 (2) ◽  
pp. 1536-1542
Author(s):  
Evgenij Zubko ◽  
Maxim Zheltobryukhov ◽  
Ekaterina Chornaya ◽  
Anton Kochergin ◽  
Gorden Videen ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Carbonaceous Material ◽  
Solar Radiation Pressure ◽  
Carbonaceous Particles ◽  
Wide Range ◽  
Before And After ◽  
Nucleus Surface ◽  
Cometary Material ◽  
Absorbing Material ◽  
Phase Angles

ABSTRACT We observe Comet C/2019 Y4 (ATLAS) before and after its disintegration while making polarimetric measurements over a wide range of phase angles. The disintegration event was marked with a dramatic growth of the positive polarization branch that is consistent with a large relative abundance of absorbing material of up to (96.5 ± 3.4) per cent. This polarization spike relaxed as the carbonaceous particles are preferentially swept from the coma due to solar-radiation pressure. The observations suggest that the primordial material stored within comets is extremely rich in carbonaceous material. The pristine cometary material is processed by subsequent solar interactions, forming a refractory crust on the nucleus surface. Polarimetry provides a means of measuring the volume ratio of carbonaceous material, and hence the weathering that has occurred on the comet due to these interactions. The polarimetric response of Comet C/2019 Y4 (ATLAS) appears similar to that of Comet C/1995 O1 (Hale-Bopp), except on few epochs that are similar to that of Comet C/1996 B2 (Hyakutake).

scholarly journals 5. Meteoroid Populations and Orbits

1977 ◽  
Vol 39 ◽  
pp. 143-152 ◽  
Author(s):  
Z. Ceplecha
Keyword(s):  
Carbonaceous Chondrites ◽  
Ordinary Chondrites ◽  
Group I ◽  
Cometary Material ◽  
Group A ◽  
Statistical Studies ◽  
Group Ii ◽  
Group B ◽  
Group D

Statistical studies of the photographic data on atmospheric trajectories and orbits of meteors (from 10-4 g to hundreds of tons) point to 5 groups of bodies with different structure and composition. The following classification is proposed: Fireball group I = exceptional cases of so-called “asteroidal” bodies among Super-Schmidt (SS) and small-camera (SC) meteors 5 ordinary chondrites. Fireball group II = group A among SS and SC = carbonaceous chondrites. Group B among SS and SC = dense cometary materials with small perihelion distances (not distinguishable among fireballs). Fireball group IIIa = group C among SS and SC = regular cometary material. Fireball group IIIB = group D (above C) of SS and SC = Draconid-shower type of cometary material. Statistics of the orbits for separate groups is considered and characteristic orbits are given.

scholarly journals Physical Properties of the Interplanetary Dust

1971 ◽  
Vol 12 ◽  
pp. 377-388
Author(s):  
Martha S. Hanner
Keyword(s):  
Optical Properties ◽  
Spatial Distribution ◽  
Chemical Composition ◽  
Physical Properties ◽  
Physical Nature ◽  
Interplanetary Dust ◽  
Physical Structure ◽  
Dust Particles ◽  
Cometary Material ◽  
Direct Condensation

The interplanetary dust may be composed of cometary material, interstellar grains, debris from asteroidal collisions, primordial material formed by direct condensation, or contributions from all of these sources. Before we can determine the origin of the dust, we need to know its physical nature, spatial distribution, and the dynamical forces that act on the particles. The spatial distribution and dynamics are separately treated in this symposium by Roosen. We discuss here the physical characteristics of the dust particles: their size distribution, chemical composition, physical structure, and optical properties.

FIB ‐ TEM analysis of cometary material in 10 Stardust foil craters

2020 ◽  
Vol 55 (6) ◽  
pp. 1349-1370 ◽  
Author(s):  
Brendan A. Haas ◽  
Christine Floss ◽  
Rhonda M. Stroud ◽  
Ryan C. Ogliore
Keyword(s):  
Tem Analysis ◽  
Cometary Material

A cometary mechanism for the formation of tektites

1963 ◽  
Vol 272 (1351) ◽  
pp. 467-480 ◽  
Keyword(s):  
Small Eccentricity ◽  
The Earth ◽  
Short Period ◽  
Cometary Material ◽  
General Order ◽  
Order Of Magnitude

Passage of the Earth through a comet must occur on average every million years approximately and last for a time of a few hours. A proportion of short-period comets will have had sufficiently small eccentricity (less than about 0.6) for accretion of cometary material to occur during such passages and produce a narrow jet of material falling vertically down-wards through the atmosphere. The orbits of these comets are such that the jet would be most likely to fall within lower latitudes, as is found for tektite fields. The temperature within the accretion-stream would be sufficiently great to vaporize most materials, and the tektites are regarded as forming from the most refractory substances within the stream, so that they are not characteristic of cometary compositions. The speeds of entry into the atmosphere are high enough for ablation to occur, and the dimensions of the resulting fields and their total masses agree in general order of magnitude with those estimated for actual fields.

scholarly journals Analytical methods for discriminating stardust in aerogel capture media

2008 ◽  
Vol 23 (2) ◽  
pp. 81-86 ◽  
Author(s):  
Sean Brennan ◽  
Katharina Luening ◽  
Konstantin Ignatyev ◽  
Piero Pianetta ◽  
Hope A. Ishii ◽  
...  
Keyword(s):  
Analytical Methods ◽  
The Other ◽  
Threshold Method ◽  
X Ray ◽  
Threshold Levels ◽  
Trace Contaminants ◽  
Cometary Material

Methods using X-ray fluorescence have been developed to identify cometary material captured in aerogel during the NASA Stardust mission to Comet 81P/Wild 2. These analytical methods are necessitated by the levels of trace contaminants present in the aerogel. The cometary material disaggregates during deceleration in the aerogel, so fluorescence mapping of the entire track (which can be several millimeters long) is necessary. Distinguishing those pixels which have cometary material and aerogel from those which have only cometary material can be very challenging. We have chosen a “dual threshold” method, with some pixels clearly having only aerogel (plus contaminants) and other pixels clearly having cometary and aerogel material. Between these two threshold levels is a set of pixels which cannot be easily ascribed to one or the other. By leaving these pixels out of the analysis, the estimate of cometary material is improved.

The nature of comets

1987 ◽  
Vol 323 (1572) ◽  
pp. 437-446 ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Future Research ◽  
Head Region ◽  
Scientific Curiosity ◽  
Halley's Comet ◽  
First Results ◽  
Cometary Material ◽  
Field Lines

The vast scientific campaign associated with the 1986 return of Halley’s Comet has greatly improved and expanded our knowledge of comets. An overview of the first results is presented here with emphasis on the large-scale structure, the chemistry, and the nucleus. Biermann and Alfven’s basic large-scale picture involving the interaction with the solar wind was confirmed. The interaction extends over very large distances and involves the draping of magnetic field lines from the solar wind around the head region. The near-nuclear region is essentially free of magnetic field. The cometary environment is a rich plasma physics laboratory as well as the site of spectacular disconnection events. As Whipple proposed, the chemical composition of the nucleus is largely water, and the breakup of the water molecule produces the large hydrogen-cloud surrounding the comet. Minor constituents with high molecular mass have been observed in the comet. The composition of the dust generally resembles carbonaceous chondrites enriched in the elements H, C, N and O. The interest in the cometary chemistry stems from the belief that cometary material is probably the best remnant of the solar nebula’s original composition. The nucleus is monolithic, as predicted by Whipple’s icy-conglomerate model. Far from spherical, the nucleus is irregular and peanut- or potato-shaped. The surface is very dark, and the emission of gas and dust occurs in jets on the sunward side. Irregular erosion of the surface, which is covered by a dust crust, could lead to many interesting possibilities for outbursts or splitting. Even with our current enhancement of knowledge, comets will continue to excite scientific curiosity. Future research on comets should be very fruitful.

scholarly journals Irradiation Effects on Comets and Cometary Debris

1989 ◽  
Vol 116 (1) ◽  
pp. 243-275 ◽  
Author(s):  
G. Strazzulla ◽  
R.E. Johnson
Keyword(s):  
Interstellar Dust ◽  
Ion Irradiation ◽  
Cosmic Ray ◽  
Oort Cloud ◽  
Energetic Ions ◽  
Fast Ions ◽  
Laboratory Results ◽  
Cometary Material ◽  
Physical Changes ◽  
T Tau

AbstractFor the last 10 years, many experimental results have been obtained on the chemical and physical changes induced by ion and electron irradiation of materials relevant to comets. Those results are reviewed here, together with their physical interpretation and their relevance for cometary astrophysics. Cometary material is, from the time of its origin, altered by the large amount of energy deposited by energetic ions. Four phases of the irradiation history are considered: the pre-cometary phase, during which interstellar dust is bombarded by cosmic-ray ions; the accretion phase, during which comets are built up, possibly in an environment rich in fast ions (T-Tau phase); the cometary phase, during which the outer layers of the comets are irradiated by galactic ions in the Oort cloud; and the post-cometary phase, during which dust, lost from the comet, is bombarded by solar ions.The relevant applications of laboratory results are reviewed. In particular, the ability of ion irradiation of simple carbon-containing ices to produce complex refractory organic materials is discussed. In the Oort cloud, this process can occur several meters into the surface, so that the buildup of a stable organic crust may occur. A comparison of ion irradiation at various stages is also made with other models for the production of organics.

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