Composition of comet Halley dust particles from Vega observations

Kissel, J.; Sagdeev, R. Z.; Bertaux, Jean-Loup; Angarov, V. N.; Audouze, J.; Blamont, J. É.; Büchler, K.; Evlanov, E. N.; Fechtig, H.; Fomenkova, M. N.; Hoerner, H. von; Inogamov, N. A.; Khromov, V. N.; Knabe, W.; Krueger, F. R.; Langevin, Y.; Leonas, V. B.; Levasseur-Regourd, A. C.; Managadze, G. G.; Podkolzin, S. N.; Shapiro, V. D.; Tabaldyev, S. R.; Zubkov, B. V.

doi:10.1038/321280a0

Cited by 341 publications

(75 citation statements)

References 5 publications

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“…However, some "mild" photochemistry could lead to more complex, less volatile organics (Öberg et al 2009a). Some of this less volatile organic material could become similar to the so-called "CHON particles" detected in comets (Kissel et al 1986) after further processing in the disk.…”

Section: The Carbon Budget Of the Disk Atmospherementioning

confidence: 86%

The warm gas atmosphere of the HD 100546 disk seen byHerschel

Bruderer

Dishoeck

Doty

et al. 2012

A&A

260

454

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Context. With the Herschel Space Observatory, lines of simple molecules (C + , O, and high-J lines of CO, J up 14) have been observed in the atmosphere of protoplanetary disks. When combined with ground-based data on [C i], all principle forms of carbon can be studied. These data allow us to test model predictions for the main carbon-bearing species and verify the presence of a warm surface layer. The absence of neutral carbon [C i], which is predicted by models to be strong, can then be interpreted together with ionized carbon [C ii] and carbon monoxide. Aims. We study the gas temperature, excitation, and chemical abundance of the simple carbon-bearing species C, C + , and CO, as well as O by the method of chemical-physical modeling. Using the models, we explore the sensitivity of the lines to the entering parameters and constrain the region from which the line radiation emerges. Methods. Numerical models of the radiative transfer in the lines and dust are used together with a chemical network simulation and a calculation of the gas energetics to obtain the gas temperature. We present our new model, which is based on our previous models but includes several improvements that we report in detail, together with the results of benchmark tests. Results. A model of the disk around the Herbig Be star HD 100546 is able to reproduce the CO ladder together with the atomic finestructure lines of [O i] and either [C i] or [C ii]. We find that the high-J lines of CO can only be reproduced by a warm atmosphere with T gas T dust . The low-J lines of CO, observable from the ground, are dominated by the outer disk with a radius of several 100 AU, while the high-J CO observable with Herschel-PACS are dominated from regions within some tens of AU. The spectral profiles of high-J lines of CO are predicted to be broader than those of the low-J lines. We study the effect of several parameters including the size of the disk, the gas mass of the disk, the PAH abundance and distribution, and the amount of carbon in the gas phase. Conclusions. The main conclusions of our work are (i) only a warm atmosphere with T gas T dust can reproduce the CO ladder. (ii) The CO ladder together with [O i] and the upper limit to [C i] can be reproduced by models with a high gas/dust ratio and a low abundance of volatile carbon. These models however produce too small amounts of [C ii]. Models with a low gas/dust ratio and more volatile carbon also reproduce CO and [O i], are in closer agreement with observations of [C ii], but overproduce [C i]. Owing to the uncertain origin of the [C ii] emission, we prefer the high gas/dust ratio models, indicating a low abundance of volatile carbon.

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Section: The Carbon Budget Of the Disk Atmospherementioning

confidence: 86%

The warm gas atmosphere of the HD 100546 disk seen byHerschel

Bruderer

Dishoeck

Doty

et al. 2012

A&A

260

454

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“…Comets presently observed in the solar system are believed to be remnants of planetesimals that contained organic materials and/or amorphous carbon and are expected to preserve pristine material of the interstellar medium. This theory has long been accepted, and indeed, in situ measurements of comet 1P/Halley carried out by the VeGa-1 and 2 spacecraft in 1986 confirmed that all analyzed cometary dust particles contain carbonaceous material, and that in 25% of the particles, carbon is the dominant component (Kissel et al 1986;Fomenkova et al 1992). Similarly, a high proportion of organic matter was found in all 29 particles analyzed with the Cometary and Interstellar Dust Analyzer (CIDA) mass spectrometer during the comet Wild 2 flyby (Kissel et al 2004), but most of those particles were analyzed at distances greater than 650 km to the nucleus.…”

Section: Introductionmentioning

confidence: 85%

Evaluating the carbon depletion found by the Stardust mission in Comet 81P/Wild 2

Zubko

Muinonen

Shkuratov³

et al. 2012

A&A

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The low abundance of refractory carbonaceous material in samples collected by Stardust in comet 81P/Wild 2 coma was completely unexpected. If these results are universal to other comets, this necessitates a reformulation of current models of solar system formation. A polarimetric imaging analysis demonstrates that dust is not uniformly distributed within cometary coma, and that the circumnucleus halo region where the dust samples were collected must contain a low population of carbonaceous particles. Such regions are seen in other comets, suggesting that comet 81P/Wild 2 is not unusual and that the anomalous lack of carbon is not necessarily representative of the entire coma.

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“…Measurements by the VEGA and Giotto dust mass spectrometers demonstrated the presence of small grains predominantly composed of C,H,0, and N (Kissel et al 1986;Clark et al 1987). Further interpretation of these data also suggests the presence of heavy compounds with multiple bonds (Kissel and Krueger 1987).…”

Section: Other Evidence For Carbonaceous Grains In Cometsmentioning

confidence: 82%

Carbonaceous Compounds in Comets: Infrared Observations

Encrenaz

Knacke

1989

International Astronomical Union Colloquium

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ABSTRACT. The Comet Halley observations showed that carbon is a major component of the comet nucleus, with mass spectroscopic data giving near-cosmic C / 0 ratios. Gaseous and solid compounds were also observed with infrared spectroscopy, which gave detections of CO and CO2, probable detections or upper limits of H2CO and CH4, and a tentative detection of OCS. The CH4/CO ratio of less than unity in Comet Halley points to a CO-rich solar nebula; however, the ratio is higher than in interstellar clouds. A broad, complicated emission feature near 3.4 /mi is evidence for carbonaceous compounds containing C-H groups in gas or solid phases. Analysis of radiation mechanisms and abundance constraints suggests that thermal emission or transient heating by single photons can account for the 3.4-/fm emission feature. The band resembles (but is not identical to) bands of carbonaceous chondrite organic material, synthetic materials, and interstellar carbonaceous bands. Direct connections among these materials are possible, but have not been established.

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Composition of comet Halley dust particles from Vega observations

Cited by 341 publications

References 5 publications

The warm gas atmosphere of the HD 100546 disk seen byHerschel

The warm gas atmosphere of the HD 100546 disk seen byHerschel

Evaluating the carbon depletion found by the Stardust mission in Comet 81P/Wild 2

Carbonaceous Compounds in Comets: Infrared Observations

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