Ion composition and dynamics at comet Halley

Balsiger, H.; Altwegg, Kathrin; Bühler, F.; Geiss, J.; Ghielmetti, A. G.; Goldstein, B. E.; Goldstein, R.; Huntress, W. T.; Ip, W. H.; Lazarus, A. J.; Meier, Anna; Neugebauer, M.; Rettenmund, U.; Rosenbauer, H.; Schwenn, R.; Sharp, R. D.; Shelley, E. G.; Ungstrup, E.; Young, D. T.

doi:10.1038/321330a0

Cited by 369 publications

(115 citation statements)

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“…The ion mass spectra of the coma of comet Halley are richly complex, as illustrated by the early results published by Balsiger et al (1986). In this paper we concentrate on the most abundant group of ions in Halley ion mass spectra; the group with masses between 12 and 19 amu.…”

Section: Introductionmentioning

confidence: 95%

“…We focus on an analysis of ion processes inside the contact surface (along the Giotto trajectory, -4600 km from the nucleus; Balsiger et al 1986) where the ion chemistry is relatively straightforward, and where photoionization is the dominant ionization process. Also, ion flow is predominantly radial in this region, which simplifies the model analysis.…”

Section: Introductionmentioning

confidence: 99%

“…The peak at m/q = 15 is diagnostic for CH 3 + ions, but with a potential contribution from NH+. Balsiger et al (1986) have reported that the dominance of the 15 peak relative to 16 over the entire inner coma identifies this peak as mainly CH3 + rather than NH+. This is because ofall ions with m/q::;; 16 [i.e., CH.+ (n = 0-4), NH.+ (n = 0-2), and o+], only CH3 + does not react with water, the main constituent of the coma.…”

Section: Introductionmentioning

confidence: 99%

“…Fig. 8 in Balsiger et al, 1986). The peak at m/q = 15 is diagnostic for CH 3 + ions, but with a potential contribution from NH+.…”

Section: Introductionmentioning

confidence: 99%

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Evidence for methane and ammonia in the coma of comet P/Halley

Allen

Delitsky

Huntress

et al. 1988

Exploration of Halley’s Comet

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Summary. Methane and ammonia abundances in the coma of Halley are derived from Giotto IMS data using an Eulerian model of chemical and physical processes inside the contact surface to simulate Giotto HIS ion mass spectral data for mass-to-charge ratios (m/q) from 15 to 19. The ratio m/q = 19/18 as a function of distance from the nucleus is not reproduced by a model for a pure water coma. It is necessary to include the presence of NH 3 , and uniquely NH 3 , in coma gases in order to explain the data. A ratio of production rates Q(NH3)/Q(H20) = 0.01-Q.02 results in model values approximating the Giotto data. Methane is identified as the most probable source of the distinct peak at m/q = 15. The observations are fit best with Q(CH4 )/Q(H2 0) = 0.02. The chemical composition of the comet nucleus implied by these production rate ratios is unlike that of the outer planets. On the other hand, there are also significant differences from observations of gas phase interstellar material.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Fig. 8 in Balsiger et al, 1986). The peak at m/q = 15 is diagnostic for CH 3 + ions, but with a potential contribution from NH+.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evidence for methane and ammonia in the coma of comet P/Halley

Allen

Delitsky

Huntress

et al. 1988

Exploration of Halley’s Comet

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“…The new D/H exchange mechanism proceeds through the formation of an excited mono-deuterated hydronium state, H 2 DO * (possibly ionic), which subsequently dissociates to HDO or OD through preferential loss of collisionally excited O-H bonds. Hydronium ions (H 3 O + and H 2 DO + ) have been detected in comae, e.g., 1P/Halley (Balsiger et al 1986(Balsiger et al , 1995, and have several transitions that make them great candidates for remote spectroscopic evaluation of the water D/H ratio. H 3 O + ions have also been detected in the 67P coma about 30 km from the nucleus between 3.09 and 2.8 au (Fuselier et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Dynamic Deuterium Enrichment in Cometary Water via Eley–rideal Reactions

Yao

Giapis

2017

ApJ

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The deuterium-to-hydrogen ratio (D/H) in water found in the coma of Jupiter family comet (JFC) 67P/ Churyumov-Gerasimenko was reported to be (5.3±0.7)×10 −4 , the highest among comets and three times the value for other JFCs with an ocean-like ratio. This discrepancy suggests the diverse origins of JFCs and clouds the issue of the origin of Earth's oceanic water. Here we demonstrate that Eley-Rideal reactions between accelerated water ions and deuterated cometary surface analogs can lead to instantaneous deuterium enrichment in water scattered from the surface. The reaction proceeds with H 2 O + abstracting adsorbed D atoms, forming an excited H 2 DO * state, which dissociates subsequently to produce energetic HDO. Hydronium ions are also produced readily by the abstraction of H atoms, consistent with H 3 O + detection and abundance in various comets. Experiments with water isotopologs and kinematic analysis on deuterated platinum surfaces confirmed the dynamic abstraction mechanism. The instantaneous fractionation process is independent of the surface temperature and may operate on the surface of cometary nuclei or dust grains, composed of deuterium-rich silicates and carbonaceous chondrites. The requisite energetic water ions have been detected in the coma of 67P in two populations. This dynamic fractionation process may temporarily increase the water D/H ratio, especially as the comet gets closer to the Sun. The magnitude of the effect depends on the water ion energy-flux and the deuterium content of the exposed cometary surfaces.

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Spatial distribution of low‐energy plasma around comet 67P/CG from Rosetta measurements

Edberg

Eriksson

Odelstad

et al. 2015

Geophysical Research Letters

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We use measurements from the Rosetta plasma consortium Langmuir probe and mutual impedance probe to study the spatial distribution of low‐energy plasma in the near‐nucleus coma of comet 67P/Churyumov‐Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e., the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be ∼1–2·10−6, at a cometocentric distance of 10 km and at 3.1 AU from the Sun. A clear 6.2 h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisionless plasma within 260 km from the nucleus falls off with radial distance as ∼1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low‐energy plasma around the comet.

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Ion composition and dynamics at comet Halley

Cited by 369 publications

References 13 publications

Evidence for methane and ammonia in the coma of comet P/Halley

Evidence for methane and ammonia in the coma of comet P/Halley

Dynamic Deuterium Enrichment in Cometary Water via Eley–rideal Reactions

Spatial distribution of low‐energy plasma around comet 67P/CG from Rosetta measurements

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