First detection of hydrogen isocyanide (HNC) in Titan’s atmosphere

Moreno, R.; Lellouch, E.; Lara, L. M.; Courtin, R.; Bockelée‐Morvan, Dominique; Hartogh, P.; Rengel, Miriam; Biver, Nicolás; Banaszkiewicz, M.; González, A.

doi:10.1051/0004-6361/201118189

Cited by 49 publications

(56 citation statements)

References 43 publications

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“…2 and are compared with our model. The column density we obtain is 3.4 × 10 13 cm −2 above 500 km whereas the value derived by Moreno et al (2011) at this altitude is 1.2 × 10 13 cm −2 (about 3 times lower). We will see in the following that this discrepancy can be simply explained by our poor knowledge of some key reactions.…”

Section: Hnc Observationscontrasting

confidence: 72%

“…Following the prediction of Petrie (2001), Moreno et al (2011) concluded that a purely ionospheric source may be quantitatively viable for HNC, provided that the protonation rates are not too high. Here we show that a purely neutral source is efficient enough to produce HNC and HCN in the upper atmosphere of Titan in agreement with current observations.…”

Section: Discussionmentioning

confidence: 88%

“…If restricted above 1000 km, the mixing ratio of HNC derived from observation of Moreno et al (2011) is about 6 × 10 −5 and the mixing ratio of HCN is in the range (0.2−6) × 10 −3 according the various observations. This leads to a HNC/HCN ratio of about 0.01−0.3.…”

Section: Sensitivity To Eddy Diffusionmentioning

confidence: 86%

“…Very recently, Moreno et al (2011) reported the first identification of HNC in Titan's atmosphere from observations using the HIFI instrument on the Herschel 1 Space Observatory. The column density of HNC inferred from these observations is in the range (0.6−1.5) × 10 13 cm −2 for altitudes between 400 and 1000 km, but the authors noticed that it was not possible to constrain the vertical profile of HNC from these data.…”

Section: Hnc Observationsmentioning

confidence: 99%

“…Their preliminary analysis suggests that the bulk of this emission must originate at altitudes above 300 km. However, the observations cannot strictly establish a HNC vertical profile (Moreno et al 2011). Petrie (2001) argued that HNC was likely to be formed almost entirely by an ion-molecule mechanism and that neutral formation pathways were not viable.…”

Section: Introductionmentioning

confidence: 99%

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Neutral production of hydrogen isocyanide (HNC) and hydrogen cyanide (HCN) in Titan’s upper atmosphere

Hébrard

Dobrijévic

Loison

et al. 2012

A&A

116

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Aims. Following the first detection of hydrogen isocyanide (HNC) in Titan's atmosphere, we have devised a new neutral chemical scheme for hydrogen cyanide (HCN) and HNC in the upper atmosphere of Titan. Methods. Our updated chemical scheme contains 137 compounds (with C, H, O and N elements) and 788 reactions (including 91 photolysis processes). To improve the chemistry of HNC and HCN, a careful review of the literature has been performed to retrieve critical reaction rates and to evaluate their uncertainty factors. We have also estimated the reaction rates of 48 new reactions using simple capture theory. Results. Our photochemical model gives abundances of HNC and HCN in reasonable agreement with observations. An uncertainty propagation study shows large uncertainties for HNC and relatively moderate uncertainties for HCN. A global sensitivity analysis pinpoints some key reactions to study as a priority to improve the predictivity of the model. Conclusions. In particular, our knowledge of the isomerization of HNC via the reaction H + HNC → HCN + H and the chemistry of H 2 CN needs to be improved. This study of the neutral chemistry taking place in the upper atmosphere of Titan is a prerequisite for future ionospheric models since ion-neutral reactions may also contribute significantly to HNC and HCN production.

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Section: Hnc Observationscontrasting

confidence: 72%

Section: Discussionmentioning

confidence: 88%

Section: Sensitivity To Eddy Diffusionmentioning

confidence: 86%

Section: Hnc Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Neutral production of hydrogen isocyanide (HNC) and hydrogen cyanide (HCN) in Titan’s upper atmosphere

Hébrard

Dobrijévic

Loison

et al. 2012

A&A

116

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Titan's atmosphere and climate

2017

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Titan is the only moon with a substantial atmosphere, the only other thick N2 atmosphere besides Earth's, the site of extraordinarily complex atmospheric chemistry that far surpasses any other solar system atmosphere, and the only other solar system body with stable liquid currently on its surface. The connection between Titan's surface and atmosphere is also unique in our solar system; atmospheric chemistry produces materials that are deposited on the surface and subsequently altered by surface‐atmosphere interactions such as aeolian and fluvial processes resulting in the formation of extensive dune fields and expansive lakes and seas. Titan's atmosphere is favorable for organic haze formation, which combined with the presence of some oxygen‐bearing molecules indicates that Titan's atmosphere may produce molecules of prebiotic interest. The combination of organics and liquid, in the form of water in a subsurface ocean and methane/ethane in the surface lakes and seas, means that Titan may be the ideal place in the solar system to test ideas about habitability, prebiotic chemistry, and the ubiquity and diversity of life in the universe. The Cassini‐Huygens mission to the Saturn system has provided a wealth of new information allowing for study of Titan as a complex system. Here I review our current understanding of Titan's atmosphere and climate forged from the powerful combination of Earth‐based observations, remote sensing and in situ spacecraft measurements, laboratory experiments, and models. I conclude with some of our remaining unanswered questions as the incredible era of exploration with Cassini‐Huygens comes to an end.

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Are Unsaturated Isocyanides so Different from the Corresponding Nitriles?

et al. 2011

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Simple unsaturated and cyclopropylic isocyanides are synthesized by an efficient and simple approach. These compounds with gradually increasing distance between the unsaturated moiety and the isonitrile group are studied by UV photoelectron spectroscopy and quantum chemical calculations, and also compared to the corresponding nitriles. The first photoelectron band of the unsaturated compounds is linked to removal of an electron from the HOMO, which corresponds to CC multiple-bond ionization in antibonding interaction with the π-isocyanide bond (in the same plane) for conjugated systems, or in antibonding interaction with the pseudo-π-CH(2) group for isolated systems. For the 1-ethenyl derivatives, both cyano and isocyano groups act as a π-electron acceptor from the vinyl group, but the isocyano π system is much more strongly destabilized (ionization energies (IEs) shift to smaller values) by vinyl (3.12 eV) than the cyano π system is (2.70 eV). In comparison with the 1-ethynyl derivatives, a less pronounced destabilization (2.69 eV) of π(NC) by the ethynyl system (1.86 eV for π(CN)), and nearly the same order of magnitude of the energetic gap between the total antibonding (π(CC)-π(NC)) and the total bonding (π(CC)+π(NC)) IEs for ethenyl and ethynyl compounds are noted. The huge values of these last-named data for H(2)C=CH-NC (3.85 eV) and for HC≡C-NC (4.04 eV) reflect the strong interaction between the unsaturated carbon-carbon moiety and the isocyanide group, and thus more efficient conjugation than for the corresponding nitriles.

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First detection of hydrogen isocyanide (HNC) in Titan’s atmosphere

Cited by 49 publications

References 43 publications

Neutral production of hydrogen isocyanide (HNC) and hydrogen cyanide (HCN) in Titan’s upper atmosphere

Neutral production of hydrogen isocyanide (HNC) and hydrogen cyanide (HCN) in Titan’s upper atmosphere

Titan's atmosphere and climate

Are Unsaturated Isocyanides so Different from the Corresponding Nitriles?

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