Volatile Abundances, Extended Coma Sources, and Nucleus Ice Associations in Comet C/2014 Q2 (Lovejoy)

Russo, N. Dello; Vervack, R. J.; Kawakita, Hideyo; Bonev, B. P.; DiSanti, M. A.; Gibb, E. L.; McKay, Adam; Cochran, A. L.; Weaver, H. A.; Biver, Nicolás; Crovisier, J.; Bockelée‐Morvan, Dominique; Kobayashi, Hitomi; Harris, Walter M.; Roth, Nathan X.; Saki, Mohammad; Khan, Younas

doi:10.3847/psj/ac323c

Cited by 6 publications

(1 citation statement)

References 82 publications

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“…If high abundances of hydrocarbons were transferred from the outer disk, then hydrocarbon ices should be detectable in edge-on disks around VLMSs or in other high C/O astrophysical environments. Although comets in the Solar System are generally oxygen-rich, carbon-rich molecules such as CH 4 , C 2 H 2 , C 2 H 6 , C 6 H 6 , HCN, HC 3 N, and CO 2 have been detected in the comets 67P/Churyumov–Gerasimenko and C/2014 Q2 (Lovejoy) ( 35 , 36 ). The small molecules C 2 and C 3 are commonly observed in comets and have been suggested to form by the breakdown of C 2 H 6 , C 3 H 4 , or C 4 H 2 ( 37 ).…”

Section: Origin Of the Hydrocarbonsmentioning

confidence: 99%

Abundant hydrocarbons in the disk around a very-low-mass star

Arabhavi,

Kamp,

Henning

et al. 2024

Science

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Very-low-mass stars (those less than 0.3 solar masses) host orbiting terrestrial planets more frequently than other types of stars. The compositions of those planets are largely unknown but are expected to relate to the protoplanetary disk in which they form. We used James Webb Space Telescope mid-infrared spectroscopy to investigate the chemical composition of the planet-forming disk around ISO-ChaI 147, a 0.11-solar-mass star. The inner disk has a carbon-rich chemistry; we identified emission from 13 carbon-bearing molecules, including ethane and benzene. The high column densities of hydrocarbons indicate that the observations probe deep into the disk. The high carbon-to-oxygen ratio indicates radial transport of material within the disk, which we predict would affect the bulk composition of any planets forming in the disk.

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Section: Origin Of the Hydrocarbonsmentioning

confidence: 99%

Abundant hydrocarbons in the disk around a very-low-mass star

Arabhavi,

Kamp,

Henning

et al. 2024

Science

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Comprehensive Study of the Chemical Composition and Spatial Outgassing Behavior of Hyperactive Comet 46P/Wirtanen Using Near-IR Spectroscopy during its Historic 2018 Apparition

Khan

Gibb

Roth

et al. 2023

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We present a comprehensive analysis of the chemical composition of the Jupiter-family comet and potential spacecraft target 46P/Wirtanen, in the near-IR wavelength range. We used iSHELL at the NASA Infrared Telescope Facility to observe the comet on 11 pre-, near-, and postperihelion dates in 2018 December and 2019 January and February during its historic apparition. We report rotational temperatures, production rates, and mixing ratios with respect to H2O and C2H6 or 3σ upper limits of the primary volatiles H2O, HCN, CH4, C2H6, CH3OH, H2CO, NH3, CO, C2H2, and HC3N. We also discuss the spatial outgassing of the primary volatiles, to understand their sources and the spatial associations between them. The spatial profiles of H2O in 46P/Wirtanen suggest the presence of extended H2O outgassing sources in the coma, similar to the EPOXI target comet 103P/Hartley 2. 46P/Wirtanen is among the few known hyperactive comets, and we note that its composition and outgassing behavior are similar to those of other hyperactive comets in many ways. We note that the analyzed parent volatiles showed different variations (relative mixing ratios) during the apparition. We compared the chemical composition of 46P/Wirtanen with the mean abundances in Jupiter-family comets and the comet population as measured with ground-based near-IR facilities to date. The molecular abundances in 46P/Wirtanen suggest that although they were changing, the variations were small compared to the range in the comet population, with CH3OH showing notably more variation as compared to the other molecules.

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Direct Simulation Monte Carlo Modeling of Ammonia in Comet C/2014 Q2 (Lovejoy)

Kawakita,

Dello Russo,

Vervack

et al. 2023

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Ammonia (NH3), likely the most abundant nitrogen-bearing molecule in cometary ices followed by hydrogen cyanide, is believed to be stored in the nucleus predominantly as a parent ice. However, spatial profiles of NH3 observed in comet C/2014 Q2 (Lovejoy) in the near-infrared region are consistent with a distributed source contribution (Dello Russo et al. 2022). We developed the direct simulation Monte Carlo model of ammonia in cometary coma and applied it to comet C/2014 Q2 (Lovejoy). Results suggest that NH3 molecules in the coma of C/2014 Q2 (Lovejoy) can plausibly originate from a combination of parent molecules of NH3 in the coma and a NH3 nucleus source. We demonstrate that the parents of NH3 having photodissociation lifetimes of several hundreds of seconds or longer (at 1 au from the Sun) can explain the observed spatial profile of NH3 in comet C/2014 Q2 (Lovejoy). Even though ammonia salts are possible candidates for parents of NH3, some simple ammonium salts such as NH4CN or NH4Cl may dissociate thermally within very short lifetimes after sublimation from the nucleus, so the contribution from those ammonium salts may be indistinguishable from the nucleus source. The lack of experimental data on photoprocesses for potential NH3 parent molecules prevent us from identifying the origin of NH3 in comets. Experimental and theoretical studies of photodissociation/ionization reactions of potential NH3 parent molecules by the solar UV radiation field are encouraged for the future identification of NH3 parents in comets.

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Volatile Abundances, Extended Coma Sources, and Nucleus Ice Associations in Comet C/2014 Q2 (Lovejoy)

Cited by 6 publications

References 82 publications

Abundant hydrocarbons in the disk around a very-low-mass star

Abundant hydrocarbons in the disk around a very-low-mass star

Comprehensive Study of the Chemical Composition and Spatial Outgassing Behavior of Hyperactive Comet 46P/Wirtanen Using Near-IR Spectroscopy during its Historic 2018 Apparition

Direct Simulation Monte Carlo Modeling of Ammonia in Comet C/2014 Q2 (Lovejoy)

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