First Comet Observations with NIRSPEC-2 at Keck: Outgassing Sources of Parent Volatiles and Abundances Based on Alternative Taxonomic Compositional Baselines in 46P/Wirtanen

Bonev, B. P.; Russo, N. Dello; DiSanti, M. A.; Martin, Emily C.; Doppmann, Gregory; Vervack, R. J.; Villanueva, Gerónimo; Kawakita, Hideyo; Gibb, E. L.; Combi, M. R.; Roth, Nathan X.; Saki, Mohammad; McKay, Adam; Cordiner, Martin; Bodewits, Dennis; Crovisier, J.; Biver, Nicolás; Cochran, A. L.; Shou, Y.; Khan, Younas; Venkataramani, Kumar

doi:10.3847/psj/abd03c

Cited by 26 publications

(42 citation statements)

References 98 publications

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“…The Rosetta mission provided the unique opportunity to monitor the evolution of the cometary coma with in situ measurements over 2 years. Cometary flyby missions collect in situ data as well, but they are limited to much shorter time periods. , The number of comets accessible via Earth-bound observations is more comprehensive and covers, besides comets in the solar system, − also interstellar objects. , …”

Section: Introductionmentioning

confidence: 99%

The Ice Composition Close to the Surface of Comet 67P/Churyumov-Gerasimenko

Läuter

Kramer

Rubin

et al. 2022

ACS Earth Space Chem.

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The relation between ice composition in the nucleus of comet 67P/Churyumov-Gerasimenko on the one hand and relative abundances of volatiles in the coma on the other hand is important for the interpretation of density measurements in the environment of the cometary nucleus. For the 2015 apparition, in situ measurements from the two ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) sensors COPS (COmet Pressure Sensor) and DFMS (Double Focusing Mass Spectrometer) determined gas densities at the spacecraft position for the 14 gas species H2O, CO2, CO, H2S, O2, C2H6, CH3OH, H2CO, CH4, NH3, HCN, C2H5OH, OCS, and CS2. We derive the spatial distribution of the gas emissions on the complex shape of the nucleus separately for 50 subintervals of the 2 year mission time. The most active patches of gas emission are identified on the surface. We retrieve the relation between solar irradiation and observed emissions from these patches. The emission rates are compared to a minimal thermophysical model to infer the surface active fraction of H2O and CO2. We obtain characteristic differences in the ice composition close to the surface between the two hemispheres with a reduced abundance of CO2 ice on the northern hemisphere (locations with positive latitude). We do not see significant differences for the ice composition on the two lobes of 67P/C-G.

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Section: Introductionmentioning

confidence: 99%

The Ice Composition Close to the Surface of Comet 67P/Churyumov-Gerasimenko

Läuter

Kramer

Rubin

et al. 2022

ACS Earth Space Chem.

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“…In C/2012 S1 (ISON), NH 3 and C 2 H 2 showed some enhancement of spatial profiles in the antisunward direction relative to other measured volatiles that were consistent with contributions from extended sources (DiSanti et al 2016;Dello Russo et al 2016b). Spatial profiles of C 2 H 2 in JFCs 103P/Hartley 2 and 46P/Wirtanen showed no evidence of an extended source contribution, but S/Ns were marginal especially in the profile wings (Dello Russo et al 2011;Kawakita et al 2013;Bonev et al 2021). IR spatial profiles of H 2 CO in C/2002 T7 (LINEAR) and C/2012 S1 (ISON) showed no evidence for extended sources (DiSanti et al 2006(DiSanti et al , 2016Dello Russo et al 2016b); however, there is extensive evidence of H 2 CO extended sources in comets from Giotto measurements of 1P/…”

Section: Spatial Distributions Of Volatiles In the Comamentioning

confidence: 64%

“…In cases where minor blends were used, a correction was applied for the small contributions from other species. To get the most complete picture of relative abundances in C/2014 Q2 (Lovejoy), we present abundance ratios relative to both a polar (H 2 O) and a nonpolar (C 2 H 6 ) molecule (e.g., Bonev et al 2021). The relative abundances given by a weighted average for all independent measurements are given in Table 3.…”

Section: Production Rates and Relative Abundancesmentioning

confidence: 99%

“…Although these compositional interrelationships provide information on global molecular associations within the comet population, they do not reveal how ices are stored or associated in the nuclei of comets. Clues to the associations of ices in the nucleus have been obtained at IR wavelengths through the study of spatial distributions of volatiles in the coma (e.g., DiSanti et al 1999;Dello Russo et al 2011;Villanueva et al 2011a;Bonev et al 2014Bonev et al , 2021Paganini et al 2014); however, data are generally not of sufficient quality to perform coma spatial studies of more than a few species with the strongest and most spatially extended emissions. In particular, information on the spatial distributions of C 2 H 2 , NH 3 , and H 2 CO in comets from IR studies is sparse.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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High-resolution infrared spectra of comet C/2014 Q2 Lovejoy were acquired with NIRSPEC at the W. M. Keck Observatory on two post-perihelion dates (UT 2015 February 2 and 3). H2O was measured simultaneously with CO, CH3OH, H2CO, CH4, C2H6, C2H4, C2H2, HCN, and NH3 on both dates, and rotational temperatures, production rates, relative abundances, H2O ortho-to-para ratios, and spatial distributions in the coma were determined. The first detection of C2H4 in a comet from ground-based observations is reported. Abundances relative to H2O for all species were found to be in the typical range compared with values for other comets in the overall population to date. There is evidence of variability in rotational temperatures and production rates on timescales that are small compared with the rotational period of the comet. Spatial distributions of volatiles in the coma suggest complex outgassing behavior. CH3OH, HCN, C2H6, and CH4 spatial distributions in the coma are consistent with direct release from associated ices in the nucleus and are peaked in a more sunward direction compared with co-measured dust. H2O spatial profiles are clearly distinct from these other four species, likely due to a sizable coma contribution from icy grain sublimation. Spatial distributions for C2H2, H2CO, and NH3 suggest substantial contributions from extended coma sources, providing further evidence for distinct origins and associations for these species in comets. CO shows a different spatial distribution compared with other volatiles, consistent with jet activity from discrete nucleus ice sources.

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“…In this paper, we test the hypothesis put forth by A'Hearn et al ( 2011), Protopapa et al (2014), andKelley et al (2013) that sublimating water ice in the coma in the form of small grains and/or large chunks is responsible for a comet hyperactivity. We point out that Knight et al (2021) and Bonev et al (2021) both provide indirect evidence for the presence of an extended source of water vapor in the coma of Wirtanen. However, no information on the properties of the ice that produces the water vapor, such as particle size and ice-to-dust ratio, has been retrieved based on their work.…”

Section: Summary and Discussionmentioning

confidence: 79%

Non-detection of water-ice grains in the coma of comet 46P/Wirtanen and implications for hyperactivity

Protopapa¹,

Kelley²,

Woodward³

et al. 2021

Preprint

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Hyperactive comets have high water production rates, with inferred sublimation areas of order the surface area of the nucleus. Comets 46P/Wirtanen and 103P/Hartley 2 are two examples of this cometary class. Based on observations of comet Hartley 2 by the Deep Impact spacecraft, hyperactivity appears to be caused by the ejection of water-ice grains and/or water-ice rich chunks of nucleus into the coma. These materials increase the sublimating surface area, and yield high water production rates. The historic close approach of comet Wirtanen to Earth in 2018 afforded an opportunity to test Hartley 2 style hyperactivity in a second Jupiter-family comet. We present high spatial resolution, near-infrared spectroscopy of the inner coma of Wirtanen. No evidence for the 1.5-or 2.0-µm water-ice absorption bands is found in six 0.8-2.5 µm spectra taken around perihelion and closest approach to Earth. In addition, the strong 3.0-µm water-ice absorption band is absent in a 2.0-5.3 µm spectrum taken near perihelion. Using spectroscopic and sublimation lifetime models we set constraints on the physical properties of the ice grains in the coma, assuming they are responsible for the comet's hyperactivity. We rule out pure water-ice grains of any size, given their long lifetime. Instead, the hyperactivity of the nucleus and lack of water-ice absorption features in our spectra can be explained either by icy grains on the order of 1 µm in size with a small amount of low albedo dust (greater than 0.5% by volume), or large chunks containing significant amounts of water ice.

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First Comet Observations with NIRSPEC-2 at Keck: Outgassing Sources of Parent Volatiles and Abundances Based on Alternative Taxonomic Compositional Baselines in 46P/Wirtanen

Cited by 26 publications

References 98 publications

The Ice Composition Close to the Surface of Comet 67P/Churyumov-Gerasimenko

The Ice Composition Close to the Surface of Comet 67P/Churyumov-Gerasimenko

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

Non-detection of water-ice grains in the coma of comet 46P/Wirtanen and implications for hyperactivity

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