The Composition of the Protosolar Disk and the Formation Conditions for Comets

Willacy, Karen; Alexander, C.; Ali-Dib, Mohamad; Ceccarelli, C.; Charnley, Steven B.; Doronin, M.; Ellinger, Y.; Gast, Philipp; Gibb, E. L.; Milam, Stefanie N.; Mousis, O.; Pauzat, F.; Tornow, Carmen; Wirström, E. S.; Zicler, E.

doi:10.1007/s11214-015-0167-6

Cited by 50 publications

(39 citation statements)

References 207 publications

(225 reference statements)

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“…We discussed the possible connection between the low CO mixing ratios and the relative abundances of complex molecules in C/2014 Q2 in comparison with other comets. Further observations of future cometary apparitions, similar to those presented here, will provide important information on chemical formation pathways and physical conditions in the protosolar molecular cloud core and/or the protosolar nebula (e.g., Mandt et al 2015;Willacy et al 2015).…”

Section: Discussionmentioning

confidence: 56%

Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope

Val-Borro

Milam

Cordiner

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Comet composition provides critical information on the chemical and physical processes that took place during the formation of the Solar system. We report here on millimetre spectroscopic observations of the long-period bright comet C/2014 Q2 (Lovejoy) using the Atacama Pathfinder Experiment (APEX) band 1 receiver between 2015 January UT 16.948 and 18.120, when the comet was at heliocentric distance of 1.30 au and geocentric distance of 0.53 au. Bright comets allow for sensitive observations of gaseous volatiles that sublimate in their coma. These observations allowed us to detect HCN, CH 3 OH (multiple transitions), H 2 CO and CO, and to measure precise molecular production rates. Additionally, sensitive upper limits were derived on the complex molecules acetaldehyde (CH 3 CHO) and formamide (NH 2 CHO) based on the average of the strongest lines in the targeted spectral range to improve the signal-to-noise ratio. Gas production rates are derived using a non-LTE molecular excitation calculation involving collisions with H 2 O and radiative pumping that becomes important in the outer coma due to solar radiation. We find a depletion of CO in C/2014 Q2 (Lovejoy) with a production rate relative to water of 2.0 %, and relatively low abundances of Q(HCN)/Q(H 2 O), 0.1 %, and Q(H 2 CO)/Q(H 2 O), 0.2 %. In contrast the CH 3 OH relative abundance Q(CH 3 OH)/Q(H 2 O), 2.2 %, is close to the mean value observed in other comets. The measured production rates are consistent with values derived for this object from other facilities at similar wavelengths taking into account the difference in the fields of view. Based on the observed mixing ratios of organic molecules in four bright comets including C/2014 Q2, we find some support for atom addition reactions on cold dust being the origin of some of the molecules.

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Section: Discussionmentioning

confidence: 56%

Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope

Val-Borro

Milam

Cordiner

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Comets are small bodies that are thought to have formed in the early protoplanetary disk. They are believed to contain unmodified materials since their formation (Willacy et al 2015). For this reason, studying them helps to decipher the physical and chemical conditions that prevailed during planetesimal formation at about 4.6 billion years ago.…”

Section: Introductionmentioning

confidence: 99%

H/C elemental ratio of the refractory organic matter in cometary particles of 67P/Churyumov-Gerasimenko

Isnard

Bardyn

Fray

et al. 2019

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Context. Because comets are part of the most primitive bodies of our solar system, establishing their chemical composition and comparing them to other astrophysical bodies gives new constraints on the formation and evolution of organic matter throughout the solar system. For two years, the time-of-flight secondary ion mass spectrometer COmetary Secondary Ion Mass Analyzer (COSIMA) on board the Rosetta orbiter performed in situ analyses of the dust particles ejected from comet 67P/Churyumov-Gerasimenko (67P). Aims. The aim is to determine the H/C elemental ratio of the refractory organic component contained in cometary particles of 67P. Methods. We analyzed terrestrial and extraterrestrial calibration samples using the COSIMA ground-reference model. Exploiting these calibration samples, we provide calibration lines in both positive and negative ion registration modes. Thus, we are now able to measure the cometary H/C elemental ratio. Results. The mean H/C value is 1.04 ± 0.16 based on 33 different cometary particles. Consequently, the H/C atomic ratio is on average higher in cometary particles of 67P than in even the most primitive insoluble organic matter extracted from meteorites. Conclusions. These results imply that the refractory organic matter detected in dust particles of 67P is less unsaturated than the material in meteorites.

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“…Residing in the cold regions, these objects have undergone little change from the time of their formation. Thus their internal composition likely contains records of physical and chemical conditions prevailing at early stages of the solar system (Lowry et al 2008;Willacy et al 2015;Guilbert-Lepoutre et al 2015;Mandt et al 2015). Currently we know two main reservoirs of primitive comet-like bodies: the trans-Neptunian region and the Oort cloud.…”

Section: Introductionmentioning

confidence: 99%

Physical activity of the selected nearly isotropic comets with perihelia at large heliocentric distance

Kulyk

Rousselot

Корсун

et al. 2018

A&A

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Context. The systematic investigation of comets in a wide range of heliocentric distances can contribute to a better understanding of the physical mechanisms that trigger activity at large distances from the Sun and reveals possible differences in the composition of outer solar system bodies belonging to various dynamical groups. Aims. We seek to analyze the dust environment of the selected nearly isotropic comets with a perihelion distance between 4.5 and 9.1 au, where sublimation of water ice is considered to be negligible. Methods. We present results of multicolor broadband photometric observations for 14 distant active objects conducted between 2008 and 2015 with various telescopes. Images obtained with broadband filters were used to investigate optical colors of the cometary comae and to quantify physical activity of the comet nuclei. Results. The activity level was estimated with Afρ parameters ranging between 95 ± 10 cm and 9600 ± 300 cm. Three returning comets were less active than the dynamically new comets. Dust production rates of the comet nuclei were estimated between 1 and 100 kg s−1 based on some assumptions about the physical properties of dust particles populating comae. The measured colors point out reddening of the continuum for all the comets. The mean values of a normalized reflectivity gradient within the group of the comets amount to 14 ± 2% per 1000 Å and 3 ± 2% per 1000 Å in the BV and VR spectral domains, respectively. The comae of the dynamically new comets, which were observed on their inbound legs, may be slightly redder in the blue spectral interval than comae of the comets observed after the perihelion passages. The dynamically new comets observed both pre- and post-perihelion, seem to have higher production rates post-perihelion than pre-perihelion for similar heliocentric distances.

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The Composition of the Protosolar Disk and the Formation Conditions for Comets

Cited by 50 publications

References 207 publications

Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope

Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope

H/C elemental ratio of the refractory organic matter in cometary particles of 67P/Churyumov-Gerasimenko

Physical activity of the selected nearly isotropic comets with perihelia at large heliocentric distance

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