Airfall on Comet 67P/Churyumov–Gerasimenko

Davidsson, B.; Birch, Samuel; Blake, Geoffrey A.; Bodewits, Dennis; Dworkin, Jason P.; Glavin, Daniel P.; Furukawa, Yoshihiro; Lunine, Jonathan I.; Mitchell, J. L.; Nguyen, A. N.; Squyres, S. W.; Takigawa, Aki; Vincent, J. B.; Zacny, K.

doi:10.1016/j.icarus.2020.114004

Cited by 34 publications

(39 citation statements)

References 94 publications

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“…Migliorini, A. et al 2016;Gasc et al 2017) discovered spatial and temporal variations in the coma H 2 O/CO 2 ratios, implying non-uniform mixing ratios for these two volatiles within the nucleus. As shown by Davidsson et al (2021Davidsson et al ( , 2022 for 67P, this could be caused by physical/chemical evolution of the comet's surface layers due to anisotropic illumination of the comet, but primordial variations in the H 2 O/CO 2 ratio intrinsic to the nucleus are also possible. It is therefore plausible that CH 3 OH in C/2016 R2 exists as a component within an apolar ice matrix dominated by CO and CO 2 , and some of this CH 3 OH is released into the coma when CO sublimates (as observed).…”

Section: Comparison With Previous Observations Of This Cometmentioning

confidence: 99%

A SUBLIME 3D Model for Cometary Coma Emission: the Hypervolatile-Rich Comet C/2016 R2 (PanSTARRS)

Cordiner,

Coulson,

Garcia-Berrios

et al. 2022

Preprint

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The coma of comet C/2016 R2 (PanSTARRS) is one of the most chemically peculiar ever observed, in particular due to its extremely high CO/H 2 O and N + 2 /H 2 O ratios, and unusual trace volatile abundances. However, the complex shape of its CO emission lines, as well as uncertainties in the coma structure and excitation, has lead to ambiguities in the total CO production rate. We performed high resolution, spatially, spectrally and temporally resolved CO observations using the James Clerk Maxwell Telescope (JCMT) and Submillimeter Array (SMA) to elucidate the outgassing behaviour of C/2016 R2. Results are analyzed using a new, time-dependent, three dimensional radiative transfer code (SUBLIME), incorporating for the first time, accurate state-to-state collisional rate coefficients for the CO-CO system. The total CO production rate was found to be in the range (3.8 − 7.6) × 10 28 s −1 between 2018-01-13 and 2018-02-01, with a mean value of (5.3 ± 0.6) × 10 28 s −1 at r H = 2.8-2.9 au. The emission is concentrated in a near-sunward jet, with an outflow velocity 0.51±0.01 km s −1 , compared to 0.25 ± 0.01 km s −1 in the ambient (and night-side) coma. Evidence was also found for an extended source of CO emission, possibly due to icy grain sublimation around 1.2 × 10 5 km from the nucleus. Based on the coma molecular abundances, we propose that the nucleus ices of C/2016 R2 can be divided into a rapidly sublimating apolar phase, rich in CO, CO 2 , N 2 and CH 3 OH, and a predominantly frozen (or less abundant), polar phase containing more H 2 O, CH 4 , H 2 CO and HCN.

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Section: Comparison With Previous Observations Of This Cometmentioning

confidence: 99%

A SUBLIME 3D Model for Cometary Coma Emission: the Hypervolatile-Rich Comet C/2016 R2 (PanSTARRS)

Cordiner,

Coulson,

Garcia-Berrios

et al. 2022

Preprint

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“…As explained in Section 4.1, grain fragmentation can cause a steepening or a shallowing of the radial profile slope depending on the composition of the grain. Depending on the icy-grain environments, such as quick fragmentation of icy grains, sublimation of icy grain, or even icy-grain mantling, for example, could result in different radial profiles provided that the icy grains survive long enough (e.g., Beer et al 2006;Markkanen & Agarwal 2020;Davidsson et al 2021). This, combined with the radar measurements, suggests that if icy grains were present in either 45P/HMP, 46P/Wirtanen, or both, an icy dust halo could be present, creating a shallowing of the radial profile slope.…”

Section: Dust Grain Behavior's Effects On Radial Profilesmentioning

confidence: 99%

Radial Distribution of the Dust Comae of Comets 45P/Honda–Mrkos–Pajdus̆áková and 46P/Wirtanen

Lejoly¹,

Harris²,

Samarasinha³

et al. 2022

Planet. Sci. J.

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There was an unprecedented opportunity to study the inner dust coma environments, where the dust and gas are not entirely decoupled, of comets 45P/Honda–Mrkos–Pajdus̆áková (45P/HMP) from 2016 December 26 to 2017 March 15, and 46P/Wirtanen from 2018 November 10 to 2019 February 13, both in visible wavelengths. The radial profile slopes of these comets were measured in the R and HB-BC filters most representative of dust, and deviations from a radially expanding coma were identified as significant. The azimuthally averaged radial profile slope of comet 45P/HMP gradually changes from −1.81 ± 0.20 at 5.24 days preperihelion to −0.35 ± 0.16 at 74.41 days postperihelion. Contrastingly, the radial profile slope of 46P/Wirtanen stays fairly constant over the observed time period at −1.05 ± 0.05. Additionally, we find that the radial profile of 46P/Wirtanen is azimuthally dependent on the sky-plane-projected solar position angle, while that of 45P/HMP is not. These results suggest that comets 45P/HMP and 46P/Wirtanen have vastly different coma dust environments and that their dust expansion properties are distinct. As evident from these two comets, well-resolved inner comae are vital for detailed characterization of dust environments.

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“…However, this model may be oversimplified and physical parameters related to the particle bed and boulder could not be derived. Additionally, Davidsson et al (2020) suggested a net accumulation of air fall material in this region of up to 3.6 m based on a numerical model including orbit dynamics, thermophysics of the nucleus, and hydrodynamics of the gas flow. In the following, we complement our measurements A2, page 3 of 15 A&A 662, A2 (2022)…”

Section: Bedform Description and Distributionmentioning

confidence: 99%

Discrete Element Modeling of Aeolian-like Morphologies on Comet 67P/Churyumov-Gerasimenko

Sachse¹,

Kappel²,

Tirsch³

et al. 2022

A&A

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Context. Even after the Rosetta mission, some of the mechanical parameters of comet 67P/Churyumov-Gerasimenko’s surface material are still not well constrained. They are needed to improve our understanding of cometary activity or for planning sample return procedures. Aims. We discuss the physical process dominating the formation of aeolian-like surface features in the form of moats and wind taillike bedforms around obstacles and investigate the mechanical and geometrical parameters involved. Methods. By applying the discrete element method (DEM) in a low-gravity environment, we numerically simulated the dynamics of the surface layer particles and the particle stream involved in the formation of aeolian-like morphological features. The material is composed of polydisperse spherical particles that consist of a mixture of dust and water ice, with interparticle forces given by the Hertz contact model, cohesion, friction, and rolling friction. We determined a working set of parameters that enables simulations to be reasonably realistic and investigated morphological changes when modifying these parameters. Results. The aeolian-like surface features are reasonably well reproduced using model materials with a tensile strength on the order of 0.1–1 Pa. Stronger materials and obstacles with round shapes impede the formation of a moat and a wind tail. The integrated dust flux required for the formation of moats and wind tails is on the order of 100 kg m−2, which, based on the timescale of morphological changes inferred from Rosetta images, translates to a near-surface particle density on the order of 10−6–10−4 kgm−3. Conclusions. DEM modeling of the aeolian-like surface features reveals complex formation mechanisms that involve both deposition of ejected material and surface erosion. More numerical work and additional in situ measurements or sample return missions are needed to better investigate mechanical parameters of cometary surface material and to understand the mechanics of cometary activity.

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Airfall on Comet 67P/Churyumov–Gerasimenko

Cited by 34 publications

References 94 publications

A SUBLIME 3D Model for Cometary Coma Emission: the Hypervolatile-Rich Comet C/2016 R2 (PanSTARRS)

A SUBLIME 3D Model for Cometary Coma Emission: the Hypervolatile-Rich Comet C/2016 R2 (PanSTARRS)

Radial Distribution of the Dust Comae of Comets 45P/Honda–Mrkos–Pajdus̆áková and 46P/Wirtanen

Discrete Element Modeling of Aeolian-like Morphologies on Comet 67P/Churyumov-Gerasimenko

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