Transport Characteristics of the Near-Surface Layer of the Nucleus of Comet 67P/Churyumov–Gerasimenko

Reshetnyk, V.; Skorov, Yu. V.; Vasyuta, M.; Bentley, Mark; Rezac, Ladislav; Agarwal, Jessica; Blum, J.

doi:10.1134/s0038094621020040

Cited by 11 publications

(2 citation statements)

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“…Skorov et al [221] showed that heterogeneous microstructures of dust layers can be neglected, so that effectively a homogeneous dust layer is a valid assumption for modelling outgassing. Further modelling of the transport characteristics was performed by Reshetnyk et al [222], which is useful for the application to comet observations.…”

Section: Comparison To Observationsmentioning

confidence: 99%

Formation of Comets

2022

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Questions regarding how primordial or pristine the comets of the solar system are have been an ongoing controversy. In this review, we describe comets’ physical evolution from dust and ice grains in the solar nebula to the contemporary small bodies in the outer solar system. This includes the phases of dust agglomeration, the formation of planetesimals, their thermal evolution and the outcomes of collisional processes. We use empirical evidence about comets, in particular from the Rosetta Mission to comet 67P/Churyumov–Gerasimenko, to draw conclusions about the possible thermal and collisional evolution of comets.

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Section: Comparison To Observationsmentioning

confidence: 99%

Formation of Comets

2022

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“…Skorov et al 2022 [221] showed that heterogeneous microstructures of dust layers can be neglected, so that effectively a homogeneous dust layer is a valid assumption for modelling outgassing. Further modelling of the transport characteristics was performed by Reshetnyk et al 2021 [222], which is useful for the application to comet observations.…”

Section: Comparison To Observationsmentioning

confidence: 99%

Formation of Comets

Blum,

Bischoff,

Gundlach

2022

Preprint

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Questions regarding how primordial or pristine the comets of the solar system are have been an ongoing controversy. In this review, we describe comets' physical evolution from dust and ice grains in the solar nebula to the contemporary small bodies in the outer solar system. This includes the phases of dust agglomeration, the formation of planetesimals, their thermal evolution and the outcomes of collisional processes. We use empirical evidence about comets, in particular from the Rosetta Mission to comet 67P/Churyumov-Gerasimenko, to draw conclusions about the possible thermal and collisional evolution of comets.Keywords comets; formation of planetesimals; evolution of planetesimals IntroductionComets are believed to be the most pristine objects of our solar system. They consist of several ices, mainly water ice but also super-volatiles such as CO or CO 2 ice, as well as refractory materials such as minerals, organics and salts. This composition obviously results in cometary gas and dust if the insolation is intense enough. In principle, a comet becomes dust-active if the outgassing rate is large enough to release dust particles against holding forces such as gravity and cohesion [1]. However, the exact physical mechanism of the ejection of dust is not yet well understood. Additionally, several aspects of the formation and evolutionary pathways of comets are still under debate. In this work, we provide a detailed overview of how icy planetesimals may have formed in the protoplanetary disc (PPD) and may have evolved into present-day bodies of the solar system, including comets. In Figure 1, we provide a graphical overview of the formation and evolutionary stages from protoplanetary dust to the contemporary small bodies in the solar system; we explain the stages in detail in the following sections. A more detailed version of Figure 1 can be found at https://www.tu-braunschweig.de/fileadmin/Redaktionsgruppen/Institute_Fakultaet_5/ IGEP/AG_Blum/Comet_Formation.pdf (accessed on 5 May 2022) and in the Supplementary Materials. In Section 2, the coagulation processes of the dust and ice particles are summarised, beginning with an overview of protoplanetary discs. In this work, we use the nomenclature proposed by Güttler et al. 2019 [2]. When referring to particles, their sizes are not further constrained. However, (dust or ice) grains are restricted to the (sub-)micrometre size range and are assumed to be homogeneously composed of one material only. Agglomerates consist of grains and can be heterogeneous in composition. The hit-and-stick growth of particles stops at growth barriers where pebbles, millimetre-to decimetresized porous agglomerates, are formed. Section 3 discusses the formation of planetesimals from pebbles via streaming instability and subsequent gravitational collapse. The required properties of the particles and the protoplanetary disc, as well as other scenarios, are briefly discussed. The different evolutionary processes that can alter the formed planetesimals are then presented in Section 4. The forma...

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Dynamics and potential origins of decimeter-sized particles around comet 67P/Churyumov-Gerasimenko

Pfeifer,

Agarwal,

Marschall

et al. 2024

A&A

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One of the primary goals of the European Space Agency's Rosetta mission to comet 67P/Churyumov-Gerasimenko was to investigate the mechanisms responsible for cometary activity. Our aim is to learn more about the ejection process of large refractory material by studying the dynamics of decimeter-sized dust particles in the coma of 67P and estimating their potential source regions. We algorithmically tracked thousands of individual particles through four OSIRIS/NAC image sequences of 67P's near-nucleus coma. We then traced concentrated particle groups back to the nucleus surface, and estimated their potential source regions, size distributions, and projected dynamical parameters. Finally, we compared the observed activity to dust coma simulations. We traced back 409 decimeter-sized particles to four suspected source regions. The regions strongly overlap and are mostly confined to the Khonsu-Atum-Anubis area. The activity may be linked to rugged terrain, and the erosion of fine dust and the ejection of large boulders may be mutually exclusive. Power-law indices fitted to the particle size--frequency distributions range from $3.4 0.3$ to $3.8 0.4$. Gas drag fits to the radial particle accelerations provide an estimate for the local gas production rates ( $Q_ g Our findings strongly suggest that the observed ejection of decimeter-sized particles cannot be explained by water ice sublimation and favorable illumination conditions alone. Instead, the local structures and compositions of the source regions likely play a major role. In line with current ejection models of decimeter-sized particles, we deem an overabundance of CO2 ice and its sublimation to be the most probable driver. In addition, because of the significant initial velocities, we suspect the ejection events to be considerably more energetic than gradual liftoffs.

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Transport Characteristics of the Near-Surface Layer of the Nucleus of Comet 67P/Churyumov–Gerasimenko

Cited by 11 publications

References 47 publications

Formation of Comets

Formation of Comets

Formation of Comets

Dynamics and potential origins of decimeter-sized particles around comet 67P/Churyumov-Gerasimenko

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