Estimating the strength of the nucleus material of comet 67P Churyumov–Gerasimenko

Basilevsky, A. T.; Krasilnikov, S. S.; Shiryaev, A. A.; Keller, H. U.; Skorov, Yu. V.; Mottola, S.; Hviid, S. F.

doi:10.1134/s0038094616040018

Cited by 25 publications

(15 citation statements)

References 25 publications

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“…In addition to three dust analyzers, OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) also provide images of the nucleus as well as dust particles. Based on the OSIRIS images, the tensile strength of comet 67P is estimated (Groussin et al 2015;Basilevsky et al 2016). Recently, Tatsuuma et al (2019) studied the tensile strength of dust aggregates and found that the tensile strength of comet 67P is reproduced when the monomer radius is between 3.3 − 220 µm.…”

Section: Comparison With Cometary Dust In the Solar Systemmentioning

confidence: 99%

Unveiling Dust Aggregate Structure in Protoplanetary Disks by Millimeter-wave Scattering Polarization

Tazaki

Tanaka

Kataoka

et al. 2019

ApJ

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Dust coagulation in a protoplanetary disk is the first step of planetesimal formation. However, the pathway from dust aggregates to planetesimals remains unclear. Both numerical simulations and laboratory experiments have suggested the importance of dust structure in planetesimal formation, but it is not well constrained by observations. We study how the dust structure and porosity alters polarimetric images at millimeter wavelength by performing 3D radiative transfer simulations. Aggregates with different porosity and fractal dimension are considered. As a result, we find that dust aggregates with lower porosity and/or higher fractal dimension are favorable to explain the observed millimeter-wave scattering polarization of disks. Although we cannot rule out the presence of aggregates with extremely high porosity, a population of dust particles with relatively compact structure is at least necessary to explain polarized-scattered waves. In addition, we show that particles with moderate porosity show weak wavelength dependence of scattering polarization, indicating that multi-wavelength polarimetry is useful to constrain dust porosity. Finally, we discuss implications for dust evolution and planetesimal formation in disks.

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Section: Comparison With Cometary Dust In the Solar Systemmentioning

confidence: 99%

Unveiling Dust Aggregate Structure in Protoplanetary Disks by Millimeter-wave Scattering Polarization

Tazaki

Tanaka

Kataoka

et al. 2019

ApJ

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“…In addition, this mission will deploy a rover to the surface of Phobos that will be the first demonstration of locomotion on a regolith-covered, low-gravity planetary surface (Murdoch et al 2020), and will provide an excellent opportunity for studying regolith dynamics on small body surfaces (Sunday et al 2020a). Despite the numerous successes described above, difficulties have also been encountered during the critical phase of landing or touching the surface of a small body, as demonstrated by the unintentional rebounding of Philae on the comet 67P/Churyumov-Gerasimenko in 2014 (Reinhard & Lars 2016;Basilevsky et al 2016), and the failed landing of the Hayabusa surface package MINERVA (Biele et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Low-velocity impacts into granular material: application to small-body landing

Murdoch

Drilleau

Sunday

et al. 2021

Monthly Notices of the Royal Astronomical Society

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With the flourishing number of small body missions that involve surface interactions, understanding the mechanics of spacecraft - surface interactions is crucial for improving our knowledge about the landing phases of space missions, for preparing spacecraft operations, and for interpreting the results of measurements made during the surface interactions. Given their regolith-covered surfaces, the process of landing on a small body can be considered as an impact at low-velocity onto a granular material in reduced-gravity. In order to study the influence of the surface material, projectile shape, and gravity on the collision dynamics we used two experimental configurations (one for terrestrial gravity experiments and one for reduced-gravity experiments) to perform low-velocity collisions into different types of granular materials: quartz sand, and two different sizes of glass beads (1.5 and 5 mm diameter). Both a spherical and a cubic projectile (with varying impact orientation) were used. The experimental data support a drag model for the impact dynamics composed of both a hydrodynamic drag force and quasi-static resistance force. The hydrodynamic and quasi-static contributions are related to the material frictional properties, the projectile geometry, and the gravity. The transition from a quasi-static to a hydrodynamical regime is shown to occur at lower impact velocities in reduced-gravity trials than in terrestrial gravity trials, indicating that regolith has a more fluid-like behaviour in low-gravity. The reduced quasi-static regime of a granular material under low-gravity conditions leads to a reduction in the strength, resulting in a decreased resistance to penetration and larger penetration depths.

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“…The consolidated surface layer mainly observed in 67P's southern hemisphere is probably extremely tough with a uniaxial compressive strength of >2 MPa (Spohn et al 2015), presumably as a result of sintering of water ice components of the surface layer material, but the compressive strength of the granular airfall material covering the northern hemisphere is only ∼1-3 kPa Article published by EDP Sciences A19, page 1 of 22 A&A 641, A19 2020with a shear strength of 4-30 Pa (Biele et al 2015;Groussin et al 2015;Basilevsky et al 2016). The size and arrangement of fracture polygons on the consolidated surfaces also hint at a strength in the MPa range (Auger et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Discrete element modeling of boulder and cliff morphologies on comet 67P/Churyumov-Gerasimenko

Kappel

Sachse

Haack

et al. 2020

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 not yet well constrained. These parameters are needed to improve our understanding of cometary activity or for planning sample return missions. Aims. We study some of the physical processes involved in the formation of selected surface features and investigate the mechanical and geometrical parameters involved. Methods. Applying the discrete element method (DEM) in a low-gravity environment, we numerically simulated the surface layer particle dynamics involved in the formation of selected morphological features. The material considered is a mixture of polydisperse ice and dust spheres with inter-particle forces given by the Hertz contact model, translational friction, rolling friction, cohesion from unsintered contacts, and optionally due to bonds from ice sintering. We determined a working set of parameters that enables the simulations to be reasonably realistic and investigated morphological changes due to modifications thereof. Results. The selected morphological features are reasonably well reproduced using model materials with a tensile strength on the order of 1–10 Pa. Increasing the diameters of the spherical particles decreases the material strength, and increasing the friction leads to a more brittle but somewhat stronger material. High friction is required to make the material sufficiently brittle to match observations, which points to the presence of very rough, even angular particles. Reasonable seismic activity does not suffice to trigger the collapses of cliffs without material heterogeneities or structural defects. Conclusions. DEM modeling can be a powerful tool to investigate mechanical parameters of cometary surface material. However, many uncertainties arise from our limited understanding of particle shapes, spatial configurations, and size distributions, all on multiple length scales. Further numerical work, in situ measurements, and sample return missions are needed to better understand the mechanics of cometary material and cometary activity.

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Estimating the strength of the nucleus material of comet 67P Churyumov–Gerasimenko

Cited by 25 publications

References 25 publications

Unveiling Dust Aggregate Structure in Protoplanetary Disks by Millimeter-wave Scattering Polarization

Unveiling Dust Aggregate Structure in Protoplanetary Disks by Millimeter-wave Scattering Polarization

Low-velocity impacts into granular material: application to small-body landing

Discrete element modeling of boulder and cliff morphologies on comet 67P/Churyumov-Gerasimenko

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