Comet formation in collapsing pebble clouds

Lorek, S.; Gundlach, Bastian; Lacerda, Pedro; Blum, J.

doi:10.1051/0004-6361/201526565

Cited by 59 publications

(70 citation statements)

References 56 publications

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“…As shown in Fig. 1, the pressure-porosity relations resulting from these parameters (for low, medium and high strength; Table 1) covers very well the range of experimental curves for dust agglomerates (Güttler et al 2009) and ice pebbles (Lorek et al 2016).…”

Section: Modeling Approachsupporting

confidence: 65%

“…Crush curve parameters P e and P s (Jutzi et al 2008), density of matrix material ρ s0 , initial bulk density ρ 0 , density of the compacted material ρ compact , initial distention α 0 , bulk modulus A, friction coefficient µ, cohesion Y 0 , average tensile strength Y T . Pressure-porosity relation (high strength) Pressure-porosity relation (medium strength) Pressure-porosity relation (low strength) Dust agglomerates (3D); Guetller et al, 2009 Ice pebbles (quasi 3D); Lorek et al, 2016 Fig. 1.…”

Section: Modeling Approachmentioning

confidence: 99%

“…Pressure-porosity relations (crush curve) used in the simulations for the three different sets of parameters (low, medium, high strength) as defined in Table 1. Also shown are the results from laboratory experiments dust agglomerates (Güttler et al 2009) and ice pebbles (Lorek et al 2016). …”

Section: Modeling Approachmentioning

confidence: 99%

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How primordial is the structure of comet 67P?

Jutzi

Benz

Τόλιου

et al. 2016

A&A

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Context. There is an active debate about whether the properties of comets as observed today are primordial or, alternatively, if they are a result of collisional evolution or other processes. Aims. We investigate the effects of collisions on a comet with a structure like 67P/Churyumov-Gerasimenko (67P). We develop scaling laws for the critical specific impact energies Q reshape required for a significant shape alteration. These are then used in simulations of the combined dynamical and collisional evolution of comets in order to study the survival probability of a primordially formed object with a shape like 67P. Although the focus of this work is on a structure of this kind, the analysis is also performed for more generic bi-lobe shapes, for which we define the critical specific energy Q bil . The simulation outcomes are also analyzed in terms of impact heating and the evolution of the porosity. Methods. The effects of impacts on comet 67P are studied using a state-of-the-art smooth particle hydrodynamics shock physics code. In the 3D simulations, a publicly available shape model of 67P is applied and a range of impact conditions and material properties are investigated. The resulting critical specific impact energy Q reshape (as well as Q bil for generic bi-lobe shapes) defines a minimal projectile size which is used to compute the number of shape-changing collisions in a set of dynamical simulations. These simulations follow the dispersion of the trans-Neptunian disk during the giant planet instability, the formation of a scattered disk, and produce 87 objects that penetrate into the inner solar system with orbits consistent with the observed JFC population. The collisional evolution before the giant planet instability is not considered here. Hence, our study is conservative in its estimation of the number of collisions. Results. We find that in any scenario considered here, comet 67P would have experienced a significant number of shape-changing collisions, if it formed primordially. This is also the case for generic bi-lobe shapes. Our study also shows that impact heating is very localized and that collisionally processed bodies can still have a high porosity. Conclusions. Our study indicates that the observed bi-lobe structure of comet 67P may not be primordial, but might have originated in a rather recent event, possibly within the last 1 Gy. This may be the case for any kilometer-sized two-component cometary nuclei.

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Section: Modeling Approachsupporting

confidence: 65%

Section: Modeling Approachmentioning

confidence: 99%

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How primordial is the structure of comet 67P?

Jutzi

Benz

Τόλιου

et al. 2016

A&A

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“…These planetesimals are expected to be composed of a high fraction of dust (silicates), which may explain why the rock-to-ice fractions inferred in minor planets and moons in the outer solar system (e.g., Schubert et al 2010) or the dust-to-ice ratio in comets (e.g., Rotundi et al 2015;Lorek et al 2016) are often significantly higher than the expected 1/2 to 1/3 value obtained from purely solar composition (e.g., Lodders 2003).…”

Section: Discussionmentioning

confidence: 99%

Formation of dust-rich planetesimals from sublimated pebbles inside of the snow line

Ida

Guillot

2016

A&A

106

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Context. For up to a few millions of years, pebbles must provide a quasi-steady inflow of solids from the outer parts of protoplanetary disks to their inner regions. Aims. We wish to understand how a significant fraction of the pebbles grows into planetesimals instead of being lost to the host star. Methods. We examined analytically how the inward flow of pebbles is affected by the snow line and under which conditions dust-rich (rocky) planetesimals form. When calculating the inward drift of solids that is due to gas drag, we included the back-reaction of the gas to the motion of the solids. Results. We show that in low-viscosity protoplanetary disks (with a monotonous surface density similar to that of the minimum-mass solar nebula), the flow of pebbles does not usually reach the required surface density to form planetesimals by streaming instability. We show, however, that if the pebble-to-gas-mass flux exceeds a critical value, no steady solution can be found for the solid-to-gas ratio. This is particularly important for low-viscosity disks (α < 10 −3 ) where we show that inside of the snow line, silicate-dust grains ejected from sublimating pebbles can accumulate, eventually leading to the formation of dust-rich planetesimals directly by gravitational instability.Conclusions. This formation of dust-rich planetesimals may occur for extended periods of time, while the snow line sweeps from several au to inside of 1 au. The rock-to-ice ratio may thus be globally significantly higher in planetesimals and planets than in the central star.

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“…The errors denote one standard deviation of the perihelion distances. The data were taken from the JPL Small-Body Database and the work by Kim et al (2014, their calculations have shown that the collision speeds during the collapse are low enough to not destroy the collapsing aggregates during collisons (Wahlberg Jansson & Johansen 2014;Lorek et al 2016).…”

Section: Introductionmentioning

confidence: 99%