The Stickiness of Micrometer-Sized Water-Ice Particles

Gundlach, Bastian; Blum, Jürgen

doi:10.1088/0004-637x/798/1/34

Cited by 292 publications

(297 citation statements)

References 43 publications

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“…The accretion rate of these fluffy aggregates onto inner embryos could be greatly different from that of compact aggregates. Bounding and fragmentation of aggregates are also potentially important, but might not be crucial given the sticky nature of ice aggregates (see Wada et al 2009Wada et al , 2011Wada et al , 2013Gundlach & Blum 2015).…”

Section: Discussionmentioning

confidence: 99%

On the water delivery to terrestrial embryos by ice pebble accretion

Sato

Okuzumi

Ida

2016

A&A

171

197

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Standard accretion disk models suggest that the snow line in the solar nebula migrated interior to the Earth's orbit in a late stage of nebula evolution. In this late stage, a significant amount of ice could have been delivered to 1 AU from outer regions in the form of mm to dm-sized pebbles. This raises the question why the present Earth is so depleted of water (with the ocean mass being as small as 0.023% of the Earth mass). Here we quantify the amount of icy pebbles accreted by terrestrial embryos after the migration of the snow line assuming that no mechanism halts the pebble flow in outer disk regions. We use a simplified version of the coagulation equation to calculate the formation and radial inward drift of icy pebbles in a protoplanetary disk. The pebble accretion cross section of an embryo is calculated using analytic expressions presented by recent studies. We find that the final mass and water content of terrestrial embryos strongly depends on the radial extent of the gas disk, the strength of disk turbulence, and the time at which the snow lines arrives at 1 AU. The disk's radial extent sets the lifetime of the pebble flow, while turbulence determines the density of pebbles at the midplane where the embryos reside. We find that the final water content of the embryos falls below 0.023 wt% only if the disk is compact (<100 AU), turbulence is strong at 1 AU, and the snow line arrives at 1 AU later than 2-4 Myr after disk formation. If the solar nebula extended to 300 AU, initially rocky embryos would have evolved into icy planets of 1-10 Earth masses unless the snow-line migration was slow. If the proto-Earth contained water of ∼1 wt% as might be suggested by the density deficit of the Earth's outer core, the formation of the proto-Earth was possible with weaker turbulence and with earlier (>0.5-2 Myr) snow-line migration.

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Section: Discussionmentioning

confidence: 99%

On the water delivery to terrestrial embryos by ice pebble accretion

Sato

Okuzumi

Ida

2016

A&A

171

197

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“…where ρ peb is the density of the pebble itself (set to 1.5 g/cm 3 for water ice) and v f is the fragmentation velocity limit, where waterice particles have a higher fragmentation velocity of 10 m/s than silicate grains (Gundlach & Blum 2015). When we use only this fragmentation limit for icy particles, the Stokes numbers of the particles in our disc model are 0.01-0.2, which is slightly smaller than in the drift-limited case (shown in Fig.…”

Section: Stokes Numbers In the Planet Formation Modelmentioning

confidence: 99%

Pebble-isolation mass: Scaling law and implications for the formation of super-Earths and gas giants

Bitsch

Morbidelli

Johansen

et al. 2018

A&A

263

296

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The growth of a planetary core by pebble accretion stops at the so-called pebble isolation mass, when the core generates a pressure bump that traps drifting pebbles outside its orbit. The value of the pebble isolation mass is crucial in determining the final planet mass. If the isolation mass is very low, gas accretion is protracted and the planet remains at a few Earth masses with a mainly solid composition. For higher values of the pebble isolation mass, the planet might be able to accrete gas from the protoplanetary disc and grow into a gas giant. Previous works have determined a scaling of the pebble isolation mass with cube of the disc aspect ratio. Here, we expand on previous measurements and explore the dependency of the pebble isolation mass on all relevant parameters of the protoplanetary disc. We use 3D hydrodynamical simulations to measure the pebble isolation mass and derive a simple scaling law that captures the dependence on the local disc structure and the turbulent viscosity parameter α. We find that small pebbles, coupled to the gas, with Stokes number τ f < 0.005 can drift through the partial gap at pebble isolation mass. However, as the planetary mass increases, particles must be decreasingly smaller to penetrate the pressure bump. Turbulent diffusion of particles, however, can lead to an increase of the pebble isolation mass by a factor of two, depending on the strength of the background viscosity and on the pebble size. We finally explore the implications of the new scaling law of the pebble isolation mass on the formation of planetary systems by numerically integrating the growth and migration pathways of planets in evolving protoplanetary discs. Compared to models neglecting the dependence of the pebble isolation mass on the α-viscosity, our models including this effect result in higher core masses for giant planets. These higher core masses are more similar to the core masses of the giant planets in the solar system.

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“…In addition to studies of silica particles, the collisional behavior of water-ice particles was the subject of experimental study. These experiments showed that water-ice particles have an enlarged sticking regime, which is caused by the high surface energy of water (Gundlach & Blum 2015).…”

Section: Introductionmentioning

confidence: 97%

Influence of porosity on collisions between dust aggregates

Gunkelmann

Ringl

Urbassek

2016

A&A

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Context. Collisions between dust particles may lead to agglomerate growth or fragmentation, depending on the porosity of the dust and the collision velocity. Aims. We study the effect of agglomerate porosity and collision velocity on aggregate fragmentation and agglomeration. Methods. Granular-mechanics simulations are used to study the outcome of head-on dust aggregate collisions. The aggregates are composed of silica grains of 0.76 µm radius and have filling factors of between 0.08 and 0.21. The simulations incorporate repulsive and viscoelastic, dissipative normal forces, and intergrain adhesion. The tangential forces are composed of gliding, rolling, and torsional friction. To study the effect of aggregate porosity, we prepared spherical aggregates with identical radius but differing particle numbers. Results. The threshold velocity for agglomerate fragmentation decreases with the porosity of the aggregates. Porous aggregates tend to fragment more easily, and the fragments are irregularly shaped. In the agglomeration regime, the merged aggregate is more compact than the initial collision partners. The collision velocity at which compaction is highest is independent of the initial porosity.

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The Stickiness of Micrometer-Sized Water-Ice Particles

Cited by 292 publications

References 43 publications

On the water delivery to terrestrial embryos by ice pebble accretion

On the water delivery to terrestrial embryos by ice pebble accretion

Pebble-isolation mass: Scaling law and implications for the formation of super-Earths and gas giants

Influence of porosity on collisions between dust aggregates

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