Decimetre dust aggregates in protoplanetary discs

Abstract

The growth of planetesimals is an essential step in planet formation. Decimetre-size dust agglomerates mark a transition point in this growth process. In laboratory experiments we simulated the formation, evolution, and properties of decimetre-scale dusty bodies in protoplanetary discs. Small sub-mm size dust aggregates consisting of micron-size SiO${}_2$ particles randomly interacted with dust targets of varying initial conditions in a continuous sequence of independent collisions. Impact velocities were 7.7 m/s on average and in the range expected for collisions with decimetre bodies in protoplanetary discs. The targets all evolved by forming dust \emph{crusts} with up to several cm thickness and a unique filling factor of 31% $\pm$3%. A part of the projectiles sticks directly. In addition, some projectile fragments slowly return to the target by gravity. All initially porous parts of the surface, i.e. built from the slowly returning fragments, are compacted and firmly attached to the underlying dust layers by the subsequent impacts. Growth is possible at impact angles from 0${}^{\circ }$ (central collision) to 70${}^{\circ }$. No growth occurs at steeper dust surfaces. We measured the velocity, angle, and size distribution of collision fragments. The average restitution coefficient is 3.8% or 0.29 m/s ejection velocity. Ejecta sizes are comparable to the projectile sizes. The high filling factor is close to the most compact configuration of dust aggregates by local compression ($\sim 33$%). This implies that the history of the surface formation and target growth is completely erased. In view of this, the filling factor of 31% seems to be a universal value in the collision experiments of all self-consistently evolving targets at the given impact velocities. We suggest that decimetre and probably larger bodies can simply be characterised by one single filling factor.

10 pages, 9 figures

References in corpus (4)

• Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
• Dust coagulation in protoplanetary disks: porosity matters
• High Velocity Dust Collisions: Forming Planetesimals in a Fragmentation Cascade with Final Accretion
• The Physics of Protoplanetesimal Dust Agglomerates II. Low Velocity Collision Properties

Cited by in corpus (24)

• The outcome of protoplanetary dust growth: pebbles, boulders, or planetesimals? I. Mapping the zoo of laboratory collision experiments
• Planetesimal formation by sweep-up: How the bouncing barrier can be beneficial to growth
• Dust evolution in protoplanetary discs and the formation of planetesimals. What have we learned from laboratory experiments?
• Comets formed in solar-nebula instabilities! -- An experimental and modeling attempt to relate the activity of comets to their formation process (corrigendum included)
• Wind-shearing in gaseous protoplanetary disks and the evolution of binary planetesimals
• Porosities of Protoplanetary Dust Agglomerates from Collision Experiments
• The Physics of Protoplanetesimal Dust Agglomerates. V. Multiple Impacts of Dusty Agglomerates at Velocities Above the Fragmentation Threshold
• Preplanetary scavengers: Growing tall in dust collisions
• Growth and fragmentation of centimetre-sized dust aggregates: the dependence on aggregate size and porosity
• Experiments on centimeter-sized dust aggregates and their implications for planetesimal formation
• Macroscopic Dust in Protoplanetary Disks - From Growth to Destruction
• Understanding planet formation using microgravity experiments
• Impact Angle Influence in High Velocity Dust Collisions during Planetesimal Formation
• Colliding Decimetre Dust
• Formation of Comets
• Ice aggregate contacts at the nm-scale
• Crossing barriers in planetesimal formation: The growth of mm-dust aggregates with large constituent grains
• Gravitoviscous protoplanetary disks with a dust component. III. Evolution of gas, dust, and pebbles
• Collisions of small ice particles under microgravity conditions
• The physics of protoplanetesimal dust agglomerates. X. High-velocity collisions between small and large dust agglomerates as growth barrier
• The four-populations model: a new classification scheme for pre-planetesimal collisions
• Formation of Terrestrial Planets
• Formation of pebbles in (gravito-)viscous protoplanetary disks with various turbulent strengths
• A Mechanism to Produce the Small Dust Observed in Protoplanetary Disks