Comets formed in solar-nebula instabilities! -- An experimental and modeling attempt to relate the activity of comets to their formation process (corrigendum included)

Abstract

When comet nuclei approach the Sun, the increasing energy flux through the surface layers leads to sublimation of the underlying ices and subsequent outgassing that promotes the observed emission of gas and dust. The ejection of dust requires that the forces binding the dust particles to the comet nucleus must be overcome by the forces caused by the sublimation process. This relates to the question of how large the tensile strength of the overlying dust layer is. Homogeneous layers of micrometer-sized dust particles reach tensile strengths of typically $10^3$ to $10^4$ Pa. This exceeds by far the maximum sublimation pressure of water ice in comets. It is therefore unclear how cometary dust activity is driven. To solve this paradox, we used the model by Skorov and Blum (Icarus 221, 1-11, 2012), who assumed that cometesimals formed by gravitational instability of a cloud of dust and ice aggregates and calculated for the corresponding structure of comet nuclei tensile strength of the dust-aggregate layers on the order of 1 Pa. Here we present evidence that the emitted cometary dust particles are indeed aggregates with the right properties to fit the model by Skorov and Blum. Then we experimentally measure the tensile strengths of layers of laboratory dust aggregates and confirm the values derived by the model. To explain the comet activity driven by the evaporation of water ice, we derive a minimum size for the dust aggregates of $\sim 1$ mm, in agreement with meteoroid observations and dust-agglomeration models in the solar nebula. Finally we conclude that cometesimals must have formed by gravitational instability, because all alternative formation models lead to higher tensile strengths of the surface layers.

The pdf file includes the main document and the corrigendum to the main article (just scroll through the pdf)

References in corpus (7)

• Comets formed in solar-nebula instabilities! -- An experimental and modeling attempt to relate the activity of comets to their formation process (corrigendum included)
• High Velocity Dust Collisions: Forming Planetesimals in a Fragmentation Cascade with Final Accretion
• The Physics of Protoplanetesimal Dust Agglomerates. IV. Towards a Dynamical Collision Model
• The Physics of Protoplanetesimal Dust Agglomerates II. Low Velocity Collision Properties
• Outburst activity in comets: II. A multi-band photometric monitoring of comet 29p/Schwassmann-Wachmann 1
• Cometary Dust Trail Associated with Rosetta Mission Target: 67P/Churyumov-Gerasimenko
• Decimetre dust aggregates in protoplanetary discs

Cited by in corpus (23)

• Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles
• Comets formed in solar-nebula instabilities! -- An experimental and modeling attempt to relate the activity of comets to their formation process (corrigendum included)
• Formation of pebble-pile planetesimals
• The thermal, mechanical, structural, and dielectric properties of cometary nuclei after Rosetta
• Ice Grain Collisions in Comparison: CO${}_2$, H${}_2$O and their Mixtures
• Experimental phase function and degree of linear polarization of cometary dust analogs
• Tensile Strength of Porous Dust Aggregates
• Submillimetre-sized dust aggregate collision and growth properties
• High precision meteor observations with the Canadian Automated Meteor Observatory -- Data reduction pipeline and application to meteoroid mechanical strength measurements
• Acceleration of cometary dust near the nucleus: Application to 67P/Churyumov-Gerasimenko
• Formation of Comets
• The role of pebble fragmentation in planetesimal formation II. Numerical simulations
• Local manifestations of cometary activity
• The footprint of cometary dust analogs: I. Laboratory experiments of low-velocity impacts and comparison with Rosetta data
• The tensile strength of compressed dust samples and the catastrophic disruption threshold of pre-planetary matter
• Thermal inertias of pebble-pile comet 67P/Churyumov-Gerasimenko
• Free Collisions in a Microgravity Many-Particle Experiment. IV. - Three-Dimensional Analysis of Collision Properties
• Comparing the reflectivity of ungrouped carbonaceous chondrites with that of short period comets like 2P/Encke
• Analog Experiments on Tensile Strength of Dusty and Cometary Matter
• Sub-mm/mm optical properties of real protoplanetary matter derived from Rosetta/MIRO observations of comet 67P
• A method to distinguish between micro- and macro-granular surfaces of small Solar System bodies
• TEMPus VoLA: the Timed Epstein Multi-pressure Vessel at Low Accelerations
• Revisiting sticking property of submillimetre-sized aggregates