Micrometer-Sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties

Abstract

Models and observations suggest that ice-particle aggregation at and beyond the snowline dominates the earliest stages of planet-formation, which therefore is subject to many laboratory studies. However, the pressure-temperature gradients in proto-planetary disks mean that the ices are constantly processed, undergoing phase changes between different solid phases and the gas phase. Open questions remain as to whether the properties of the icy particles themselves dictate collision outcomes and therefore how effectively collision experiments reproduce conditions in pro- toplanetary environments. Previous experiments often yielded apparently contradictory results on collision outcomes, only agreeing in a temperature dependence setting in above $\approx$ 210 K. By exploiting the unique capabilities of the NIMROD neutron scattering instrument, we characterized the bulk and surface structure of icy particles used in collision experiments, and studied how these structures alter as a function of temperature at a constant pressure of around 30 mbar. Our icy grains, formed under liquid nitrogen, undergo changes in the crystalline ice-phase, sublimation, sintering and surface pre-melting as they are heated from 103 to 247 K. An increase in the thickness of the diffuse surface layer from $\approx$ 10 to $\approx$ 30 Å ($\approx$ 2.5 to 12 bilayers) proves increased molecular mobility at temperatures above $\approx$ 210 K. As none of the other changes tie-in with the temperature trends in collisional outcomes, we conclude that the surface pre-melting phenomenon plays a key role in collision experiments at these temperatures. Consequently, the pressure-temperature environment, may have a larger influence on collision outcomes than previously thought.

12 pages, 5 figures

References in corpus (17)

• Observations of the Icy Universe
• Consistent dust and gas models for protoplanetary disks. I. Disk shape, dust settling, opacities, and PAHs
• The stickiness of micrometer-sized water-ice particles
• Fluffy dust forms icy planetesimals by static compression
• Imaging the water-snow line during a protostellar outburst
• The chemical history of molecules in circumstellar disks. I. Ices
• Micrometer-sized ice particles for planetary-science experiments - I. Preparation, critical rolling friction force, and specific surface energy
• Water formation at low temperatures by surface O2 hydrogenation II: the reaction network
• From dust to planetesimals: an improved model for collisional growth in protoplanetary disks
• Ice Grain Collisions in Comparison: CO${}_2$, H${}_2$O and their Mixtures
• Microgravity experiments on the collisional behavior of Saturnian ring particles
• Breaking the Ice: Planetesimal Formation at the Snowline
• Discovery of Crystallized Water Ice in a Silhouette Disk in the M43 Region
• Collisions of small ice particles under microgravity conditions
• Collisions between sintered icy aggregates
• Spatially resolved detection of crystallized water ice in a TTauri object
• Collisions of solid ice in planetesimal formation

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• Drifting inwards in protoplanetary discs II: The effect of water on sticking properties at increasing temperatures
• Transmission Electron Microscopy Study of the Morphology of Ices Composed of H2O, CO2, and CO on Refractory Grains
• Are Pebble Pile Planetesimals Doomed?
• Growth of Aggregates with Liquid-Like Ice-Shells in Protoplanetary Discs
• Thermal Desorption of H2O-Ice: From Nanoscale Films to the Bulk
• Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures
• A Pluto-Charon Concerto: An Impact on Charon as the Origin of the Small Satellites
• Dust evolution during the protostellar collapse: influence on the coupling between the neutral gas and the magnetic field
• Evading the dust fragmentation barrier with the streaming instability in protoplanetary disks