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Title: 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 protoplanetary 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 protoplanetary environments. Previous experiments often yielded apparently contradictory results on collision outcomes, only agreeing in a temperature dependence setting in above ≈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 ≈10 to ≈30 Å (≈2.5 to 12 bilayers) proves increased molecular mobility at temperatures above ≈210 K. Becausemore » 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.« less

Authors:
;  [1]; ; ;  [2]; ; ;  [3];
  1. School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)
  2. Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig (Germany)
  3. ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX (United Kingdom)
Publication Date:
OSTI Identifier:
22679753
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 848; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; AGGLOMERATION; COLLISIONS; ICE; LAYERS; MELTING; NEUTRON DIFFRACTION; NEUTRONS; NITROGEN; PLANETS; PROTOPLANETS; SATELLITES; SIMULATION; SUBLIMATION; SURFACES; TEMPERATURE DEPENDENCE; TEMPERATURE GRADIENTS

Citation Formats

Gärtner, S., Fraser, H. J., Gundlach, B., Ratte, J., Blum, J., Headen, T. F., Youngs, T. G. A., Bowron, D. T., Oesert, J., and Gorb, S. N., E-mail: sabrina.gaertner@stfc.ac.uk, E-mail: helen.fraser@open.ac.uk. Micrometer-sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8C7F.
Gärtner, S., Fraser, H. J., Gundlach, B., Ratte, J., Blum, J., Headen, T. F., Youngs, T. G. A., Bowron, D. T., Oesert, J., & Gorb, S. N., E-mail: sabrina.gaertner@stfc.ac.uk, E-mail: helen.fraser@open.ac.uk. Micrometer-sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties. United States. https://doi.org/10.3847/1538-4357/AA8C7F
Gärtner, S., Fraser, H. J., Gundlach, B., Ratte, J., Blum, J., Headen, T. F., Youngs, T. G. A., Bowron, D. T., Oesert, J., and Gorb, S. N., E-mail: sabrina.gaertner@stfc.ac.uk, E-mail: helen.fraser@open.ac.uk. 2017. "Micrometer-sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties". United States. https://doi.org/10.3847/1538-4357/AA8C7F.
@article{osti_22679753,
title = {Micrometer-sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties},
author = {Gärtner, S. and Fraser, H. J. and Gundlach, B. and Ratte, J. and Blum, J. and Headen, T. F. and Youngs, T. G. A. and Bowron, D. T. and Oesert, J. and Gorb, S. N., E-mail: sabrina.gaertner@stfc.ac.uk, E-mail: helen.fraser@open.ac.uk},
abstractNote = {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 protoplanetary 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 protoplanetary environments. Previous experiments often yielded apparently contradictory results on collision outcomes, only agreeing in a temperature dependence setting in above ≈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 ≈10 to ≈30 Å (≈2.5 to 12 bilayers) proves increased molecular mobility at temperatures above ≈210 K. Because 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.},
doi = {10.3847/1538-4357/AA8C7F},
url = {https://www.osti.gov/biblio/22679753}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 848,
place = {United States},
year = {2017},
month = {10}
}