HR: 09:48h
AN: MR11A-08    [Abstracts]
TI: Experimental and Computational Studies of Planetary Ices.
AU: * Fortes, A D
EM: andrew.fortes@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
AU: Vocadlo, L
EM: l.vocadlo@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
AU: Wood, I G
EM: ian.wood@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
AU: Grindrod, P M
EM: p.grindrod@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
AU: Brand, H E
EM: h.brand@ucl.ac.uk
AF: Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
AU: Gromnitskaya, E L
EM: grom@hppi.troitsk.ru
AF: Vereschagin Institute for High Pressure Physics, Moscow Region, Troitsk, 142092, Russian Federation
AU: Lyapin, A G
EM: alyapin@hppi.troitsk.ru
AF: Vereschagin Institute for High Pressure Physics, Moscow Region, Troitsk, 142092, Russian Federation
AU: Yagafarov, O F
EM: oyagafarov@hppi.roitsk.ru
AF: Vereschagin Institute for High Pressure Physics, Moscow Region, Troitsk, 142092, Russian Federation
AB: Planetary bodies are essentially crystalline aggregates. Underlying the structure and evolution of all such bodies is the microscopic behaviour of the component crystals – their equilibrium structures, elasticity, and transport properties, for example. Determining the magnitudes of these properties for the different ‘ices' and for the highly hydrated phases thought to exist in the interiors of outer solar-system moons requires a coordinated multidisciplinary approach involving a combination of experimental and computational techniques. All of the substances of interest exhibit complex polymorphism over the range of pressures and temperatures found in the largest icy moons; however, apart from the case of water ice, little is known about the existence and stability fields of these numerous polymorphs. We employ traditional piston-cylinder methods to map the loci of phase boundaries, whilst simultaneously measuring density, bulk modulus and shear modulus. In addition, high-pressure powder neutron diffraction data provide the basis for the solution of high-pressure crystal structures as well as the measurement of thermal expansion tensors and incompressibilities. If the crystal structures are known, it is possible to carry out quantum mechanical calculations to determine a range of physical properties. We present new calculations of the elastic properties of triclinic meridianiite (MgSO₄.11H₂O), and use the example of epsomite (MgSO₄.7H₂O) to illustrate our confidence in the accuracy of the calculations as well as the synergy between the experimental and computational methods. Determining the rheology of planetary ices at very low strain rates is critical to the success of planetary evolution modeling. We describe experimental techniques using neutron diffraction which may allow the diffusion creep regime of water ice to be observed, and discuss the status of quantum mechanical calculations of this process.
DE: 3902 Creep and deformation
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
DE: 6020 Ices
DE: 6045 Physics and chemistry of materials
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting