Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session E4: Geophysics and Planetary Science II: Giant and Super-Earth Planets |
Hide Abstracts |
Chair: Lowell Miyagi, Yale University Room: Renaissance Ballroom C |
Monday, June 27, 2011 4:00PM - 4:15PM |
E4.00001: Chemical processes in the interior of giant planets Sebastien Hamel, Alfredo Correa, Eric Schwegler The unusual magnetic fields of the planets Uranus and Neptune represent important observables for constraining and developing deep interior models. Models suggests that the non-dipolar and non-axial magnetic fields of these planets originate from a thin convective and conducting shell of material around a stably stratified fluid core. We present a computational study of the physical properties of a fluid compositionally similar to what is expected in the interior of Uranus and Neptune. Our diffusivity and conductivity results suggest that the core cannot be well mixed if it is to generate non-axisymmetric magnetic fields. The simulations highlight the importance of chemistry on the properties of this complex mixture, including the possible formation of carbon and nitrogen clusters. We present results concerning the overall phase stability of the mixture under conditions relevant to the planetary interiors. [Preview Abstract] |
Monday, June 27, 2011 4:15PM - 4:30PM |
E4.00002: Structure of Fe and Carbon near 10 Mbar Federica Coppari, Jon Eggert, Ryan Rygg, Jim Hawreliak, Damien Hicks, Tom Boehly, Gilbert Collins Recent advances combining shockless dynamic compression, x-ray diffraction, and wave profiles now provides information on the structure, texture, and equation of state for solids at pressures up to 10 Mbar. We report new data on ramp compressed Fe to 7 Mbar and carbon starting from the diamond phase to 6 Mbar. Diffraction data are compared to simulated diffraction profiles to show consistency with specific high pressure crystal structures and give estimates for the density. The wave profiles are used to determine the pressure that the diffraction data are collected. [Preview Abstract] |
Monday, June 27, 2011 4:30PM - 5:00PM |
E4.00003: Exploring Extra-Solar Planetary Interiors: New Chemistry at Extreme Conditions Invited Speaker: The physical and transport properties of silicate and oxide melts at extreme pressures and temperatures are critical for understanding early planetary evolution and the aftermath of late-stage giant impacts such as that believed to have formed the Moon. Here we report on a suite of laser-driven shock experiments on major mineral phases of significance to the terrestrial mantle and extra-solar rocky planets SiO2, MgO and MgSiO3. Experiments on two polymorphs of SiO2 were used to validate experimental technique and are compared to previous results. We extend Hugoniot equation of state measurements for MgO and MgSiO3 to 6.4 and 9.5 Mbar, respectively, constraining controversial predications for the ultra-high pressure melt curves. Experiments on amorphous and crystalline MgSiO3 starting materials show the first evidence of a liquid-liquid phase transition with a volume reduction of 5-8{\%} near 3.5 Mbar and over a range of temperature of at least 7000 K, suggesting the potential for unexpectedly complex chemistry in silicate liquids. Transport properties are extracted from time-resolved optical reflectivity data and imply that the distinction between silicate and metallic constituents are blurred in deep planetary interiors with potential implications for coupling across the present-day core-mantle boundary. [Preview Abstract] |
Monday, June 27, 2011 5:00PM - 5:15PM |
E4.00004: Shock Compression of MgO: The Melt Transition Dawn G. Flicker, Seth Root, Luke Shulenburger, Thomas R. Mattsson Magnesium Oxide (MgO) is a highly stable material that melts at temperatures above 3000 K at ambient pressure. It is abundantly found in the Earth's mantle and is likely to be an important constituent of exo-planets, including ``super earths'' with higher inner pressures. However, little data exist at extreme pressures and temperatures and the current phase diagram is not well defined. To further examine the MgO phase diagram, we performed shock compression experiments using Sandia's Z -- accelerator to measure the Hugoniot to stresses greater than 10 Mbar and gain insight on the melt transition. In addition, we performed Density Functional Theory (DFT) simulations to examine the behavior of MgO under shock compression, calculating the Hugoniot with particular emphasis on the transition from solid to liquid. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of the Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Monday, June 27, 2011 5:15PM - 5:30PM |
E4.00005: Possible magnetic fields generated in oxides in Super Earths W.J. Nellis Planetary magnetic fields are generated by convective motion of conducting fluids. The highest pressure on oxides in Earth is about 130 GPa (1.3 Mbar) at about 3000 K at the core-mantle boundary. At these conditions electrical conductivities and viscosities of solid oxides are too small and large, respectively, to produce a significant contribution to Earth's magnetic field. However, oxides in super-Earth exoplanets reach interior pressures and temperatures much larger than those in Earth. Recent work has shown that solid Al2O3 is highly disordered up to $\sim $400 GPa and probably becomes a metallic glass with minimum metallic conductivity (MMC) at $\sim $300 GPa under both shock and static compression. MMC is essentially independent of material and so all oxides might behave this way. This insulator-metal transition is probably entropy-driven by energy absorbed in breaking chemical bonds, which leads to metallic energy bands. Since Al2O3 is estimated to melt on the Hugoniot at $\sim $400 GPa, viscosity is expected to decrease near this pressure. Depending on existence and nature of dynamos, the possibility exists that many extrasolar rocky planets have finite external magnetic fields without fluid Fe cores. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700