Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session P62: Physics of Planetary Interiors: Modeling Planets From Atomic to Global ScaleInvited Undergraduate
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Sponsoring Units: DCOMP GSCCM Chair: Philip Armitage, JILA Room: BCEC 258C |
Wednesday, March 6, 2019 2:30PM - 3:06PM |
P62.00001: What Juno and Cassini have told us about Giant Planet interiors Invited Speaker: David Stevenson Juno is in orbit about Jupiter and will likely continue collecting data for several more years. Cassini collected data during close encounters within the Saturn ring plane for several months in 2017. The main source of information is the gravity data and magnetic field data, augmented in the case of Juno by microwave radiometry data that inform us about atmospheric composition, a key boundary condition for the interior. Juno gravity indicates that the innermost part of Jupiter is enriched in heavy elements (everything heavier than H and He), perhaps ot the extent of around 10 or 15 Earth masses (~5% of the planet mass) but this enrichment is not in the form of a discrete core but is instead diluted by the overlying H and He. This is consistent with current ideas for planet formation, where very high temperatures lead to evaporation and mixing of incoming solids. The distribution of heavier elements in the region where hydrogen begins to metallize is less clear and may be affected by and entangled with the possible rain-out of helium. Saturn, unlike Jupiter, benefits from ring seismology: the existence of ring structure that must be attributed to density anomalies within the planet. In both Jupiter and Saturn, the region of magnetic field generation extends out beyond the metallic hydrogen region in to primarily molecular hydrogen that is sufficiently hot and compressed that it has significant conduction electrons. Coupling of the magnetic field to the zonal flow extends out further still, to a region where the electrical conductivity is of order 1 S/m. Although there has been much improvement in our understanding of H-He, the uncertainties, both in theory and experiment, remain large enough that they limit our ability to make full use of the spacecraft results. We need experiments at relevant temperatures and pressures, since most current experiments are either too hot or too cold at the pressures of importance. |
Wednesday, March 6, 2019 3:06PM - 3:42PM |
P62.00002: Setting the stage: dynamics of planet formation and water delivery Invited Speaker: Sean Raymond In addition to our Solar System, exoplanet systems provide a sample of thousands of outcomes of planet formation. Even though Jupiter is the only Solar System planet likely to be detected with present-day technology, the past decade of observations has shown that the Solar System is quantifiably unusual among exoplanet systems at the ~1% level. Instead, at least half of main sequence stars host close-in "super-Earths", and ~10% have Jupiters on non-Jupiter-like orbits. In this talk I will explore how the Solar System fits in a larger context by addressing key steps in planetary system formation. I will present models to explain the diversity of observed planetary systems and the mechanisms that create that diversity. I will focus on the processes that create a diversity in planetary compositions and formation times, with a particular emphasis on the origin of water. While there is as yet no consensus on exactly how the Solar System formed it is clear that Jupiter played a central role. |
Wednesday, March 6, 2019 3:42PM - 4:18PM |
P62.00003: Imaging the Earth's Interior based on Seismic Full Waveform Inversion Invited Speaker: Jeroen Tromp Information about Earth's interior comes from seismograms recorded at its surface. Seismic imaging based on spectral-element and adjoint-state methods has enabled assimilation of this information for the construction of 3D (an)elastic Earth models. These methods account for the physics of wave excitation and propagation by numerically solving the equations of motion, and require the execution of complex computational procedures that challenge the most advanced high-performance computing systems. Current research is petascale; future research will require exascale capabilities. Our research addresses the long-standing challenge of imaging Earth’s interior based on full-waveform inversion. What we mean by `full-waveform inversion' is combining 3D forward simulations with Fréchet derivatives computed in 3D background models to fit complete three-component seismograms both in phase (traveltime) and amplitude. |
Wednesday, March 6, 2019 4:18PM - 4:54PM |
P62.00004: Spin crossover in iron in lower mantle minerals Invited Speaker: Renata Wentzcovitch Pressure and temperature induced spin-state change in iron in lower mantle minerals is an unusual phenomenon with previously unknown consequences. High pressure and high temperature experiments have offered a wealth of new information about this class of materials problems, which includes the insulator to metal transition in Mott systems. I will discuss key experimental data, contrast them with our ab initio results and thermodynamic models, show the implications for fundamental phenomena taking place at the atomic scale and their macroscopic manifestations, and discuss potential geophysical consequences of this phenomenon. |
Wednesday, March 6, 2019 4:54PM - 5:30PM |
P62.00005: Numerical Simulations of Mantle Convection and Plate Tectonics in the Earth and Planets: From Magma Oceans to Present Day Invited Speaker: Paul J Tackley The coupled system of convection of the Earth’s solid mantle and plate tectonics is the driver of geological change on our planet, including continental drift, volcanoes, earthquakes, crustal production, atmospheric degassing the recycling, and cooling of the core, which drives the geodynamo. Modelling of this process is challenging due to the wide range of length scales (from faults to continents) and time scales (seconds to billions of years) and the complex rheology of rocks, which exhibit visco-elasto-plastic behaviour with strongly temperature-dependent viscosity varying by orders of magnitude over short length scales. Nevertheless, it is now routine to perform global-scale 3-D spherical simulations that span the 4.5 billion year age of our planet and contain complex effects such as partial melting and crustal production and solid-solid phase transitions. |
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