Planetary Mantle Dynamics

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Heat loss from the terrestrial planets in our solar system is governed by convection in their outer silicate shells. In the case of the Earth, this convection is manifested as plate tectonics and the continental drift that results. The research encompassed in this proposal will focus on the thermal evolution of planetary interiors and the feedback between surface and interior dynamics. The methodology will focus on utilizing computer models of two- and three-dimensional convecting fluids contained within either self-gravitating spherical shells or plane-layer systems. Motivation for a substantial amount of the proposed activity derives from the observation that the Earth is the only planet in the solar system featuring plate tectonics and our desire to understand why this is so. Specific topics of interest will include examining the influence of system geometry (i.e., mantle thickness) and particularly planetary core size on the thermal character of mantle convection. In addition, we shall investigate the influence of a mobile surface on mantle convection as well as the physical requirements for plate motion. The nature of the thermal evolution of rocky planets and icy moons will be explored by investigating the influence of fluid parameters (e.g., thermal viscosity dependence) on convection characteristics. Moreover, the role in planetary thermal evolution that may be played by continents and deep chemically distinct anomalies will drive a portion of the proposed work. Extension of the models and applications to exosolar planets will also be examined. The research is facilitated by utilizing sophisticated computational models run on distributed memory parallel computing platforms (i.e., utilizing many processors). Presently, a small planetary interiors group of four graduate students works under my guidance at the University of Toronto-Scarborough (UTSC) and benefits from access to the SciNet General Purpose Computing (GPC) Cluster. Over the past five years the research group has migrated all of the computer codes used for our research to SciNet's GPC. Consequently, all tools required for the research proposed here are already available, tested and ready to use. In addition, we are now utilizing codes developed at UTSC as well as new computer codes, obtained from collaborative ventures that are well suited to capitalize on SciNet's capabilities. This will enable the research projects described here to probe physical behaviour in regimes, and on time-scales, not previously accessible. For example, the codes and high performance computing facilities now available will allow researchers at UTSC to model planetary convection in systems featuring both the convective vigour and the surface area of an Earth-like planet over periods simulating billions of years of evolution. The underlying theme of all of these studies is investigation of the time-dependence of planetary heat loss and surface motion. The research involved will train highly qualified personnel (HQP) in the use of high performance computing for investigating problems in geophysical fluid dynamics. To undertake these projects , support for a group of six researchers is sought. Over the next five years, the general makeup of this group will include the Principal Investigator, a post-doctoral research assistant and four graduate students, engaged in both MSc and PhD studies. These HQP will be engaged in international collaborative research stemming from use of the computing tools required for the research. Funding would support the completion of six PhD and four MSc degrees and the HQP will complete their research projects having obtained experience that will include training as geodynamicists and exposure to the methods by which scientific results are disseminated.