HR: 1340h
AN: P33A-1015    [Abstracts]
TI: Scaling of plume formation on Mars
AU: * Ke, Y
EM: yke@levee.wustl.edu
AF: Department of Earth and Planetary Science, Washington University, Saint Louis, MO 63130
AU: Solomatov, V S
EM: slava@levee.wustl.edu
AF: Department of Earth and Planetary Science, Washington University, Saint Louis, MO 63130
AB: Various explanations were suggested in the past for one-plume pattern of Martain mantle convection. Here we look at the role of rheology and investigate the number of plumes as a function of the viscosity contrast across the thermal boundary layer at the core-mantle boundary. Plumes form as the result of the instability in the thermal boundary layer. Previous studies showed that such instability can approximately be described as a Rayleigh-Taylor instability. In order to have one-plume structures formed, the viscosity contrast has to be larger than 10$^4$ - 10$^5$, which is basically the same viscosity contrast at which small-scale convection begins in the thermal boundary layer. In this regime, the instability growth rate depends only weakly on the wavelength of perturbation. This means that the number of plumes can be determined by the spectrum of initial heterogeneities rather than by the fastest growing wavelength. Thus, the one-plume structure on Mars could be controlled by a single large-scale heterogeneity generated, for example, by a large early impact.
DE: 8125 Evolution of the Earth
DE: 5455 Origin and evolution
DE: 5749 Origin and evolution
DE: 6040 Origin and evolution
DE: 1060 Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting