11:00 AM - 11:15 AM
[PPS07-25] The structure of mantle convection in super-Earths of various sizes
Keywords:super-Earths, mantle convection
In this paper, we show that how convective structure changes as the mass of the planet increases. In the Earth-like size planet, hot plume activity is high, but the activity is reduced as the planet mass increases. When Mp (the planet mass divided by the Earth’s mass) exceeds 4, hot plumes become faint compared with cold ones and their activity becomes negligible. The dimensional thickness of the lithosphere increases as Mp increases in spite of the increasing Rayleigh number. The rms velocity of thermal convection does not significantly depend on Mp. These results suggest that plate tectonics becomes harder to operate as Mp increases.
We also explored the initial transient stage of thermal convection in massive super-Earths. When the shallow mantle is initially hotter than expected from the adiabatic extrapolation from the deep mantle, as expected when the planet is formed from giant impact, transient layered convection continues for as long as several to ten billion years before it yields to a whole layer convection that occurs as the structure in the statistically steady state. Our results suggest that the interior of many of massive super-Earths may be still in the transient stage rather than the steady state now.