Influence of early plate tectonics on the thermal evolution
and magnetic field of Mars
F. Nimmo and D. Stevenson,J. Geophys. Res., 105, 11969-11980, 2000.
Recent magnetic studies of Mars suggest that (1) it possessed a periodically reversing magnetic field for the first ~500 Myr of its existence and (2) plate tectonics
may have been operating during this time. On Earth the geodynamo is thought
to occur because of convection in the outer core. This paper estimates
the amount of heat the Martian core can conduct in the absence of convection.
It uses parameterized, variable-viscosity thermal evolution models to show
that the core heat flux increases if the planet's surface heat flux is
increased above the value required to eliminate instantaneous radiogenic
heat production. Conversely, a sudden reduction
in surface heat flux causes the mantle to heat up and the core heat flux to become negative. Thus, if plate tectonics, or some other process causing high surface
heat flux, was occurring on early Mars, it
is likely to have caused convection in the core and hence generated a
magnetic field. Conversely, a reduction in surface heat flux would probably have
caused the core to stop convecting and shut off the magnetic field. There is
thus an important link between surface processes and core magnetism, which
may also be relevant to planets such as Earth and Venus.
Francis' Page
Department of Earth Sciences
home page
nimmo@esc.cam.ac.uk
This page was last modified on 22 May 2000.