Geodynamic mantle modeling and its relation to origin and preservation of life

Abstract

Section 1 refers to hypotheses on the origin of life. These different hypotheses require distinct geodynamic and structural-geology prerequisites. For example, in case of chemoautotrophic metabolism-first hypotheses, a plate-tectonic mechanism is necessary that contains sites of reducing volcanic exhalations. It was shown that the mass extinctions of biological species are influenced by the convection-differentiation mechanism of the endogenic evolution of the Earth’s mantle. Especially LIP-producing eruptions appear to be the principal reason for mass extinction events. Occasionally, bolide impacts cause an extinction event in an ecologically stressed, LIP-generated situation. Section 2 reports on our efforts pertaining to the self-consistent modeling of plate tectonics. To facilitate platel ike motions, two conditions are required, namely a low-viscosity asthenosphere and a deviation from the purely viscous constitutive equation of the lithosphere. Our modeling results show that already relatively simple additional assumptions in a 3-D spherical-shell model of the Earth’s mantle produce oceanic lithospheric plates moving along the Earth’s surface and changing their shape and size as a function of time. Section 3 describes a new model of episodic growth of continental crust (CC). In the case of genetics-first hypotheses or of metabolism first hypotheses with solar irradiation or lightning energy supply, the existence of CC with epicontinental seas, lagoons and ponds is directly determining for the origin of life. Furthermore, the most important sources of nutrients originate from the upper CC. We put a water-concentration dependent solidus model of mantle peridotite into a 3-D spherical-shell, dynamic mantle model with chemical differentiation that redistributes the heat-producing elements. As a result, we obtain a set of temporal distributions of CC growth episodes that show a certain temporal invariance for a variation of the melting-criterion parameter, f3. The laterally averaged surface heat flow density qob, the Urey number Ur, and the kinetic creep energy Ekin show temporally sinusoidal components superposing a monotonously decreasing curve. Section 4 discusses partly unknown distributions of physical quantities, the knowledge of which is necessary for the computation of a dynamic Martian convection-differentiation system. It is ambiguous whether the early strong Martian magnetic dipole was generated by the more effective core cooling due to a platetectonic mode of solid-state convection in the Martian mantle during the first 500 Ma. Section 5 outlines the numerical progress in the advancement of the Terra code that was achieved by cooperation of the international group of Terra developers.