Subduction and accretion in a soft Venus without surface water.
Abstract
Water is often taken as a key-ingredient to allow Plate Tectonics and the continuous resurfacing of a planet, because it softens rocks rheology and lubricates faults and the subduction interface. This is certainly the case on Earth. But it does not imply that without water on its surface, a planet cannot sustain subduction. We systematically studied in the laboratory convection in complex rheology fluids and the conditions when it generates subduction, accretion, and plate tectonics. So far, aqueous colloidal dispersions are the only laboratory fluids capable of producing the sufficient shear localization to generate self-consistently asymmetric subduction and/or plate tectonics. It is worth noting that the strong and rapid deformation localization is due to their biphasic nature (water and a skeleton of silica nano-particles). This suggests that fluids are keys to produce Earth-like dynamics, and that not only surface water, but also melt, could provoke the sufficient deformation localization. This would explain well the present-day occurence of subduction around Venus large coronae. The experiments further predict trench roll-back, and associated accretion inside the coronae, with velocities that could reach 1 to 10 cm/yr. So, far from always being in a quiet stagnant lid regime, a Venus-type planet can sustain plenty of localized subduction/accretion events. Plate tectonics on a global scale is also seen to occur in laboratory experiments but its range of occurence is reduced when surface temperature becomes too high. Anyway, as the occurence of subduction or of plate tectonics is no garantie that water exists on an exoplanet surface, the absence of liquid water on an exoplanet surface does not mean that tectonic resurfacing is not occurring either.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P53A..08D
- Keywords:
-
- 5205 Formation of stars and planets;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 6295 Venus;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6296 Extra-solar planets;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS