The Potential for Plate Tectonics about Sun-like Stars in the Galaxy as Controlled by Composition
Abstract
Earth is the only known planet to host continuous, long term crustal subduction through plate tectonics. These dynamics are associated with planetary habitability due to its role in volcanism and the water and carbon cycles. The negative buoyancy of subducting plates is the main driver of plate tectonics, and is a consequence of the density contrast between the subducting crust and surrounding silicate mantle. This contrast is a function of both compositional and thermal differences between the crust and mantle. To date, as many as 230 terrestrial planets have been discovered, with increasing precision in the measurements of the physical properties of these planets. There is no observational method to detect plate tectonics in this sample of exoplanets. We therefore model the thermal and compositional state of terrestrial exoplanetary crusts and mantles assuming a genetic relationship between the host star and its planets. To produce these models, we use the MELTS/pMELTS (Ghiorso & Sack 1995, Ghiorso et al. 2002) and HeFESTo (Stixrude & Lithgow-Bertelloni 2011) thermodynamic mineral phase equilibria algorithms. From these calculations, we determine the density contrast between an exoplanet's potentially subducting basaltic crust and mantle by analyzing the cumulative negatively buoyant forces generated by crustal subduction. This allows us to analyze the likelihood for cold crust to founder and sink promoting dynamic mass flux within the solid planet. Based on a survey of 1111 Sun-like stars spanning a wide range of refractory element composition, we find that the silica content of the resulting mantle is a controlling factor in the likelihood for exoplantary crusts to sink through combined thermal and compositional factors. Therefore, we estimate that as few as 0.6% of all Sun-like stars are likely tohosting planets that undergo steady-state surface-to-interior crustal cycling. This approach therefore provides a method for identifying the most important planets for time-intensive follow up of atmospheric properties.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.P41B2077H
- Keywords:
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- 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5455 Origin and evolution;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 8147 Planetary interiors;
- TECTONOPHYSICS