Geodynamics of super-Earth GJ 486b

Abstract

Many super-Earths are on very short orbits around their host star and, therefore, more likely to be tidally locked. Because this locking can lead to a strong contrast between the dayside and nightside surface temperatures, these super-Earths could exhibit mantle convection patterns and tectonics that could differ significantly from those observed in the present-day solar system. The presence of an atmosphere, however, would allow transport of heat from the dayside towards the nightside and thereby reduce the surface temperature contrast between the two hemispheres. On rocky planets, atmospheric and geodynamic regimes are closely linked, which directly connects the question of atmospheric thickness to the potential interior dynamics of the planet. Here, we study the interior dynamics of super-Earth GJ 486b ($R=1.34$ $R_{\oplus }$, $M=3.0$ $M_{\oplus }$, T${}_{\mathrm{eq}}\approx 700$ K), which is one of the most suitable M-dwarf super-Earth candidates for retaining an atmosphere produced by degassing from the mantle and magma ocean. We investigate how the geodynamic regime of GJ 486b is influenced by different surface temperature contrasts by varying possible atmospheric circulation regimes. We also investigate how the strength of the lithosphere affects the convection pattern. We find that hemispheric tectonics, the surface expression of degree-1 convection with downwellings forming on one hemisphere and upwelling material rising on the opposite hemisphere, is a consequence of the strong lithosphere rather than surface temperature contrast. Anchored hemispheric tectonics, where downwellings und upwellings have a preferred (day/night) hemisphere, is favoured for strong temperature contrasts between the dayside and nightside and higher surface temperatures.

36 pages, 13 figures, updated with version accepted for publication in JGR: Planets

References in corpus (21)

• Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• Inevitability of Plate Tectonics on Super-Earths
• High Tide or Riptide on the Cosmic Shoreline? A Water-Rich Atmosphere or Stellar Contamination for the Warm Super-Earth GJ~486b from JWST Observations
• Decomposing the Iron Cross-Correlation Signal of the Ultra-Hot Jupiter WASP-76b in Transmission using 3D Monte-Carlo Radiative Transfer
• An Atomic Spectral Survey of WASP-76b: Resolving Chemical Gradients and Asymmetries
• The rotational and divergent components of atmospheric circulation on tidally locked planets
• A nearby transiting rocky exoplanet that is suitable for atmospheric investigation
• The Equilibrium Temperature of Planets in Elliptical Orbits
• Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b
• Constraining mornings & evenings on distant worlds: a new semi-analytical approach and prospects with transmission spectroscopy
• A detailed analysis of the Gl 486 planetary system
• Plausible constraints on the range of bulk terrestrial exoplanet compositions in the Solar neighbourhood
• The Detectability of Rocky Planet Surface and Atmosphere Composition with JWST: The Case of LHS 3844b
• The Tectonics and Volcanism of Venus: New Modes Facilitated by Realistic Crustal Rheology and Intrusive Magmatism
• High-Resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b
• Interior dynamics of super-Earth 55 Cancri e
• A mineralogical reason why all exoplanets cannot be equally oxidising
• Redox state and interior structure control on the long-term habitability of stagnant-lid planets
• From stars to diverse mantles, melts, crusts and atmospheres of rocky exoplanets
• Super-Earth LHS3844b is tidally locked

Cited by in corpus (1)

• Constraining exoplanet interiors using observations of their atmospheres