Geodynamics of Super‐Earth GJ 486b

• Published in: Journal of geophysical research. Planets 2024-10, Vol.129 (10), p.n/a
• Main Authors: Meier, Tobias G., Bower, Dan J., Lichtenberg, Tim, Hammond, Mark, Tackley, Paul J., Pierrehumbert, Raymond T., Caballero, José A., Tsai, Shang‐Min, Weiner Mansfield, Megan, Tosi, Nicola, Baumeister, Philipp
• Format: Article
• Language: English
• Subjects: Atmosphere; Atmospheric circulation; Climate models; Convection; Convection patterns; Degassing; Earth; Earth mantle; Extrasolar planets; Geodynamics; Global climate; Global climate models; Heat transport; Hemispheres; interiors; Lithosphere; Locking; Magma; mantle convection; Planetary composition; Planetary mantles; Planets; Plate tectonics; Solar system; Stars; super‐Earths; Surface temperature; Tectonic processes; tectonic regimes; Tectonics; Temperature; Terrestrial planets; Upwelling
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2024JE008491

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 toward 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 $R=1.34$ R⊕ ${R}_{\oplus }$, M=3.0 $M=3.0$ M⊕ ${M}_{\oplus }$, Teq≈700 ${\mathrm{T}}_{\text{eq}}\approx 700$ 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 favored for strong temperature contrasts between the dayside and nightside and higher surface temperatures. Plain Language Summary The tectonic processes occurring on super‐Earths, which are rocky exoplanets with masses exceeding that of Earth, may differ significantly from those observed on the terrestrial planets in our solar system. Many super‐Earths are also expected to be tidally locked to their host star, so that always the same hemisphere faces the star. Tidal locking can lead to a strong temperature contrast between the dayside and nightside surface. Here, we investigate the influence of such strong surface temperature contrasts on the interior dynamics and tectonic behavior of super‐Earth GJ 486b, which is one of the best characterized Earth‐mass planets to date. We