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Abstract Thermophysical properties of silicate liquids under extreme conditions are critical for understanding the accretion and evolution of super‐Earths and sub‐Neptunes. The thermal equation of state and viscosity of silicate liquids determine the adiabatic profiles and dynamics of magma oceans. However, these properties are challenging to constrain at elevated pressures in experiments. Here, we perform ab initio molecular dynamics simulations of MgSiO₃liquid across a wide range of pressures (0–1,200 GPa) and temperatures (2200–14000 K) and analyze its structure, the Grüneisen parameter, and viscosity. Our results reveal the clear temperature and pressure dependence of the Grüneisen parameter, which varies synchronously with the O‐O coordination number. The Grüneisen parameter shifts from positive to negative temperature dependence between ∼20 and 70 GPa, corresponding to a peak in the O‐O coordination number and SiO₅abundance. Initially, the Grüneisen parameter increases with pressure and then decreases, showing limited temperature dependence above ∼300 GPa, where its behavior resembles that of solids. Furthermore, we determine the adiabat and viscosity profiles of magma oceans in super‐Earths and sub‐Neptunes. The results suggest that the mantles of super‐Earths and sub‐Neptunes may solidify either from the bottom up or at pressures of ∼120–150 GPa, depending on the curvature of the mantle melting line. The low viscosity of magma oceans likely enhances convective currents and facilitate efficient differentiation. These thermophysical properties, now quantified up to terapascal pressures, enable updates to the mass‐radius relation of magma ocean exoplanets, showing notable differences compared to their solid counterparts. 

Abstract The precipitation of magnesium oxide (MgO) from the Earth's core has been proposed as a potential energy source to power the geodynamo prior to the inner core solidification. Yet, the stable phase and exact amount of MgO exsolution remain elusive. Here we utilize an iterative learning scheme to develop a unified deep learning interatomic potential for the Mg‐Fe‐O system valid over a wide pressure‐temperature range. This potential enables direct, large‐scale simulations of MgO exsolution processes at the Earth's core‐mantle boundary. Our results suggest that Mg exsolve in the form of crystalline Fe‐poor ferropericlase as opposed to a liquid MgO component presumed previously. The solubility of Mg in the core is limited, and the present‐day core is nearly Mg‐free. The resulting exsolution rate is small yet nonnegligible, suggesting that MgO exsolution may provide a potentially important energy source, although it alone may be difficult to drive an early geodynamo. 

Abstract Earth's accretion was highly energetic and likely involved multiple global melting events. Following the Moon‐forming giant impact, extensive mantle melting and the separation of solids and melts under deep mantle pressures likely produced a basal magma ocean (BMO) beneath the solidified mantle. The presence and evolution of the BMO have been proposed to explain key geophysical and geochemical features of the lowermost mantle. Understanding the evolution of the BMO is crucial for testing these hypotheses, but its interaction with the core presents a significant challenge, as the mechanism of this exchange remains unclear. In this study, we develop a theoretical framework to assess the regime of BMO‐core exchange based on the compositions of the BMO and the core. We propose that during solidification, the BMO may evolve into a regime where the reaction at the BMO‐core interface drives compositional convection in liquids on both sides, if the core has a high enough Si content (–, under the assumption that the O content is –). In this scenario, the BMO‐core exchange would be much more efficient than previously estimated, buffering the tendency of FeO enrichment during crystallization and shortening the lifetime of the BMO. 

Radiogenic heat production is fundamental to the energy budget of planets. Roughly half of the heat that Earth loses through its surface today comes from the three long-lived, heat-producing elements (potassium, thorium, and uranium). These three elements have long been believed to be highly lithophile and thus concentrate in the mantle of rocky planets. However, our study shows that they all become siderophile under the pressure and temperature conditions relevant to the core formation of large rocky planets dubbed super-Earths. Mantle convection in super-Earths is then primarily driven by heating from the core rather than by a mix of internal heating and cooling from above as in Earth. Partitioning these sources of radiogenic heat into the core remarkably increases the core-mantle boundary (CMB) temperature and the total heat flow across the CMB in super-Earths. Consequently, super-Earths are likely to host long-lived volcanism and strong magnetic dynamos. 

Abstract Metabolic scaling theory has been pivotal in formalizing the expected energy expenditures across populations as a function of body size. Coexistence theory has provided a mathematization of the environmental conditions compatible with multispecies coexistence. Yet, it has been challenging to explain how observed community‐wide patterns, such as the inverse relationship between population abundance density and body size, can be unified under both theories. Here, we provide the foundation for a tractable, scalable, and extendable framework to study the coexistence of resource‐mediated competing populations as a function of their body size. For a given thermal domain and response, this integration reveals that the metabolically predicted 1/4 power dependence of carrying capacity of biomass density on body size can be understood as the average distribution of carrying capacities across feasible environmental conditions, especially for large communities. In line with empirical observations, our integration predicts that such average distribution leads to communities in which population biomass densities at equilibrium are independent from body size, and consequently, population abundance densities are inversely related to body size. This integration opens new opportunities to increase our understanding of how metabolic scaling relationships at the population level can shape processes at the community level under changing environments. 

Abstract Hydrogen may be incorporated into nominally anhydrous minerals including bridgmanite and post‐perovskite as defects, making the Earth's deep mantle a potentially significant water reservoir. The diffusion of hydrogen and its contribution to the electrical conductivity in the lower mantle are rarely explored and remain largely unconstrained. Here we calculate hydrogen diffusivity in hydrous bridgmanite and post‐perovskite, using molecular dynamics simulations driven by machine learning potentials of ab initio quality. Our findings reveal that hydrogen diffusivity significantly increases with increasing temperature and decreasing pressure, and is considerably sensitive to hydrogen incorporation mechanism. Among the four defect mechanisms examined, (Mg + 2H)_Siand (Al + H)_Sishow similar patterns and yield the highest hydrogen diffusivity. Hydrogen diffusion is generally faster in post‐perovskite than in bridgmanite, and these two phases exhibit distinct diffusion anisotropies. Overall, hydrogen diffusion is slow on geological time scales and may result in heterogeneous water distribution in the lower mantle. Additionally, the proton conductivity of bridgmanite for (Mg + 2H)_Siand (Al + H)_Sidefects aligns with the same order of magnitude of lower mantle conductivity, suggesting that the water distribution in the lower mantle may be inferred by examining the heterogeneity of electrical conductivity. 

Abstract The recent JWST detections of carbon-bearing molecules in a habitable-zone sub-Neptune have opened a new era in the study of low-mass exoplanets. The sub-Neptune regime spans a wide diversity of planetary interiors and atmospheres not witnessed in the solar system, including mini-Neptunes, super-Earths, and water worlds. Recent works have investigated the possibility of gas dwarfs, with rocky interiors and thick H₂-rich atmospheres, to explain aspects of the sub-Neptune population, including the radius valley. Interactions between the H₂-rich envelope and a potential magma ocean may lead to observable atmospheric signatures. We report a coupled interior-atmosphere modeling framework for gas dwarfs to investigate the plausibility of magma oceans on such planets and their observable diagnostics. We find that the surface–atmosphere interactions and atmospheric composition are sensitive to a wide range of parameters, including the atmospheric and internal structure, mineral composition, volatile solubility and atmospheric chemistry. While magma oceans are typically associated with high-temperature rocky planets, we assess if such conditions may be admissible and observable for temperate sub-Neptunes. We find that a holistic modeling approach is required for this purpose and to avoid unphysical model solutions. Using our model framework, we consider the habitable-zone sub-Neptune K2-18 b as a case study and find that its observed atmospheric composition is incompatible with a magma ocean scenario. We identify key atmospheric molecular and elemental diagnostics, including the abundances of CO₂, CO, NH₃, and, potentially, S-bearing species. Our study also underscores the need for fundamental material properties for accurate modeling of such planets.