Primitive noble gases sampled from ocean island basalts cannot be from the Earth's core

A deeper and hotter Martian core-mantle differentiation inferred from FeO partitioning

The core-mantle differentiation process plays a pivotal role in redistributing material on a massive scale, shaping the long-term evolution of rocky planets. Understanding this process is crucial for gaining insights into the accretion and evolution of planets like Mars. However, the details of Mars's core-mantle differentiation remain poorly understood due to limited compositional data for its core and mantle. In this study, we aim to constrain the Martian core-mantle differentiation by examining FeO partitioning between core and mantle materials, incorporating improved Martian compositional data from the InSight mission. Using ab initio thermodynamic techniques, we calculated the FeO partition coefficient between liquid iron and silicate melt. Our results align with previous studies while also clarifying the factors affecting partitioning behavior. Based on these findings and estimates of oxygen concentration in the core, we infer that Mars's core and mantle likely differentiated at temperatures above 2440 K and pressures ranging from 14 to 22 GPa. Although these estimates are higher than previously reported, they are consistent with observed abundances of moderately siderophile elements and Mars's accretion models.

Radiogenic heating sustains long-lived volcanism and magnetic dynamos in super-Earths

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.

Ab initio determination of melting and sound velocity of neon up to the deep interior of the Earth

The thermophysical properties and elemental abundances of the noble gases in terrestrial materials can provide unique insights into the Earth's evolution and mantle dynamics. Here, we perform extensive ab initio molecular dynamics simulations to determine the melting temperature and sound velocity of neon up to 370 GPa and 7500 K to constrain its physical state and storage capacity, together with to reveal its implications for the deep interior of the Earth. It is found that solid neon can exist stably under the lower mantle and inner core conditions, and the abnormal melting of neon is not observed under the entire temperature (T) and pressure (P) region inside the Earth owing to its peculiar electronic structure, which is substantially distinct from other heavier noble gases. An inspection of the reduction for sound velocity along the Earth's geotherm evidences that neon can be used as a light element to account for the low-velocity anomaly and density deficit in the deep Earth. A comparison of the pair distribution functions and mean square displacements of MgSiO3-Ne and Fe-Ne alloys further reveals that MgSiO3 has a larger neon storage capacity than the liquid iron under the deep Earth condition, indicating that the lower mantle may be a natural deep noble gas storage reservoir. Our results provide valuable information for studying the fundamental behavior and phase transition of neon in a higher T-P regime, and further enhance our understanding for the interior structure and evolution processes inside the Earth.

Highest terrestrial 3He/4He credibly from the core

The observation that many lavas associated with mantle plumes have higher 3He/4He ratios than the upper convecting mantle underpins geophysical, geodynamic and geochemical models of Earth's deep interior. High 3He/4He ratios are thought to derive from the solar nebula or from solar-wind-irradiated material that became incorporated into Earth during early planetary accretion. Traditionally, this high-3He/4He component has been considered intrinsic to the mantle, having avoided outgassing caused by giant impacts and billions of years of mantle convection1-4. Here we report the highest magmatic 3He/4He ratio(67.2 ± 1.8 times the atmospheric ratio) yet measured in terrestrial igneous rocks, in olivines from Baffin Island lavas. We argue that the extremely high-3He/4He helium in these lavas might derive from Earth's core5-9. The viability of the core hypothesis relaxes the long-standing constraint-based on noble gases in lavas associated with mantle plumes globally-that volatile elements from the solar nebula have survived in the mantle since the early stages of accretion.