Physicochemical Controls on the Compositions of the Earth and Planets
arXiv:2512.00373 · doi:10.1007/s11214-025-01243-w
Abstract
Despite the fact that the terrestrial planets formed from the protoplanetary disk, their compositions show marked departures from that of solar nebula condensates. Metallic cores fix oxygen fugacities (Os) of the planets to 5 (Mercury) to 1 log units below the iron-wüstite (IW) buffer, orders of magnitude higher than the nebular gas. Their oxidised character is coupled with a lack of volatile elements with respect to the solar nebula. Condensates from a solar gas at different temperatures () have Fe/O (by mass) of 0.93 ( = 1250 K) to 0.81 ( = 400 K), far lower than that of Earth (1.06). Because the reaction Fe(s) + H2O(g) = FeO(s) + H2(g) proceeds <600 K, temperatures at which most moderately volatile elements (MVEs) have condensed, oxidised planets should be volatile-rich, and vice-versa. That this is not observed suggests that planets did not accrete from equilibrium nebular condensates and/or underwent additional volatile depletion/O changes. Indeed, MVEs in small telluric bodies (Moon, Vesta) indicate near equilibrium evaporation/condensation at IW-1 and 1400-1800 K. Volatile-depleted elemental yet near-chondritic isotopes of larger telluric bodies (Earth, Mars) reflect mixing of bodies of variable volatile depletion, overprinted by volatile-undepleted material. From the Cr- and Ti isotopes in the BSE, such undepleted matter has been proposed to be CI chondrites. 6% CI added late to an enstatite chondrite-like proto-Earth would match the Earth. However, because Earth is an end-member in isotopic anomalies of heavier elements, no combination of existing meteorites alone can account for its chemical- and isotopic composition. Instead, the Earth is made partially or essentially entirely from an NC-like missing component. If so, the oxidised-, yet volatile-poor nature of inner solar system bodies, including Earth and Mars, is intrinsic to the NC reservoir.
References in corpus (66)
- Photoevaporation of protoplanetary discs II: evolutionary models and observable properties
- Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water
- Forming Planetesimals in Solar and Extrasolar Nebulae
- The Evolution of the Water Distribution in a Viscous Protoplanetary Disk
- Evolution of protoplanetary disks: Constraints from DM Tauri and GM Aurigae
- Protostellar disk formation and transport of angular momentum during magnetized core collapse
- Global simulations of protoplanetary disks with ohmic resistivity and ambipolar diffusion
- The structure of protoplanetary discs around evolving young stars
- Solar System Abundances of the Elements
- Disk Winds Driven by Magnetorotational Instability and Dispersal of Proto-Planetary Disks
- The great dichotomy of the Solar System: small terrestrial embryos and massive giant planet cores
- Global simulations of protoplanetary disks with net magnetic flux: I. Non-ideal MHD case
- The composition of Mars
- Why do protoplanetary disks appear not massive enough to form the known exoplanet population?
- Bifurcation of planetary building blocks during Solar System formation
- Turbulent Mixing and the Dead Zone in Protostellar Disks
- Evidence for a correlation between mass accretion rates onto young stars and the mass of their protoplanetary disks
- Planetary and meteoritic Mg/Si and d30Si variations inherited from solar nebula chemistry
- Convective Overstability in radially stratified accretion disks under thermal relaxation
- Directions of Outflows, Disks, Magnetic Fields, and Rotation of YSOs in Collapsing Molecular Cloud Cores
- Modal abundances of CAIs: Implications for bulk chondrite element abundances and fractionations
- Contemporary formation of early solar system planetesimals at two distinct radial locations
- Terrestrial planet formation from lost inner solar system material
- ALMA Reveals Transition of Polarization Pattern with Wavelength in HL Tau's Disk
- Planetesimal rings as the cause of the Solar System's planetary architecture
- 60Fe-60Ni chronology of core formation in Mars
- Dispersion in the lifetime and accretion rate of T Tauri discs
- Near-equilibrium isotope fractionation during planetesimal evaporation
- Thermally-driven atmospheric escape: Transition from hydrodynamic to Jeans escape
- Chemistry of Impact-Generated Silicate Melt-Vapor Debris Disks
- 3D Radiation Non-ideal Magnetohydrodynamical Simulations Of The Inner Rim In Protoplanetary Disks
- Stellar irradiated discs and implications on migration of embedded planets II: accreting-discs
- Gallium isotopic evidence for extensive volatile loss from the Moon during its formation
- The Chemical Composition of Mercury
- Compositional evolution during rocky protoplanet accretion
- Protoplanetary Disk Rings as Sites for Planetesimal Formation
- Volatile loss following cooling and accretion of the Moon revealed by chromium isotopes
- Anisotropic Infall and Substructure formation in Embedded Disks
- A Critical Examination of the X-Wind Model for Chondrule and Calcium-rich, Aluminum-rich Inclusion Formation and Radionuclide Production
- Temperature Structure in the Inner Regions of Protoplanetary Disks: Inefficient Accretion Heating Controlled by Nonideal Magnetohydrodynamics
- Early volatile depletion on planetesimals inferred from C-S systematics of iron meteorite parent bodies
- Isotopic evolution of the inner Solar System inferred from molybdenum isotopes in meteorites
- Leaky dust traps: How fragmentation impacts dust filtering by planets
- Scaling laws for the geometry of an impact-induced magma ocean
- Probing the Protosolar Disk Using Dust Filtering at Gaps in the Early Solar System
- Protoplanetary Disk Heating and Evolution Driven by the Spiral Density Waves
- Spin state and moment of inertia of Venus
- Convective outgassing efficiency in planetary magma oceans: insights from computational fluid dynamics
- The Metal-Silicate Partitioning of Carbon During Earth's Accretion and its Distribution in the Early Solar System
- Bayesian Inference on the Isotopic Building Blocks of Mars and Earth
- Solubility of Rock in Steam Atmospheres of Planets
- Collisional stripping of planetary crusts
- Accretion of the earliest inner solar system planetesimals beyond the water-snowline
- Stochastic accretion of the Earth
- Potassium Isotope Compositions of Carbonaceous and Ordinary Chondrites: Implications on the Origin of Volatile Depletion in the Early Solar System
- The Ni isotopic composition of Ryugu reveals a common accretion region for carbonaceous chondrites
- Chemical Equilibrium Calculations for Bulk Silicate Earth Material at High Temperatures
- An inflationary disk phase to explain extended protoplanetary dust disks
- Size and density sorting of dust grains in SPH simulations of protoplanetary discs
- Vapor-Melt Exchange -- Constraints on Chondrite Formation Conditions and Processes
- A Self-Consistent Model for Dust-Gas Coupling in Protoplanetary Disks
- Distribution of s-, r-, and p-process nuclides in the early Solar System inferred from Sr isotope anomalies in meteorites
- The cosmochemistry of planetary systems
- Maximum Temperatures in Evolving Protoplanetary Discs and Composition of Planetary Building Blocks
- Composition, Structure and Origin of the Moon
- Abundance, Sizes, and Major Element Compositions of Components in CR and LL Chondrites: Formation from Single Reservoirs