Constraining Ganymede's Interior Structure and Bulk Composition from Its Present-Day Magnetic Field Strength
Authors: Jun Kimura, Ryohei Kawakami, Taro Matsuo, Sho Sasaki
Abstract
Ganymede is the only Solar System satellite with a global magnetic field driven by a core dynamo. Although its small moment-of-inertia (MoI) factor indicates a differentiated structure of a metallic core, rocky mantle, and outer hydrosphere, its exact bulk composition and layer thicknesses remain highly uncertain. We developed a comprehensive, long-term thermochemical evolution model that couples thermal history with magnetic field generation. Building upon previous theoretical frameworks, this study systematically evaluates how diverse chondritic precursor compositions constrain Ganymede's internal thermochemical evolution and core solidification processes. Based on interior structures initially permitted by a wide range of chondritic compositions and geodetic constraints, we applied the observed equatorial surface magnetic field strength ($\sim$719 nT) as a dynamic filter. Our evolutionary simulations demonstrate that while magnetic dynamos can operate under entire melting, Fe-snow, and FeS-layer regimes, the requirement to sustain the observed field strength strongly restricts the viable interior models. Satisfying this constraint preferentially requires a relatively large core radius and a specific, non-eutectic bulk core sulfur concentration. Consequently, this coupled thermochemical approach highlights the main novelty of this study: characterizing the hydrosphere's density serves as an independent constraint to break the structural degeneracy of Ganymede's bulk composition. Our model indicates that L and CI chondrites yield parameter spaces capable of sustaining comparable field strengths under a low-density hydrosphere scenario (1,200 kg m-3), whereas the H chondrite composition can satisfy this criterion under a high-density scenario (1,300 kg m-3). These predictions provide a critical framework to be tested by the JUICE mission arriving in 2031.
The papers around it, by date and closeness
Higher is closer to this paper; left is older. Lines join papers close to each other: groups of lines are sub-topics. Select a point to see why it is there. Back to the summary of this paper
Papers around this one
Ranked by how close their title and abstract are to this paper’s. Select some to read them together.
Closest papers
-
Compositional evolution during rocky protoplanet accretionPhilip J. Carter, Zoë M. Leinhardt, Tim Elliott et al. · 2015 · Earth and Planetary Astrophysics · cited 82 times · AI summary available
Compositional evolution during rocky protoplanet accretion models how chondritic planetesimals shape terrestrial planet compositions, rather than Ganymede’s present-day interior and magnetic field.
Abstract
The Earth appears non-chondritic in its abundances of refractory lithophile elements, posing a significant problem for our understanding of its formation and evolution. It has been suggested that this non-chondritic composition may be explained by collisional erosion of differentiated planetesimals of originally chondritic composition. In this work, we present N-body simulations of terrestrial planet formation that track the growth of planetary embryos from planetesimals. We simulate evolution through the runaway and oligarchic growth phases under the Grand Tack model and in the absence of giant planets. These simulations include a state-of-the-art collision model which allows multiple colli…
-
Saturn's Interior After the Cassini Grand FinaleJ. J. Fortney, B. Militzer, C. R. Mankovich et al. · 2023 · Earth and Planetary Astrophysics · cited 6 times · AI summary available
Saturn's Interior After the Cassini Grand Finale reviews Saturn’s interior structure and thermal evolution, whereas this paper models Ganymede’s interior and dynamo.
Abstract
We present a review of Saturn's interior structure and thermal evolution, with a particular focus on work in the past 5 years. Data from the Cassini mission, including a precise determination of the gravity field from the Grand Finale orbits, and the still ongoing identification of ring wave features in Saturn's C-ring tied to seismic modes in the planet, have led to dramatic advances in our understanding of Saturn's structure. Models that match the gravity field suggest that differential rotation, as seen in the visible atmosphere, extends down to at least a depth of 10,000 km (1/6$^{\rm th}$ the planet's radius). At greater depths, a variety of different investigations all now point to a d…
-
A Helicity-Based Method to Infer the CME Magnetic Field Magnitude in Sun and Geospace: Generalization and Extension to Sun-Like and M-Dwarf Stars and Implications for Exoplanet HabitabilityS. Patsourakos, M. K. Georgoulis · 2017 · Solar Physics, 2017, 292, 89 · cited 17 times · Not summarized yet
A Helicity-Based Method to Infer the CME Magnetic Field Magnitude estimates magnetic fields in coronal mass ejections, not fields generated by a planetary core dynamo.
Abstract
Patsourakos et al. (Astrophys. J. 817, 14, 2016) and Patsourakos and Georgoulis (Astron. Astrophys. 595, A121, 2016) introduced a method to infer the axial magnetic field in flux-rope coronal mass ejections (CMEs) in the solar corona and farther away in the interplanetary medium. The method, based on the conservation principle of magnetic helicity, uses the relative magnetic helicity of the solar source region as input estimates, along with the radius and length of the corresponding CME flux rope. The method was initially applied to cylindrical force-free flux ropes, with encouraging results. We hereby extend our framework along two distinct lines. First, we generalize our formalism to sever…
-
Earth shaped by primordial H$_2$ atmospheresEdward D. Young, Anat Shahar, Hilke E. Schlichting · 2023 · Nature, v. 616 (7956), 306-311 (2023) · cited 104 times · AI summary available
Earth shaped by primordial H$_2$ atmospheres models how hydrogen-rich atmospheres affect rocky-planet water and core composition, rather than Ganymede’s chondritic interior.
Abstract
Earth's water, intrinsic oxidation state, and metal core density are fundamental chemical features of our planet. Studies of exoplanets provide a useful context for elucidating the source of these chemical traits. Planet formation and evolution models demonstrate that rocky exoplanets commonly formed with hydrogen-rich envelopes that were lost over time. These findings suggest that Earth may also have formed from bodies with H$_2$-rich primary atmospheres. Here we use a self-consistent thermodynamic model to show that Earth's water, core density, and overall oxidation state can all be sourced to equilibrium between H$_2$-rich primary atmospheres and underlying magma oceans in its progenitor …
-
Phase equilibria of sub-Neptunes and super-EarthsEdward D. Young, Lars Stixrude, James G. Rogers et al. · 2024 · Earth and Planetary Astrophysics · cited 4 times · AI summary available
Phase equilibria of sub-Neptunes and super-Earths examines silicate-hydrogen mixing and internal layering in rocky planets, unlike Ganymede’s core-solidification and magnetic-field constraints.
Abstract
We investigate the consequences of non-ideal chemical interaction between silicate and overlying hydrogen-rich envelopes for rocky planets using basic tenets of phase equilibria. Based on our current understanding of the temperature and pressure conditions for complete miscibility of silicate and hydrogen, we find that the silicate-hydrogen binary solvus will dictate the nature of atmospheres and internal layering in rocky planets that garnered H$_2$-rich primary atmospheres. The temperatures at the surfaces of supercritical magma oceans will correspond to the silicate-hydrogen solvus. As a result, the radial positions of supercritical magma ocean-atmosphere interfaces, rather than their tem…
-
Asteroseismic inference of the near-core magnetic field strength in the main sequence B star HD 43317Daniel Lecoanet, Dominic M. Bowman, Timothy Van Reeth · 2022 · Solar and Stellar Astrophysics · cited 20 times · AI summary available
Asteroseismic inference of the near-core magnetic field strength in the main sequence B star HD 43317 uses stellar oscillations to constrain an interior magnetic field, not a satellite dynamo.
Abstract
About 10 per cent of intermediate- and high-mass dwarf stars are observed to host a strong large-scale magnetic field at their surface, which is thought to be of fossil field origin. However, there are few inferences as to the magnetic field strength and geometry within the deep interiors of stars. Considering that massive stars harbour a convective core whilst on the main sequence, asteroseismology of gravity (g) modes is able to provide constraints on their core masses, yet it has so far not been used to probe the strength of their interior magnetic fields. Here we use asteroseismology to constrain an upper limit for the magnetic field strength in the near-core region of the pulsating and …
-
An abrupt change in the stellar spin-down law at the fully convective boundaryYuxi Lu, Victor See, Louis Amard et al. · 2023 · Solar and Stellar Astrophysics · cited 14 times · AI summary available
An abrupt change in the stellar spin-down law at the fully convective boundary links stellar convection to spin-down and dynamo behavior, rather than modeling Ganymede’s interior.
Abstract
The importance of the existence of a radiative core in generating a solar-like magnetic dynamo is still unclear. Analytic models and magnetohydrodynamic simulations of stars suggest the thin layer between a star's radiative core and its convective zone can produce shearing that reproduces key characteristics of a solar-like dynamo. However, recent studies suggest fully and partially convective stars exhibit very similar period-activity relations, hinting that dynamos generated by stars with and without radiative cores hold similar properties. Here, using kinematic ages, we discover an abrupt change in the stellar spin-down law across the fully convective boundary. We found that fully convect…
-
The influence of cold Jupiters in the formation of close-in planets. I. planetesimal transportSergio Best, Antranik A. Sefilian, Cristobal Petrovich · 2023 · Earth and Planetary Astrophysics · cited 10 times · AI summary available
The influence of cold Jupiters in the formation of close-in planets. I. planetesimal transport studies planetesimal orbital transport during planet formation, not differentiated interiors or magnetic dynamos.
Abstract
The formation of a cold Jupiter (CJ) is expected to quench the influx of pebbles and the migration of cores interior to its orbit, thus limiting the efficiency of rocky planet formation either by pebble accretion and/or orbital migration. Observations, however, show that the presence of outer CJs ( >1 au and >0.3 Jupiter masses) correlates with the presence of inner Super Earths (at <1 au). This observation may simply be a result of an enhanced initial reservoir of solids in the nebula required to form a CJ or a yet-to-be-determined mechanism assisted by the presence of the CJ. In this work, we focus on the latter alternative and study the orbital transport of planetesimals interior to a CJ …
Go further
How are these papers found?
We compare the title and abstract of this paper with those of every paper summarized on this site, and with the papers Semantic Scholar recommends, those it cites and those citing it (for a much-cited paper, its most recent citations and, from OpenAlex, the most cited ones). Among the prior work and the follow-ups, the papers that use each other in depth, a method it uses and the much-cited follow-ups come a little higher. The levels (very close, close, related) come from the similarity of the texts, not from a judgment of quality; * marks a paper without an abstract, compared by its title. The sentence under a paper is written by an AI from the two abstracts: check it in the papers. A paper marked not relevant by three readers leaves the list.
Updated on 5 November 2026.