View in EDS

Thermal Evolution of the Sulfur‐Rich, Small Terrestrial Planetary Core as Inferred From the Experimental Study of the Fe‐S‐O‐H System.

Saved in:
Bibliographic Details
Title: Thermal Evolution of the Sulfur‐Rich, Small Terrestrial Planetary Core as Inferred From the Experimental Study of the Fe‐S‐O‐H System.
Authors: Lee, Jeongmin1 (AUTHOR), Keum, Jaeyoon2,3 (AUTHOR), Kim, Taehyun1,4 (AUTHOR), Lee, Chanbi5 (AUTHOR), Chariton, Stella6 (AUTHOR), Prakapenka, Vitali6 (AUTHOR), Giordano, Nico7 (AUTHOR), So, Byungdal2 (AUTHOR), Hwang, Huijeong5 (AUTHOR) huijeonghwang@gist.ac.kr, Lee, Yongjae1 (AUTHOR) yongjaelee@yonsei.ac.kr
Source: Journal of Geophysical Research. Planets. Apr2026, Vol. 131 Issue 4, p1-13. 13p.
Subject Terms: *Geomagnetism, Crystallization, Chemical systems, Inner planets, Earth's core
Abstract: The cores of rocky planets, including the Earth, are believed to contain light elements such as silicon, oxygen, sulfur, hydrogen, and carbon. Amongst them, sulfur appears to be rich in the cores of small terrestrial bodies like Mars and Ganymede. To understand the evolution of sulfur‐rich cores in the presence of other light elements, we have performed in‐situ high‐temperature and high‐pressure experiments on the Fe‐S‐O‐H system in the range of 18 to 44 GPa and 1260 to 2980 K to simulate the cooling of Mars‐sized planetary core using FeS and Mg(OH)2. Our results show crystallizations of FeS2, (Fe,Mg)O, together with FeSHx(IV), upon the decomposition of Mg(OH)2, indicating that in a sulfur‐rich environment, hydrogen tends to be selectively incorporated into the FeS structure. Based on the observed density contrast of the phases formed in the Fe‐S‐O‐H system, we conjecture a buoyancy overturn of the Fe‐O layer, initially formed in the topmost part of the core, by the lighter Fe‐S‐H layer. Our proposed stratification scheme would impact thermal and chemical convection of the core to dictate the generation and/or cessation of geodynamo in sulfur‐rich terrestrial planets. Plain Language Summary: Here, we explored how the sulfur‐rich core (Fe‐S‐O‐H system) of small‐sized terrestrial planets, like Mars and Ganymede, might solidify and undergo thermal evolution during core cooling. During the cooling process, crystallization of FeO, FeS2, and hydrogen‐bearing FeS (FeSHx) occurs, with these phases separating into layers due to differences in their densities. As a result, FeO forms first and rises to the top of the sulfur‐rich core to create a solid layer. Later, as the core continues to cool, the FeSHx phase begins to crystallize and buoyantly rises upward. The lighter FeSHx replaces the existing FeO layer, causing a "buoyancy restructuring" similar to the process the Moon underwent after its magma ocean crystallized. This restructuring in the core of small‐sized terrestrial planets affects their magnetic fields. Our findings suggest that existence of light elements, such as S, O, and H, in planet's core influences the planet's thermal evolution, core dynamics, and magnetization. Key Points: In Fe‐S‐O‐H system under small‐sized planetary core conditions, crystallization of FeS2, FeO, and FeSHx(IV) occursIn sulfur‐rich core environments, hydrogen is selectively incorporated into the FeS structureBuoyancy overturn within the core influences convection and geodynamo activity in sulfur‐rich terrestrial planets, such as Mars [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: GreenFILE
Description
Abstract:The cores of rocky planets, including the Earth, are believed to contain light elements such as silicon, oxygen, sulfur, hydrogen, and carbon. Amongst them, sulfur appears to be rich in the cores of small terrestrial bodies like Mars and Ganymede. To understand the evolution of sulfur‐rich cores in the presence of other light elements, we have performed in‐situ high‐temperature and high‐pressure experiments on the Fe‐S‐O‐H system in the range of 18 to 44 GPa and 1260 to 2980 K to simulate the cooling of Mars‐sized planetary core using FeS and Mg(OH)2. Our results show crystallizations of FeS2, (Fe,Mg)O, together with FeSHx(IV), upon the decomposition of Mg(OH)2, indicating that in a sulfur‐rich environment, hydrogen tends to be selectively incorporated into the FeS structure. Based on the observed density contrast of the phases formed in the Fe‐S‐O‐H system, we conjecture a buoyancy overturn of the Fe‐O layer, initially formed in the topmost part of the core, by the lighter Fe‐S‐H layer. Our proposed stratification scheme would impact thermal and chemical convection of the core to dictate the generation and/or cessation of geodynamo in sulfur‐rich terrestrial planets. Plain Language Summary: Here, we explored how the sulfur‐rich core (Fe‐S‐O‐H system) of small‐sized terrestrial planets, like Mars and Ganymede, might solidify and undergo thermal evolution during core cooling. During the cooling process, crystallization of FeO, FeS2, and hydrogen‐bearing FeS (FeSHx) occurs, with these phases separating into layers due to differences in their densities. As a result, FeO forms first and rises to the top of the sulfur‐rich core to create a solid layer. Later, as the core continues to cool, the FeSHx phase begins to crystallize and buoyantly rises upward. The lighter FeSHx replaces the existing FeO layer, causing a "buoyancy restructuring" similar to the process the Moon underwent after its magma ocean crystallized. This restructuring in the core of small‐sized terrestrial planets affects their magnetic fields. Our findings suggest that existence of light elements, such as S, O, and H, in planet's core influences the planet's thermal evolution, core dynamics, and magnetization. Key Points: In Fe‐S‐O‐H system under small‐sized planetary core conditions, crystallization of FeS2, FeO, and FeSHx(IV) occursIn sulfur‐rich core environments, hydrogen is selectively incorporated into the FeS structureBuoyancy overturn within the core influences convection and geodynamo activity in sulfur‐rich terrestrial planets, such as Mars [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2025JE009141