Structure of eutectic Fe–FeS melts to pressures up to 17 GPa: Implications for planetary cores

Morard, Guillaume; Sanloup, C.; Fiquet, G.; Mézouar, M.; Rey, Nicolás A.; Poloni, Roberta; Beck, Pierre

doi:10.1016/j.epsl.2007.09.009

Cited by 84 publications

(106 citation statements)

References 62 publications

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“…While Fei et al (1997Fei et al ( , 2000 found that the eutectic concentration remains constant betweeñ 7 and 10 GPa, the data of Morard et al (2007) suggest a constant eutectic concentration between slightly higher pressures of~11 and 15 GPa (see Fig. 5 in Morard et al 2007). These uncertainties also impact the slope of the melting temperature, which is typically obtained through linear interpolation of the melting temperature of the endmembers (Fe-FeS eutectic and pure Fe or pure FeS).…”

Section: Iron Snow Regimementioning

confidence: 96%

“…Note that the exact decline of the eutectic concentration with pressure is somewhat uncertain. While Fei et al (1997Fei et al ( , 2000 found that the eutectic concentration remains constant betweeñ 7 and 10 GPa, the data of Morard et al (2007) suggest a constant eutectic concentration between slightly higher pressures of~11 and 15 GPa (see Fig. 5 in Morard et al 2007).…”

Section: Iron Snow Regimementioning

confidence: 99%

“…The increase of the liquidus with depth in the snow zone is inevitably accompanied by a decrease in the sulfur concentration with depth, which implies the presence of a stable chemical gradient across the snow zone (Hauck et al 2006;Williams 2009;Rückriemen et al 2015). Usselman (1975), Boehler (1993), Boehler (1996), Fei et al (1997Fei et al ( , 2000, Shen et al (1998), Alfè et al (2002b), Campbell et al (2007), Chudinovskikh and Boehler (2007), Morard et al (2007), and Stewart et al (2007). Figure after Morard et al (2008) The remelting of iron particles below the snow zone results in a local enrichment of iron in the Fe-FeS melt.…”

Section: Iron Snow Regimementioning

confidence: 99%

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Iron snow, crystal floats, and inner-core growth: modes of core solidification and implications for dynamos in terrestrial planets and moons

Breuer

Rueckriemen

Spohn

2015

Prog. in Earth and Planet. Sci.

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Recent planetary space missions, new experimental data, and advanced numerical techniques have helped to improve our understanding of the deep interiors of the terrestrial planets and moons. In the present review, we summarize recent insights into the state and composition of their iron (Fe)-rich cores, as well as recent findings about the magnetic field evolution of Mercury, the Moon, Mars, and Ganymede. Crystallizing processes in iron-rich cores that differ from the classical Earth case (i.e., Fe snow and iron sulfide (FeS) crystallization) have been identified and found to be important in the cores of terrestrial bodies. The Fe snow regime occurs at pressures lower than that in the Earth's core on the iron-rich side of the eutectic, where iron freezes first close to the core-mantle boundary rather than in the center. FeS crystallization, instead, occurs on the sulfur-rich side of the eutectic. Depending on the core temperature profile and the pressure range considered, FeS crystallizes either in the core center or close to the core-mantle boundary. The consequences of the various crystallizing mechanisms for core dynamics and magnetic field generation are discussed. For the Moon, revised paleomagnetic data obtained with advanced techniques suggest a peculiar history of its internal dynamo, with an early strong field persisting between 4.25 and 3.5 Ga, and subsequently a much weaker field. In addition, the long-lasting dynamo and the possible presence of an inner core, as inferred from a revised interpretation of Apollo seismic data, suggest core crystallization as a viable process of magnetic field generation for a substantial period during lunar evolution. The present-day magnetic fields of Mercury and Ganymede (if they occur on the iron-rich side of the Fe-FeS eutectic) and the related dynamo action are likely generated in the Fe snow regime and seem to be recent features. An earlier dynamo in Mercury would have been powered differently. For Mercury, MESSENGER data further suggest core formation under reducing conditions that may have resulted in an Fe-S-Si composition, further complicating the core crystallization process. Mars, with its early and strong paleo-field, likely has not yet started to freeze out an inner iron core.

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Section: Iron Snow Regimementioning

confidence: 96%

Section: Iron Snow Regimementioning

confidence: 99%

Section: Iron Snow Regimementioning

confidence: 99%

See 1 more Smart Citation

Iron snow, crystal floats, and inner-core growth: modes of core solidification and implications for dynamos in terrestrial planets and moons

Breuer

Rueckriemen

Spohn

2015

Prog. in Earth and Planet. Sci.

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“…Under increasing P, structural evolution of the Fe-S bond towards metallic bond was evidenced in the vicinity of gap closure (Morard et al, 2007), thus providing a rationale for it. Not all immiscible Fe-alloys have been studied yet under pressure, but Fe-S-C gap closes at 5 GPa (Corgne et al, 2008), and Fe-FeO could close above 70 GPa, P at which the insulator to metallic transition has been reported for FeO (Knittle and Jeanloz, 1986).…”

Section: Immiscible Liquidsmentioning

confidence: 99%

“…Fei et al (1997Fei et al ( , 2000). Morard et al (2007); Usselman (1975); Stewart et al (2007); Chudinovskikh and Boehler (2007) (adaptédeFeietal. (1997(adaptédeFeietal.…”

Section: Figure 4: Critère De Fusionàh a U T Ep :A P P A R I T I O Ndmentioning

confidence: 99%

High-pressure experimental geosciences: state of the art and prospects

Sanloup¹

2012

Bulletin De La Société Géologique De France

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International audienceThis paper aims at reviewing the current advancements of high pressure experimental geosciences. The an- gle chosen is that of in situ measurements at the high pressure (P) and high temperature (T) conditions relevant of the deep Earth and planets, measurements that are often carried out at large facilities (X-ray synchrotrons and neutron sources). Rather than giving an exhaustive catalogue, four main active areas of research are chosen: the latest advance- ments on deep Earth mineralogy, how to probe the properties of melts, how to probe Earth dynamics, and chemical reac- tivity induced by increased P-T conditions. For each area, techniques are briefly presented and selected examples illustrate their potentials, and what that tell us about the structure and dynamics of the planet

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The Fe snow regime in Ganymede's core: A deep‐seated dynamo below a stable snow zone

2015

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Ganymede shows signs of a present-day magnetic field, whose origin is thought to be in its core. The Fe snow regime has been suggested to be vital in Ganymede's history. In this regime, Fe crystals first form at the core-mantle boundary and later settle to the deeper core due to their higher density (Fe snow). A stable chemical gradient arises within the liquid of the snow zone. Below the snow zone the Fe particles remelt. We propose that the remelting of Fe in the deeper, entirely liquid core initiates compositional convection, which could be the origin of the dynamo. Such a dynamo is restricted by the period of time the snow zone needs to grow across the core. We investigate this time period with a 1-D core evolution model by varying the initial sulfur concentration, the core heat flux, and the thermal conductivity of the core. For the proposed dynamo in the deeper liquid core, we obtain necessary time periods of between 320 and 800 Myr and magnetic field strengths at the surface that match the observed value of 719 nT. To explain the present magnetic field, we favor cores with high sulfur concentrations because those lead to a late start and a long duration of the dynamo. Furthermore, a present dynamo below the snow zone suggests the absence of an inner core.

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Structure of eutectic Fe–FeS melts to pressures up to 17 GPa: Implications for planetary cores

Cited by 84 publications

References 62 publications

Iron snow, crystal floats, and inner-core growth: modes of core solidification and implications for dynamos in terrestrial planets and moons

Iron snow, crystal floats, and inner-core growth: modes of core solidification and implications for dynamos in terrestrial planets and moons

High-pressure experimental geosciences: state of the art and prospects

The Fe snow regime in Ganymede's core: A deep‐seated dynamo below a stable snow zone

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