Mars: A New Core-Crystallization Regime

Stewart, Andrew J.; Schmidt, Max W.; Westrenen, W. van; Liebske, Christian

doi:10.1126/science.1140549

Cited by 209 publications

(212 citation statements)

References 24 publications

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“…Thus, crystallization of their cores started at the core-mantle boundary region even in the cores containing both silicon and sulfur as light elements. This crystallization start is consistent with the snowing-core model proposed by previous authors for the cores with the Fe-S systems (Chen et al 2008;Stewart et al 2007). …”

Section: Resultssupporting

confidence: 78%

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Melting relations in the Fe–S–Si system at high pressure and temperature: implications for the planetary core

Sakairi

Ohtani

Kamada

et al. 2017

Prog. in Earth and Planet. Sci.

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The phase and melting relations in the Fe-S-Si system were determined up to 60 GPa by using a double-sided laser-heated diamond anvil cell combined with X-ray diffraction. On the basis of the X-ray diffraction patterns, we confirmed that hcp/fcc Fe-Si alloys and Fe 3 S are stable phases under subsolidus conditions in the Fe-S-Si system. Both solidus and liquidus temperatures are significantly lower than the melting temperature of pure Fe and both increase with pressure. The slopes of the Fe-S-Si liquidus and solidus curves determined here are smaller than the adiabatic temperature gradients of the liquid cores of Mercury and Mars. Thus, crystallization of their cores started at the core-mantle boundary region.

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Section: Resultssupporting

confidence: 78%

“…Therefore, crystallization of the core of the planets must have started at CMB. This crystallization start is consistent with the snowing-core model proposed for Ganymede (Hauck et al 2006) and Mars (Stewart et al 2007). …”

Section: Solidus and Liquidus Temperatures In The Fe-s-si Systemsupporting

confidence: 72%

Melting relations in the Fe–S–Si system at high pressure and temperature: implications for the planetary core

Sakairi

Ohtani

Kamada

et al. 2017

Prog. in Earth and Planet. Sci.

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show abstract

“…For core materials, Fe-S alloys have received the largest attention so far as the eutectic point has the lowest melting T amongst Fe-alloys, hence it is technically the easiest system to workw i t h . Am a j o re f f e c to fp r e s s u r ei s to shift the eutectic composition towards the Fe pole (Campbell et al, 2007;Stewart et al, 2007;Morard et al, 2008a), resulting in the sulfide phase being present at the solidus for potential core compositions containing 10±5w t%lig h te le me n ts( F ig . 6 ) .…”

Section: Melting Relationshipsmentioning

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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“…Therefore, the core is now thought to be composed of Fe-Si-S (e.g., Malavergne et al 2010;Chabot et al 2014) rather than Fe-S, which is generally taken as a good model for Earth-like planetary cores. Experimental data relevant to Fe-FeS eutectic melting relations (Fei et al , 2000Chudinovskikh and Boehler 2007;Stewart et al 2007;Chen et al 2008;Buono and Walker 2011) suggest that crystallization in the core can proceed substantially differently in small planets compared with the Earth's core. In small planets, iron may start crystallizing at the core-mantle boundary (CMB) rather than in the center, and iron snow may form (e.g., Hauck et al 2006).…”

Section: Introductionmentioning

confidence: 99%

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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Mars: A New Core-Crystallization Regime

Cited by 209 publications

References 24 publications

Melting relations in the Fe–S–Si system at high pressure and temperature: implications for the planetary core

Melting relations in the Fe–S–Si system at high pressure and temperature: implications for the planetary core

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

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

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