Mercury’s inner core size and core-crystallization regime

Dumberry, Mathieu; Rivoldini, Attilio

doi:10.1016/j.icarus.2014.10.038

Cited by 84 publications

(120 citation statements)

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“…Based on these parameters with the above thermodynamic relations, the adiabatic temperature gradients of the liquid cores were calculated to be around 27(6) K/GPa for Mercury and 18(4) K/GPa for Mars. The adiabatic temperature gradient is consistent with that estimated by Fei and Bertka (2005) for the Martian core, and it is consistent but slightly greater than that estimated by Dumberry and Rivoldini (2015) for Mercury's core as shown in Fig. 4.…”

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

confidence: 90%

“…The adiabatic temperature of the core of Mercury estimated by this work, 27 K/GPa, is given as a red curve, S, under the assumption that the temperature at CMB of Mercury is 1800 K (e.g., Dumberry and Rivoldini 2015;Malavergne et al 2010). The temperature profiles of the Martian core estimated by Fei and Bertka (2005), and Mercury's core by Dumberry and Rivoldini (2015) Grüneisen parameter γ th of the outer core may be around 1.3 (Anderson 1998;Dubrovinsky 2000;Stacey 1995;Vocadlo et al 2000). However, it could have a large uncertainty.…”

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

confidence: 99%

“…Therefore, we assumed γ th to be in the range of 1.0-1.5. The density of molten metal in the core of Mercury may be taken to be the density of the Fe-S melt (Sanloup et al 2000(Sanloup et al , 2002Terasaki 2015) or the Fe-Si melt at high pressure (Tateyama et al 2011;Yu and Secco 2008;Nishida et al 2011;Terasaki 2015), and the CMB temperatures are assumed to be around 1770 K for Mercury and 1990 K for Mars (e.g., Dumberry and Rivoldini 2015;Malavergne et al 2010). Based on these parameters with the above thermodynamic relations, the adiabatic temperature gradients of the liquid cores were calculated to be around 27(6) K/GPa for Mercury and 18(4) K/GPa for Mars.…”

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

confidence: 99%

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

confidence: 90%

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

confidence: 99%

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

confidence: 99%

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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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“…Due to lack of compositional information, I assume the the incongruent melting Fe (3−x) S 2 to FeS + liquid reaches an asymptotic composition of 26 wt% S along Morard et al (2008) melting curve. In contrast, Dumberry and Rivoldini (2015) assumed that the eutectic composition decreased exponentially with pressure towards a value of 11 wt% S (compare Fig. 3), and did not parameterize the incongruent melting of Fe (3−x) S 2 at all.…”

mentioning

confidence: 99%

Mars core structure—concise review and anticipated insights from InSight

Helffrich

2017

Prog Earth Planet Sci

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This review summarizes the knowledge of Mars' interior structure, its inferred composition, and the anticipated seismological properties arising from its composition with particular focus on Mars' core. The emphasis on the core stems from the unusual morphology of the liquidus diagram of iron at moderate pressures when enriched in sulfur. From a fairly detailed liquidus diagram constructed from experimental studies, I identify a set of processes that could act within Mars' core: an iron "snow" from the core-mantle boundary's surface and a Fe 3−x S 2 "ground fog" forming at the base of the core. Depending on temperature and bulk sulfur composition, these could form an inner core or could stratify the outer core by enriching it in sulfur, or both. Core stratification could be one explanation for the extinction of Mars' magnetic field early in the planet's history, and I demonstrate the feasibility of this mechanism. The crystallization processes in the core could be observable in the seismic data that the future Mars geophysical mission, InSight, is planned to provide. The core size, the presence of an inner core, and the wavespeed profile of the outer core, whose radial derivative provides a proxy for changes in composition, are key observables to seek.

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“…and Mercury (e.g. Dumberry & Rivoldini, 2014;Knibbe & Van Fig. 4 Georg et al, 2007;Fitoussi et al, 2009;Ziegler et al, 2010;Chakrabarti & Jacobsen, 2010;Armytage et al 2011Armytage et al , 2012 Westrenen, 2015), as well as differentiated asteroids such as Vesta (e.g.…”

Section: The Abundance Of Lithophile Elements (Plus Iron) In Bse Nomentioning

confidence: 99%

Silicon stable isotope fractionation between metal and silicate at high-pressure, high-temperature conditions as a tracer of planetary core formation

Kempl

Vroon

Wagt

et al. 2016

Netherlands Journal of Geosciences

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The largest differentiation event in Earth and other terrestrial planets was the high-pressure, high-temperature process of metal core segregation from a silicate mantle. The abundant element silicon (Si) can be partially sequestered into the metallic core during metal-silicate differentiation, depending on pressure, temperature and planetary oxidation state. Knowledge of the Si content of a planet's core can constrain the conditions of core formation, but in the absence of direct samples from planetary cores, quantifying core Si content is challenging. One relatively new tool to study core formation in terrestrial planets is based on combining measurements of the Si stable isotopic composition of planetary crust and mantle samples with measurements of the Si stable isotope fractionation between metal and silicate at high-temperature and high-pressure conditions. In this study we present the results of a small set of high-pressure, high-temperature (HPT) experiments and combine these with a review of literature data to investigate how the Si isotope fractionation behaviour between metal and silicate varies as a function specifically of experimental run time and temperature. We show that although there is no debate about the sign of fractionation, absolute values for Si isotope fractionation between metal and silicate are difficult to constrain because the experimental database remains incomplete, and because Si isotopic measurements of metals in particular suffer from the absence of a true inter-laboratory comparison. We conclude that in order to derive accurate quantitative estimates of the Si content of the core of the Earth or other planets a wide range of additional experiments will be required.

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Mercury’s inner core size and core-crystallization regime

Cited by 84 publications

References 50 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

Mars core structure—concise review and anticipated insights from InSight

Silicon stable isotope fractionation between metal and silicate at high-pressure, high-temperature conditions as a tracer of planetary core formation

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