Mercury's moment of inertia from spin and gravity data

Margot, Jean-Luc; Peale, S. J.; Solomon, Sean C.; Hauck, Steven A.; Ghigo, F. D.; Jurgens, R. F.; Yseboodt, Marie; Giorgini, Jon D.; Padovan, Sebastiano; Campbell, D. B.

doi:10.1029/2012je004161

Cited by 112 publications

(284 citation statements)

References 28 publications

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“…(We show below that C/mR 2 c must be reduced and (C m + C c )/C increased when there is an elliptical solid inner core.) The values of J 2 , C 22 , and m come from Smith et al (2012) and Mazarico et al (2014), and C/mR 2 c and ( Margot et al (2012). In summary there are 16 unknowns (4ǫs, 4ξs, 4ρs, and 4Rs) and 10 equations (C/mR 2 , (C m + C c )/C, m, R c , J 2 , C 22 , two equipotential surface conditions at the CMB, and two at the ICB).…”

Section: Gravitational Torque On the Inner Core From The Mantlementioning

confidence: 99%

Consequences of a solid inner core on Mercury’s spin configuration

Peale

Margot

Hauck

et al. 2016

Icarus

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The pressure torque by a liquid core that drove Mercury to the nominal Cassini state of rotation is dominated by the torque from the solid inner core. The gravitational torque exerted on Mercury's mantle from an asymmetric solid inner core increases the equilibrium obliquity of the mantle spin axis. Since the observed obliquity of the mantle must be compatible with a solid inner core of any size, the moment of inertia inferred from the occupancy of the Cassini state must be reduced to compensate the torque from the inner core and bring Mercury's spin axis to the observed position. The unknown size and shape of the inner core means that the moment of inertia is more uncertain than previously inferred.

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Section: Gravitational Torque On the Inner Core From The Mantlementioning

confidence: 99%

Consequences of a solid inner core on Mercury’s spin configuration

Peale

Margot

Hauck

et al. 2016

Icarus

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“…From these, improved estimates of the core radius range between 1840 and 2040 km (Smith et al 2012;Hauck et al 2013;Rivoldini and Van Hoolst 2013). The value of C m /C = 0.431 ± 0.025 also supports the presence of a fluid outer core (Peale 1976;Margot et al 2012). In a recent study, these data have been used to constrain the size of the putative inner core (Dumberry and Rivoldini 2015).…”

Section: Mercurymentioning

confidence: 96%

“…The high density of the planet suggests that this core must be comparatively large, about 0.8 planetary radii. Recent MESSENGER gravity data (Smith et al 2012) and the amplitude of libration measurements with Earth-based radar (Margot et al 2007(Margot et al , 2012 have been used to calculate improved values of the planet's moment of inertia factor, C, and the ratio of the moment of inertia of the solid part of the planet overlying the liquid core to that of the whole planet, C m /C, following Peale (1976). From these, improved estimates of the core radius range between 1840 and 2040 km (Smith et al 2012;Hauck et al 2013;Rivoldini and Van Hoolst 2013).…”

Section: Mercurymentioning

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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“…The amplitude of the related 27-day forced libration in longitude has been used to infer the MoI of the Moon and the probable molten state of its central region (Khan et al, 2004;Williams et al, 2001;Yoder, 1981). In a similar way, measurements of Mercury's 88-day forced libration amplitude in longitude provide clues on the planet's internal mass distribution and coupling between core and mantle ( Jehn et al, 2004;Margot et al, 2007Margot et al, , 2012Peale, 1976Peale, , 1988. From a combined analysis of the rotational and low-degree gravitational field data, the radius of Mercury's outer liquid core and the presence of an inner solid core were inferred Rivoldini and Van Hoolst, 2013;Smith et al, 2012).…”

Section: Rotation and Tidesmentioning

confidence: 99%