Early Lunar Magnetism

Garrick‐Bethell, I.; Weiss, B. P.; Shuster, David L.; Buz, J.

doi:10.1126/science.1166804

Cited by 162 publications

(161 citation statements)

References 38 publications

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“…Paleomagnetic measurements of lunar rocks show magnetic remanence most easily explained by a long-lived early lunar dynamo (Garrick-Bethell et al 2009). Dwyer and Stevenson (2005) argued that the only plausible driving force for an early lunar dynamo is mechanical stirring of the liquid core due to the relative motion between the core and mantle.…”

Section: Introductionmentioning

confidence: 99%

Precession of the lunar core

Meyer

Wisdom

2011

Icarus

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Abstract:Goldreich (1967) showed that a lunar core of low viscosity would not precess with the mantle.We show that this is also the case for much of lunar history. But when the Moon was close to the Earth the Moon's core was forced to follow closely the precessing mantle, in that the rotation axis of the core remained nearly aligned with the symmetry axis of the mantle. The transition from locked to unlocked core precession occurred between 26.0 and 29.0 Earth radii, thus it is likely that the lunar core did not follow the mantle during the Cassini transition. Dwyer and Stevenson (2005) suggested that the lunar dynamo needs mechanical stirring to power it. The stirring is caused by the lack of locked precession of the lunar core.So, we do not expect a lunar dynamo powered by mechanical stirring when the Moon was closer to the Earth than 26.0 to 29.0 Earth radii. A lunar dynamo powered by mechanical stirring might have been strongest near the Cassini transition.

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Section: Introductionmentioning

confidence: 99%

Precession of the lunar core

Meyer

Wisdom

2011

Icarus

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“…Generation and maintenance of magnetic field of internal origin can effectively protect the solar winds, thus pro-vide a chance to fertilize life forms once they are created. In fact, the records of four-billion-year old magnetic field were well preserved in lunar rocks (Lawrence et al 2008;Garrick-Bethell et al 2009) and Martian meteorites (Kirschvink et al 1997;Weiss et al 2000Weiss et al , 2002Antretter et al 2003). As in terrestrial igneous rocks, records of younger volcanism are also preserved in Martian meteorites (Nyquist et al 2001;Yu & Gee 2005).…”

Section: Evolution Of the Solar Systemmentioning

confidence: 75%

Meteorites: Rocks From the Outer Space

Doh¹,

2010

Journal of The Korean Astronomical Society

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According to the historical documents and paintings in many civilizations, rocks that fell from the sky fascinated humans as the message from the God or supernaturals. Scientific progress allows humans to recognize these exciting extraterrestrial objects as meteorites. Meteorites contain a wealth of pivotal information regarding formation of the early Solar System. Meteorites also provide broader scientific insights on, for example, the origin of life, interplanetary transfer of life forms, massive depletion of biosphere on Earth, and evolution of lithosphere on Earth-like planetary bodies.

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“…Lunar paleomagnetic data suggest a magnetizing field of up to~100 μT between at least 4.25 and 3.56 Ga b.p., a field similar in strength to the present terrestrial magnetic field (Cisowski and Fuller 1986;Garrick-Bethell et al 2009;Shea et al 2012;Suavet et al 2013). The field strength decreased by an order of magnitude between 3.56 and~3.3 Ga b.p.…”

Section: The Moonmentioning

confidence: 90%

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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Early Lunar Magnetism

Cited by 162 publications

References 38 publications

Precession of the lunar core

Precession of the lunar core

Meteorites: Rocks From the Outer Space

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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