Can the lunar crust be magnetized by shock: Experimental groundtruth

Gattacceca, J.; Boustie, M.; Hood, L. L.; Cuq‐Lelandais, J.‐P.; Fuller, M.; Bezaeva, N. S.; Rességuier, T. de; Berthe, Laurent

doi:10.1016/j.epsl.2010.08.011

Cited by 56 publications

(50 citation statements)

References 43 publications

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“…For 10017, we found that the residual VRM would be 9.4 × 10 Although our petrographic observations exclude shocks with pressures >5 GPa, even shocks with lower peak pressures could produce magnetization if a field were present. To investigate this possibility, we conducted pressure remanent magnetization (PRM) acquisition experiments (SI Appendix) for subsamples 378-3 and 102-1 following the method used by Gattacceca (27). Like previous such studies of lunar rocks (27), we found that PRM was acquired dominantly by LC grains (<∼30-40 mT) with even the 2.0-GPa PRM significantly softer than the NRM (SI Appendix).…”

Section: Nrmmentioning

confidence: 93%

Persistence and origin of the lunar core dynamo

Suavet

Weiss

Cassata

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The lifetime of the ancient lunar core dynamo has implications for its power source and the mechanism of field generation. Here, we report analyses of two 3.56-Gy-old mare basalts demonstrating that they were magnetized in a stable and surprisingly intense dynamo magnetic field of at least ∼13 μT. These data extend the known lifetime of the lunar dynamo by ∼160 My and indicate that the field was likely continuously active until well after the final large basin-forming impact. This likely excludes impact-driven changes in rotation rate as the source of the dynamo at this time in lunar history. Rather, our results require a persistent power source like precession of the lunar mantle or a compositional convection dynamo.high-K mare basalts | paleomagnetism

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Section: Nrmmentioning

confidence: 93%

Persistence and origin of the lunar core dynamo

Suavet

Weiss

Cassata

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Theoretical models have suggested that such fields might reach tens or even hundreds of mT but would be short-lived, lasting up to a day for the largest, basin-forming impacts and less than seconds for most smaller impacts. Although impact fields would only be capable of imparting a full TRM on samples that cool from the Curie temperature to surface temperatures more quickly than these time scales (32), an SRM could be readily acquired by virtually any rock shocked in the presence of such fields, given the near instantaneous pressure changes associated with shock waves (33). If correct, the impact plasma fields hypothesis would have profound implications for all of extraterrestrial paleomagnetism, because it implies that NRM may not be a record of internal geophysical processes on planetary bodies.…”

Section: Apollo-era Measurementsmentioning

confidence: 99%

The lunar dynamo

Weiss

Tikoo

2014

Science

196

161

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The inductive generation of magnetic fields in fluid planetary interiors is known as the dynamo process. Although the Moon today has no global magnetic field, it has been known since the Apollo era that the lunar rocks and crust are magnetized. Until recently, it was unclear whether this magnetization was the product of a core dynamo or fields generated externally to the Moon. New laboratory and spacecraft measurements strongly indicate that much of this magnetization is the product of an ancient core dynamo. The dynamo field persisted from at least 4.25 to 3.56 billion years ago (Ga), with an intensity reaching that of the present Earth. The field then declined by at least an order of magnitude by ∼3.3 Ga. The mechanisms for sustaining such an intense and long-lived dynamo are uncertain but may include mechanical stirring by the mantle and core crystallization.

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“…An additional complication is that the lithologies that comprise lunar magnetic anomalies are not rigorously constrained mineralogically. As a result, it is difficult to discern if the magnetization of materials in these anomalies is derived from crystallization or from impact shock (Fuller and Cisowski, 1987;Gattacceca, 2010).…”

Section: Introductionmentioning

confidence: 98%