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Science 16 January 2009:
Vol. 323. no. 5912, pp. 356 - 359
DOI: 10.1126/science.1166804
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Reports

Early Lunar Magnetism

Ian Garrick-Bethell,1* Benjamin P. Weiss,1 David L. Shuster,2 Jennifer Buz1

It is uncertain whether the Moon ever formed a metallic core or generated a core dynamo. The lunar crust and returned samples are magnetized, but the source of this magnetization could be meteoroid impacts rather than a dynamo. Here, we report magnetic measurements and 40Ar/39Ar thermochronological calculations for the oldest known unshocked lunar rock, troctolite 76535. These data imply that there was a long-lived field on the Moon of at least 1 microtesla ~4.2 billion years ago. The early age, substantial intensity, and long lifetime of this field support the hypothesis of an ancient lunar core dynamo.

1 Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 54-521, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
2 Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA.

* To whom correspondence should be addressed. E-mail: iang{at}mit.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Magnetism of Extraterrestrial Materials.
P. Rochette, B. P. Weiss, and J. Gattacceca (2009)
Elements 5, 223-228
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