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The Magnetic Field of Mercury

Published online by Cambridge University Press:  30 March 2016

Norman F. Ness
Norman F. Ness*
Affiliation:
Laboratory for Extraterrestrial Physics, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

Abstract

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The USA Mariner 10 spacecraft encountered Mercury three times in 1974-1975. The 1st and 3rd encounters provided detailed observations of a well developed, detached bow shock wave which results from the interaction of the solar wind. The planet possesses a global magnetic field, and modest magnetosphere, which deflects the solar wind. The field is approximately dipolar, with orientation in the same sense as Earth, tilted 12° from the rotation axis. The magnetic moment, 5×1022 Gauss-cm3, corresponds to an undistorted equatorial field intensity of 350γ, approximately 1% of Earth’s. The origin of the field, while unequivocally intrinsic to the planet, is uncertain. It may be due to remanent magnetization acquired from an extinct dynamo or a primordial magnetic field or due to a presently active dynamo. Among these possibilities, the latter appears more plausible at present. In any case, the existence of the magnetic field provides very strong evidence of a mature, differentiated planetary interior with a large core, Rc ≈ 0.7RM, and a record of the history of planetary formation in the magnetization of the crustal rocks.

Type
Joint Dicussions
Information
Highlights of Astronomy , Volume 4 , Issue 1: Highlights of Astronomy. As presented at the XVIth General Assembly of the IAU, 1976 (Part I) , 1977 , pp. 179 - 190
Copyright
Copyright © Reidel 1977

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