MANY lunar rocks possess a stable component of natural remanent magnetisation (NRM) with specific intensities around 10−6 e.m.u. g−1 (refs 1–6). Most of them also have compaction ages of more than 3 × 109 yr (refs 5 and 6). Ancient lunar surface magnetic fields of the order of 10−2–1.2 gauss have been postulated to explain the observed NRM in lunar rocks1–6, and several interesting suggestions have been made concerning the origin of such high magnetic fields during the early history of the Moon. Runcorn and Urey7 have proposed an intrinsic dipolar field, acquired by the Moon during its initial stages of formation. Such a dipolar field could result either from a primaeval magnetisation of the Moon by an external field or from the action of an ancient lunar dynamo. Collinson et al.5 supported that theory with the observation that the palaeofield required to explain the stable NRM in lunar rocks decreases with the decreasing formation or compaction ages of the rock samples. I point out here some constraints that can be put on the origin and nature of the ancient lunar magnetic field, based on the observation of solar-wind ions in lunar breccias with compaction ages of more than 3.2 × 109 yr.
This is a preview of subscription content, access via your institution
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Rent or buy this article
Prices vary by article type
Prices may be subject to local taxes which are calculated during checkout
Pearce, G. W., Strangway, D. W., and Larson, E. E., Proc. 2nd Lunar Sci. Conf., 2451–2460 (1971).
Nagata, T., et al., Proc. 3rd Lunar Sci. Conf., 2423–2447 (1972).
Gose, W. A., Strangway, D. W., and Pearce, G. W., The Moon, 7, 196–201 (1973).
Banerjee, S. K., and Mellema, J. P., Earth Planet. Sci. Lett., 23, 175–188 (1974).
Collinson, D. W., Runcorn, S. K., and Stephenson, D., Proc. 6th Lunar Sci. Conf., 3049–3062 (1975).
Cisowski, S. M., et al., Proc. 6th Lunar Sci. Conf., 3123–3141 (1975).
Runcorn, S. K., and Urey, H. C., Science, 180, 636–638 (1973).
Reynolds, J. H., Alexander, E. C., Jr, Davis, P. K., and Srinivasan, B., Geochim. cosmochim. Acta, 38, 401–418 (1974).
Srinivasan, B., Proc. 4th Lunar Sci. Conf., 2049–2064 (1973).
Alexander, E. C., Jr, and Kahl, S. B., Proc. 5th Lunar Sci. Conf., 1353–1373 (1974).
Megrue, G. H., J. geophys. Res., 78, 3216–3221 (1973).
Murthy, V. R., and Banerjee, S. K., The Moon, 7, 149–171 (1973).
Russell, C. T., Schubert, G., and Coleman, P. J., Space Res. (in the press).
Siscoe, G. L., and Goldstein, B., J. geophys. Res., 78, 6741–6748 (1973).
Eberhardt, P., Geiss, J., and Grögler, N., J. geophys. Res., 70, 4375–4378 (1965).
About this article
Cite this article
GOSWAMI, J. Constraints on the nature of the ancient lunar magnetic field. Nature 261, 675–677 (1976). https://doi.org/10.1038/261675a0