Close Geodynamo, solar wind, and magnetopause 3.4 to 3.45 billion years ago,
Tarduno, J. A., R. D. Cottrell, M. K. Watkeys, A. Hofmann, P. V. Doubrovine, E. A. Mamajek, D. Liu, D.G. Sibeck, L. P. Neukirch, Y. Usui (2010),
Science, 327 p. 1238–1240,
10.1126/science.1183445.