1 24, 504 (1975). 1. W. K. Hartmann, D. R. Davis, Icarus, 504 (1975). https://doi.org/10.1016/0019-1035(75)90070-6 model completely supported that hypothesis. All attempts to explain isotopic identity of Apollo samples and Earth’s mantle left too much alien impactor material in the resulting Moon. 2 338, 1040 (2012). 2. A. N. Halliday, Science, 1040 (2012). https://doi.org/10.1126/science.1229954 The idea that our Moon originated by collision of a large space body with Earthhas much shakier foundations than its almost universal acceptance might suggest. Before 2012 no published giant-impactcompletely supported that hypothesis. All attempts to explain isotopic identity of Apollo samples and Earth’sleft too much alienmaterial in the resulting Moon.

models. 3 338, 1047 (2012). 3. M. Ćuk, S. T. Stewart, Science, 1047 (2012). https://doi.org/10.1126/science.1225542 impact to be spinning near its approximately 2.7-hour limit of rotational stability. With that added energy, the impactor could blast part of the mantle into an orbiting cloud, a future moon polluted only by acceptably small traces of the impactor. The new mechanism of lunar–solar tidal resonance transfer, a descendant of George Darwin’s original lunar origin by tidal interaction, 4 171, 713 (1880). 4. G. H. Darwin, Phil. Proc. Roy. Soc. London, 713 (1880). https://doi.org/10.1098/rstl.1880.0020 angular momentum to near-modern values. In 2012 a new mechanism became the basis for the first successful giant-impactThat mechanism allowed early Earth at the moment ofto be spinning near its approximately 2.7-hour limit of rotational stability. With that added energy, thecould blast part of theinto an orbitinga future moon polluted only by acceptably small traces of theThe new mechanism of lunar–solar tidal resonance transfer, a descendant of George Darwin’s originalby tidal interaction,then reducedto near-modern values.

models have the same initial conditions as fission models of the 1960s—namely, a very rapidly spinning, partially segregated, early Earth. Elimination of excess angular momentum by the new mechanism removes once fatal objections to fission hypotheses. In these revitalized models late-stage core segregation increased the rotation rate beyond stability limits 5 74, 6034 (1969). 5. D. U. Wise, J. Geophys. Res., 6034 (1969). https://doi.org/10.1029/JB074i025p06034 mantle as lunar precursors. Subsequently a combination of tidal transfer; late-stage, backward-directed impacts; magnetic braking; drag in the solar wind; or escape of a silicate atmosphere, 5 74, 6034 (1969). 5. D. U. Wise, J. Geophys. Res., 6034 (1969). https://doi.org/10.1029/JB074i025p06034 angular momentum to near-modern levels. The newhave the same initial conditions as fissionof the 1960s—namely, a very rapidly spinning, partially segregated, early Earth. Elimination of excessby the new mechanism removes once fatal objections to fission hypotheses. In these revitalizedlate-stage core segregation increased the rotation rate beyond stability limitsto separate single or multiple parts of theasprecursors. Subsequently a combination of tidal transfer; late-stage, backward-directedmagnetic braking;in theor escape of a silicate atmosphere,other volatiles, small debris, or other moonlets reducedto near-modern levels.