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Evidence for a Past High-Eccentricity Lunar Orbit

Science  04 Aug 2006:
Vol. 313, Issue 5787, pp. 652-655
DOI: 10.1126/science.1128237

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Abstract

The large differences between the Moon's three principal moments of inertia have been a mystery since Laplace considered them in 1799. Here we present calculations that show how past high-eccentricity orbits can account for the moment differences, represented by the low-order lunar gravity field and libration parameters. One of our solutions is that the Moon may have once been in a 3:2 resonance of orbit period to spin period, similar to Mercury's present state. The possibility of past high-eccentricity orbits suggests a rich dynamical history and may influence our understanding of the early thermal evolution of the Moon.

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