Global tectonic patterns of the Moon

Abstract

Planetary tectonics provide a record of the myriad of processes that shape planetary surfaces and interiors. While there is a long history of mapping and modeling planetary tectonics, stresses from disparate processes are not generally captured by a single model. We present a comprehensive and general stress and tectonics model that can consider multiple stress-generating mechanisms simultaneously. The model is applicable to mass loading with arbitrary geometry, rotational and orbital perturbations, and arbitrary elastic lithosphere thicknesses. This wholistic approach to tectonic modeling has important implications for understanding both lunar evolution and tectonics across the solar system. We apply this model to the Moon, which exhibits a global pattern of thrust faults. The ubiquitous presence of young thrust faults suggests that isotropic contraction plays a dominant role. However, their non-random orientation requires additional stress-generating mechanisms that are not isotropic. Best-fit solutions correspond to models combining isotropic contraction with orbit recession, despinning, and South Pole-Aitken ejecta loading and the corresponding true polar wander. Contraction and despinning assuming an elastic shell with a thinner equatorial region can lead to misfits that are smaller than those assuming a constant thickness elastic shell. The young age of the faults favors recent contraction and recession; however, unrelaxed stresses from older processes combined with recent contractional stresses can also generate young faults. This possibility is supported by the Moon's ability to preserve a fossil figure.

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