A geological model of Mare Humorum

A model of Mare Humorum is presented as a working hypothesis. The model was deduced by combining theories and observations of the origin of the vittae (rays), rilles, wrinkle ridges, and faults. In this model, Mare Humorum consists of a basin which subsided by tilting and normal faulting. The tilting is deduced from the observation of the partial flooding of Gassendi and Dopplemeyer, on the north and south shores of the Mare, respectively. The faulting is deduced from the location of several linear features and the vittae, which are interpreted as being loci of sublimate deposition along infra-mare faults. The basin is filled by volcanic material which behaves incompetently with respect to the basement. Wrinkle ridges are features of the volcanic cover due to compression resulting from the subsidence. Rilles are features of the competent basement material, due to tension stresses occurring at the hinge areas of the subsiding basin and may be grabens and/or superficial dikes. The crustal weakness responsible for Mare Humorum could have originated by impact, but endogenous tectonism is the primary factor responsible for the present structure.