(LAC-42) Geologic map of the Mare Serenitatis region of the moon

The surface of the Moon is heterogeneous. Surface materials are classed on the basis of telescopic observations into map units, each having lateral continuity and a limited range of physiographic characteristics and optical properties (mainly polarization and albedo, the reflectivity under full moon illumination). Such units are analogous to the rock-stratigraphic formations of terrestrial geology. By application of the principles of superposition and intersection, these formations are arranged in order of relative age and grouped into time-stratigraphic units. Following terrestrial convention, the major time-stratigraphic units are designated systems, and their subdivisions series; corresponding to these are periods and epochs of time (Shoemaker, 1962; Shoemaker and Hackman, 1962).