  Three principal concepts regarding lunar formation have been examined: the
accretion hypothesis, the mega-impact theory, and the multi-impact model. The
multi-impact model amalgamates the salient facets of the mega-impact theory and
the accretion hypothesis. As per this model, fragments of the terrestrial crust
are ejected into space during collisions with numerous planetesimals
(proto-asteroids) with diameters around 10-100 kilometers. This ejecta
interacts with the accretion disk, augmenting its mass. Different models of
lunar formation yield varied conclusions regarding the quantity of lunar water,
its subsurface distribution, and isotopic composition. Geomorphological
structures in the lunar polar regions (smoothed craters, landslides, regular
patterns) suggest the presence of a substantial permafrost layer with an
approximate thickness of a kilometer.
