Radiometric dating of moon rocks
(NASA) The terrae, or highlands, constitute about two-thirds of the near side of the Moon and exhibit a wide range of topographic relief.
This is the highest and most rugged topography on the Moon, where local relief in many areas is up to 5000 meters.
But not until the 1960s---and the inception of space travel with its sophisticated satellites and probes and the eventual Moon landing---did man begin to appreciate the significance of the Moon as a planet.
We know from lunar rock specimens and surface features that the maria are vast layers of thin basaltic lava, which flowed into depressions and flooded large parts of the lunar surface.
Long ago the distance from Earth to the Moon was measured and the diameter of the Moon determined.
Early astronomers realized that the Moon's rotation period and its period of revolution are the same; thus it keeps one hemisphere facing Earth at all times.
Nonetheless, many of the facts listed in Table 1 were known long before we began to explore space; they represent years of diligent study.
For example, it was discovered centuries ago that the Moon revolves about Earth and not the Sun and is thus a natural satellite (the largest in the inner solar system).
The importance of the Moon in studying the principles of geology is that it provides an insight into the basic mechanics of planetary evolution and events that occurred early in the solar system.