Lunar Geography

It is important to be familiar with the type of major features of the Moon prior to search­ing for the Apollo landing sites. In 1651, a Jesuit astronomer named Giovanni Battista Riccioli created and published a system of nomenclature still in use today. Originally written in Latin, many of the lunar names have been Anglicized. For the comfort of the readers, Seas, Ocean, Bay, and other English nomenclature will henceforth be used in this book, except in one case. Mare Cognitum will be used in its Latin form, because it translates to “the sea that has become known”, which is extraordinarily awkward.

• Mare or Sea – The near side of the Moon is characterized by large, dark, seem­ingly smooth areas that early astronomer Riccioli called Mare, or Sea (with the plural Marias or Seas). From the Apollo missions, scientists now know that what looked like water to early astronomers is comprised of vast fields of basalt lava flows. In keeping with the water-based nomenclature for the Moon, Riccioli named one oceanus (ocean), and several dark areas as lacus (lake), palus (marsh) and sinus (bay). The ocean, lake, marsh and bay have the same nature and characteristics, but differ in size.

• Major craters – The Moon is obviously pockmarked with craters, the majority being impact craters left from meteors over the eons. Two of the larger craters are named for the pioneering astronomers Tycho Brache and Copernicus. The meteor impacts that created these landmark craters spread lunar debris across the near face of the Moon, and influenced NASA planners in their selection of Apollo landing sites, as will be seen in the Apollo mission chapters of this book.

• Highlands and Mountain Ranges – The highlands and mountain ranges of the Moon provide the brightest images of the Moon. Some mountain ranges, such as the Apennines and the Alps are actually parts of the crater rim surrounding the Sea of Rains. Other peaks are part of mountain ranges that project above the surface as part of fluid dynamics resulting from the liquefaction of surface rock following a meteor impact. Apollo landing sites in the highlands gathered scien­tific data, rock and soil samples from these regions to provide a comparison with the basin material, as detailed in the Apollo mission chapters of this book.