and light areas. Those dark areas are often referred to as maria—the plural form of the Latin word mare, which means “sea.” Early Moon watchers thought those regions were watery oceans, but a close look with a telescope or a pair of binoculars shows no water on the surface, just rocky plains. The low-altitude maria formed as volcanic vents called lunar domes emptied out their molten basaltic lava and flooded the surface. The light areas are called the lunar highlands. They are mostly hilly regions that lie at higher altitudes than the maria. The whole surface is peppered with impact craters,
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