Chemical Composition of Lunar Surface
Have you ever wondered what causes the surface of the Moon to be dark in some areas and light in other ones? Have you ever gone farther and asked yourself maybe dark areas are oceans of the Moon? Indeed, in past, this was one of common thoughts, but today we know there is no ocean or even a very small pond on the surface of the Moon.
Dark areas called maria (Latin for “seas”, singular mare) are vast solidified pools of ancient basaltic lava while light areas called terrae or more commonly highlands are rough highlands largely made of anorthosite. Basalt forms when lava cools rapidly while anorthosite forms from slow cooling of lava. Differences in chemical composition and formation make rocks of maria less reflective and hence darker to the naked eye.