Types of Mare Basalt

The lunar mare are very dark when seen with the naked eye. They are not all of the same color, however. Small differences are present in the amounts of ultraviolet, visible and infrared light reflected from the mare. Such color differences define 13 mare basalt types (shown here). These basalt types should mark changes in the minerals and chemistry of the mare basalts. However, the exact nature of over half of these mare units is poorly known. Most are located far from the Apollo landing sites. We have samples for only the 4 basalt types labeled Apollo 11, Apollo 12, Apollo 15, and Luna 20. Note -- The mare reflect only a small fraction (~7-10%) of visible light. Thus, most of the color differences in this map are invisible to the human eye. (Figure from Pieters (1978) Proceedings of 9th Lunar & Planetary Science Conf., vol. 3, p. 2826.)

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