Mare basalt
Mare basalt is the dark volcanic rock that fills the Moon's large lowland plains, the maria.
The dark patches on the Moon visible with the naked eye are the maria, Latin for seas, though they contain no water. They are vast plains of mare basalt, lava that welled up from the Moon's interior and flooded large impact basins.
Apollo samples show that most mare basalts erupted between about 3.9 and 3.1 billion years ago, and China's Chang'e 5 mission returned basalts about 2 billion years old, showing that volcanism lasted longer than many expected. Mare basalts are richer in iron, and sometimes titanium, than Earth basalts and contain no water-bearing minerals.
Several lunar meteorites found in deserts and Antarctica are mare basalts. Compared with the bright highland meteorites, they have dark pyroxene, plagioclase and sometimes abundant ilmenite. Because they come from random places on the Moon, including the far side, they add to the record from the six Apollo landing sites and the Soviet Luna and Chinese Chang'e missions.
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