Mare Serenitatis

28.0°N, 17.5°E

Mare Serenitatis, the ‘Sea of Serenity’, is a large, nearly round lava expanse with an area of about 500 × 700 km. Like all the other maria, Mare Serenitatis is also the centre of a gravitational anomaly (a mascon), and it is also a typical multiring basin with at least two basin ramparts. The darker edge regions suggest that this lava is richer in metallic components such as iron and titanium, and that it emerged earlier in the period of lava flows than the lava in the central region. Around the edge, the lava is also thinner than in the centre of the mare.

From soil samples obtained during the Apollo 17 mission (the landing site was on the southeastern edge of the mare), geologists were able to determine that the lava in Mare Serenitatis erupted at different times, almost 800 million years apart (between 3.8 and 3.0 billion years ago). Even on the Earth and for terrestrial geological sequences, this is an enormous time-span. This period was the most active one for lunar volcanism. About 3 billion years ago, the lava flows gradually ceased, but did not stop completely. The last active phase of lava production took place about 1 billion years ago.

The southwestern edge of Mare Serenitatis is bordered by Montes Haemus, a range of mountains that is about 400 km long. The range is the visible remnant of the wall of the Serenitatis Basin.