To its upper left is Mare Serenitatis, the Sea of Serenity, and Mare Imbrium, the Sea of Rains. All three are roughly circular, the result of lava’s flooding gigantic craters left by meteorite impacts when the moon was young. To their left is the larger, more formless Oceanus Procellarum, the Ocean of storms, with Mare Humorum (sea of Moisture) and Mare Nubium (sea of Clouds) below it, The large bright areas are mountainous, cratered terrain made of lighter colored rock.