Mare Imbrium (pictured in the foreground), or the “Sea of Showers,” is one of the largest lunar maria on the Moon’s surface. Lunar maria are vast basaltic plains that were formed by ancient volcanic eruptions, and they are less reflective than the highlands of the Moon, making them appear darker, and thus referred to as “seas.”
Located in the northwest region of the Moon’s near side, Mare Imbrium has a diameter of about 1,145 kilometers (711 miles). The mare is predominantly filled with solidified lava, creating a relatively flat surface, although it is punctuated by a few smaller impact craters and wrinkle ridges caused by the contraction of the basaltic lava.
The origin of Mare Imbrium dates back to the early history of the Solar System, around 3.5 billion years ago. An enormous asteroid or comet collided with the Moon, creating the Imbrium Basin. This basin was then filled with lava erupting from the Moon’s interior, which solidified to form the mare’s flat plains. The impact that created Mare Imbrium was so intense that it left marks radiating out from the basin, extending across large portions of the lunar surface.
Several prominent features surround Mare Imbrium, including the Montes Carpatus, a mountain range on the southern edge of the mare, the Montes Apenninus, a mountain range to the southeast featuring some of the Moon’s highest peaks, the Montes Alpes, a mountain range to the east of the mare, housing the famous Vallis Alpes, a large valley, and the Sinus Iridum, also known as the Bay of Rainbows, a picturesque feature to the northwest.
Mare Imbrium has been a prominent target for both manned and unmanned lunar missions, and its features have been explored and studied in detail. The Apollo 15 mission, for example, landed near the Apennine mountain range at the southeastern edge of Mare Imbrium. The study of Mare Imbrium and other lunar maria helps scientists understand the geological history of the Moon and offers insights into the processes that have shaped other celestial bodies in our Solar System.