Mare Tranquillitatis

Mare Tranquillitatis ("sea of tranquility") is a lunar mare that sits within the Tranquillitatis basin on Earth's moon. The mare material within the basin consists of basalt in the intermediate to young age group of the Upper Imbrian epoch. The surrounding mountains are thought to be of the Lower Imbrian epoch, but the actual basin is probably Pre-Nectarian. The basin has irregular margins and lacks a defined multiple-ringed structure. The irregular topography in and near this basin results from the intersection of the Tranquillitatis, Nectaris, Crisium, Fecunditatis, and Serenitatis basins with two throughgoing rings of the Procellarum basin. Palus Somni, on the northeastern rim of the mare, is filled with the basalt that spilled over from Tranquillitatis.

In 1965, the Ranger 8 spacecraft crashed in Mare Tranquillitatis, after successfully transmitting 7,137 photographs of the moon in the final 23 minutes of its mission. This mare also served as the landing site for the Apollo 11 lunar module, the first manned landing on the Moon. The landing area at 0.8° N, 23.5° E has been designated Statio Tranquillitatis, and three small craters to the north of the base have been named Aldrin, Collins and Armstrong in honor of the Apollo 11 astronauts.

Bays

Along the periphery of the mare are several bay-shaped features that have been given names.

Sinus Amoris

The "Bay of Love" extends northward from the northeast end of the Mare Tranquillitatis. It is located at selenographic coordinates 18.1° N, 39.1° E, and lies within a diameter of 130 km. To the north of the bay are the jumbled Montes Taurus peaks.

Near the southern end of the bay where it outlets into the Mare Tranquillitatis lies the Theophrastus crater. Along the western side is the flooded Maraldi crater and Mons Maraldi. Bordering the east side of the bay are the Carmichael and Hill craters. There are some low ridges in the central part of the bay, but otherwise it is relatively featureless.

Sinus Asperitatis

The "Bay of Roughness" is an area of lunar mare that extends southward from the Mare Tranquillitatis until it joins the Mare Nectaris to the southeast. It is bordered along the western and eastern sides by continental regions of irregular terrain. The selenographic coordinates of this feature are 3.8° S, 27.4° E, and it has a diameter of 206 km.

In the northern part of this mare is the small Toricelli crater. At the southern end is the prominent crater pair of Theophilus and Cyrillus. On the border between Sinus Asperitatis and the Mare Nectaris is the Mädler crater.

Sinus Concordiae

The narrow "Bay of Harmony" lies along the eastern edge of the Mare Tranquillitatis. Along its northern border is an area called the Palus Somni, while the southern border is an area of irregular terrain that contains the ruined Da Vinci crater. The selenographic coordinates of this bay are 10.8° N, 43.2° E, and it has an overall diameter of 142 km.

Sinus Honoris

The "Bay of Honour" is located along the western edge of the Mare Tranquillitatis. The selenographic coordinates of this feature are 11.7° N, 18.1° E, and it has a diameter of 109 km.

Sinus Honoris has a wide mouth and is bordered by uneven terrain to the north and southwest. Where the bay joins the mare, rilles systems extend to the north and south. The northern system is designated Rimae Maclear, after the Maclear crater just to the east of the bay. At the southern end of the bay entrance is the Rimae Sosignes, named for the Sosigenes crater to the south. At the west end of the bay is a finger of mare surface that extends to the northwest for almost 100 km.

In the arts

Mare tranquilitatis is also the name of a composition of music by composer Vangelis on his 1976 album, Albedo 0.39 and is in reference to the selenographical term.

Sea Of Tranquility is the name of the final track on the 1994 album Embedded by industrial death metal band Meathook Seed.