 The Sea of Tranquility of the Moon | |
| Coordinates | 8°30′N31°24′E / 8.5°N 31.4°E /8.5; 31.4 |
|---|---|
| Diameter | 876 km (544 mi)[2][3] |
| Eponym | Sea of Tranquility |
Mare Tranquillitatis/træŋˌkwɪlɪˈteɪtɪs/ (Latin forSea of Tranquillity orSea of Tranquility)[a] is alunar mare that sits within the Tranquillitatis basin on theMoon. It containsTranquility Base, the first location on another celestial body to be visited by humans.
The mare material within the basin consists ofbasalt formed in the intermediate to young age group of theUpper Imbrian epoch. The surrounding mountains are thought to be of theLower Imbrian epoch, but the actual basin is probablyPre-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, andSerenitatis basins with two throughgoing rings of theProcellarum basin.Palus Somni, on the northeastern rim of the mare, is filled with the basalt that spilled over from Tranquillitatis.
This mare has a slight bluish tint relative to the rest of the Moon and stands out quite well when color is processed and extracted from multiple photographs. The color is likely due to higher metal content in the basaltic soil or rocks.[4]
Unlike many other maria, there is nomass concentration (mascon), or gravitational high, in the center of Mare Tranquillitatis. Mascons were identified in the center of other maria (such asSerenitatis orImbrium) from Doppler tracking of the fiveLunar Orbiter spacecraft in 1968.[5] The gravity field was mapped at higher resolution with later orbiters such asLunar Prospector andGRAIL, which unveiled an irregular pattern.
Mare Tranquillitatis was named in 1651 by astronomersFrancesco Grimaldi andGiovanni Battista Riccioli in theirlunar mapAlmagestum novum.[6][7]
Michael van Langren, in hisLumina Austriaca Philippica of1645, used the name "Mare Belgicum".
On February 20, 1965, theRanger 8spacecraft was deliberately crashed into the Mare Tranquillitatis at2°38′16″N24°47′17″E / 2.6377°N 24.7881°E /2.6377; 24.7881 (Ranger 8 crash site) after successfully transmitting 7,137 close-range photographs of the Moon in the final 23 minutes of its mission.[8][9]
Surveyor 5 landed in Mare Tranquillitatis on September 11, 1967, after transmitting 19,118 images of the Moon, and was the fifth lunar lander of the uncrewedSurveyor program.[10]
Mare Tranquillitatis was the landing site for the first crewed landing on the Moon on July 20, 1969, at 20:18UTC. AfterastronautsNeil Armstrong andBuzz Aldrin made a soft landing in theApollo 11Lunar ModuleEagle,Armstrong toldflight controllers on Earth, "Houston,Tranquility Base here. The Eagle has landed." The landing area at0°48′N23°30′E / 0.8°N 23.5°E /0.8; 23.5 (Tranquility Base) has been designatedStatio Tranquillitatis after Armstrong's name for it, and three small craters to the north of the base have been namedAldrin,Collins, andArmstrong in honor of the Apollo 11 crew.[11]
Apollo 11 landed at0°40′27″N23°28′23″E / 00.67408°N 23.47297°E /00.67408; 23.47297 (Apollo 11 landing site).[12][13]
Along the periphery of the mare are several bay-shaped features that have been given names:Sinus Amoris,Sinus Asperitatis,Sinus Concordiae, andSinus Honoris.[14]
These are three views of Mare Tranquillitatis on the Moon, taken by the mapping camera of theApollo 17 mission in 1972, facing south-southwest from an average altitude of 111 km on Revolution 36 of the mission. At the left is the east side of Mare Tranquillitatis, with the cratersFranz (bottom right),Lyell (dark floor, right of center), andTaruntius (upper left). The "bay" of dark mare (basalt) at left isSinus Concordiae, with "islands" of older, light highland material. At the right is the craterCauchy, which lies between theRupes Cauchy and Cauchy rille. The center photo shows the central mare with cratersVitruvius (lower right) andGardner (bottom center). At the horizon are lighter highlands at the southern margin of the mare, near theApollo 11 landing site. The craterJansen is visible at the edges of both the center and right photos. The right photo shows the western mare, with the cratersDawes (lower left) and the largePlinius (43 km diameter), with the Plinius Rilles in the foreground. These photos were taken within minutes of each other as thecommand moduleAmerica orbited the Moon. The Sun elevation drops from 46 degrees at left to 30 degrees at right.
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