Mare Tranquillitatis (

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for Sea of Tranquillity or Sea of Tranquility) is a

lunar mare The lunar maria ( ; mare ) are large, dark, basaltic plains on Earth's Moon, formed by lava flowing into ancient impact basins. They are less reflective than the "highlands" as a result of their iron-rich composition, and hence appear dark to ...

that sits within the Tranquillitatis basin on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

. It contains

Tranquility Base Tranquility Base () is the site on the Moon where, in July 1969, humans landed and walked on a celestial body other than Earth for the first time. On July 20, 1969, Apollo 11 crewmembers Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Mo ...

, the first location on another celestial body to be visited by humans. The mare material within the basin consists of

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

formed 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. 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. Unlike many other maria, there is no mass concentration (mascon), or gravitational high, in the center of Mare Tranquillitatis. Mascons were identified in the center of other maria (such as Serenitatis or Imbrium) from Doppler tracking of the five Lunar Orbiter spacecraft in 1968. The gravity field was mapped at higher resolution with later orbiters such as

Lunar Prospector ''Lunar Prospector'' was a spacecraft that orbited the Moon for 19 months in 1998-99. From a low polar orbit, it mapped surface composition including lunar hydrogen deposits, measured magnetic and gravity fields, and studied lunar outgassing e ...

and GRAIL, which unveiled an irregular pattern. File:Tranquillitatis basin topo.jpg, Topographic map File:Tranquillitatis basin GRAIL gravity.jpg, Gravity map based on GRAIL

Naming

Mare Tranquillitatis was named in 1651 by astronomers Francesco Grimaldi and

Giovanni Battista Riccioli Giovanni Battista Riccioli (17 April 1598 – 25 June 1671) was an Italian astronomer and a Catholic priest in the Jesuit order. He is known, among other things, for his experiments with pendulums and with falling bodies, for his discussion of ...

in their lunar map ''Almagestum novum''. Michael van Langren, in his ''Lumina Austriaca Philippica'' of 1645, used the name "Mare Belgicum".

Landings

On February 20, 1965, the Ranger 8

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

was deliberately crashed into the Mare Tranquillitatis at after successfully transmitting 7,137 close-range photographs of the Moon in the final 23 minutes of its mission. 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 uncrewed Surveyor program.

Apollo 11

Mare Tranquillitatis was the landing site for the first crewed landing on the Moon on July 20, 1969, at 20:18 UTC. After

astronauts An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a List of human spaceflight programs, human spaceflight program to serve as a commander or crew member of a spa ...

Neil Armstrong Neil Alden Armstrong (August 5, 1930 – August 25, 2012) was an American astronaut and aerospace engineering, aeronautical engineer who, in 1969, became the Apollo 11#Lunar surface operations, first person to walk on the Moon. He was al ...

and

Buzz Aldrin Buzz Aldrin ( ; born Edwin Eugene Aldrin Jr.; January 20, 1930) is an American former astronaut, engineer and fighter pilot. He made three extravehicular activity, spacewalks as pilot of the 1966 Gemini 12 mission, and was the Lunar Module Eag ...

made a soft landing in the

Apollo 11 Apollo 11 was a spaceflight conducted from July 16 to 24, 1969, by the United States and launched by NASA. It marked the first time that humans Moon landing, landed on the Moon. Commander Neil Armstrong and Lunar Module pilot Buzz Aldrin l ...

Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed s ...

''Eagle'', Armstrong told

flight controller Flight controllers are personnel who aid space flight by working in mission control centers such as NASA's Christopher C. Kraft Jr. Mission Control Center or ESA's European Space Operations Centre. Flight controllers work at computer consoles a ...

s on Earth, "Houston,

here. The Eagle has landed." The landing area at has been designated '' Statio Tranquillitatis'' after Armstrong's name for it, and three small craters to the north of the base have been named Aldrin, Collins, and Armstrong in honor of the Apollo 11 crew. Apollo 11 landed at .

Bays

Along the periphery of the mare are several bay-shaped features that have been given names: Sinus Amoris, Sinus Asperitatis, Sinus Concordiae, and Sinus Honoris.

Views

These are three views of Mare Tranquillitatis on the Moon, taken by the mapping camera of the

Apollo 17 Apollo 17 (December 7–19, 1972) was the eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, ...

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 craters Franz (bottom right), Lyell (dark floor, right of center), and Taruntius (upper left). The "bay" of dark mare (basalt) at left is Sinus Concordiae, with "islands" of older, light highland material. At the right is the crater

Cauchy Baron Augustin-Louis Cauchy ( , , ; ; 21 August 1789 – 23 May 1857) was a French mathematician, engineer, and physicist. He was one of the first to rigorously state and prove the key theorems of calculus (thereby creating real a ...

, which lies between the Rupes Cauchy and Cauchy rille. The center photo shows the central mare with craters

Vitruvius Vitruvius ( ; ; –70 BC – after ) was a Roman architect and engineer during the 1st century BC, known for his multi-volume work titled . As the only treatise on architecture to survive from antiquity, it has been regarded since the Renaissan ...

(lower right) and Gardner (bottom center). At the horizon are lighter highlands at the southern margin of the mare, near the

landing site. The crater Jansen is visible at the edges of both the center and right photos. The right photo shows the western mare, with the craters Dawes (lower left) and the large Plinius (43 km diameter), with the Plinius Rilles in the foreground. These photos were taken within minutes of each other as the command module ''America'' orbited the Moon. The Sun elevation drops from 46 degrees at left to 30 degrees at right.

In popular culture

* ''

Sea of Tranquility Mare Tranquillitatis (Latin for Sea of Tranquillity or Sea of Tranquility) is a lunar mare that sits within the Tranquillitatis basin on the Moon. It contains Tranquility Base, the first location on another celestial body to be visited by hu ...

'', a 2022 book by Emily St. John Mandel

Gallery

File:Mare Tranquillitatis map.jpg, Map of the Sea of Tranquility, showing the landing sites of

Apollo 16 Apollo 16 (April 1627, 1972) was the tenth human spaceflight, crewed mission in the United States Apollo program, Apollo space program, administered by NASA, and the fifth and penultimate to Moon landing, land on the Moon. It was the second o ...

, and Surveyor 5. To the southeast is Mare Fecunditatis, to the northeast is Mare Crisium, to the northwest is Mare Serenitatis, and to the south is Mare Nectaris. File:AP11 FINAL APPROACH.ogv,

lands the Apollo 11 Lunar Module ''Eagle'' on the Moon at Mare Tranquillitatis, July 20, 1969, creating

. Starts approximately 6200 feet from the surface. File:Buzz salutes the U.S. Flag.jpg,

salutes the U.S. flag on Mare Tranquillitatis during Apollo 11 in 1969. File:Mare Tranquillitatis pit crater.jpg, High Sun view of the Mare Tranquillitatis pit

crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

revealing boulders on an otherwise smooth floor. Image is 400 meters wide, north is up, NAC M126710873R. File:Aldrin Apollo 11 (jha).jpg, "A man on the Moon", the first photograph taken on the Moon, was taken on Mare Tranquillitatis.

References

{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Apollo 11 Articles containing video clips Tranquillitatis Tranquillitatis Tranquillitatis