Mare Tranquillitatis

Mare Tranquillitatis (Latin for Sea of Tranquility or Sea of Tranquillity; see spelling differences) is a lunar mare that sits within the Tranquillitatis basin on the Moon. The mare material within the basin consists of basalt 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.[3]

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.[4] The gravity field was mapped at higher resolution with later orbiters such as Lunar Prospector and GRAIL, which unveiled an irregular pattern.

Tranquillitatis basin topo

Topographic map

Tranquillitatis basin GRAIL gravity

Gravity map based on GRAIL

Moon names
Lunar nearside with major maria and craters labelled.
Mare Tranquillitatis
The Sea of Tranquility of the Moon
Coordinates8°30′N 31°24′E / 8.5°N 31.4°ECoordinates: 8°30′N 31°24′E / 8.5°N 31.4°E
Diameter873 km (542 mi)[1][2]
EponymSea of Tranquility


Mare Tranquillitatis was named in 1651 by astronomers Francesco Grimaldi and Giovanni Battista Riccioli in their lunar map Almagestum novum.[5][6] Earlier lunar cartographers had given the feature different names. Michael van Langren's 1645 map calls it "Mare Belgicum" (Latin for the Belgic Sea), the classical name of the North Sea[7][8] And Johannes Hevelius included it within Pontus Euxinus (after the classical name for the Black Sea) in his 1647 map.[7][9]


Apollo-11 nasa 536
A view of the Apollo 11 landing site at center, facing west, with Maskelyne crater in right foreground

In February 1965, the Ranger 8 spacecraft was deliberately crashed into the Mare Tranquillitatis, after successfully transmitting 7,137 close-range photographs of the Moon in the final 23 minutes of its mission.[10]

Surveyor 5 landed in Mare Tranquillitatis on September 11, 1967, and was the fifth lunar lander of the uncrewed Surveyor program.


This mare was also the landing site for the first crewed landing on the Moon on July 20, 1969, at 20:18 UTC. After astronauts Neil Armstrong and Buzz Aldrin made a smooth touchdown in the Apollo 11 Lunar Module named Eagle, Armstrong told flight controllers on Earth, "Houston, Tranquility Base here. The Eagle has landed." The landing area at 0.8° N, 23.5° E 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.[11]

The Apollo 11 landed at 00.67408° North latitude, 23.47297° East longitude.[12][13]


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.[14]


Mare Tranquilitatis AS17-M-1647-1653-1659

These are three views of Mare Tranquillitatis on the Moon, taken by the mapping camera of the Apollo 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 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 right is the crater Cauchy, which lies between the Rupes Cauchy and Cauchy rille. The center photo shows the central mare with craters Vitruvius (lower right) and Gardner (bottom center). At the horizon are lighter highlands at the southern margin of the mare, near the Apollo 11 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.

Irregular mare patch

An Ina-like feature is also founded in Mare Tranquillitatis in the vicinity of Maskelyne,[15][16][17] one of many newly discovered young volcanic deposits on the Moon, founded by the Lunar Reconnaissance Orbiter (LRO).

During eclipses

During eclipses with long totality, temperatures slowly plunges, as being in a basin, it remains nearly high in many areas but slightly cooler in the southeast. The highest are in some of the large craters of the basin such as Plinius. They were first known in the mid-infrared image of the Moon was taken during a September 1996 lunar eclipse by the SPIRIT-III instrument aboard the orbiting Midcourse Space Experiment (MSX) satellite.[18][19]

In the arts

  • Israeli psych-progressive rock band Jericho Jones recorded a song named "Mare Tranquilitatas" as the opening track of their UK album release (1971) Junkies, Monkeys & Donkeys. The band is also known as The Churchills.
  • "Mare Tranquillitatis" 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 also a song by the progressive rock band Barclay James Harvest, included in their 1977 album Gone to Earth. The composition was written by the band keyboardist Stuart "Woolly" Wolstenholme.
  • Singer songwriter Tommy Shaw (best known for his work with the rock band Styx) is associated with a number of references to the Sea of Tranquility. Tranquility Base Songs is his publishing company. He called his farm Tranquility Base Farms. A number of his songs mention Tranquility Base or simply "tranquility." Examples include: "Boat on the River", "And all roads lead to Tranquility Base" (from the 1979 album Cornerstone), "Everything Is Cool" – "We are a Sea of Tranquillity" (from the 1999 album Brave New World), and "These Are the Times" – "We know the end will bring tranquility" (from the 2003 album Cyclorama).
  • Sea of Tranquillity is the title of a 1994 novel by Paul Russell.
  • Six Finger Satellite included a song named "Sea of Tranquility, Parts 1 & 2" from their 1998 album Law of Ruins.
  • The Dutch stoner rock/space rock band 35007 released a 2001 EP named Sea of Tranquility.
  • Dutch producer Maarten van der Vleuten/In-Existence released a song titled "Mare Tranquillitatis" on his album Vow Of Silence released on Tonefloat in 2005.
  • Howard Korder wrote a play called Sea of Tranquility.
  • The Brazilian rock band from the 80s RPM mentions the Sea of Tranquillity in their hit song "Radio Pirata".
  • "Sea of Tranquillity" is a song by space ambient artist, John Stanford.
  • The Sea of Tranquility is the name of a book by Mark Haddon, author of the best-selling The Curious Incident of the Dog in the Night-Time.
  • The Sea of Tranquility is the name of a book by Katja Millay.
  • Transmissions from The Sea of Tranquility is the name of the album by The Samples, released September 30, 1997.
  • The Houston, Texas based progressive metal band Galactic Cowboys recorded a song named "Sea of Tranquility" as the sixth track on their 1991 self-titled debut album.
  • The hardcore punk band Jeromes Dream released a song called "Remember the Sea of Tranquility on their split 7" with Usurp Synapse.
  • In the 1987 film Can't Buy Me Love, Ronald Miller (played by Patrick Dempsey) describes the Sea of Tranquility to Cindy Mancini (played by Amanda Peterson) while viewing it through a telescope on their final date.
  • In the anime Log Horizon 2, Mare Tranquillitatis is the name of the sea inside the dimension where characters go when they die.
  • "Mare Tranquillitatis" is the name of a 2016 song by Adam Young.
  • Sea of Tranquility appears in chapter 78 of Life of Pi by Yann Martel.
  • In Touhou 15, Legacy of Lunatic Kingdom, Mare Tranquillitatis is the setting of the final two stages of the game.
  • In the Alien franchise of movies, Weyland-Yutani (Often referred to as "The company") has a major corporate headquarters in the Sea of Tranquility. (Mentioned in the 1979 film Alien as seen on the opening screen of the "Mother" computer, among other sources)
  • In the book Artemis, the city Artemis is located in the Sea of Tranquility, just north of the Moltke Foothills. The Apollo 11 Visitor Center and reactor/smelter complex is also located in the Sea of Tranquility, 40 and 1km north and south of Artemis respectively.
  • In John Adams' opera Nixon in China, Act 1 Scene 1, Richard Nixon references "the Earth's Sea of Tranquility".
  • In the Power Rangers' tenth anniversary special Forever Red, Lord Zedd's Zord of Serpentera is stated to be located in the Sea of Tranquility, which is where the last known remnants of the Machine Empire have based themselves, digging Serpentera up and planning to use it to destroy Earth in revenge for the death of their leader, King Mondo.
  • The Sea Of Tranquility is the name of an EP by musician T E Morris.


Mare Tranquillitatis map

Map of the Sea of Tranquility, showing the landing sites of Apollo 11, Apollo 17, Apollo 16, 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.

Buzz salutes the U.S. Flag

Buzz Aldrin salutes the U.S. flag on Mare Tranquillitatis during Apollo 11 in 1969.


  1. ^ "Moon Mare/Maria". Gazetteer of Planetary Nomenclature. USGS Astrogeology. Retrieved 2010-08-20.
  2. ^ "Mare Tranquillitatis". Nasa. Archived from the original on 2008-10-13.
  3. ^ "Wayback Machine" (PDF). 20 October 2014. Retrieved 10 April 2018.
  4. ^ P. M. Muller, W. L. Sjogren (1968). "Mascons: Lunar Mass Concentrations". Science. 161 (3842): 680–684. Bibcode:1968Sci...161..680M. doi:10.1126/science.161.3842.680. PMID 17801458.
  5. ^ The Face of the Moon. Kansas City, MO: Linda Hall Library. 1989. p. 7. Archived from the original on 2012-01-06.
  6. ^ "Mare Tranquillitatis naming origin". Lunar Planetary Institute.
  7. ^ a b Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999).
  8. ^ Langrenus map of the Moon (1645)
  9. ^ Hevelius map of the Moon (1647)
  10. ^ Grayzeck, Dr. Ed (July 1, 2013). "Ranger 8". National Space Data Centre. Washington, D.C.: NASA. Archived from the original on July 31, 2013. Retrieved July 31, 2013.
  11. ^ Gaherty, Geoff (April 19, 2013). "How to See Where Astronauts Walked on the Moon". Retrieved March 3, 2018.
  12. ^ "Apollo 11 Landing Site". Smithsonian National Air and Space Museum. Retrieved October 12, 2017.
  13. ^ Accessed October 12th, 2017
  14. ^ Wood, Chuck (2006-08-10). "Is it Love or a Sinus Infection?". Lunar Photo of the Day. Retrieved 2006-08-10.
  15. ^ Wood, Charles. "Strange Little IMPs." Sky and Telescope, February 2015 issue.
  16. ^ Stooke, P. J. (March 19–23, 2012). Lunar Meniscus Hollows (PDF). 43rd Lunar and Planetary ScienceConference. The Woodlands, Texas (published March 2012). Bibcode:2012LPI....43.1011S. 1011.
  17. ^ Braden, S. E.; Robinson, M. S.; Stopar, J. D.; van der Bogert, C. H.; Hawke, B. R. (March 18–22, 2013). Age and Extent of Small, Young Volcanic Activity on the Moon (PDF). 44th Lunar and Planetary Science Conference. The Woodlands, Texas (published March 2013). p. 2843. Bibcode:2013LPI....44.2843B.
  18. ^ NASA Astronomy Picture of the Day: Eclipsed Moon in Infrared (8 November 2003)
  19. ^ Wood, Chuck (May 13, 2005). "Hotspots identified". Lunar Photo of the Day.
Al-Bakri (crater)

Al-Bakri (Arabic: البكري‎) is a small lunar impact crater on the northwest edge of Mare Tranquillitatis and is named after the Spanish Arab geographer and historian Abu Abdullah al-Bakri. It is just south of the eastern arm of the Montes Haemus that borders the Mare Serenitatis to the north. To the east-northeast is the prominent crater Plinius and Ross to the south-southeast. South of the crater are the rilles of the Rimae Maclear.

Al-Bakri was designated Tacquet A prior to being assigned a name by the IAU. The tiny Tacquet lies to the northwest on the Mare Serenitatis.

Aldrin (crater)

Aldrin is a tiny impact crater located on the southern part of the Mare Tranquillitatis, to the east of Sabine. It is located about 50 kilometers to the northwest of the Apollo 11 landing site. Named after Buzz Aldrin, the crater is the westernmost of a row of three craters named in honor of the Apollo 11 crew members. About 30 kilometers to the east is the landing site of the Surveyor 5 lunar probe.

This crater was previously identified as Sabine B before being named by the IAU. Sabine itself is to the west of Aldrin.

Alfraganus (crater)

Alfraganus is a small lunar impact crater that lies in the rugged highland region to the southwest of the Mare Tranquillitatis and is named after Alfraganus. Northwest of Alfraganus is the crater Delambre, to the west is Taylor, and to the south is the irregular Zöllner. The rim of Alfraganus is circular and retains a sharp edge that has not received a significant amount of wear due to subsequent impacts. The interior floor is roughly half the diameter of the crater rim.

Ariadaeus (crater)

Ariadaeus is a small, bowl-shaped lunar impact crater on the western shores of Mare Tranquillitatis. It lies about 40 km north of the crater Dionysius, and about 120 km west-southwest of Arago, it is also located about 70 km west of nearby Manners, nearly east of Cayley and over 115 km south of Sosigenes. The crater is joined along the northeast rim by the slightly smaller Ariadaeus A, and the two form a double-crater.

Its diameter is 11.2 km long and is 1,800 meters deep. The area is about 80 km² and the perimeter is over 30 km.

This crater marks the eastern extent of the rille designated Rima Ariadaeus. This wide rille extends in a nearly straight line to the west-northwest, passing just to the north of the crater Silberschlag. Other rille systems lie in the vicinity, including the Rimae Ritter to the southeast and Rimae Sosigenes to the northeast.

The crater was named after Philip III of Macedon (Arrhidaeus).

Armstrong (crater)

Armstrong is a small lunar impact crater located in the southern part of the Mare Tranquillitatis. It lies about 50 kilometers to the northeast of the Apollo 11 landing site. Named after Neil Armstrong, the crater is the easternmost of the row of three craters named in honor of the Apollo 11 crew members. To the north is the Ranger 8 impact site.

This crater was previously identified as Sabine E before being renamed by the IAU. Sabine itself is located due west of Armstrong.

Aryabhata (crater)

Aryabhata, named after Indian astronomer Aryabhata, is the remnant of a lunar impact crater located in the eastern Mare Tranquillitatis. The crater has been almost submerged by lava-flow, and now only an arc-shaped ridge formed from the eastern half of the rim remains above the lunar mare. This crater was previously identified as Maskelyne E before being named by the IAU in 1979. Maskelyne itself is to the southwest. Other craters nearby are the tiny Donna to the east-northeast, Zähringer almost to the east, Menzel to the east-southeast and Wallach nearly to the southwest.

Beketov (crater)

Beketov is a small lunar impact crater that lies in the northern reaches of the Mare Tranquillitatis and is named after Nikolay Beketov. To the south is the ghost crater Jansen R. Northeast of Beketov, along the edge of the mare, is the crater Vitruvius located about 53 km. Beketov was previously designated Jansen C before being named by the IAU. The flooded crater Jansen itself lies nearly 70 km to the south. Other nearby large craters are Dawes located about 75 km west and Fabbroni to the north.

The diameter is 8.4 km and being about 1,000 meters deep. Also, the area is more than 50 km² and its perimeter is about 25 km.

Other nearby geographical features include Dorsa Barlow to the southeast and Rima Jansen to the south.

Carrel (crater)

Carrel is a small lunar crater on the Mare Tranquillitatis. It has a somewhat distorted appearance, having a slight protruding bulge in the northwest rim. The interior is somewhat irregular, with ridges and some slumped material. This crater lies across a ridge in the surface of the mare.

This crater was previously designated as Jansen B before being given its current name by the IAU in 1979 in honour of the scientific contributions of the Nobel-winning French scientist Alexis Carrel. The lava-flooded crater Jansen lies about 90 km northeast.

Cayley (crater)

Cayley is a small lunar impact crater that is located in a lava-flooded region to the west of Mare Tranquillitatis and is named after the 19th century British mathematician Arthur Cayley. It lies almost directly to the south of the smaller crater De Morgan being about 7 km and the larger D'Arrest. West and 25+ km slightly west of Cayley is Whewell, a crater of about the same dimensions. To the north is a linear rille designated Rima Ariadaeus, which follows a course to the east-southeast.

Collins (crater)

Collins is a tiny lunar impact crater located on the southern part of the Mare Tranquillitatis. It is located about 25 kilometers to the north of the Apollo 11 landing site. Named after Michael Collins, the crater is the central member of the row of three craters named in honor of the Apollo 11 crew members. About 15 kilometers to the west-northwest is the landing site of the Surveyor 5 lunar probe.

This crater was previously identified as Sabine D before being renamed by the IAU. Sabine itself is to the west of Collins.

Crile (crater)

Crile is a tiny lunar impact crater. It is roughly circular and cup-shaped, with interior walls that slope down to the midpoint. The crater lies in the Palus Somni, between the Mare Crisium to the east and Mare Tranquillitatis to the west.

This formation was previously designated Proclus F before being renamed by the IAU in 1976. Proclus itself is located to the north-northeast. The crater is named for American surgeon, George Washington Crile.Nearby prominent craters include Glaisher nearly to the east and Lyell to the west.

D'Arrest (crater)

D'Arrest is a lunar impact crater that is located in the lava-flooded region to the west of the Mare Tranquillitatis and is named after the German astronomer Heinrich Louis d'Arrest. It lies to the southeast of the crater Agrippa, north of Theon Senior and Junior, the first being about 130 km, and northwest of Delambre. Just to the northeast are the small, bowl-shaped craters De Morgan and Cayley. Also further east is Dionysius being about 60 km.

The outer rim of D'Arrest is broken in several places, with a gash at the south end and a wide gap to the northeast where only a low ridge remains in place of the original wall. The interior has been resurfaced by lava, leaving a nearly flat, featureless floor. The surviving rim is low and worn, with ridges connecting it to the south and southwest.

Delambre (crater)

Delambre is a lunar impact crater that lies to the southwest of Mare Tranquillitatis, in the central highland region. To the west is the crater pair of Theon Junior and Theon Senior, the latter being more distant and located to the northwest. To the north are several craters including D'Arrest, Dionysus and the small Schmidt. Also the south are Taylor and Alfraganus, the first located more than a crater diameter.

It is 52 kilometers in diameter and 3.5 kilometers in depth. It was named for Jean Baptiste Joseph Delambre, an 18th-century French astronomer.The rim of Delambre has a terraced interior, with a tiny craterlet lying along the northern rim. In the south is a low cut forming a slight notch. The crater interior has an irregular surface. It has high walls, with some peaks reaching 15,000 feet. Delambre was photographed by the unmanned probe Ranger 8 on its descent towards Mare Tranquillitatis. Delambre is from the Upper Imbrian epoch, which lasted from 3.8 to 3.2 billion years ago.

Fabbroni (crater)

Fabbroni is a small lunar impact crater that lies along the northern edge of the Mare Tranquillitatis, at the eastern edge of the gap where the lunar mare joins Mare Serenitatis to the north. About 45 km to the southeast is the crater Vitruvius.

Fabbroni is named after the Italian economist, chemist and naturalist Giovanni Fabbroni. Fabbroni was known as Vitruvius E before being given its own name by the IAU.

This is a circular crater with a conical interior formed by the inner walls gradually sloping down to the tiny floor at the midpoint. The northern rim of this crater lies along the southeastern flanks of the peak Mons Argaeus.

Franck (crater)

Franck is a small lunar impact crater that lies near the north end of Sinus Amoris, a bay on the northern part of Mare Tranquillitatis. The crater lies just about 20 km southeast of Brewster, and farther to the south of Römer. Franck was previously designated Römer K before being given a unique name by the IAU.

The diameter is 12 km and being about 2,500 meters deep. Also, the area is about 100 km² and its perimeter is over 35 km.

This is a circular, bowl-shaped crater with a sharp rim that has not been significantly eroded. The interior walls slope down to the tiny floor at the midpoint. Just to the north of Franck is a joined pair of smaller craters, and the three nearly form a merged cluster of impacts.

Franz (crater)


Franz is a small lunar impact crater identified during the Apollo mission in August 1971 and located along the eastern edge of the Sinus Amoris, a bay that forms a northern extension to the Mare Tranquillitatis. It lies about 170 km southwest of the prominent crater Macrobius. To the north is the smaller Carmichael, and to the northwest is the diminutive Theophrastus.

Its diameter is 25 km long and is 600 meters deep. The area is around 450 km² and the perimeter is about 75 km.

The rim of this crater has been eroded due to subsequent impacts, although it retains a generally circular form. The interior has been flooded, leaving only a narrow inner wall and a low surviving rim. This floor has the same albedo as the surrounding terrain, and is not as dark as the lunar mare surface to the north and west. Attached to the exterior of the eastern rim is Proclus E, a merged double-crater formation. Proclus lies to the east across the Palus Somni, or Marsh of Sleep.

Sinus Amoris

Sinus Amoris (Latin for "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 crater Theophrastus. Along the western side is the flooded crater Maraldi and Mons Maraldi. Bordering the east side of the bay are the craters Carmichael and Hill. There are some low ridges in the central part of the bay, but otherwise it is relatively featureless.

At the southern egress where the bay joins the mare lies Mons Esam, a minor rise that lies among several small lunar domes.

Sinus Medii

Sinus Medii ("Central Bay") is a small lunar mare. It takes its name from its location at the intersection of the Moon's equator and prime meridian; as seen from the Earth, this feature is located in the central part of the Moon's near side, and it is the point closest to the Earth. From this spot the Earth would always appear directly overhead, although the planet's position would vary slightly due to libration.

During the Apollo program, Sinus Medii was desingated ALS3. Flight operations planners were concerned about having the optimum lighting conditions at the landing site, hence alternative landing sites moved progressively westward, following the terminator. A delay of two days for weather or equipment reasons would have sent Apollo 11 to Sinus Medii instead of ALS2, Mare Tranquillitatis; another two-day delay would have resulted in ALS5, a site in Oceanus Procellarum, being targeted.

Surveyor 5

Surveyor 5 was the fifth lunar lander of the American unmanned Surveyor program sent to explore the surface of the Moon. Surveyor 5 landed on Mare Tranquillitatis. A total of 19,049 images were transmitted to Earth.

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