Sinus Medii (

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''sinus mediī'' "Middle Bay") is a small

lunar mare The lunar maria (; singular: mare ) are large, dark, basaltic plains on Earth's Moon, formed by ancient asteroid impacts on the far side on the Moon that triggered volcanic activity on the opposite (near) side. They were dubbed , Latin for 'seas' ...

. It takes its name from its location at the intersection of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...

and

prime meridian A prime meridian is an arbitrary meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great c ...

; as seen from the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, 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 designated 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 Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, an ...

to Sinus Medii instead of ALS2,

Mare Tranquillitatis Mare Tranquillitatis (Latin ''tranquillitātis'', the Sea of Tranquillity or Sea of Tranquility; see spelling differences) is a lunar mare that sits within the Tranquillitatis basin on the Moon. It is the first location on another world to be ...

; another two-day delay would have resulted in ALS5, a site in

Oceanus Procellarum Oceanus Procellarum ( la, Ōceanus procellārum, lit=Ocean of Storms) is a vast lunar mare on the western edge of the near side of the Moon. It is the only one of the lunar maria to be called an "Oceanus" (ocean), due to its size: Oceanus Proc ...

, being targeted.

Geology

The selenographic

coordinate In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space. The order of the coordinates is sign ...

s of Sinus Medii are , and its diameter is 287 km. It joins

Mare Insularum Mare Insularum (Latin ''īnsulārum'', the "sea of islands") is a lunar mare located in the Insularum basin just south of the western Mare Imbrium. The basin material is of the Lower Imbrian epoch, with the mare material of the Upper Imbrian epo ...

in the west with

Mare Vaporum Mare Vaporum (Latin ''vapōrum'', the "sea of vapors") is a lunar mare located between the southwest rim of Mare Serenitatis and the southeast rim of Mare Imbrium. It was named by Giovanni Battista Riccioli in 1651.''Autostar Suite Astronomer ...

to the north. The eastern part of this area is notable for a series of

rille Rille (German for 'groove') is typically used to describe any of the long, narrow depressions in the surface of the Moon that resemble channels. The Latin term is ''rima'', plural ''rimae''. Typically, a rille can be several kilometers wid ...

systems. In the far northeast is the Rima Hyginus, which is bisected by the crater

Hyginus Gaius Julius Hyginus (; 64 BC – AD 17) was a Latin author, a pupil of the scholar Alexander Polyhistor, and a freedman of Caesar Augustus. He was elected superintendent of the Palatine library by Augustus according to Suetonius' ''De Grammati ...

. At the far eastern end is the 220-km long Rima Ariadaeus rille which continues eastward to the edge of the

. At longitudes 4-6° E is the Rimae Triesnecker rille system, named after the crater Triesnecker just to the west. The northern edge of the Sinus Medii is formed by a highland region, with the impact craters Murchison and

Pallas Pallas may refer to: Astronomy * 2 Pallas asteroid ** Pallas family, a group of asteroids that includes 2 Pallas * Pallas (crater), a crater on Earth's moon Mythology * Pallas (Giant), a son of Uranus and Gaia, killed and flayed by Athena * Pa ...

along the border. Near the northern border on this mare is the cup-shaped

Chladni Ernst Florens Friedrich Chladni (, , ; 30 November 1756 – 3 April 1827) was a German physicist and musician. His most important work, for which he is sometimes labeled as the father of acoustics, included research on vibrating plates a ...

. Another highland region lies to the south and southeastern edge of the Sinus Medii. Several flooded craters lie along this border, with

Flammarion Flammarion may refer to: * Camille Flammarion (1842–1925), French astronomer and author * Gabrielle Renaudot Flammarion (1877–1962), French astronomer, wife of Camille Flammarion * Flammarion engraving by unknown artist; appeared in a book by C ...

near the western edge, then Oppolzer, Réaumur, and Seeliger further east. The Rima Flammarion and Rima Oppolzer

s lie along the edge of the mare near their corresponding craters. Also along the southeast border and bisecting the prime meridian is the crater Rhaeticus. In the western half of the interior are the small craters

Bruce The English language name Bruce arrived in Scotland with the Normans, from the place name Brix, Manche in Normandy, France, meaning "the willowlands". Initially promulgated via the descendants of king Robert the Bruce (1274−1329), it has been ...

and Blagg. Near the western end of the mare are the flooded craters Schröter and Sömmering.

Names

The English astronomer William Gilbert was the first to give a name to this mare, calling it Insula Medilunaria ("Middlemoon Island"). The idea for its present name originates with Michael Van Langren, who labelled it Sinus Medius in his 1645 map.

Johannes Hevelius Johannes Hevelius Some sources refer to Hevelius as Polish: * * * * * * * Some sources refer to Hevelius as German: * * * * *of the Royal Society * (in German also known as ''Hevel''; pl, Jan Heweliusz; – 28 January 1687) was a councillor ...

called the feature Mare Adriaticum ("The

Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to t ...

") in his 1647 map.
List of names on p. 228

Giovanni Riccioli Giovanni Battista Riccioli, SJ (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 ...

called it Sinus Aestuum ("Bay of Hot Days") in his 1651 map. Map of the Moon by Giovanni Riccioli (1651)

Exploration

The

Surveyor 6 Surveyor 6 was the sixth lunar lander of the American uncrewed Surveyor program that reached the surface of the Moon. Surveyor 6 landed on the Sinus Medii. A total of 30,027 images were transmitted to Earth. This spacecraft was the fourth of the ...

mission landed to the west-southwest of

crater inside Sinus Medii in November 1967. Prior to that in July 1967, the

Surveyor 4 Surveyor 4 was the fourth lunar lander in the American uncrewed Surveyor program sent to explore the surface of the Moon. This spacecraft crashed after an otherwise flawless mission; telemetry contact was lost 2.5 minutes before touchdown. The ...

had crashed nearby.

References

External links

Sinus Medii at The Moon Wiki
{{Authority control Medii, Sinus