View source for Sinus Medii

{{more citations needed|date=June 2012}}
{{Infobox Lunar mare
|name        = Sinus Medii
|image       = Sinus Medii (LRO).png
|caption     = [[Lunar Reconnaissance Orbiter|LRO]] image
|coordinates = {{coord|1.6|N|1.0|E|globe:moon_type:landmark|display=inline,title}}
|diameter    = {{Convert|287|km|abbr=on}}
|eponym      = Bay of the Center
}}

'''Sinus Medii'''<ref name=gpn>{{gpn|5567}}</ref> {{IPAc-en|'|s|aɪ|n|ə|s|_|'|m|iː|d|i|aɪ}} ([[Latin]] ''sinus mediī'' "Middle 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]].
[[File:Aldo Ferruggia - Godin Crater.jpg|left|thumb|421x421px|Sinus Medii and closer craters with mineral postprocessing]]
During the [[Apollo program]], Sinus Medii was designated Apollo Landing Site 3 (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]] (where it actually landed); another two-day delay would have resulted in ALS5, a site in [[Oceanus Procellarum]], being targeted.

==Geology==
[[File:Sinus Medii 2093 med.jpg|thumb|left|Oblique view facing south of central Sinus Medii from [[Lunar Orbiter 2]], showing Bruce crater at right and Oppolzer crater above left]]
[[File:Sinus Medii AS16-M-0842.jpg|thumb|right|Oblique view facing north from [[Apollo 16]]]]

The selenographic [[coordinate]]s of Sinus Medii are {{Lunar coords and quad cat|1.6|N|1.0|E}}, and its diameter is 287&nbsp;km.<ref name=gpn/> It joins [[Mare Insularum]] in the west with [[Mare Vaporum]] to the north.

The eastern part of this area is notable for a series of [[rille]] systems. In the far northeast is the Rima Hyginus, which is bisected by the crater [[Hyginus (crater)|Hyginus]]. At the far eastern end is the 220-km long [[Rima Ariadaeus]] rille which continues eastward to the edge of the [[Mare Tranquillitatis]]. At longitudes 4-6° E is the Rimae Triesnecker rille system, named after the crater [[Triesnecker (crater)|Triesnecker]] just to the west.<ref name=LAC59>[https://asc-planetarynames-data.s3.us-west-2.amazonaws.com/Lunar/lac_59_wac.pdf LAC 59], Lunar Astronautical Chart, Scale 1:1,000,000, Mercator Projection.</ref>

The northern edge of the Sinus Medii is formed by a highland region, with the impact craters [[Murchison (crater)|Murchison]] and [[Pallas (crater)|Pallas]] along the border. Near the northern border on this mare is the cup-shaped [[Chladni (crater)|Chladni]].<ref name=LAC59/>

Another highland region lies to the south and southeastern edge of the Sinus Medii. Several flooded craters lie along this border, with [[Flammarion (lunar crater)|Flammarion]] near the western edge, then [[Oppolzer (crater)|Oppolzer]], [[Réaumur (crater)|Réaumur]], and [[Seeliger (crater)|Seeliger]] further east. The [[Rima Flammarion]] and [[Rima Oppolzer]] [[rille]]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 (crater)|Rhaeticus]].

In the western half of the interior are the small craters [[Bruce (crater)|Bruce]] and [[Blagg (crater)|Blagg]]. Near the western end of the mare are the flooded craters [[Schröter (lunar crater)|Schröter]] and [[Sömmering (crater)|Sömmering]].

==Names==
[[Image:Langrenus map of the Moon 1645.jpg|thumb|right|[[Michael van Langren|Langren's]] map (1645), on which the name ''Sinus Medius'' first appeared]]
The English astronomer [[William Gilbert (astronomer)|William Gilbert]] was the first to give a name to this mare, calling it Insula Medilunaria ("Middlemoon Island").<ref>Ewen A. Whitaker, ''Mapping and Naming the Moon'' (Cambridge University Press, 1999), p.15</ref> The idea for its present name originates with [[Michael van Langren]], who labelled it Sinus Medius in his 1645 map.<ref>Ewen A. Whitaker, ''Mapping and Naming the Moon'' (Cambridge University Press, 1999), p.41, 200.</ref> [[Johannes Hevelius]] called the feature Mare Adriaticum ("The [[Adriatic Sea]]") in his 1647 map.<ref>Ewen A. Whitaker, ''Mapping and Naming the Moon'' (Cambridge University Press, 1999), p.53, 201.</ref><ref name=Hevelius_1647>{{cite book
 |author    =Hevelius J.|author-link    =Johannes Hevelius
 |title     =Selenographia sive Lunae descriptio
 |place     =[[Gdańsk|Gedani]]
 |publisher =Hünefeld
 |date      =1647
 |pages     =226–227, 234
 |doi       =10.3931/e-rara-238
 |url       =http://www.e-rara.ch/zut/content/pageview/160524
}} ([http://www.e-rara.ch/zut/content/pageview/160527 List of names on p. 228])</ref> [[Giovanni Riccioli]] called it Sinus Aestuum ("Bay of Hot Days") in his 1651 map.<ref>Ewen A. Whitaker, ''Mapping and Naming the Moon'' (Cambridge University Press, 1999), p.61, 216, 217.</ref><ref>[[:commons:File:Riccioli1651MoonMap.jpg|Map of the Moon by Giovanni Riccioli (1651)]]</ref>

==Exploration==
[[Image:Surveyor 6 Fig 7-41d2.jpg|thumb|left|Mosaic of the mare surface from Surveyor 6]]
The [[Surveyor 6]] mission landed to the west-southwest of [[Bruce (crater)|Bruce]] crater inside Sinus Medii in November 1967.  Prior to that in July 1967, the [[Surveyor 4]] had crashed nearby.

== References ==
{{reflist|30em}}

==External links==
{{Commonscat}}
*[https://the-moon.us/wiki/Sinus_Medii Sinus Medii at The Moon Wiki]

{{Lunar maria}}
{{Moon colonization}}

{{Authority control}}

[[Category:Maria on the Moon|Medii, Sinus]]