Ritter is a

lunar Lunar most commonly means "of or relating to the Moon". Lunar may also refer to: Arts and entertainment * ''Lunar'' (series), a series of video games * "Lunar" (song), by David Guetta * "Lunar", a song by Priestess from the 2009 album ''Prior t ...

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

located near the southwestern edge of

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 ...

. Its diameter is 29.5 km. It was named after German geographer

Carl Ritter Carl Ritter (August 7, 1779September 28, 1859) was a German geographer. Along with Alexander von Humboldt, he is considered one of the founders of modern geography. From 1825 until his death, he occupied the first chair in geography at the Univer ...

and German astrophysicist August Ritter. It is the northwestern member of a crater pair with

Sabine The Sabines (; lat, Sabini; it, Sabini, all exonyms) were an Italic people who lived in the central Apennine Mountains of the ancient Italian Peninsula, also inhabiting Latium north of the Anio before the founding of Rome. The Sabines divide ...

to the southeast. To the northwest is the crater

Dionysius The name Dionysius (; el, Διονύσιος ''Dionysios'', "of Dionysus"; la, Dionysius) was common in classical and post-classical times. Etymologically it is a nominalized adjective formed with a -ios suffix from the stem Dionys- of the name ...

, and to the north-northeast are

Manners Etiquette () is the set of norms of personal behaviour in polite society, usually occurring in the form of an ethical code of the expected and accepted social behaviours that accord with the conventions and norms observed and practised by a ...

and Arago. This crater is roughly circular but with an irregular outer rim. The inner walls have slumped down towards the floor. The interior is irregular with several low ridges. To the northwest of Ritter is a system of parallel

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 ...

s designated Rimae Ritter. These follow a course to the northwest.

Ranger 8 Ranger 8 was a lunar probe in the Ranger program, a robotic spacecraft series launched by NASA in the early-to-mid-1960s to obtain the first close-up images of the Moon's surface. These pictures helped select landing sites for Apollo missions an ...

flew over Ritter prior to impact in Mare Tranquilitatis. Both Sabine and Ritter were originally believed to be

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

s rather than impact craters. In ''To A Rocky Moon'', lunar geologist Don E. Wilhelms summarized: "They are identical twins in morphology and size (29-30 km). They lack radial rim

ejecta Ejecta (from the Latin: "things thrown out", singular ejectum) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic materials (tephra) that came out of a volcanic explosion and magma ...

and

secondary craters Secondary craters are impact craters formed by the ejecta that was thrown out of a larger crater. They sometimes form radial crater chains. In addition, secondary craters are often seen as clusters or rays surrounding primary craters. The study of ...

despite their apparent youth. They are positioned at the presumably active edge of a mare. They are even aligned along

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

, the Hypatia rilles. Most significant, they lack deep floors recognized since the days of

Gilbert Gilbert may refer to: People and fictional characters * Gilbert (given name), including a list of people and fictional characters *Gilbert (surname), including a list of people Places Australia * Gilbert River (Queensland) * Gilbert River (South ...

as diagnostic of impacts." However, after the Apollo landings were complete, it was realized that "all craters inside basins suffer enhanced isostatic uplift," because "the thin crust and greater heat inside basins lower the

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

of the craters' substrate, allowing it to reach isostasy with its surroundings more quickly than can other craters."To a Rocky Moon: A Geologist's History of Lunar Exploration. Don E. Wilhelms, University of Arizona Press (1993). Sabine crater Ritter crater AS16-M-1392

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Ritter.

References

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External links

Ranger 8 image of Ritter
* {{cite web, last = Wood , first = Chuck , date = December 12, 2006 , url = http://www.lpod.org/?m=20061211 , title = How Deep is That Hole , publisher = Lunar Photo of the Day, url-status=dead, archive-url=https://web.archive.org/web/20110614233616/http://www.lpod.org/?m=20061211, archive-date=June 14, 2011 - includes a couple of craters such as Ritter Impact craters on the Moon