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 depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

located near the southwestern edge of

Mare Tranquillitatis 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 huma ...

. 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, as they established it as an independent scientific discipline. From 1825 until ...

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

Sabine The Sabines (, , , ; ) were an Italic people who lived in the central Apennine Mountains (see Sabina) of the ancient Italian Peninsula, also inhabiting Latium north of the Anio before the founding of Rome. The Sabines divided int ...

to the southeast. To the northwest is the crater

Dionysius The name Dionysius (; ''Dionysios'', "of Dionysus"; ) 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 of the Greek god, Dionysus, parallel ...

, and to the north-northeast are

Manners Etiquette ( /ˈɛtikɛt, -kɪt/) can be defined as a set of norms of personal behavior in polite society, usually occurring in the form of an ethical code of the expected and accepted social behaviors that accord with the conventions and n ...

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 w ...

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 and ...

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 volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

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 (; ) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic rock, pyroclastic materials (tephra) that came out of a explosive eruption, volcanic explosion and magma eruption v ...

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 depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German language, German, meaning 'ditch' or 't ...

, the Hypatia rilles. Most significant, they lack deep floors recognized since the days of Gilbert 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 Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

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

* * * * * * * * * * *

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