Keeler is a large

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 ...

that lies on 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 ...

far side ''The Far Side'' is a single-panel comic created by Gary Larson and syndicated by Chronicle Features and then Universal Press Syndicate, which ran from December 31, 1979, to January 1, 1995 (when Larson retired as a cartoonist). Its surrealis ...

. It is connected along the eastern edge to

Heaviside Oliver Heaviside FRS (; 18 May 1850 – 3 February 1925) was an English self-taught mathematician and physicist who invented a new technique for solving differential equations (equivalent to the Laplace transform), independently developed vec ...

, a walled plain of similar dimensions. Keeler, however, is the younger of the two formations, with more clearly delineated features. To the northeast of Keeler is the smaller crater Stratton, and to the northwest lies Ventris. The outer rim of Keeler is roughly circular, with a straight segment where it is joined to Heaviside. The northern portion of the rim is more irregular, with an outward protuberance to the north-northwest. Portions of the inner wall have a

terrace Terrace may refer to: Landforms and construction * Fluvial terrace, a natural, flat surface that borders and lies above the floodplain of a stream or river * Terrace, a street suffix * Terrace, the portion of a lot between the public sidewalk a ...

structure, especially along the southern half. Note the

terraced walls A terraced wall, also a terrace wall, or a terraced retaining wall is a wall that is divided into sections (Terrace (earthworks), terraces) over a slope. Such designs are useful when building on a steep Grade (slope), grade. Terraced walls may b ...

of the crater. Within the crater interior, Planté lies on the eastern floor, adjacent to the inner wall. There is an interior ridge that runs from about the midpoint toward the west-southwest. The floor is generally level, with some areas of irregularity to the south. A few small craters mark the interior plain. Measurements with the electron reflectometer instrument on board the

Lunar Prospector ''Lunar Prospector'' was the third mission selected by NASA for full development and construction as part of the Discovery Program. At a cost of $62.8 million, the 19-month mission was designed for a low polar orbit investigation of the Moon, ...

showed that this crater is one of a number of impact sites that show demagnetization. The low magnetic reading lies at the center of this crater, and the reduced field extends outward to about one and a half crater diameters. Scientists believe that shock demagnetization is the cause. Keeler is one of the largest craters of Lower (Early)

Imbrian The Imbrian is a lunar geologic period divided into two epochs, the Early and Late. Early Imbrian In the lunar geologic timescale, the Early Imbrian epoch occurred from 3,850 million years ago to about 3,800 million years ago. It overlaps the en ...

age. The crater was named after American astronomer

James Edward Keeler James Edward Keeler (September 10, 1857 – August 12, 1900) was an American astronomer. He was an early observer of galaxies using photography, as well as the first to show observationally that the rings of Saturn do not rotate as a solid body ...

by the

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

in 1970. Keeler was known as ''Crater 302'' prior to naming.Lunar Landmark Locations - Apollo 8, 10, 11, and 12 Missions. NASA technical note D-6082. Manned Spacecraft Center, Houston, Texas. November 1970. Figure 4. A highly eroded crater that is west of Keeler and somewhat larger than it was designated ''Crater 300'', but it is currently unnamed.

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 Keeler. Keeler S crater as08-17-2709hr.jpg, Keeler S crater photographed by

Apollo 8 Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing, and then departed safely back to Earth. These ...

References

Other sources

* * * * * * * * * * * * {{refend Impact craters on the Moon