Alder 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 ...
that is located in the
southern hemisphere on the
far side of the
Moon
The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
. It is located in the
South Pole-Aitken basin
South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both west and east.
Etymology
The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþaz ...
, and lies to the southeast of the crater
Von Kármán. Southeast of Alder is
Bose, and to the south-southwest lies
Boyle.
The inner wall of Alder is rough and slightly
terraced, with the material scattered across the edges of the otherwise relatively flat interior floor. There are several low central ridges lying along a band from the midpoint toward the eastern rim. A small crater lies on the eastern inner slopes. The crater is otherwise free of significant impacts within the rim.
Alder is associated with the only area in the basin not dominated by the
pyroxene
The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...
rocks typical of lunar lowlands. This ''alder ejecta'' area is on
spectrograph
An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...
ic evidence instead principally
anorthosite
Anorthosite () is a phaneritic, intrusive rock, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic ...
rock, typical of the lunar highlands.
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 Alder.
References
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External links
* (This article on South Pole-Aitken (SPA) basin mentions Alder crater.)
{{Craters on the Moon: A–B
Impact craters on the Moon