Alter is a lunar

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 northern 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 lies to the southwest of the larger crater Robertson, and to the east of

Ohm Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm. Ohm or OHM may also refer to: People * Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm'' * Germán Ohm (born 1936), Mexican boxer * Jörg Ohm (1 ...

. The outer rim of Alter has been degraded by subsequent erosion, most notably at the northern and southern extremes. There is a small crater lying across the south-southeast rim. A cleft runs across the floor from the southern rim toward the north-northeast. Ray material cross the crater floor from the east, forming a pair of faint bands. Prior to formal naming by the IAU in 1970, Alter was called ''Crater 257''.Lunar Farside Chart (LFC-1A)
2nd Edition October 1967 The crater Alter W, to the northwest of Alter, was called ''Crater 255''. A crater that is currently unnamed, between Alter W and Comrie K, was called ''Crater 254''.

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 Alter.

References

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External links

* {{Craters on the Moon: A–B Impact craters on the Moon