Alter (crater)
Crater on the Moon
From Wikipedia, the free encyclopedia
Alter is a lunar impact crater that is located in the northern hemisphere on the far side of the Moon.[2] It lies to the southwest of the larger crater Robertson, and to the east of Ohm.
Oblique Lunar Orbiter 5 image, facing west | |
| Coordinates | 18.74°N 107.80°W |
|---|---|
| Diameter | 64.73 km (40.22 mi)[1] |
| Depth | Unknown |
| Colongitude | 108° at sunrise |
| Eponym | Dinsmore Alter |
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.[3]: 54 The infrared spectrum of pure crystalline plagioclase has been identified on the central peak.[4]
This crater is named after American astronomer and meteorologist Dinsmore Alter (1888-1968), an authority on lunar geology.[5] Prior to formal naming by the IAU in 1970,[1] Alter was called Crater 257.[6] 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.
