Alter (crater)

Alter
Oblique Lunar Orbiter 5 image, facing west
Coordinates18°44′N 107°48′W / 18.74°N 107.80°W / 18.74; -107.80
Diameter64.73 km (40.22 mi)[1]
DepthUnknown
Colongitude108° at sunrise
EponymDinsmore Alter
Satellite craters of Alter

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.

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.

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.[7]

Alter[3]: 291  Latitude Longitude Diameter
K 16.3° N 106.0° W 22 km
W 20.4° N 109.2° W 52 km

References

  1. 1 2 "Alter". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  2. ↑ Moore, Patrick (2000). The Data Book of Astronomy. CRC Press. p. 66. ISBN 978-1-4200-3344-1.
  3. 1 2 Bussey, B.; Spudis, P. (2004). The Clementine Atlas of the Moon. New York: Cambridge University Press. ISBN 978-0-521-81528-4.
  4. ↑ Donaldson Hanna, K. L.; et al. (July 2014). "Global assessment of pure crystalline plagioclase across the Moon and implications for the evolution of the primary crust". Journal of Geophysical Research: Planets. 119 (7): 1516–1545. Bibcode:2014JGRE..119.1516D. doi:10.1002/2013JE004476.
  5. ↑ Menzel, D. H.; et al. (1971). "Report on Lunar Nomenclature by the Working Group of Commission 17 of the IAU". Space Science Reviews. 12 (2): 136–186. Bibcode:1971SSRv...12..136M. doi:10.1007/BF00171763. S2CID 122125855.
  6. ↑ "Lunar Farside Chart (LFC-1A)" (2nd ed.). Lunar & Planetary Institute. October 1967. Retrieved 2026-05-12.
  7. ↑ Grego, P. (2015). "Satellite Crater". In Hargitai, H.; Kereszturi, Á. (eds.). Encyclopedia of Planetary Landforms. New York, NY: Springer. doi:10.1007/978-1-4614-3134-3_328.

Sources

  • Price, Fred W. (1988). The Moon Observer's Handbook. Cambridge University Press. ISBN 978-0-521-33500-3.
  • Rükl, Antonín (1990). Atlas of the Moon. Kalmbach Books. ISBN 978-0-913135-17-4.
  • Wlasuk, Peter T. (2000). Observing the Moon. Springer. ISBN 978-1-85233-193-1.
  • Wikimedia Commons logo Media related to Alter (lunar crater) at Wikimedia Commons
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