Alphonsus (crater) explained

Coordinates:	-13.39°N -2.85°W
Diameter:	110.54 km
Depth:	2.7 km
Colong:	4
Eponym:	Alfonso X

Alphonsus is an ancient impact crater on the Moon that dates from the pre-Nectarian era.^[1] (Older sources state that it is Nectarian in age.^[2]) It is located on the lunar highlands on the eastern end of Mare Nubium, west of the Imbrian Highlands, and slightly overlaps the crater Ptolemaeus to the north. To the southwest is the smaller Alpetragius. The crater name was approved by the IAU in 1935.^[3]

Description

The surface of Alphonsus is broken and irregular along its boundary with Ptolemaeus. The outer walls are slightly distorted and possess a somewhat hexagonal form.

A low ridge system of deposited ejecta bisects the crater floor, and includes the steep central peak designated Alphonsus Alpha (α). This pyramid-shaped formation rises to a height of 1.5 km above the interior surface. It is not volcanic in origin, but rather is made of anorthosite like the lunar highlands.

The floor is fractured by an elaborate system of rilles and contains four or five smaller craters surrounded by a symmetric darker halo. These dark-halo craters are cinder cone-shaped and are believed by some to be volcanic in origin, although others think they were caused by impacts that excavated darker mare material from underneath the lighter lunar regolith.

Exploration

The Ranger 9 probe impacted in Alphonsus, a short distance to the northeast of the central peak. Harold Urey said of a close-up photograph of Alphonsus:

Apollo Landing Site

The dark-haloed craters along some of the rilles in the crater are thought to be volcanic vents, and during the Apollo program Alphonsus was considered as a possible landing site in order to possibly sample xenoliths of the lunar mantle from the vents.^[4] It was considered for Apollo 16 but the Descartes area was selected. It was one of the three final possible sites for Apollo 17, together with Gassendi crater and the Taurus-Littrow valley, but it was considered possibly "contaminated" with younger material from the nearby Imbrium basin.^[5]

Transient lunar phenomena

Alphonsus is one of the sites noted for transient lunar phenomena, as glowing red-hued clouds have been reported emanating from the crater. On October 26, 1956, the lunar astronomer Dinsmore Alter noted some blurring of the rilles on the floor of Alphonsus in the photographs he took in violet light. The same blurring did not occur in the infrared photographs he took at the same time. However, few professional astronomers found this evidence of volcanic activity on the Moon very convincing.^[6]

One astronomer who was intrigued by Alter's observations was Nikolai A. Kozyrev, from the Soviet Union. In 1958 while Kozyrev was looking for volcanic phenomenon on the moon, he observed the formation of a mist-like cloud within Alphonsus.^[7] The spectrum of the area had been measured at this time, and displayed indications of carbon matter, possibly C₂ gas. He believed this to be the result of volcanic or related activity. However no evidence for this phenomenon has been found from lunar missions, and the emission results have never been confirmed.^[8]

Names

Alphonsus is named after King Alfonso X of Castile (known as "Alfonso the Wise"), who had an interest in astronomy. Like many of the craters on the Moon's near side, it was given its name by Giovanni Riccioli, whose 1651 nomenclature system has become standardized; Riccioli originally named it "Alphonsus Rex" ('King Alfonso'), but the 'Rex' was later dropped.^[9] Earlier lunar cartographers had given the feature different names. Michael van Langren's 1645 map calls it "Ludovici XIV, Reg. Fran.", after Louis XIV of France,^[10] and Johannes Hevelius called it "Mons Masicytus" after a range of mountains in Lycia.^[11]

Interior craters

Five tiny craters in the northeastern part of Alphonsus' interior floor have been assigned names by the IAU. These are listed in the table below.

Crater	Coordinates	Diameter	Name source
Chang-Ngo	-12.7°N -2.1°W	3 km	Chinese goddess of the moon
José	-12.7°N -1.6°W	2 km	Spanish masculine name
Monira	-12.6°N -1.7°W	2 km	Arabic feminine name
Ravi	-12.5°N -1.9°W	2.5 km	Indian masculine name
Soraya	-12.9°N -1.6°W	2 km	Persian feminine name

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 Alphonsus.

Alphonsus	Latitude	Longitude	Diameter
A	14.8° S	2.3° W	4 km
B	13.2° S	0.2° W	24 km
C	14.4° S	4.8° W	4 km
D	15.1° S	0.8° W	23 km
G	12.3° S	3.3° W	4 km
H	15.6° S	0.5° W	8 km
J	15.1° S	2.5° W	8 km
K	12.5° S	0.1° W	20 km
L	12.0° S	3.7° W	4 km
R	14.4° S	1.9° W	3 km
X	15.0° S	4.4° W	5 km
Y	14.7° S	1.8° W	3 km

References

• Book: Andersson . L. E. . Whitaker . E. A. . Ewen Whitaker . 1982 . NASA Catalogue of Lunar Nomenclature . NASA RP-1097 .
• Book: Bussey . B. . Ben Bussey . Spudis . P. . Paul Spudis . 2004 . The Clementine Atlas of the Moon . Cambridge University Press . New York . 978-0-521-81528-4 .
• Book: Cocks . Elijah E. . Cocks . Josiah C. . 1995 . Who's Who on the Moon: A Biographical Dictionary of Lunar Nomenclature . Tudor Publishers . 978-0-936389-27-1 .
• Web site: McDowell . Jonathan . July 15, 2007 . Lunar Nomenclature . Jonathan's Space Report . 2007-10-24 .
• Menzel. D. H.. Minnaert. M.. Levin. B.. Dollfus. A.. Bell. B.. Report on Lunar Nomenclature by the Working Group of Commission 17 of the IAU. 10.1007/BF00171763. Space Science Reviews. 12. 2. 136–186. 1971. 1971SSRv...12..136M. 122125855.
• Book: Moore , Patrick . Patrick Moore . 2001 . On the Moon . Sterling Publishing Co . 978-0-304-35469-6 .
• Book: Price , Fred W. . 1988 . The Moon Observer's Handbook . Cambridge University Press . 978-0-521-33500-3 .
• Book: Rükl , Antonín . Antonín Rükl . 1990 . Atlas of the Moon . Kalmbach Books . 978-0-913135-17-4 .
• Book: Webb , Rev. T. W. . Thomas William Webb . 1962 . Celestial Objects for Common Telescopes . 6th revised . Dover . 978-0-486-20917-3 .
• Book: Whitaker , Ewen A. . Ewen Whitaker . 1999 . Mapping and Naming the Moon . Cambridge University Press . 978-0-521-62248-6 .
• Book: Wlasuk , Peter T. . 2000 . Observing the Moon . Springer . 978-1-85233-193-1 .

Further reading

• Web site: Wood . Chuck . 2005-04-06 . Micro-Topo . Lunar Photo of the Day . 2006-07-21 . dead . https://web.archive.org/web/20060514140245/http://www.lpod.org/?m=20060406 . 2006-05-14 .
• Book: Cortright , Edgar M. . SP-168 Exploring Space with a Camera . NASA Langley Research Center . 1968 . Rangers Bring the Moon Up Close . 48 . https://history.nasa.gov/SP-168/section2a.htm#46 .
• Alter . Dinsmore . A Suspected Partial Obscuration of the Floor of Alphonsus . Publications of the Astronomical Society of the Pacific . 1957 . 69 . 407 . 1957PASP...69..158A . 10.1086/127036 . 158 . free .
• Alter . Dinsmore . The Kozyrev Observations of Alphonsus . Publications of the Astronomical Society of the Pacific . 1959 . 71 . 418 . 1959PASP...71...46A . 10.1086/127330 . 46 .
• Web site: W. David . Compton . 1989 . Where No Man Has Gone Before: A History of Apollo Lunar Exploration Missions . NASA . 2007-02-09 .

External links

• Alphonsus at The Moon Wiki
• Rimae Alphonsus at The Moon Wiki
• Alphonsus crater mantled floor fracture, from LROC
• Lunar Orbiter map and photo of Alphonsus

Other related articles

• Web site: Wood . Chuck . May 15, 2004 . The Golden Triad . Lunar Photo of the Day . September 16, 2017 . https://web.archive.org/web/20180530165228/http://www.lpod.org/archive/archive/2004/05/LPOD-2004-05-15.htm . May 30, 2018 . dead .
• Web site: Wood . Chuck . May 21, 2004 . Volcanic Craters on the Moon . Lunar Photo of the Day . September 16, 2017 . https://web.archive.org/web/20180530202019/http://www.lpod.org/archive/archive/2004/05/LPOD-2004-05-21.htm . May 30, 2018 . dead .
• Web site: Wood . Chuck . October 31, 2004 . Sunrise and Sunset on the Triade . Lunar Photo of the Day . October 14, 2017 . https://web.archive.org/web/20171014150747/http://www.lpod.org/archive/LPOD-2004-10-31.htm . October 14, 2017 . dead . - one of three craters making up a Triad which includes Alphonsus
• Web site: Wood . Chuck . July 10, 2006 . Craters and Papers . Lunar Photo of the Day . dead. https://web.archive.org/web/20110614233616/http://www.lpod.org/?m=20060710. June 14, 2011.
• Web site: Wood . Chuck . September 16, 2006 . Just Another Glorious Image . Lunar Photo of the Day . dead. https://web.archive.org/web/20110614233616/http://www.lpod.org/?m=20060916. June 14, 2011.
• Web site: Wood . Chuck . November 27, 2006 . A Long Line in the Matter of Confidence . Lunar Photo of the Day . dead. https://web.archive.org/web/20110614233616/http://www.lpod.org/?m=20061127. June 14, 2011.
  • Web site: Wood . Chuck . February 13, 2007. New Observations of a Well-Known Area . Lunar Photo of the Day . dead. https://web.archive.org/web/20110614233616/http://www.lpod.org/?m=20070213. June 14, 2011.

Notes and References

1. Web site: Ambrose. W.A.. ORIGIN, DISTRIBUTION, AND CHRONOSTRATIGRAPHY OF ASYMMETRIC SECONDARY CRATERS ASSOCIATED WITH NEARSIDE LUNAR BASINS. Bureau of Economic Geology. University of Texas at Austin, TX. 25 September 2013.
2. https://pubs.er.usgs.gov/publication/pp1348 The geologic history of the Moon
3. http://planetarynames.wr.usgs.gov/Feature/206 Alphonsus
4. To a Rocky Moon: A Geologist's History of Lunar Exploration. Don E. Wilhelms, University of Arizona Press (1993). Chapter 16.
5. To a Rocky Moon: A Geologist's History of Lunar Exploration. Don E. Wilhelms, University of Arizona Press (1993). Chapter 17.
6. Dinsmore (1957), 69: 158
7. Oepik. E.J.. Cratering and the moon's surface. Armagh Observatory. January 1968 . Department of Physics and Astronomy, University of Maryland. 2060/19690007782.
8. Dinsmore (1957), 71: 46
9. Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p.210.
10. Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p. 198.
11. Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p. 205.