Geminus (crater)

Geminus
	LRO mosaic
Coordinates	34°30′N56°42′E / 34.5°N 56.7°E Coordinates: 34°30′N56°42′E / 34.5°N 56.7°E
Diameter	86 km
Depth	5.4 km
Colongitude	304° at sunrise
Eponym	Geminus

Last updated August 07, 2019

Geminus is a lunar impact crater that is located near the northeast limb of the visible Moon. In this position the crater appears oval in shape due to foreshortening, but it is actually more nearly circular in form. Notable nearby craters include Messala to the northeast, Bernoulli due east, and Burckhardt and Cleomedes to the south.

Lunar craters are impact craters on Earth's Moon. The Moon's surface has many craters, almost all of which were formed by impacts.

An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters range from small, simple, bowl-shaped depressions to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.

Earth's Moon is an astronomical body that orbits the planet and acts as its only permanent natural satellite. It is the fifth-largest satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits. The Moon is, after Jupiter's satellite Io, the second-densest satellite in the Solar System among those whose densities are known.

The circular rim of Geminus contain a number of outward notches, particularly to the north and east. The crater ejecta is still visible in the rough surroundings beyond the rim, but any rays deposited during the impact have long since been worn away by space weathering. The inner wall is wide and extensively terraced, although these features are now somewhat muted due to impact erosion. There are no notable impacts on the interior floor, but there is a long, slender central ridge located at the midpoint and a pair of readily observed clefts.

A ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking somewhat like many thin spokes coming from the hub of a wheel. The rays may extend for lengths up to several times the diameter of their originating crater, and are often accompanied by small secondary craters formed by larger chunks of ejecta. Ray systems have been identified on the Moon, Earth, Mercury, and some moons of the outer planets. Originally it was thought that they existed only on planets or moons lacking an atmosphere, but more recently they have been identified on Mars in infrared images taken from orbit by 2001 Mars Odyssey's thermal imager.

Space weathering is the type of weathering that occurs to any object exposed to the harsh environment of outer space. Bodies without atmospheres take on many weathering processes:

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 Geminus.

Geminus	Latitude	Longitude	Diameter
A	31.5° N	51.8° E	15 km
B	34.2° N	52.3° E	10 km
C	33.9° N	58.7° E	16 km
D	30.6° N	47.4° E	16 km
E	33.5° N	48.5° E	67 km
F	32.1° N	51.1° E	22 km
G	30.8° N	48.6° E	14 km
H	31.6° N	48.9° E	15 km
M	31.9° N	48.5° E	11 km
N	31.4° N	47.7° E	24 km
W	34.3° N	47.4° E	6 km
Z	30.7° N	46.7° E	26 km

Related Research Articles

Anaximenes is a low-rimmed lunar impact crater near the north-northwest limb of the Moon. It lies to the west of the crater Philolaus, and northeast of Carpenter. To the northwest is Poncelet, close to the visible edge of the Moon.

Flamsteed is a small lunar impact crater located on the Oceanus Procellarum, which is named after British astronomer John Flamsteed. It lies almost due east of the dark-hued Grimaldi, and north-northwest of the flooded Letronne bay on the south edge of the mare.

Burckhardt is a lunar impact crater that is located in the northeast part of the Moon. It lies between the craters Geminus just to the north and Cleomedes to the south.

Franklin is a lunar impact crater that is located in the northeast part of the visible Moon; it is named after Benjamin Franklin. To the north-northwest is the smaller crater Cepheus, and in the opposite direction to the southwest is the shallow Berzelius.

Archytas is a lunar impact crater that protrudes into the northern edge of Mare Frigoris. To the northwest is the comparably sized crater Timaeus, and the smaller Protagoras lies in the opposite direction to the southeast. Further to the southwest, beyond the opposite edge of the mare, is the dark-floored crater Plato.

Boss is a lunar impact crater that is located along the northeast rim of the Moon's near side. Due to its location, the crater is viewed from the side by observers on the Earth, and its visibility is subject to libration effects.

Boyle is a lunar impact crater that is located in the southern hemisphere on the rugged far side of the Moon. It is adjacent to the larger crater Hess to the southeast, and lies about midway between the craters Alder to the north-northeast and Abbe to the south-southwest.

Dawson is a lunar impact crater that lies on the southern hemisphere on the far side of the Moon. It lies across a crater triplet: the southeast rim is intruding into the crater Alekhin; the northwest rim also intrudes into the larger satellite crater Dawson V, and the northeast rim is attached to the comparably sized Dawson D. To the south of this formation is the large crater Zeeman. West of Dawson is the crater Crommelin, and to the north lies Fizeau.

Bernoulli is a lunar impact crater that is located in the northeast part of the Moon. It lies to the south of the crater Messala, and east of Geminus.

Cepheus is a lunar impact crater that is located in the northeastern part of the Moon, within one crater diameter of the larger crater Franklin to the southeast. To the north-north-east is the flooded crater Oersted. The proximity of this formation to the lunar limb means it appears oblong when viewed from the Earth due to foreshortening.

Brisbane is a lunar impact crater that is located in the southeastern part of the Moon, to the south of the crater Peirescius. To the northwest lie the craters Vega and Reimarus, and farther to the east is the walled plain Lyot. Due to its proximity to the limb, foreshortening of this crater causes it to appear somewhat elliptical in shape, even though it is actually circular.

Berzelius is a lunar impact crater located in the northeast part of the Moon's near side. It lies to the southeast of the crater Franklin, and to the northwest of Geminus.

Buffon is a lunar impact crater that is located on the southern hemisphere on the far side of the Moon. It lies a crater diameter south of the large walled plain Chebyshev. To the northeast is the crater Langmuir and to the southwest is Leavitt. Buffon lies nearly at the midpoint between these formations.

Damoiseau is a lunar impact crater that is located just to the west of the Oceanus Procellarum, in the western part of the Moon's near side. It lies due east of the prominent crater Grimaldi, a walled plain with a distinctive dark floor. Due south of Damoiseau is the crater Sirsalis.

Demonax is a lunar impact crater near the southern limb of the Moon. This location makes the crater difficult to observe due to foreshortening. The crater is also illuminated at a very low angle, when it is in the sunlit side. Demonax lies just to the north of the crater Scott, one of the south polar formations. To the north-northwest is Boguslawsky.

Carver is a lunar impact crater that is located on the far side of the Moon, due east of the walled plain Van der Waals. To the northeast is the crater Rosseland, and to the south-southeast lies Kozyrev.

Fourier is a lunar impact crater that is located in the southwestern part of the Moon's near side, just to the southeast of the crater Vieta. To the northeast is the Mare Humorum. The rim of this crater is roughly circular, but appears oval when viewed from the Earth due to foreshortening.

Denning is a lunar impact crater that is located on the far side of the Moon. It lies about midway between the craters Levi-Civita to the south and Marconi to the north-northeast. About two crater diameters to the southeast is the huge walled plain Gagarin.

Eötvös is the remains of a lunar impact crater on the far side of the Moon. It lies to the north-northwest of the walled plain Roche, and east-southeast of the equally ruined Bolyai.

Tsander is a large lunar impact crater on the far side of the Moon. Attached to the southeastern outer rim is the younger crater Kibal'chich. To the northwest lies Dirichlet, and to the northeast lies Artem'ev.

References

Andersson, L. E.; Whitaker, E. A. (1982). NASA Catalogue of Lunar Nomenclature. NASA RP-1097.
Blue, Jennifer (July 25, 2007). "Gazetteer of Planetary Nomenclature". USGS . Retrieved 2007-08-05.
Bussey, B.; Spudis, P. (2004). The Clementine Atlas of the Moon. New York: Cambridge University Press. ISBN 978-0-521-81528-4.
Cocks, Elijah E.; Cocks, Josiah C. (1995). Who's Who on the Moon: A Biographical Dictionary of Lunar Nomenclature. Tudor Publishers. ISBN 978-0-936389-27-1.
McDowell, Jonathan (July 15, 2007). "Lunar Nomenclature". Jonathan's Space Report . Retrieved 2007-10-24.
Menzel, D. H.; Minnaert, M.; Levin, B.; Dollfus, A.; Bell, B. (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.
Moore, Patrick (2001). On the Moon. Sterling Publishing Co. ISBN 978-0-304-35469-6.
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.
Webb, Rev. T. W. (1962). Celestial Objects for Common Telescopes (6th revised ed.). Dover. ISBN 978-0-486-20917-3.
Whitaker, Ewen A. (1999). Mapping and Naming the Moon. Cambridge University Press. ISBN 978-0-521-62248-6.
Wlasuk, Peter T. (2000). Observing the Moon. Springer. ISBN 978-1-85233-193-1.

Ewen Adair Whitaker was a British-born astronomer who specialized in lunar studies. During World War II he was engaged in quality control for the lead sheathing of hollow cables strung under the English Channel as part of the "Pipe Line Under The Ocean" Project (PLUTO) to supply gasoline to Allied military vehicles in France. After the war, he obtained a position at the Royal Greenwich Observatory working on the UV spectra of stars, but became interested in lunar studies. As a sideline, Whitaker drew and published the first accurate chart of the South Polar area of the Moon in 1954, and served as director of the Lunar Section of the British Astronomical Association.

The National Aeronautics and Space Administration is an independent agency of the United States Federal Government responsible for the civilian space program, as well as aeronautics and aerospace research.

The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology, geography, geology, and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility.

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LRO mosaic
Coordinates	34°30′N56°42′E / 34.5°N 56.7°E / 34.5; 56.7 Coordinates: 34°30′N56°42′E / 34.5°N 56.7°E / 34.5; 56.7
Diameter	86 km
Depth	5.4 km
Colongitude	304° at sunrise
Eponym	Geminus