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Janssen
	Lunar Reconnaissance Orbiter image
Coordinates	44°58′S 40°49′E / 44.96°S 40.82°E
Diameter	201 km
Depth	2.9 km
Colongitude	320° at sunrise
Eponym	Pierre J. C. Janssen

Janssen at center, near the terminator as viewed from Earth

Janssen is an ancient impact crater located in the highland region near the southeastern lunar limb. The entire structure has been heavily worn and is marked by many lesser crater impacts. The outer wall is breached in multiple locations, but the outline of the crater rim can still be observed. The wall forms a distinctive hexagonal shape upon the rugged lunar surface, with a slight curvature at the vertices.

The crater is named after French astronomer Pierre Jules César Janssen.^[1]

The prominent crater Fabricius lies entirely within the outer wall, in the northeast quadrant of the floor. A number of other lesser, but still notable craters mark the crater floor. Connected to the northeast rim is Metius, and to the north is the heavily worn Brenner. Southeast of Janssen are the co-joined craters Steinheil and Watt. Astride the southwest wall is the smaller Lockyer. Further to the east, although appearing nearby due to elongation, is the huge Vallis Rheita.

In the southern two-thirds of Janssen can be discerned the remains of a large, concentric crater, the wall of which is overlaid by Fabricius. The floor of this inner depression contains a rille system named the Rimae Janssen. The rille curves from the rim of Fabricius to the southeast of the outer wall of Janssen, extending for a distance of up to 140 kilometers.

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 Janssen.

Janssen	Coordinates	Diameter, km
B	43°10′S 34°22′E / 43.17°S 34.37°E / -43.17; 34.37 (Janssen B)	21
C	42°53′S 34°55′E / 42.89°S 34.91°E / -42.89; 34.91 (Janssen C)	7
D	48°39′S 41°13′E / 48.65°S 41.22°E / -48.65; 41.22 (Janssen D)	29
E	48°49′S 39°46′E / 48.82°S 39.77°E / -48.82; 39.77 (Janssen E)	24
F	49°49′S 41°55′E / 49.82°S 41.92°E / -49.82; 41.92 (Janssen F)	35
H	46°26′S 41°43′E / 46.43°S 41.71°E / -46.43; 41.71 (Janssen H)	10
J	43°26′S 36°35′E / 43.44°S 36.58°E / -43.44; 36.58 (Janssen J)	27
K	46°11′S 42°19′E / 46.19°S 42.31°E / -46.19; 42.31 (Janssen K)	15
L	46°05′S 43°35′E / 46.09°S 43.58°E / -46.09; 43.58 (Janssen L)	12
M	41°54′S 35°26′E / 41.90°S 35.44°E / -41.90; 35.44 (Janssen M)	16
N	41°26′S 32°07′E / 41.43°S 32.12°E / -41.43; 32.12 (Janssen N)	5
P	45°30′S 39°46′E / 45.50°S 39.76°E / -45.50; 39.76 (Janssen P)	4
Q	46°21′S 39°22′E / 46.35°S 39.36°E / -46.35; 39.36 (Janssen Q)	5
R	48°17′S 38°42′E / 48.28°S 38.70°E / -48.28; 38.70 (Janssen R)	23
S	50°25′S 41°50′E / 50.42°S 41.83°E / -50.42; 41.83 (Janssen S)	7
T	48°53′S 42°19′E / 48.88°S 42.31°E / -48.88; 42.31 (Janssen T)	29
X	42°56′S 33°16′E / 42.93°S 33.27°E / -42.93; 33.27 (Janssen X)	24

References

^ "Janssen (lunar crater)". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.

Andersson, L. E.; Whitaker, E. A. (1982). NASA Catalogue of Lunar Nomenclature (PDF). NASA RP-1097. Archived from the original on 2014-10-06.{{cite book}}: CS1 maint: bot: original URL status unknown (link)
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. S2CID 122125855.
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. (2003). Mapping and Naming the Moon. Cambridge University Press. ISBN 978-0-521-54414-6.
Wlasuk, Peter T. (2000). Observing the Moon. Springer Science & Business Media. ISBN 978-1-852-33193-1.

External links

Wood, Chuck (October 1, 2007). "Crateric Concatenation". Lunar Photo of the Day. Archived from the original on October 27, 2007. Retrieved 2007-10-01.

[1] "Janssen (lunar crater)". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.

[1]

Janssen (lunar crater)

Satellite craters

References

External links