Cyrillus (crater)

Cyrillus
Lunar Orbiter 4 image
Coordinates13°12′S 24°00′E / 13.2°S 24.0°E / -13.2; 24.0
Diameter98.09 km (60.95 mi)[1]
Depth3.6 km (2.2 mi)
Colongitude335° at sunrise
FormationNectarian[2]
EponymSaint Cyril

Cyrillus is a lunar impact crater located on the northwest edge of Mare Nectaris. Intruding into the northeast rim is the slightly larger, and younger crater Theophilus. To the south is another prominent crater named Catharina. Together these three craters form a prominent trio in the southeast quadrant of the Moon.[3] To the northwest are the Ibn-Rushd and Kant craters.[4]: 78 

This formation is named after Saint Cyril of Alexandria, a 5th-century Patriarch and theologian.[1] His name was included as 'S. Cyrillus Alex.' in the lunar nomenclature of Italian astronomer Giovanni B. Riccioli in 1651.[5] Its modern designation was formally adopted by the International Astronomical Union in 1935.[1]

Description

This formation dates to the Nectarian epoch of the lunar geologic timescale.[2] The floor of Cyrillus contains a reduced central hill and the considerable crater Cyrillus A. The walls of the broken formation of Cyrillus remain intact until the point of junction with Theophilus.[6] The central peak of Cyrillus and ejecta to the southwest are olivine-rich.[7] Slightly northeast of its center, three rounded mountains rise to heights of 1,000 metres above Cyrillus' floor: Cyrillus Alpha, Delta, and Eta.[8]

A tiny crater with bright rays on the east side of Cyrillus has been named Shioli.[9] A point to the east of Shioli was the proposed landing site of Japan's SLIM lander.[10][11][12] It landed on the Moon on January 19, 2024, within 100m of the targeted landing zone.[7]

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 Cyrillus.[13]

Cyrillus[4]: 296  Latitude Longitude Diameter
A 13.8° S 23.1° E 17 km
C 12.3° S 21.5° E 12 km
E 15.8° S 25.3° E 11 km
F 15.3° S 25.5° E 44 km
G 15.6° S 26.6° E 8 km

The following craters have been renamed by the IAU.

References

  1. 1 2 3 "Cyrillus". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program. Retrieved 2026-07-19.
  2. 1 2 Tompkins, Stefanie; Pieters, Carle M. (January 1999). "Mineralogy of the lunar crust: Results from Clementine". Meteoritics & Planetary Science. 34 (1): 25–41. Bibcode:1999M&PS...34...25T. doi:10.1111/j.1945-5100.1999.tb01729.x.
  3. ↑ Grego, Peter (2005). The Moon and How to Observe It. Astronomers' Observing Guides Series. London: Springer-Verlag. p. 205. ISBN 1-85233-748-6.
  4. 1 2 Bussey, B.; Spudis, P. (2004). The Clementine Atlas of the Moon. New York: Cambridge University Press. ISBN 978-0-521-81528-4.
  5. ↑ Whitaker, Ewen A. (1999). Mapping and Naming the Moon. Cambridge University Press. p. 60, 211. ISBN 978-0-521-62248-6.
  6. ↑ Moore, Patrick (2001). On the Moon. Sterling Publishing Co. pp. 81, 209. ISBN 978-0-304-35469-6.
  7. 1 2 Wang, Yichen; et al. (April 2024). "Geological Context of the SLIM Landing Site". Journal of Earth Science. 35 (2): 708–711. Bibcode:2024JEaSc..35..708W. doi:10.1007/s12583-024-1986-8.
  8. ↑ Grego, Peter (2005). Moon Observer's Guide. Springer. p. 207. ISBN 1-85233-748-6.
  9. ↑ "Shioli". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program. Retrieved 2026-07-19.
  10. ↑ Mehta, Jatan (September 11, 2023). "Moon Monday #144: On the most precise planetary landing attempt by SLIM, sprawling SLS rocket costs, and more". Jatan’s Space. Archived from the original on 2024-02-10. Retrieved 2023-09-11.
  11. ↑ "SLIM" (in Japanese). JAXA. Retrieved 2026-07-19.
  12. ↑ Robinson, Mark (November 7, 2023). "On the Way to Shioli Crater". LROC image team. Retrieved 2026-07-19.
  13. ↑ 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.
  14. ↑ Moore, Patrick; Rees, Robin (2014). Patrick Moore's Data Book of Astronomy (2 ed.). Cambridge University Press. p. 64. ISBN 978-1-139-49522-6.
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