Eratosthenes (crater)

Eratosthenes

Lunar Orbiter 4 image
Diameter	58 km
Depth	3.6 km
Colongitude	12° at sunrise
Eponym	Eratosthenes

Eratosthenes (lower right of center) and surroundings from Apollo 17. NASA image.

Eratosthenes crater. Photo taken from Earth. Author: Georgi Georgiev, Stara Zagora, Bulgaria.

Eratosthenes as seen from Earth.

Detail map of Mare Imbrium's features. Eratosthenes is marked "L".

Eratosthenes is a relatively deep lunar impact crater that lies on the boundary between the Mare Imbrium and Sinus Aestuum mare regions. It forms the western terminus of the Montes Apenninus mountain range. The crater has a well-defined circular rim, terraced inner wall, central mountain peaks, an irregular floor, and an outer rampart of ejecta. It lacks a ray system of its own, but is overlain by rays from the prominent crater Copernicus to the south-west.

The Eratosthenian period in the lunar geological timescale is named after this crater. The crater is believed to have been formed about 3.2 billion years ago, defining the start of this time period.

At low Sun-angles this crater is prominent due to the shadow cast by the rim. When the Sun is directly overhead, however, Eratosthenes visually blends into the surroundings, and it becomes more difficult for an observer to locate it. The rays from Copernicus lie across this area, and their higher albedo serves as a form of camouflage.

In 1851 Shropshire Astronomer Henry Blunt constructed a model of the moon's surface showing Eratosthenes. The model is based on observations made by Blunt with a reflecting telescope from his home in Shrewsbury and was displayed in the same year at the Great Exhibition, London.

In 1924, William H. Pickering noted dark patches in the crater that varied in a regular manner over each lunar day. He put forward the speculative idea that these patches appeared to migrate across the surface, suggestive of herds of small life forms. The idea received a degree of attention primarily due to Pickering's reputation.

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 Eratosthenes.

Eratosthenes	Latitude	Longitude	Diameter
A	18.4° N	8.3° W	6 km
B	18.7° N	8.7° W	5 km
C	16.9° N	12.4° W	5 km
D	17.5° N	10.9° W	4 km
E	18.0° N	10.9° W	4 km
F	17.7° N	9.9° W	4 km
H	13.3° N	12.2° W	3 km
K	12.9° N	9.2° W	5 km
M	14.0° N	13.6° W	4 km
Z	13.8° N	14.1° W	1 km

References

• Andersson, L. E.; Whitaker, E. A. (1982). NASA Catalogue of Lunar Nomenclature. NASA RP-1097. {{cite book}}: Invalid |ref=harv (help)
• Blue, Jennifer (July 25, 2007). "Gazetteer of Planetary Nomenclature". USGS. Retrieved 2007-08-05. {{cite web}}: Invalid |ref=harv (help)
• Bussey, B.; Spudis, P. (2004). The Clementine Atlas of the Moon. New York: Cambridge University Press. ISBN 978-0-521-81528-4. {{cite book}}: Invalid |ref=harv (help)
• 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. {{cite book}}: Invalid |ref=harv (help)
• McDowell, Jonathan (July 15, 2007). "Lunar Nomenclature". Jonathan's Space Report. Retrieved 2007-10-24. {{cite web}}: Invalid |ref=harv (help)
• Moore, Patrick (2001). On the Moon. Sterling Publishing Co. ISBN 978-0-304-35469-6. {{cite book}}: Invalid |ref=harv (help)
• Price, Fred W. (1988). The Moon Observer's Handbook. Cambridge University Press. ISBN 978-0-521-33500-3. {{cite book}}: Invalid |ref=harv (help)
• Rükl, Antonín (1990). Atlas of the Moon. Kalmbach Books. ISBN 978-0-913135-17-4. {{cite book}}: Invalid |ref=harv (help)
• Webb, Rev. T. W. (1962). Celestial Objects for Common Telescopes (6th revision ed.). Dover. ISBN 978-0-486-20917-3. {{cite book}}: Invalid |ref=harv (help)
• Whitaker, Ewen A. (1999). Mapping and Naming the Moon. Cambridge University Press. ISBN 978-0-521-62248-6. {{cite book}}: Invalid |ref=harv (help)
• Wlasuk, Peter T. (2000). Observing the Moon. Springer. ISBN 978-1-85233-193-1. {{cite book}}: Invalid |ref=harv (help)

External links

• PDF newsletter - The Lunar Observer: Feature of the Month - MARCH 2006: FOCUS ON: Eratosthenes