Eratosthenes (crater)

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Eratosthenes (LRO).png
Coordinates 14°28′N 11°19′W / 14.47°N 11.32°W / 14.47; -11.32Coordinates: 14°28′N 11°19′W / 14.47°N 11.32°W / 14.47; -11.32
Diameter 59 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 crater 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.

One other crater to the south-southwest is Stadius located over a crater diameter distant.

The Eratosthenian period in the lunar geological timescale is named after this crater, though it does not define the start of this time period.[1] The crater is believed to have been formed about 3.2 billion years ago.

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 1910–1920th, 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.[2][3] The idea received a degree of attention primarily due to Pickering's reputation.

Eratosthenes and its satellite craters
Detail map of Mare Imbrium's features. Eratosthenes is marked "L".


The crater is named after ancient Greek astronomer Eratosthenes of Cyrene,[4] who estimated the circumference of the Earth, and the distance from the Earth to the Sun. It was given its name by Giovanni Riccioli, whose 1651 nomenclature system has become standardized.[5][6] Earlier lunar cartographers had given the feature different names. Michael van Langren's 1645 map calls it "Haro".[7][8] And Johannes Hevelius called it "Insula Vulcania" of the ancient world, also to the south, he named "Montes Chalcidici" to what are now the eastern part of the Copernicus ray system.[9]

An earlier feature was named Sinus Eratosthenes (Bay of Eratosthenes) in Michael van Langren's 1645 map[8] That part, thought to be a straight, it actually a terrain (or land) separating Mare Fecunditatis and Mare Spumans.

Satellite craters[edit]

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 Coordinates Diameter, km
A 18°20′N 8°20′W / 18.34°N 8.33°W / 18.34; -8.33 (Eratosthenes A) 5.7
B 18°42′N 8°42′W / 18.70°N 8.70°W / 18.70; -8.70 (Eratosthenes B) 5.3
C 16°53′N 12°23′W / 16.89°N 12.39°W / 16.89; -12.39 (Eratosthenes C) 5.2
D 17°26′N 10°54′W / 17.44°N 10.90°W / 17.44; -10.90 (Eratosthenes D) 3.8
E 17°56′N 10°53′W / 17.93°N 10.89°W / 17.93; -10.89 (Eratosthenes E) 3.8
F 17°41′N 9°55′W / 17.69°N 9.91°W / 17.69; -9.91 (Eratosthenes F) 4.0
H 13°19′N 12°15′W / 13.31°N 12.25°W / 13.31; -12.25 (Eratosthenes H) 3.5
K 12°51′N 9°16′W / 12.85°N 9.26°W / 12.85; -9.26 (Eratosthenes K) 4.3
M 14°01′N 13°35′W / 14.02°N 13.59°W / 14.02; -13.59 (Eratosthenes M) 3.5
Z 13°45′N 14°06′W / 13.75°N 14.10°W / 13.75; -14.10 (Eratosthenes Z) 0.6


  1. ^ Wilhelms D. (1987). "Chapter 12. Eratosthenian System" (PDF). Geologic History of the Moon. United States Geological Survey Professional Paper 1348. pp. 249–250. Archived from the original (PDF) on 2013-05-14. 
  2. ^ Pickering, W. H. (1919). "Eratosthenes I, a study for the amateur". Popular Astronomy. 27: 579–583. Bibcode:1919PA.....27..579P. 
  3. ^ Pickering, W. H. (1924). "Eratosthenes". Popular Astronomy. 32 (6): 392–404. Bibcode:1924PA.....32..393P. 
  4. ^ "Eratosthenes". Gazetteer of Planetary Nomenclature. International Astronomical Union. Retrieved September 21, 2017. 
  5. ^ Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999), p.61.
  6. ^ Riccioli map of the Moon (1651)
  7. ^ Ewen A. Whitaker, Mapping and Naming the Moon (Cambridge University Press, 1999).
  8. ^ a b Langrenus map of the Moon (1645)
  9. ^ Hevelius map of the Moon (1647)

Further reading[edit]

External links[edit]

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