Theon Senior (crater)

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File:Dionysius crater Area Si.jpg
The crater area in a Selenochromatic format Image (Si)

Template:Infobox Lunar crater

File:Theon craters AS16-M-1392.jpg
Oblique view of Theon Senior (top) and Theon Junior (bottom) from Apollo 16

Theon Senior is a lunar impact crater that is located to the northwest of the crater Delambre, and south of D'Arrest. It forms a matching pair with Theon Junior, about two crater diameters to the south-southeast. The satellite crater Theon Senior A can be found to the north. Theon Senior is named for Theon of Smyrna, a 1st-2nd century Greek mathematician and philosopher.<ref>Template:Gpn</ref><ref name="a">Autostar Suite Astronomer Edition. CD-ROM. Meade, April 2006.</ref><ref name="b">Moore, Patrick (2001). On the Moon. Sterling Publishing Co.. Template:ISBN.</ref>

This crater is circular and bowl-shaped, with only a small floor at the center of the steeply sloping interior walls. The crater appears relatively young, as it shows little sign of wear due to impacts. The crater is about 18 kilometers in diameter, and the distance from its rim to the floor is 3470 meters.<ref name="a"/> Theon Senior is from the Eratosthenian period, which lasted from 3.2 to 1.1 billion years ago.<ref name="a"/><ref name="b"/>

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 Theon Senior.<ref>Template:Cite book</ref>

Theon
Senior
Latitude Longitude Diameter
A 0.2° S 15.4° E 5 km
B 0.2° N 14.1° E 6 km
C 1.4° S 14.5° E 6 km

References

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|CitationClass=web }} - includes a couple of craters such as Theon Senior