Porter is a lunar impact crater that is located in the southern part of the Moon, and lies across the northwestern rim of the huge Clavius walled-plain. Although generally circular, the form of this crater has been modified by the geometry of the surface on which it was formed. The outer rim is generally lower to the southwest, where it lies on the floor of Clavius. Likewise the interior floor is flatter near this face. In contrast the northeastern floor is rougher and more uneven in the northeastern half.
The crater is somewhat worn in appearance, in comparison with the younger and sharper-edged Rutherfurd crater to the south along the southeast rim of Clavius. There is a double central peak located just to the southwest of the mid-point. A small craterlet lies along the northwestern inner wall of the crater, but the formation is not otherwise significantly marked by smaller impacts.
This crater was formerly designated 'Clavius B' before being renamed by the IAU.
Satellite craters
By convention these features are identified on Lunar maps by placing the letter on the side of the crater mid-point that is closest to Porter crater.
The crater is one of the older formations on the lunar surface and was likely formed during the Nectarian period about 4 billion years ago.
The crater floor retains a diminished remnant of a central massif, which lies between Clavius C and N. The relative smoothness of the floor and the low size of the central peaks may indicate that the crater surface was formed some time after the original impact.
Notable nearby craters include Scheiner to the west; Blancanus to the southwest; Maginus in the northeast, and Longomontanus to the northwest.
The Maria, or seas, are the grey smooth plains on the lunar surface.
On the crater’s circular rim I saw 4 smaller craters superimposed, Rutherfurd and Porter on the east, and Clavius K and L on the opposite side.
This young crater with a diameter of 128 km and a depth of 5000 meters is a typical example of a complex crater with terraced walls, central peaks, and a relatively flat floor full of hills.
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