Geological Chronicle
Positioned on the eastern shore of Palus Somni to the west of Mare Crisium, Proclus is a young lunar impact crater measuring 26.91 kilometers in diameter. It has a high albedo, ranking second only to Aristarchus in brightness. The rim is distinctly polygonal, forming a pentagon that does not rise far above the surrounding terrain, while the interior displays wall slumping and an uneven floor with small rises from slump blocks.
The crater has a notable ray system extending over 600 kilometers, whose bright streaks place Proclus within the Copernican System. The rays display an asymmetric pattern, with the most prominent extending to the northwest, north-northeast, and northeast, alongside an ejecta-free arc to the southwest. These features suggest the crater formed from an impact at a low angle.
Infrared observations have identified pure crystalline plagioclase on the north wall of the crater. The surrounding terrain was also considered during lunar exploration planning, when a candidate landing site roughly 100 kilometers north-northeast of Proclus was evaluated for the Apollo program before planners selected the Taurus-Littrow valley for Apollo 17.