Geological Chronicle
Spanning 319.46 kilometers in diameter, Planck is a massive impact basin situated in the southern hemisphere on the far side of the Moon. Located within the broader South Pole–Aitken basin, the crater lies west of the walled plain Poincaré and adjoins several nearby features, including Prandtl across its southeastern rim, Hildegard to the northeast, and Fechner to the west. The formation is named for German physicist and Nobel laureate Max Planck.
According to a 2012 study, Planck formed roughly 4.09 billion years ago, partially resurfacing the sector of the South Pole-Aitken basin that it impacted. The structure is classified as a peak ring basin, characterized by an interior ring of peaks without a central peak. Later smaller impacts have eroded its outer rim into a rugged ring of peaks and ridges notched by small craters, while its western rim is overlain by Vallis Planck, a 503-kilometer valley radial to Schrödinger to the south.
A multi-crater formation occupies the northern interior floor, comprising Planck W, Planck Y, Planck Z, Planck B, and Planck A. The floor of Planck Y has been almost completely flooded by lava, leaving only a shallow perimeter, while Planck Z is also flooded and Planck B contains a concentric crater and several floor clefts. Smooth plains line an arc along the northern inner wall, contrasting with the more irregular southern floor, which is marked by small craters and ghost-crater remnants.