Geological Chronicle
Chaplygin lies in the highlands on the Moon’s far side, within the proposed Chaplygin-Mandel’shtam Basin. It is southeast of the walled plain Mendeleev, about midway between Schliemann to the northeast and Marconi to the southwest. Its diameter is 123.39 km.
Chaplygin is one of the largest craters of Nectarian age. It formed in ferromagnetic ejecta from the South Pole-Aitken basin. The impact appears to have demagnetized the crater interior. The crater’s iron abundance is similar to that of its surroundings.
The rim is roughly circular, though its edge is uneven. The inner wall is terraced around much of the circumference and somewhat disrupted along the southern side. The mildly eroded rim has few craters around its edge, except Chaplygin K, which intrudes into the inner wall on the southeast. Inside the walls, a level, smooth plain contrasts with the rugged terrain outside; a central peak lies near the midpoint, with a few tiny craters scattered across the surface. The crater is named for Soviet mathematician and engineer Sergey Chaplygin (1869–1942). It was identified as Crater 297 before the International Astronomical Union formally adopted its name in 1970.