Geological Chronicle
Ritter lies near the southwestern margin of Mare Tranquillitatis, spanning a diameter of 29.52 kilometers across a roughly circular frame. Its slumped inner walls fall toward an irregular floor segmented by low ridges, while the parallel trenches of Rimae Ritter branch away to the northwest.
Forming a close pair with Sabine immediately to the southeast, Ritter presents an unusually shallow interior devoid of typical impact depth or radial ejecta blankets. Lunar geologist Don E. Wilhelms documented that their shared size and placement along graben led investigators to consider both formations volcanic calderas rather than impact structures before the Apollo missions.
Analyses conducted following the Apollo program resolved the origin of the pair, demonstrating that craters within mare basins experience enhanced isostatic uplift. Thinner crustal rock and elevated heat beneath the basin floor lowered the viscosity of the substrate, allowing the crater floor to rise toward equilibrium with its surrounding terrain.