Geological Chronicle
Situated on the far side of the Moon south of Comrie, Ohm measures 61.75 kilometers in diameter and is named after the German physicist Georg Simon Ohm. The satellite crater Comrie K attaches to its northeastern rim, while the larger crater Shternberg lies to the northwest and Kamerlingh Onnes to the southwest. Formed during the Copernican period, the crater retains impact melt rich in meteoritic iron.
Ohm sits at the origin of a ray system extending several hundred kilometers across the surrounding lunar terrain. The exterior surface for about 20 to 30 kilometers remains relatively free of ray material, but beyond that perimeter lies a skirt of higher albedo with streaks running northwest, east-northeast, and southwards.
The outer rim is sharply defined except at its southern end, where the edge is somewhat irregular. Within the crater, slumped material slopes down to the floor around a modest central rise. Spectral analysis of this central peak matches a gabbro mineralogy excavated from 6.4 to 9.9 km deep.
Before its formal naming by the International Astronomical Union in 1970, Ohm was designated Crater 253. In April 2026, the Artemis II lunar flyby brought the crater and its chevron-shaped bright rays into direct human view as the spacecraft approached the Moon's western hemisphere and far side regions.