Geological Chronicle
Thomson lies within the basalt plains of Mare Ingenii on the far side of the Moon, spanning 117.25 kilometers across. The impact crater sits southwest of the merged crater Van de Graaff, with O'Day on the northwest rim of the mare and Obruchev along its southern shore. The feature commemorates British physicist and Nobel laureate Sir Joseph John Thomson.
Lava flooded the crater in the past, leaving only the outer rim intact. Gaps in the eastern and western rims leave two mountainous half-moon arcs facing each other across the relatively flat floor, while a similar lava-flooded crater remnant attaches to the southern rim.
The floor of Thomson features secondary impacts that form short, linear streaks across the surface. Along the northwest rim, observations have identified the infrared spectrum of pure crystalline plagioclase.