Geological Chronicle
Chapman lies on the far side of the Moon, just past the northwestern limb as observed from Earth. Situated northeast of Rynin and south of the expansive walled plain Poczobutt, the structure spans 76.83 kilometers in diameter across rugged lunar terrain.
Formed during the Pre-Nectarian period, Chapman has been heavily eroded by subsequent impacts that softened its profile into a worn, bowl-shaped depression. While circular along much of its perimeter, the rim is breached to the south by the satellite crater Chapman W, and an unnamed depression adjoins the southwestern crest where the wall narrows.
Small impacts pockmark the outer crest and inner wall, including a paired formation that cuts a cleft in the western rim and a slender cleft along the northwestern slope. In contrast to the rough exterior landscape, the crater floor remains relatively flat, punctuated by scattered impact pits in its southeastern quadrant.
The International Astronomical Union formally adopted the crater's name in 1970, honoring the British geophysicist and mathematician Sydney Chapman.