Geological Chronicle
Ashbrook is a 157.68-kilometer-wide impact crater in the vicinity of the south pole on the far side of the Moon, placing it out of direct view from Earth. It lies within the South Pole-Aitken basin, with the walled plain Zeeman to the northwest and the plateau Mons Kocher just to the north. Its eastern face is overlain by Drygalski, a crater of similar size whose outer ramparts and ejecta cover more than half of Ashbrook's interior floor.
On the lunar geologic timescale, the formation dates to the Pre-Nectarian period. Subsequent impacts have worn and eroded the surviving outer rim, although much of the original formation remains visible. Any central peak the crater may have once possessed is buried under Drygalski's ejecta, leaving only a section of the interior floor near the southwest rim flat and marked by tiny craterlets.
The International Astronomical Union adopted the name Ashbrook in 1994 in honor of American astronomer Joseph Ashbrook (1918–1980). Before that decision, the feature was designated Drygalski Q. In lunar studies, Ashbrook is cited for his method of estimating the height of lunar domes from their shadows.