Geological Chronicle
Bessel lies in the southern half of Mare Serenitatis and is the largest crater to lie entirely within the mare. Menelaus lies to its north-northeast. The crater is named for German astronomer Friedrich Wilhelm Bessel (1784–1846). Johann Mädler added the name to lunar nomenclature in 1837; the International Astronomical Union officially adopted the designation in 1935.
Bessel dates to the Copernican period of the lunar geologic timescale. Its circular, bowl-shaped form has a rim with higher albedo than the floor or surrounding mare. The outer rim is not significantly worn, and the interior has no notable features apart from material slumped from the inner walls to the floor. Bessel is too small to have developed the terraces found in larger craters. A distinct darker layer lies in the upper half of the wall, roughly 500 m from the rim.
A large ray crosses the mare from north to south, passing west of Bessel. Its origin is unclear. It appears to begin at Menelaus’s rim, though its alignment suggests Tycho as a possible source. The Tycho ray ends in the central highlands, hundreds of kilometers south of Bessel, and there are no evident clusters of Tycho secondary craters along the stretch between the highlands and the bright ray’s start at Menelaus’s rim.