Geological Chronicle
Located on the northeast edge of Mare Vaporum, Manilius is a lunar impact crater measuring 38.34 kilometers in diameter. The crater features a well-defined rim with a small outer rampart, and its inner surface slopes directly down to a ring-shaped mound of scree along the base. Its interior has a higher albedo than the surroundings, appearing bright when the sun is overhead, and contains a central peak formation near the midpoint.
Infrared spectroscopy along the northern walls has identified the signature of pure crystalline plagioclase. Manilius also possesses a ray system extending for more than 300 kilometers across the lunar surface. Although prominent ray systems generally indicate a younger Copernican age, the crater is currently mapped as Eratosthenian.
Early lunar cartographers assigned several different names to the feature. Michael van Langren designated it Isabellae Reg. Hisp. on his 1645 map, and Johannes Hevelius labeled it Insula Besbicus after the island in Turkey now known as İmralı. In 1651, Giovanni Riccioli introduced the name Manilius in honor of Roman astronomer Marcus Manilius, a designation the International Astronomical Union adopted in 1935.