Geological Chronicle
Mare Vaporum, Latin for the 'Sea of Vapors', is a circular lunar mare basin situated in the central near side of the Moon. Centered at 13.3° N and 3.6° E, the basin spans 245 kilometers in diameter and covers an area of roughly 55,000 square kilometers. The depression formed within the larger Procellarum basin, wedged between the southwestern margin of Mare Serenitatis and the southeastern rim of Mare Imbrium. Eruptions of low-titanium basaltic lava flooded the basin floor during the Early Imbrian epoch, with subsequent volcanic resurfacing extending into the Eratosthenian period.
Rugged lunar mountain ranges define the perimeter of Mare Vaporum. The high peaks of Montes Apenninus border the mare to the northwest, while Montes Haemus lines its northeastern boundary. Across these margins lie several volcanic fissures and grabens. Along the southern perimeter sits Rima Hyginus, a linear rille system 220 kilometers in length split by the 11-kilometer-wide volcanic crater Hyginus. Unlike standard impact structures, Hyginus is a volcanic caldera lacking an elevated rim. At the northern perimeter near Sinus Fidei, the mare transitions toward Rimae Yangel' and the small circular crater Yangel'.
Italian astronomer Giovanni Battista Riccioli assigned the name Mare Vaporum in 1651 in his lunar map, a designation the International Astronomical Union formally adopted in 1935. Modern orbital missions provided detailed imaging of the basin and its surrounding faults. During lunar orbital operations in 1971 and 1972, crew members on Apollo 15 and Apollo 17 captured high-resolution panoramic and mapping camera photographs of the basin floor, documenting its rille systems and dark mantling deposits.