Geological Chronicle
Lacus Autumni, translated from Latin as the "Lake of Autumn," is a region of lunar mare positioned near the western limb of the Moon. The feature sits in the northeastern quadrant of the gap between Montes Rook and Montes Cordillera, two concentric mountain rings surrounding the Mare Orientale impact basin. Because of its location near the edge of the lunar disk, the region is difficult to observe directly from Earth.
The mare is approximately 195 kilometres long, trending from southeast to northwest and reaching a maximum width of 90 to 100 kilometres. Its irregular appearance results from lunar basalt that emerged from the surface to fill low areas between hummocky hills.
The International Astronomical Union officially approved the designation Lacus Autumni in 1970.