Mare Australe (the "Southern Sea") is a lunar mare located in the southeastern hemisphere of the Moon. It is 603 kilometers in diameter, overlapping the near and far sides of the Moon. Smooth, dark volcanicbasalt lines the bottom of the mare. The Australe basin was formed in the Pre-Nectarianepoch, while the mare material inside formed in the Upper Imbrian epoch.
Unlike most of the lunar maria, Mare Australe has an uneven surface that is marked by a number of crater impacts. Examples of these include the craters Jenner and Lamb, which are flooded with basalticlava much like many of the other crater features in this mare.