Mare Fecunditatis (the "Sea of Fecundity" or "Sea of Fertility") is a lunar mare which is 840 km in diameter. The Fecunditatis basin formed in the Pre-Nectarian epoch, while the basin material surrounding the mare is of the Nectarian epoch. The mare material is of the Upper Imbrian epoch and is relatively thin compared to Mare Crisium or Mare Tranquillitatis. This basin is overlapped with the Nectaris, Tranquillitatis, and Crisium basins. Fecunditatis basin meets Nectaris basin along Fecunditatis' western edge, with the area along this zone faulted by arcuated grabens. On the eastern edge of Fecunditatis is the crater Langrenus. Near the center lie the interesting craters Messier and Messier A. It was here that the first automated sample return took place via the Luna 16 probe, in September of 1970.  Sinus Successus lies along the eastern edge of the mare.