Mare Humorum (the "sea of moisture") is a lunar mare. The impact basin it is located in is 825 kilometers across. It was not sampled by the Apollo program, so a precise age has not been determined. However, geologic mapping indicates that it is intermediate in age between the Imbrium and Nectaris Basins, suggesting an age of about 3.9 billion years. Humorum Basin is filled with a thick layer of mare basalt, believed to exceed 3 kilometers in thickness at the center of the basin. On the north edge of Mare Humorum is the large craterGassendi, which was considered as a possible landing site for Apollo 17.
