Geology
It was not sampled by the Apollo program, so a precise age has not been determined. However, geological 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 crater Gassendi, which was considered as a possible landing site for Apollo 17.
Read more about this topic: Mare Humorum