Mare Humorum

This image shows Mare Humorum and the western edge of Mare Nubium. Mare Humorum is a small circular mare on the lunar nearside. It is about 275 miles (~440 km) across. The mountains surrounding Mare Humorum mark the edge of an old impact basin. This basin has been flooded and filled by mare lavas. These lavas also extend past the basin rim in several places. In the upper right are several such flows which extend northwest into southern Oceanus Procellarum. Note the large fractures arcing around Mare Humorum on the right. These fractures are believed to mark a bending of the lunar surface due to the weight of Mare Humorum. Such a sinking of the mare may also explain the two large, partly flooded craters that seem to slope into Mare Humorum. (Earth-based telescopic photo from the Consolidated Lunar Atlas)

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