Lunar 100 – Object 44
Mersenius is a large crater in the southwestern lunar highlands, distinguished by its gently domed floor formed by uplift and volcanic intrusion. This smooth interior surface is cut by numerous secondary craters, most of them originating from nearby major impacts, which disrupt the otherwise uniform dome. Mersenius is included in the Lunar 100 because it shows a domed crater floor modified by secondary impacts, illustrating how later bombardment can overprint and fragment earlier tectonic or volcanic features.