The South Cluster, a crater cluster located to the south of the Apollo 15 site near Mons Hadley Delta, is believed to have formed as a result of a secondary impact, or the impact of ejecta/debris from a larger impact elsewhere on the Moon, probably the crater Autolycus about northwest of the cluster's location. This meant that the Apollo 15 astronauts were able to sample material from other parts of the lunar surface without traversing a great distance. The feature also allowed the astronauts to sample material that was originally located deep within the Moon. The south rim of Dune crater within the cluster was visited by the astronauts.