Page "Apollo 16" Paragraph 12

Apollo 14 had visited and sampled a ridge of material that had been ejected by the impact that created the Imbrium impact basin.

Likewise, Apollo 15 had also sampled material in the region of Imbrium, visiting the basin's edge.

There remained the possibility, because both the Apollo 14 and Apollo 15 landing sites were closely associated with the Imbrium basin, that different geologic processes were prevalent in areas of the lunar highlands far from Mare Imbrium.

Several members of the scientific community remarked that the central lunar highlands resembled regions on Earth that were created by volcanic processes and hypothesized the same might be true on the Moon.

They had hoped that scientific output from the Apollo 16 mission would confirm their suspicion.