The upper half of the map portrays the geology of the earth-facing or near side, and the lower half shows terrain that was unknown before spacecraft photography. The geology of a small area near the south pole that was in shadow during the Orbiter missions can be partly inferred from the nature of adjacent units.
Line geometry is topologically clean.
Geology mapped 1973-77. Near side mapped by D.E. Wilhelms and H.G. Wilshire, far side by K.A. Howard and D.E. Wilhelms. Prepared on behalf of National Aeronautics and Space Administration under Contract No. Information has been obtained from sources believed to be reliable, but its accuracy and completeness and the opinions based thereon, are not guaranteed. As every effort is made to provide accurate information in this database, USGS would appreciate it if users could call to our attention any errors that may occur by communicating with the contact person.