AS16-2995(M)

Figure 182

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This arcuate structure is Letronne. It straddles the boundary between southern Oceanus Procellarum and the southern highlands. From "horn to horn" it is about 115 km wide. Astronomers have long recognized Letronne as a crater and geologists also interpret it as a crater because those parts preserved have much in common with better-preserved craters. The preserved crater elements include a large segment of a raised rim, a partly preserved blanket of ejecta occupying depressions along the lower edge of the picture, and the tips of three centrally located peaks that presumably represent the top of a buried central peak complex. The largest and steepest slopes along the rim face inward and probably define the wall of Letronne. The northern one-third of the rim and wall has been almost completely buried by the mare lavas of Oceanus Procellarum. An isolated small hill (arrow) and the crudely arcuate band of mare ridges east of the hill mark the approximate position of the buried rim. The abrupt disappearance of the rim beneath Oceanus Procellarum suggests faulting, but vertical movement without faulting is also possible; this part of Procellarum may have been tilted downward or the adjacent highlands upward.    -G.W.C.