AS17-2103(M)       &       AS17-2102(M)

Figure 63

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This stereoscopic view shows southwestern Mare Serenitatis "lapping against" its shore of ancient highlands or terrae. The highlands near the Sulpicius Gallus rilles in the lower part of the picture are unusually dark-- darker even than the mare. M. H. Carr (1966)
suggested from telescopic study that the darkness of the highlands is caused by a thin mantle of dark material, perhaps consisting of volcanic ash. The numerous small bright spots are knobs of highland material. They may have once been covered by the dark mantle but, if so, have since shed it. As elsewhere around the outer part of Mare Serenitatis, the rilles and the dark mantle in this area were originally thought to be younger than the lighter mare to the north. Apollo 17 photographs such as these have changed that concept. Now, the lighter mare is interpreted as embaying the faulted dark materials, just as in the Plinius rilles area (figs. 58 and 59). Isolated islands of dark mantled highlands that escaped inundation are shown by the arrow.   K.A.H.