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AS14-78-10378 (H) | AS14-78-10377 (H) | AS14-78-10376 (H) | AS14-78-10375 (H)



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L.O. IV-1334



[82]



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AS15-98-13361 (H)


FIGURE 71 [above].- A very low Sun angle emphasizes detail in this south-looking oblique view of an area in western Oceanus Procellarum. The crater Seleucus is just outside the field of view to the right, and Seleucus E is in the lower left corner. The near-terminator view was exposed in a hand-held Hasselblad camera with a 250-mm lens. Low Sun illumination enhances small surface features and subtle differences in slope so that the broad, gently sloping arches associated with the mare ridges are clearly delineated. The oblique viewing angle accentuates the angularity that characterizes the path of many ridges as they are traced across the mare surface. (See, for example, fig.68.) - M.C.M.






[83] FIGURE 72 [right].-Mare ridges in Oceanus Procellarum at the northwest tip of the Aristarchus plateau (lower right) are typical of mare ridges in many other areas. Among these are small crenulate wrinkle ridges (A) superposed on broad gentle arches (B), braided or en echelon patterns, a common tendency toward parallelism within limited areas, and a tendency to be deflected by obstacles such as the arcuate ridge belt of terra near the Aristarchus plateau. Measurements by photogrammetric methods have shown that mare ridges may project as much as 250 m (at C) above the surrounding mare surface. The origin of the ridges has yet to be explained satisfactorily by any single hypothesis. Among those proposed are (1) intrusion of deep-seated, postmare dikes and laccoliths, with some extrusion; (2) compressional buckling caused by sagging of comical mare surfaces; (3) buckling at the fronts of lava flows; (4) autointrusion of molten subcrustal mare lava forming laccoliths and squeeze-ups; (5) thrust faulting; and (6) drag folding along deep-seated transcurrent faults. The diversity in morphologies and patterns of ridges suggests that several hypotheses may be required to explain all of them.-C.A.H.








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AS15-2487 (M)

FIGURE 73 [right].-Stereoscopic viewing, made possible by the overlap of Apollo mapping camera frames, does wonders for some lunar scenes. When viewed monoscopically, these photos taken at high Sun illumination in Mare Fecunditatis show bright patterns of craters and narrow mare ridges. Viewed stereoscopically, they reveal the relative depths of the craters; the sharp relief of the narrow ridges; an unsuspected broad, high swell between the parallel "ranges" of narrow ridges; and the even more surprising differences in elevation between mare surfaces in the left (west) and right parts of the photograph. The elevations of the mare surfaces probably mimic the variable depth of the buried floor of the Fecunditatis basin. The center of the basin, presumably the deepest part, is located near the left of the picture, where the mare surface is lowest. The large crater Messier G is 14 km in diameter.-D.E.W.






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AS15-2401 (M) | AS15-2399 (M)

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