The steep-walled but shallow D-shaped depression near the center of the photograph is apparently a unique feature. It is located in a patch of mare on the foothills of the Montes Haemus, west of Mare Serenitatis. Measured along its straight side, the depression is about 3 km wide. It is situated atop a very gentle circular dome that appears to be somewhat smoother than the surrounding mare surface. As is more clearly shown in the accompanying stereogram (Figure 233), the many bulbous structures on the floor give it a blisterlike appearance. The depression is believed to be volcanic, probably a caldera (El-Baz, 1973b). Figure 234 explains the probable sequence of events leading to the formation of this unusual structure. -F.E.-B.
This web page was created by Francis Ridge
for The Lunascan Project
Section Directory 23