image by Clementine viaUSGS Map-A-Planet, Flagstaff, Arizona
Just north of Poincare - a farside two or three ring basin - is Hopmann. This 88 km diameter crater is typical of large ones within the South Pole - Aitken Basin in that its floor is mostly surfaced with mare lavas. Some of the old floor and remnants of concentric rilles peek out at the bottom right, and possibly near the center where there is a small peak and more highly cratered patch of terrain. The very bright ejecta blanket of a small crater is the most conspicous feature on the floor, but another much more delicate brightening is more interesting. The tightly sinuous narrow bright marking southeast of the center looks very much like a lunar swirl. The tight bright swirl appears to extend as two parallel lines across the central area to the opposite wall. A final sight is the unnamed large crater on the south side of the floor which contains an interior ring right up against the crater wall. This is not a traditional concentric crater (CC), but seems a similar type of structure. Like most CCs this double ring crater is on a thin unit of lava, suggesting again that inner rings are somehow associated with an interaction of the impact event with layered target rock. The farside has many secrets yet to divulge.
PS - I thank Paolo Amoroso for uploading a Hopmann image to the LPOD Photo Gallery, which is where I noticed this interesting feature!
Related Links:
Clementine Atlas plates 131 & 132
Yesterday's LPOD: Lunar People
Tomorrow's LPOD: Rims Near the Limb
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