Posted by David Arditti at 22:21 on 2011 Jan 13
Tony, I would say it is a wrinkle ridge of the Mare Imbrium. There is a ridge that starts south of Plato before bifocating, the western (IAU) branch ending near Mt Pico, the eastern at Piazzi Smyth.I am not sure what you mean by the "very indistinct crater south of Plato". I have sometimes imagined that south of Plato there could be a ghost crater of slightly greater size than Plato, its borders defined by the western wrinkle ridge branch, Pico, and the shape of the hills on the southern flanks of Plato, but this may be entirely my imagination and without foundation.The whole area is shown in an image I took on 2010 Nov 15, below.DavidNE Mare Imbrium